Alan Dressler

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ORAL HISTORIES
Alan Dressler

Photo courtesy of Alan Dressler

Interviewed by
David Zierler
Interview date
Location
Video conference
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Interview of Alan Dressler by David Zierler on February 24, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
www.aip.org/history-programs/niels-bohr-library/oral-histories/46907

For multiple citations, "AIP" is the preferred abbreviation for the location.

Interview with Alan Dressler, Astronomer Emeritus at The Carnegie Institute for Science Observatories. He describes his current focus on the James Webb Telescope and he conveys concern for a "post-reality" political environment that has taken a grip on American politics. He recounts his upbringing in Cincinnati, and how his curiosity about how things worked naturally pulled him toward astronomical interests. Dressler discusses his undergraduate education at UC Berkeley and his decision to pursue a PhD in the newly created Department of Astronomy at UC Santa Cruz. He describes the importance of the Lick Observatory for his research under the direction of Joe Wampler, and how Jim Peebles gave this thesis project a "seal" of approval. Dressler describes the origins of the Dressler Relation in his study of the morphology of galaxies and the density of their environment, and he describes the opportunities leading to his postdoctoral appointment at Carnegie. He explains the history of the Caltech-Carnegie partnership in astronomy, and he describes working with Allan Sandage and Jim Gunn. Dressler emphasizes the revolutionary effect the Hubble Telescope imparted to the field, and he discusses his time as a Las Campanas fellow. He describes how his work on galaxy formation fed into larger questions about the origins of the universe and the broader philosophical implication of our understanding of Earth's place in the universe. Dressler explains the Great Attractor Model and the state of play in black hole research in the 1980s, and he describes why he did not need to "see" an image of black holes to be convinced of their existence. He narrates the origins of the Association of Universities for Research and Astronomy, and the drama surrounding the repair of the Hubble. Dressler describes presenting the HST & Beyond report to NASA administrator Dan Goldin, and he discusses the natural progression for his work on the NASA Origins program. He discusses his subsequent focus on the Magellan Telescope and the EOS Decadal Survey. At the end of the interview, Dressler reflects on the strides made in galaxy formation research over the course of his career, and he conveys pride in playing a role in science, for which he appreciated since youth as a field that offered limitless opportunities to improve the world. 

Transcript

Zierler:

Okay. This is David Zierler, Oral Historian for the American Institute of Physics. It is February 24th, 2021. I am so happy to be here with Dr. Alan Dressler. Alan, it's great to see you. Thank you for joining me. 

Dressler:

Nice to be here, David. 

Zierler:

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

Dressler:

I am an Astronomer Emeritus at The Carnegie Institution for Science Observatories, which is in Pasadena. That's an institution that used to be called, earlier, Mount Wilson Observatories, and then later, the Hale Observatories. I formally retired in 2016 in order to make my position available for the next people coming up, because positions are in short supply. But I'm continuing to work pretty much full time under the emeritus label. 

Zierler:

Of course, looking at your background, with all of your books and papers behind you, emeritus does not mean you're no longer working. What are some of the major things you've been doing since you went emeritus in 2016?

Dressler:

Well, I decided to focus on a few projects because it seemed like over the longer term, maybe I wasn't going to be fully engaged in astronomy. I have other interests, some long unfulfilled, and my wife and I are keen to explore other parts of the world. So, I thought being more focused there are two projects that I had been working on for years that I thought maybe I can do one more program, and a paper or two from each. Then, because I'm on the NIRCam team for the James Webb Space Telescope, and I have one new program I’d like to accomplish with the early observations that team will make with the primary camera on the Webb. That's been my main activity for a while. So, scientifically it looks a lot like before, but I'm not participating in much as I used to in the business of our observatory or our field. There were a lot of committees and activities I served on as part of my career that I’ve really have retired from. 

Zierler:

Alan, as a first order of business, I want to get some terms on the table, because they mean different things to different people, and particularly, different things at different institutions. So, astronomy, astrophysics, cosmology. Where are the boundaries, and where is the overlap as they related to your research and your interests?

Dressler:

Astronomy traditionally means anything that has to do with space: planets, stars, galaxies. I grew up pretty much as an observational astronomer, one who works with the latest telescopes and instruments. Astrophysics means something else to me, actually, the term was coined by the person who built this observatory, George Ellery Hale. He started the Astrophysical Journal because he believed that the twentieth century was going to be a transition from astronomy as an observational science, much in the way of taxonomy, and trying to understand the variety of ‘unearthly’ phenomena we observe and to try to unite that with laws of physics as it was being learned at laboratories on Earth. He saw stars as a particular junction point- what actually is a star, what’s going on? The last half of the nineteenth century was a time when stars were becoming familiar, but the biggest questions, like where does the energy in the sun come from? were unanswered. Nuclear reactions were not understood. So, Hale started the field he called astrophysics, and we use the label now for anything that involves studying the laws of nature in the context of things in space.

This last year I kind of rebelled and tried to convince my colleagues we should start a school of galacto-physics, because there is physics that is particular to galaxies, which although it involves stars, it involves a lot of other things including cosmology. Nobody uses the term cosmo-physics either, and you could consider using that moniker because there is a science of observational cosmology, a vigorous one, done by people who really don't spend a lot of time with laws of relativity or very complicated analysis of what happens in stars. So, you might think that really, astrophysics, galacto-physics, and cosmo-physics are really three branches of which only one has been named. I didn’t persuade anybody; everybody calls everything astrophysics. And the last one you asked me about was?

Zierler:

Cosmology. 

