Steven Chu

Zierler:

OK, this is David Zierler, Oral Historian for the American Institute of Physics. It is May 18, 2021. It is my great honor to be here with Professor Steven Chu. Steve, it's great to see you. Thank you for joining me today.

Chu:

Oh, my pleasure.

Zierler:

To start, would you please tell me your title and institutional affiliation?

Chu:

I'm a Professor of Physics, and I'm also a Professor of Molecular and Cellular Physiology in the Medical School at Stanford University.

Zierler:

And is that a joint appointment in terms of teaching and department responsibilities? Is it essentially 50/50?

Chu:

Yes. I have a root home department, physics, but it's 50/50. Which means I go to both faculty meetings, participate in the votes, things of that nature. Big difference now. Molecular and Cellular Physiology is a small department with only 12 people. When I joined physics, way back in 1987, there were about 21 or 22. But now, it's effectively merged with applied physics, and both have grown, and now it's 40-ish. I actually enjoy a department of 12 much better.

Zierler:

Just for a snapshot in time circa May 2021, what are you involved with, both scientifically, politically, and administratively? What do you have going on these days?

Chu:

So scientifically, I am in several fields. That follows a pattern of mine, where I usually either go into another field or branch out into another field. I get restless, but not only that, once something becomes more visible and known in the scientific world, lots of smart people rush in and try to do something, which is how progress is made. But as soon as that happens, then I look around and say, "Well, why should I be competing with 100 people smarter than me? [laugh] I'd rather start something new, where there is no competition." And so, that has been true since immediately after my graduate student days.

And so, right now, to specifically answer your question, my center of gravity had moved from physics to biology in the late 1990s due to, first, optical tweezers of molecules, but then other so-called single-molecule methods, like, for instance, resonance energy transfer, and we were the first group to actually get it to work on a surface that made it practical. And so, all these methods that were being invented by my group or other groups became a real new window on biology. But there were certain experiments I could not do based on the current optical probes. It's a marriage of optics, microscopy, and what you can do with it. And so, when I stepped down from being Secretary of Energy, I said, "Well, what couldn't you do with fluorescent dye molecules, fluorescent proteins, and also quantum dots that, if you had a better probe, you could do some new things?"

So I thought there were new light emitting nanoparticles emerging, and I'd team up with materials scientists, they would give me the particles, they could make the particles that I knew about biology. And so, that was the strategy. But when these materials people started giving me the particles, they weren't as good as advertised, in part because they were all clustering together. You have to make them water soluble, and in doing so, it was bad. And so, in desperation, we said, "Well, let's try to make our own particles." So after a year or two, we now make the best particles of this type, a new class of particles. And that has enabled us to do things. These particles don't photo bleach, their fluorescence is very steady.

We started doing biology experiments, and the first biology experiment was a rehash of an experiment we did in 2004 or 2005 with quantum dots, but again, the quantum dots were blinking, and eventually they would photo bleach. So that's one thing. But then, once we realized we had these particles and could make them any size we want and things like that, the explosion of new applications started to just grow. It was sort of like laser cooling and trapping. When I was working on laser cooling, I said to a director at Bell Labs, "We can cool atoms, and we can trap them." And he says, "That's great," noting my enthusiasm. "What are you going to do with them?" And I said at the time, "I don't know, but I think it's really neat."

Now, actually, I knew of only one application, and that is, if you have really cold atoms, you can throw them up, and they would go up and turn around due to gravity. And in this free fall, you would have the ability to make a very precise measurement, and notably, a microwave measurement that would lead to a better clock. So that was the one thing I knew about. And so, as soon as I got to Stanford, I did exactly that. Threw them up and showed that, "Yes, indeed, you can make a better clock." And within seven years of that first demonstration, the Bureau of Standards around the world used that method as the time standard. So it's a very fast application, but it's just so much better.

Zierler:

If I can interject on Bell Labs for a second, I always thought that Bell Labs was the high temple of basic science, where you would never have to defend whether or not it had applications.

Chu:

You're right in that respect, but he was just wondering. [laugh] First big experiment I did at Bell Labs had to do with taking an atom consisting of an electron and its anti-particle and making a precision measurement of this. Now, this is not in the mainstay of telephone communications. It was testing quantum electrodynamics, and it was a minor deal in the sense that there were many, many attempts to try this in the decades before, and it never worked. And so, my brief moment of fame was I got something to work that other people had tried that never worked. But it didn't have any real impact because it was so esoteric. Atom cooling was very different because it was a method, and as soon as we got the laser cooling to work, the optical molasses, and most notably, this thing called a magneto-optic trap that is now a college demonstration experiment, it became so easy for everybody that that really made things explode.

But once you did the fountain clock, then we made what are called atom interferometers using optics to quantum mechanically put the atom in one trajectory and another trajectory, but it's in both at the same time. And then, looking at the interference of the atomic waves, and this is in 1991 or so, within a year, it became very precise, with a measurement uncertainty on one part in 108. It's now the best way of measuring gravitational acceleration and tests of General Relativity. People are now thinking of making the new generation of gravity wave detectors. Again, these are "applications in basic science". But there were many more applications, again, in science. The ability to hold onto atoms. While we were pursuing atoms, we had this optical glue, optical molasses, and then this tiny, little focus beam. And we were trying to get that to work.

The idea of trapping a particle, or even an atom, in a tiny, focused laser beam was proposed years ago. In fact, by 1970 and '71, Art Ashkin showed you can hold onto particles in water, and the water kept them cold. He also showed you can levitate particles. And in '78, he proposed that you could focus very tightly and hold onto atoms. So by, ironically, 1970 and '71, he never did the experiment to focus tightly onto a micron-sized particle in water and hold onto them with what we dubbed the “optical tweezer.” It's only when we're doing this really exotic stuff with atoms in 1985, and using optical molasses cool them and keep them cold after they were optically trapped that it was realized the same thing could be done with particles cooled in water. This was 15 years after all the ingredients for optical tweezers were there. We said, "Yeah, particles trapped in water is the poor person’s version of optical trapping with a single focused laser bean cooled in optical molasses." So that was how the optical tweezer of small particles was born. It eventually led to Ashkin's Nobel Prize because he found, a year after that, you can hold onto bacteria.

When I got to Stanford, I said, "Well, you can hold onto bacteria and atoms. Why not hold onto biomolecules in water at room temperature by gluing little handles, little polystyrene spheres, to the molecule?" And so, I started that in '89. By 1990, it worked. I got a graduate student in the medical school, Steve Kron, to teach me how to glue these little polystyrene spheres to DNA. So he had to teach me some basic biochemistry. And so, that, again, took fire. And it caught on, and Ashkin happily got a Nobel Prize in 2018 for that work. Because the ability to do precision measurements, and measuring forces, and distances, and displacements at a molecular level was a big deal. Again, these are applications, but they're applications in research.

Timekeeping still is a big deal. The global positioning satellite system (GPS) is based on atomic clocks. And its spatial accuracy is now bordering on a centimeter if you really stretch the limits of GPS. It is certainly less than a meter, and if your ability to locate where you are is less than a meter, you say, "Isn't that good enough?" And not only, "Isn't that good enough?" but you don't need the clocks based on fountains and cold technology that were emerging. Cold atom technology allowed clocks with 14 and 15 decimal place accuracy to precision of 19 to 20 decimal places, which sounds ridiculous. To tell you how ridiculous it is, suppose you started one of these clocks when the universe was born 14 billion years ago. And you said, "OK, what's the uncertainty in time after 14 billion years?" It's about one second.

So a logical question is, isn't this overkill? So, a couple years ago, I asked a friend of mine, Brad Parkinson, who was one of the people who while he was working in the Air Force, actually established the GPS satellite system. I said, "Well, since cold atom technology, there have been great advances in technology, cold atom clocks. We're going to get a couple more decimal places. Do you really need it?" And he said, "Yes, but not for the reason you think. And the reason you think is, what happens is, there's an atomic clock up there, and the best clocks are still on earth, so you beam up and beam down, and you constantly do this correction. But if you had a better clock, a better flywheel in the satellite, you could actually make systems much more resistant to interference, jamming, and malfeasance. So yes, we can use a couple more decimal places." With a better clock, you don't have to phone home quite as often.

And so, "OK." It's sort of like, in computing, there were such rapid advances that all the sudden, the laptop computer was now the supercomputer of 30 years ago, and now the iPhone computer is the supercomputer of 40 years ago. It's ridiculous. And there was always a fear, "Isn't this good enough?" And for most people who don't do heavy computing with their laptops, who do only do word processing, mail, PowerPoints, they don't need that compute power. But machine learning and artificial intelligence came along, along with an insatiable hunger for more compute power. If computing speed improved by several orders of magnitude, it can be used to massage bigger data sets better. So, it's a funny business, what you think your computers are getting to be “good enough,” then, all the sudden, you realize you've found a new capability. And all of a sudden, things you've never dreamed of doing, you can now do, and it opens up a new computer application.

So, thinking of how to improve some technology that's rapidly advancing was something I had wired into me when I was a graduate student. In my second year, I started working with an advisor, and then in 1972, the tunable dye laser was invented. The first laser was demonstrated in 1966. I started as a graduate in 1970. And I said, "Wow, a tunable laser. You can do things you couldn't do before." My advisor was an atomic physicist. Dye lasers can be tuned to spectral lines, so I said to my advisor, "I want to work with lasers." He said, "OK, but I don't know anything about lasers." I said, "Don't worry, I'll learn about lasers. Let's look for something to do with them." And what happened was, I got really good at making lasers. In fact, when we finally did land on a really nice project that excited both of us. The experiment was to use a dye lasers to excite an atom in order to test a theory that unified weak and electromagnetic interactions. This is the so-called Weinberg-Salam-Glashow model.

So that was a big event. Just as big an event as when Maxwell unified electricity and magnetism. Now, you have electricity, magnetism, and weak nuclear decay forces all in one theory. And so, my thesis was to test that in a tabletop experiment, not a high energy accelerator. And so, it was a great application, and I got good at making lasers. And the experiment was hard and we weren't making progress as fast as we had hoped. I finally made a deal with my advisor, "Look, I've been a graduate student now for a while. Why don't you give me a PhD, and I'll hang around and finish the experiment as a post-doc" He said, "Sure." [laugh] It also meant he wouldn't have to pay me anymore. I had been on an NSF pre-doctoral fellowship, but the fellowship was only four years, and I was in my sixth year as a graduate student. For years five and six, he had to pay me.

But then, I got an NSF post-doctoral fellowship, so I became free to him again.

Strangely, for whatever reasons, the physics department at Berkeley asked me to apply for a job. "Well, I'm not sure I want to stay at Berkeley. I've been here, now, seven and a half years." I was told, "Just apply, you can always turn us down." So I applied, I gave a physics colloquium talk, and they gave me the job. They said, "Great. Here's your setup money. You can do whatever you want to do. But you spent all your time doing this one experiment, we'll allow you to go somewhere else, broaden yourself. The job is yours, you start your group now, or take a leave of absence. You can do what you want." So I said, "Great, I'll take the money." I spent it on equipment to do a better version of my thesis and postdoc experiment. My scientific outlook was very narrow. But I also said, "I'll go somewhere," so I went to Bell Labs on a leave of absence from Berkeley. I was officially in their catalogue and planned to come back in two years.

But Bell Labs was like hog heaven, and being at Bell Labs broadened me tremendously. I didn't know about this whole wide world of physics. And then, I told Bell Labs I was going back. I promised them a year and a half afterwards. First I said, "I only want a post-doctoral position because I'm going back." They said, "No, no, we think you should take a permanent position. You'll have more freedom. You can do what you want." The management at Bell knew what they wanted. [laugh] They wanted to see if they could hook me. And then, after a year and a half, I told them I was going back. And they said, "Oh, you're doing so well here. Why do you want to do that?" My colleagues at Berkeley said, "Well, we are happy you are returning as you promised." And others said, "You're doing so well there. Why do you want to come back? Funding's hard. Don't come back." Anyway, I said, "No, I promised I was coming back," and then couldn't sleep for the next three days.

So I said, "My stomach is telling me something," I stayed at Bell Labs for nine years. But during that whole time, I was always looking at new areas, inventing new things, or improving on earlier things . My ability to make lasers was also getting better and better. The laser I designed when I was a graduate student worked so well that the department made four of them so other faculty members could use them. Because you just couldn't buy as good a laser from any company. It was a real workhorse. And so, maybe they hired me because they thought I could keep them in lasers. [laugh] I don't know.

I used my start-up money to buy lasers to construct a better laser system for an improved version of my thesis project. The laser system I and a beginning graduate student, Persis Drell, constructed in the final months of my postdoctoral years was used in her Ph.D. thesis. She is now the provost at Stanford.

The science I did at Bell Labs: positronium, laser cooling and trapping, and some condensed matter experiments such as exciton mobility as a test of Anderson Localization was very different than what I did at Berkeley. A bunch of things in very different fields.

When I came to Stanford, things were really working well and we were developing new methods of laser cooling and trapping. I made a mistake in my first optical molasses experiment. The temperatures were a lot colder than predicted by the theory that described an atom as one ground state and one excited state. Other groups repeated our mistake, but another post-doc in Bill Phillips's group said, "Maybe we should repeat the measurement.” After the lower temperatures were confirmed by Claude-Cohen-Tannoudji’s group, my group and Carl Weiman’s group, the race was on to understand the cooling mechanism. The real theory of laser cooling was developed by Claude Cohen-Tannoudji and Dalibard, and independently by me in a few months.

In the first eight years at Stanford, we demonstrated the atomic fountain and atomic fountain clock, the new theory of laser cooling, atom interferometry and the first optical tweezer manipulation of biological molecules happened. Everything was exploding, and these methods were opening up new fields.

By the year 2000, I got waylaid in the sense that I was an interested citizen, not in scientific interests, I was saying, "All this stuff about climate change, how real is it? Do we really know? The weather's really noisy." Like any typical physicist, you go in with this attitude. So I started looking into it and just reading papers. And I decided, "Yeah, there might be something there." And after a couple more years, I said, "Yeah." So I started talking about, "Well, we don't really know it's for sure happening, but there are some risks here."

And I remember, this is in the early 2000s, another Nobel Laureate, Richard Smalley, calls me up and says, "Steve, I'm so glad you're interested in this because I've been talking about climate change in the last two years. And to have another voice like yours is great." And then, in 2004, Lawrence Berkeley Lab, which was the national laboratory just up the hill from Berkeley, was looking for a new director. The director of SLAC, Burt Richter, said, "You'd be perfect for the job. I'm going to recommend you." I said, "Don't bother. I'm not interested. I don't want to be a bureaucrat." The people at Berkeley were also trying to get me interested. I said, "Don't bother." And finally, the then-director of Berkeley Lab, who was my former boss at Bell Labs when I did the laser cooling and trapping, said, "Well, look, if there's less than a 5% chance you're interested in the job, don't bother. We don't want to waste your or our time. If there's more than a 5% chance, why don't you come take a look around and go for an interview?"

So I said to myself, "Wow. Here I am talking about climate change for the last couple years. Here's a Department of Energy National Lab that has brilliant scientists." By brilliant scientists, I mean the following. They had, in their history, a dozen Nobel Laureates, now 15 Nobel Laureates, as employees of Lawrence Berkeley National Lab (LBNL). Even more impressive, maybe three-dozen young scientists, graduate students, post-docs, starting career people, were trained as at Berkeley Lab, including me. When I was a graduate student and post-doc, I was also a member of Berkeley Lab. Tom Cech, Nobel Laureate in chemistry, was also a Berkeley Lab employee. And so, I said, "If I can harness some of that intellectual horsepower, I could do more about energy and climate change than I could just talking about it." So I said, "OK. I'll show up for an interview." I did and they offered me the job. When I decided to interview, I was prepared to take the job. Unlike other professors, I was not interested in getting an offer to better my position at Stanford.

I took the job and immediately started thinking how to get more researchers interested in climate change and carbon-free energy and to harness the intellectual might of this national lab. As director of a national lab, one has more authority than a university president. Great scientists don’t listen to bureaucrats. The way to have influence is to get them excited about something." Many of the Lab scientists were also professors on campus. Some of my colleagues in physics and chemistry. One of the professors told me, "Steve, I don't know much about energy and climate." And I said, "Well, neither do I. Let's teach ourselves." [laugh] And so, a core of five or six people, started to meet and brainstorm. Then, we started having these little informal so-called teach-ins, half-day retreats, these sorts of things. I would give talks to describe what was known about climate change, describing the challenge, "Science could really help solve some of the problems. We don't have all of the technologies we need."

Apparently, these early efforts had an effect on a number of scientists. When I returned to Stanford after my time as Secretary of Energy, I started to collaborate with Prof. Yi Cui, who is in the Materials Science and Engineering department at Stanford. He was a post-doc in Paul Alivisatos's group at Berkeley when I was director of LBNL. He said, "I'd just gotten offered a job at Stanford to use nanotechnology," and his plan was to use nanotechnology in electronics. And he said, "And then, I heard you talk. And I said, 'Maybe I should use nanotechnology to help solve the energy problem, like make a better battery.'" Now, he's one of the big gurus in nanotechnology-based batteries. And then, he went to Stanford and said, "Well, look, I don't know anything about batteries, so I might not be able to get funding." He started supporting his battery research with his startup money, but soon received support from a Stanford energy institute who believed in him despite the lack of any track record, saying "We'll help you, too." And after a year or two, he started getting really nice ideas, and the rest is history.

I was also able to interest another young scientist, Jay Keasling, who was doing molecular biology manipulation of microbes to teach the microbes how to grow an anti-malarial drug. The anti-malarial drug is called Artemisinin, extracted from a plant in Southeast Asia. And so, he said, "If I can teach microbes how to grow this, it would be great because it could stabilize the supply." He convinced the Gates Foundation to fund him to do this. When I joined the lab, he had gotten the Gates funding, and it looked like it was going to work. So I said, "Jay, what are you going to do next?" And he said, "I'll think about some other disease." And I said, "Why don't you think about using this technology to make biofuels.” He liked the idea. I also said, “Well, look, I know this other guy at Stanford named Chris Somerville who's in the Carnegie Institute.”

Although I was on the faculty at both Stanford and Berkeley, as Lab director, I recruited Chris Somerville away from Stanford to join Jay Keasling at Berkeley and Berkeley Lab. The two of them became the heart of a new biofuels program. BP (formerly British Petroleum) found out we were getting interested in biofuels, and at the last minute, they invited us to join five other institutions to bid on this half-billion-dollar 10-year contract for a new biofuels research institute. We were the dark horse because we had not done anything in biofuels, but then, they heard through the grapevine that Berkeley Lab was trying to put together something. We didn't even know BP was considering funding a new institute. We started on this path without knowledge of funding opportunities, by the way. We were responding to the scientific challenge and the need to do something before money started really flowing, which is a good place to be. So anyway, we were awarded the half-billion-dollar grant.

During my time as director lots of things were beginning to happen: really superb scientists getting excited about doing something about climate change, and things were beginning to move. This was maybe a decade before it was to become fashionable. I was planning to step down at LBNL after five or six years and go back to the lab having done my tour of public duty. And then, in November of 2008, Obama's people asked me to meet with the President-elect to talk about a very important job. And I said, "Well, I'm not so sure I want a job in DC. I'm happy with what I'm doing, and I want to go back to research. But how important is it?" And he said, "Secretary of Energy." So I said, "OK, for that, I'll fly to Chicago." If it was for a deputy secretary or undersecretary position, I would've said “no” for sure.

Zierler:

What would you have seen as a lateral move from lab director? Deputy director?

Chu:

I wasn't really thinking of it that way because a lab director is not a federal employee.

Zierler:

More in terms of stature and responsibility.

Chu:

First two years I was lab director, word was getting out that I was a good bureaucrat. And so, I started getting nibbles from some of the best research universities in the country to be a candidate for the president of the university. That would have been a move up since they were among the top six research universities,. And I said, "No, because I just got here. I've only been here two years." It would've been completely disloyal for me to jump ship. That would've been a move up. I don't know what a lateral move in terms of stature would be, but it didn't matter because I don't think like that anyway. Actually, the way I really thought was, the highest position you could be at a university was to be a professor. [laugh] It's downhill after that. Any higher position should be done as “public service.” I was chair twice, but it was only as a public service, not because I wanted to be a dean. And because I love doing research, I had reached my pinnacle early in life. [laugh]

Zierler:

Politically, administratively, in terms of advocacy, what are you doing right now?

Chu:

I advise companies. I'm on the board of directors of companies that are trying to do something about climate change. One, for example, is a carbon capture company. They've developed a better or cheaper method of capturing carbon from point sources to manpower. Ultimately, from the air because that's going to be needed. I'm at another company that does biomanipulation of microbial genomes. It is what Jay Keasling was doing when I was director of LBNL, but this company was using robotics, machine learning, and biology to get alternate supplies of materials, starting with high value materials such as thin films, plastics, things like that. Ultimately, the target will include transportation fuel again, but it's hard to compete with oil at even $100 a barrel still. I am on the board of a battery company as well.

I'm typically the only scientist on the board of directors at those companies, and many of these companies ask for technical advice. I feel good about that because then, I get to help on the technology side as well. I am also on scientific boards of Applied Materials. Royal Dutch Shell, and Siemens before they dissolved that advisory board. Royal Dutch Shell, for example, is very serious about trying to make a transition to clean energy. While the path is unclear, they know that in 50 years, they can't be in the fossil fuel business.

Zierler:

Do they have a basic science lab like BP or Exxon?

Chu:

They have science labs, both in the Netherlands and in Houston. They've got some pretty serious scientists and engineers there. For example, several years ago, I said, "Look, I can see a time where electricity's going to be $.015 per kilowatt hour in the best places. And there are going to be times when there's an over-abundance of electricity from wind and solar. At $.015 per kilowatt hour, the energy cost to split water for electrolysis will be half the cost of delivered hydrogen “at the gate” today made from steam methane reforming. The low cost is going to open up the possibility of electrochemistry. I was saying to them, "You guys have to do more electrochemistry research."

And they took me pretty seriously and they actually put me in front of the CEO and the board to talk to them. Investing $100 million a year is nothing for a big oil company. But in terms of research in electrochemistry, it's a pretty big deal. Research directions should always anticipate the future. As another example, I do research in batteries, but don't work on how to make a better nickel-manganese-cobalt battery. If light-duty EVs are going to be 80% of the market by 2035 - 2040, the cost of cobalt would become prohibitive. Why should I do research on improving cobalt batteries. I do research on what the world's going to need ten or more years from today.

Occasionally, the Energy Commission in California would ask me for advice, and other countries would ask for advice. I am Chair of the external review of energy programs of the Humboldt Association in Germany for 7 years. The federal government has not asked me for advice during the last four years. [laugh] But in the new administration, a couple of the people who were my direct reports are now in the Biden Administration.

And there are people like that there, which is good. I'm also longtime friends with Eric Lander, who's head of OSTP and the President’s Science Advisor. I've been friends for over a decade with Frances Arnold, who is the Chair of PCAST. I spoke with Eric Lander a few times about science policy, climate change, but also other things, like the new concerns about of China, which has now leaked over into paranoia of Chinese-American scientists, many who have become naturalized citizens, and potentially crazy policies about denying visas for graduate students or post-docs from China. The Trump administration put a hold on granting graduate student visas, Biden reversed that policy, but there's still a lot of paranoia in Congress. And some zealous people in the FBI think these graduate students are spies. Perhaps a few could be spies, but I would be shocked if more than a few dozen were “spies” out of the several hundred-thousand students. At Stanford, Berkeley and many of the best research universities there is no classified research, and most of it gets published in the open literature. But what we want to do is bring great foreign graduate students here, get their PhDs here, and keep them in the U.S.

Zierler:

In this paranoia, do you see an ongoing legacy of Wen Ho Lee? Is that part of it institutionally at places like the FBI?

Chu:

Well, that is part of it, but it's gotten worse because the Chinese government is really helping companies spy on US companies. There's no debate about stuff like that. I have also heard that they have put some pressure on some graduate students to find out what is happening in laboratories in the United States, even if it's basic research. Just to get a head-start glimpse, so they can rise up in science a little bit faster than normal. There may be a little bit of that going on, too, but I don't know how widespread that is. And then, there's more of what I would call a growing confrontation. China has become very aggressive is exerting military influence in the South China Sea and other areas. There is also a concern about the rising competition, of a giant economy waking up and becoming very competitive. And when that happens, typically, the United States reacts initially in a not-so-good way. They try to put up trade barriers. When the Germans and Japanese started making better cars, we put up big tariffs. "You can only sell your cars if you have a factory here." Remember that?

And when the Japanese semiconductor industry was overtaking the US semiconductor industry, they were trying–but the US companies formed the SEMATECH, a non-profit R&D consortium to develop advance chip manufacturing technology. That's the proper response. The improper response is to put up trade barriers. I was talking to Norm Augustine a couple weeks ago, and he said, "Our K-12 education system is not good. Is that China's fault? We're underinvested in STEM education, science, mathematics. Is that China's fault?" I'm trying to help the Biden Administration and some members of Congress who are looking out for the best interests of this country to realize the proper way to respond to competition is of us to get better. If we turn off immigrant graduate students, we're going to lose a lot. A major reason why American science is so good is because we attracted all these people who were gifts from Nazi Germany, Fascist Italy, the Communist Revolution, the Cultural Revolution. All of these were gifts, but we can't expect these gifts to continue.

Zierler:

In terms of professorial duties, do you have an active group right now? Do you have graduate students? Are you teaching undergraduate classes? All of the above?

Chu:

Right now, I don't have graduate students. I have post-docs, an active but small group. And then, we leverage by collaborating with others. I'm teaching a class, Physics of Energy and Climate Change. It's suitable for upper-division undergraduates and graduate students, but the ones who appreciate it the most are graduate students in science or engineering, who want to understand the basic ideas of what we know about climate change. I collaborate with Yi Cui on batteries and electrochemistry, and Jen Dionne in Materials Science, Bianxiao Cui in Chemistry and Tom Südhof in Molecular and Cellular Physiology. I have a core group making rare earth doped luminescent nanoparticles of biology research. We have developed very bright particles and want to use them to do experiments that were not possible without the new particles. One of my postdocs students is interested in neurobiology and Alzheimer's disease in particular. We collaborate with Tom Südhof, who's in the same department as me, and who got a Nobel Prize in, I think, 2013 for identifying a number of the molecules that are used in vesicles fusion that releases neurotransmitters in neuro-communication. The experiments post-docs interested in Alzheimer's disease are aimed at trying to find out what is going at the basic science level.

Zierler:

In your teaching on the physics of climate change, have you had a chance to look at Lawrence Krauss's book yet?

Chu:

No.

Zierler:

He has a whole book on that very topic.

Chu:

There's a big book by professors at MIT, Jaffe and Taylor on the Physics of Energy.

Zierler:

More on the policy side?

Chu:

No, it's fundamentally a physics book that introduces a lot of the basic concepts in energy. In my course on climate and energy, while I teach the fundamental ideas, I also include new information that we learned in the past three to five years. You can explain a lot of the material at a very fundamental level. It's not mysterious, where a lot of this stuff comes from. The course is a springboard for those who really want to understand the fundamentals, rather than say, "Some expert with a big computer program told us this."

Zierler:

Of course, there are lots of cranks out there, but what about mavericks within the scientific community, physicists, people like Will Happer? How do you deal with that, both scientifically and politically?

Chu:

Will Happer's an interesting case. There's also Steve Koonin. And I gave a talk in the 2000s at Princeton, and I talked with Will Happer. Will Happer was a very, very good scientist in my field, atomic physics. And so, we talked. And as we talked, first, he was very upset about claims such as life on Earth will end and other exaggerations. I said, "No, no, I agree with you. Life's not going to end. The temperature of the globe can go up four degrees, but life is pretty robust. Societal order could break down, but life isn't going to end. And even polar bears had survived in a two-degree warmer world. But it's possible that, for example, we had a period in the Depression years where the Great Plains became a desert. And you could go into a situation with a little bit changed where it could flip back into the same, but over a longer period of time." And he said, "Oh, very possible. I don't doubt that for a minute. But we're still going to be able to grow food in other places."

So Will doesn't see a problem, so I said, "But these disruptions, changes in weather in places mean that a lot of people could be displaced, many people could die. It could be 5%, could be 10%, if things were really going bad." And he said, "Yeah." And then, I began to think, "OK, we're not going to disagree on the range of possible climate outcomes." I gave my talk, he listened attentively. He came up after me smiling and said, "I don't disagree with anything you said." The reason there was no disagreement was because I said in my talk, "This is what we know. This is what we don't know. These are the risks. These are the possible downsides." Also, Steve Koonin doesn't get upset when I give my climate talks. They get upset when the uncertainties of predictions to climate change are underestimated. Koonin's major schtick is that he thinks the uncertainties in IPCC are under-exaggerated. I disagree on this point, but I also think he is missing the point, that there are long-tail risks to extreme events in a changing climate. It is also very hard for predicting with any accuracy far into the future such as 30, 50, 100, 200 years. I view spending on climate mitigation as a prudent management of risk.

