Sandra Faber

Zierler:

Okay, this is David Zierler, Oral Historian for the American Institute of Physics. It is November 12, 2020. I am delighted to be here with Dr. Sandra Faber. Sandy, it's so good to see you. Thank you for joining me today. 

Faber:

My pleasure. I'm looking forward to this. Thank you. 

Zierler:

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

Faber:

Okay. It's complicated, actually. I have numerous titles. First and foremost, I'm Professor Emerita in the Department of Astronomy and Astrophysics at UC Santa Cruz, but I also hold an Astronomer Emerita appointment with the University of California Observatories, and finally, I'm a University Professor for the University of California. 

Zierler:

Indeed, complicated. What are some of the connections between these various appointments? In other words, where is the Lick Observatory within the larger UC system?

Faber:

Okay, well, Lick Observatory is now part of the University of California Observatories. That entity grew because we built the Keck telescopes with Caltech, so we weren't just Lick anymore. We had to have a bigger title. Again, we're going on now, hopefully, to the 30-meter telescopes, so still expanding there. That entity, University of California Observatory, provides all the ground based optical research facilities for the whole University of California, and there are ten campuses in the university, of which eight have astronomers. The headquarters of UCO is at UC Santa Cruz. So, you asked me how these titles fit together. First and foremost, I was an Astronomer with a capital A, which is an actual title in the UC personnel handbook. I came to Lick -- it was then only Lick in 1972 -- and had a title that was 80% Astronomer, and 20% Assistant Professor at UCSC. So, that's where the professor part comes in. Then, later, it was lovely. The university gave me a University Professor appointment, which is one of these distinguished appointments that's systemwide. 

Zierler:

When did you go emeritus? What year was that?

Faber:

I don't know exactly. Maybe five or six years ago, something like that. (It was July 1, 2013).

Zierler:

And you went emeritus from both appointments at the same time.

Faber:

I did, yeah. You do it together. 

Zierler:

When you were active, in terms of the students, in terms of the teaching, was it a real 50/50 appointment, or did you naturally gravitate toward one or the other?

Faber:

It was written in stone in the contract. I was supposed to be an 80% astronomer and 20% faculty. In practice, what this meant was that you worked more than anybody. 

Zierler:

Of course, yes. I've come to learn that about joint appointments. 

Faber:

Right, exactly. But since I've retired, I'm still extremely active. About the only thing that has stopped for me is I don't have to sit on committees or do standing administrative work for the University the way I used to do, or the Observatory, and I don't teach anymore. But I'm doing research, I'm doing outside service, I'm doing a lot of inside service, so I'm pretty busy, actually. My schedule, Andy would tell us, doesn't look that different from the old days. 

Zierler:

Physicists and astronomers never actually retire. They just go emeritus so they can get more done. 

Faber:

That's right. 

Zierler:

Sandy, we'll work up to your current interests as we develop the conversation, but I wonder if you could talk right now about the ways that the pandemic and remote work might actually be beneficial to your productivity. 

Faber:

Right. I would say, it's sort of opened a new window of collaboration. While I was Interim Director of the Observatory a few years back, I had occasion to travel on business to China. That was when the observatory was trying to start up the 30-meter telescope, and China was a partner. So, I made it a practice to travel all over and visit the astronomy departments, so I actually made a lot of friends there. As an example, I've got a distinguished visitor professor appointment at Tsinghua University right now. I'm co-chair of the Governing Board for the Kavli Institute at PKU, and I've just been asked to chair a strategic planning committee for a joint research effort between that Kavli Institute and Shanghai Observatory. So, I actually have three official appointments in China. Bottom line, people now know me there, and I expressed a great interest in just accepting students to come and work with us in Santa Cruz. We're now on our twelfth student, or thereabouts, and the pandemic is kind of perfect for this in the sense that nobody can travel. We had people who wanted to come, but they couldn't do it, so we said, "Well, let's go ahead anyway." So, I actually am part of two research groups that are meeting on a very regular basis. Like, daily, with one of them. Two of the students are in China, one is here in Santa Cruz, one is a high school student who wrote us out of the blue from Lake Oswego in Portland and said, "I'd like to do some astronomy research." So, she's part of the team. I guess, what I would say is you're extremely flexible, and you don't need appointments. You don't need to send a letter to the dean to have a visitor for two weeks, you know? I really enjoy that. It's very fluid, and I think it's working really well. 

Zierler:

As long as we can stay healthy, there's a lot of freedom and fluidity in this moment we're in. 

Faber:

That's right. For example, another thing I'm doing is I founded something called the Osterbrock Graduate Leadership Project at UC Santa Cruz in the Astronomy Department. We have lunchtime speakers, so we wanted to have people in person, and we were limited to the local offerings, but now we can ask people all over the world. 

Zierler:

Well, Sandy, I want to say, for the record and for context for our readers that our discussion today will be the third in what will ultimately be a trio of oral histories with you. So, I would direct readers to the other interviews to gain more insight about the earlier aspects of your life, as they were covered when those interviews took place. So, today, as we discussed, we're going to focus on some topical issues, so let's just jump right into that. Let's first start with the DEIMOS spectrograph. Tell me a little bit about the origins of that project and how you got involved. 

Faber:

Well, I've always been interested in galaxy formation, and with the formation of the Hubble telescope, it was obvious that a strategy was going to be to go very deep and look far back in time to follow the evolutionary process. But Hubble is really kind of a small telescope, and all it really can do is take pictures of distant galaxies. How were you going to know how far away things were? How were you going to get a spectrum -- I have an expression. The Chinese say, "A picture is worth a thousand words." I say, "A spectrum is worth a thousand pictures." It was clear that there was a crying need for an efficient spectrograph, to gather spectra of very distant galaxies. I foresaw that that spectrograph would be a partner with the Hubble Space Telescope, and that's exactly how it worked out. There was a smaller, and very nice spectrograph on Keck, but DEIMOS tripled the throughput for distant galaxies when we put it on. So, we built that spectrograph from 1992 to 2001, and then conducted the DEEP Survey, which was a survey of 50,000 galaxy spectra, the first and largest of its kind, going out to a redshift of about one and a half. 

Zierler:

Sandy, when you say you've always been interested in galaxy formation, how far back does that go? Are we talking about graduate school, the early part of your teaching career?

Faber:

Definitely, yeah. It really took root when I was choosing my thesis topic. It's interesting, I wasn't at Harvard at the time. I was residing in Washington, D.C., and I had access to a very good library at the Naval Observatory. I think I read every paper ever written on galaxies, through the year 1966. Isn't that interesting? You could do that then. There were only hundreds instead of gazillions. 

Zierler:

Sandy, what were some of the big questions in the earlier part of your years about galaxy formation? What were some of the observational and theoretical propositions about how galaxies formed? 

Faber:

Okay, great question. Could take the rest of the interview, so I'll try to avoid that. First and foremost, we didn't know what kind of universe we were in. The steady state theory was still a viable prospect at that time. 

Zierler:

Which means what, steady state theory?

Faber:

Steady state theory is the idea that the universe is expanding but does not become more dilute because hydrogen atoms spontaneously appear out of nothing to maintain the density uniform over time. Actually, that's the inflationary universe of today, except it's not hydrogen atoms. It's dark energy, or a scalar field, or something like that. In some sense, those guys were ahead of their time. I'm thinking of Hoyle and Burbidge, and people like that. In any case, we didn't know what kind of universe we were in, and therefore, you did not know if you looked out in space whether you would see a different population of galaxies. If it's a steady state universe, the universe is everywhere the same in time and space, so if you look out in space and back in time to a different time, it doesn't matter. You still see the same thing. So, you just had no idea what you would see if you got a telescope. That's point number one. Even more fundamental than that, there was no theory for galaxies. That's why I liked it. I'm always drawn to these really fundamental questions. I tend to lose interest when we know too much. Galaxies were perfect, because a few people had an inkling of a gravitational instability seeded by initial density fluctuations, but I'll tell you, as a graduate student, I never heard anything about that. I loved it because I was going into a field where nothing was known. 

Zierler:

Where were spectrographs -- the technology that went into spectrographs at the early part of your career, when did that become a viable tool for understanding galaxy formation?

Faber:

Another great question. I would say, as long as people were taking spectra purely on conventional spectrographs with photographic detectors, there wasn't that much you could do because galaxies are just too faint. So, people were studying the center of Andromeda and bright galaxies and things like that, and Hubble was struggling to get radial velocities in the nearby universe. The first breakthrough was the Carnegie image tube, which was put together by Kent Ford. He got a grant from the National Science Foundation to make a unit that you could put on a spectrograph. The front light detector was a 1P21 photocathode, I think. So, electrons were produced, they were accelerated in a vacuum tube, they landed on a phosphor, big flash of light. Then, another imaging system that got us to, unfortunately, a photographic plate. But instead of having one percent quantum efficiency, you had 20% quantum efficiency. So, there was a great gain there.

The next step -- this was so lucky for me -- was made here at Lick Observatory just as I got my appointment. That was a new version of the Ford device which was invented by Joe Wampler and Lloyd Robinson. To make a long story short, they had the initial photocathode with the electrons and so on, landing on the phosphor, but then they scanned that rapidly, before the phosphor flash could fade, with another photomultiplier. So, they had a real photon counting device, and it was called the image dissector scanner, and it revolutionized galaxy spectroscopy. I just walked in the door and it was right there for me to use. It was fantastic. I had been studying spectra using very coarse, intermediate band filters for my thesis. Suddenly, I could actually look at an elliptical galaxy spectrum and see all the little features in it. That's where the Faber-Jackson relation came from. I started taking spectra and saw that I could measure the line broadening. 

Zierler:

Sandy, what were some of the advances in observational astronomy that might have informed how DEIMOS was conceived and built?

Faber:

Well, I remember at the time thinking that there were seven revolutionary elements in DEIMOS that had never been implemented before. So, I probably can't remember all seven right now, and you probably don't want them anyway, but let me just say, off the top of my head, we had a wonderful optical designer, Harland Epps. The heart of a spectrograph is the camera, and basically, what spectrographs do is they take pictures of their slits, except there's a grating or a prism in the way. So, the picture they take is actually a band spread out into a rainbow. Basically, light is coming in, it's going through a nice little bright slit, and over here is an imaging device that we call a camera, and the camera is going to image the slit onto some detector. So, developments; optical design; the ability to make a wonderful camera using calcium fluoride. Very tricky substance. There were three calcium fluoride elements in DEIMOS, and getting them, and polishing them -- very fragile. Look away, and you can look back and it's broken, and that's $100,000 down the drain. There's a lot of tension involved in dealing with these things.

Then, there's the CCD detector. That was revolutionary. CCDs were these little postage stamps, and to service this big telescope, the Keck telescope -- as telescope get bigger, everything in the instrument gets bigger along with it. So, we needed a large detector, five inches by five inches. That had never been made before, and it was an array of eight CCDs, each one 2k by 4k. So, we had the first 64-megabyte detector ever made. There still aren't very many of them that look like that. Then, finally, the last thing that I think was the secret to everything -- CCDs have a problem. Without going into the details, what we want is something that is a photon counting device. We want something that's absolutely rock solid, calibrated and linear. The problem with a CCD is you can calibrate it by putting, say, a flat field on it, but then, if the wavelength on that pixel changes ever so slightly between the flat field and the actual object, the calibration from the original flat field is no longer valid. We were the first people to figure out exactly what that stability of wavelength had to be, and it’s mechanically unattainable without feedback. That is to say, a natural flexure in steel and glass and whatnot. As the telescope moves the spectrograph has to rotate, being at the Nasmyth focus, which would cause objectionable image motion. So, we put in a beam-steering feedback system which keeps the image stabilized. It's amazing. It images positioned to within a quarter of a pixel. That was our criterion and we just met it. So, DEIMOS is a photon counting instrument in a way that nobody had made a CCD spectrograph before.