Dressler:

Cosmology specifically refers to the overall properties of the universe: its size, its energy, its dynamical and physical states. In the beginning the universe was a very different place – a plasma sea of particles that are two energetic to live in our cold world. So, whenever you're talking about those kinds of large-scale issues, including crucial physics that describe the universe at early times, one that was completely different than the one we live in today, you call that cosmology. Or, at least, I do.

Zierler:

Alan, before we go back to the beginning and develop your personal and family narrative, I'd like to ask a very in the moment question, and that is one we're all dealing with today. How has the work for you been affected by the pandemic? In what ways has remote work allowed for you to be productive in areas that you might not otherwise have been, and in what ways has the mandates of the social and physicals isolation, where having that interpersonal an in-person interaction, really has stymied the science? What have your experiences been like over these past ten to eleven months?

Dressler:

That's a good question. Since a lot of my work involves writing and running programs on my computer, I have not been affected very much, but where it has been a problem is mostly in the loss of direct contact with my colleagues. Still, we are connecting by Zoom, but something is surely missing. We're keeping up our weekly seminars, so I'm logging into those, but I would say that the casual conversations that go on at the observatory at lunch, the interchanges between scientists, those are not as fulsome on Zoom. That's been a loss. 

Zierler:

It's a loss, Alan, because real science happens as a result of those casual conversations. 

Dressler:

Yes, and maybe real changes in direction and learning about things that are relevant to your own work, things you might not actually hear about. I work with small groups of people, and often by myself. So, I think the effect may be a little less than for most astronomers who are now working within very large groups. Science has become a very big enterprise, in particular because of the big and expensive facilities we need to use. Big research groups have a leg up, I think, in access to those facilities wince the proposals they make support so many people. But in some ways, I think they're more affected by the pandemic because their interactions are more constrained. I could accomplish quite a lot sitting at my computer all day, and then breaking off to watch a seminar, or talk to one of my colleagues. But I think the functioning of these big groups, which might be centered in Santa Cruz or Princeton, but really world-wide collaborations, there will be a lot of people communicating on a daily basis, or at least, they would like to. I think that's been compromised.

Nevertheless, scientists are pretty lucky that a lot of their work can be done remotely. Our observatory has stayed open with all of its people employed and productive through the whole pandemic, but of course we’ve had to work from home and not in our headquarters in Pasadena, and our telescopes in Chile have been shut down much of the time. But we’re still working, still moving forward. So, we're fortunate. 

Zierler:

Alan, the follow-on question, the one that we're all thinking about now is a vaccinated and post-COVID future that we're inching closer toward. That is, what do you see for you and your field? What are the best parts of this experience going forward to keep? What are the things to shed going forward? What are your concerns and sources of optimism for where your field goes in a post-COVID future?

Dressler:

I'll be honest with you, I'm worried less about that than a post-reality future. What's happened in the last year in particular that is much more troubling to me than how we'll adjust to the real threat of future pandemics and health problems that circle our world. The challenge is that global challenge added to global warming and all these other things is the status and politicization of science. It's been a much bigger concern as far as I'm concerned, and very worrisome. In fact, I'd say the last few months in particular have been some of the darkest I've ever spent as a scientist. It's caused me to really think back about when I got into science, what I expected for its effect on my life, but also on the world. Lots of very positive thoughts about how science was going to change the world, not only by continuing to improve the lives of human beings, but also adding so much meaning by understanding where we came from and how the world works. We seem to be in a rather conflicted and maybe dark period now about science's role. There still are plenty of people who believe in science and believe in its approach to solving problems and learning things, but it's now met with a degree of opposition that is, I think, unprecedented.

Zierler:

Alan, I assume you're talking about things like climate change denialism and all of the conspiracies around COVID and all of that, but actually, my question for you –

Dressler:

Yeah, the pandemic has been a perfect expression. 

Zierler:

Yeah, but for your field, for astronomy, how has astronomy been affected by these things?

Dressler:

That's a good question. Well, I don’t think we're ‘going anywhere, we’ll continue the kind of work we’re doing. A lot of people are interested in astronomy, and even if they do no more than dip-in every once in a while, we have maybe a twenty percent base of people who would say, "Oh, that's interesting stuff." And maybe five percent who'd say, "Oh, yeah, I follow that pretty closely." And then a really solid one to two percent who are passionate followers of the field. I hope I’m not too optimistic in my numbers. Those groups probably may not think basic research has been affected very much, but the whole nature of distrust of so-called scientific elites, and attitudes like that, I think that is going to be harmful. It's going to have an effect on NASA and the government's funding of science across the board. Universities, I think, are going to come in for a lot of trouble, or conflict, or what would you say? A lot of issues are being raised right now. I think all those things are going to make any of the sciences more difficult, and that will have a negative effect on science, a long-term effect, more damaging than the pandemic. In some ways, the conflicts that have arisen about the pandemic express this disengagement from science. I look around to other countries who are not as anti-intellectual as the United States, and it seems to me they have done better limiting the damage of the pandemic. We could have prevented the harm to a large extent and have been better prepared for the next one.

Zierler:

For the historical record, of course, we're talking already a month into the Biden Administration. The concerns you're raising, of course, go beyond the Trump Administration. They're bigger than any one administration, and any one political party. 

Dressler:

That's a fair statement. I think the two parties have diverged in how they treat- what would you say- what passes for evidence, what passes for things that you can believe, things that you can use to plan. There's a very big schism in the country now. And you're right. It goes back, I would say, thirty to forty years.

Zierler:

Well, Alan, perhaps on a happier note, let's take it all the way back to the beginning for you. I'd like to start first with your parents. Tell me a little bit about them and where they're from. 