So when I talked to Koonin about that, we may disagree about how much to spend on risk management. When he emphasizes the uncertainties of climate predictions, I think he gets misused by the other people. And he does this because he actually likes being a skeptical curmudgeon. Both Will Happer and Steve Koonin are members of JASON, from the members I know, there seems to be a culture of skepticism. Skepticism is at the heart of science, but in something as politically charged as climate change or vaccines, scientific skepticism could be easily misinterpreted as disbelief.

Zierler:

There's also a preponderance of data where skepticism no longer serves a good purpose.

Chu:

Well, in terms of climate change, I'll give you a detailed anecdote. So Happer was worried if they were really analyzing data correctly. And he's a spectroscopist. So as you may know, carbon dioxide is saturated absorption, meaning at the center of the molecular lines, it's way over-saturated, and additional carbon dioxide mainly adds to the width of the absorption band. So his contention was, "Are they handling the line-broadening in the wings properly?" It's a very specific scientific question, and he suggested that the effect was not handled properly. He tried to get a paper published in Physical Review Letters about his concern. The paper was reviewed up, down, sideways, and finally, the editors said, "No, the reviewers find objection to his calling into question." But then, another friend of mine, who was at Princeton, Bill Brinkman, who was the Director of the Office of Science, said, "Well, look, Happer's a smart guy." There's a guy at Lawrence Berkeley Lab, a climate scientist named Bill Collins.

And he said to Will, "Why don't you get together with Happer and just talk about it? Are you handling the wings of the distribution correctly?" So Collins sends a post-doc to meet with Happer. They talk about it for a couple days, and he tells Collins, “If you assume the assumptions that Happer's assuming, that's fine, you get his result. But his assumptions are not quite right." That happened a decade ago. I was talking to Bill Collins a month ago, and I said, "Well, what more do you know about the wings?" And he said, "Oh, you should see this. We really nailed it this time through better measurements. In physics, we test theoretical predictions with better measurements, and more work are showing the modeling of the absorption lines is being handled correctly. Happer posted a blog because he couldn't get into Physical Review Letters but he has remained silent on what now seems to be a settled matter on the details of how to treat line broadening. I think it is partly because there were so many ad hominem attacks on him that I think he has become emotional and angry in the last couple decades. It's very sad, because he's definitely a smart guy. But the opposition just seizes this. Ivar Giaever is even worse. He got a Nobel Prize for his discoveries of semiconductor tunneling. He has become irrational about climate change, but unlike Happer, he doesn’t know most what was happening in the science world. And I used to be friends with him. And now, I publicly refute him, saying, "No, no, no. That's not true. This is what we know."

Zierler:

After so many decades in science, policy, and administration, working side by side with your colleagues and coworkers, how has this past year been?

Chu:

Well, what's been productive is, you're helping advance technology, but again, I have to be honest, we need these things and very fast. Any time you want to make a switch, it takes a long time. If you just postulate by 2040, 100% of the new cars sold are going to be EVs, That means 50% are internal combustion cars, which will stay on the road 15 to 20 years. That puts an automatic time scale. It's not like replacing your cell phone every three years. And the energy infrastructure has a decades-long life. Cars turn over quickly compared to power plants. Do you retire them before their useful life? That's hard because you've just built a new gas plant, the people who invested in the plant want to use it for 50 years.

So what's happening is, when the policymakers, Biden, for example, say, "We want to cut by 50% by 2030, and by 2050, we'll be carbon neutral in everything." It's a great aspiration, but how are we going to get there? We have a lot of greenhouse gas emissions from agriculture, and that sector has an inertia as well. Farmers have to be convinced to change their practices, and it's not going to come by regulation. Similarly, you've got to convince people to drink oat milk instead of dairy milk or eat meat substitutes. The older generation is unlikely to make a major change in their diets, and it's too much of a hot button issue for any lawmaker to say, "You're not allowed to eat meat." And yet, for beef and dairy, it's a ten-to-one ratio for the amount of substance, nutrition, and protein you get from beef versus plant-based protein. I'm joining another board of an oat milk company because I believe there's a lot of biotechnology that can be applied to decrease the GHG emissions in food production.

So these are all good things, but I'm constantly worried we are not moving fast enough, and that's a problem. There's a growing sense of urgency, which is good. Most Americans are not debating whether the climate's changing because they can see with their own eyes. More of them now believe that humans have something to do with it. But then, even if you recognize that you have something to do with it, or that we've got to be at a certain place by 2050, how you get there is the real problem. How do you de-carbonize agriculture? How do you de-carbonize industrial heat used to make chemicals and materials? Electric vehicles are easy compared to processed heat. If you go more and more electricity-based on intermittent sources like soil and wind, then energy storage and long-distance transmission become crucial. And even the United States was blessed with great wind and solar and four time zones, the estimates are, in order to get to 80% renewable electricity, which sounds modest, you need maybe three days' storage.

But what three days' storage means is that the storage capacity is capable of storing days' worth of energy. And it turns out to be about 10,000 times more chemical battery storage that we have today. And the price has got to be $30 a kilowatt hour to be competitive with peaker natural gas plants. Utility battery storage is now about $300. From what I know about batteries, both from my research and what's coming down the pike commercially in the next decade, chemical battery storage may drop to $100 for utility scale storage, which is more expensive than EVs. The price has got to be $30 a kilowatt hour to be competitive with peaker natural gas plants because it's got to have a longer life and have much higher reliability. And so, how are you going to get to $20 or $30 to keep parity with energy prices? And if you want to double or triple energy prices, it's a different story. So we have these serious issues. And technology is going to help, and you need both technology and policy. If the policy is too aggressive, energy costs will increase significantly, and there's going to be a pushback on that.

In Germany, they sadly decided to get rid of their nuclear power plants before the end of their natural lifetime. To compensate for the lost power generation, they started building coal plants. They don’t like that to rely on coal and natural gas has to be viewed as a transition energy source. Solar energy is limited and off-shore wind energy costs significantly more than on-shore wind and needs more transmission lines. So far, their energy transition is expensive, and the residential rates have doubled. The cost of energy to industry cannot rise to the point that the heavy industry in Germany that makes the chemicals, steel and cars will be less competitive their energy prices doubled. So these are very complicated issues. And so, even when you have society wanting to mitigate the risks of climate change, there are difficult trade-offs. Japan, Korea, you go down the list of countries that don't have the energy resources the United States has. Compared to many countries, we have it easy, but we're laggers in terms of making an energy transition. We should be leading the way.

Zierler:

There's almost a responsibility because we have it easier than other countries to do the R&D.

Chu:

We have better resources, we have inventive people, we should be leading the way in the development of better energy solutions.

Zierler:

Part of it is a nomenclature question, part of it, there's substantive science behind it, but as you were saying, in the late 1990s, when you were moving more fully into a biological world, to what extent were you a physicist moving into biology, and to what extent was biophysics really a merging of the two disciplines and where you saw yourself operating?

Chu:

Good question. I'm a physicist--once a physicist, always a physicist--but I am also learning biology. I don't want to make an instrument and hand it over to a biologist. I got interested in the biological questions and began to understand deeply the biological literature, with the help of my colleagues who are the subject matter experts. "What papers do I read?" And not only the biophysics, but questions biologists are interested in. And biophysics has blossomed and continues to blossom. But some of my trainees, my post-doc graduate students, when they went into biology, they kind of went native. [laugh] And they stopped using what they know in physics. And I don't do that. Right now, I'm doing research on how dynein molecular motors transport cargos in neurons. We developed new optical probes, so we can see things you couldn't see before. We can see these transport mechanisms at individual molecular steps in a live neuron for the first time, and with this new capability, we've discovered new things.

We have been analyzing the data, with a new theorem in statistical physics called the Fluctuation Theorem. The theorem was discovered accidentally in a computer simulation, and then proved as a general theorem in the 1990s. This theorem and its corollaries are helping us analyze and more deeply appreciate what was going on in biology. The new measurements, based on our particles, come from advances in materials science, but the statistical mechanics gives us deeper insight. In my old age, I have found I am still able to prove corollaries that the theorists initially missed.

While the questions we're interested are in biology, it turns out that biology is actually teaching us something new about physics, which I find amazing. To give you an example, you may know of the Feynman Lectures. And one of the lectures was a ratchet and pawl mechanism held at one temperature, linked to a set of vanes held at another temperature. In this lecture, one of the more famous lectures in his course, Feynman argues that a rachet and pawl mechanism can only do work if the temperature of the gas surrounding the vanes is hotter than the rachet and pawl mechanism. In his idealized model, Feynman argues that the system acts like a reversible heat engine. Other authors argue that the rachet motor system is inherently non-reversible since the two parts of the motor remain in thermal with both the hot and cold temperature reservoirs through the connecting shaft.

Physicists have drawn analogies of the rachet and pawl mechanism to molecular motors but where the effective temperature imbalance is supplied by the burning of chemical fuel. The burning of ATP means that the system is out of thermal equilibrium.

I'm going to cut to the chase. When we look at the statistical spread of displacements due to a dynein motor or motors, we find that fluctuations in the motion satisfies an equipartition partition theorem, but at a temperature greater than the cell temperature. The Fluctuation theorem, which is applicable to systems out of thermal equilibrium can be used to prove a new uncertainty principle which states that the product of the heat entropy and the orderliness of the operation of the motor motion must be greater than two times the Boltzmann constant times the effective temperature of the motor system. If you want to move the cargo with less statistical fluctuations, you have to expend more heat entropy.

In our analysis of the fluctuations in the motion of the vesicle, we are also able to deduce how many motors are being used to move the vesicle. Two motors move the cargo with half the dispersion and three motors lead to a three-fold decrease, but where the velocity of the motion is the same. Thus, we see that this is an example of the uncertainty principle: burning three units of fuel per given motion directly translates into three times less disorder in the motion.

Our statistical analysis of a dynein motor operating in a live cell shows that the motor system approaches a steady-state non-thermal equilibrium, and that there is decreasing the entropy of the motion costs more energy.

So that's hardcore physics. In addition, our measurements forced us to develop a new molecular model for how the motor works. The model is described by a few fitted parameters; but do these parameters make sense? But we go to the structural biology data and look at the size of the molecules, the kinetics, and the viscosity of the cellular environment, and it all matches with known measurements. A brilliant postdoc and I have been combing the literature for the last year and a half, understanding the structural biology, the kinetic experiments, and single molecule force measurements. We had the attitude that we're going to understand in depth all of the measurements and figure it out if the new model fits the date better that the old model. With a couple of exceptions, where we think there were mistakes made in the measurement, the whole body of literature actually fits the model better than the previous model. In fact, there was enough data that was inconsistent with the previous model, but it wasn't clearly recognized. But the fact that we're able to make new measurements forced us to make a new model. Then, we looked at the new model versus the old model, and paper by paper, checked to see which model the data fit better, we found our model is a better fit to the observations.

Zierler:

How much have you been an autodidact in biology, and how much are you relying on colleagues who were formally trained in the field?

Chu:

In the case of understanding the details of earlier measurements, that was self-taught. When we started reading the literature deeply, the guy who actually established the prevailing dynein model is a friend of mine. His name is Ron Vale. He's now the head of Janelia Farms. A very famous biologist. And I talked to him and one of his former postdocs about our findings, and we said, "OK, Ron, this is what we got." And he would ask some good questions that kept us honest. But the bulk of our knowledge was self-taught in the sense that we'd read some of the paper five times, ten times and poured over the experimental details in the supplementary information. I'm talking to my post-doc tens of hours per week. We read the papers many, many times in order to find out what they measured as opposed to what they concluded. In many cases, showed that if you had our model and their model, our model could fit their data at least as well as their model did.

It's a lot of fun. And occasionally, when two papers disagree, we try to figure out what went wrong. Now, normally, authors don’t say, "You made a mistake, and here it is." They let science sort itself out because people can get offended if other scientists point out a mistake. We haven't submitted the paper yet and have been thinking and writing for literally two and a half years as we digested 20 years of previous experiments.

Zierler:

Well, let's go back. Let's do some real oral history. Let's take it all the way back to the beginning. Let's start with your parents and their remarkable trajectories. Tell me a little bit about them and where they're from.

Chu:

OK, my father's father was a landlord. But he valued education, and he wanted all his children to be well-educated. And my father was the first male child, and there were four other women before him. But my grandfather was liberated enough that he said, "I don't care if they are women, they're all going to get PhDs." So the oldest sister, who my father adored, got her PhD at Michigan, and then went back to China and became a professor of chemistry in Peking University in the 30s. She had her feet bound. So it was crossing over from one century to another, and I just recently found a history of chemistry in China. And in this book, they said that she was the most influential woman chemist in China before the Communist Revolution. And my father said she's brilliant. She comes to the United States in '48, '49 because after the Communists take over, she would be killed. Also, my father. My father's father was too old, and he died of natural causes before they got down to the Shanghai area. Because he was a landlord, they killed the oldest male child in the family, who happened to be 21, just to set an example.

Zierler:

That's where your father was born, Shanghai?

Chu:

Yeah, it was a little suburb west of Shanghai called Taicang. And then, my father's mother died of childbirth complications. So my father's father took on another wife after that, but they were younger and all stayed in China. After the Communist Revolution, all contact was broken with that part of the family. My mother's father was a civil engineer. He got his PhD at Cornell. In those days, the tradition at the time, like Singapore today, you take a national exam, and if you do really well and the government sends you abroad to get a PhD somewhere. You come back and assume a position in the government, public service, or in a university. He got his PhD at Cornell in civil engineering. He went back to China and became a professor in civil engineering. He was very talented, and apparently a good administrator.

So he became the dean then president of his college in Nanjing at the age of 28. And by the time '49 rolled around, he'd been the president for many years, but he had to leave the country. Everybody was escaping with their lives. His brother was another interesting story. My mother's father's brother, her uncle, my grand-uncle--and my parents never told me this--got a PhD in physics in Paris, and then went back. And when he was doing his PhD, he was working for a guy named Perrin. Einstein suggested that if you measured Brownian motion, you may be able to measure Avogadro's number. And Perrin did this by tracking Brownian motion particles, and my grand-uncle was the graduate student who did the work. Perrin received a Nobel Prize for this work. The French government was so appreciative of the role my grand-uncle played in this work that they gave him a medal the year Perrin’s Nobel Prize was awarded. So there's a long academic history on both sides.

Zierler:

Not just academic, scientific.

Chu:

Yes, and scientific.

Zierler:

And your mom's family was in Nanjing?

Chu:

Yes, Tianjin, Nanjing. Right, Tianjin. So anyway, they all had to leave, too. My parents, at the end of World War II, went to MIT to go to graduate school. And after the Revolution in '49–I was born in '48, and they couldn't go back. They were very bitter about that, because they both had privileged lives in China.

Zierler:

They met at MIT?

Chu:

No, they met in Tsinghua University, which is like the MIT of China. And the two big universities were Peking University and Tsinghua. And then, during the War, those two merged with two other universities, including my grandfather's, and went to Southwest China (Kunming) to escape the Japanese. World War II was in Northeastern China. So then, they went to the United States to go to graduate school.

Zierler:

Were they married when they came to the United States?

Chu:

My father was a senior, my mother was a freshman when they were introduced. I think both families wanted to marry into an intellectual family or something like that. [laugh] So my father went to MIT first, and my mother joined a couple years later.

Zierler:

In terms of class status, were they equivalent, coming from their respective families?

Chu:

Well, yes, in the sense that one was from a rich landlord who valued education. And so, his daughters were getting PhDs, which was kind of amazing in China. In science. Doubly amazing. And my grandfather's brother rose to a high level in the Ministry of Education. He also worked in the founding of UNESCO. So they were real big shots. But they had to escape with their lives.

Zierler:

What was their course of study at MIT? What programs were they each in?

Chu:

Chemical engineering for my father, and economics for my mother. But my mother got pregnant and gave birth to my older brother in 1946 and dropped out of school. And my father continued and became a professor first at Washington University in St. Louis, but then there was a new up-and-coming department, Brooklyn Polytechnic, a very legendary chemical engineer named Donald Othmer, who recruited my father. So I grew up, first, in Queens, and then Long Island.

Zierler:

What was your father's research specialty?

Chu:

Thermodynamics. And in particular, the equations of thermodynamics of heat transfer and mass transfer. He realized that measurements in domain could be used to measure thermodynamic properties in the other domain, so he became pretty well-known very early in his career. And there's an honorific society in Taiwan called Academia Sinica, and he was elected to when he was young. It's kind of like the National Academy of Sciences in the US or the Chinese Academy of Sciences. And my grandfather on my mother's side was also elected a member, and later, I was elected a member. So it was the first time that three generations of scientists belonged to the Academia Sinica.

Zierler:

It's a family business.

Chu:

Yes, something like that.

Zierler:

Were your parents' pedigree such that they learned English in China? That was not a barrier in terms of coming to the United States?

Chu:

They had to learn a little bit of English. They had accents, of course. But remember, my father's older sister, ten years older, got her PhD at the University of Michigan. So it wasn't as though English was unknown, and the educated elite knew English. But they certainly had accents. And there was a lot of prejudice against the Chinese in those days. And it's very sad because my aunt was a Chinese woman, and she couldn't get anything close to the position at the best universities in the United States. The best she could do was a job in a small girls' school that taught young ladies how to be high school teachers.

But she was so good that she got significant funding, and for the next 20 years, she could hire her husband and started a lab at this small girls' Catholic school. I thought it was amazing. The story of my grandfather is equally amazing. He's 50 when he flees to the U.S. but has been a bureaucrat since the age of 28. And usually, if you're a bureaucrat that long, all is lost and you don't go back to science. In 1950, he's not going to be able to get a job as a professor, and certainly not as a university president in the US. So he said, "I've got to learn how to do civil engineering again." Which he did. He told us when we were kids that he would walk the Queensborough Bridge and other things, looking at how they were made. He taught himself civil engineering, brought himself up to date, again started practicing civil engineering at age 50 from scratch. He started a private practice, got jobs, and supported himself as a practicing civil engineer. Because that's what he knew.

And I was looking at some family history, I found about four or five years before he died, he got the highest award in a civil engineering society for his contributions to cement technology. So he did that after he was a university president and a bureaucrat. After I was the Secretary of Energy, I wanted to go back and start a new group in new areas. As one of my former graduate students said, "Yeah, he wanted to come back to Stanford and become an assistant professor all over again. He had no students, no support, and no lab space." I did have tenure. Maybe it runs in the family that ex-bureaucrats can return to science.

Zierler:

I'd say so. Where were you born?

Chu:

I was born in St. Louis, when my father was a professor at Washington University. And then, when I was 3, they moved to Queens because he got the job at Brooklyn Polytech. And then, after a couple years there, they moved to Garden City, which is in Nassau County, because it had a fabulous public school. So we were in the poorest neighborhood of Garden City, which is an upper-middle class neighborhood. There were no Blacks, there were only two Chinese families in the whole town of 25,000. My parents moved there because of the public school system. Some of my high school classmates and I just had kind of a West Coast Garden City High reunion of the class of '66. Out of the six people in that little Zoom reunion, three or four of them were from immigrant families who moved to Garden City because of the public school system, and they were in the poor section of town. And you sacrifice everything to get in a good school system, you don't have enough money to send your kids to private school. And Garden City had a great public school system.

Zierler:

Do you have any memories of St. Louis, or you were too young?

Chu:

I only have a very brief memory of how hot and sweaty it was. And I went back decades later, and it was still hot and sweaty.

Zierler:

What was your first language?

Chu:

English. My parents only spoke to us in English. Unlike today, they did not speak to us in Chinese because they said, "You have to do well in school." And so, they would only speak to us in English. And they'd speak to each other in Chinese.

Zierler:

Mandarin?

Chu:

Yes. They did not speak to us in Chinese because they thought we'd grow up confused. And they didn't understand in those days that kids are really smart with languages. And nowadays, it's the exact opposite. You're an immigrant family from whatever country, speaking only in your native tongue, and I've seen cases where immigrants from two different countries and they speak to them in both languages, but not English. And then, they go to kindergarten, and they sort it all out. And by the time they're in 1st grade, they're fluent in three languages. But that was not what people thought in those days. So I'd say I have about a 1-year-old vocabulary.

Zierler:

So you really didn't pick up any Mandarin just overhearing them?

Chu:

A little bit. Only because when they didn't want us to hear something, they would switch to Chinese. So you'd hear a little bit. My accent is terrible. But when I go to China, if I'm there for three or four days, I begin to understand more and more Chinese. It kind of comes back a little bit from early childhood.

Zierler:

It's in there deep somewhere.

Chu:

Yes, but the knowledge is deeply buried. We were all spoken to in English, and that’s the way it was. And we had this extended family, mostly on my father’s side, of his sisters and him. And my mother’s side, her grandfather and grand-uncle, we would see at least once a month. They lived in New York, and we’d travel to see them and eat at a Chinese restaurant. We’d all drive in from Long Island. So when I was growing up, one group was in Philadelphia. My father’s older sister was in Hollywood working at her girls' school. My father's other sister married a chemist. So there was this extended family of people brought up in this scholarly environment, and they expected us all to be good students.

Zierler:

Now, is the language decision a window into their broader ideas about assimilation? In other words, did you grow up with any Chinese traditions or customs?

Chu:

We grew up eating Chinese food. My mother was a good Chinese cook, but we also ate "American" food as well. When we were growing up, we were in an essentially all-white neighborhood. And kids want to be like the people around them. Occasionally, at a very early age, there were some taunts. And I did the mature thing, which was to start fighting with them. It only took one fight for the taunts to stop. The taunt went something like, "Ching chong chinaman sitting on a fence, trying to make a dollar out of 15-cents." You might have heard this. That taunt really pissed me off, and I got into a little fight. And they left me alone after that. This was in grade school. So we grew up an immigrant family, Brooklyn Poly professors weren't being paid much. And so, we all had paper routes, and I shoveled snow, things like that.

Zierler:

Did you have a sense of your parents' politics when you were growing up, specifically with regard to China, the Cold War, Taiwan, those kinds of things? Did you engage them in those kinds of talks?

Chu:

I did have a sense of their politics because they were so bitter about China because of the Revolution. And they were sympathetic to Taiwan because their feel was that's where the real government was. Even after China reopened, they never went back. They refused to visit. They were Republican because they believed the Republicans were more in favor of defending Taiwan and more anti-Communist.

Zierler:

Although, Republican means a very different thing in the context you're speaking of.

Chu:

Yes. Well, the current Republican party currently is unrecognizable. So I knew a little about their politics, but mostly, they focused that we should do well in school. I was the big disappointment within my extended family. My older brother went to Princeton, the two male cousins went to Harvard, the older female cousin went to Bryn Mawr, and then it was my turn. I applied to Yale and Princeton, got rejected, and went to University of Rochester, my “safety” school. Growing up, my older brother was number one in his class, and he set a record for the cumulative average record for the school. When I was following behind, my teachers said to me, "Oh, you're Gilbert's brother. You are going to do just as well." But I was a ne'er-do-well, wasn't as disciplined as my brother, and got Bs in German. And so, I did get interviewed at Princeton and Yale but apparently didn't make the grade. I went to Rochester where no one there had heard of my older brother. I think it was the best thing to happen to me. Because by this time, my self-image and confidence were crushed. I was the first Chu not to go to Harvard or Princeton. It was terrible. But by the end of the first semester at Rochester, I knew it was going to be OK.

Zierler:

Yeah. Rochester has some incredible programs that are as good as any place in the world.

Chu:

Right. And among the top people in my class there were one or two of them did get into the Ivy Leagues, like Yale, but for whatever reason, decided to go to Rochester. But it was great, because had I gone to Princeton or Yale, I would not have been as much of a standout. And so, having professors take you under their wings is really good for your self-confidence.

Zierler:

Growing up, did you have a sense of your father's career? Did you understand what it meant to be an academic scientist? Did he involve you in those kinds of things?

Chu:

Sure, he told us when we were in grade school, "Don't marry until you get a PhD." So yes.

Zierler:

Besides the family expectations, how did you demonstrate your own interests in science? What kinds of things were fascinating to you as a teenager, for example?

Chu:

It started earlier on in tinkering. I played with erector sets, model airplanes, chemistry sets, all those things. Actually, much more so than my older brother. My older brother also built model airplanes, but have an erector set or chemistry set. I loved to tinker. In those days, you could go to a local chemical supply store and buy chemicals needed to make bombs and rockets, so of course, I made bombs and rockets. Surprisingly, at Bell Labs I learned that a number of other people made rockets and bombs. One person, another Nobel Laureate lost part of one of his fingers. Luckily, I still have all my fingers. And so, I'd save up money used it to buy chemicals in those days. So that was lots of tinkering. In school, the first memorable course I took was 9th grade geometry. And I just caught fire over the subject. The idea that you can prove things with a few axioms and the logic just electrified me. It was so much different than high school algebra, where you memorized the quadratic equation, and learned how to plug in numbers. Geometry was exciting.

And the next class that really electrified me was physics in my junior year, then AP calculus in my senior year. And the physics teacher was a legendary physics high school teacher. He got national awards. And he took me under his wing, and that was encouraging. When I went to college, I was a math major as well as a physics major. A couple of math professors also took me under their wings. In kind of a funny way, I started getting invited to faculty social meetings when I was an undergraduate. But they didn't invite the graduate students, which was kind of amazing. But in those days, in Rochester, you could drink when you were 18, and I was older than 18 when I was invited to the faculty meetings. There were scotch connoisseurs in the math department, and they introduced me to single-malt scotches and how to appreciate them. A physics professor introduced me to wine.

One summer, I was in a math program for supposedly math prodigies. There were a dozen of us. Each one got assigned at University of Indiana to some professor. I wasn't a math prodigy, but I was OK. And then, my algebra professor was at Purdue for the summer. And he called me up and said, "Steve, why don't you round up a couple girls, and we can go to Chicago and watch a Cubs game?" So I said, "Sure." It was all very innocent, all of this is probably illegal now. Faculty members are not supposed to teach their undergraduates how to drink or double date. I don't think they would've treated me that way if I went to Princeton or Yale.

Zierler:

Being an undergraduate in the late 1960s, graduating in 1970, were you political at all? Were there campus protests at Rochester?

Chu:

Great question. I was the class of '70 there, and in '69, '70, a lot of Vietnam stuff was happening. They'd started the draft when I was a junior. I got lucky, and my number was 305, so I was not going to be drafted. I was pretty apolitical, but I was against the war in Vietnam. And with a friend of mine, we decided instead of being radical hippie types, we went to a neighborhood around Rochester and knocked on doors, all dressed up in our best clothes. I remember talking to these middle-aged couples, and they were so charmed by us because we weren't hippies and angry, we were just trying to explain that, "This is maybe a war we shouldn't be in and were trying to think about our position. "

So that was the extent of my political involvement. When I was at Berkeley, I actually assiduously tried to avoid places where there was tear gas. Because by then, Vietnam led to war in Cambodia and there were lots of student protests. I was liberal-leaning, against the wars, but I wasn't really super active in that way. I cared about it and was willing to do low-level activism, knocking on doors, and things like that. Trying to put a different face on young people's feeling about the War.

Zierler:

Did this put you at odds at all with your parents and their politics?

Chu:

No. I didn't ask them. They may not have known about it. This is very typical Chinese, my parents' idea towards politics was, "Don't go into politics. Don't do political things. Don't demonstrate. Don't do anything." That's a very Chinese attitude. My younger brother ran for college council and won. And my parents were horrified. They said, "What is your brother doing? He's getting into politics. That's terrible. He should concentrate on science." And growing up, I knew I wasn't going to be able to compete with my brother. In 9th grade, I stopped going to class. I rebelled for two months. My parents were beside themselves. I finally went back and took the finals, and that was fine. My younger brother was even worse. And by the time the family moved, he was the only kid left.

My parents’ emphasis on education and how they tried to motivate us is typical of Chinese and Jewish families. "Gilbert's doing well in school now. Steven's doing well in school. What about you?" He had a falling out with our parents, and he just left home. So he never graduated from high school. He dropped out, left home and bummed around with some friends of his. He did get in the Guinness Book of World Records with several of his pals for going to every stop on the New York subway system on one token, the fastest you can do it. He broke it by about 30 minutes. Because you have to really think about how to plan the rides to catch all the express trains. And they were shooting for the record, so they got some witnesses for Guinness.

After a year of bumming around and taking odd jobs, he decided to return to school, and was able to talk his way into attending UCLA. His wife describes what my brother did is he used a loophole that was designed to get athletes into UCLA if a professor vouches for you.

So he apparently had charmed some professor into vouching for him, even though he didn't graduate from high school, didn't have the blessing of his high school, his parents, or anything. By this time, he wasn't taking any money from our parents. So he went to UCLA, ran for student government. He introduced me to marijuana. He's three years younger than me. So he was a bit of a wild person. He got a PhD to avoid the draft by the age of 21 or 22, and then got a law degree from Harvard. And then, he went into intellectual property rights law and became the managing partner of a very distinguished firm, Irell and Manella, by the time he was 40. And he was probably, by the age of the early 40s, one of the most famous patent litigators in the United States.