Zierler:

Sandy, I want to ask, as a collaboration, of course, there are two elements. There's the interpersonal collaboration, and then, of course, there's the institutional collaboration. So, on the first part, who are some of your key colleagues? Individuals who were instrumental in getting DEIMOS up and running?

Faber:

Well, the idea for DEIMOS came from Garth Illingworth and David Koo. They went -- with my help, I was part of the team -- to the NSF. In like a month, we wrote a grant for $1.9 million, and the NSF actually funded it! So, the initiative came from those guys. Gradually, Garth decided that he wanted to turn his efforts to other things, and I became the PI. I was the one who dealt with the construction in the Lick Shops. At that point, that's really all the people I needed to deal with. I needed my local folks who were the engineers and the machinists and the opticians, and people like that. 

Zierler:

So, at the top level, the three of you, what is your sense of what each of you contributed in terms of your individual talents and expertise?

Faber:

Well, I think I would probably credit Garth with the driving force. Garth is very powerful and has a vision. So, I'm going to give him that credit. David stayed on the project, and he and I joined with Mark Davis to do the DEEP Survey. David's main contribution was designing the survey. Those two guys were off there wondering how we're going to do the DEEP Survey while I'm busy trying to get the instrument built. 

Zierler:

I'm always interested in hearing how scientists arrive at monetary numbers to put in a proposal. Where did $1.9 million -- why not $2.9 million? Why not $.9 million? How do you get to such a precise figure when you're thinking these things through?

Faber:

Oh, well, it's very easy. You just ask for the biggest thing you think you can get. Don't be under any illusions that that number means a thing. But it was a cost-sharing strategy. It wasn't the number for the whole cost of the spectrograph. We went to the NSF and said, "If you give us this, we will go to the Science Steering Committee from the Keck telescopes, and we have favorable information that they will say, wow, we can get this big chunk of cash up front." That, in fact, happened. On the other hand, I knew when the final proposal was going to the Science Steering Committee, I knew very well that the budget by that time was $5.5 million, and the other part was supposed to come from Keck. I knew that was not going to be enough money. I did it anyway, and the ultimate cost was $10 million. If I had said to the Science Steering Committee up front that this thing is really going to cost $10 million, they weren't going to give me the money. 

Zierler:

Sandy, I'm curious. I know this is a little bit before, but the DOE got involved in supporting astronomy and astrophysics with Ray Orbach and supporting Saul Perlmutter. This is later on. Did it ever occur to you to think about the Department of Energy as a funding source?

Faber:

Actually, the DOE was in a sense the impetus for the whole thing. They didn't actually give us any money, but why did Saul Perlmutter get money? It's because he was at Berkeley, and because Berkeley had -- gosh, maybe that's not a DOE. No, I guess maybe that was an NSF Science and Technology Center. Berkeley had a Science and Technology Center in astro particle physics. (Note added later by Faber: the UCB Center for Particle Astrophysics was an NSF Science and Technology Center. Linking to DOE was an error.) Bernard Sadoulet was the director, if you want to look into that further. They had an advisory committee, and they knew that Perlmutter was struggling to get a sequence of supernovae observations. It was very tight. He had to find and measure brightness, and then he had to persuade people to take spectra before the thing faded, and then he had to observe again to measure a second brightness. All within 60 days. So, the sequencing that he needed was completely unfamiliar to the ground based optical world on these telescopes. He was struggling. The advisory committee said to him, "Get with it. Get a plan in place. We'll support you." With their backing -- I think that was a large part of it -- he managed to get these carefully sequenced observing runs on telescopes. Now, I'm not mentioning Ray Orbach. I really think this was an NSF center. So, that's a little bit vague and maybe needs to be clarified. What did you have in mind?

Zierler:

Well, that it was Ray Orbach who was instrumental in supporting. The whole idea was that Berkeley, as a DOE national laboratory, was not in the business of supporting astrophysics. 

Faber:

Was the center an NSF center?

Zierler:

That we'll have to look up. We can clarify that. 

Faber:

Okay. Well, you've told me something I didn't know. 

Zierler:

Sandy, what about NASA as a funding source? Was that ever something to pursue?

Faber:

Not at that time. NASA has been a major funding source for me later. But NASA is not in the tradition of funding instruments for ground-based telescopes, at least then. Of course, they became a partner of Keck. They have -- is it a sixth of Keck, I think? In that capacity, they have funded specific instruments for Keck that relate to their program on the telescope.

Zierler:

Sandy, when did you know that DEIMOS was really doing what it was intended to do? What were some of the feedback mechanisms you were getting that told you were on the right track?

Faber:

We had sort of a catastrophe as we were putting it together. This happened because of my inexperience. I'd never been a PI for an instrument before, and this was the world's most difficult spectrograph to that time. I was really in hot water, and much of the time didn't really know very much what I was doing. What I didn't take sufficient care with was assembling this fabulous camera that had been designed by Harland Epps. I was kind of relying on the Shops and the engineers to do the measurements. I told them the tolerances that were needed but didn't actually stand over everybody to make sure that it was done properly. So, it was really traumatic. We finally assembled everything and took the first end-to-end pictures, and they were horrible. We were under a gun to ship at that point. We had a pre-ship review, and all I had to present were these awful pictures. But I had learned to run ZEMAX and so I could try to mimic the errors that we were seeing. I could see that probably there were spacings that were wrong in the camera. If I could get those right a second time, that would fix these horrible images that we were seeing. 

Zierler:

If you could explain, what is a horrible image and what is a great image? How do you know what's bad and what's good?

Faber:

Okay. A great image is small and tight. These horrible images had long tails that stuck out radially away from the center of the field. The farther away you were from the center of the field, the longer the tails. To make a long story short, I had to persuade the pre-ship review committee that this was fixable, and that we should ship anyway. The point was we already had a plan to disassemble the camera as part of shipping. That was safer than shipping it whole. So, it was going to have to be reassembled in Hawaii in any case. So, we went to Hawaii, Drew Phillips and I, and this time we had a plan. We were much more careful when we put it together. We measured everything very carefully. The moment I knew that DEIMOS was going to be a fabulous success was when we tested that camera and got perfect images. I'll tell you, that was a big day in my life. That was a day. 

Zierler:

Sandy, depending on where you set it up, maybe this was early on, were there any early signs that there might be troubles in Hawaii in terms of tribal land and all of those controversies that would come later? Were there any indications that this would be part of that?

Faber:

Yes, there were. I don't think I'm a very good person to give you chapter and verse, but already, we were certainly -- in creating the telescope, we were riding on the coattails, both good and bad, of previous telescopes that had been constructed on the mountain. We took considerable care -- I think in retrospect not enough, but we were better than people before us -- to court and try to get good relations with the local folks. Keck, I think, has had an admirable record in hiring local people, for example. So, there was a realization that we needed to maintain good relations, and we were worried about that. Now, later -- when did this happen? Keck applied to build outrigger telescopes that would have created an interferometer system there with six smaller telescopes around the two big telescopes. Beam combining gives you much higher optical resolution. That ran into a buzzsaw of opposition from local people. I think that was their great victory. That was when they really showed, with clout, that they could stop something major on the mountain. That was a precursor to everything has followed since. 

Zierler:

Sandy, from that heady day when you knew that the pictures were good, and amazing things were going to happen, I wonder if you can develop -- once you started to get really good pictures and you knew that understanding galaxy formation was really going to come substantially better, I wonder in what ways DEIMOS confirmed things that were only presuppositions up until that point, and what did you learn about galaxy formation that raised new questions that you didn't even know to ask before?

Faber:

Okay. So, in parallel -- this was covered in previous interviews with me -- I was part of this group that's really headed by Joel Primack. We wrote this paper in 1984 which kind of laid out a menu for how galaxies would form from cold dark matter. DEIMOS was finished in 2001. That's when we started the DEEP Survey. Between 1984 and 2001, a lot had been done, including by Hubble. We had the first photo z’s from Hubble. So, we knew already that we were well on the way to confirming that 1984 theory. Nothing really horrible and objectionable and emerged in that intervening time. So, when we started to use DEIMOS, the focus by that time was to understand more of the details of how the visible parts of galaxies were forming within halos. So, our menu was just to measure basic parameters. We wanted, first of all, to get the redshift much more precisely than a photoz. We wanted to use those redshifts to get better-calibrated photoz’s for all the other galaxies. We wanted to measure the distribution of galaxies in space and measure correlation functions.

The last big thing that I was engaged in, I became very interested -- always been interested in elliptical galaxies. How do spiral galaxies go from forming to stars to being quenched, red, and dead? So, one of the major achievements with DEEP was counting the ratio of star forming to quenched galaxies as a function of time. You could see the quenched galaxies were increasing. It just established that there was a flow of galaxies whose star-formation was going out. So, spirals would move to being quenched to be replaced by new spirals, growing underneath them from new matter perturbations. So, that emerged very strongly. Finally, the last big, big discovery was something called the star-forming main sequence, which is one of the most cited papers from the DEEP Survey. The first author is Kai Noeske. That established the star forming galaxies populate this very narrow sequence of star-formation rate as a function of mass. So, if you know the mass of a star-forming galaxy, you can predict its star formation rate. We could see the normalization of that evolving with time. By the way, the name "star-forming main sequence" was my idea, and I think it helped to sell his paper because it made the discovery a more memorable concept.

Zierler:

Sandy, what were some of the sub-fields in physics, astrophysics, astronomy, cosmology, that you felt were most important in terms of conveying the findings of DEIMOS? What were some of the key conferences or journals that you felt here's where colleagues more broadly in the field need to understand what we're finding?

Faber:

Well, we went to all the usual conferences in galaxy formation in cosmology. That would be the reporting venue. I had always published primarily in the Astrophysical Journal, so most of the papers that we published appeared there. 

Zierler:

In what ways did the findings relate and help inform even bigger questions about the universe? What would you say to that? In other words, if we understand how galaxies form better as a result of DEIMOS, that also helps us understand what? Does it help us understand dark energy, dark matter, the origins of the universe? What are the broader questions beyond galaxy formation that help us understand these things?

Faber:

Okay, well, let me just say that at this point, maybe your question hasn't been totally clear to me. I've been telling you the results of the DEEP Survey, but DEIMOS is a public instrument, so it's been used by many other cosmological surveys. I think one of the major uses has been to study dwarf galaxies. Dwarf galaxies are a place where there's some conflict, potentially, with the cold dark matter theory. (Note: CDM is the name of the theory of galaxy formation that was described in the Primack-led paper back in 1984. – Blumenthal, Faber, Primack, and Rees, Nature, 1984.) That has led people to contemplate different kinds of dark matter. In particular, self-interacting dark matter has been proposed in order to account for the observations of these dwarf galaxies. So, that's one thing that occurs to me right away. Then, of course, along about 2000, but confirmed much more strongly since then, is the use of supernovae to calibrate the amount of dark energy in the universe, in other words to get a very, very accurate measurement of the rate of expansion as a function of time. Many spectrographs have contributed to that, but Saul Perlmutter's work helped to win him the Nobel Prize, and he observed with DEIMOS in order to take those observations. So, there have been many impacts overall. 

Zierler:

Sandy, what are some of the universal truisms that are applied to all galaxies in terms of how they're formed, and what are some things that you've learned that may be unique from one galaxy to another?