Dressler:

My father grew up in New York City in the twenties. My mother grew up in Lexington, Kentucky. Both of them were children of immigrants who came from Eastern Europe just before 1900. They were both pretty smart people. My father became a dentist. He wanted to become a doctor, but there were quotas for Jews in medical schools that he couldn't quite make it. That had a big effect in my life, in a way, because my father was more interested in medicine than he was in dentistry. So, it caused him to advise me to make sure I did something I really like, whatever that was. He was incredibly supportive in that way. That was the most important thing I had to do, something I would enjoy.

I've been one of those very fortunate people. Unbelievably so, really, all my professional life doing something that I enjoyed, making my living from it, and growing my social interactions with people who are like-minded. I can lay that all at my parents’ feet. They were both educated people. My mother went to college in the thirties and almost got a master’s degree, which was pretty uncommon for a woman in the day, in psychology. They were both well-read, and they respected learning and scholarship more than anything, even though neither one made a living that way.

I often tell this story, around 1954, when I was six years old, there was a night that I came home from school, and we always had dinner together as the nuclear family used to do at that time. There was a buzz of excitement around my parents and my brother, and I that I could not understand at my age. Finally, in the middle of dinner, I said, "What's all this about?" There was such joy and happiness, and it seemed a bit out of character. And my mother said, "Well, something wonderful has happened. There is a doctor who has found a way to stop polio." I didn't know very much about what that was, but they explained it to me. We had a next-door neighbor, a doctor and friend, who had polio, and was affected by it for the rest of his life, and you didn’t have to look far from home to see the damage to people’s lives. I think my parents feared polio as the worst thing that could happen in our future, my brother and I, even though they had lived through many bad things: the Great Depression, two World Wars, the Cold War. Yet Jonas Salk freeing them from the horror of polio was the most important thing that could have happened at that time. I knew at that moment that being a scientist was probably the highest calling, in their eyes, and being a success in business or in some other way making a lot of money didn’t even rate in comparison. 

Zierler:

A scientist, specifically, not even a doctor. 

Dressler:

Oh, yeah. Scientists were people who found new things and made the world better. 

Zierler:

Alan, where did you grow up?

Dressler:

Cincinnati, Ohio. My father had gone to school in Kentucky, and that's where he met my mother. They decided to live someplace equidistant between the in-laws. It was a good town to grow up in. It was kind of a modest size city and had a lot of cultural institutions, and good schools,

Zierler:

When you grew up, it was also a time of strong industry in Cincinnati. Good employment, good jobs.

Dressler:

Yeah, a wide range of companies and academic institutions. Cincinnati was a bit more diversified city than, for example, Pittsburgh and Cleveland, which were centers of heavy industry. Cincinnati, by good fortune, I think, had gotten a wide variety of things: machine tools, Procter & Gamble, meatpacking, and all kinds of things that made it almost recession proof. But the best thing about it was it just had a lot of museums, parks, music, history, that made it a very civilized place to live. That culture fit perfectly into what I think my parents imagined for me. I think that's why they chose it actually. It's a big enough city to have all those things, but not so big as New York or Chicago, someplace where one can get sort of lost.

Zierler:

Growing up, was your family Jewishly connected? Were you members of a synagogue? Were you bar mitzvahed, things like that?

Dressler:

I was bar mitzvahed. We were Reform Jews. My father didn't take very much to religious practices, but he certainly appreciated Jewish life. My mother was more observant, but the family as a whole was not very observant. Didn't keep kosher, didn’t go to Shabbos services every week, things like that. So, while our religion played an important social role, it wasn't so much of the religious role. Some of my aunts, uncles, and cousins, were much more observant. 

Zierler:

And you went to public schools throughout. 

Dressler:

Throughout. One of my proudest things, this was something I was thinking about, I have to give what's called a “golden webinar” in a couple weeks, something that Chilean astronomers have put together during this year of the pandemic, an astronomy seminar series for a worldwide audience. Anyway, I was thinking about the path of my education. Going to public schools all my life, in grade school and high school, and then the University of California, where I was at two of the different campuses, I think a public education, good one, is something I am most grateful for because I was always in a very mixed environment full of all kinds of people and different races and religions, different backgrounds. Maybe I took that for granted at the time, but I think that steered me in a very good direction for the rest of my life. The influence of money and family that I saw in the private schools some of my friends attended was very deemphasized.

Like I said, my parents believed that the most important thing was to do something you loved, and the other things would take care of themselves. You might not get rich, but you will get by, and doing something you love. So, I was fortunate in that. I went to a very good high school that was a college prep school that drew from all over Cincinnati. Good teachers. Had a long tradition, still one of the best high schools in the country. Some great teachers, memorable, that enriched my life when I was just getting started. I got help and guidance along the way that was sort of just what I needed, when I needed it. 

Zierler:

As you tell it, obviously you had a deep respect for science just from your family. I'm curious when astronomy or stargazing captured your attention. Was that early on also?

Dressler:

Yes, I think I had a natural bent about asking questions and wanting to know how things worked. My parents told me I was asking questions at two or three years old about everything I was probably making myself a complete nuisance, but I figured out when I was a little older that they were happy about that, like “the kid's smart, that’s good!” I also had an uncle who was a physicist, actually an important physicist who worked on the development of radar during WWII and afterwards worked with Ernest Lawrence and Luis Alvarez on a “single-gun” system for color television. By the time I understood what Uncle Robert did, he was already neck-deep in highly classified defense work that I couldn’t ask about. He went out of his way to come to Cincinnati every year or two, and he would shuttle back-and-forth between catching up with my folks and introducing me to the world of science. He was a Mr. Wizard kind of guy, very entertaining, so very smart, and very charming – inspiring. Whatever inclinations I had toward a career in science grew and blossomed through the attention he lavished on me with experiments like building simple electrical circuits, making an electric motor, growing crystals.