I have a funny story about how famous he is. When I first arrived at Stanford from Bell Labs, there was a series of patent filings. I worked with a patent attorney, and at the end of our first meeting, I asked, "Oh, by the way, do you know my brother?" "Who's your brother?" "He's Morgan Chu." He just stopped, and his jaw dropped. He said, "Your brother is Morgan Chu?" "Yes. So you've heard of him." "Yes. He's the most famous patent litigator in the United States." This is when he was 36.

Zierler:

Were you a true double major insofar as when you were thinking about graduate schools, you could've gone on for mathematics as well? Or was physics always the real focus?

Chu:

By the senior year, it was going to be physics. But by junior year, I was taking graduate courses in math.

Zierler:

Was it always more applied math or even pure math that you were doing?

Chu:

Pure math. And for example, there's this course called linear algebra. It was a required course for math majors. So I went up to my professor and said, "Look, I looked at the book. Do I really have to take this class?" He said, "Well, it is required." I said, "I'll make you a deal. Let me TA for it, and if I do a good job, will you give me credit for it?" And he said, "Sure." So that summer, I read the book, and the next year TA-ed the course. So by junior year, I was taking graduate classes. And I loved it. I would stay up late at night proving theorems. But I also realized that I'd be OK, but I wasn't going to be spectacular. So I told myself, "I'd rather be a mediocre physicist than a mediocre mathematician because there's no future for a mediocre mathematician." I also thought I wasn't weird enough to be a mathematician.

But then, I thought I was going to be a theoretical physicist. When I went to Berkeley, I did well on the qualifying exams, my thesis advisor assigned me a theoretical physics problem. During the time I was supposed to be working on a theoretical problem, I was tinkering in the lab. I wasn't making bombs or rockets anymore, but I was tinkering. He would ask me, "How are you doing this problem?" And it happened to be an astrophysics problem. I finally told him, “I'd rather be an experimentalist." So he said, "Sure." Because that was his first foray into a theoretical physics problem for him.

Zierler:

I was curious, though, given your abilities in math, if you would've leaned more towards theoretical physics.

Chu:

I was going to be a theoretical physicist. Except for the fact that I loved doing things with my hands during my childhood. My older brother went into theoretical physics. When I entered Berkeley in graduate school, he entered as a post-doc in theoretical physics. Theory is very competitive. He was 2 post-docs out of 700 applicants for this position in theoretical physics. He was near the top, but he also began to realize he wasn't going to get a faculty job at Berkeley, Caltech, Harvard, or any place like that. The world doesn’t need that many theoretical physicists. He decided he wanted another career. So he went to medical school, got an MD and PhD. He collects degrees. The smartest brother out of the three of us is my younger brother, Morgan.

Zierler:

What kind of advice did you get from professors about graduate schools to apply to, people to work with, programs that would be good for you?

Chu:

Well, it looked like theoretical physics, but they didn't really say much besides–I said, "What do I say in my essay? What do you suggest?" And one of them said, "Don't bother with that. Just say what you want. You might say something like, 'I like physics. I enjoy doing physics. It's kind of fun for me. I want to do more of it.'" So I applied to Stanford, Berkeley, Princeton, Stony Brook. C.N. Yang was at Stony Brook. I got rejected at Princeton, possibly because they required four letters of recommendation, while the other schools required only three letters. I was kind of irked by that and very rebellious. So I got one of my classmates, a good friend of mine, who was also applying to Princeton, and we wrote a letter for each other. We clearly identified ourselves. "I'm applying, I'm an undergraduate at the University of Rochester. I'm writing a letter for…" Princeton rejected both of us. But we both got accepted to Berkeley. I also got accepted to Stanford. There was another friend of mine who was a freshman, who transferred and went to Caltech. And we kept in touch. When it came time to graduate school, he and three of us at Rochester all decided we were going to descend on Berkeley.

Zierler:

I'm curious, coming from a more homogenous environment in Rochester, a more “white” place, to the Bay Area, did that affect your identity, your sense of Asian-ness at all when you got to Berkeley?

Chu:

No, actually, I discovered I was Asian when I was at Rochester. But then, very quickly, I also discovered that I was Jew-ish. Half the undergraduate class at Rochester was Jewish, and they called me “Chustein,” and I became a member of the tribe. There were many more Asians in Berkeley, for sure. But I did discover I was Chinese when I was at Rochester. The rest of my housemates at Berkeley were Caucasian. I wasn't hanging around the Asian community. Sometimes, ethnic groups really hang out together, and that becomes most of their social circle. And my social circle was not based on that.

Zierler:

When did you get to know Eugene Commins?

Chu:

First quarter of my first year, he taught a statistical mechanics class. I had thermodynamics, but not statistical mechanics at Rochester, so it was an upper division undergraduate class. He was a spectacular teacher, and when I took his class, I remember I complained because I didn't get 100 on the final, and thought I did not make a mistake. I said, "What did I do wrong?" And he kind of looked at me and said, "What are you complaining about?" I'm not sure whether I took another class from him my first year at graduate school. I might have. He was teaching weak interactions class and astrophysics classes. He was such a spectacular teacher that whatever class he taught, I would take.

Zierler:

So you connected with him as a student before you became his student, so to speak.

Chu:

Correct. And then, the beginning of my second year is where you first have to take the qualifying exams to proceed. And in those days, they flunked a third or a quarter of the students, which means you have to take it again. It was a real exam. So I took it, and then he approached me and said, "Have you decided who you want to work for?" And I said, "No, but I was about to ask you about working for you." He liked me from the stat mech class I took from him. I admired him as a teacher before I knew he was an outstanding researcher. He always had a small group, and his group was shrinking to zero by the time I joined. By the second year, he had two graduate students that were about to leave. For a while, I became his only graduate student.

Zierler:

And what was his research at that point? What was he working on?

Chu:

He was looking around for something new. He had used atomic physics methods to test time reversal invariance, a very basic symmetry and measured zero departure. But he developed a reputation of doing really exquisite measurements like that. He did research using beta decay, nuclear physics. The first experiment, he was doing some experiment in weak interactions tests using beta decay using the cyclotron linked to an atomic beam machine, but he was casting around for something to do. He applied for an astrophysics grant. It was rejected. But he was a member of Lawrence Berkeley Lab. He was part of a big block funding grant. The people at Berkeley knew he was really good, even though he wasn't good at getting grants and stuff like that. But the Berkeley Lab took care of him because he was just good, which is a nice position to be in.

And by then, I was his only graduate student of the next generation. And then, another student joined, and then I got him to hire my friend I wrote a recommendation for. He was doing a high energy physics experiment, and it wasn't working out. So I said, "This guy's a really good theoretical guy." And then, a small group got started around what had become my thesis experiment, namely using lasers to test parity non-conservation in atomic transitions. Commins had written a textbook on weak interactions, was an expert on weak interactions, and a new set of graduate students was growing around this experimental effort. And so, it was interesting because he had a very good track record for training students, many of them successful physicists. In my generation, I was the oldest of this group.

But of that generation, the one immediately behind me is a professor at Stanford now. He followed me to Bell Labs. Someone else would've been my first graduate student, was a beginning graduate student when I was a post-doc, and I used my faculty start-up money to buy equipment for a better version of my thesis and postdoc experiment would've been my first graduate student, had I returned to Berkeley from Bell Labs. She's now the provost at Stanford. They're both in the National Academy of Sciences. So it was a pretty good bunch of people. Another person who went to Amherst but did spectacularly well at Amherst. Anyway, Commins's reputation as a lecturer was just out of this world. And then, he had a very small group, but his students had a very high success rate.

Zierler:

Did you have any interactions with Geoff Chew?

Chu:

Yes, when he was chair of the department. And he was the nominal advisor of my older brother. But I had interactions with him only as chair of the department. Because he was the one who offered me the job as assistant professor. And he was the one who formally asked me to apply. And my letter of application was very short. It was, "Dear Professor Chew, my advisor, Professor Commins, has urged me to apply for the position of assistant professor in the physics department. Consider this letter my application." By then, I'd gotten to know a bunch of professors. And I was talkative, and started chatting with Ron Shen, Erwin Hahn, Gene Commins, Richard Maris, Charlie Townes, and others. I guess they began to notice I was a little different than the other graduate students. In any case, the Physics Department offered me an assistant professor job while I was a postdoc.

Zierler:

How much were you hanging out at Berkeley Lab? Was that your spot? Or was it really more the department?

Chu:

I would only go up there to use their stores and things like that. But I did a reading course with Gerson Goldhaber in the Trilling-Goldhaber group. So I knew a bunch of people there, too. And then, on the second floor in Birge Hall, there was Gene Commins, Herb Steiner. So I knew a surprising number of professors when I was a graduate student.

Zierler:

What about for instrumentation? Was that your go-to, the lab, to do everything?

Chu:

No. Machine shop was my go-to place. Commins and I both loved to do machining. He was really hands-on, and he did a lot of machining. I machined everything since we were poor. I went to Berkeley Lab to go through their surplus equipment and also scrounged equipment from Lawrence Livermore Lab as well. But I literally made the laser with my hands in the machine shop.

Zierler:

And what guidance, if at all, was theory giving you at this point? In what ways were advances in theory influencing the ways you wanted to build the laser and what you wanted the laser to do?

Chu:

Virtually nothing. The theory was in the experiment we were doing to test it. Because I thought if you could say something meaningful about the unification of the weak and electromagnetic interactions with a bench-top experiment, that would be the cat's meow. In terms of theory, in terms of the laser, there was some basic stuff that I wouldn't call even theory. There were little bits of stuff. We were so poor, I started making my own spark-gap switches for a flash lamp pump dye laser I was building. The laser used a double elliptical cavity. An ellipse is used because rays of light coming from one of the focal points of the ellipse and bouncing off of an elliptical reflector would be focused onto the other focal point. That was well-known, and a double ellipse meant that you could have more uniform illumination because you could place a flash lamp on both sides of the column of the gain medium.

How do you make a double ellipse? Well, it's a conical section, so I took a mill head and tilted it. If you take a circle and turn it on its side, and it becomes an ellipse. So I was able to machine an reflector whose cross-section was elliptically shaped. The first ellipse I machined out of metal, and then polished it to be reflective. However, using the best metal polish methods, one can get to 70% reflecting. Also the polished metal tarnished quickly. I had this idea, "What if I machined out of carbon blocks with half elliptical cross-sections, and when sandwiched together, became a full ellipse.” I talked to a glassblower in the physics department to help me. My idea was "Look, what we're going to do is heat up this Pyrex tube until it's soft. And we heat up the block, you put the molten soft tube in between the hollowed-out carbon parts, close the sandwich and blow out the soft glass so it expands and fills up the ellipse." Well, it's glass, so you can evaporate aluminum on the outside, which becomes a 90% reflector across the whole spectrum. But the glass protects it, so is an aluminumized mirror.

The outside of the glass fills up the hollow space within a fraction of a millimeter. So I made the carbon mold. I'm not sure we got a patent on it, but I published a paper on it. The double elliptical glass cavity more than doubled the laser power because the reflection was so good.

I also wanted to discharge the flashlamps as quickly as possible. Because of technical reasons having to do with the photo-physics of dye lasers, you wanted a very short pulse. In order to get a very short pulse, you had to design a very fast discharge circuit. I had to make my own spark gaps for high voltage electronic switches. In the end I was able to find some surplus, unused thyratrons at a junkyard in Livermore that were much better than my home-made spark gaps. Thyratrons were invented for high current, high voltage switching for radar applications. So I was scrounging everything.

I was scrounging capacitors, but they weren't really fast. They weren't low inductions capacitors. I actually started making my own capacitors, but finally I said, "This is screwy." But I was scrounging capacitors, and they were leaking insulating oil and they weren’t low inductance capacitors in any case. I finally convinced Gene, my advisor, that I could not make a low inductance high power capacitor as good as commercial capacitors, so he let me buy a capacitor. In order to increase the speed of the flashlamp discharge, we ran the flashlamps in what was known as simmer mode. When you start a discharge in a flashlamp, the discharge starts with a little filament, and then it widens to fill up the flash lamp. But while current is a thin filament, it has very high inductance. The thinner the conducting filament, the higher the magnetic field strength, and the higher the inductance. I began by running the flashlamps in low current simmer mode. I then learned about an experiment at SLAC that was using a flash-lamped pumped dye laser designed by a guy named Charlie Prescott.

At SLAC he was part of a high energy experiment designed to test the same theory that unified the electromagnetic and weak interactions. They were using circularly polarized light from a dye laser to photoemit circularly polarized electrons that would then be accelerated to GeV energies. We started trading notes on how to design these flash lamp pump dye lasers. He told me "What you're doing is great, but I found that you ran a higher current in the lamp, the conducting filament expands to fill the full diameter of the lamp, and with this higher current simmer, it has even a lower inductance." So the fast discharge due to the high current simmer, the highly reflecting double ellipse and other refinements produced a much better laser compared to anything commercially available. The physics department got really impressed with my laser, but there was very little theoretical insight in any of the engineering. Well, a little bit of elementary E&M about inductance.

Zierler:

You underplayed it before, but obviously your experiment was a lot more well-defined than you said, in terms of saying to Commins, "Oh, just let me defend at this point." What had you accomplished up to that point of defending the thesis?

Chu:

We started doing the spectroscopy, and the idea was that you measure the transition rates between an atomic ground state and excited state using circularly polarized light. The different experimental configurations are mirror images of each other. Electricity and magnetism is symmetric with respect to a parity transformation, but the weak interactions are not parity symmetric. If the atomic transition were due to a combination of photons (the electromagnetic interaction) and Z bosons (the weak interactions) as described by the Weinberg-Salam-Glashow theory the transition rates would not be equal. The trouble is the part of the transition due to the weak interactions is tiny compared to the electromagnetic interaction. In order to make the effect bigger, we chose a very weak (highly forbidden) electromagnetic magnetic dipole transition. So my thesis ended up being the measurement of that transition rate, which was the weakest induced transition ever measured in physics. My thesis experiment was to measure the asymmetry in this rate with a precision of one part in a thousand. So it was a hard experiment. And then, it got even worse because it turned out there were backgrounds that I couldn't get rid of due to collisions.

And so, we knew if you put it on an electric field, you can the interference between the forbidden electric dipole and magnetic dipole transition amplitudes big enough to rise above the collision background, but it made the interference effect smaller. So the interference turned out to be not a part in a thousand, but ten parts in a million. But at least you can see the signal. Now, in subsequent ideas, I realized that if a much narrower bandwidth laser is used to excite the atoms, the experiment can be improved. The basic vacuum chamber and laser system was constructed during my graduate student days. The next three graduate students used that same apparatus I built, pushed it much harder and showed that all of the systematic effects could be understood. And they pushed a little harder, tried little improvements here and there.

A successor experiment, done by Persis Drell, used a much better laser that we built during my final time as a postdoc in the Commins group. The laser that was built was another advance in state of the art lasers, and resulted in yet another paper on lasers.

And that turned out to make an even better measurement. And then, I had another idea that would make it even better using atomic beams. By then, Carl Wieman had gotten interested in this area, and he began using atomic beams and CW lasers. He worked with cesium, we worked with thallium. And then, I did research on getting a very narrow CW laser to excite the forbidden transition in thallium. If our experiment could be done using an atomic beam, it would be greatly improved. The problem is the light needed to excite the forbidden transition was in the ultraviolet spectrum. I started consulting with a laser company, Coherent Radiation, because I convinced them that UV light could be generated within a laser cavity with high circulating power. The laser cavity was designed so that a frequency doubling crystal would be part of the cavity. This work was turned into a commercial product that Coherent Radiation marketed and sold. By the time I was a postdoc, I was good at making both pulsed and CW lasers.

Zierler:

To foreshadow to your supervisor's reaction at Bell Labs, did Commins or anybody else ask you, "What's this going to be good for?"

Chu:

Well, if you make a better tool, it's good for a number of things. And that's what I've done in my later life. I have kind of intuition about recognizing areas that were ripe for technology breakthroughs. For example, dye lasers were invented in 1966 and it was easy to see that a tunable laser would revolutionize atomic physics. If you can do something people can't do before, and you address the right important problem, the chances of you discovering something new are very high. And I used to say in my older age, "Look, if you look underneath a rock, but you're the 100th person to look underneath it, the chance of you discovering something new is very small. If you're the first person to discover this view, you don't even have to be very smart." So what I did is say, "What is happening in technology that's maybe due to others, maybe had nothing to do with me, but if you can get to the front of it and help push it a little bit faster, then you'll have a new science tool." And laser cooling and trapping was a technology. Optical tweezers applied to biological molecules and single molecule FRET (fluorescence energy transfer) were also new tools.

But once you have this tool, then you look around for the most important problem. So I would dream of the problem, but I didn't know how really important it was. So I'd go to a biology colleague and say, "Look, I'm thinking of doing this. Does this make sense?" And sometimes, they would say, "You're asking the right question. This is the most important problem in biology." And other times, they would say, "Nah, people are not really interested in that." [laugh] And so, that helped guide me. So I would use my colleagues as sounding boards, and quite often, I would get, "My God, you can do that? I'll work with you."

Zierler:

Besides Commins, who else was on your thesis committee?

Chu:

Erwin Hahn, who was a very, very good physicist, who invented what's called a spin echo. He and one of his students also discovered self-induced transparency. Dick Marris. He was an atomic physicist who used the Bevatron HILAC to make heavy ions to test relativistic quantum electrodynamic effects. There was also a theoretical physicist, Eyvind Wichmann, who was a good friend of Gene’s. They were all good friends.

Zierler:

Anything memorable from the oral defense?

Chu:

Not really. The outcome was assured.

Zierler:

Very pro forma.

Chu:

We all had a good time.

Zierler:

When you were considering post-docs, was NIST on your list at all?

Chu:

No, I did a post-doc at Berkeley. I didn't consider anywhere else. It was my deal with Commins. I wanted to finish the experiment. That was a very important experiment. And so, I really wanted to finish it. Steven Weinberg would call my advisor and say, "What is the answer? I promise I'm not going to tell anybody about any preliminary data.” JD Jackson, who wrote the standard textbook on electricity and magnetism and who was a high energy physicist, once saw me around lunch time, and asked "Where are you going?" "I'm going to the pool for a swim." He said, "What? Why aren't you in the lab? There's important work to be done." So, the world was watching.

Zierler:

What was Weinberg interested in?

Chu:

Well, we were testing his theory. This Weinberg-Salam-Glashow theory. He invented the fundamental, rudimentary stuff of unifying the weak and electromagnetic interactions. He, and Salam independently, invented the simplest theory. Glashow had done some earlier work, so that's why it's called Weinberg-Salam-Glashow. And so, the year our result came out, we were competing with the SLAC high energy experiment, and had done a definitive experiment verifying the Weinberg-Salam-Glashow model. They completely scooped us in the summer of ’78 with a beautiful experiment. We only had a marginal result. That autumn, Weinberg, Salam, and Glashow were awarded the Nobel Prize the following year. It was a big deal. The world was watching, and it was fun to do something that was that exciting when you're a little graduate student post-doc.

Zierler:

Did you do all that you wanted to or what Commins expected of you as a post-doc?

Chu:

No, our result was less than a three-sigma result. I wish it'd been a five-sigma result. Really definitive. So we didn't have the precision. Carl Wieman did a much better experiment using better laser technology. He was also really good at making lasers and also very smart. By that time, I has moved on and was doing other things different than my thesis and postdoctoral work.

Zierler:

Did Bell recruit you? Were you on the market and looking for opportunities?

Chu:

That was very interesting. So yes, when Berkeley gave me an opportunity to go elsewhere, I started writing letters. I looked around. I applied to Bell and IBM, to MIT. I got rejected by MIT. Dan Kleppner said, because I'd been a graduate student and post-doc with the same advisor, "We're looking for people who are more independent." By that time, Yale and Princeton, the two schools that rejected me as an undergraduate applicant, wanted to interest me in an assistant professor job, so word was getting out. But I was not interested, and I very quickly winnowed my choices to Bell and IBM. I remember being interviewed at IBM, giving a talk, and they said, "Oh, I don't know whether we should even give you an offer." "Why?" "We're sure Bell Labs is going to give you an offer, and we can't compete with Bell Labs." I said, "They might not give me an offer. Why don't you give me an offer?" At the time, Bell Labs was really the king of the hill.

Zierler:

Was IBM saying that both in terms of salary and instrumentation?

Chu:

No, there were some groups that were doing laser physics. They had good people. One of the early pioneers of lasers, Peter Sorokin was there. Dan Grischkowsky was there. There were a bunch of people who were really good doing some very fundamental physics with lasers that I was attracted to. At Bell Laboratories, there was Hyatt Gibbs, a former student of Gene Commins, who was doing very exciting work. Bell, at first, Bell wasn't interested, but Gene said, "You should look at this guy."

So they invited me for a visit and after the visit, offered me a job. Also, Sam McCall, who was an Erwin Hahn student, was at Bell Labs. So there were a bunch of Berkeley people at Bell Labs. And then, there were a whole bunch of laser people in Holmdel. But I decided I'd rather go to Murray Hill because there were fewer laser people. I would be more unique. And that always attracted me. I don't want to go with the crowd, and so it was a good decision because it actually helped me become a more versatile scientist, not just to stay working in a group of what I called “laser jocks.” You know, "Have laser, will travel." It was being introduced to a wider set of problems.

Zierler:

Did you cross paths with Bill Silfvast at all?

Chu:

Oh, yeah. I was his department head.

Zierler:

Oh, there you go.

Chu:

How do you know Bill Silfvast?

Zierler:

I interviewed him.

Chu:

Yeah, he was a pioneer of metal vapor lasers and excimer lasers. I was at Murray Hill, and then Chuck Shank wanted to recruit me to go to Holmdel and become a new department head of his in a basic research department. And they were cobbling together some people there. And so, here I was, this 34-year-old kid, and Bill was, I don't know, 10 years older than me. I like him. I did sports when I was in college, and in Bell Labs, I joined a softball team. And when I went to Holmdel, I started a softball team there, [laugh] and Bill Silfvast was our pitcher. When I was at Berkeley, I was also on a softball team. That was a good softball team. and we won the league championship two years in a row. One of our team members played for Cal when he was in college, so he was a serious baseball player. And also had a AA player on our team. I was the centerfielder.

Zierler:

Ah, you can run, that means.

Chu:

I could run, and believe it or not, I could hit. But yes, I could run. I was really good at picking up where the ball was going to go right as it was leaving the bat.

Zierler:

What was your initial project at Bell? What did you work on?

Chu:

There were two projects. Positronium with Allen Mills, and even before I showed up, I started to talk to him about doing a laser experiment. He was a positron expert. And Hyatt Gibbs got me interested in another project, another laser experiment. Phil Anderson had just gotten a Nobel Prize for his contributions to condensed matter physics and because of what he had done in pioneering how to apply quantum mechanics to disordered materials. For periodic materials, the quantum mechanics was used by Felix Bloch and others back in the late 20s. But no one knew how to use quantum mechanics to describe amorphous materials. The quantum mechanics of periodic materials crystalline quartz predict a very sharp onset in the absorption of light near the band edge. In amorphous materials, like glasses or fused quartz, there is no periodicity, and there must be a smearing of density of energy states. Anderson said, "Well, this is a little bit weird because you look at the absorption of fused quartz and crystalline quartz, and the optical absorption spectra both had sharp spectral features, so what's going on?"

So he developed a theory called Anderson localization that said that you have a difference between localized states and continuous states that's like a phase transition in the density of states, and so it gives you this very sharp transition. And he introduced a way of calculating based on summing all possible quantum paths, similar to Feynman’s path integral approach. Anderson localization was one of his contributions in condensed matter physics mentioned in his Nobel Prize citation. When he got the Nobel Prize, he said that the best test of Anderson localization was an experiment done by a Bell Labs experimentalist named Stan Geschwind, and that he would like to see more experiments to test localization. And it was a very clever experiment having to do with optical properties and energy transfer in impurities in ruby. Hyatt Gibbs said, "Well, he just got a Nobel Prize for this. He would like to get better evidence."

Stan Geschwind used a ruby laser, and by cooling the ruby laser, it would tune to one side of the ruby R1 absorption line. He saw a rapid drop in absorption that was interpreted as a sharp drop in the density of states that could interact optically with the light that was consistent with localization of energy transfer of excitons in the ruby lattice. Anderson thought that was a great experiment, also based the idea the energy transfer was due to short range exchange interactions by Bob Birgeneau who was at Bell Labs and then later, MIT. So Gibbs said, "I have a tunable dye laser, so we can tune to the other side of the line of the absorption line. If you see a similar drop-off, that would strengthen the interpretation of localization of excitation in ruby ." I said, "While it is not a novel experiment, but given the importance of the theory, let’s do it.”

We found that it wouldn't be a sharp drop-off, it was more gradual. And on the other side of the line, it looked very different. "OK, what to do? What's going on?" Stan Geschwind was still at Bell labs and was very helpful. I said, "Look, Stan, we're trying to replicate your experiment, and we're having difficulty. Help us out here." And he said, "OK, well, here are my samples." He's a good scientist and wanted to know what was going on. We discovered when we looked through his samples that the ruby powder samples were ground to dust and packed down, and the radiation was optically trapped. He was measuring an artifact. So I said, "OK. It's radiation trapped and this is not good, so ground the ruby powder to make much lower density samples. With more dilute samples, the drop-off become even more gradual. Stan was still help us, but he was disappointed.

Everybody was disappointed because the ruby experiment no longer looked like a good example of Anderson Localization. Then, Sam McCall, who was good friends with Hyatt Gibbs came up with a very clever suggestion. He knew that that the chromium impurity ions sit at two different lattice sites. When an external electric field is applied to local electric field at the lattice would shift the R1 line in opposite directions. Assuming that the population of the impurity ions occupies random lattice sties, in the presence of an electric field, all of the ions in the spectral line width of the laser at one site would be excited. The electric field is briefly turned off so that ions in the nearby different lattice sites could exchange energy. Ions at the different sites that are spectrally shifted when the field is on would be resonant with ions in the other nearby lattice sites. Energy transfer measured as a function of the time when the electric field is momentarily switched off would allow us to extract the near neighbor energy transfer rate.

What we were able to deduce is that the energy transfer was via long-range dipole-dipole energy transfer. Hence, the assumptions of Anderson localization did not apply since energy could never be localized. It is easy to see why. If the probability of transferring the excitation energy drops off as one over R³, the number of ions accessible to energy transfer increases as R³, so long-range energy is possible.

With our new direct near-neighbor measurements of energy transfer, we then looked in the literature for the evidence that led to the conclusion that the energy transfer was shorter range than dipole-dipole transfer. The evidence was based on rapid resonant energy transfer between excitations among single ion impurity sites before eventually transferring to fourth nearest neighbor pair states that act as energy traps. Energy transfer was deduced by looking at the intensity ratio of the R₁ and pair states.

We reviewed all of the earlier experiments and found that the evidence that ruled out dipole-dipole interactions and favored shorter range interactions such as quadrupole-quadrupole or exchange interactions were also plagued by radiation trapping, and only dilute measurements were considered, dipole-dipole exchange could not be ruled out. Also, an excited state of the trap states were nearly resonant with an excited single ion state that could resonantly enhance the energy transfer between a single ion and the trap state.

The sum of all our analysis of earlier experiments showed that the earlier experiments - after accounting for radiation trapping - were consistent with the dipole-dipole transfer we measured in a much more direct manner. Geschwind’s experimental test of Anderson Localization experiment was based a large body of work that turned out to be based on incorrect interpretations. The bottom line is that Anderson localization theory didn't even apply to the ruby system, and the calculation that Birgeneau concluded, that there was rapid energy transfer based on exchange was also incorrect. I was very diplomatic about our findings. I wrote him a letter saying, "Look, Bob, I don't think your calculation is right”, but we did not write a paper that said, "Birgeneau was wrong." He appreciated that we did not make a big deal out of the error, and he said, "You were very kind to me." In the end, my work on the energy transfer of ruby led to my first tenure offer.

In those early days at Bell Labs, I also got interested in two other areas. One of them was a beta decay experiment to see if the neutrino had mass. For example, in the beta decay of the neutron, the neutron decays into a proton, and electron and an electron antineutrino. And the energy spectrum of the electron and antineutrino have a continuum of kinetic energy density of states.

But if it the neutrino had mass, the high energy tail of the electron spectrum would not go smoothly to zero, would have a fall-off that would indicate a non-zero rest mass of the neutrino. The traditional way of measuring the distribution of electron kinetic energies is the traditional method of determining the upper limit to the neutrino mass. However, there were some experiments that suggested that maybe there was a little anomaly that suggest the neutrino could have mass. I got interested in this question because of the electroweak experiment I did for my thesis and post-doc work. In earlier beta decay experiments, there were concerns about so-called final state interactions between the daughter nucleus and the solid-state host material could mimic the drop-off in kinetic energy states that could be interpreted as a neutrino mass. So I said, "Wouldn't it be cool if you could take a gas of radioactive tritium in the gas state, where there are no complicated condensed matter final state interactions. The recoil of the daughter nuclei becomes very simple atomic kinetic recoils effects that can be calculated.