Faber:

Well, I think we're still struggling with the basic question of what are the numbers that you need to characterize a galaxy? This way of thinking about astronomical objects has sort of been a theme for me ever since I started. For example, I'll give you an analogy. Here's a star. What do you need to know about that star in order to more or less completely predict what it does? You need to know its mass, and you need to know its age. You need to know its composition, and you might need to know something about its rotation speed, and so on. But there are a small number of numbers that go into characterizing a star, and all the complexity of the formation, the swirling gas clouds, the mass of the – memory of all that is lost in formation. Finally, you make the object, and the beauty of stellar physics is that you forget all the original stuff that was complex. You wind up with a simple object which is describable with just a few numbers. When I went into galaxies, I asked myself -- and this is back in the early '70s -- do those principles carry over? Do galaxies forget their formation and somehow a new set of physics takes over? God giveth with one hand and taketh away with the other, okay? If you forget your origins, it means that studying your present is easy. If you remember your origins, it's more complicated, but on the other hand, by studying the present, you might learn about the origins. I don't think I've ever heard anybody say that about galaxies, comparing them to stars in quite that way. So, I think your question for me reduces to how many numbers does it take to basically explain a galaxy, and to what extent do those numbers -- are they embedded in the original conditions, or separated from the initial conditions?

Zierler:

Sandy, to add further complexity to the question, to what extent is there a historical chronology that might make the answer a little more complex? In other words, there are galaxies that were formed billions of years ago, there are galaxies that are forming today, and presumably, there will be galaxies formed billions of years into the future. Are those timelines relevant --

Faber:

Maybe less than you think. 

Zierler:

Maybe less than I think. Can you explain that a little bit in terms of the broader history of the universe in early galaxy formation versus current or future galaxy formation?

Faber:

Absolutely. Before the Blumenthal paper, I was actually dabbling in theory myself, and I said that there were two numbers that would characterize a dark halo, which we were just beginning to learn about at that point. The year now is 1982, two years before Blumenthal. Two numbers: one would be the mass of an early density fluctuation, and the second number would be its over-density at a particular epoch. So, the mass then would make the mass of the halo now, but the over density would tell you how quickly it would collapse. If it collapsed sooner, it would collapse in a denser university and be small and dense, and if it collapsed later, the opposite would be true. Guess what? Galaxies are a two-dimensional family, while star-forming, anyway. So, we see today a suite of objects that have different masses and have different radii. I believe that in some way that early paper is telling you how the density fluctuation and halo conditions map onto the structure today. That's what I'm working on right now. I'm trying to establish that the second parameter in galaxy structure, which is their radii, actually derives from the initial over-density of the fluctuation. 

Zierler:

Sandy, what flaws or limitations, perhaps, exist in DEIMOS, that might inform the next generation of research endeavors in this field?

Faber:

I think DEIMOS, in fairness, has been surpassed now by the next generation of spectrographs. 

Zierler:

Is that simply a matter of technological innovation, or was there some problem inherent in DEIMOS that's been solved in the next generation?

Faber:

I think we did the best we could with what was available, but I think the big breakthrough now is VPH gratings, which enable a different optical design that enables you to get more resolution from smaller elements. So, MUSE on the VLT is a fantastic collection of spectrographs, and something similar is KCWI, which is a smaller version of MUSE that's gone into operation at Keck. Both of those spectrographs really specialize on minimizing scattered light, and they both use VPH gratings. They're just wonderful instruments. I've, unfortunately, never observed with either one of them. 

Zierler:

Let's move on to Hubble. It's such an interesting story to get the broader perspective on who was concerned when with regard to the optical flaw. First, let's just build that context in terms of in the development phase, what was your part in this project?

Faber:

I came in pretty late. I was asked by Jim Gunn to join the Wide Field Planetary Camera team, and I think the year for that was 1985. The telescope was due to be launched in 1986, but the Challenger explosion delayed that, and it didn't go up until 1990. So, why did I come in? They didn't invite me in in order to build the camera. That was already going on at JPL.

Zierler:

Had you collaborated with Gunn previously?

Faber:

No, we were just friends. So, the Wide Field Camera had a science team, and the team was going to get 300 hours of observing time on Hubble, and Gunn thought that it would be helpful if I came in and helped the science plan. So, I listened to a lot of meetings about building the camera but didn't have much to do with that specifically. I learned a lot about it though, which was a good thing, because when the telescope was finally launched and in trouble, I found myself being the principal person on site in Baltimore, trying to make sense of the reports of the thing not working. So, I could just go on there a little bit.

Why did our team have anything to do with what was going on in Hubble? Well, all the instrument teams met on a regular basis at the daily project meeting at Goddard Space Flight Center. There would be reports from various parts of the project, and you would hear that such-and-such wasn't working, that a measurement was supposed to be taken and it made no sense, or it was obvious that the telescope wouldn't point. See, the telescope actually had two problems. The optical problem, but also the solar panels that the Europeans had built changed shape abruptly when the telescope went from dark to light around the Earth's orbit, or from light to dark. So, there'd be a glitch kind of, a bi-metallic strip effect, and then the solar panels would flap, and the telescope would wobble as a result. It took them several weeks, actually, to control the system before you could even take a sharp picture. So, that was one delay. 

Zierler:

So, there was indication early on that there was an issue, even before it was up and running.

Faber:

Oh, you mean on Earth? Oh, that's the famous story of the optical team. I think it was five guys at Perkin Elmer. They had been testing the primary mirror with a provisional, interim test optic. Then, when they put in the final test optic, the surface looked drastically wrong. They didn't pause to try to find out why that was, and it was because the second test optic was mis-assembled. Yes, there were people in that little team who were convinced that the mirror was no good. But the leader of that team did not share that information with higher ups, as far as I know. Can you pause just a moment?

Zierler:

Please, take your time. 

Faber:

Okay, so, where were we? You wanted to know if there were indications on the ground. Yes, there were indications on the ground, but they weren't shared with anybody who could do anything about it. 

Zierler:

Meaning that if these were better publicized, they might have delayed the whole project?

Faber:

Yes.

Zierler:

And should it have delayed the whole project?

Faber:

Yes, that's right. 

Zierler:

I mean, silly question: would it have been --

Faber:

No, let me be fair. Just a minute. It depends on when the attention was paid. What happened, as I said, they had been polishing along with this provisional device. Then, they put in this new test optic. The new test optic goes between the light source and the mirror. So, light comes from a very small light source, goes through the test optic, hits the mirror, comes back, goes through the test optics in reverse, and comes back. If it comes back to a point, you know your mirror is okay. If you've got a bad test optic, your mirror is going to compensate for that and its surface will be wrong. Now, supposing the opticians, when they put in the new test optic, they said, "Whoa, something's not right here." They probably within a month could have figured out what was wrong, because in retrospect, it was obvious how the test optic had been mis-assembled.

That's a wonderful story in the Lou Allen report. Gosh, if you haven't interviewed him, you should certainly do that. A wonderful report. I think it would take us too far afield today for me to tell you what's in it. But the net result was that when these folks tried to assemble it, it didn't fit right. They went down to the hardware store and had to buy washers to make something fit. Now, look, you're making a so-called "space qualified device" and you have to go to the hardware store because something -- I mean, what are you thinking? Or not, as the case may be. So, if they had gotten with the program at that time, it probably could have been a quick fix with essentially no delay. But then, later, after they figured in the wrong mirror, it would have been years in order to figure it back again. 

Zierler:

When did you realize that something was seriously wrong, and what was the game plan?

Faber:

Okay, I take credit for this. I had been going to the daily Project meeting at Goddard Spaceflight Center for days, listening to the people from Perkin Elmer complain that somehow their optical assessment wasn't working. These were smart people. The team was led by a PhD optician from Perkin Elmer. Thier device, on the telescope, was an interferometer. It didn't take pictures. In retrospect, we know why it didn't work, because it was assuming -- it was sort of success oriented, and it assumed that the telescope would be correct within some narrow margin. So, it didn't have much dynamic range. In fact, the path differentials were enormous from one side of the mirror to another. So, there was just no way that device could tell you anything. Furthermore, because it was so far off center, the slightest little perturbation of the mirrors would change the readings completely.

So, they came in day after day, getting different numbers and none of them made any sense. Okay, meanwhile, there are reporters out there, you know, and the world is waiting. What's going on with Hubble? The tension was high. So, the Project decided that it needed to take a picture and have a press release. So, with great fanfare, this picture was arranged. I think the star was Iota Carinae in the Southern Hemisphere. I actually wasn't on site at that moment because I was observing at Palomar, but one of the members of our team, Roger Lynds, looked at this picture. It was taken with our camera, the Wide Field Camera, and it didn't look right to him. It had a small point of light at the middle, but then it had a little halo. They published it in press releases, and they, I think deliberately changed the stretch so that you could only see the small point of light, and you didn't see the halo. It was somewhat dishonest. But we who owned the camera and had the electronic image in our computers, could manipulate it. We could see what it really looked like.

The next day at the Project meeting -- again, I wasn't there -- Roger Lynds spoke up and said, "I think this telescope has spherical aberration." That's a common problem in ground-based telescopes when you have secondary mirrors and primary mirrors. If their curvatures don't match, then the basic aberration that emerges is spherical. By the way, I knew nothing about any of this. I knew nothing about optics. Spherical aberration, I barely knew what that was. Anyway, the Project leader, a nice guy named Joe Magner, spoke up to Roger Lynds. He was leading the meeting, Joe was, and said, "I don't want to hear that now. It's too soon to come to decisions like that. We have a lot of work to do." Kind of a reasonable Project Manager statement at the time, but Roger was wounded. He's a sensitive guy. He sort of crawled off and said, "If you don't want my advice, I'm leaving." So, that was bad because he was one of the most knowledgeable people on my team. 

Zierler:

Was that a legitimate response? Was he correct in feeling his advice would not be valued?

Faber:

No. These projects are big projects. They have bureaucracy. They have ways of doing things. You can't expect some astronomer coming in from the side just to have everybody listen to you. What do you know? These people have been spending years training for this moment, and you pop up in a meeting and say something horrible. They want you to go away. At least, at that moment they do. Anyway, I returned from my observing run at Palomar. I looked at the picture and could see it was a problem. Spherical aberration is being discussed in the Wide Field Camera team by my colleagues.

Then, about that time, the Project decided to take another picture. This was the key one for me. They took a picture of a star cluster named NGC188. It's not a very dense star field, but it was enough to put stars in all four quadrants of the Wide Field Camera. They didn't expose long enough, unfortunately, but it was just enough to show me that there were symmetries in the optical errors. These symmetries were symmetric within each quadrant of the camera. So, there'd be two stars in this quadrant and two or three stars in that one. If you somehow superimposed all the quadrants, you could see that in fact, there were these kidney shaped things that poked out away from the center of each of the quadrants. I showed this image to my colleagues on the Wide Field Camera team, and they didn't believe me. They were unimpressed. That's because the exposures weren't quite deep enough. But I thought I saw something there that was systematic. I didn't understand it. I didn't understand why there were these tails poking out from the center of the field. I barely even knew how the optics worked of the camera. But then I was on a crusade. I had to get the Project to actually steer to a bright star and put it in the center of one of the cameras and expose deeply. That took several weeks, actually, to accomplish that because we didn't know how to point very well. There were some false tries.

Then, finally, we got this, and it was Iota Carinae again, this really deep image, and you could see in all of its glory all the problems of the telescope. The bright center, but the huge halo, and lots of diffraction-caused features all over the outer fan and so on. And these tails that had been aiming outwards from the center were caused by the fact that there were obscurations within each one of the quadrants that were obscuring part of this whole image. You only saw the whole image if you put a star in the middle of one of the quadrants, which is what we did. 