Before that, when I was five years old, I had been expressing curiosity about the night sky, and one day, my mother found an advertisement in the paper that the Cincinnati observatory, a relic of nineteenth century astronomy, was having a viewing session on Friday night. They did this in the summers, the only time in Ohio when the skies were likely to be clear! She told my Dad, "I bet Alan would like that." So, they grabbed me up and took me out to a big, beautiful park, and I remember waiting in this really long line for what seemed like eternity, and not having any idea what this was all about. But when we got up to the front of the line and I remember this vividly. My father got me by the armpits, and he shoved me up against the eyepiece, the telescope was way up high, from the vantage of a five-year-old. I looked in there, and there was Saturn, just bright and yellow and sharp, an ocean liner piercing the black sky. I was astonished- spellbound. I could see where the telescope was pointed, that bright dot in the sky. But here’s what it really looked like!

That was the turning point. I wrote about this in my book, The Voyage to the Great Attractor. At this point in my life, I was really taken with exploring, and every year they let me go further from the house in the neighborhood. But I was kind of getting a little bored and thinking that I’d already seen it all before, just more streets, other houses. But what was beyond? That night sort of opened things up. I just looked at Saturn and thought, "Well, I'll never explore all of this. This will be there to explore forever." The joy of it just overtook me. That's the simplest way I can explain it. 

Zierler:

What about the space race, and specifically, the moon landing? Were these things really big deal to you as a kid? 

Dressler:

Yeah, I remember when they started launching rockets with the Mercury capsules and I followed it all through the sixties, right up to the Moon landing. I recorded some of the launches and big moments off the radio, and of course, it had a big effect. But I think I realized there was a difference between space exploration and astronomy I was definitely more interested in the mysteries of space. I saw that that's what NASA was after, at some level, but I knew that it would be a long time before much astronomy would come from the space program. Although, getting to the Moon was a pretty big deal because, well, here was this human being standing on a surface of another world: would they sink into the dust? Those kinds of questions, and plenty of excitement and drama. You know, the James Webb Space Telescope is named for the NASA Administrator during that time of the Apollo program. His big contribution, the reason NASA wanted his name on the telescope, was that he put science in the space program. Up until that point, not really part of their mission, there’s nothing in the NASA charter about doing science. It was later rewritten to include science. I believe it was Webb who said, "Without science, space exploration is just tourism." 

Zierler:

Alan, when it was time to think about colleges, were you thinking specifically about pursuing a degree in astronomy or physics? 

Dressler:

Yes, that was pretty much what took me away from Cincinnati, because I knew that all the schools with strong programs in astronomy were either on the East Coast or the West Coast. In particular, optical astronomy and big telescopes is what drew me west. I built a lot of things when I was a kid, including two telescopes. My bar mitzvah teacher asked my parents what he should get me for a gift, and they said, "Well, he likes astronomy." He went out- I don't know how he made the connection, he went out and bought a book on how to make telescope, in particular, how to grind the mirror for a telescope. My parents chipped in with a little kit from Edmond Scientific, and I made my first telescope, with a four-inch mirror, at thirteen, and an eight-inch mirror a few years later. That got me building telescopes, the rest of the telescope, that is, and I thought that was going to be my future, building new kinds of instrumentation for telescopes. But a series of events that happened when I got to California and studied physics at Berkeley, and then at U.C. Santa Cruz where I did my PhD, I wound up shifted away from the instrumentation part, and had to make my living as a research scientist for a long time before I got back to that. 

Zierler:

Where besides Berkeley did you apply as an undergraduate? And were you thinking specifically about astronomy programs?

Dressler:

Yes. but as an undergraduate, it's true, I had other academic interests, so while I applied to Caltech and the University of California, I also applied to Reed College in Portland, not known for its science. I went on a little journey with best friend at the time. We drove out to look at these schools, and I was really intrigued by Reed’s academic program, but I was scared off by how intense a place it seemed. I was quite shy in those days, and I didn't think I could take it. On the other hand, when I got to California, this was 1967, this was the ‘summer of love’ and all that, and the excitement, San Francisco, it was a great time to be in Berkeley. As it turned out, I got turned down by Caltech anyway. They said wasn’t strong enough in math, and that I should apply again next year. But I was happy with going to Berkeley. It was a magical place for many reasons, at that time especially.

Zierler:

Did you declare the major right away or did you take a little time before that?

Dressler:

I tried, but my advisor, an astronomer, Len Kuhi, wouldn't let me! Because I had said I was interested in astronomy, they chose an astronomer as my advisor. The first thing he told me, "Are you really interested in astronomy? Well, you have to be a physicist first. Come see me when you're a senior. In the meantime, you have to take all these physics courses." That was an excellent piece of advice, because Berkeley had many other classes that intrigued me. So, I didn't get really involved in astronomy until the very last year. I took one upper division astronomy class, but Kuhi, my advisor, said, "If you're going to be an astronomer, you're going to have to take all of these courses again anyway, the level of the undergraduate classes isn’t suitable for a professional."