So I thought of this crazy idea, if the radioactive gas were to be confined with a very thin low Z membrane a couple hundred angstroms thick, the beta decay electrons wouldn't lose much energy going through the membrane, and the wouldn't distort the energy spectrum of the electrons.

I began to experiment with formvar, a polymer that's used to coat copper wire which gives the wire its brown coloring. It turns out if you dilute the polymer in a solution and put a drop of the polymer solution onto water, the drop spreads out over the surface of the water on a drop of oil on top of water. I found that you can make free standing films that are 100 angstroms thick that were an inch in diameter. I started making these films but got concerned that if the films leaked the radioactive gas would leak into the detector vacuum chamber and contaminate the detector And so, I finally decided it was too risky. But I was playing around for a few weeks making ultra-thin films.

In another quick exploratory effort, after the Anderson localization work I did, I was thinking of how to study the Mott transition, which is now also called the Mott-Hubbard transition. Mott considered a lattice of atoms that are initially separated so that they act as isolated atoms. He imagined squeezing hydrogen atoms closer and closer together. At some point, he predicted that the atoms would undergo a sudden phase transition from an insulator to a metal. There would be an equivalent phenomenon if one replaced atoms with excitons, bound states of an electron and a hole. Increasing the density of exciton “atoms” is done my increasing the optical excitation energy of the laser. By interfering two laser beams, you can make a periodic one-dimensional lattice of excitation. By changing the angle of excitation, the lattice spacing changes. If one then takes a third beam of light, it is possible to diffract light from this periodic diffraction grating. However, if the excitons undergo a Mott transition at some exciton density, the lattice would disappear, and so would the diffracted light.

I put together a picosecond laser system and used it to write transient gratings of periodic excitations. During this time at Bell Labs, I was drawn to laser experiments that could test quantum phase transitions in condensed matter physics, such as the Anderson localization, transition between localized excitations and a sudden transition to very mobile excitations. The Mott transition was a phase transition between atomic-like state of hydrogen and “metallic’ state where the electrons and holes would suddenly be able to move in the host lattice.

Another problem I got interested in was the discovery that if electrons are confined to form a two- dimensional system such as in a MOSFET (metal-oxide-semiconductor field effect transistor), held in a very high magnetic field and cold temperatures, the Hall resistance was found to have extraordinary precise quantized levels equal to Planck’s constant divided by the square of the charge of an electron. Von Klizing found that the resistance plateaus were repeatable to three to four decimal places. And some people at Bell Labs were reviewing the paper, and told him to go back and make even more precise measurements to see how repeatable with the resistance plateaus. Von Klizing found that the levels were quantized to better than six decimal places.

This is an amazing discovery since nothing in materials science and device physics can give measurements to this accuracy unless there is precision to so many decimal places. For this discovery, von Klitzing was awarded the Nobel Prize for the quantum Hall effect.

When the quantum Hall effect paper came out, the discovery led to an animated and extended discussion at Bell Labs. What was the underlying physics that was responsible for so much precision? There were about 150 Bell Lab scientists saying, “This is remarkable. What does it mean? What is responsible for all of this precision, and what else can we measure?" I was active in the discussions, and one of the other participants, Dan Tsui, came up to me after the session and said, “Steve, I didn't know you were interested in electron transport. Why don't we collaborate on this?” People wanted to collaborate with me by then. I said, "Sure," but thought about it, and the next day, and told him, "Well, I'm committed to improving the positronium measurement, and if I worked on this, it would be unfair to my other collaborators. I'd love to do it, but I can't." He said, "Oh, OK.” Dan Tsui and Horst Stormer ended up working together on the quantized hall effect.

And what was their first idea? They decided to take more measurements at higher magnetic fields and use much better devices where the electron mobility is much higher. The initial MOSFET devices that von Klizing used were made form with pretty crappy gallium arsenide material. Stormer was one of the inventors of a method to fabricate very high mobility electrons in gallium arsenide quantum wells. Dan and Horst discovered the fractional quantum Hall effect. Their discovery was a very big deal and it turned out that the underlying physics is very different. By then, Bob Laughlin, who was at Bell for two years as a postdoc, and then a permanent member of the technical staff was at Livermore, was developing the theory of the quantum Hall and fractional quantum Hall effects. The explanations of the quantum and fractional quantum Hall effects were very different. The fractional quantum Hall effect is due to fractionally charged quasiparticles that are neither bosons or fermions. In a three-dimensional world, all known particles are bosons or fermions. However, these quasiparticles are fundamentally different, but can exist only in a two-dimensional world. In a short period of time, the physics community recognized that the fractional quantum Hall effect was a very big deal." And I said to myself, “Shit. There goes a Nobel Prize.” I got another chance a few years later.

Zierler:

How close did you feel at Bell to academic scientists? Were you publishing in the same journals, going to the same conferences? That was all the same, essentially?

Chu:

Right. Giving talks at universities, conferences.

Zierler:

At what point at Bell did you get on the leadership track?

Chu:

Well, Bell had a tradition of getting very good scientists to become department heads. Because the way it's structured at Bell Labs, the department heads and directors actually made the funding decisions. Nobody at Bell actually had to apply for outside grants, whereas at IBM, it was a mixture of internal and external support. At Bell Labs, what they wanted or encouraged you to work on was essentially motivated from the ground up, from the principle investigators. So you had resources. If you had a good idea, you could go, and talk to them, and say, "I have this idea." And so, Allen Mills and I had done a big splash in positronium. We had this idea to make it even better. We went to Arno Penzias, the vice president in charge of research and a Nobel Laureate. He listened to us for two minutes and said, "OK, here's a quarter-million-dollars. Go." So that was how funding was done. And so, the great thing about Bell Labs is, it did not do peer review. It was “superior” review because the people making the funding decisions were the best scientists.

Now, how do you get the best scientists to take on these bureaucratic roles? You make it so that the overhead of bureaucracy is virtually nonexistent, and department heads and directors could still have a research career. And not only could you have a research career, Bell Labs demanded that you did have an active research career. The culture and premise was that the funding decisions are made by active researchers. Even as a director, you were expected to have a lab and were a practicing scientist working with your own hands. And even executive directors were still active, practicing scientists.

Early on in my career at Bell Labs, my director at the time was not thrilled by my decision to work on positronium. Once he said, "If you have come to talk about positronium, I don't want to hear about it. Just get out of my office." He and my department head didn't like me to work on the experiment because other scientists at Bell Labs had tried it and failed. And they thought it had become a dead end. It was an important enough problem that Bell Labs did support it, but after a couple of failed attempts, they said, "This is like throwing good money after bad. We don't want to do this." And after two years, my department head said, "Look, Steve, we have high hopes for you, but you're going to throw your career down the toilet because you're working on positronium. It's been two years, and it’s not working."

So I said to him, "Look, you're right. I have just a few more ideas. If they don’t work by next year, I'll quit and move onto something else." But the ideas worked, and I became a momentary hero. That same thing happened when I began to work on the laser cooling and trapping of atoms. Art Ashkin had a dream of trapping atoms with laser light. He started trapping micron-sized particles in 1970 and ’71, began to think of trapping atoms, and published a proposal to trap atoms in '78. They demonstrated that laser light could deflect atoms in an atomic beam. There were two types of forces: the so-called dipole force and the scattering force on atoms. After working on trapping atoms for several years, Art and his collaborators were nowhere close to trapping atoms. When I got to Holmdel and became a fellow department head, he tried to get me interested in atom trapping.

And I looked at what he was trying to do, and convinced myself that his approach of first trapping atoms and then cooling them was unlikely to work. He published an idea to introduce an atomic beam of atoms into a region with focused, counterpropagating laser beams in a geometry he used to trap a particle. He was hoping that the low-end Boltzmann tail of the atomic beam distribution would be cold enough to that his trap could capture them. They never tried to test the proposed configuration, but if they'd tried it, it wouldn't have had little chance of working. I realized the fast atoms in atomic beam would just knock the slow atoms they were trying to trap out of the trap. And so, I started thinking about how to avoid having fast atoms. My first idea was to create a sudden “puff” of atoms by using a pulsed laser to evaporate sodium atoms embedded in a frozen neon rare gas matrix. When the laser hit the solid source, it would evaporate a short puff of atoms, and there would be no other atoms coming from behind.

As I thought more about this scheme, I thought it would be too risky. I then independently discovered the Hänsch-Schawlow laser cooling scheme. I didn’t read their paper, which turned out to be a good thing. I first thought of a one-dimensional geometry of two, unfocused counterpropagating beams of light. In order to cool in all three dimensions, use three pairs of laser beams aligned along three orthogonal axes. By simple superposition, an atom with an arbitrary velocity will be cooled along all three axes. Hänsch and Schawlow said in their 2-3 page paper that one should “surround the atoms with light.” Since I didn’t read the paper, I landed on the right geometry of how to surround the atoms with light. I went to my director, Chuck Shank, and said, "Look, this laser cooling doesn’t need to first trap atoms. Also, if I calculate how long it will take for an atom to diffuse out the cooling region, it will confine the atoms for longer than any atom trap that's been proposed. It has to work."

He looked at me and said, "OK. You got positronium to work, so you earned the right to try this." Chuck had shut down the effort in the late 70s, and I was told that he told Art, John Bjorkholm and the others, “It’s time to just shut it all down. It was a good attempt, but you're not getting close to trapping atoms and it is time to move onto something else." This was after eight years of trapping and about six years of working with atoms. It was a very long time by Bell Labs standards. In 1984, Chuck also warned me, "Don't try to talk anyone else into doing it with you." I said, "OK."

In any case, I quickly scrounged a high-vacuum chamber that was on the “surplus list” and about to be donated to a university. I began to experiment with the “puff” atom source, and by this time, I was joined by a new postdoc, Leo Hollberg. He was getting interested in slowing and trapping atoms. Leo and Alex Cable (my spectacular technician) decided to forget about capturing the low velocity tail and use a frequency-swept laser beam counter-propagating against the pulse of atoms to do the initial slowing.

In less a year, the laser cooling idea, which I called “optical molasses,” worked like a champ. And the last two months, I said to John and Art, "Hey, this is working. You can join me." And then, the next year, we trapped atoms. But again, it was like positronium, in that I was following others, trying to get something to work where others had failed. I did things slightly differently. With atom trapping, I said, "Forget about trapping. Just get them cold. Once you get them cold, you can do a lot of other stuff." And that was the secret.

Zierler:

And scientifically, it makes more sense, cold and then trapping as opposed to trapping and then cold.

Chu:

Yeah, but the original approach was to follow the ion trappers. The ion trappers had very powerful forces to trap ions. Once trapped, they could be laser cooled with a single beam. As the ion oscillated in its trap, as the ion moved towards the oncoming stream of photons, the light would be tuned into resonance and the scattering force would slow the ion. When the ion was going the other way, it would be tuned out of resonance. Art’s approach was to do the same thing with neutral atoms. However, the optical forces that could be used to hold onto atoms was much weaker than the forces one could exert on ions.

Optical molasses was the secret, and it opened up everything else. Once cooled to very low temperatures, it was possible to use the feeble dipole force to trap atoms. So in a certain sense, I kind of got lucky. Ashkin tried to get me interested in doing what I thought was a dead-end project, and I said, “They were absolutely right to shut it down,” until I realized, if the order is reversed, trapping becomes much easier.

Zierler:

Well, I think that's a great place to cut it for today.

[End of Session 1]

[Beginning of Session 2]

Zierler:

OK, this is David Zierler, Oral Historian for the American Institute of Physics. It is June 22, 2021, and I am so happy to be back with Professor Steven Chu. Steve, it's great to see you. Thank you for joining me again.

Chu:

Hi, good to be here.

Zierler:

To start, we're going to pick right up in the 1986, 1987 area and your decision to join Stanford. How much of that was about you reading the writing on the wall for where Bell Labs was ultimately headed?

Chu:

Very little. Essentially none. Around 1986, '87, things were going swimmingly well. And a few universities, Stanford included, kept on asking whether I'd be interested in coming out of Bell Labs. They had asked several years ago. I said no. They asked my then post-doc, Leo Hollberg, who was from Colorado, and he said no, surprisingly. He wanted to go back to Boulder. Then, Ted Hänsch, by then a friend of mine, tried very hard to recruit me to come to Stanford, but got frustrated and left Stanford to take a Max Planck directorship in Munich. But what was remarkable is, he and Art Schawlow, who was Ted’s postdoctoral mentor, still continued to pursue me after Ted went to Munich. Ted remained loyal to Stanford, and he was especially loyal to Art Schawlow.

I had been at Bell Labs about eight and a half years. Very few people stayed on and retired at Bell Labs. There were a few people who did do that, but typically, people stayed there a decade, maybe a little longer. As you recall, I was supposed to have been on leave from Berkeley for two years. When Stanford began to solicit evaluation letters for my appointment, the Berkeley Physics Department asked, “Are you really serious about leaving Bell Labs?" And I said, "Yes, this time I am." And they said, "OK, well, we would like to make you an offer." And then, Harvard also called and wanted to make me an offer. I told Harvard I was predisposed to going back to the West Coast, but the dean of the Faculty of Arts and Sciences said, "Well, I'll fly down to New Jersey to visit to interest you into visiting Harvard." And I said, "There's no point in doing that," and agreed to visit Harvard.

All of a sudden, I had other universities indicating their interest, but I said, "No, three is enough." During this time, I did not anticipate the demise of Bell Labs. And so, why did I choose Stanford? I chose Stanford because it was the smallest department, it was the most fragile department. Both Harvard and especially Berkeley had bigger departments. They were all first-rate departments, certainly in the top five, but I thought I could make more of a difference at Stanford. My thesis advisor, Gene Commins, said, "Why do you want to go to Stanford and be a big fish in a small pond when you can go to Berkeley?" I said, "Well, I'm not so sure I'd be that big of a fish." But it was 60 faculty members versus 22. But they had a very small faculty, but a very good faculty. But 9 faculty at Stanford just retired or would retire in the next 10 years.

And so, as a riverboat gambler type of person, I thought I could make a big difference there, and went to Stanford. Also, I broke tradition. My work was both in very fundamental physics, but also, I had a lot of colleagues in the Applied Physics Department. I asked for a joint appointment and became the first joint appointment between the two departments. I even had friends at SLAC, but there was still a lot of animosity between SLAC and the Physics Department.

Zierler:

Yeah, from the Leonard Schiff days.

Chu:

That's right, it was during the Leonard Schiff days, but the people really stoking the fight were Bob Hofstadter and Felix Bloch. And the issue actually was a science issue. Bob and Felix wanted to build the next generation electron accelerator, but wanted Stanford to dictate who was allowed to use it. Pief Panofsky, Sid Drell, and others felt they should build an even bigger one that would require a lot of government support. With government money, the accelerator would become a “user facility,” and everybody had to submit a proposal to get access to beam time. In the end, the members of the Physics Department could not agree, and they fractured from the department. Pief Panofsky, Sid Drell and Burt Richter - at the time he was a young assistant professor – left the Department and formed the Stanford Linear Accelerator (SLAC).

The founding members of SLAC got kicked out of the physics department. It was a bitter divorce. Before the breakup, the faculty was very close. Felix Bloch, Sid Drell, the father of Persis Drell, used to play in a string quartet. They were talented musicians, but after SLAC was formed, the quartet broke up. Persis remembers going up to Felix when she was a young girl to say hello, but Felix ignored her, and just walked away. The Physics Department asked the defectors to return their department library keys.

Zierler:

I had not heard that one.

Chu:

It was really petty to take away their library keys. And when I joined the faculty, Sid knew me. Had I stayed at Berkeley, his daughter, Persis Drell, would've been my first graduate student. Remember, I spent my faculty setup money to build the laser system she used for her thesis. Sid called me up when he heard I was coming to Stanford, and says, "This is the first smart thing the Physics Department has done in 25 years." And what's really funny is, I was friends with him and Bill Little in the physics department, who was also of that generation. I invited them both over for a dinner, and in this dinner, they started arguing with each other about whose was a fault over breakup that occurred 25 years earlier.

Going back to my decision to come to Stanford, my life would've been different for sure had I gone to Berkeley or Harvard, but I felt it was a good decision. I was able to bring my laser cooling apparatus and lasers with me, so I got a very fast start at Stanford. I hired my first bunch of graduate students and was off to the races.

Zierler:

Did you take this as an opportunity to change up your research agenda? Or was your inclination to continue doing what you were doing at Bell Labs, just at Stanford with new colleagues and new resources?

Chu:

Both. When I was at Bell, Art Ashkin found he could trap bacteria and organelles within yeast and other things using the optical tweezers trap. We were trapping atoms, I said to Art while I was at Bell Labs, "I'm going to try to trap individual molecules. If you can glue little polystyrene spheres to a single molecule, you can make measurements with that." And so, in 1988, '89, I found a MD/PhD student, Steve Kron, who was willing to teach me how to use biochemical methods to glue DNA to a polystyrene sphere. I'll skip the details and just mention that Steve Kron didn’t tell his thesis advisor he was moonlighting with me, teaching me rudimentary biochemistry to attach a polystyrene bead to the end of a long DNA molecule. In the beginning, I didn’t know what a pipette was, or anything about biochemistry.

While I was learning these methods, I had brought two atom trapping vacuum chambers from Bell Labs. I and my first students reassembled them quickly. The first chamber was used to demonstrate optical molasses, then the optical tweezers trap, and then the magneto optic trap, which became the workhorses in the entire field. And shortly after arriving at Stanford, Bill Phillips's group discovered that the temperatures in optical molasses were much colder than I reported. In the first replication of my experiments everybody else reported comparable temperatures. I was overly influenced by the theory describing laser cooling in a two-level atom. Bill Phillips’ group did the first experiments that showed that the atoms cooled in optical molasses were much colder.

The news of their observation broke in '87, '88. By that time, I was at Stanford. We repeated the experiments much more carefully than we did the first time. Carl Wieman did the same, the French group did the same, and they all found the temperature was below the theoretically predicted minimum temperature. The theoretical minimum was based on modeling an atom with a single ground and excited state. The theory of a two-level atom used the full QED (quantum electrodynamic) theory, but it was for a simplified atom. And I remember that summer, after the groups had confirmed the lower temperatures, similar low temperatures were seen in sodium by Bill Phillips’s group, and my group. I think the French group led by Claude Cohen-Tannoudji and Carl Wieman's group cooled cesium. In the summer of 1988, there was a low temperature summer conference where Claude Cohen-Tannoudji and I were invited to give the talks on laser cooling.

And we met during lunchtime, and we compared what we knew about the lower temperature measurements, but at the time, neither of us knew understood the reason for the cold temperatures. We know it had to do with the multiple levels in the ground and excited states, chatted about it, and then went our separate ways after the end of the conference. And my next stop was in Europe, and my next stop was in Munich, Germany where I visited Ted Hänsch. I told him it was likely due to optical pumping. Ted suggested I read about optical pumping in the university library. As I began to read about optical pumping, I was getting nervous. The French group was the master of optical pumping, beginning with Alfred Kastler, who received a Nobel Prize for his work on optical pumping. And Claude Tannoudji was Kastler's student. In my reading, I learned there were so-called “Cohen-Tannoudji states.”

And I said, "Oh, jeez. I don't know if I'm going to think of the explanation." [laugh] But then, I was in another conference, and listening to another talk. All of a sudden, one of the speakers said something that reminded me of a very intuitive model I had of how atoms interact with light. The person said, "Well, the electric field polarizes the atom and its electron cloud oscillated like this …” I had known how the light field distorts the electron cloud, of course, because that was the basis of the optical trap. But now, I'm thinking in the context of optical pumping what came to my mind very quickly was a kind of mechanical model of how this cooling effect would occur.

The laser cooled atoms had multiple ground and the excited state. Both Claude and I realized the explanation had to be due to the Zeeman sublevels of the same hyperfine states since the hyperfine splitting of cesium and sodium were very different: cesium was split by 9.2 gigahertz and sodium had a 1.4 gigahertz splitting. However, the similarities and the degree of cooling below the two-level system were about the same. Hence, we both knew that the effect was likely be due to the multiple states in the same Zeman manifold. If an atom absorbs a circularized polarized photon, the circularized polarized light has one unit of angular momentum, so it changes the angular momentum of the atom from, let's say, a -1 angular momentum state to an excited state with zero angular momentum. When the atom returns back to the ground state manifold, the distribution of ground states is shifted toward higher angular momentum states.

The naive mechanical picture I formulated was that the repeated excitations would be orienting electron cloud to oscillate in the direction of the driving electric field. The optical field that is most strongly coupled to the atom is in the most optically pumped state. The stronger the coupling, the bigger the light shift, which lowers the energy of the ground state. I then imagined this optically pumped at moving into a region with different polarized light. I know the configuration of optical molasses beams was that each set of counterpropagating beams were linearly polarized, but the polarizations were mutually orthogonal. This led to a standing wave light field where the polarization states varied spatially. If an atom which has been optically pumped into a low-lying state in one region of space moves into a region of space with opposite polarization, its light shifted state is higher in energy. The energy has to come from somewhere, and the only other source is the kinetic energy of the atom. However, as the atom moves into this new region, it is being optically pumped into a lower energy state.

So in the end, think of the electron cloud blob of the atom trying to follow the changing polarization state of the optical field. It sounds like a pretty stupid mechanical model of how atoms interact with light, but even before laser cooling and for the rest of my career, I tried to remind people that the classical picture of how an electrical field distorts the electric charge of an atomic cloud is a pretty good picture of what really happens. Of course, because of quantum mechanics, you don't see this continuous electric field being generated, you see this quantum jump.

That's the peculiarity of quantum mechanics. If you looked at an oscillating electron cloud, classically, you would see the oscillation decaying gradually. In quantum mechanics, the decaying electron cloud distortion is related to the probability that the atom is in the excited or ground state. In reality, what we observe is a quantum jump, while the actual calculation has the decaying oscillation look classical. I remember Dave Wineland was in the audience at this conference. He asked after the session, "What happened? Your head went down, you started scribbling like mad, and you stopped paying attention to the rest of this session." And I said, "I think I figured it out how laser cooling really works."

My next stop was in Paris at the International Atomic Physics Conference. I met Jean Dalibard, and he said, "Steve, we've figured it out. We now understand why the temperature's so low." And I said, "I did, too." He asks, "What did you think is going on?" So I described it. It’s an optical polarization effect. The optical field orients the atom to enter into its lowest energy state in that region of space, but if it moves into another region of space, that Zeeman sublevel is in a higher energy state. The French had invented a very clever term: they called it “Sisyphus cooling,” which is masterful. I called the effect “polarization gradient cooling,” but it was the same physics. The atoms is in a low energy state in one region of space, but as it travels into another region, it is climbing up an energy hill. Once there, it finds that optical pumping is putting the atom back into its low energy state. It works just like the legend of Sisyphus, who was condemned to be forever pushing a boulder up a hill, only to find himself at the bottom of the hills has he nears the top. The atoms is always losing energy, going from one polarization region of space to another.

Jean Dalibard and I agreed, yes, it was the same explanation, and we were very happy. And they allowed me to squeeze in a last minute short talk. At the conference, Claude was already scheduled to give a summary talk, and he mostly talked about the new cooling mechanism. After the conference, a special edition of the Journal of the Optical Society was to be devoted to laser cooling and trapping. The two editors were Carl Wieman and myself. They sent in their manuscript, while I was working my manuscript, and these were the first archival publications of this cooling effect. Our articles were very different. I certainly didn't peek at what they were saying. They were doing very elegant quantum mechanics; they modeled systems of the two-level ground state and three-level excited states that laid bare the essential quantum mechanics.

I and my graduate students approached the problem in two ways. I wrote the first part of the paper with my very intuitive oscillating field model with a quasi-empirical classical model of how the “torque” of the driving electric cools the atom. While it's very intuitive, it was not hardcore quantum mechanics. But the other part of the paper was really hardcore quantum mechanics. Instead of a model system, we just used the energy levels of the sodium atom and solved the Optical Block equations. That was a plug and chug calculation that automatically includes the changing polarization states. The Optical Block solution was a quantitative prediction of how big the cooling effect will be.

Another project my group worked on used the other vacuum chamber that was designed at Bell Labs. The only application using laser-cooled atoms was that I knew when I started the cooling work was that the technology would make a better atomic clock. When I was at Bell Labs, I knew the atoms were so cold, that if the optical molasses light were turned off, they would drop to the bottom of the vacuum chamber. While at Bell Labs, I designed a new vacuum chamber designed to cool atoms in a magneto optical trap. Once cold, the plan was to push them upwards. The cloud of atoms go up in an arc and come back down. On the way up the idea was to put the atoms into a superposition of its ground and excited states with a pulsed electromagnetic field. In this superposition state, the quantum phase would oscillate at the energy difference of the two states. On the way down, if the electromagnetic field is pulsed on again and the phase of the driving field is in phase with the phase of the atom, the atom can be put into the excited state with 100% probability. If the phase of the electromagnetic field is 180 degrees out of phase, the atom would end up in the ground state.

So this is called Ramsey's separated oscillatory field method that earned Norman Ramsey a Nobel Prize because it allowed atomic clocks to become very precise time standards because it allowed the quantum measurement time to be increased by more than a 100 fold. When Norman Ramsey has this idea in 1949, and in the early 1950s, a professor at MIT, Zacharias, thought, "Why not take a beam of atoms and point them upward? Most of the atoms are traveling at the speed of a supersonic jet plane, and will just hit the top of the vacuum can. However, he thought that the very low energy Boltzmann tail, the really atoms would turn around due to gravity and re-enter the microwave cavity that used to initially put the atom into it superposition state. So Zacharias assigned a graduate student to demonstrate what he called an atomic fountain. I remember Norman Ramsey telling me, "After I heard of Zacharias’ idea, I said to myself, what a great idea, and felt scooped."

In the end, the poor graduate student assigned to this experiment couldn't get it to work because the very slow atoms going upward would be knocked out of the way by lots of fast atoms coming from behind. He was unable to detect slow atoms coming down because the fast ones knocked them out of the way. That graduate student, by the way, experimentally showed that the slow atoms were knocked out by the many more hot atoms. He survived this failure, and eventually got his PhD. His name is Rai Weiss. He went on to get a Nobel Prize for gravity wave interferometry. In the end, he did fine, but for a while it was rough sledding.

When I was a graduate student, I learned about this story as part of the oral history of atomic beams. I am not sure there was a publication on why the Zacharias fountain never worked. In any case, the reason I chose to develop a puff-source of atoms was that I did not want fast atoms to knock the laser cooled atoms out of the way. Once the laser-heated pellet cools down, the atom source turns off. One of the lessons of the Zacharias failure, was burned into my brain, was "Don't have a continuous beam of atoms Whatever you do, that beam cannot be intercepting where you're planning to cool and trap atoms." The same logic led me to use a ultra-high vacuum chamber to trap the atoms. I did not want residual gas atoms to knock the cold atoms out of the cooling or trapping region.

No surprise, but the atomic fountain worked. We then put a microwave cavity into the chamber that allowed use to induce transitions between the hyperfine levels of sodium. That also worked beautifully, and again it was off to the races. By then, the French group, led by Claude Cohen-Tannoudji, had also started to collaborate with their standards people. They made the first cesium fountain. We did it in sodium, but since the time standard was based on the cesium hyperfine splitting, we made a cesium fountain. I did not have a group devoted to precision measurements like a Bureau of Standards. In France, they have a group of groups that include professional scientists as well as graduate students and postdocs. In this way the French can assemble really first-rate groups. In the early days I was laser cooling and trapping, my group worked in groups of one or two people. We decided to finesse all of the precision microwave technology by scrounging a used cesium clock. Hewlett-Packard made the best commercial cesium beam clocks. Their machine actually fits in a 19-inch rack. It was a beautifully engineered and machined microwave cavity, and their clocks were the de facto time standard. Even though the National Bureau of Standards used a much longer separated oscillatory field apparatus, alongside of the primary standard, they ran about a half a dozen of the Hewlett Packard clocks as comparison clocks.

And so, why am I telling you this? I'm telling you this because I wasn’t a microwave expert. I called up a friend of mine at Hewlett-Packard Labs, Len Cutler. HP Labs was very close to Stanford. I said, "Len, we want to make a cesium clock fountain. Do you have any surplus guts of a cesium clock?” And he said, "Sure," and he gave us the copper cavity and the vacuum microwave feed throughs to power the cavity. And again, we put the microwave cavity into a new MOT chamber designed to collect billions of atoms. The laser cooled atoms were launched through the microwave cavity hole, went up, and came back down through the cavity again. The difference was the heart of the microwave system was this beautifully constructed Hewlett-Packard atomic clock cavity with all the needed microwave stuff to get the microwaves inside our vacuum chamber.