Zierler:

Sandy, I want to go back to a comment you made before. It's quite true that with Hubble the whole world was watching. There is that general sense that with Hubble there was somehow this really deep and broad public interest in what Hubble was setting out to do. Can you explain, from your perspective, why there was all of that anticipation around Hubble. What made Hubble different, at least in the public perception?

Faber:

Well, you probably ought to interview people from the public in order to figure that out. I guess, probably several reasons. First of all, it was very ambitious. So, people were on tenterhooks. Would it succeed? It was an American project, so Americans cared deeply. Our reputation was on the line. There had been controversy for years in Congress. Congress had almost killed the project a few times because it was running over budget and it was expensive, so Congress was watching. But then there's the point that there is a segment of the population that just loves astronomy. We were promising beautiful pictures. It was like candy. So, great anticipation, and we also said we were going to answer some of the major secrets of the universe at the same time. So, put those things all together and it was a recipe for pressure and anticipation. 

Zierler:

Were there any days or moments when the optical flaw felt like it might doom the whole endeavor?

Faber:

Yes. Before moving on with that, I have a little story to tell about the optical flaw. 

Zierler:

Please, please. 

Faber:

After several weeks, we managed to coax the project into taking these six exposures, moving the secondary mirror through focus. This was Roger Lynd's test. This is how you discover spherical aberration on a ground-based telescope. You move it through focus, and you see this characteristic pattern in the image shapes. So, as it happens, the last image to be taken in the sequence was called the smoke ring image. It's paradoxical. It's an image in which there's no light at the middle. It's a donut! As it happened, that day it was my job to go over to Goddard and pick up the magnetic tape that had this image on it. I walked into the control room at Goddard, and the astronomer on duty there said -- they were looking at the image on a TV screen, and he was baffled. "What in heck is this?" Well, by this time, our team was making calculations of spherical aberration and we had expected that this image was going to be the smoke ring. So, I said, "Oh, well that's the smoke ring for spherical aberration." He said, "You understand this?" I said, "Yeah, our team has been making calculations." He said, "Could you go down in the basement and talk to the people from Perkin Elmer?" So, I did.

By this time, I knew them, and they were sitting at a long table. The leader of the team was closeted with a couple of his assistants, and I walked in. It was a little awkward. Why was I there? Sort of, "Hi, how are you? How are things going?" And he said, "Have you seen this?" And so, I came over, and he had a drawing there. I said, "Sure, yeah. That's the smoke ring for spherical aberration." You could have heard a pin drop. So, he wanted to see an illustration of this. I start sketching with wobbly lines optical rays on a piece of paper and demonstrate to him how, at this point, you can get this circular image. Meanwhile, the chief optician for the Project, a NASA employee, was at the other end of the table, and he was sitting with another Perkin Elmer employee. He and I had been discussing spherical aberration by this time. So, we invited him into the conversation, and he reaches into his pocket, and he brings out a beautiful piece of paper drawn on the computer with exactly what my fumbling sketching had been trying to do. He lays it out, and now it's clear, it's elegant, and so on.

Well, the Perkin Elmer people were completely stunned. It thought it was probably better just to leave them alone for a while. So, I exited, and my friend, the chief optician from NASA went with me. We're walking down the hall, and I said, "How come you weren't telling them? You had this piece of paper in your pocket. You knew." And he said the strangest thing to me. He said, "I was waiting for you to show up and tell them." But he didn't know that I was coming, so that response meant nothing. But I've always remembered that remark because what it really meant was, he did not want to be the messenger of this bad news. So, here I am. I'm coming in from the University of California. I have no professional stake in this. Whether or not I get promoted doesn't depend on what I say, but for him it was a different matter. He had gotten the message that NASA shoots messengers with bad news. If you have bad news, you don't share it. So, that's an insight into the workings of the Hubble Project at that time. Of course, it was the same thing that had led to the explosion of Challenger. It was the same thing that led to a bad mirror on Hubble. When it came my turn to lead the DEIMOS project, which I saw as being very difficult, I just had it burned into my head at that time that as a project leader you must create an atmosphere in which people feel rewarded for coming and telling you bad news. You will never know at grass roots level what's really going on yourself, and if your troops don’t tell you, it could be a disaster. 

Zierler:

You're earning in real time an amateur degree in organizational psychology. 

Faber:

Absolutely. That's right. 

Zierler:

So, Sandy, let's get back to that question about some of those dark moments where perhaps the optical flaw felt like it was an existential threat to the whole program. 

Faber:

Well, you're reminding me of the night after the press conference was held. So, to make a long story short, the six images came in. Our team was analyzing them. We came in with a pair of graphs: the real images and our synthesized images using software from Space Telescope Science Institute, match by match by match by match by match. We told them what the spherical aberration was within a few percent. Okay, so, there was that traumatic project meeting in which we shared our results, and to NASA's credit, two days later they had a press conference, and they announced the flaw to the world. That evening, our Wide Field Camera team -- see, our team was on site for weeks and months at a time, so we were eating dinner together every night. We'd all go out as a group. That night we were at a Chinese restaurant, and we made a whole list of things that were going to be a catastrophe in science as a result of this failure. That night we didn't see how it was going to be fixed. We thought this might be the end of NASA, we thought it might be the end of American astronomy. We spun all kinds of really dreadful scenarios. We were feeling very blue. 

Zierler:

How did you get beyond that? How did you not feel so blue, and feel hopeful that this was actually going to be okay?

Faber:

Well, it sounds like I'm giving a lot of credit to the Wide Field Camera team, but actually, two things then happened in the team. Thing one was contributed by my former graduate student, but by then a staff member at NOAO, and that's Tod Lauer. He's a genius with manipulating images, and he began to experiment with Lucy-Richardson deconvolution, which was a software tool that could be applied to Hubble images to basically stuff the light back down into the point spread function and correct the spherical aberration. Within a day or two, he had made some test experiments with images to show that with bright objects, that actually would work. That meant that the telescope could do something useful in the meantime, and kind of show its promise, not on faint things but on bright things.

Then, it was also realized that when they built the Wide Field Camera, the one that was up on orbit, they made a clone, just for emergencies in case somebody dropped that one or something. They had actually built two of them. The guy out at JPL who was in charge of the clone said, "Look, I can change the optics on the secondary mirrors in this clone, and we could install that. I could do that quickly." So, it was that twin announcement within just a few days or weeks -- I forget the timing exactly -- really upped people's enthusiasm. So, now there was a known fix for the main camera on the telescope, and that inspired Space Telescope Science Institute to convene this blue-ribbon advisory committee, which wrote a report on ways of fixing the Hubble Space Telescope. there were 50 different strategies in this report, and ultimately the ones that were chosen -- trouble is, there are five instruments. You have to fix all five. So, fixing the clone would work for the Wide Field Camera, but there were four other instruments that also needed to be fixed. And then Jim Crocker came up with this clever idea of putting little mirrors in front of the apertures of the other four instruments that would fix them as well. So, by the end of the summer, it was clear that maybe this actually could be accomplished without bringing the telescope back down. Nobody wanted to do that, especially for contamination reasons. 

Zierler:

Sandy, of course, today, everybody continues to marvel at how successful Hubble continues to be. Did you and your team have any sense that once the optical flaw issue was addressed that Hubble would, so many decades later, continue doing wonderful things?

Faber:

No. I think nobody had any sense of the lifetime. We were all working to a ten-year lifetime, and that's why losing three years at the beginning seemed very bad. 

Zierler:

I wonder if the experience of dealing with the optical flaw in real time actually lengthened the viability of Hubble in some way. 

Faber:

Well, I think it, in the end, hugely increased interest in the telescope. I described the fact that we felt we were in a pressure cooker and everybody was watching. But the flaw, the failure, and then the recovery became a story of mythic proportions. So, the public focus on Hubble after the fix was much greater than it ever would have been without the flaw. So, in the end, Hubble's legacy in history, and the number of lives it's touched, really is much greater because it started out as a failure. This is my opinion. 

Zierler:

And you emphasize that this is your opinion because perhaps some do not agree with you?

Faber:

No, because I've never actually asked anybody out in the public. Do you think you care more about Hubble because it almost died? I just sort of suspect that that is true. 

Zierler:

Yeah, that's a very interesting observation. What were the origins of the CANDELS project for Hubble?

Faber:

Well, as I've said, the impetus to build DEIMOS came from Hubble pictures, but the field of view of DEIMOS was huge and covered enormous areas of sky. The pictures that Hubble had been taking to that time were these tiny little postage stamps. So, here's the Hubble picture and the DEIMOS slit was four or five times longer and was getting wasted – it wasn’t filled. So, I felt a huge impulse to string together Hubble pictures on the side to take full usage of the full DEIMOS slit length. That was my impulse. I put in two Hubble proposals to [unintelligible] large areas of sky that failed, and then finally wrote this third proposal in which -- see, fiefdoms had arisen in the meantime. I think this happened because of improper management by Space Telescope Science Institute. So, people were realizing that to really understand galaxies, you have to have observations of the same field all the way from X-rays to radio. Wonderful as Hubble is, those pictures by themselves don't answer all the questions. You add a spectrum from DEIMOS, well that's all very well, but you don't know anything about the infrared. That's where the signatures of star formation are occurring. And AGN emit X-rays. So, you really needed a soup-to-nuts data scheme over all wavelengths.

So, a race was on in which various groups around the world would choose their patch of sky, and then try to bring all of these resources to bear on it. I think the reason why my proposal succeeded was that it didn't just look at the fields that we had been building up with the DEEP Survey. It stood back and it said, where are the best fields that are the most developed with this pan chromatic data over the sky, and let's propose those. And there were five fields. Two of them had been looked at already, the so-called GOODS fields, which were the first extended fields imaged deeply with Hubble. You probably know the story. GOODS put in a proposal to only look at their fields, but more deeply, and the review committee on the time assignment committee said, "We see virtues from both of these. Maybe we should put these proposals together." It had never been done in the history of Hubble, because they feared that PIs couldn't get along if they tried to merge proposals. I was in charge of my proposal, and Harry Ferguson was in charge of the GOODS proposal. We're both kind of known as reasonable people. So, for the first time, they said, "Maybe these two people could make a joint project." I got called by Matt Mountain, director of Space Telescope at the time, who said, "Would you be willing to collaborate with Harry?" And I said, "Of course." – this was the gift of a lifetime, and Harry said exactly the same thing about me, and so that's how the project finally came together. 

Zierler:

What were some of its major achievements once it was together?

Faber:

Well, it's the biggest single project that's ever been done on the Hubble space telescope. It took 903 orbits all together. It was a blend of galaxy imaging together with trying to capture those supernovae. So, I'll speak about the supernova results first. Basically, CANDLSS showed that we'd run out of supernova – you could not find them in large numbers even further back in time that had already been probed. That, I think, was a definite result, probably a little disappointing to the supernova team. They did not, as a result of our pictures, really extend their reach back in time or significantly tighten the cosmic parameters that they were trying to measure. Now, on the other hand, the general imaging data are being used everywhere. I think there are 500 papers now that had been published that cite the CANDELS survey. (Note: as of 12/15/2020 1700 refereed papers have cited CANDLSS.) Anything you want to do with distant galaxies, the first thing you do is you go to the CANDELS fields and you look at the properties of galaxies in our catalogue, which is all public and everything. So, JWST will not take any of those images. It doesn't go to blue wavelengths the way Hubble does. Those are going to be the images for decades that we have of the universe. That's a great legacy to leave. Now, as far as discoveries are concerned, what have we learned? Gee, everything I know about galaxy evolution comes from the CANDELS pictures. 

Zierler:

What were those pictures able to demonstrate or to reveal to you that wasn't possible before?