As it turned out, I wanted to stay at Berkeley to study astronomy, because they had an excellent department, but when I applied, they rejected me because it was not their policy to keep Berkeley students. I said, "Well, wait a minute! You told me I couldn’t study astronomy here." They said, "Well, that's true. We guess that wasn't really fair, but you did spend some time around the department, so we think it would be good if you went someplace else. But you know, this place Santa Cruz has a very good and new astronomy department." It happened that there had been an ongoing feud at University of California about the astronomers who lived up at the observatory on Mount Hamilton. Astronomers on the Berkeley and UCLA campuses were unhappy about the fact that these astronomers got to live at the Observatory and didn't have classes to teach or students very often. The conflict was solved, much to their annoyance, I think, by the University administration starting a new department in Santa Cruz and moving the Mt. Hamilton astronomers there. It was a great opportunity to create a department, and it became one of the leading places of astronomy in the world. So, I guess I of got a number of lucky breaks like that. So, I was encouraged to apply to U.C. Santa Cruz, the right phone calls were made, and I got in. It all worked out. 

Zierler:

This is an extraordinarily interesting time to be a student at Berkeley in the late 1960s. Were you political at all? Were you involved in any of the anti-war protests, and things like that?

Dressler:

Oh, absolutely. The People's Park issue and demonstrations, and the big peace march in San Francisco, there were a million of us marching against the Vietnam war. I had a social conscience that had developed quite strongly by that point. I was married to a woman who was very active in the women's liberation movement. There was so much political stuff- I think it all worked well for me. It's been important now, you know. A lot of those feelings and beliefs that formed there, it seems more urgent to follow through with them now. So, I did some demonstrating this year, too- a long time between demonstrations, though. 

Zierler:

Alan, was the draft something that you needed to contend with?

Dressler:

Well, it turned out, no, because I had a heart murmur that had turned into something serious the year I graduated high school. It was to repair an atrial septal defect, when the two atrial chambers are not well sealed from each other. The closing is the last thing that happens before you're born. I had open heart surgery in 1966, which was quite an experience, open-heart surgeries had only been widespread for ten years at that point but because of that condition, I got a deferment. Turns out, I had a high draft number anyway, but I felt bad about that too, a sense of guilt, I guess, because some of the kids I knew went off to the war. Most of them came back safe, but not all.

Zierler:

Alan, who were some of the professors you became close with at Berkeley as an undergraduate?

Dressler:

Len Kuhi, my advisor, and I talked only half a dozen times, but there was an astronomer Hy Spinrad who tutored me with summer project, interesting, but not much of an advertisement for wanting to be an astronomer, and I had some chats with Ivan King, the Department Chair, he was the one who told me I had to go elsewhere for graduate school. That turned out to be ironic, because twenty years later I came to give a colloquium at Berkeley, when I was getting some recognition for my work, and King introduced me, very nicely actually, but when he finished, but before I spoke, Hy Spinrad blurted out “Don’t forget, Alan was one of our students!” and Ivan King’s face went pure red. He didn’t remember me, but I wasn’t surprised or offended. There were a few physics professors: Paul Richards taught quantum mechanics in the Berkeley physics series, he was an excellent teacher, so good that I took a second course from him, and one of the pioneers of CMB characterization working with Owen Chamberlain [who] was a one of the most important physicists of that time, and here he was teaching undergrads like me and pretty involved in “the movement” to boot. I wouldn't say I was close to any of the physicists, but I remember that the breadth and depth of the physics department was intimidating and inspiring to me, at the same time. I had a really tough time in statistical physics, thermo-mechanics, it just never clicked, but in everything else I did pretty good. 

And there were others outside of science. There was John Searle, a brilliant professor of philosophy, the philosophy of language, specifically. He was an amazing intellect with a no-nonsense Brooklyn accent, another great teacher. Searle became quite well-known in the 1980s for his work on artificial intelligence. The two courses I took from him, and the courses I took on oriental art – Japanese painting and Chinese bronzes. Berkeley was a feast of knowledge communicated by those who were the bringers of that knowledge, it was one of the great experiences of my life.

Zierler:

Did you have any formative labs or observational opportunities as a student intern that made a big impression on you?

Dressler:

In astronomy, not really. They dumped some project on me in a summer that was measuring some photographic plates and doing some quantitative evaluations of star images. It was instructive, but it really wasn't very much preparation for what was coming. But the physics labs were interesting. I built a “dye laser” more-or-less from scratch, the dye, in a small glass tube, lased when it was excited with extremely intense, but unphased ordinary light.

Berkeley had all these old things, in this case, storage batteries that were each as big as a loaf of bread, and in order to make this dye laser work, I had to connect a dozen of these batteries, altogether, a dangerous amount energy, and produce an electric discharge in an evacuated glass tube, which ran down a two-inch diameter aluminum tube that I had deformed into an ellipse and polished on the inside. Ellipses have two foci, so running down one axis was the evacuated tube for the spark, while the other axis had the tube filled with dye. So, when “fired” an intense spark of light was focused on the tube with the dye, almost like a fusion experiment, “pumping” the dye into an excited atomic state, and that state decayed in a fraction of a second and the energy came out in a flash of coherent laser light. I'd seen something like this in the magazine Popular Science, so I chose this for my experiment, and it worked! But what was clear, even at the time, was the danger, I could have been electrocuted, there was no supervision! But we had a lot of great lab equipment to demonstrate mechanics, and waves of oscillations, electricity. I really enjoyed that part of it. 

Zierler:

Did you spend any time up at Berkeley Lab?

Dressler:

I had some connection with them, but I never actually got to work up there. Some of the professors did. LBL was mostly about high energy physics and this was not a draw to me. It seemed just too hard, to tell you the truth. Too mathematical, too big in all respects. I did pretty well in my quantum mechanics classes, so I understood what was going on up there, but I pretty much steered clear of it. 

Zierler:

How well formulated were your ideas when it was time to start thinking about graduate school? What kind of specialty you wanted to focus on, what kind of people you wanted to work with? Were you wide open, or were you narrowed down in terms of your pursuits for graduate school at that point?