Our work was the first cesium atomic fountain whose short term microwave clock stability passed the short-term stability of the very long National Bureau of Standards clock because we had such long measurement time. Our work was followed quickly by a German group and a French group that were part of their national time standards groups. Remarkably, the time of our first atomic fountain measurement of the sodium hyperfine energy levels in 1989 to the time the atomic clock frequency standards groups switched to atomic fountain clocks was only seven years.

In 1991, the first atom interferometers were demonstrated. Historically, the first atom interferometer experiments were done by using a direct analogy with optics. A German group led by Jurgen Mlynek showed that an atomic beam that went through two narrow microfabricated slits showed diffraction analogous to the Young’s double slit diffraction of light. A very well collimated atomic beam has a very slow velocity spread in the direction orthogonal to the propagation direction. The very low velocity spread means that the quantum mechanical wavelength of the atoms increases to the point where diffraction effects could be seen using a double slit. This was the first experiment to observe quantum interference of atom waves. In the same issue of Physical Review Letters, an MIT group led by Dave Pritchard used a standing wave of light to exert optical forces on a well-collimated beam of atoms. The standing wave creates a periodic grading, and they showed that three sequential light gratings creates an atom interferometer.

And then, three months later, we published our atom interferometer result. Our approach was totally different. Instead of using optical analogies of atom waves diffracting off of periodic gratings, we considered what would happen if an atomic fountain of atoms were exposed to a pulse of light comprised of two counterpropagating laser beams. We tuned the light so that the frequency difference of the two beams was resonant to the ground state hyperfine splitting of the atoms in the fountain.

Initially, we optically pumped the atoms to be in one of the hyperfine states. If the laser beams were tuned near but not on an excited state resonance, one can think of the atom as making a virtual transition from the ground to the excited state and back down to the ground state. In this virtual transition, the photon from one beam imparts a momentum impulse to the atom. The other beam can be tough to stimulate the atom to return to the other hyperfine ground state. The stimulated emission adds another momentum kick in the same direction as the excitation pulse. Thus, two units of photon momentum are transferred from the laser field to each atom. The second beam of light is derived from the first beam by using a electrooptic modulator to create microwave sidebands on the original light beam. The frequency of the initial laser beam did not have to be well controlled the laser was tuned far away from any atomic resonance. On the other hand, the frequency difference between the laser beams was due to a very precise microwave generator used to put radio frequency sidebands on the light.

The difference between our interferometer, which followed three months after the first two atom interference experiments, was that we were able to measure atom wave interference to six decimal places digits rigt out of the gate. One year later, we got eight digit precision in a measurement of the acceleration on an atom due to gravity. This was all happening in 1991 and ’92. This method still remains the absolute most precise way to do any atom interferometry.

Atom interferometry is now one of the most precise measurement tools we have today. For example, another of my graduate students used the atom interferometer to compare the acceleration due to gravity of a freely falling macroscopic object, a corner cube reflector, to freely falling atoms in an interferometer. The agreement was good to one part in ten billion.

Since those early atom interferometer days, the graduate students and postdocs who worked in my group are now the world leaders in atom interferometry. For example, Mark Kasevich, the first student to work on the atom interferometer and one of his former students are both professors at Stanford are now working on a ten meter tall fountain in the basement of the Physics department to test the General Theory of Relativity. They are also testing and its foundational assumption, the equivalence principle. A 100 meter tall atom interferometer apparatus is also being constructed at Fermilab to search for the presence of ultralight dark matter particles, and to detect gravitational waves of lower frequency than previously detected based on laser interferometers. This journey all started back then in the late 80s and early 90s.

Meanwhile, the biology-side of what I began doing at Stanford was based on optical tweezers which was cooking along in a very amateurish way. I got it to work working with Steve Kron, started giving talks about what I was doing, then got a couple of my students; one undergraduate student, Steve Quake, and two graduate students, Tom Perkins and Doug Smith. The method I developed with Steve Kron wasn't reliable because the protocol we used was based on labeling DNA with biotin and attaching them to polystyrene spheres coating with a molecule called streptavidin. I didn’t realize that the method we used would allow biotin to go into solution. Once this happened, they would use up all the avidin binding sites. The difference is because I was moonlighting in the evening with the MD/PhD student, and we worked very fast. And so, the difference is, a graduate student typically will work until 6 or 7, maybe 8 pm, then it's quitting time. The next day, they pick up the experiment again, whereas I was just trying to rush to do the whole thing in a couple hours. And so, the slow off rates of biotin were not fatal. It took Tom and Doug about a half year to figure out what was going on. Because I was too green, and I didn't know enough to know to help them. I just knew, "Hey, I got it to work. What's the problem?"

But we first started doing these things, thinking I was going to measure forces between molecules. I started also helping Jim Spudich, a professor in the Biochemistry Department at Stanford, and a professor on leave, Bob Simmons from King’s College. They were both very distinguished biochemists who wanted to use optical tweezers to measure the forces that molecules exert on other molecules.

The system Jim Spudich was studying was molecular motor was myosin. Myosin is a little molecule that attaches to actin, a biopolymer rod-shaped molecule. And when actin hydrolyzes ATP, it generates a force that pulls on the myosin filament. Many actin molecules attached to strands of myosin generate the molecular forces in all muscle contraction. In order to use optical tweezers to measure the forces, we couldn’t simply put an actin filament onto a bed of myosin heads that way Jim Spudich visualized the movement of acting filaments in a microscope. I suggested we can measure the molecular forces by placing a lot of the myosin molecules on the surface of a polystyrene sphere. The sphere served as a spacer between the microscope cover slip and the actin filament. When two beads were attached to actin filament, the optical tweezers could be used to place the filament on top of the sphere. Once in place, if the myosin molecules pulled one way, a feedback circuit is use so that the optical tweezer pulls the other was to keep the filament immobile. Since the optical tweezer is pulling the other way, and we can calibrate the optical tweezer force, you can actually measure the force as it occurs with the optical tweezer. If you hold it lightly, you can see the filament move, so we could image the length of each actin step. The optical tweezers kept the filament engaged on the actin, so repeated measurements could be done. The first few papers paper describing what we did were published while the optical tweezers set up was on the second floor of the Varian Physics building.

Our goal was to see a single actin move the myosin with a single molecular stroke, and to measure the strength of the molecular force. However, the microscope set up was vibrating too much on the second floor of Varian. We put all sorts of damping on the microscope, but none of it was successful and finally, the experiment was moved it to a basement of another building which had much less vibration. Also, we used an inverted microscope instead of the original microscope. And once that happened, the single molecular forces could be resolved.

Meanwhile the optical manipulation of DNA was succeeding. My original intent was to examine how enzymes moved along DNA. However, once we were able to visualize DNA stretched out with optical tweezers, I saw it relax like a rubber band. At the time, I didn't know any polymer physics, but, "Holy cow, that's kind of neat. Why does it act like a rubber band?" And so, I got sidetracked into doing DNA polymer experiments for the next ten years.

This was a very exciting time in the development of optical tweezers and biology and fundamental polymer physics. The DNA optical tweezers experiments allowed us to do a series of experiments testing very fundamental ideas in polymer physics. The single force measurements in actin-myosin system started the molecular motor studies in biology. Shortly thereafter, Steve Block did a similar sort of measurements on kinesin, and it was off to the races, beginning with Spudich, Simmons, and Block. Soon Ron Vale and others used this technique to method study other molecular motors.

I entered into polymer physics not knowing anything about polymer physics. Early on, I gave a talk at Bell Labs around 1990-91 describing our results. And a colleague of mine there, who's a theoretical physicist/chemist polymer expert, Ron Larson, got excited and said "This is great. I've got just the set of experiments for you." I said, "What are they?" He said, "You know, Pierre de Gennes wrote this book on polymer physics. Just go through it, chapter by chapter and see if he's right." I said, "Ron, he just got a Nobel Prize for his work on polymer physics. Why should I do this?" He answered, "Because we don't know if they are right." To my amusement, his book became the outline of our experimental program.

Steve Quake, a very bright undergraduate Stanford student, and I started reading de Gennes's book, and also a classic textbook on polymer physics by Doi and Edwards. We, plus Tom Perkins and Doug Smith found we only needed to read the first three chapters of Doi and Edwards and skim through de Gennes to design the beginning of an experimental program. For the next ten years, that formed the basis of what we did. It was crazy period, and we were publishing an article in Science literally every nine or ten months for about 6 years. Then it got really hard because we started testing some of his ideas that were really hard to achieve experimentally. At first, de Gennes was thrilled. I was at a polymer conference giving a talk and showing movies of DNA relaxing in polymer solutions, testing whether a normal-mode description of polymer dynamics was sufficient to describe what ultimately had to be a non-linear system. Once, I was describing our work in a polymer conference, and someone in the audience asked de Gennes, "Pierre-G, what do you think of this?" He says, "Never in my life did I believe you could do these things."

He was a big fan, but also a harsh critic. One of our papers described how DNA stretches in a microfluidic elongational flow cell comprised of two opposing inlet channels and two orthogonal outlet channels. If a polymer moves close to the central so-called “stagnation point,” it spends a lot of time here, and begins to stretch out – elongate – in this flow. What we observed was that the polymers would enter into this region as random, jumbled coil mess. As they elongated, they would stretch out , but they took different pathways, assumed different morphologies, as they stretched out map. When our paper was published, de Gennes was asked to write a commentary. He said, "This cannot be. This is a very simple molecular system, and how can identical molecules act as individuals?" He dubbed the phenomena "molecular individualism". In his comment, he speculated that there must be something wrong with our experiment, and perhaps the DNA molecules were not really identical.

When George Gamow suggested that the universe might have started with an initial explosion, The critics named it the Big Bang Theory, and the name stuck. Our discovery was trivial compared to how the Universe began but nevertheless could identical starting conditions of simple molecular systems lead to the diversity of outcomes. We responded by doing another experiment. This time, we took a single molecule, we arranged the flow so we could keep it trapped near the stagnation point by feeding back on the balance of flow in and out of the flow cell. We then we turned on elongation and took movies of how it stretched out. We then let the molecule relaxed and starched it again. After many dozens of times using the same molecule, we could reproduce the variety of pathways to elongation we saw in the original experiment.

We also did a numerical experiment of how the molecules were expected to elongate. Yes, it was the same molecule, starting in exactly the same flow conditions, but there were many microscopic configurations of a long molecule in its initial configuration. Thus, there is a randomness in its exact starting configuration. When we numerically simulated a polymer starting in a random coil, it unraveled in the elongational flow along different pathways. So with the simulations and the experiment using the same molecule, the matter was settled. I joked with my students at the time, "Don't get mad. Just get even." In any case, over the years, de Gennes and I became friends.

During the time we were doing the single molecule experiments, we were inventing several new ways of laser cooling such as Raman sideband cooling, and new ways of creating what we called large area atom interferometers. By this time, I had a group of 20-25 people, but I was having trouble getting the atomic physicists to pay attention to the biologists and polymer people, and the biology people to pay attention to the atomic physicists. Mark Kasevich was still in the group at the time, and he thought the biology was not hardcore science. The biologists, who were trained as physicists, some of whom had undergraduate degrees in physics, didn't want to hear about the details of optical Block equations and atomic coherences.

And so, it was hard for me to keep the groups together. The biophysicists were beginning to act more like biologists, and the physicists didn't want to learn all the new vocabulary in biology. When Xiaowei Zuang joined my group to move into biology, she claimed she knew nothing about DNA. She claimed she heard the name “DNA,” that that was about it. She did her thesis in condensed matter physics, and nonlinear effects at the interface of surfaces with Ron Shen at Berkeley. The person who became her future husband was doing single molecule polymer physics in my group.

Zierler:

How did all these ideas formalize into Bio-X? When did all that start?

Chu:

The idea of Bio-X started in 1997. The University of Chicago was thinking of starting a new institute that would bring together biological sciences with physical sciences. They had very good physics and chemistry, a good medical school, but were weaker in the biological sciences and had no engineering. They were trying to recruit me to become the director of this new institute. I was intrigued and had a lot of respect for the University of Chicago. It's a really excellent school. I have a lot of respect for a lot of reasons, it regarded it as consider to be a truly “academic” school. They don't do sports. There was a list of what the best party schools in the country, and the University of Chicago was ranked dead last in a 1993 survey of the most “fun schools” in the US. A really no-nonsense intellectual school, and I seriously considered going to Chicago.

While it was very enticing, I had recently gotten divorced, and my kids were spending half the time with their mother, half the time with me. I asked them, "Would you be willing to move to Chicago?" And they said, "No, our friends are over here." If they don't want to go, and their mother's staying in California, it meant I couldn’t move. After the dust settled, someone told me how the physics department was figuring out how to entice me to how come someone asked, "This is all fine and good, but what happens if he gets the Nobel Prize?" And there was this silence in the room. Because they said, "If he gets the Nobel Prize, Stanford's going to really work hard to keep him." In the fall of 1997, they announced my Nobel Prize.

In my Chicago visit in 1998, one of the faculty members told me, "We didn't even think you'd show up for an interview." But what they were trying to do was intriguing. So then, I got back to Stanford. I said to my kids, "If you aren't coming, I can't go." I explained that to Chicago, and they understood. I visited with Jean and spent three days there, looking at houses, and we seriously considered moving.

After I turned them down, I told myself, "What they're trying to do makes a lot of sense," but they were going to recruit a lot of people around this institute. But I looked at Stanford, and we had many of the right people and a medical school and an engineering school. So I got Jim Spudich in Biochemistry, Dick Zare in Chemistry, Lucy Shapiro in Genetics, and myself to meet on a Saturday in my office to talk about starting sometime like what the University of Chicago was trying to do. By this time, I was collaborating with Spudich and Dan Herschlag and a few others. And there was a feeling that the developing technologies based on physical methods would open up new capabilities. Our enthusiasm was before single molecule fluorescence, single molecule FRET and super resolution microscopy were invented. But already, optical tweezers was gaining a foothold. We all felt that "This is going to lead to great discoveries. " I said "We have an engineering school, biological sciences, chemistry, physics and a medical school all within a half block of each other. We wrote a white paper that circulated among us for a couple days, and then sent it to the provost and the president. And within three or four days, they read our five or six page description and said they will support it. It was that simple. We didn't bother showing to our department heads or deans; we just sent it to directly to the president and provost of Stanford.

Gerhard Capser was the President and Condi Rice was the at Stanford at the time. She then took a leave of absence to go work for Bush 2, and John Hennessy took her place. And Hennessy was also enthusiastic about Bio-X (where “X” could stand for anything) and was good friends with a guy named Jim Clark, who made a fortune as the co-founder of Silicon Graphics and Netscape. Jim Clark fell in love with the idea and pledged $160 million to fund the initiative. We were off to the races. Within a half year, another roughly $150 million was raised. From our meeting in the spring of 1998, a building and program was designed. People began to move in by 2002-2003. In 2013 we celebrated the tenth anniversary of Bio-X and the Clark Center.

While Bio-X was largely successful there were some growing pains. Partly, the three deans started getting into the implementation, and looking out after the schools they represented. We ideally wanted a strictly bottoms-up faculty initiative. Even so, what was successful was that the Clark Center became a means of increasing informal interactions among the faculty, especially within the building, but also as a hub for everything that cpould not fit into the building. There were seed grants, there were seminars in “plain English,” there were many things that helped magnify chance encounters and new collaborations across disciplines.

The whole premise was built on, "Let graduate students, post-docs, faculty members get together, discover what they're doing, and they can dream something up." So instead of top-down initiatives, we were marching in this direction. Bio-X became the model of a number of other multidisciplinary institutes within Stanford and around the world. It was a model of how to get people who normally don't talk to each other realize that they have common interests and could do things they couldn’t dream of doing alone. A biologist wouldn't have the background or inclination to make a new instrument, while a physicist or an engineer could get guidance on how to best apply the new tools. While things were well, I also got interested in climate change.

Zierler:

Before we go there, where were you when you got the call from Stockholm?

Chu:

I was at home. I was asleep. I was supposed to be attending a conference in Southern California. But I was too busy and decided not to go. The day before the Nobel call, Stanford Press called me up and said, "If you get a call from Stockholm, will you call us?" I said, "What?" "Just in case you get a Nobel Prize tomorrow." And I said, "What? Do you know something I don't know?" And they said, "No, we don't know anything you don't know. But you've been rumored for a couple years and the rumors are increasing … or something like that " And I said, "I'll be at home." That night, I didn’t sleep well. There was no phone call. So I said to myself, "Hm. Guess I'm not getting a Nobel Prize" and went back to sleep. About an hour later, I get this phone call, and the person on the phone asks, "What does it feel to win a Nobel Prize?"

And I said, "Who is this?" And he said, "I'm a reporter from the local TV station." And I said, "Well, I haven't gotten a phone call. So I don't know what it's like." So he says, "Oh my God, they must be trying to reach you now. I'll get off the line." The Stanford Press people told me to call them in case I got a call from Stockholm. I followed their instructions, called them and said, "I got this strange call from a reporter saying I got the Nobel Prize. Is that true?" And they said, "Yes, it is. It's on the internet." And I said, "Do you believe everything you hear on the internet?" And they said, "No, no, this is from the official Nobel web site." They said, "Don't do anything. We'll come on over, and we'll help you deal with the press. They came, set up a communications system and everything. It turned out that they had switched area codes, and where I was living on Stanford campus, my phone number was changed from the 415 area code to 650. The Nobel people were using my old area code and couldn't get a hold of me. I thought to myself, "This wouldn't have happened had they not broken up AT&T”, but that is another story" [laugh] By now it is 5 o'clock in the morning in October, and it's dark out. All of a sudden, TV camera crews show up and the front of our home on the Stanford campus is lit up. I imagined our neighbors peeking outside their windows seeing the bright lights and wondering if was a police drug raid.

Anyway, the Stanford people handled the many phone calls. At 7 am I called up my mother to tell her to say. "Hi, mom. I just got the Nobel Prize." She answered, "That's nice, but when are you coming to visit me next?" Several hours later, she says, "It's true. You did get a Nobel Prize. My friends told me. " I finally get an official call a couple hours later from the Nobel Prize committee after they finally figured out my phone number had changed. I asked a Swedish reporter who called me before the Nobel committee reached me, "I don't understand. The reporters could figure out how to call me." The person laughed and just said, "We have our ways." The reporters can be quite resourceful.

At the time, I was thinking while this was great news, it was not a complete surprise because rumors were swirling by then. I was not expecting the interest from the press. Whole bunch of people from China, Taiwan, Hong Kong, got on planes and were at Stanford the day after the announcement. There was a press conference the day of the announcement and another one the following day to accommodate all the overseas press who flew in. After a week or so, I went back to work thinking that is over and I can get back to work.

It wasn't until the night of the ceremony, when I was walking on stage, hearing this music, and you're looking at this opera house, that it finally hit me that getting a Nobel Prize was a really big deal. Before the Nobel ceremony, I had known Nobel Laureates before and after their Nobel Prize. They didn't get suddenly smarter. I'd known people who didn't get Nobel Prizes who were equally brilliant, made tremendous contributions to science and never got a Nobel Prize. But that night I realized it's different because the public views it differently.

Zierler:

Did you have a suspicion that all of the attention from the Nobel Prize could derail your research? And what steps did you take to prevent that from happening?

Chu:

Yes. I'd seen it happen with others. I've also seen Nobel Laureates start to talk about things that they didn't bother informing themselves about before pontificating = about a lot of things. And I said to myself, “I’m not going to do that. And I’m not going to let the publicity get hold of me.” I was 49 at the time, so I was middle aged. Not so old, not so young.

Zierler:

But still, real scientific work ahead of you.

Chu:

Yes. And I felt in 1997, that I was moving into other areas beginning with the optical tweezer work manipulating the DNA and other biological molecules. By then, we were developing single molecule FRET, (fluorescence resonance energy transfer), which measures the energy transfer between two molecules such as between a green and red fluorescent molecule. If the green molecule is excited and is sufficiently close to the red molecule, the oscillating dipole electric field of the excited molecule is able to resonantly transfer its energy to the red molecule. Once the energy is transferred, it cannot transfer back because oscillation energy immediately degrades to a lower energy. By measuring the ratios of the tow light intensities, you can measure separation distance to a precision of about one nanometer if the separation distance is about five nanometers, plus or minus a few nanometers. Thus, by just measuring the ratio of the two colors of emission, distances at the molecular scale can be measured with nanometer precision.

My group was not the first to demonstrate FRET between individual molecules, but we were the first group to get it to work on a surface. This was important because it meant that we look at immobilized molecules until the fluorescent molecules photobleached.

The first single molecule FRET experiment looked at a biomolecule that drifted into the imaging volume of a confocal microscope. The people who did the experiment then argued that the fluctuations in the fluorescence of the two FRET molecules were consistent with structural fluctuation of the biomolecule. We were able to show it was possible to tether and biomolecule to the surface of a microscope cover slip and induce structural changes in a triple helix of RNA that agreed with the FRET of many molecules in solution. Later we showed it was possible to look at proteins interacting with DNA near a surface did not interfere with their biological activity as well. These experiments made single molecule FRET not a very powerful biological tool. After we showed you can do this, that were able to experiment with more and more complex systems, such as the translation by the ribosome and transcription by RNA polymerase. At the time, I felt that single molecule FRET could be as important as our atom interferometry work.

By the time I got the Nobel Prize, we were still doing atom interferometry and riding that wave, but also started doing single molecule FRET experiments, and riding that wave as well. I thought the single molecule biology and polymer work was as important as the atomic physics work, and didn’t want to get derailed by getting a Nobel Prize.

I was still very excited about what I was doing and moving into totally different fields. In fact, in the early 90s, a high energy theoretical physicist colleague of mine at Stanford said, "There are some people in Sweden asking some questions about you because I think they're interested in finding out more about you. You shouldn't do biology." By then, I was towards biology, and asked him what was wrong with that. And he was Greek and appreciated how scientists behave. He said, "Because if you leave physics now, people may rewrite this history, and they won't remember your scent." It's like a dog peeing on all the fire hydrants and trees in their neighborhood to just remind the other dogs they are still there.

So he said, "Don't do the biology. Wait until after the Nobel Prize." I said, "No, I'm sorry, this is very exciting. I'm going to it anyway." I said, "If I get a Nobel Prize, that's great, but this is very exciting to me." And so, after the Nobel Prize, for a year or so, you are on the lecture, and after that I thought the attention would subside, but it didn't. Also, afterwards, and especially in the early 2000s, and by 2004 or so, I started getting more concerned about climate change, I started talking about climate change as well as biology and physics. That shift also put me more in the public light than if I had just remained a scientist.

Zierler:

Did you see the directorship at Berkeley Lab as an opportunity to merge all these interests? Was that part of your decision-making?

Chu:

No, I considered joining the Berkeley Lab mostly because of climate change. I was very happy with my research, which was going great. And in 2004, my former boss at Bell Labs was director of LBNL, and also Burt Richter said, "They're looking for a new director. You would be perfect." I told Burt, "Don't bother nominating me. I'm not interested since my research is going well." Some people at Berkeley were also interested in getting me interested in considering the job as well. Finally, Chuck Shank called me up and said, "Look, we're very interested in you. Why don't you come take a look? If there's a 5% chance you'll take the job if offered, that's all we ask for. If it's less than that, we don't want to waste your time or our time." So I went and looked around. He gave me a tour. When I was a graduate student and post-doc at Berkeley, I was also a member of Berkeley Lab, and when I became an assistant professor, I remained a member of the Lab.

And then, I began to think, "This is a very distinguished laboratory. A whole bunch of Nobel Laureates in its history, but a whole bunch more, roughly 30 at the time, started their science careers as Berkeley Lab members went on to receive Nobel Prizes. Tom Cech, who got a Nobel Prize for his work in biology/chemistry was also a Lab member. So I said to myself, "Here I am giving talks about climate change, and the Berkeley Lab is Department of Energy National Lab. A very, very distinguished Lab and many of its staff scientists were also faculty members at Berkeley. If I can get them interested in thinking about what they can contribute in terms of science and technological solutions the climate problem, that would be far better than what I could do by just talking about it." I wasn't doing climate or energy research at the time, but I was saying, "Hey, maybe these people are right. There are some real risks involved in using fossil fuels."

I felt by 2002, 2004, it wasn't really super convincing that all the bad things that were being predicted would happen. But as I looked more into it and started reading more. I thought to myself, "They may have something here. Instead of just talking about it, here's an opportunity to have this great National Lab adjacent to Berkeley." When I became director of the Lab, I started talking about energy, climate, things like that. I had a bunch of friends there, and they said, "Well, we don't know much about energy and climate." I answered, "Neither do I, but we can teach ourselves." We started to meet where half a dozen of us would meet for an hour or an hour and a half every week or so. The group included Paul Alivisatos in Chemistry, Alex Zettl in Physics, a bunch of others in physics and chemistry mostly. Jay Keasling in Chemical Engineering had just gotten a Gates Foundation grant to use microbes to make an antimalarial drug called artemisinin. His work was a big success, so I asked Jay, "What are you going to do next?" He said, "I'm going to see if I can use synthetic biology to help treat another disease." And I said, "Why don't you see if you can use synthetic biology to manufacture biofuels?"

We also had “teach-ins,” to self-educate ourselves, and we invested in efforts to capture the imagination of the Berkeley Lab scientists and the Berkeley faculty, "Maybe we can do something in research that would lead to better solutions." Due to these efforts, we were able to get a big BP grant for half a billion dollars over ten years to do research in biofuels. BP wasn't even going to ask Berkeley and Berkeley Lab to make a bid. The favorites were MIT, Illinois, and King's College, London. When they heard we were looking at synthetic biology applications of biofuels, BP invited us to submit a proposal. We started looking at biofuels before we knew there was going to be a lot of money invested in this area. In those days, energy research was not as fashionable as it is today, but I thought there should be more money invested in this type of research.

So I gave a lot of talks, trying to inspire people, saying, "Look, we're going to need solutions. But in the process of looking for solutions, there's going to be great science to be had, and there will be at least a couple Nobel Prizes that will come out of this. The solutions were going to be a mixture of science, engineering, innovation, everything." And so far, there are a couple Nobel Prizes coming out of this. Blue LEDs and lithium ion batteries so far. There will be a couple more because the science solutions we need have to transform the world. So that's primarily why I went. Berkeley became a center for energy research in novel applications of solar energy and in biology solutions. The Berkeley Lab still operates JBEI, the Joint Bio-Energy Institute. I just gave a keynote talk at their annual meeting on new opportunities for biology to develop new pathways for energy and more sustainable agriculture.

Ultimately, biofuels solutions are needed to replace diesel and jet fuel, but it is very hard to compete with oil at $60 or $80 a barrel. The initial euphoria calmed down. Optimizing stable new metabolic pathways in microbes was harder than anticipated, but the technology is maturing. We know a lot more now. We have new methods, like the Crisper-CAS methods, machine learning and robotics to speed the optimization and reproducibility of synthetic biology. Eventually, I believe biotechnology will help us get off of fossil-based feedstocks for chemicals and plastics. There is also the hope that cheap, green hydrogen could lead to inexpensive liquid hydrocarbons. Currently the cost to produce diesel or jet fuel is roughly $2 a gallon using oil. I'm on the Shell Science Council, and the cost of bio-based liquid fuel that does not compete food crops is not competitive with oil at $100 a barrel.

After I became director of the Berkeley Lab, some of the young people did alter their careers. Also, I think established professors spent more of their time thinking about clean energy. I know of a young post-doctoral scientist working in Paul Alivisatos’ group who was a rising star in nanotechnology. He just got an assistant professor offer from Stanford to use nanotechnology to build better electronics. He told me he heard one of my talks, got inspired, and then told Stanford, "I want to use nanotechnology to work on batteries. I know nothing about batteries. I know you hired me to do this, but I want to work on batteries. " Stanford gave him a little seed money to start his research. He name is Yi Cui, and now he is a big star in battery research, and I collaborate with him when I returned to Stanford after working at the DOE. He told me "You changed my life. I heard you give a talk and decided to change my research." So I felt good about that. We were getting the very best scientists to sit up and take notice because that's what it will take to find climate solutions.

I define a solution as an alternative that has to be better and cheaper than what we do today. We want an electric vehicle that costs the same as an internal combustion engine car with a 300 - 400-mile range and can go 200 miles after recharging for five minutes. An electric vehicle will have be virtually no maintenance on the motor and drivetrain. And if the car is the same cost, then it's just better and cheaper. So that's what I define as better and cheaper. When people say, "We have all the technology we need, we just need the political will," that means the alternative clean energy solution is more expensive. But if we invent something that is better and cheaper, we don’t need political will.

Zierler:

In your directorship of Berkeley Lab, what contacts or interface did you have with the DOE that might have foreshadowed your later leadership of the DOE?