Faber:

Quantity. Just the number of objects that you could put in a plot went up by a factor of ten. So, you might have had glimmerings of trends with small samples before, but now suddenly you could put dozens of objects in a single plot. You need to slice by mass, and you need to slice by redshift. Within that, there are other things you need to slice by. Star formation rate. By the time you dissect the galaxy population in all of those parameters, you don't have very many objects left in a bin. So, the large sample has been a huge, huge help. So, you just string the pictures together. You make plots, and you can just see these beautiful evolutionary trends. There is a story there. We don't know the whole aspect of it, but it's clear that galaxy formation and evolution is an orderly process. Coming back to my original statement a few minutes ago, two parameters. I think there might be three, but basically, it doesn't take very many parameters to characterize a galaxy, I think. I'm not done with that yet, and maybe we can talk about that in current work if we get to it. 

Zierler:

Yeah, let's jump into that right now. We've touched on that already a little bit but given that you are currently this year not only working on this but presenting these issues publicly. You're conveying these things to a broader audience. What are some of the key items of consideration that you want to convey in terms of what the field knows, what problems have been solved about galaxy formation, and what remained outstanding, and how those outstanding problems are very different from what they were twenty or thirty years ago?

Faber:

Okay, so it's interesting that you say that because that was the title of a talk that I gave at the Subaru 20th Anniversary. You might have just read my abstract there. Did you?

Zierler:

No, no. I didn't. Full disclosure, I did not. 

Faber:

Yeah, “Galaxy formation: What problems are solved and what problems remain outstanding?” That's the title. So, I've been trying to put together a simple theory, which I hope explains everything soup to nuts. It starts with a picture of dark halos. We really understand dark halos very well because we can model them -- forget the baryons. We can just put in gravitating particles, dissipationless particles. The power of modern computers is such that we really have a wonderful story about dark halos over a very large dynamic range. So, assume that we know everything about dark halos in the universe. Where they're located, their sizes, their radii, etc. How they cluster. My picture takes -- by the way, that comes out of Blumenthal, 1984. Before that, White and Rees. Those were the fundamental papers that said that dark halos would be the scaffolding on which galaxies are built.

So, trying to stay simple, the next stage is to try to see if there's a simple rule for putting a galaxy into a halo. That's what I've been dealing with. So, actually, we just published a paper. The first author was my colleague from China, [Zhu Chen]. This is a picture in which you start with dark halos, and there's a certain mass of stars and gas that goes into a halo mass that's called the stellar-mass-to-halo-mass relation. That's actually empirically measured. People try to make hydrodynamic simulations that match that but have not fully succeeded yet. So, use empirical data on that. In addition, I told you before, galaxies while star forming are a two-dimensional family, so you have chosen the mass of the galaxy to correspond to the halo, but you need a radius for it. So, my theory is that the radius of that galaxy is going to depend on when that halo formed. If it formed early, it would have a physically small galaxy in it, and late will have a large galaxy.

Alright, so halos are evolving. You continue to use this rule, and then the second part of the theory is when a certain condition is reached, star formation goes out. I would say that's the other big mystery that's still plaguing us in galaxy evolution. Part one is how does the structure relate to the halo while you're star forming, and part two is why do you stop star forming? So, a favorite candidate for that transition has been feedback from AGN. We take advantage of that, and we put black holes into galaxies in an extremely simple way. The way we do it, essentially, is reverse engineering the observations. We say how the black holes must grow in order to reproduce certain scaling laws that are associated with the transition from star forming to quenched. So, we conclude that black holes live at the centers of galaxies. Their mass is growing as a power law of the central density. Galaxies reach a tipping point when the energy from the black hole, the effective energy, equals four times the gas binding energy in the dark halo.

At that point, that's when quenching starts. It's a well-defined moment that you see in all of these scaling law diagrams, a boundary. And then, for reasons that aren't understood, but seeded by additional data, it looks as though, actually, the black holes start to grow very fast just as they are turning the galaxy off. They grow by a factor of ten during death, and then finally, their feedback has nullified the ability of gas to fall in anymore, and the halo is now full of hot gas that doesn't cool anymore. And that's the end. That's the elliptical galaxy at the end of the process. This very simple theory – almost a cartoon – matches all the observed galaxy scaling laws in a way that all of these detailed hydro simulations don't even come close to. Of course, there's no physics in my picture. Why do the black holes grow the way they do? And exactly why do they quench the halo at that moment? I'm not saying that it's a full picture, but the vision of what needs to happen in the computer in order to equal the universe is right there in the simple cartoon.

Zierler:

Sandy, given all of these advances, where are computers in all of that? Of course, the computational power of computers and their ability to analyze data, it's hard to overstate how much that has grown since you've become interested in galaxy formation. In what ways have you and your collaborators harnessed that computational power for the research questions you're asking?

Faber:

Well, my collaborators, Joel Primack, and also in more recent years, Avishai Dekel, from the Hebrew University, they're leaders in making these computer simulations. They're absolutely crucial. So, on pencil and paper, back in 1982, I could write some laws about the mass of a halo and its radius, but I couldn't from that tell you how halos of different masses are clustered. I couldn't tell you how a large cluster of galaxies would form and how the halos there would be different from isolated halos. All of that, really, to understand, you have to numerically integrate dark matter and get a halo universe. So, Joel and his colleagues have really led in that area.

As I said before, I think we've been very successful there, and I think we really understand that aspect of things. Where we're having trouble is simulating what the baryons do. The baryons are much more complicated because they run into one another, and then they make stars and the stars create feedback that influence the baryons, and so on. So, here, I think we're less successful. What's happening here is that each group making these so-called "hydro-dynamic simulations" that have gas in them, they have their own little recipes for how a little volume is going to make stars, or how a patch of supernovae is going to drive a galactic wind out of the galaxy. Kind of garbage in, garbage out, I think at this stage. Broadly speaking, there's considerable success, but the individual simulations are quite different one to another. They aren't really reliable yet, and I'm a little cynical because years have gone by and every one of these simulators says, "Ah, new computer. Two times higher resolution. Now we've got it." And we never seem to have it because we're always dependent on these sub-grid recipes. So, that's how it stands for me. I feel as though I've done a service to the field by showing them what their codes need to do, and the scaling laws that they need to have in place at every stage over the last 13 billion years. So, if you want to know if your code is working, you should look at my scaling laws. 

Zierler:

Sandy, if you could extrapolate a bit into the future, what are your aspirations for the black hole quenching model in terms of what its best case scenario findings are going to demonstrate, and what limitations might you appreciate in the here and now that suggest that subsequent generations of models are going to become necessary?

Faber:

Okay, well, the model as it stands has a big problem. The problem that at first blush it doesn't agree with the data that I mentioned a moment ago, namely that the black holes need to grow faster even as the galaxy is dying. So, that seems paradoxical because why would more gas fall into the black hole just as gas is becoming less available in the galaxy as a whole? That's an unanswered question. Not only does it seem implausible physically, but you would think that -- we see energy coming out of black holes. There are quasars, there are Seyfert galaxies, there are X-ray sources. That's how black holes radiate, and yet, we don't see the requisite excess of radiation coming out right at that phase, which the model claims is the key growth phase for the black hole. So, that's a problem. The solution might be that some forms of energy can come out of black holes in an invisible way. So, maybe the quasar phase is not the feedback phase. Maybe there's a stronger phase that involves kinematic outflows that don't shine. That's my hope, that somehow, we will find a better way of actually gauging the energy output from black holes, and it will agree better with the predictions of the model. 

Zierler:

Sandy, what are some of the most relevant theories currently in black holes, and how are they important for your research?

Faber:

As part of writing the Chen paper, I wanted to acquaint myself with theories for black hole accretion in particular, because we observe these black-hole scaling laws. They're part of the scaling laws I keep referring to. There's a certain relationship between a black hole mass and its host-galaxy mass, or the host velocity dispersion. So, I reviewed all the literature to see how people have modeled these. It's really remarkable. I think the theorists have had very little success explaining exactly how black holes accrete in such a way as to account for these laws. I did discover one theory which is by a pair of people called King and Pounds. That seems to me to have maybe the seeds within it of explaining the basic scaling law. They say that black hole energy output becomes much more efficient at a certain transition point, and that transition point follows the scaling law that my model needs. So, that's encouraging. You're asking me what could be an advance? I keep telling the hydro simulators, you should go off and read these papers by King and Pounds and see if you can put something into your simulation that looks like their simple model. So far, I haven't gotten anybody to do that.

Here's another way forward that I'm really intrigued by, and that is Fermi bubbles. I think if you look at our black hole quenching paper, we referred to the current evolutionary state of the Milky Way, and also M31. It has long been a mystery about these two galaxies -- their total masses aren't very different. Their bulges are slightly different – the central density in the Milky Way is a bit lower than that in Andromeda – but the black holes mass difference is a factor of, I think, 50. Here we have two galaxies that are essentially similar globally, yet their black holes differ in mass by a factor of 50. Nobody has ever come up with a theory for that. I think it's consistent with the fact that the Milky Way is just entering the strong BH growth phase, and M31 has just exited from it. Now, that's interesting because the Milky Way also has this thing called the Fermi bubble, which is, I guess, created by the injection of hot gas and/or magnetic fields into the halo. We take pictures of it in gamma rays, and we can see these gigantic evacuated cavities. So, my favorite picture at the moment is that in the Milky Way, the Fermi bubbles look big, but they're still not filling the halo. So, perhaps, during the next giga year or so, our black hole will grow and inject more and more material into the Fermi bubble, which will gradually expand and cover the disc, and basically act like an umbrella to prevent further gas from falling in. A lot of evidence coming from different directions says that galaxies begin to quench inside out. A possible explanation for that is that at that point they're growing their Fermi umbrellas, and they gradually get bigger, and finally it's only the last parts that die. 

Zierler:

Sandy, I want to set the stage in discussing and learning about your collaboration with Chinese scientists. I want to zoom out a bit and note editorially that here in 2020, unfortunately, there are many tensions that exist between our countries that go far beyond, of course, science. So, I want to ask if you could explain when you got involved in Chinese collaborations -- chronologically when that was -- and if you felt any indication that there were those geopolitical issues that influenced the kind of work you were able to do with your Chinese colleagues. 

Faber:

The answer to the latter question seems to be no, fortunately. As you are very aware, the glory of being an astronomer is being irrelevant. An example, again, of God giveth with one hand and taketh away with the other. We win in that regard. By the way, I hope we come back to that question of irrelevance. Maybe that could be the end of our interview. 

Zierler:

Certainly. 

Faber:

Okay. So, I was traveling around meeting these folks, and two people approached me and wanted to work together. We had common interests. One is a scientist at Shanghai Observatory. She has sent a post doc to work with us, which has been incredibly fruitful. The other was a guy who has now become a really good friend, [Chenggang Shu], who is head of one of the key laboratories at a smaller place called Shanghai Normal University, which is again in Shanghai. He reached out to me and he said, "I'm trying to build up my department." He's trying to rehabilitate the Caltech telescope that used to be on Mauna Kea, and move it to the Atacama. That would put him on the map. He saw me, I think, as somebody who, as a friend of the department, could help advertise the department, and bring some new ideas, and so on. So, I've been visiting there a lot. In fact, my partner, Zhu Chen, is from that department. It took us three years to write this paper. That's a very long-running collaboration. I think that's the oldest for me in Chna. And then, what happened was we advertised -- David Koo has played a huge role in this -- our willingness just to advise people on projects. Now, I'm in retirement and I don't have to teach anymore. I saw, gosh, if I collaborate with these -- they're really brilliant scientists, and these kids are so motivated and come to us with tools that are already very, very well developed. You can sit with them in an afternoon. You can imagine a project, and the next day, you've got your first graph. It's just incredibly gratifying, the speed with which they get things done and move along. I said, "I don't have to write NSF proposals anymore. I can just have folks come and work with me, and I don't have to worry about this funding problem anymore." So, that's another impetus for going this route. 