Dressler:

You know, I think I had been focused on galaxies for a long time. I'm not exactly sure why. Maybe because that was “the universe,” that was my direction, even before I was studying it. So, I went someplace that was exploring the distant universe. That field was just opening up. Astronomers were discovering the universe, in a way, for the first time, because telescopes were being fitted with new detectors that increased their power by ten to one hundred times That was what was needed to see parts of the universe so distant that they revealed its distant past. 

Zierler:

Alan, what were some of those telescopes, at that time, that were demonstrating all of the exciting things that could be discovered with this next generation?

Dressler:

Well, one of them belonged to the University of California. It was the Lick Observatory. That's why I applied to Santa Cruz, in particular, but also Berkeley. There was an astronomer there, Joe Wampler, who was building one of the new generation of detectors. He had served in the Korean War and learned about, basically, things that became radar-related kind of technologies that went into television cameras. In the 1960’s the networks were beginning to broadcast sports at night, so super sensitive TV cameras were being developed. They found their way into astronomy. So, I applied for graduate school to Santa Cruz and also to Caltech, [which had a] world-leading group there, as I remember, I was rejected again! I think I applied for a couple of other places. U. of Arizona for sure, and maybe U. of Texas, and U. of Hawaii. They were all places with big telescopes and good groups building state-of-the-art instruments. 

Zierler:

But Lick Observatory was most attractive for you. 

Dressler:

Pretty much. I loved California. I loved Northern California. I'd been completely indoctrinated, at this point, that Northern California was wonderful and Southern California was the depths of hell. The first two years at Santa Cruz was [great] coursework, the teachers were exceptional, the courses were demanding, and there were smart people taking them, the challenge was good for me. It was an exciting place to be because it was a new campus that was built sort of on a European model of colleges, and at the same time it was beautiful and very “arty” and steeped in the “Whole Earth” movement, this was 1970s and "whole Earth" kind of place. It was like studying in a national park. Most of the undergraduates who went there were given so much freedom, for the first time, but there was so much distractions, including drugs, that a lot of them washed out. I was a graduate student at this point. I knew what I wanted, so I had gorgeous park-like woods, and the ocean, and yet, I had a rigorous program I had to succeed. That kept me focused, very focused. 

Zierler:

Obviously, your vantage point as an undergraduate versus a graduate student are very different, but I wonder, in what ways the divide between physics and astronomy was different at Santa Cruz than from Berkeley. 

Dressler:

Well, Santa Cruz had a strong physics department, and because the astronomy department was relatively small, the two effectively joined. So, I got acquainted with a wide range of physicists, some astrophysicists, but also high energy, condensed matter, nuclear- it was all fascinating to me. As a matter of fact, just to jump ahead, when I got down to Southern California to work at Carnegie, I started going regularly to all the physics colloquia at Caltech. That was really one of the most satisfying experiences of my career, because all the top physicists would come through Caltech, sort of Valhalla. Feynman and Gell-Mann would be ensconced in the front row, encouraging the speakers, and challenging them. To see some of the very brightest people in the world go at it was very inspiring, even though I was working on very different things. I never lost that love of physics. I have tremendous respect for it, and I think I could make my living at it, and I came to respect the primacy of physics throughout science.

Zierler:

Who was your graduate advisor, and how did you develop that relationship?

Dressler:

As I said, there was this guy, Joe Wampler, who was building novel instrumentation, and as my course work finished up in the third year, I had to pick somebody to be my advisor for the PhD thesis. I kind of leaned on his door and said I'd like to work with him. He had just finished building another one of these detector systems for a spectrograph on the Lick 120-inch telescope at Mt. Hamilton. As I mentioned, there was great excitement and potential for new kinds of research because the new systems were ten times more sensitive than using the photographic emulsions that preceded them. Wampler was very strong technically, but I came to think of him as a mediocre astronomer, he didn't really offer me any ideas about what to do.

About that time, there was a lot of talk about “missing matter” in clusters of galaxies, what we now attribute to “dark matter”. There were only a couple of clusters where this had been demonstrated, and people wondered, it made no sense that the galaxies in these clusters were whipping around at such speeds that they should escape the gravity of their clusters, yet that was clearly not happening. It was a real puzzle, perhaps the first of many crazy results in astronomy that have followed, like supermassive black holes, dark energy. So, my project was to use the spectrograph, fitted with Wampler’s sensitive detector system to study some more clusters. There were few measured and dozens more we could do. In fact, I started working with him on just a few additional clusters, but unfortunately, for me, Wampler was preoccupied with quasar research, finding the highest red-shift quasar, an exciting prize, and he knew little, nor was very he very interested in the project that he had in-effect chosen for me. I spent fifteen minutes trying to tell my wife Charmeen the other night about the story of how Jim Peebles was sought out, after a colloquium he had given at the department to bless my thesis project. Because Joe Wampler wanted him to endorse the idea, I was trotted out to a lunch and a dinner I could not afford with two dozen faculty, and I the only student, to talk to him about it. When dinner was over I had my three minutes to describe the project. He gave the blessing: "Yeah, that sounds like a good thing to do." And we were off. But because he wasn’t very interested in the subject, I was a bit adrift working with Wampler.