Chu:

No. In fact, the leadership of the DOE was getting more and more irritated at me. The Berkeley Lab was an Office of Science Laboratory, which meant that that part of the DOE had the major influence on how the Lab is run. The senior staff person at the DOE, Pat Dehmer, was getting increasingly irritated at me. Why was she getting irritated? Because the DOE was trying to exert more and more micro control over the science we did. I resisted the increasing micromanagement and would say, "If you give us bigger hunks of money, we can decide how to divvy it up in a better way." And they wanted to decide budget allocation in Washington have more influence and authority. And in the old days, the National Labs received big hunks of money, and the directors who were very distinguished scientists, made the detailed funding decisions. That system worked well, but Pat Dehmer didn't like that, and said, "If we give you a big pot of money, and you fail, you are putting the whole lab at risk." And I said, "That's OK. We're willing to take that risk." And she didn't like that answer.

And so, every year, they would grade the performance of the lab directors. The first year, I got an A, then an A-, and by my fourth year, I got a B, which is tantamount to failing in the DOE system. My contract period was five years before renewal, and they were hoping either I'd get discouraged, or the University of California, who was my employer, would fire me. Because I was going on year four and a half, she was hoping my low grade would be a sign that the DOE did not want my contract renewed.

Instead, what happened was I got a call from a member of Obama team. It was around the third week of November of 2008. The person said , "The President-elect would like to talk to you about a very important job." I told them "Well, I wasn't really thinking of working for the government. In fact, I was thinking of stepping down and going back to my lab full time. There are lots of exciting things happening in my lab." Then, I said, "How important?" They said, "Secretary of Energy." I said, "OK, for that, I will fly to Chicago." If it was going to be a deputy position, I would have immediately said no. The previous administration wanted me to throw my hat in the ring to be the Presidential Science Advisor and head of OSTP (Office of Science and Technology Policy). I asked if that position a direct report to the President?" The person said, “No, but you're going to have a lot of influence." I replied, "In that case, I'm not interested." I'm really a science researcher, and I didn't want to become a career bureaucrat. The job eventually went to John Marburger. And he was in a tough spot because he couldn't contradict the President on some science policy issues he might not agree with. I didn't ever want to put myself in that position.

In any case, I flew to Chicago, and I talked with Obama one-on-one for about an hour. He asked me my thoughts on energy and climate change. For example, he wanted to know my thoughts on nuclear energy. So we just chatted.

Zierler:

Do you know who got you on Obama's radar, what the connection was there? Did he know you?

Chu:

Yeah, good question. So what I suspect is that there were a couple of rich donors who became very impressed with what I was doing at Lawrence Berkeley Lab. And I knew that Jim Simons, and his daughter and son became fans of mine based on what I was doing at Berkeley Lab. John Doerr also became a big fan of mine for similar reasons. So big Democratic donors liked what I was doing. It was very exciting, going in the right direction, able to generate excitement. Also, universities were also interested in getting me to become a candidate in their presidential searches because I was showing I could be a decent administrator and also generate scientific excitement. But I said, "No, it'd be disloyal. I've only been here two years."

Zierler:

And when was the meeting? Was it during the transition? Was he already president-elect at that point?

Chu:

It was two and a half to three weeks after the election. Still in November. And so, it was very early. And he walks into an overheated room on the 15th floor of a building in Chicago. He's from Hawaii. I was wearing a blazer but took it off because it was so warm. He walks in in short sleeves. I get up, shake his hand, and he says, "Everybody's telling me you should be the next Secretary of Energy." And I say, "Who are these future former friends of mine?" When I make jokes like that, he doesn't laugh. [laugh] The private conversation continued for about an hour. Afterward, I spoke with David Axelrod, Valarie Jarrett and a few others. Another part of why I was on Obama’s the radar was that the University of Chicago wanted me to throw my hat in the ring to be president of the university the year before. I told a Board of Trustee members, a friend of Obama, that I would not do that because it would be disloyal to Berkeley Lab. I should stay there and do what I came to do at Berkeley Lab." I am guessing that was another factor because President Obama was very connected to the University of Chicago.

In any case, Obama decided to offer me the job a few weeks later and I accepted. The U.S. government never had a scientist in the Cabinet before, and I was a practicing scientist and was running an active lab. So that was new. Based on my experience, I think our government should have several scientists as cabinet members. If you compare how China works with how the United States works, if you know anything about the Chinese leadership, there's a small group of about a dozen people who have the most power. Up until the current president, who is breaking a lot of traditions, the previous presidents has 70 to 80% of their top leaders, including some of their presidents and premiers, trained as engineers or scientists. Typically, engineers, but I am talking about people who had advanced degrees in engineering.

With technically trained people as government leaders, discussions like “Is climate change really happening?” do not occur. The same with the government of Singapore. They have very strong technical people at high levels in government. It would be great if the United States or countries in Europe would have at least one or two scientist cabinet-level people. It would change how things work. Having scientist cabinet members is different than having a scientist who's head of the NIH or head of the NSF. As a cabinet member, you have a seat at the Big Table, and you can pick up the phone and call the President of the United States as a direct report. And Obama treated me as a scientist. He gave me things that were out of the purview of the domain of the Department of Energy.

For example, during the Macondo oil spill in the Gulf of Mexico, I made a suggestion to BP to help them diagnose what was going on. I suggested that they should consider using gamma rays from a cobalt source. The very penetrating gamma rays could go through inches of steel and could be used to image the state of the valves on the blowout prevention platform. The idea was like taking dental X-rays of teeth to look for cavities, except the gamma rays could look through steel. I heard BP laughed at the suggestion, "He's from LBNL. The Hulk was created at LBNL, and it was gamma rays that turned him into the Hulk.” However, after two days, the engineers said, "He may be right." Somehow the President heard about my suggestion, perhaps from my Chief of Staff, and after a cabinet meeting, he comes up to me and says, "Chu, go down there and help BP stop the leak."

I decided I would recruit about half a dozen people who would be out-of-the-box thinkers to help me. I thought about who I should ask and called them up myself. They all said yes. Sometimes, they said, "Well, tentatively yes. I have to check with my department head, get someone to cover my classes, or check with my wife." And I said, "By the way, we're going to meet at 8 am in Houston tomorrow." And they all showed up.

For the next two and a half months–I lived in Houston half the time, while the others in my small group would come in and out. But there were constant emails literally every day, long discussions. Despite the stress, it was great fun because we were solving a technical problem, and we really helped BP. You couldn't do that as a cabinet member who's not trained as a scientist. I did not form a committee to give advice. And at first, the BP engineers said, "Who are these people?" But then, they began to realize we were really adding value. BP also learned we weren't talking to the press. I said, "Whatever happens here, we're not talking to the press, or trying to assign blame. We're here to help BP stop the leak," and the small team all understood that.

In the middle of May, BP decided to try what they called a “top kill.” The idea was to use the so-called “choke” and “kill” lines to force material down the BOP (blowout prevention platform) so the downward momentum of the material is greater than the oil and gas spewing out of the oil well. In addition to heavy weight drilling “mud,” a variety of materials are added in order to help clog the BOP and the oil pipe below.

We agreed with BP between each attempt to stop the flow with different materials, we would use these lines with their additional pressure gauges to measure the pressure drop across each valve in BOP, which was a two-story-high set of valves. These pressure readings would allow us to estimate how constricted was the flow path and the degree of failure in each section of the BOP. BP did not follow the plan. After the first top kill attempt failed, they immediately went to the next set of stuff. I threw a temper tantrum in the control room. It's about 2 am in the morning. I said, "Look, you guys promised you're going to do follow the plan. We need to make these measurements. So from here on in, you've got to stop between each attempt, and take pressure readings. It's only going to take 15 or 20 minutes, but we're going to do this." Thad Allen, the Incident Commander was also in the control room and could see I was mad. BP knew I could pick up a phone and call the President, so they began to follow the plan. Those pressure measurements were key to helping diagnose what was going on in the valves.

After that experience, I thought to myself, , "These guys can't be trusted. They're cowboys. They are desperate to stop the leak, but they're not taking a rational approach." So I told Admiral Allen, "From here on in, they're not going to do anything until they run it by us, and we give them approval." My little committee--well, it wasn't a committee, we didn't take votes, we just brainstormed while talking warned me, "You don't want do this, because it you insist on giving approval, you are assuming some responsibility." I said, "Well, look, I'm going to do the best I can with the information we have. If something goes wrong, yes, I’ll get fired, but at least I will have done the best I could do."

Zierler:

Something's already going wrong.

Chu:

[laugh] Something is really going wrong. And sometimes, we didn't always agree within our little group. Sometimes, there were very strong opinions, "You shouldn't do this," or, "You should do this." And there was no vote. I would just say, "Well, this is what I'm going to do. I hear all you guys, but this is what we should recommend."– bureaucrats don't act like that. They hide behind committees. But I was tackling it like an engineer or scientist trying to solve the problem. And if you make a wrong decision based on the best evidence at the time, that's all you can do. And you've got to make choices on a day-to-day basis, sometimes shorter than that.

During my whole time I was in the DOE, if I asked, I could get briefed on anything. My staff quickly learned I loved learning about new technologies, new things. They also learned I didn't like ribbon-cutting. Also, unlike most of the political animals in DC, I don't like sucking up. Scientists don't suck up at all. And I love managing down and I love brainstorming with people.

I also found that, within the permanent staff at the Department of Energy, they might've started as engineers and scientists, but as they went up the ladder, they got less and less connected to the technology – the real stuff that was going on. Some of them were pretty mediocre and were hiring consultants to do the work they were supposed to be doing. There were also a number of really good people in the DOE. Lots of really good people were very interested in joining the Department of Energy during my time there. I was actually personally doing a lot recruiting to get the very best people. I called them up personally. My approach was very simple. They were surprised that I would work for the government. I said, "Look, why don't you come and join me? It be OK if it is for two years or four years. We're here to save the world." That was my pitch. Half of them would come. One person I really wanted was a senior vice president of United Technologies. Really good guy, trained as a physicist, and very, very smart. Mike McQuade. And I said, "Why don't you join me?" He seriously considered it. He told me, "I took a week off from work. I walked the beach with my wife and kids. My wife and daughter wanted me to go to DC and work with you. But I just got here at United Technologies. There are stock options and all these other things. So I've got to hang around for a few more years. Ask me again next term." So I missed some people.

I was able to recruit Arun Majumdar from UC Berkeley and the Berkeley Lab. That was a difficult decision for him because his daughter was about to enter high school, the other was in junior high school. They couldn't move from the Bay Area to DC. He asked, would it be possible for the Department to pay the airfare so I can visit my family once a month?" I said, "Nope, can't do that." We got Ramesh (Ramamoorthy Ramesh) from Berkeley as well. Both of these people were in their early middle 40’s and had already been elected to the National Academy of Engineering and Sciences. Another half dozen people who came to work in the DOE were members of the NAS or NAE, and I think maybe another half dozen more people will be elected in the coming years. Never had the Department of Energy had such high-quality people working 60, 70 hours a week. And once they came, they would help recruit others, so it was a snowball effect.

So the type of people working in the Department of Energy in those days was just amazing. We stood up the ARPA-E (Advanced Research Projects Agency – Energy). The people in ARPA-E were only allowed to stay three years. It's written into the authorization plan. The irony is I was on the committee, “Rising Above the Gathering Storm” that suggested the Energy Department form an ARPA-E. The National Academies that sponsored the study then sent me to Congress to testify in a Congressional hearing to argue for it, and to the DOE to convince them to support it. And so, in a House Science Committee Authorization hearing, Bart Gordon was the Chair and became a big ally. He championed the idea, got it authorized. Sam Bodman, the Secretary of Energy was in favor of it, but the Office of Science was not. He told me, "Steve, I think what you're trying to do is good, but my people do not want to support this, so I'm not going to either." When I became Secretary of Energy, we started ARPA-E, and with the Emergency Recovery Act, refunded it with $200 million the first year and $200 million the second year.

The funding was only two years and would end with the Recovery Act spending. We knew we had one and a half years to prove its worth, so that Congress would appropriate it into the annual budget. We succeeded in convincing Congress that it was a worthwhile program. In the first year, they gave real money, $180 million the first year. In 2011 the budget increased to $275. By then, the House became Republican controlled after the first mid-term election A bunch of industry guys, Bill Gates, John Doerr, the CEO of DuPont, a former CEO and Chair of Lockheed Martin, Norm Augustine, and other bunch of real first-stringers wrote a report, and in it, they said, "ARPA-E's budget should be increased to a billion dollar a year." The program was very quickly recognized that this was a different way of funding and had attracted very high quality people to manage the program.

When we stood it up, it was located a short half block from the DOE building, HR and legal were was embedded in with the program managers in ARPA-E. By embedding those people within ARPA-E, they became part of the mission. These service organizations usually say, "No, we don't do things that way. We do it this way." But that's something I learned when I was director at LBNL. I started to embed the HR and legal people within each laboratory. Why? That was very important because if the people sat in an office building in downtown Berkeley, they didn't feel like they were part of the mission. Once they were sitting among the scientists in each division and learned about what was happening, they took a different attitude. Instead of saying, "No, that's against the rules," they said, "OK, let's figure out how, within the rules, to make it happen." It was a very different attitude because both legal and HR people normally go to bed each night with a book “101 Ways to Say No.” And so, I carried over my experience at LBNL to the DOE. I knew, if you're going to start a new thing in a big, ponderous, bureaucratic organization like the Department of Energy, this is the way you've got to do it. Now, my dream of getting rid of a lot of bureaucracy in the rest of the department did not work. I only slowed down the growth of more bureaucracy.

Today, it's even more bureaucratic, which is the typical evolution of big organizations. I was told by Applied Materials, "The government will spend $52 billion to invest in bringing back chip technology, semiconductor technology, to the United States." And that's a lot of money. I was asked to meet with some of the board of directors of Applied Materials. I advised them not to have the funds go through the Department of Energy. While they have a lot of technical expertise, it has become too bureaucratic. I said, “If it were up to me, I would set it up within a department that has less bureaucracy, but also set it up as a new entity to shield it from the bureaucratic rules." And I said, "This is what we did in ARPA-E, and it really worked. Every time something goes wrong, there's another rule. And then, after 50 years of additional rules, everything becomes slower to implement, taxpayer money is not spent as wisely."

But I had the time of my life at the Department of Energy. It was great. I learned so much. And that was actually the feeling of virtually everybody who was brought in during that time. Now, many of those people have left, especially after Trump came. In fact, during the Trump time, much of the department and other departments got really hollowed out. Usually, the veterans in any department see Republicans and Democrats come and go. But the Trump years devastated the morale, and the Trump administration never replaced many of the people. The OSTP (Office of Science and Technology Policy) was down to the last 20 or so people before Eric Lander was appointed. During Obama’s time there were about 160. By the end of Trump’s administration most of the good people were gone. All of the agencies with a strong science mission were hollowed out. It's tragic. There was no leadership in technology, science. People don't realize that there is fourth branch of the government consisting of the civil servants in the federal agencies.

Zierler:

Yeah. Back to your tenure, what was it like setting up the Loan Program Office? Specifically, what were the differences between setting up a loan program and a grant program?

Chu:

Huge differences. The grant programs were picking the best science and giving people money to do R&D. We expect only in the long term to get compensated. Some research comes out, it ends up as patents, which ends up as innovation. In the loan program, we're loaning companies money, or we're guaranteeing the loan, should they default. So it's either a loan or insurance to a loan. There were many more safeguards built into them. You have formal milestones in the loan contracts. So we give you a hunk of money, then you have to meet certain milestones. Because it's not given as single lump sum at the beginning of the time of the loan; it's given out in tranches. The oversight was significant. There's always an issue, if you go into something, whether companies or individuals within companies would abuse it. The bureaucracy of the loan program was set up before Obama, and that was not fully appreciated. But it didn't have a lot of money behind it.

So it wasn't until the Recovery Act that they actually put money behind it. And the loan program was set up to stimulate more daring technology development. For example, in solar energy, during the Bush era, the career people had picked Solyndra as the first loan to be issued. It looked like a really innovative approach to solar technology and was picked by the career people in the Bush Administration. But there were several companies in line behind the first loan. The loan office was taking a long time to decide these loans because of all the checks make sure that it would be money well-spent. There was a philosophy of the program was there would be a portfolio approach to the loans. Not every loan was expected to be repaid, similar to banks. The OMB would assign a risk of failure for each loan. Let's say you loan to company X. With a certain probability that the loan would fail. That fractional risk was set aside in the Treasury as “as spent dollars” to cover the risk of the loans.

So it's a form of loan insurance. And the biggest allowed risk for a loan was a 50% chance of failure, which meant there's only 50% chance this loan would be paid back. The company that was deemed the riskiest was Ford. We loaned them $6 billion. By that time, GM and Chrysler had already gone bankrupt, and the government owned GM and Chrysler. Ford recognized bad things were happening and started to save their resources. And so, they didn't have to go into bankruptcy, but they were in pretty bad shape. They hawked the Ford medallion, that blue Ford oval. They put it in a “pawn shop” so to speak. The loan was used to help them invest in cars that would get better mileage, lighter weight, more economical cars to operate.

We loaned to Tesla and to Fisker. We gave Nissan a loan to help them with the Leaf and their battery development. We loaned to a bunch of innovative automotive companies. In solar power, we loaned to Solyndra, and a few others. We supported big solar and wind projects. Projects that cost hundreds of millions to half-a-billion-dollars. Wall Street, at the time, would not touch these large projects. Solyndra's risk was evaluated as having a 12% chance of failure by OMB. People forgot in 2009, they were listed as one of the top 25 companies to watch by the Wall Street Journal. What people did not anticipate is all the tons of money the Chinese were putting into their solar industry, which really helped them. And so, if you have a $5-billion solar factory in China competing with a half-a-billion-dollar factory in the United States, just the economy of scale means the $5-billion factory will win.

And so, many solar companies did go bankrupt, Solyndra included. But also, the biggest company in Germany went bankrupt, and so did the biggest solar company in China. I think the company was called Suntech. But unlike the United States, where the Obama Administration and Secretary of Energy were severely criticized for allowing this to happen–we lost half a billion dollars ($536 million, to be exact) and didn't pull the funding stream in time. By midway through the loan, we knew that the chance of success was less than 50%, but the loan people were arguing that it was better to have a full factory than half a factory. The decision was my responsibility, but I didn't fully appreciate at the time that there was fundamentally an over-investment of capital into the solar industry.

After Suntech failed, it was propped up by the Chinese government. It went bankrupt, but the Chinese government kept the factory running. Solyndra went bankrupt, and was sold off in little, bitty pieces. Tesla would've gone bankrupt within three or four weeks after the time we announced they were getting a loan. They needed the loan to develop their S1, and they were behind. And half the initial investors were bailing out, so they would've gone bankrupt. Nissan probably would've been OK, but Ford definitely would have gone bankrupt.

In hindsight, the loan program was actually a big success. The biggest success was that large wind and solar projects were now deemed investable by Wall Street. By 2012, they were considered low risk because we wouldn't give the renewable energy projects a loan until they had an off-take agreement for at least 20 years. They needed a signed contract, "We will buy your electricity at this rate." If the projects were built on time and on-budget, they would make a profit. The real risk was essentially in the project risk. Can the project be delivered on time, on-budget? Because there's a lot of interference. For example, the environmentalists in the big solar project started getting worried about the desert tortoise, which is an endangered species. And the solar project was designed so that the areas where the area of the solar modules were fenced off, and there would be pathways where the desert tortoise would migrate through the solar farm. But they said, "That's not good enough. The fences are going to scare them away. Also, if a person picked up a tortoise to move them, they get frightened, urinate, dehydrate, and die." This maybe contributed to why they're endangered. [laugh] The company finally decided, "We'll just move them." They thought there were 500, but there turned out to be 5,000. They spent millions of dollars moving the desert tortoises somewhere else. If they wanted to fight it in court, the oppositional politics would have delayed the project. You want to build a wind farm, people come out and protest, "You're going to kill birds." In any case, most of these projects were essentially all built on time, on-budget. And then, the project managers would sell them to other investors. Warren Buffet's Berkshire Hathaway bought two of the solar farms. Because once it's up and running, they would deliver an 8% return on a very safe investment. And if you have a diversified portfolio, you want a few safe investments. So that was a big success, that wind and solar deployment in the United States went through the roof. And now, these big projects are “bankable.”

Tesla survived. That was a big success. Nissan's Leaf isn't the greatest EV in the world, but it was OK. So yes, Solyndra died, Fisker died, a few others died. But a lot of the loans turned out well. Tesla paid back the loan early. I was getting raked over the coals for Solyndra. By law, I had to personally sign off on each loan, so the blame lay on my shoulders.

During this time, Tesla was missing the loan milestones in the development of the S1. I get on the phone with Elon Musk and said, "Look, I know you're missing your milestones. I'm under tremendous pressure. So we may have to cut off your loan. But if I stop your loan, that's going to send shockwaves through the system. And you're about to go on a $3-billion capital fund for more money. So why don't you pay back the loan early? Once you are free of the loan, and it will be a sign of strength, and it will be easier raise your money." And he agreed. This was another half-a-billion-dollar loan. We had, as collateral for that loan, warrants which allowed us to buy shares in the company at a certain price and within a specified time. But by then, the Tesla stock was very high, we could have made well over a billion dollars in profit if we cashed the warrants in at that time. And we were willing to reduce this amount to a couple hundred million in profit. We let Tesla and Elon Musk off the hook, he was not grateful at all. But that's Elon Musk. He's not a grateful person. But with Tesla paying back the loan early, they raised their $3 billion, we made a little money, but could have made a lot of more money on our loan. The loan turned out to be a good thing. If I had to do it again, I would still have a loan program, but design it with fewer onerous checks and balances that it required huge staffs to administer.

And I likened having a federal loan to having a colonoscopy during the whole time of the loan without anesthesia. If companies could raise the funds without a government loan, they would not apply. We, of course, would like to loan to the best companies to make them even more successful. But the very best stayed away from the loans. Even though the rates were very low, a couple hundred basis points above prime, it was not worth the colonoscopy. [laugh]

Zierler:

How surprised were you by the level of blowback you got over Solyndra, and what were some of your big takeaways from that?

Chu:

I was not surprised. It was purely political. The charge was that we were loaning to Obama's political cronies, and not based on its merits. And so, when it failed, that was the charge. Now, there were some Democratic donors and Republican donors who invested in Solyndra. But there were more Democratic donors than Republican donors. Maybe because Democrats wanted to invest more in solar than Republicans. I don't know. But whatever the case, I was not surprised. I knew it was just a political game. They wanted to embarrass the Obama Administration, and the Department of Energy was part of the Obama Administration. So it was pure politics. My wife got very upset about it. I was less upset about it. The opposition manufactured all sort of stuff that was not true. They subpoenaed all sorts of records. Boxcars full of records went over to the Oversight Committee in the House looking for correspondence, something that was evidence that we were giving money to political cronies.

But instead, the bulk of the decisions were made by the staff people in Bush administration. After through everything, there was no evidence that there was any cronyism. They couldn't find anything, because there was nothing to find. The evidence didn't exist. They found one email I wrote, one or two sentences about something, and I put a little smiley face at the end of the email. They asked my chief of staff, "What does that smiley face mean?" He said, "I don't know, it's just a smiley face." [laugh]

Zierler:

Sometimes a smiley face is just a smiley face.

Chu:

Anyway, they couldn't find anything. There was three or four hours of oversight hearing. It could've been worse. Darrell Issa was their attack dog. Whoever is the head of the Oversight Committee is the attack dog of party in charge of the House. But actually, my staff were very good. They had me go meet with Darrell Issa a day or two before hearing. So I spent two hours in his office. And after an hour, he shooed everybody out, and we had a heart-to-heart conversation. He could have been much worse on me. By the time of the hearing, I knew he was going to go through this theater and his role is to look really vicious and mean. But it could've been much worse. Because in the end, I think he became convinced in his heart of hearts there was nothing there. I would like think he decided "Chu's an OK guy."

There were other times later on–every year of issues I had to deal with. For example, every year there's a memorial remembrance of when we bombed Hiroshima. One of those times, an 82-year-old nun and two 70-plus-year-old men hopped the fence at the Y-2 Oak Ridge, and next to the building on the site where we store all the nuclear material that is used to make our nuclear bombs. This material is the “bomb-ready,” purified stuff is sitting in this big building. I toured the place. If anyone breaches the building and gets in, they're not going to get out. So they hopped over a barbed wire fence, spray painted graffiti on the outside of the building, and waited for the security guards to come get them. Well, you're not supposed to get close to this building. So what happened? The alarms went off, but the guards ignored them. The reason they did so was because the alarms were going off 600 times a day.

The alarm system was installed a year prior, and they didn't bother to fix it. Twenty percent of the security cameras weren't working. There was no discipline with any training of the security guards. And when the alarms go off, it's not like they make a constant noise until the problem is fixed. You can turn the alarms off even if you haven't fixed the problem. If a security camera stops working it sets off an alarm, but if the camera is not fixed, there is an alarm next day. The contractor who runs the laboratory complex and the company that installed the alarm system were both trying to cover their rears. The incident caused a a big hullabaloo. "What's going on? Why can’t the DOE keep the fissile materials safe. How can we trust them?" My deputy secretary was good friends with the lab contractor, and he told me there was only three false alarms on that day before the incident occurred. I said I was not concerned about that time period. How many false alarms were there in the week before the incident?"

So I said to the administrator of the NNSA (the National Nuclear Security Agency, the branch of the DOE responsible for the nuclear bombs) , "Go down there, and find out what's really happening." And he calls me, "It's really bad. The guards were cheating on the written exams. They don't take care of the cause of the false alarms, they ignore them. They just mentally tune out that fact that they were having so many alarms." He found out the security was bad on many levels. This is our nuclear arsenal materials. Not the actual bombs, but all the stuff used to make the bombs.

In one sense, stolen material could be more dangerous, because our bombs are designed so that if someone happens to steal them, they can't set it off. If you could get your hands on weapons grade fissile uranium, a high school kid knows how to make atomic bomb out of that. In any case, the deputy had a report after four days that we were about to send to the White House. I looked at the draft of the report and said, "This is crap." So I re-wrote the report myself, and told the White House how bad it really was.

I get called before some House Republicans who wanted to investigate. Before they were going to hold a formal hearing, they wanted to see what I had to say. I spent an hour telling them all the things that went wrong. "It's really bad,” and told then what I was planning to do fix the problems. They were surprised how honest I was and decided not to hold a public hearing. This incident could easily turn into weeks of public scandal. They could also see that I wasn’t trying to cover up how bad or security had become, and that I was incensed. A half year later, the Inspector General of the Department of Energy issued its report. The Inspector General Office is an independent investigative arm of the department to make catch government waste, fraud and incompetence. The report didn't find about a third of the stuff we had found on our own.

To follow up, I talked to my old friend Norm Augustine into chairing the committee that reviewed all of the security measures. I asked Norm and his committee, "I don't want you to just look at Oak Ridge. The lapses in security could be systemic in all the weapons labs, that they're not taking security seriously anymore. They may be taking shortcuts." I was also worried that the contractors are getting paid lots of money to putting in $100-million alarm systems that were too fancy. Birds would land somewhere and it would set off the alarm. Or squirrels... stuff like that. I was worried the alarm companies wanted to make a lot of money by selling super fancy security systems that were over-engineered, with complex software and forgot fundamentals like the attitude of the guards and others in charge of maintaining the security. These things happened. But the White House was very nervous that I met with the three Republican members of Congress, but their reaction was, "Wow. Thank you very much. We're not going to have an investigation. I think you're doing the right things."

Zierler:

To go back to the American Recovery and Reinvestment Act, how useful was it as a driver for pushing forward clean energy technology?

Chu:

There were two or three buckets of money. We were investing in what was called “shovel-ready” projects to speed deployment. Also, the cost of financing was crucial. The cost of money goes directly into the cost of clean energy, so if you lower the cost of money, you lower the cost of clean energy. The reason is because renewable energy is a very CapEx intensive endeavor. The sun and wind are free, but the cost of the capital equipment is expensive. The cost of installation is also an important cost of wind and solar energy. With wind turbines, the cost of maintenance is also an issue, whereas the cost of maintaining a solar farm once is installed is much less.

In other technology areas, there was a mix of issues. I think the Tesla's S1 was a great car. The flaws were in the building of the normal “white body” part of the car, but the battery and drive train was beautifully engineered. But in the white body part, they had issues for a while with just building the “car” part of the car. There's a lot of cumulative experience in building cars, and even in the United States, companies have figured out how to make high quality cars at low cost.

Tesla had to learn how to build all of that stuff. Tesla's getting better, but they had manufacturing problems for a while. But all the engineering through the battery, drivetrain, and everything got rave reviews from their competitors as well. There's a lot of inventive stuff in Tesla cars.

We supported a number of battery companies developing new technology. Some of them died, some are still alive. There still will be more technical breakthroughs in batteries, and battery technology overall has continued to improve remarkably. The cost reduction's mostly an economy of scale. But there are some technical innovations. The lower cost of solar power is due to economy of scale, and also working down the “learning curve” in manufacturing. When I was working in the DOE, solar modules used to be polycrystalline operating with 14% efficiency. Now, the Chinese have figured out how make single crystal solar panels almost as cheaply as polycrystalline, operating at 19 to 20% efficiency. The technology is getting better. When you go from 14 to 20%, that's a big relative improvement.