Zierler:

Is your sense that the Chinese government is supporting basic science in the way that the United States was in the post-war era? 

Faber:

More. Oh, way more. There's a difference here in the sense that astronomy -- it was really the United States who created modern optical astronomy with these mountaintop western observatories. Lick Observatory, Mount Wilson, Palomar, and then the Hawaii observatories. That set the standard for the world. We have the biggest telescopes. Edwin Hubble discovered the expansion of the universe, etc. So, astronomy has occupied a very honored scientific position in the United States for over a century. China doesn't have that tradition. They tried some projects that didn't work so well. So, actually, astronomy is a bit under a cloud in China, even though China is pouring riches into other sciences. It does pour some money into astronomy, but it's more grudging. The astronomers are under some scrutiny to perform. 

Zierler:

Do you see any national security considerations in the way that the Chinese government supports astronomy in particular?

Faber:

No. Largely because astronomy is irrelevant. As far as I know, I've never heard of any instances of fraud of the sort that you hear about going on in materials science or biology, or other more financially and technically relevant fields. 

Zierler:

What about politically, among your Chinese colleagues? Is your sense that they are able to pursue their interests and to express themselves freely in the way that you are?

Faber:

Almost. There is not a political dialogue going on in China the way it's constantly going on in the United States. I think they feel themselves comfortable and free in their culture's way of doing business. They get their work done. They are in complete awe and admiration of what their country has accomplished in the last 20-30 years. All Chinese I’ve met feel intense pride in how far along their country has come. They're not going to apologize for that in any way. I think the most specific thing that annoys the heck out of them is the firewall which prevents them sometimes from getting really nice access to data abroad. When you go there, you have to have the latest VPN, and while you're there, that one will be discovered by the government, and you've got to find another one. It's like Whack-a-mole, and everybody is playing that game. So, I can't go to China and function unless I have a colleague who's constantly looking for the latest VPN for me. I just can't get out. I can't even read my mail. So, there are some practical issues but most people, I think, aside from the computer issue, are quite content. 

Zierler:

Sandy, to be clear, the vast difference that you see in the way that China supports basic research versus the way that the United States government supports basic research, this is not a partisan comment. You're talking about broader structural changes that don't have much to do with Democrat or Republican administrations. This is sort of just generally where these countries are headed in the 21st century. 

Faber:

Yeah. So, before we go there, apropos of the previous topic, something that I am following is the reports of the Uighur persecutions. So, you might be interested in asking me what my Chinese colleagues thing about that. Well, first of all, they don't know. 

Zierler:

Right, because there's censorship within their own journalism. 

Faber:

That is correct. So, then, you talk to them a bit, and they listen to you, but there's disbelief. "No, we don't do that." Then, if they begin to understand, yes, maybe some of this is actually going on, how do they feel about it? They're not concerned. And they're not concerned because they have a different sense -- this is pervasive throughout the whole culture, as far as I can see -- about the relationship of the individual to society. So, this is old news. In these Asian societies, individualism is much reduced compared to what it is in the U.S. So, they see themselves, first and foremost as having an obligation to their families, and then instantly after that to their society. So, they would say if Uighurs are being put into camps even forcibly, and forced to learn Chinese, that's good for them, because "They need to become part of our society. Our society is the standard, and disruptive groups with different goals, aims, ethics are not tolerated." You want to live in China, you live this way, and they don't see that that's a problem. 

Zierler:

Sandy, I can't help but wonder, if we flip that question, and if any of your Chinese colleagues asl you what you think about George Floyd, for example.

Faber:

They don't ask me too much about George Floyd. They're more interested in, and proud, actually -- it's another feather in their cap. It's the pandemic. Forget George Floyd for a moment. That's kind of a detail in this much bigger picture of the relationship between the individual and society. So, my friends over there, they're walking around and going to stores. They're living a normal life now. They're scrutinized. They report, they're tested in ways that we would find invasive and restrictive of individual library. But the result is that their GNP is now largely recovered, while we're looking forward to months and years of struggling rather ineffectively with this. It's purely because they can get together. They can get together and march together, and they don't see that as much of a loss to their personal freedom. They expect to do it. We, we're just all over the place. "You want me to put on a mask? No." So, I think the pandemic, more than anything, is showing the strengths and weaknesses of the two different ways of doing business, and it really upsets me to listen to politicians’ sort of saying, "Oh, well, the Europeans are having problems, too. There's no way of dealing with this." They never mention that, in fact, all of those countries on the other side of the Pacific are dealing just fine. Taiwan, Japan, Vietnam -- all of those with a different culture have come to grips, and we cannot. 

Zierler:

I mentioned George Floyd because I thought perhaps it might be an accurate comparison in the way your Chinese colleagues might consider that systemic racism is a real problem in the United States. 

Faber:

I think my colleagues in China don't understand this, because it just doesn't -- they're Han Chinese, and they just can't really imagine what that is like, or that it could happen. They've always been part of the mainstream culture. In contrast, I do know Chinese here -- our younger daughter married a first-generation Chinese. His parents were born there, and they live now in Canada. We have very deep conversations about what life was like for Chinese immigrants here, at the end of the last century, around 1900, building the railroads and so on. We tell our grandchildren about that, and so on. They're very familiar with it, and the George Floyd story to them resonates much more. 

Zierler:

Sandy, of course, much has been made about a particularly, or uniquely American style of understanding the universe. Essentially, bringing a frontier mentality to the final frontier, as it were. In your collaborations with your Chinese colleagues, have you ever detected a uniquely Chinese approach to understanding the universe? 

Faber:

This reminds me of a question I got recently. I was given an award from a local high school for young women -- girls' school. I was asked, "What is the value of diversity in doing astronomy?" The same idea. Somehow, can you bring different valuable viewpoints to bear? I'll answer it the same way for you the way I did that question. There's only one way of doing good astronomy, and the Chinese do it just the way we do. 

Zierler:

What are some of the most exciting things that are happening in Chinese astronomy right now, both on the observational side and perhaps even on the theoretical side?

Faber:

They're producing excellent papers. They are making use of all the public catalogue data that had been produced by so many projects around the world. That's why I find it so nice to collaborate with them, because that's what I want to do right now too. Use all those numbers on CANDELS galaxies, you know? 50,000 galaxies, and so on. So, that's, I think, at a very high level. The cosmology is very strong. Active galactic nuclei is also very strong. Probably the biggest single effort, financially, in the country, is radio astronomy, and it's really focused on pulsars. They have a 65-meter pulsar telescope in Shanghai, and they built the FAST radio telescope, which I was lucky enough to go visit. That's their version of Arecibo, but much bigger. Drop-dead gorgeous construction. It's just fantastic. That is also under scrutiny because last I heard it's not working, but maybe progressing. I don't have any final news of it. You might know that it's a spherical dish, but they pull on 2000 wires to reconfigure portions of it as a parabola. Then, as the source goes overhead, the reconfigured portion is moved across the sphere, so at any given moment, they're only using part of the spherical dish. But it's still huge. It's an enormous thing. So, they built it, and certainly all the electronics is working, but the question is can they get this active surface to work? Theory, I think -- there are theorists, but they don't stand out for me as being much, much better than the rest of the world.

Where they're not doing so well is optical astronomy. That's an interesting story. The structure of astronomy there is different from here. I think something that we stumbled into and maybe didn't realize how good it is the close partnership between federal funds and universities in this country. The NSF and NASA are the glue here. They're the conduit. In France, and also in China, the federal funds tend to go much more to national observatories. Meanwhile, there are university departments. There is an NSF over there, but it's relatively smaller than our NSF. The flow of funds through it is much smaller. So, they set up an annual evaluation system in which the various universities are competitive against one another. They don't collaborate well the way we do in this country. The source of funds from the federal level to the national observatories is the Chinese Academy of Sciences. From what I've heard, that's kind of an old boy network that isn't really run with good peer review. They have set up laboratories that sort of have cornered the design and construction of ground-based telescopes. They're not in wonderful contact with the huge advances in ground-based telescopes, segmented mirrors and so on, that have taken place around the world. The rest of the world has done great things in optical astronomy, and China has lagged. Partly for this reason, and also because they don't have any good observing sites.

That's another interesting point. The Chinese government might be accused of building big projects just so that people could come and look at them, regardless of whether they work. For example, we were talking about this FAST telescope a moment ago. Radio telescopes should be in the middle of nowhere because truck ignitions and things like that screw them up with interference. What did they do? Ten miles away, they built a tourist town, which they call "Astronomy Town," which is full of four-star hotels. People are flocking to that town, and then there are busses that take them to come and look at this FAST telescope. It's a tourist attraction. Whether or not it actually does any astronomy wouldn't matter for this whole activity that is kind of riding on the coattails. So, it's a conflict of interest that doesn't make for really great scientific performance.

Zierler:

Sandy, let's bring the conversation back to California. I'd like to learn about the Osterbrock Leadership Program. First, tell me a little bit about the namesakes, Donald and Irene Osterbrock. 

Faber:

So, Don was our director for many years. This was before we became University of California Observatories. This was in the Lick days. We were just making plans for the Keck telescopes, and Don could see that it was going to be a long slog for the director to get those going. He preferred to return to scientific work. So, at that point, Bob Kraft took over as director. Don was a very effective director during his term, and it was he who established the groundwork where all the astronomy campuses could cooperate to help build the Keck telescope. We were a fractious bunch back then with competition, especially between Santa Cruz and Berkeley. Don was a very effective leader dampening that down and getting the team together. He was also fantastic with graduate students. His roster of successful astronomers is long. So, for both reasons, not to mention being the leading theorist of the day in the mission line and interstellar medium physics. So, put that all together, he seemed like a wonderful person to name this after. 

Zierler:

What was your involvement in the creation of this program?

Faber:

I think I thought of it. I think it was my idea. It was born of the conviction – even before we were thinking of a memorial to Don Osterbrock -- I really feel that graduate training in the United States could be improved. We are the glory of the world. The whole world sends their people here to earn PhDs in our universities. But these PhDs are expensive. The last time I tried to add up the cost of a PhD at UC Santa Cruz in astronomy, it was half a million dollars. I think it's gone up since then. I'm being honest now. I'm taking my salary, I'm taking if they use Keck, that's $120,000 a night. That's the cost to operate, and gets one night of data, etc. So, it's a lot of money. I kind of imagine myself being at some cocktail party and being asked, "Well, what is this PhD training worth? Why should I, the taxpayer, spend money on that?" On the one hand, I think that astronomy training is unique. It really teaches you to think. Astronomers have to draw conclusions with incomplete information, point number one. Point number two, they have to do so without getting their hands on and doing an experiment. So, we are, I think, masters of looking around and trying to get any clue we can, and sifting and sorting all of that evidence that comes to us, throwing away the uncertain stuff, etc. 

Zierler:

Sandy, just to interject, on the idea of incomplete information, to a degree, isn't this what all scientists struggle with? Who has the complete picture?