There's a story that I told recently at a conference on “multi-object” astronomy, a crucial technique for studies of galaxies. It was a night on the 120’ allocated to Wampler and I came along to do a little (very little) of my thesis research. Sandy Faber, who had joined the faculty in 1973 as a young “star” came along to see Wampler try out a new 2D version detector system. I was always given the last hour of the night, when the sky was brightening with the dawn, to target a few galaxies. As I said, my advisor was not very interested in my thesis program, even though he had “validated” it by one of the most respected astrophysicists of that time. And we were looking at the screen of this new device, and you could see- we were on one of the clusters of galaxies- you could see, most of the galaxies in the field were shining back at us. First time I'd ever seen an electronic picture of the sky, but then there was a hole where the light from the one targeted galaxy disappeared into the spectrograph. I said, "Gee, how come we can't get the light of all these other objects we see into the spectrograph, which I now realized had a 2D detector?"

It occurred to me that if the light from the galaxy next to that one was bouncing back to us, couldn’t we have another aperture to send it’s light into spectrograph too? And all the others! Before we didn't have these two-dimensional detectors, so you really couldn't have done that. So, I said this to Joe and Sandy, and what I remember was getting a dirty look from Wampler, sort of like, "Shut up and do your galaxies," but Sandy Faber sort of smiled and said, "Yeah, that's a pretty interesting idea." Of course, this moment stuck with me for the rest of my life.

About seven years later, when I got to Southern California, I was working on the 200-inch Hale telescope at Mt. Palomar I was working with a very important astronomer, Jim Gunn, who had just built a spectrograph with a new kind of CCD detector that went on top of the telescope – the “prime focus.” This time the telescope and instrument were perfectly suited for this idea of multiple objects at one time: the “PFUEI” (Prime Focus Universal Extragalactic Instrument) had an easily accessible field – the focal plane, we call it, where the telescope focuses the light, because PFUEI was both a camera and a spectrograph. I was thinking, okay, here's finally an opportunity to do this. So, I made the first multi-slit mask, one that covered ten galaxies at a time instead of just one. We were observing galaxies so faint that it took hours of observation to get a spectrum, even with the 200-inch telescope.

Well this technique had a big effect on astronomy. Today, multi-object spectroscopy is one of our most important techniques – thousands of galaxies can be studied at the same time with the right type of instrumentation. I learned later that there were some other people working on this idea, mostly using fibers to collect the light, but I think it’s true that we had the first important piece of science to come out of multi-slit spectroscopy: that first paper has accumulated 693 citations so far – that’s a lot of citations. A few years later, Sandy Faber reminded me that I had thought about this years before- "You know, you invented that." And I said, "Huh? Oh, yeah, that's right. I did." I guess I had sort of forgotten about it, but it had been buried in my mind for all those years.

Zierler:

Alan, looking back, what were some of the principal conclusions of your thesis research, and how are they responsive to some of the bigger questions in the field at the time?

Dressler:

I don't think they were very responsive, actually. The whole business that my advisor sent me off on, measuring the missing mass in clusters, other people were doing that too. More clusters were shown to have the same problem, so nobody knew what it was. The effect was shown to be real, but astronomers were still skeptical that there could be something as mysterious as “missing mass.” Eventually the idea of dark matter thing came along, based on another independent observation that Carnegie scientist Vera Rubin made that individual galaxies have more mass than is “visible,” that is, emitting light, like stars and glowing gas do.

So that issue resolved eventually, but I didn’t have much to add to the story. But in the process, I wound up studying what were called the luminosity functions, the distribution of light (and the implied mass) for cluster galaxies. How many big galaxies were there compared to medium size and small? And was that universal? Jim Peebles, I think, had been the one who suggested it was just a universal function, just as a starting assumption, really, but sensible. Why that was important was, it suggested that there was nothing different about environment that caused the numbers of galaxies, how many big ones, how many small ones, to be affected by whether it was a very dense cluster, a very low density, a very massive cluster, a not-so-populous cluster. Nothing substantial differences had been found. I did find some very minor differences in “luminosity functions,” but I didn't find anything substantial – at least, that was my conclusion at the time.

However, that did, actually, lead me to something important. I thought my thesis was rather boring, and that in itself was okay. I've always believed a thesis topic really shouldn't be to do your best work, but just to show you could do research. I had done a sufficiently careful job to show that the luminosity functions were almost all the same, and not tried to claim anything too bold, but in fact did lead me to a Carnegie Fellowship. This whole question of environment. Sandy Faber helped me think it through, what I could do with the new telescope Carnegie had built, and put together this whole question of what are the environments of galaxies, and how does it affect how they were born, and what kind of galaxies are found in different environments, and eventually, why?

Zierler:

Alan, when you use the word environment, it means something very specific. Can you explain a little what that means in this context?

Dressler:

To explain what I’m talking about I need to jump forward a few years to my work as a Carnegie postdoctoral fellow. What “environment” means, in the large scale of the universe, is the density of matter in the region, that some places are born with a high density of galaxies, crowded, in astronomical terms, and some in relatively empty regions, low density environments. We understand that whatever we see late in the universe is telling us something all the way back to the beginning, gravity works just one way. If a galaxy is in a dense environment in today’s universe, it's likely it was in one of the densest places early in cosmic history, relatively speaking. An “over-density” (more dense than average) grows in amplitude as the universe ages, and so do the “under-dense places” – voids. The patterns sustain, growing in contrast, as the universe grows older and expands, which seems rather contradictory, but is true. So, with Sandy Faber’s suggestion, I was looking at the question of morphology and environment at Carnegie: what kinds of galaxies are born where?

I came up with a very clear relationship between the morphology of galaxies and the density of their environment in these clusters of galaxies. It was such a stunning correlation that it brought me my first real recognition as a scientist. It was called the Morphology Density Relation, sometimes called the Dressler Relation. My colleagues were surprised, because they believed that dense environments in clusters were ephemeral, that is, as these galaxies circulated at high speeds, what appeared to be dense environments would evaporate and new ones appear. But if that was true, there couldn’t be a correlation with the types of galaxies (spiral, lenticular [S0], elliptical) because the galaxies couldn’t rapidly change their appearance.