And so, there are a number of really novel things I'm still excited about. We invested in how to drill into rock with no “weight on bit.” The drilling technology we use today goes back to the days of Howard Hughes who used heavy drill pipe and drilling bits with diamond teeth to grind the rock while drilling. Eliminating the need to put a lot of weight onto the drill bit would be useful for a lot of drilling that has nothing to do with oil and gas. It could be used to make geothermal less costly.

We invested in wide band semiconductors that can operated at higher voltages. High voltage power transistors are, even for EVs, which run on 600 volts. If you need cheaper, better transistors, you can run it on 1,200 volts, so there's less copper conductor in the car. What we really wanted were very high-powered transistors for high voltage DC transmission lines. The voltage is stepped up with high-frequency alternating currents, and high voltage high power transistors are needed. China has the highest voltage DC lines that operates at plus and minus 1.1 million volts per line. AC power electronics are step up the voltage and then convert the AC to DC currents. Once the power is converted to DC, it can be transmitted with less loss. There are three losses in transmission. Conductive losses, radiation losses, even at 50 or 60 Hertz, and then there are losses due to the electromagnetic field coupling to the ground. In high voltage AC transmission, the losses are engineered to be about all equal. With DC lines, you only have the conductive losses.

China has made DC power lines that carry six gigawatts per two wires. Six gigawatts at 1.1 million volts DC. Electricity can be transmitted 3400 kilometers with only 5 -10% of the energy lost. You don't need superconducting wires. And when I ask them, "It must be very expensive. The high voltage electrical standoff insulators are ten meters long." They told me, "No, the highest voltage lines are not more expensive. We compensate by putting more power into each of the lines, so, it is about the same cost." More efficient high voltage transmission lines is going to be a big deal. Germany, the U.S. and many other countries have “right of way” issues in citing new transmission lines. If you have a high voltage tower full of AC lines, and you can perhaps transmit five times more power with in the same tower, if the AC lines are replaced by DC lines. Germany's beginning to do this. The pathetic thing about the United States is, we have very, very few DC lines. Meanwhile, China has built an entire network of very high voltage transmission lines.

The cat's meow would be a diamond power transistor. Diamond has great thermal conductivity and can withstand much higher voltages across the transistor junctions. Diamond transistors would be wonderful. People are researching diamond transistors, but they haven't really achieved what we think is possible with diamond. When I was working in the DOE, we tried to identify places where, let's say, a Siemens, an ABB, or a GE would never invest in materials research needed to make better power electronics, so it's a public good investment. So it's hard to know when these things really hit it big because it's going to take years. So it's a wide gamut of things we invested in.

The batteries are coming along. I'm on the board of a battery company, I do battery research myself now, and advise Applied Materials which is beginning to make separators for batteries. And the technical progress in batteries is still zooming ahead. There are people trying to develop fast charge batteries that literally will give you in five- or ten-minute charge time a couple hundred-mile range. There is a possibility these type of batteries will be commercially viable within ten years, but it takes about five years to get an OEM to put a new type of battery into a car.

Lots of new technologies are needed. My biggest push, and this is what I was telling people in my talks on climate change, clean energy, and more environmentally friendly practices. We also need a new agriculture revolution. It's just not using agricultural products to substitute chemicals, plastics, and fuel. We will have a population going to 11 billion by the end of this century. We're close to eight billion now, and half the arable land is under cultivation or is grazing land. As countries get wealthier, their demands for a better diet are increasing, and the demand for meat is increasing. Meat is a very inefficient way of producing food. We're beginning to develop plant-based meat substitutes, plant-based milk substitutes. If you take all the beef and dairy cows in the world, the greenhouse gas emissions they produce would be more than the EU 27 plus Great Britain and comparable to the United States. And we eat three times the weight of all the wild animal mass in the world. 96% of all the weight of mammals are us, the humans and the animals we eat. A meat diet is a very inefficient the use of land resources. Especially if we raise beef. Pork and chickens are three or four times more efficient in terms of land use, and energy and water inputs.

I'm on the board of a company that bioengineers microbes using synthetic biology. JBEI at LBNL was started for the same reason. The goal of synthetic biology is to engineer their genome so the entire metabolic pathways can be introduced to carry out new functions. For example, a company called Pivot Bio has altered microbes so that they can supply food to the roots of corn to replace nitrogen fertilizers. The microbes that live at the boundary of the roots of food plants and the soil. The microbes have been altered so they have symbiotic relationship with the plants and supply the plan roots nitrogen nutrients so that less fertilizer is needed.

About 1.4% of the world energy consumption if used as energy inputs to manufacture fertilizer In addition, any fertilizer not used by the plant is emitted as N20, a potent greenhouse gas, and fertilizer runoff is about 2-3 % of all greenhouse gas emission from human activity. We are heavily reliant in adding plant nutrients but need to take the GHG emissions out of fertilizer production and fertilizer runoff. If we can get microbes to make food for plant with no carbon emission, and where there will be no excess nitrogen compounds not consumed by the plants will eliminate up to 5% of all human GHGs. So we're trying to get this to do it with high-fertilizer crops starting with corn, then see if this technology can be used to raise wheat, rice, sorgum and other plants. Also, current farming practices are a big contributor GHG emissions.

There is more GHG emission from farming, grazing and land management than the entire electricity generation in the world. The wonderful opportunity is that a number of new technologies are emerging, so that there's a real hope that we can transition green agriculture, Without a fourth agricultural revolution of the type I am talking about, there's no way we're going to get anywhere close to going to net zero emissions in next a half century. So JBEI 's doing this type of research and private enterprise also investing I these areas. That journey started with heavy investments in the Department of Energy, during the years around 2009 and later. Also, there are other people make other biological discoveries, but turning those discoveries into widespread deployment is going to take time.

We definitely need a new revolution in agriculture. The third revolution was the ability to make nitrogen fertilizers though the Haber-Bosch process, and the breeding of higher yield grains, beginning with Norman Borlag’s dwarf wheat strains that would thrive on higher doses of fertilizers. From 1961 to 2021, the world cereal production increased between 2x to 6x per hectare. We need to continue to increase grain production but now need to dramatically cut the GHG emissions due to emission to make fertilizers, N2O emissions due to fertilizer runoff, and methane emissions from ruminant animals and food waste.

Zierler:

Back on the administrative side, how did you manage the new distinction of labor between Bill Brinkman as Office of Science Director and Steve Koonin as Undersecretary for Science? How did you manage that?

Chu:

Brinkman, was in charge of the Office of Science, which includes all the science labs, and things of that nature. Koonin had sort of an overarching portfolio, but in the end, he told me, "Unfortunately, you're effectively the Undersecretary of Science by managing down." So he said, "There's not that much for me to do." Now, he did a good service. We did the first of the quadrennial reports of reviewing the portfolio of the Department of Energy, where we're going, what is needed. And so, he did a very good job of looking into the Department, where things were going, what was happening. He didn't think he had enough of a portfolio, so after about a year and a half or so, he left. No hard feelings, but he said, "You don't really need me because you're you." So he left the DOE.

Zierler:

Were his views on climate change part of that? Did you value and understand that he had a few different ways of thinking about climate change?

Chu:

Well, yes. Well, his view, if I had to summarize it in three sentences, is that the uncertainties in climate change are bigger than we think. He's part of the JASON crowd that was very skeptical when other non-scientists would overstate their knowledge on how the climate will change. They'd say, "No, that's not scientifically based. It's fear mongering. We don't understand the full range of risks or uncertainties," which was true. When I was director of LBNL, we had some really good climate scientists. Inez Fung was one, I recruited Bill Collins, who has now become a real big shot in climate modeling. And Inez said, at the time, "We've only just begun to try to understand the biological feedbacks to the climate system." But the biological feedbacks of the climate are huge. Really huge. Biology gave us an oxygen atmosphere. Without photosynthesis, there would be no oxygen.

When you have increased CO2, there's going to be an uptick in plant life. The biological effects in the ocean, both the good and the bad, mostly bad, more acidity. We still don't understand what the small phytoplankton in the sea are going to do, whether their shells will get so thin, they disappear, or whether they'll adapt. Phytoplankton obtain their energy through photosynthesis and constitute a significant portion of the base of the marine food supply. They account for about half of global photosynthetic activity and oxygen production. We still didn't understand if climate change will threaten the foundations of the ocean food chain. Some environmental scientists were afraid that if the oceans acidify, the thinning phytoplankton shells would lead to a collapse of the ocean food chain. Now, since I've left the Department of Energy, I've taught a course in energy and climate change, the physics of climate change. The course also includes biology. I examined the fossil record shells of the 50 to 100 million years ago when the ocean was far more acidic and the temperatures were far higher. The fossil records show the those same critters were around then, and they had thicker shells.

During those times, the plane of climate was more gradual compared to today, so there remains a risk that these plankton will not be able to adapt fast enough to thrive in a new climate. There's no certainty that everything falls apart. Yes, corals will bleach and die and things like that. So Koonin was skeptical in that way, which is fine.

It's good to have a skeptic or two in your midst. I have no problem with that. I think some people don’t like people like Koonin because they don’t like to hear that there are significant uncertainties in the climate predictions. A core virtue of science is that people who challenge accepted dogma can stimulate a critical re-examination about what we know, what we think we know, and what predictions are on less solid ground. However, in the last decade, there has been a lot of progress in understanding the very complex climate system, including the bio-feedbacks. And a lot of the deeper understanding is not good news.

Zierler:

Tell me about the Energy Frontier Research Center and Energy Innovation Hub programs. Did you specifically see these as a departure from the way DOE traditionally funded these kinds of programs?

Chu:

Yes. I did. So for example, for innovation hubs like batteries or nuclear power, what I wanted was to bring together a bunch of people around a very specific problem. There are certain challenges in batteries. We would fund individual investigators, but I wanted more communication between different researchers. And ideally, what I really wanted was for it to all be under one roof, like at Bell Labs. A Bell Labs for batteries, for nuclear technology. Nuclear technology meaning, can you improve a lot of the technical things? The fundamental economics means you'd have to learn how to build on-budget, on time. But you can do things like getting more electricity from the fuel rods, getting more output, things like that.

So even though we're going down in the number of nuclear reactors, we were steady or going up slightly in the amount of electricity generated by nuclear reactors. Until we either close them all down or build a new generation. Who knows? But the answer to your question is, I wanted people to begin to talk to each other and say, "OK, what are we doing?" Rather than three or four independent groups doing something, going after the same thing, replicating efforts, not talking to each other, and competing. Is it possible to actually get them to talk to one another, more like industrial research, where sometimes, industry wants a little competition to really get people's juices flowing, but they don't really want what is done in academic research.

So that was the idea. Sometimes it works, sometimes, it doesn't. But I wanted the communication lines open, the sharing of information. Because that's what happens in general in science. You sometimes have to wait for publication. But someone makes a breakthrough, and it just goes like that. And so, can you make that go faster? My vision was to start a Bell Labs or Los Alamos seeking energy solutions.

Zierler:

What were your interests in supporting the high-profile physics programs as Energy Secretary? Specifically, high energy physics and fusion energy sciences.

Chu:

Well, there were exciting things going on in high energy physics. It was a small part of the budget. Astrophysics is something the Department of Energy has always funded. I wanted to continue that, for sure. We were the biggest funder of physical sciences, bigger than the NSF. Fusion's tricky because ITER was beginning to suck up most of the money for fusion, which is unfortunate. But the problem with ITER is that unlike CERN, they didn't get a pot of money, and then empower a director general to make it happen. The countries decided they would contribute in kind to make sure that the money, jobs, and everything else they were investing in ITER would be spent in their country. And so, things got divvied up perhaps not in the best way because of that. So it became an administrative nightmare, and it was very hard to get it to work. During my tenure, we went through two director generals of ITER. The first one was a disaster, the second one was better.

Finally, we were able to get Bernard Bigot to be director general. But this was after several re-baselining of the budget, and the estimated cost of the project was three to four times over budget. Now, the turn-on time has drifted back at least a couple of decades. Also, ITER is a scientific experiment, and after that, there is a follow-on project called DEMO. DEMO will be designed to actually generate hundreds of megawatts of power as a necessary step to see if fusion shas a chance of generating power economically. There are still issues regarding neutron damage. With the expected neutron flux of a commercial tokamak, the vacuum chamber would be nonfunctional in a couple of years, which would be a nonstarter. So in addition to a lithium blanket used to abord neutrons to breed tritium, a fusion reactor would also need a sacrificial layer of material.

In a year, it was estimated that the neutrons bombardment would cause the atoms in the material to be displaced around 100 times in one year. This created a lot of dislocations and swelling of the material. Before the sacrificial layer falls apart, before it crumbles, you have to stop the fusion reactor, and use a robot to remove the sacrificial layer, which will be radioactive, and install a new layer. One could hope to be back on online generating power. Because the material will be radioactive, this procedure, in the most optimist scenario, would take a week, but I think this goal was set more by the economics of what would be acceptable down time instead of what may be possible with large scale precision robotics. There are other material problems. Inside a tokamak, there are structures called diverters, or “scrapers,” that are needed to remove the waste materials produced in the reactor. The scrapers will be subject to very harsh conditions, and will also have a limited life time. So the materials problems are much harder to solve that the ability to maintain the needed plasma for commercial fusion. We have made great strides in understanding tokamak plasmas, but developing new damage resistant materials is more of a black art instead of a solvable physics problem.

And realizing the dream of a commercial reactor–even a $10 billion conventional nuclear power plant is a huge financial risk. So you're going to spend $20 or $30 billion on a fusion reactor, industry would not be able to take that financial risk. So the first several fusion reactors would have to be paid for by taxpayers. Indeed, the risk would need to be spread over several countries.

In the end, I just don't know whether fusion will ever become commercially viable. There are other end runs around it. I know several companies trying to do smaller things that aren't at the scale of ITER. I don't know if they are going to work either. I am on a scientific advisory board of one of those start-up companies. The probability that any of these companies will develop a successful reactor is low, but who knows? Maybe one of the ideas will lead to a breakthrough.

We do need compact energy sources for sure, whether it's going to be small modular nuclear reactors, or natural gas with carbon capture, or something else, I don't know. But we will need standby power. In order to have a grid that's reliable, you need humongous amounts of energy storage if there are no turn-on electricity generating stations.

There was a big study written by three veterans of ARPA-E that looked at how much energy stores you need for–in the United States, we're very rich in renewables, in wind and solar over four time zones and different weather fronts. Their conclusion was, "If you want to get to 80% renewables for electricity generation, you need about 100 hours' worth of storage." That's 100 hours’ worth of storage that could supply the average electrical needs of the entire country. That is to get to 80% renewable electricity. If you want to get to 100%, the amount of storage increases dramatically. It turns out that getting to 80% would require about 10,000 gigawatt hours of energy storage. We've got three gigawatt hours today. And the price tag should be $20, $30 per kilowatt hour. It's right now $300. So this is a big challenge to get to 80%, and to get to 100%, you go up by an order of magnitude. So when I hear, "We have all the technology to go to 100% renewables," that's just not true, because energy use and its cost are inseparable. And so, what is going to supply the rest is this emergency turn-on–the Southwest is baking. We're avoiding blackouts so far, but there's going to be more of this in the coming decades.

We will need some standby power. Natural gas in the ground or in pipelines is standby power. Fossil energy is a really cheap battery, but we will need to capture the carbon and sequester the CO2 if we want to use natural gas. An alternative is nuclear fission. While fusion energy is a possibility, you can't hold your breath waiting for fusion. It's much more likely we'll get $30 batteries than we'll get fusion. I'm a big advocate of pumped hydro. There are people against hydro in all forms, like there are people who were against solar and wind.

Some people wanted me to breach the system of dams in Washington and Oregon. The DOE is a partner in the operation of the Columbia River Basin system of dams. A group came to see me to breach those dams because they were killing the salmon. I said, "No, no, no. We're putting in fish-friendly turbines, installing fish runs that bypass the dams, and more. The population's beginning to come back up. If we breach the dams, we're going to go to turn to fossil fuel to generate electricity. That will add carbon emissions and accelerate climate change. If the water temperature goes above 70 degrees in the Columbia River, there will be no salmon." They said, "Well, that's going to happen 50 to 100 years from today, and we are worried about now." So some of these environmentalists, I think, may be more in love with protesting than actually fixing the environment.

Zierler:

Separate topic, what were your views on the way NNSA existed as a semi-autonomous agency within DOE?

Chu:

It was beginning to be more incorporated back in the DOE. The whole thing that started the separation was the Wen Ho Lee case. And they wanted to split it off and have it go in the Department of Defense. And there was a real concern at the time that if it went into the Department of Defense, all of the science-based stuff that was involved with stockpile stewardship would be lost. And I agreed with that. I think the Department of Defense is not as good at managing science laboratories. And our nuclear stockpile and its stewardship is a science-based endeavor. In any case, the NNSA was created and split off from the rest of the DOE. When NNSA was first started, I became a member of the advisory committee in the Bush 2 Administration. Condi Rice twisted my arm to join. The NNSA part of the DOE had and still has issues, like the security problems I talked about.

Returning to a science-based approach to our stockpile stewardship, the military used to sponsor lots of great basic and applied research. But they started going away from developing the technology they needed and were pressured to seek commercial solution instead of doing expensive in-house development." And the military was a primary mover of a lot of the technology in the 50s, 60s, and 70s in the United States. They were the engine behind a lot of what was happening in semiconductors, electronics, microwaves, you name it. Then, they decided, "It would be cheaper to just buy it." I think they're changing now because if you buy the technology, we become dependent on the companies and countries that developed it. In China in particular is an issue. I think we need to have homegrown expertise of the real state-of-the-art technology, and this realization is growing. But the military stopped funding what is called the basic 6-1 research. 6-1 research before was pie-in-the-sky stuff while 6-2 research was more short-term applied research. Today, what is called 6-1 research is beginning to look more like 6-2 research.

And so, that leaves the NSF and the Department of Energy. There was a long-term view that originated from the Manhattan Project on forward, and the culture of Department of Energy labs was from Los Alamos, Metallurgical Lab in Chicago, Lawrence Berkeley Lab, and these other places. The culture of the DOE labs was grown out of those things, which really got a big boost during World War II. And Oak Ridge, too. The NNSA is coming back into the fold for good reasons because there's a lot of overlap. A weapons lab's primary mission is still weapons, although they're branching out now, and they're getting Office of Science contracts as well. The NNSA labs have very different security requirements.

Zierler:

Did you have a close working relationship with John Holdren? And more generally, did you see the OSTP as a partner in terms of getting the most important policies to Obama?

Chu:

Yeah. I certainly knew him well before our time in the government. And certainly, we worked very closely together during the Fukushima incident. He knows about nuclear physics and nuclear power. In terms of the other energy technologies, some of those areas is a little bit outside his expertise. He's mostly an arms control kind of guy. And he worked very closely with Ernie [Moniz] in negotiating with the Iran treaty. But certainly, we both were informed and were very concerned about the risks of climate change. I think he had the trust the President, but the immediate White House people around the President didn't really like him. I think they tried to screen him out of some of the White House discussions. They didn't like him going around giving talks on the climate. They did not give me a lot of talks on climate change, but they couldn't stop me because I was a cabinet member. He had to tone down some of what he wanted to say, but I didn't feel compelled to tone down anything. It's a strange political world in the White House. Those who get to see the President first in the morning, last at night are the ones who have the most influence. And I regard some of them like moths around the flame.

Zierler:

What about at the OMB? Did you have any key partners at the OMB who were useful for your agenda?

Chu:

No, mostly, I was fighting with the OMB. They have incredible power, budget authority, and tremendous influence. Some people in the Obama Administration, like the economic people, Tim Geithner, Larry Summers, Jack Lew, were not strong climate advocates during my time with them. I was in the Obama administration because of what I wanted to do in clean energy and climate. And Obama felt very strongly about those missions as well. But they were different, and so there was a slight tension there. For example, I was in favor of a loan guarantee to a company trying to figure out how to put solar panels on top of commercial buildings, like K-Marts, Home Depots, and warehouses. The financial people believed the private sector should be doing it. They were the free-market economists, and they believed the free market could do no wrong. My joke was, "How many free-market economists does it take to change a lightbulb?” The answer is “None. If it needed changing, the free market would've done it." International fishing and climate change are two examples where the free market completely fails.

Zierler:

What about Congress? Were there any Senators or Representatives that you really considered allies?

Chu:

Yes, on both sides of the aisle. In the Senate Energy and Natural Resources Committee, four most important members were Jeff Bingaman, Lamar Alexander, Lisa Murkowski and Dianne Feinstein. They were all great, and politics never entered any of our discussions. Lamar Alexander was a great ally to me. I was trying to get Carl Wieman hired in OSTP. Carl was a Nobel Laureate for his work on Bose condensation, but he got interested in science education, 10 or 15 years before I became Secretary. He led a science education institute in UBC Vancouver, and had started one the University of Colorado in Boulder. And I said, "If you really want to change science education, come to DC and do it." I finally convinced him to come, but then his appointment was being held up by an unknown senator. In the Senate, you can put a hold on a nomination, and you don’t have to identify yourself, and you don’t have to give a reason why. It’s sort of like just hold your pinkie up to stop an appointment. It's sort of like what it takes to start a Senate filibuster.

I called up two friends of mine, both Republicans to help. One was Lamar Alexander, the other was Norm Augustine. I said, "Carl is getting really upset. He's been hanging around DC. He and his wife moved here and have been here five, six months. He's about to go home. We don't want to let this happen. He's a Nobel Laureate, he just won a $3-million prize in science education and is a serious guy. And so, can you help?" I didn't ask the White House, I just called my friends. The White House wanted everything to be going through them, but I didn’t think they would help. Instead, I called Lamar and Norm. Lamar said, "Yep, I'll help you. The same thing happened to me.” He was President of the University of Tennessee when Bush 1 asked him to be Secretary of Education. He came to DC, and then waited to be confirmed. His nomination was held up for four months. During that time, he was spinning his wheels.

Before you get confirmed, you can't give advice. You're allowed to attend meetings, but you can't say anything. When Carl called me, the August recess time was approaching. Carl Wieman said, "Unless I get a recess appointment, I'm out of here." And so, John Holdren, who was going to be his boss at OSTP, and I both said, "Don't do this. Yes, you can get a recess appointment, but no one actually respects people with recess appointments on both sides of the aisle because it skirts the confirmation process of the Senate. And so, just hang in there." And a week after Congress came back, he was confirmed. Lamar Alexander figured out who was causing the hold and made it go away.

When I was in DC, I got to know a bunch of people on the left, on the right, and in the middle. Some of them took positions that were different than mine, but there was kind of a mutual respect. There were a bunch of people trying to do the right thing on both sides of the aisle. Now, a lot of that seems to have just gone away. A lot of the veterans in the middle of the political spectrum left. Bingaman just got tired of the increasingly partisan politics and said, "I'm out of here." Lamar Alexander's quitting now. Lisa Murkowski was also great, but couldn't even get the nomination of her party, and had to run as a write-in candidate. There's a bunch of people on the moderate side I could work with. Lindsay Graham was someone I could work with during that time. He's unrecognizable now, but when I was there, I could work with him.

Joe Manchin and I got along swimmingly well. He was governor at the time, and he and I would tour around in West Virginia. Our message was, "We're not trying to wipe out coal. We're trying to get carbon capture to work and give West Virginia time to make a transition." I can go down the list of people who are in this middle ground. Joe Lieberman. There were Ed Markey and John Kerry who was on the left, but they could work with people in the middle. When I met a Republican and said, "Yeah, I can work with this guy," those people were retiring or were having trouble getting re-nominated, by their party. You could see the split occurring. The veterans would tell me that it used to be a time when everybody lived in DC. But now, they don't. They have to go back to their home states every week.

The Senate only votes on Tuesday, Wednesday, and Thursday because they're flying in and out on Mondays and Fridays as though they were continuously on the campaign trail. This was happening in the Senate where elections were every six years. So think about what the representatives had to do. They rent some hovel somewhere in DC and had to fly back to their home district almost every week. And their kids are rarely being raised in DC, they're all back home. Well, if you don't meet with members of Congress in PTA meetings, at soccer games or band concerts, you don't get to mix and mingle with the members on the other political side. There was no easy way to build trust. I wasn't a politician, so they would confide in me, "It's not like the old days." Since then, it's gotten much, much worse in the last half dozen years. Which is very sad. It's tragic. Because unless people trust each other, things are going to fall apart.

Zierler:

On the international stage, what opportunities did you have to work in the capacity of a diplomat or to work with your peers around the globe?

Chu:

Mostly on climate change. Mostly on things that required international cooperation. I started a little group we called the Clean Energy Ministerial. The group started with about 20, grew to about 25 members by invitation only. It included the major economies and other smaller economies that were leaders in fighting climate change. The purpose of the group was to share “best practices.” We weren't looking for international agreements or trying to duplicate the UN. We were not seeking commitment from governments, and anything like that. we wanted to just share best practices.

Let me give you an example. Appliance standards. They save consumers and countries lots of money and lots of energy. Energy efficiency is a great success story, but there are a lot organizations and people against energy efficiency. In developing countries, South Africa, for example, businesses in more developed countries want to sell them refrigerators and air conditioners, but they would not be allowed to sell in their own countries because of energy efficiency standards. Essentially, they wanted to sell them their leftovers, their junk. China would try to sell developing countries their stuff that was no longer legal to be sold in China because of their energy standards. But they would dump them onto developing countries because they wanted to get rid of them, and it's an easy market. Appliance manufacturers don't pay for the energy used by their products. And energy in developing countries is generally subsidized, which means the taxpayers pay for it. But then, how do you get a developing country to set up appropriate standards? And what they realized is, in the United States, there's a whole infrastructure that has to be set up evaluate standards, and as the technology improves, decide how to change those standards.

We decided it was possible just to follow the energy standards a couple years behind the standards used in the developed countries. You don't have to have the same standards as the US because the purchase price in developing countries is still the most important consideration. But in the United States, for example, you're not allowed to put in a higher efficiency standard unless you can prove that the cost of ownership is overall cheaper. So that's the bottom-line energy standards, which were a regulatory push. We have higher efficiency ratings like “Energy Star” ratings, which is an industry “pull.” Updating the requirements of the Energy Star ratings in the United States is shared between the EPA and Department of Energy. As technology gets better and better, you want to raise the bar for Energy Star and for minimum energy standards. So we started talking about things like that. How do you promote energy efficient buildings? It's a difficult question since the people who build the buildings are generally not the ones who pay the energy bill.

We discussed what were the emerging technologies, what other countries are doing, how they're making the transition as they go to more and more renewables. At the time, Europe was ahead of the United States in policy issues. It was very easy to find out what other countries were doing in policy.

Buildings still remains an issue. How do you incentivize people who build buildings to make them more energy efficient if they're not going to pay for the energy bills? This is called the “principal agent problem,” and it remains a problem.

You can give incentives to construct more efficient buildings. I did not like the LEED certifications because of several reasons. You get a certification based on design, and I said, "It should be based on performance. The certifications can be initially based on design, but I wanted the certification to be recertified every year or two to make sure the building efficiency doesn’t slip backwards." For example, LEED certifications encourage low flow faucets in the bathrooms and kitchens. I have heard that sometimes after the certification is awarded, they open up the flow rate. There's a lot of stuff like that that goes on in the world.

There are good examples of how efficiency standards in developing countries saves tons of money. Consider energy efficient fans. You can make a fan with a motor that's 90% efficient or you can make a fan that's 50% efficient motor. India has mostly fans, not air conditioners. And there's a tremendous amount of electricity waste when you have a cheap, junk 50% efficient fan. So I would work with the government and people who really wanted to push it in the right direction. When you sell a fan in India, you don't have to pay for the electricity, so you're going to make it super cheap. Saving a penny here and there saves in the manufacturing costs, but it costs the country a lot of money. And so, there were things like that we discussed in the Clean Energy Ministerial.

I set up cooperative agreements with China on clean vehicles, clean buildings, and transmission and distribution of electricity. The vehicles turned out to be a little tougher because it's a very highly competitive business. But in buildings and distribution–you don't build buildings, put them on a boat, and ship them – so it is possible to set up cooperative research agreements. Despite the fact that we seem to be entering into a cold war with China, there's still general agreement that the United States and China have much to gain in climate change. And so, things like nuclear power as well. The Department of Energy is kind of the rallying point for a lot of the nuclear technology.

There's a IAEA nuclear meeting each year in Vienna. The Iranians also go to that meeting. They're part of this nuclear cooperation meeting, believe it or not. During one of the meetings I attended, they were giving away little keychain flashlights with the shape of their centrifuges. In the same, my computer was hacked and it crashed and could not be restored.

In terms of what I what I was trying to do at that the IAEA meeting, I was trying to impress upon the people, countries and industries, the importance of nuclear safety. I said a nuclear accident anywhere in the world would be terrible for the entire industry. This was before Fukushima. My concern was that there were more countries and companies wanting to sell nuclear reactors to UAE and other countries.