Faber:

Well, maybe no one, but if I'm a biologist, and I do an experiment, and I say, "Hm, maybe I saw something there. Let me tweak this," and I'll do another one. So, I have more control, but astronomers don't have any control. All they can do is observe the scene of the crime. The other science that's very similar is geology. We don't do experiments with planets. You have to piece together the history of Earth just from picking up rocks. Right, so I'll stick to my guns on that one. I think this is an excellent skill for life, and for running organizations. It gets you into a mindset in which, okay, I don't understand, but I've got to make a decision. Let's move on, and how can I do that? So, the training itself is extremely valuable, but what's missing is the fact that many PhDs go onto leadership positions. They run teams, they deal with budgets, they have management issues. We don't teach them that at all. We don't even teach them that there's a world out there. We don't even want them to know because that might take a few precious seconds away from their research work, which we want them to be 110% focused on. That's maybe good for the advisor and the laboratory, but it's not good for the person because it's not cultivating their full faculties. It's not preparing them for future challenges, and it's not good for society. I thought that maybe by not taking a huge number of cycles in graduate student training, we could put a frosting on it that would be worth more than just the few percentages of minutes taken away. I think that's proved to be true. 

Zierler:

Sandy, I can't help but observe that perhaps subliminally, in reflecting on your own career, you might have thought how much you would have benefitted by going through this program. 

Faber:

Perceptive. That's so true. That's right. 

Zierler:

Are there any academic colleagues that this program engages beyond the world of astronomy who might have effective and useful perspectives to share on what it takes for leadership in general?

Faber:

Well, we invite all kinds of people in to talk to our grads. Getting outside the astronomy bubble is part of the recipe here. I think the highlight of the program, and unfortunately can't take place this year, is our week in Baltimore/Washington. Maybe we can -- where are you?

Zierler:

I'm right now in New Jersey. 

Faber:

You're in New Jersey. Too bad. Yeah, so we're hosted by Space Telescope Science Institute. Bob Williams, the former director there, is a mentor in the program. So, we interview a ton of astronomers farther along in their careers, just to see what they're doing and what they thought of their graduate training, and where it took them, and what they can do as a PhD. We meet with members of the Maryland State Legislature just to get a political bent. We go to Washington, D.C., and meet with the heads of the NSF, the president of the Carnegie Institution, the director of the Carnegie Embryology Laboratory, deliberately getting out of astronomy and into another field. That's always a fascinating meeting because you see that the methods and cultures of those two sciences are very different. All together, we meet with about 30 people in one week. Our students get to sit in like flies on the wall on the Time Assignment Committee meeting. Confidentially. I can't go in, but they can go in. This is just eye-opening for them to see the world that awaits them. They have no idea. 

Zierler:

Is the program well developed enough at this point where you see the freshmen class that has graduated from the program and the way that it has benefited their careers as they go into positions of leadership?

Faber:

Too soon. It hasn't been in place that long. We've got postdocs but nobody beyond that. So, I would say that it's too soon. You might know, though, that we got a very, very generous donation from a donor, $200,000. That's acting as seed funds to launch two more programs at two other universities under the auspices of the American Astronomical Society. So, my goal is, actually, I think this should spread and take over all of PhD training in the United States. But I understand astronomy best. It seems that we might try to propagate it and study it within our field first before advertising more broadly. 

Zierler:

You're absolutely right that there is that bubble in every PhD discipline. We're all focused on our particular research, and nobody talks about how that research is going to launch us into careers that are going to make us leaders. There's just a total disconnect there. It's certainly not unique to astronomy.

Faber:

No, that's right. It's the American PhD. 

Zierler:

Sandy, let's talk about this concept of cosmic knowledge. There's any number of guesses as to what that phrase might mean, but of course, you use it in a very specific way. I wonder if you could explain that and the origins of your thinking on this idea. 

Faber:

Well, this, again, came out of the feeling that we're not optimized. My dad used to say to me -- I've lived with this my whole life long -- "Sandra, make yourself useful." So, that's kind of a theme that pervades a lot of the things that I try to do. The Osterbrock was one. Let's make more useful PhDs. Let's now try to be more useful as astronomers. Realizing that astronomy is an expensive science, why do people care, and why should they care? What should we be doing in order to be more useful? 

Zierler:

Particularly because with taxpayer dollars, there's always zero-sum choices that need to be made about what science to fund and what science not to fund. 

Faber:

That's right. Absolutely. I have always thought that astronomy is important because it puts us in perspective. I would add the geophysicists there, and to some extent the biologists. I think it's important to understand how human beings got here. I've been privileged during my career to really see the astronomical chapters of that book unfold and get fleshed out. I'd say astronomers get the first 25% of the book, or something like that. Then, the planetary physicists take over, and so on. Why is that important? Well, isn't it miraculous that we have pretty much explained all of this using just the laws of science? There're no miracles in this story, and I feel we do need to be talking to people who believe in myth, and whose whole lives are governed by myth. It points them in the wrong direction.

I'm reminded of this famous quote by the guy who was Secretary of the Interior for Ronald Reagan who said, "Seen one redwood, seen ’em all." Now, he was a Mormon. Mormons believe, I'm told, that we're here only for a short time, and that a miraculous transformation will soon occur, and the condition of Earth will become irrelevant. We don't need Earth anymore. Earth is only a waystation for us. It's temporary. That is not a recipe for environmental action. It's just the opposite. If I tell you the cosmic story, and it took 13 billion years for us to get here, I can also tell you, having understood that path, I now know something about the future. I know what the Sun is going to do, I know what the Earth is going to do, I know what the Solar System is going to do. If we can just solve that pesky asteroid problem, we have several hundred million years ahead of us. What are we going to do with that? We're the first generation of humans to understand the past well enough to know that we're now confronted with this enormous challenge. Is there an obligation? I think now I've switched completely from scientific issues.

Astronomy is important for setting the scientific agenda and the background, the stage, on which the discussion now needs to take place. The key discussion now is an ethical discussion. Are we stewards of the Earth? More than that, are we obligated to be stewards of the Earth? Does it matter if the Earth is rare or common? If it's very common, maybe we can squander this one. But if Earth is the only Earth like it in the entire Galaxy, maybe we have a greater responsibility. Do we owe anything to the plants and animals around us? Do we owe anything to future generations of our own kind? We don't have an ethical sense for these questions, I think, because I believe that we get our ethics evolutionarily. I am a sociobiologist along the lines of E. O. Wilson, and I believe that our ethical system has been tuned by evolution to suit beings with our strategy for making a living, which is a mixture of self-promotion and social investment. Those are the devil and angel on our shoulders, right? We're constantly in tension with that, and we spend a lot of time trying to balance those two forces. We were talking about the Chinese a minute ago. They have a different balance than we have in the West, tilted more towards social investment and away from the individual. This is why they are dealing so much better than we are with the pandemic.

Nevertheless, all humans, to some degree, have this issue in their ethical systems, I believe. Some dress it up with organized religion. Other people, like myself, just see it as basically the natural next stage of chimpanzee ethics, which they have, and look a lot like ours if you study it. Now, the problem is that that ethical system, like everything else about us, has been designed to make us survive with this strategy that we have. It only deals with questions that come up in that struggle. Our struggle, to date, has had no thought for future generations. It didn’t need to. In order for me to be a healthy human being, raise a family, and have descendants, I don't have to think about future generations a billion years from now. So, I lack that capacity. I lack that ethical organ. That's why we're in trouble here, looking at the future of the Earth. Our ethical system just does not deal with these issues. So, the challenge, I think, is how flexible our ethical system is and whether or not we can grow a new one. Here’s an experiment I do in talks about Earth’s future. The first thing I do before I reveal my main thread is, I ask my audience to envision the following: it's a thousand years from now. A thousand years is long enough that nobody in the room feels responsible anymore. It's distant. A thousand years from now, I tell you -- this is a fact -- that Earth has been seriously degraded. It's impossible for intelligent beings like ourselves to live fruitful lives there anymore. A smoking ruin, if you will. How do you feel about that? You get three answers: you think it's bad, you think it's good, or you don't want to commit yourself. 

Zierler:

Who thinks it's good?

Faber:

95% of the people in the audience say it's bad. 3% say it's good, but on further scrutiny it usually turns out that they haven't understood the question and they actually think that Earth would be better off without us. So, that's good. And then the other people don't want to commit. The point is, there is an overwhelming sense that it would be bad. Where does that come from? Is that the germ of concern for the bigger picture that somehow, we need to foster, nurture, understand, and cultivate in our educational program? I think without that kind of focus on the bigger picture downstream – our destiny if you will, why is Earth important? If Earth is destroyed, what is the loss? These are the questions I would like to pursue, and I've been trying to form this Earth Futures Institute, a very nascent effort so far, not so much as to solve the problems, but to understand our own psychology better. I think, as it is now, we're not equipped genetically to come to grips with planning the future of the Earth. 

Zierler:

Sandy, it sounds like, to return to this idea of astronomy being irrelevant, that you've sort of looked to solve that inherent problem by demonstrating that the kinds of things that you understand about the universe are actually quite relevant for the most existential and immediate problems we face right here on Earth. 

Faber:

That's what I think, yeah. I have felt a large part of my life feeling a little guilty being an astronomer. I always think about the taxpayers. I really do. Being supported so generously by the taxpayers to play in my little sandbox while people are dying out there, going hungry, etc. Why do I have that right? I'm kind of closing my career with the notion that actually astronomers might be among the most important people on the planet right now. So, I'm feeling less guilty. 

Zierler:

Is there an intellectual tradition in astronomy to which you feel you belong in developing this career-long narrative journey? 

Faber:

I don't think so. I don't really know -- I only know one book, or a couple of books, that are starting to engage with the question of what is the good of these long-term sciences? There's a book called Timefulness. That's written by a geologist, and that's very much in the vein that I'm speaking. But actually, the book that got me thinking most about this is by my colleague, Joel Primack, and his spouse, Nancy Abrams. Do you have an AIP interview with those guys?

Zierler:

No, I'll have to look. I haven't, but I'll have to look. 

Faber:

That would be extremely interesting. Joel did some very interesting things in starting the Union of Concerned Scientists. He co-founded the AIP's Congressional Science Fellows Program. He's always been interested in the social ramifications of physics. He and his spouse wrote a book called “View From the Center of the Universe”. Their basic message was that harmonious cultures depend among other things on a shared cosmological myth. If you analyze these cosmological myths, they solve the problem of how the individual fits into the bigger picture. Of course, the story is different for different societies, but that's what they're about. Their argument is that now with the combination of astronomy and geology, telling the story of Earth and the Solar System and going all the way back, we are now ripe for sharing this science-based cosmic myth with the world, and they think the ramifications of that are going to be very powerful. So, I'm kind of riding on their coattails, I would say. They got started in this before me. 

Zierler:

I wonder, Sandy, in some of your younger colleagues, and even students that you interact with, if the kinds of things that you're feeling now about what astronomy is all about might feel more natural to them than they would have when you were a graduate student thinking about your fellow students, or even your advisors. 

Faber:

In a way, in the sense that I think every young person now thinks more about the future of the Earth than I did when I was starting graduate school. So, to that extent, they're aware of those looming issues, but people seem to find them more depressing than inspiring. The day-to-day life of the graduate student astronomer these days, I think, looks awfully much like what my life was like 40-50 years ago. So, these issues are not penetrating to any degree into daily discussions in my department. People don't stand around in the halls saying, "Hm, how can I talk to my class about cosmic knowledge?" That hasn't happened. 

Zierler:

The goals of the Earth Futures Institute -- I mean, they are quite profound, but it's also -- the reality is such that how much influence could one small endeavor have? So, I wonder if you could explain a little bit about what the realistic goals of this endeavor are. What cord are you hoping to strike so that the kinds of things you feel become more normative in your field and beyond?

Faber:

I have been grasping at straws here. Santa Cruz is one of the poorest of the UC campuses. It has no significant donor base. There's no Mr. or Mrs. Moneybags who will endow an institute to even get going. For example, Stanford started an institute -- some topic, I forget what it was. With great fanfare, they announced it. I went and I looked at their webpages, which went on for pages. To start it, they had hired somebody who was formerly a very high up project manager in the federal government. They gave six faculty 50% release time to form an advisory committee. They had another 100 affiliated faculty. They had several million dollars per years in grants, etc. You get the picture, right? We have nothing like that. So, if I had an edifice like that, I could maybe make some sort of an impact. I haven't had anything like that. I put in several grants; they've all been turned down. So, I'm kind of -- there are several people, I would say maybe 40 faculty who are really interested in this idea. But then what happened, of course, was the forest fires. Before that, we had a graduate student strike which paralyzed everybody for winter quarter, and now we're in the pandemic mode. I hired a post doc. He quit to go work for a venture capital company. It's just been one -- I'm a little tired, if I may confess. So, I've sort of been recovering with research work, which has energized me greatly, and letting Earth's Future sort of percolate for a while. Maybe I'll take it up, but I have to do something different from Stanford. I have to do it with no money. 

Zierler:

I wonder if in some ways the Earth Futures Institute is an institutional home for the broader endeavor you have as a public science communicator. In other words, your work explaining science to lay audiences, who understand at a basic level the concerns that you have, but don't understand what you know about how the universe works. 

Faber:

You could say that, but really, there are other institutions in Santa Cruz and elsewhere who already do that. I think the new thing about Earth's Future Institute is to force people to address the very basic question of why are we important? Are we important? And how do we even go about thinking about that? As a byproduct, and this is the painful part for some people, I think, it would force you to think, well, why do I believe in anything? Most people, I think, don't know why they believe in things. I know why I believe in things. It's because I have a genome that's a human genome, and it generates emotions and feelings in me, and that is my analog computing system for deciding what is right and wrong. I'm only comfortable as long as I'm consistent with that machinery, which I was born with. What do I do if I wasn't born with the right machinery to answer these new questions? 

Zierler:

Sandy, it doesn't sound like this leaves much room for considering metaphysical aspects to reality that might explain, not only why the universe exists or how it exists, but why you exist, or understand the things about you that motivate your desires. 

Faber:

Well, I sort of disagree with that. I would argue with you because you were too squishy with using that word "why," right? As you know, there's sort of an existential meaning for why. Why is Earth here? And then there's the normative meaning of why are you planning your life the way you do? There's the two whys. So, yes, I think meaning number one, there's absolutely no room for metaphysical, but meaning number two is another matter. I'm going to challenge you. What do you mean by metaphysical? 

Zierler:

Well, to assert that all of your constituent parts are merely physical manifestations, and that all of your emotions are a sum total of the genomes.

Faber:

Machinery. 

Zierler:

DNA. External stimuli. It would suggest by default that there's nothing more there, which may or may not be true. I'm not asserting one way or the other. I'm merely observing that you seem to be confident or comfortable in the idea that even things as complex as emotions merely exist in a physical realm, that there isn't something beyond that that might account for that. 

Faber:

I feel very comfortable with that, which is probably why I believe it. I really think that people adopt the religion that is comfortable for them. I am perfectly happy to have people accuse me of just believing the “atheist religion”. You don't know that. I don't know about this god over here, but I don't know what you're talking about, you know? However, I do think that neuroscientists are really uncovering a lot of the basis of the physical mechanism for what goes on in our brain and our decision-making process. Have you ever read the book, “Thinking Fast and Slow”?

Zierler:

Yeah, yeah. 

Faber:

Okay. Right, so we know having read that book that like 99% of the stuff that's going on inside our head, we don't even have any consciousness of it, right? I already know there's stuff about me I don't understand. So, I don't feel the need to invoke a divine being to understand the little bit that I do see. 

Zierler:

Sandy, because the concept of a god is so wrapped up in the universe, do you feel that your understanding of the universe gives you a privileged position in those debates about whether God exists or not?

Faber:

To a degree, in the sense that we've answered so many questions without appealing to God. But I have to tell you this little story. I think it was Pope John Paul II. It was just when I was starting to work on galaxy formation models, and there was a Vatican conference (November 1981). The Pontifical Sciences Academy held an audience where we met the Pope, and shook his hand, and so on. He gave an address at the beginning of that audience, and there were three Pontifical Sciences Academy meetings that were occurring at that time, contemporaneously. He thanked each meeting. He started by addressing the tropical disease people, and said how bad these diseases were, and thank you very much for trying to cure them. Then, he addressed the nuclear winter people, and he said that would be a horrible thing, and thank you for telling us about it, and maybe we can avoid it, and so on. These were sort of perfunctory. And then he got on to the cosmologists and the galaxy formation people. That was my meeting. And he went on at much greater length. Basically, that was what he clearly cared about. His message was, "Thank you very much for answering all these cosmic questions -- but there will come a point when there's a question that your science cannot answer. At that point, you need to come and see me." He literally said that. It was very funny. So, no matter how successful astronomers are by expanding the boundaries of knowledge, the Pope would always say there's always another question out there for which you will need me. 

Zierler:

But science, of course, runs into that as well. So far as getting all the way back to T=0, and what might have been before that. 

Faber:

It's the “before that”, yes. You haven't asked me about multiverses. 

Zierler:

Ah. Shall we engage in string theory a little bit?

Faber:

Well, I don't know enough about string theory to expound on that, but I will make the observation that I think anthropic reasoning has been the only, with one glaring exception, the only successful way of explaining anything in the history of astronomy. So, we have all these numbers, and one of them that's important is the flatness of the universe. The universe really does seem to be flat. That's the only number we have a physical mechanism to explain, and that's inflation. Inflation makes flat universes. But all the other 125 numbers seem to be just drawn out of the air. I know that physicists hate anthropic reasoning, but it's been proven to be true time after time. For example, supposing we imagined ourselves in Greece 2000 years ago, debating, and talking like physicists. What is a constant of our universe? The radius of the Earth. Wow, that's a constant of nature. Where did that come from? So, the one physicist says, "Evidently, there's a rule, and there's only one way you can have this number. We don't know what it is yet, but we're physicists. We'll figure it out." It's like trying to figure out what's the mass of a proton, or something like that. But the other person, thinking more like an astronomer of today, would say, "Hm, well, there's another explanation, and that is there's a machine out there that's creating all of these round bodies. We don't understand that machine, but they're all different." And add in a little spice about gravity, and stuff like that. “Some of them are too big. We'd be crushed on their surface. Some of them are too small. They might lose their atmosphere, and so on.” So, there's just a small window for the radii of a rocky planet, if they used that word, on which we could be standing here today to have this discussion. So, that's my explanation.

And by the way, a consequence for me to stand firmly on that argument is that I must believe those other bodies actually exist. “I'm telling you here and now,” the Greek astronomer says, “that there's an ensemble of round bodies out there in the universe that we have not discovered yet. Maybe people will discover them some day.” And of course, we have. Same thing with the galaxies. Same with the Sun. Why is the Sun the way it is? Stars are all different. The Sun is the way it is because we're next to it. Galaxy also. Some galaxies, I'm sure, cannot support planets like Earth, because they don't have the right composition. Okay, the next leap up is the universe. So, I was waiting for many years for a machine to create other universes with different properties. The key thing is that they all have to be different. There has to be a wide range of properties. You're not explaining one number, you're picking it out of an ensemble. So, when I heard about string theory, I said, "That's it. That's what I'm looking for." The landscape of string theory is going to make all these universes that we've never seen. So, yeah, I'm a strong proponent of the meta verse -- multiple universes and anthropic reasoning to describe why ours is the way it is. And by the way, just as I insist on capitalizing Earth, Sun, Solar System, and Galaxy to signify that they are OUR members of these larger ensembles, I insist also on capitalizing Universe, since the situation is exactly the same.

Zierler:

How do you avoid the inevitable despair when you come up against the concept that in multiverses, anything and nothing can be true at the same time, because fundamentally nothing is testable?

Faber:

I don't live in a -- I put myself in the mind frame of that other Greek back there, the astronomer Greek. I comfort myself by having had a brilliant insight and from that being able to suspect, not necessarily prove, that there's something much grander than anything that I have ever seen. The hope is that maybe someday future scientists would be able to discover that. And we did discover the planets. So, that guy 2000 years ago was vindicated. I don't know enough about string theory, or these other concepts, to tell you whether or not they're ever discoverable or not. I would say a lot happened in the last 2000 years to make discovering exoplanets possible, and I'm telling everybody that unimaginable advances might happen in the millions of years allotted to us … if we take care of ourselves. 

Zierler:

While you can't be sure, Sandy, it sounds like you're certainly open to the possibility, and you find it exhilarating. 

Faber:

Right, absolutely. I don't find any reason to despair. 

Zierler:

Sandy, I want to ask you for the last part of our talk, let's look to the future. What are the things that you want to accomplish for the remainder of your career, and in what ways -- going back to this idea of thinking about the Greeks -- in what ways are you looking to continue to bridge the divide between science and the humanities, to get to those fundamental truths, and the most important things that face us as a species?

Faber:

Well, I'd certainly like to advance the Earth Futures Institute beyond its current state. I do think it fills a need. As I say, I've tried several things over the last three or four years. I've spent quite a lot of time on it, and I'm certainly -- I'm playing the odds here. I don't think I want to spend 100% of my time on an effort which hasn't been too successful in the past, when I might do other things in addition. So, at some level, I hope to continue to see that along. The other thing I'm still really very engaged in is this question of black hole growth, and the quenching of galaxies, and seeing all kinds of budding opportunities with new collaborations around the world to pursue that, especially with people who are doing hydrodynamic models. I think now I'm in closer contact with them, and they're listening to me more. Maybe they'll take my scaling laws more seriously and try to test their models that way. So, I'm keen on that. I also want to advance the Osterbrock Program. But, you know, I've never been a person with a big plan. So, I'm sort of approaching the waning years of my life the way I always approached all the other years, just day-to-day. What do I want to do? That's about it -- in my own life, I don't think that large. 

Zierler:

Last question, Sandy: what are you most excited about in science? What are the things, in terms of advancing our understanding of the universe, that you're confident you'll be around to experience and even be a part of?

Faber:

Well, that's two different things, but I think planetary exploration in astronomy really is extremely interesting, and I really like it because I do think it relates to the Earth Futures question. People can understand, I think, and appreciate -- again, it's this innate quality that we have, this emotional reaction to whether Earth is rare or not. Most people care about that. I think exoplanets are a major feature of the Galactic landscape that we need to understand in order to plan our own future. Natalie Batalha tells me -- she's head of our new Astrobiology Initiative -- she tells me she's confident that within twenty years, we will have discovered Earth-mass planets in quantity around other stars. It's right there, she thinks. So, I'm very excited about that. The other thing I'm excited about is genetic engineering and the possibility of re-engineering our ethical system, and our lifetimes, to be a more powerful, a more present Galactic inhabitants. So, two things need to happen. We need to avoid spoiling our planet and killing our own species. That's where the genetic re-engineering of the ethical code would come in. But also, we need to live longer if we're going to voyage the stars. I think that's a destiny that we could try to aim at. 

Zierler:

To be clear, this is science reality that you're envisioning. Not science fiction. 

Faber:

Oh, total reality, but not tomorrow. Although, the need for re-engineering the ethical code, the moral code, is urgent, and probably not likely that that's going to happen in biology. It's got to happen some other way. 

Zierler:

Well, if there was ever a year that indicated the urgency of this issue, I would say 2020 must be up there. 

Faber:

I'll say. 

Zierler:

Sandy, I am absolutely delighted that we were able to connect and do this. just thrilled. 

Faber:

You're a great interviewer. 

Zierler:

Oh, thank you very much. 

Faber:

You're a wonderful interviewer. I've really enjoyed talking to you. You've got a real talent. 

Zierler:

Well, I have to hit end on recording there.