There is a proliferation issue and there was a safety issue. You have to have trained personnel who were really good at operating nuclear reactors. It's like training to become an airline pilot. You want high-quality personnel who know what to do in an emergency when things go wrong. Nuclear safety was within the bailiwick of the Department of Energy, and so were new issues like climate change. In the international arena, I was mostly focused on nuclear safety and non-proliferation, but I was not negotiating the Iran nuclear deal. That issue came after my time at the DOE. It was mostly energy stuff.

The Copenhagen climate conference was a disaster in terms reaching any agreements. But it redoubled the efforts of the Obama administration. In the end, actually, it was the President of China and the President of the United States that saved the day in the Paris meeting.

Zierler:

A rather reflective question, to what extent did you set a certain bar as a scientist at the DOE going forward? Whatever the ins and outs of the selection of Ernie Moniz to be your successor, what value do you think generally was appreciated of you being a scientist, and even a physicist specifically, as Energy Secretary?

Chu:

Well, I think, and this is really to President Obama's credit, I was a practicing scientist. In addition to Macondo and Fukushima, he turned to me for other things. Fracking was becoming a very contentious issue, and so he asked the Department of Energy to draft what the federal guidelines for fracking on federal lands. That drove the Interior Department crazy. Because just like Macondo, that was their responsibility. So in a number of occasions, the President turned to the Department of Energy because he wanted a decision based on technology and science, not based on politics.

And he was right. In fact, I got phone calls from Senators in the later half of my term that said, "Well, look, I'm calling you because I want some Department of Energy funds for my state for this and that." One powerful senator called me and said, "I know you're a numbers kind of guy, and what I say is not going to have much influence on your decision." And I said, "You're right. It's not. You talk, I listen, you can go back to your constituents and say you talked to the Secretary of Energy." But not all cabinet members in Obama's Administration, or before or after, acted that way. I felt that our decisions should be made on the merits. And there were times when I got angry people, Congressmen or Senators, who asked me, "How could you do this?" And I said, "Well, look, this is how I made my choice. You are welcome to come to my office, and we can talk about why I did it." But they never did. I also said, "Bring people who are upset, and we can talk." And they never did. Because they're going to lose in a discussion based on technical merit.

Because energy issues are laced with politics, I had to be aware of what we were doing. But in the end, I said, "We've got to make sure that this is, in our best technical judgment, what's best for the taxpayer money." So that was important. I promised myself going into the job, I would never lie and lose my credibility as a scientist. And even things I didn’t agree with, I didn’t really have to lie. For example, Yucca Mountain was a political hot potato. The Republicans wanted Yucca Mountain. Harry Reid, who was the leader of the House, didn't want Yucca Mountain. He gave me a nasty phone call even before I became Energy Secretary. "I heard you're becoming Energy Secretary. I just want you to make sure there's going to be no repository at Yucca Mountain." And I said, "Well, Senator, I tend to agree with you, but as a temporary repository, it might be OK." He said, "There will be no repository, period," and slammed down the phone.

Now, I didn't have to lie about Yucca Mountain. I said it was not a good site. I knew this before I was Secretary of Energy. When I was director of the Berkeley Lab, we did a lot of the hydrology studies of Yucca Mountain. Hydrology is the study of the flow of fluids in rock. The study showed that it was not a good choice. In fact, as they started to drill into Yucca Mountain before I was Secretary of Energy, they found that water started dripping through the rock into the tunnels. I got to be friends with the Deputy Secretary, Clay Sell, and the Secretary, Sam Bodman. And a year before I was Secretary of Energy, I was in Clay Sell's office. He told me they discovered that the rock was saturated with water. Radioactivity and water don't mix. So even though Yucca Mountain is in a desert, there was still a lot of ground water that seeps in. And Clay said, "You know what the proposed solution is? You can't believe this. They're going to put a titanium shield in the mountain that will cost another couple billion dollars."

And I said, "That's not going to work." He said, "Of course, it's not going to work. This is ridiculous." So here is a Republican administrator saying, "This is stupid." During my time in the department, I said, "It would have to pass a 10,000 year certification requirement.” By then the Supreme Court ruled that the scientists needed to assure the public the repository would be safe for at least up to a million years. The hydrology studies we did suggested to peak leaking would in about 400,000 years. For the first 100 years, the heat of the radioactivity would keep the water away. But after that, it has to be the rock, the geology could create safe million-year storage. In our stand against Yucca Mountain, I kept on insisting that it was not a good site. I would say, "This is what we found, and you can check the science. It's just not a good place for long-term disposal of spent fuel, and we should start again to look for a better place."

I set the groundwork for doing this, got the President to name a blue-ribbon commission to look for a way of locating suitable repositories for long term storage. Sweden had figured out how to do this, and the group recommended that you form a little organization to try to get it out of the purely political realm, try to find out the best geological place and how many sites were needed. The blue-ribbon commission made a set of recommendations. All the recommendations, save one, I knew about. And the one I didn't know is, what they found was that Sweden had gotten a semi-private organization to help locate potential repository sites. They got three areas in Sweden to bid for the site. Those regions wanted to host the site because it brings in business and lots of money.

But there were all sorts of other issues with dealing with spent nuclear fuel in the US. Having to nuclear waste cross state lines is a big issue. Jeff Bingaman in New Mexico did not want the site in his state because the voters didn’t want radioactive material being trucked around New Mexico.

Carlsbad was already a low-level repository for nuclear waste. The site was a salt formation that was very stable. The salt was radioactively dated that it had been there for five-million years. That meant there had been no water for five million years, because if water reaches the salt, you have a big, hollow cavern.

So the blue ribbon committee knew the storage had to be based geological confinement. Finding a good site is still not a solved political problem. It turns out that since then, a friend of mine from Berkeley, Rich Muller, and his daughter founded a new company called Deep Isolation. Their idea is to use bore holes and advances in drilling technology from the oil and gas industry. One can drill a couple kilometers down and then drill sideways in stable geological formations. The advantage is that you can place the radioactive material deep underground without having to build roads and ventilation systems for humans, and that lowers the cost. You will have access to many more different types of geological sites that could be safe. The difference in cost can be huge, like the difference between manned and unmanned spaceflight.

Their company is now trying to get permission to drill some test bore holes, first without the radioactive materials, then with low-level radioactive material. But going back to being a scientist, mercifully, I did not have to lie while I was Secretary of Energy. I would not have lied and would've resigned instead.

Zierler:

How closely were you involved in the handover to Ernie Moniz?

Chu:

It was during my exit interview. I told the President that my wife did not want me to stick around. She was getting tired of DC. She was going back every month to visit her grandchildren in the Bay Area. And finally, she said, "No one's irreplaceable, not even you. I know you want to stay for more years, but I'm tired of DC. I'm moving back to California. I hope you come with me." So I told the President, and he said, "I understand. What do you recommend we do?" based on the fact that both the Senate and the House were Republican, and this would be executive actions because the chance of legislation was nil. McConnell was very effective in blocking things. Still is.

And we talked about a few things. But in the end, I said, "Look, Mr. President, you get a lot of credit. You hired me as a scientist. I didn't do politics. I know there are people around you who don't want that to happen again because scientists can push back. But you get a lot of credit for it. Do it again." Which he did. Because a lot of the inner circle didn’t like to deal with scientists. They can be stubborn and don't listen all the time. I was willing to say, "No, that's not right. This is wrong. You can't do this. And there are technical reasons why this policy should not be this." In any case, he did it again.

Zierler:

Did you float Ernie's name? Or would you know that he would be on the short list?

Chu:

Oh, I knew because he was being considered for my job during my time. He actually likes DC. He loves it. He was an Undersecretary during Clinton, and he hung around DC the whole time during Bush 2, even though he was a professor at MIT. He was living in DC. He didn't get the job and went back to MIT. He loves the DC scene. I thought serving as Secretary was a time public service, and after my time, I wasn't going to hang around DC. I could've stayed, but I wanted to go back to the lab.

Zierler:

Were you concerned that you lost your muscle memory in the lab? Was that something you thought you might not be able to pick back up?

Chu:

I didn't know. When I joined the administration, I didn't know whether it was four years or eight years. I was thinking it could be eight years. I had my post-docs take their equipment with them. My group went to zero. I wasn't allowed to apply for research grants. The ones I had, I couldn't ask for renewal. I had to get my colleagues to sign for things because I had a dozen people still in the group who were going and getting jobs. Graduate students and post-docs. By the time I got out, I had no group, no funding, no space, no nothing. Berkeley, in hopes that I would come back, saved my space. After a year, they said, "Can we let other people use your office and lab?" I said, "Sure." Well, my lab space was there until the post-docs left it. And so, that took a while.

So my wife decided we were going back to Stanford. There was no choice. Well, the two choices were Berkeley or Stanford. But four of her grandchildren, who were little kids, the daughter-in-law was a professor in medical school in psychiatry at Stanford, and the son was a part stay-at-home dad, part-time working dad. They were living right at the edge of the campus border. So we moved back to Stanford to be near her grandchildren. George Shultz and Bill Perry were very eager to have me return to Stanford. And Bill Perry, who was the head of my advisory board, asked, "Would you mind if George and I talked to the president of Stanford, John Hennessy, to tell him how important it is that they try to get you back?" And I said, "No, go right ahead." And so, they did.

And so, the president and the provost separately told me they wanted me to come back to Stanford. I told them, "Your life is going to be really easy. There will be no counter bid. I'm not going to ask Berkeley to make a bid.” The Provost asked me about start-up funds. I said, "Well, I don't know whether I will have any new ideas.” I continued doing research while I was at the DOE, but it was on stuff I'd already started, and we were still writing papers. But I wasn't starting anything new. And I said I wanted to start new things because if it's the same old things I was doing before joining the government, it's not worth it. So I told the provost, "How about this? I don't know if I'm going to have any new ideas, but if I do, will you help?" Now, some of my friends were saying, "They're willing to set up an institute around you. You can ask for $10 million." And I said, "I'm not going to do that. I just want to know whether I can come up with new ideas." And the provost said, "Yes, we can do that.”

Then, I wrote him a little note after and said, “Maybe I will need a little bit of start-up funds. Maybe a quarter-million dollars." I didn't realize how expensive things had gotten. Stanford gave me a million, which is still less than they give assistant professors. When I returned, I had nothing. No students, no funding, and didn’t get lab space for a year. So, all I could do was sit around and think. Soon, a lot of ideas started coming. And so, in the end, it was fun to do nothing but think, and soon ideas came. Now, we have a flood of ideas, many more than I can do. I got some Moore Foundation funding and some seed grants from Stanford, so I still have a lot of my set-up money. I just got a Chan Zuckerberg CZI seed grant, have a shared NIH RO1, and I am going to get another new NIH RO1 grant on more new ideas. I personally think the work we are now doing could be as impactful as the stuff I did on single molecule FRET and optical tweezers in biology, and maybe laser cooling and trapping.

So it's really exciting. And also, I am now doing research in batteries and other applications of electrochemistry. In biology, we are making new discoveries with new optical probes that we've made. I didn't know materials science, so we started to collaborate with people who are experts in these nanoparticle probes. But it turned out the probes they gave us were forming clusters, and were not very bright. We found out what was going wrong, and then figured out how to synthesize much better probes - the best probes in the world. So the answer to your question is, when I returned to Stanford, I had no idea whether there was anything left.

Zierler:

Did your vantage point as Energy Secretary serve as inspiration? While you were Energy Secretary, did you think, "Ah, that's something that I can work on when I get back to civilian life"?

Chu:

Yes, and no. First, being Secretary of Energy broadened my technical knowledge a lot. Because I was curious about many, many things. And all my career, I would be able to take little bits and pieces an assemble some new concoction. Laser cooling and trapping was little bits and pieces and some insight. Certainly, while I was at the DOE, I developed a better appreciation of batteries, what to work on and not work on. I was not interested in just writing battery papers, I was interested in really solving the problem. And as an example, you want higher energy density, more reliability, and fast charging. You want to get away from expensive materials. So that means, forget about cobalt. I did not want to do research on batteries that use cobalt, and even nickel is going to be too expensive. The other thing is, I think like a physicist, and so there are ways of thinking that are maybe different than a typical materials science/battery person.

We are now working on a lithium metal sulfur battery. We have not yet submitted it, because in takes months to do life testing. As of now, it is performing better than any published lithium metal sulfur battery in the world, and it has a chance of being commercially viable. The same new idea of how to let lithium ions to pass through with very high conductivity but blocking the sulfur completely could also be useful for desalinization, and lithium mining. Early on, my first battery paper introduced a material that would be assist the thin film called the solid electrolyte interfase, of SEI layer. Lithium's very reactive and automatically forms this SEI layer. In recharging a battery, lithium ions in the cathode part of the battery are driven to the anode by adjusting the electric potential between the andoe and cathode. The applied potential breaks the very weak chemical bonds between the lithium and the cathode material, and the lithium is driven bring to the anode. During the discharge cycle, diffusion allows the lithium to rejoin the cathode in an energetically lower state. That's how lithium batteries work.

If the anode is all metal, instead of the graphite lithium metal anode used today, there's no “overhead” of additional materials the add volume and weight. The problems is that for a pure metal anode, if there is a surface irregularity, and the local voltage is higher at this point. The bump would grow into a dendrite, and there is a run-away effect and the dendrite grows towards the cathode until it short circuits the battery. The idea is if there is a very hard, high Young's modulus material that allows lithium ions to pass freely through it, but is strong enough to prevent dendrites from going through the material, it will prevent dendrite formation. The material needs to be much stronger than the SEI layer that naturally forms. That was our approach to a first paper published in 2014. In the first work, we fabricated a thin amorphous carbon. What we are working on is to use a two-dimensional materials, boron nitride. The material is comprised of multiple layers, can be mass produced.

By treating the material, we found it can have amazing lithium ion conductivity. In one demonstration we found we can cycle lithium metal with world record coulombic efficiency for hundreds of cycles. However, not all of the small test batteries preform as well and we need to understand the cause of the variability. The same technology could perhaps be used to separate lithium ions dissolved in salty water from the much more abundant sodium, and other ions. The hope is that an electrostatic potential would drive the ions through the material, but the holes are too small to allow sodium and other ions to pass through while allowing the lithium to squirt through.

We are now trying to think of how to apply some of the optical microscopy methods that biophysicists have pioneered in materials science. Materials scientists don't generally use single molecule, super resolution optical methods in their work. Optical methods allows one to look in the wet chemistry environment and see what's really going on. So I bringing a bunch of tools I use in biology into materials science. This work had nothing to do with my time in the Department of Energy. These are examples of what's happening in my lab.

Zierler:

What are the scientific ideas that you see as patentable? How do you know a patent when you see one?

Chu:

Well, we have a couple patents. Since 2015, there are about 15 patents and patent applications with my name on it. The lithium membrane idea should be patentable. If it turns out to help extract lithium from sea water, that would be patentable. Another area I worked on is how to improve the electrolysis of water to make hydrogen. Another patent had nothing to do with my research at Stanford. The idea started in a conversation with a friend of mine who started a company to miniaturize PCR testing. His original application as inexpensive, 15 minute test for venereal diseases. More recently, his device received emergency approval for COVID testing.. The fundamental new thing is that in a PCR test, you have to heat up and cool down the sample to allow the multiplication of the nucleic acid sample. If you miniaturize the device, the heat-up and cool-down process can be very quick.

And so, it's a micro-fluidic device. Actually, I got my name on one of those patents for an idea to make miniature heat exchange better. But in 15 minutes, the accuracy is as good as or better than the standard lab PCR test. Ultimately, each stand-alone device can be $10. It is battery-powered, and the user can tell if the test is positive or negative by a color light indicator. Since it uses PCR, it can detect whatever virus DNA you want. And it can be made even better with further miniaturization.

I got my name on another patent invention to develop a safer way to perform colonoscopies. So there are a couple patents that have nothing to do with my research, but they'd happen to be in conversations with people. In those conversations, and I would say, "Hey, I think there's a better way." There are three or four battery patents, and one the new nanoparticles we can synthesize. We have a patent on new ultrasound imaging, and there maybe another patent application in that area. Patent applications are a pain. I'd just as soon not do it, but I work at Stanford, and the patents may be good for the university. And there are other ideas I have that I haven't bothered patenting that would be patentable, and there are a couple more in the works.

Zierler:

Well, now that we've worked right up to the present, for the last part of our talk, I'd like to ask a broadly retrospective question, and then we'll end looking to the future. In your mind, if I can ask you to go into introspection mode and think about your contributions, do you tend to segregate out your scientific accomplishments from your public policy accomplishments? And then, where does social utility fit in with all of that? How do you think about all of these things as you reflect on your career?

Chu:

They're different. I think the scientific accomplishments are judged on what influence they made in shaping the research of other scientists and the applications that come from your research. I've helped start or move forward half a dozen fields. I can look back on that and say that I was a big part of the laser cooling and trapping work. I was a big part of the development of atom interferometry, and the precision measurements using atom interferometry. I was a big part of single molecule FRET and other single molecule methods that have become cottage industries. There are companies that have been created out of my work as well. And the stuff I'm doing now is in totally different fields. I'm hoping that we can have real impact in batteries, lithium mining and other applications.

The Department of Energy helped push me more in directions I normally would not have thought about. A lot of why I am doing is really applied engineering, instead of pushing the frontiers of physics. The public stuff, it's harder to tell. Some things, I have great satisfaction in. I think during my time as Secretary of Energy and during my time as LBNL director, I did change a bunch of careers. Especially among younger people. You can get really bright, young people to focus in an area and give their intellectual attention to that. And I see those people, such as those that started when Breakthrough Energy Ventures was first formed, about a third of them were people from the Department of Energy, some of whom I helped recruit.

Out of the people who came to the Department of Energy when I was there, virtually all of them have left. They started to leave when I left, but when Trump came, they really started to leave. They went back to universities or have joined companies, and they're going great guns. So I can see that, that some new initiatives, like ARPA-E of the Clean Energy Ministerial that were started when I was there are still doing good things. My dream was that ARPA-E funding would lead to something that is going to transform clean energy the way the internet or global positioning satellite system transformed the world. Nothing like that so far. If synthetic biology turns out to play an important role in the next agriculture revolution we need to reduce carbon emissions, I could say I helped a little bit in that. I helped in getting government funding, billions over the years for clean energy research. Since becoming a lab director and then Secretary of Energy, I gained a wide range of knowledge and experience. You're responsible for a lot of things, but you have the opportunity to stick your nose into new science and technology. You also have a better appreciation of what is needed.

More generally, I hope I helped excite young people to think about the possibilities and "What do you want to do with your life?" I think the loan program was a success. A lot of the government policies come and go, but progress in science and motivating bright people to work on the environment and a more sustainable world will have more lasting impact.

I tend to look at things I think will last. I was a big energy efficiency nut before the Department of Energy and remain a big proponent of increasing energy efficiency. There is lots of political resistance against more efficient lighting, shower heads, all the other stuff. It's funny that Trump tried to mock low flush toilets. And I have a personal anecdote. So we had a new toilet put in our home. I went and bought a 1.2 gallon flush. The standard in California is 1.6 gallons per flush. Which is a pretty small amount. Our new toilet if not one of those pressurized toilets, it is just a standard flush. The 1.2 gallon toilet works better than the 1.6 and the 2 gallon toilets. It gets people to think about it. And then, there are pressurized air toilets that work even better with less water per flush. The toilets use water pressure to compress a volume of air. When the toilet is flushed, the compressed air creates a stronger flush with less water. LED lighting is another big deal. The invention of the blue LED meant that “white lighting” is possible by mixing blue, green and red lighting. Tons of money can be saved with LED lighting.

All of my lights at home used to be incandescent light when we bought it. There were a lot of built in flood lighting in this house. I put scotch tape over some of the light rocker arm switches so the incandescent lights cannot be turned on. But every light that can be turned on is either an LED or compact fluorescent bulbs. As LEDs become made in a format that can replace the fluorescent bulbs, they are being replaced.

And so, I’m not yet doing much yet in food and meat substitutes area. A friend of mine, Pat Brown, a very distinguished biochemist, founded Impossible Foods. He called me up some time ago and said, "Steve, you inspired me. I quit my job." He was a member of the National Academy of Sciences, a Howard Hughes Senior Medical Investigator in Biochemistry, invented the DNA chip technologies. So he is a really famous guy. I said, "You did what?" He said, "Yeah, I quit. You went and worked for the Department of Energy. I don't know anything about energy. I am a biochemist, so I figured out what I can do to save the planet, which is to make meat substitutes." Which was Impossible Foods.

I recently agreed to join this company called Oatly that makes oat-based milk. There's a lot of technology in the products that Oatly makes. Unlike other board members, I have a technical background and want to help them in their research. The company was founded by nutrition biologist in Sweden, who wanted a plant-based substitute for milk for lactose intolerant people and to lower the greenhouse gas footprint by developing a milk substitute. Soy milk satisfies this need, but a lot of people don’t like the taste of soy milk. The substitute could not be based on peanuts because of allergies. Growing almonds for almond milk is too water intensive so they settled on oat milk.

And then, they figured out how to use enzymes to better break down the oats to raise the nutritional value. It is possible to engineer microbes to make a better enzyme, but they want to keep their product as “natural” as possible. I think they're going to have to modify their rule of only using naturally occurring stuff if they want to better oat milk. If one wants to make good cheese, an essential ingredient is a protein in milk called casein that is vital for the cheese fermentation. Casein if not found in oats, but you can program yeast to make casein. You can make casein in different ways and there are other companies developing plant-based sources of casein.

Impossible Foods uses soy leghemoglobin, a molecule similar to animal hemoglobin that gives meat its blood-like taste. At first they planned to get the molecules from the roots of the soy plant, but it turned out to be too expensive. Instead, they actually trained yeast to produce the molecules. They can get the yeast to grow animal hemoglobin as well, but they found out in taste tests, people preferred the other taste and the spoilage rate is slower. I didn’t ask Pat Brown.

Another science frontier is how to increase food production without using artificial fertilizers. Oatly wants to develop relationships with the farmers that grow oats around the world. I told them about a start-up company, Pivot Bio, that supplies farmers with corn seeds and microbes that enter into a symbiotic relationship with the corn that sues only half of the fertilizer. It takes a lot of energy to make fertilizer, and worse, there is fertilizer run-off since the plant does not use all of the fertilizer. That creates N₂ O emissions, and this gas is a very potent greenhouse gas, hundreds of times worse than CO₂ and even worse than methane. The microbes produce nitrogen nutrients right at the boundary between the plant roots and the soil so all of the materials is used by the plant. Ideally, if all the fertilizer is replaced by microbes, the N20 emissions would be eliminated. The goal is to develop microbes that can replace fertilizers used to grow all of the cereal grains in the world, including oats. Oatly introduced me to their technical development group. I hope I can help them.

I think younger people prefer oat milk to dairy milk. And most of the world's lactose intolerant anyway, which is an evolutionary thing. Nature wanted to make you lactose intolerant after a year or two so that you stop nursing, so that the mother can get pregnant again. [laugh] And the way you beat lactose intolerance is by forcing yourself to drink milk after nursing. Most adults don't drink milk. But there are a lot of important proteins in it. And there are a few proteins that plants don't make, which is where biology comes in. A few necessary proteins. Well, almost necessary. There are vegans and vegetarians. But a lot of vegetarians get their proteins from eggs and dairy. But like I said, cows and beef cattle come with a huge environmental cost.

So it's all very exciting business. And we're going to need it. So it's a lot of fun.

Zierler:

On that note, last question looking to the future, it would be so easy to end on a note of doom and gloom, given all of the generational, even existential, challenges the planet is facing. But let's flip that question around. For all of your work as a scientist, whether it's food security, public health, or climate change, where do you see the most cause for optimism that as a human race, we have the technical ability, economic appetite, and political will to overcome these challenges?

Chu:

That more and more people are beginning to take seriously a long-term prediction, which science has never made before. Never in the history of science have scientists said, "What we're doing today is going to affect people 50, 100, 200 years from today, and the story is not good." And not only is the story not good, in order to shift away from the present course, it requires major changes in just about everything we do. In agriculture, energy, transportation, cities, everything. And yet, more and more people are beginning to take this seriously. It doesn't hurt to have record high temperatures such as 104 F in Paris. Where I live, in Menlo Park, I go bicycling and have a thermometer on my bike computer. It was 114 Fahrenheit, four blocks from where I live. This is a crazy temperature.

Our house doesn't have air conditioning, by the way. We don't need it. You know why? Because we still have cool nights. And so, I open the windows at night to cool the house down. During the day, all the blinds on the south- and west-facing side of the house are left down. It is possible to keep the house in the 70s when it's 100 outside.

The optimistic side of me says that there are huge challenges, but they are beginning to get the attention of the world. Seeking solutions is beginning to capture the imaginations of people around the world, and hopefully, we will come up with some technical solutions. It's tough, and we are running out of time, and we are going too slowly. But nevertheless, whenever I think of some new scientific development, in the front of my mind and the back of my mind, "Can it be used to address this problem?" But more and more people are beginning to think that way, whether it's a better battery, a better this, a better that.

The realization that we've got to decarbonize agriculture and get carbon back in the soil. Capturing carbon capture from the atmosphere is essential. The people who are opposed to carbon capture but they are afraid it will be used to keep the fossil fuel companies alive are coming around. They're even maybe coming around to possibly accepting nuclear power … slowly. No one with a brains doubts that carbon capture is essential. We need to capture carbon form the atmosphere it will be hard to eliminate all green hose gas emissions. We can't capture airplane emissions. One solution is to produce biofuels or another form of sustainable aviation fuel based on captured caron so that burning jet fuel is a net zero cycle.

We need to begin to recycle more of what we used is also really important. Reuse would even be better. Biodegradable plastics is unfortunate because if people would responsibly recycle disposable plastic, you don't want biodegradable because biodegradable means methane generation which is worse than carbon dioxide. So bringing carbon out of the ground to make biodegradable plastic is bad. So think of 500-year-old wooden homes in Great Britain or the Netherlands. That's carbon sequestration for 500 years.

So we'll need complete substitution for a lot of the materials we now use. Anyway, there's a huge appreciation for the challenges. My fear is, there's still a lot of inertia in changing what we do, and to many shortsighted groups of people, they only care about their own prosperity and the prosperity of their children. But it's beginning to change, and people are beginning to ask what they can do. You can think of not owning a car, drinking oat milk, going to a more vegetarian diet. All these things move slowly, but I think it's going to pick up speed. The older generation are set in their ways. I can't get my wife to drink oat milk, but two of her granddaughters loves it, so, there's hope.

I'm pretty sure we're going to go over 550 parts-per-million CO2. Not 450. Forget about the goal of staying below 450. I'm sure we're going to need carbon capture from the atmosphere before a lot of the long-term bad stuff like the glacial melting in Antarctica happen.

Also, we don’t see all the damage we have already done because of the inertia in global warming. The cause of the inertia is because the deep oceans are cold, and the ocean mixing time is slow. The delay is a function of how much greenhouse gases are added to the atmosphere. We can debate whether there's a 20 year, 50 year, 80 year lag in the warming of the Earth. If it's only a small increase in carbon dioxide, the delay is less than if there will be a large increase. It will also take hundreds of years to reach a new equilibrium with glaciers. However, many glaciologists and geologists say we've already reached the “point of no return” because you've eroded the grounding lines in Antarctica and Greenland. Glaciers extends from the mountains down into the ocean. Where the glacier is hitting land the bottom at coastline is eroding inward. With this erosion, the friction holding the glacier from going into the sea is decreasing. With less friction, the speed to the glacial flow increases. The speed of glacial flows has been increasing to the point where the fastest glaciers are now moving at a kilometer per year.

It turns out that the melting of sea ice and the Greenland glaciers in the northern hemisphere make the North Atlantic less salty and less dense. As the water cools and descends, it's less salty, less dense, so on the return conveyor belt ocean current that goes all the way back to Antarctica is warmer, and the warmer, and that erodes the grounding line of the glaciers. So the North Pole's connected to the South Pole and the warming in the northern most latitudes actually accelerates the melting in the southern-most latitudes. So there's a bunch of other positive feedback effects we see are beginning to occur. The methane in the tundra's beginning to come out. We don't know whether it becomes irreversible, but there's concern it might unleash a huge amount of methane. We don't know what's going to happen. In the West, we are seeing crazy high temperatures and record droughts. Lake Mead behind the Hoover Dam is one-third full now. It's never been this empty since they built the dam. We are seeing worse water shortages and more forest fires.

Zierler:

But we'll start with oat milk. That's a good place to start.

Chu:

I like it. It's good stuff. And some people like the ice cream. The ice cream's good. I can't wait for the cheese, but for oat cheese, you need casein.

Zierler:

Steve, it's been an absolute pleasure spending this time with you. Thank you so much for taking the time to do this. And this is going to be an enormous historical treasure for the archive. So I'm greatly appreciative and honored that you were able to do this.

Chu:

Well, you're welcome.