So, my study, which involved taking wide-field photographs of 50+ rich clusters of galaxies with Carnegie’s new, superb DuPont telescope, in effect, the widest field, most sensitive camera in the world, said that environments, sparse or dense, were what galaxies would experience for all their lives. People were surprised because they thought that it was basically suggesting that this universal process of galaxy type and density happened everywhere because galaxies were being transformed by their interactions, turning a spiral galaxy into an elliptical galaxy in dense environments. This relationship between type and the density of galaxies reflect what was going on when these galaxies were infants: an elliptical galaxy was destined from birth because of the dense environment in which it was born. That turned out to be right, but for years and years, and even today, people still credit me with showing that environment matters, but they think that environment at the time that we’re observing them, and that galaxies are being changed from one type to the other. I never believed that. Even though people read the paper, they never got to the point where I said, “No, it can't be that. It has to be the early environment, not today’s environment that is responsible.”

So, that really did set the course of my research for my career, because even now, I'm sort of looking at that same question. I'll use the James Webb Space Telescope to see how the galaxies were forming at the very earliest times, and we'll see what effects the merging of galaxies have, for example, and what kinds of effects galaxies have on each other just by interacting, in the very first half a billion years, when the universe was very young and galaxies were just forming. So, I've always believed that the initial conditions are mostly responsible, and that they manifest themselves late. 

Zierler:

Alan, after you defended, what were some of the most compelling post-doc opportunities you had to consider?

Dressler:

I got a number of offers, but the Carnegie offer was a shock. I never imagined that I could get a Carnegie Fellowship. I think Sandy Faber wrote me a glowing letter. She had much more faith in me than I had in myself, I thought mine was boring thesis. There’s definitely a post-partem thesis depression. You’ve been intensely focused on something for years, you’re not sure if it really mattered, and it is often true that you now know more than anyone about this one subject, and others may not really understand or care. I was in fact very down for a while. I thought maybe I could go back and study architecture, like I thought I would, before I had to choose to go on in astronomy. I was just completely amazed when I got a Carnegie Fellowship. At that time, Pasadena was still the center of the universe, as far as astronomy goes. 

Zierler:

That was really the place to be for your field, to go to Carnegie. 

Dressler:

Yes, and Caltech. They were united in this, that was a strong axis. 

Zierler:

I wanted to ask on that point, what exactly was the Caltech-Carnegie relationship when you joined as a post-doc?

Dressler:

It was called the Hale Observatories when I was a post-doc and had started out as Mount Wilson and Palomar Observatories. In astronomy, two institutions were more-or-less defined by the observatories. It was a rocky relationship from the start, because the Rockefeller Foundation made a grant for the 200-inch telescope, but it didn't want to give it to Carnegie because John D. Rockefeller apparently disliked Andrew Carnegie. So, the Foundation gave the money to Caltech, even though pretty much everyone who knew how to build this telescope was at Carnegie. So, although these two excellent places were engaged in this joint enterprise, there was some acrimony and jealousy right from the start. Caltech didn't have an astronomy department per se at that time, so the Carnegie side held some resentment, I think, that new people were hired to use this telescope which they thought of as theirs. By the time I got there, some forty plus years later, there were several battle lines drawn between the two sides. Just as I finished my post-doc in 1980, they split apart and went their separate ways, to the benefit of both of them, most of us think. But it was not what I would call an amicable divorce.

Zierler:

Where was your funding coming from for the post-doc? 

Dressler:

The Observatories of the Carnegie Institution have long had a few postdoctoral positions at a time where a young astronomer was given free rein to follow their passion, astronomy-wise. A Carnegie Fellow was considered to be particularly fortunate because the observing facilities have always been first-rate and time on the telescopes was generously allocated to the Fellows. When a grad student at Santa Cruz, I had heard that one of our new PhDs had received the Carnegie Fellowship, and I remember that all the graduate students said, "Wow!" So, I was thrilled to get that opportunity. There weren't many positions like that in astronomy, most post-docs were working for more senior astronomers. But with the Carnegie Fellowship, it was “you come here, you have two years, you buckle down on research, and we'll give you whatever you need.”

After the two years I got sort of a more senior fellowship that had been created, a “Las Campanas Fellowship,” So, all told, I had four years of "whatever you need, you do what you want." And then I became a staff member, and I got to spend the rest of my career in this wonderful place that focuses almost exclusively on research, provides the resources that its astronomers need, and lets you follow your own star, so to speak. Of course, you’re on your own, mostly, so you have to figure that out for yourself, which is pretty much what Andrew Carnegie had in mind, I think, the kind of scientists that needed to follow their instincts and pursue whatever they found interesting, free of federal grants and the popular, trendy subjects they support, and unoccupied with teaching and other responsibilities of university faculty.

Zierler:

Alan, did this initial appointment put you on a non-professorial track? Did you get that sense from the beginning that that's where your career was headed?

Dressler:

I guess, I thought at the beginning, I was just going to spend a couple years in Pasadena, and then people were going to find out how stupid I really was, and I could go back and teach someplace. That didn’t sound so bad. I liked teaching. I had taught my own course in graduate school, “Architecture of the Universe,” so, I didn't think that would be bad at all. And I thought, I'd always be able to brag that I worked on the big telescopes, and I had hobnobbed with the elites of the field, and I don’t think elite is a dirty word. In fact, in my first years at Carnegie, another guy and I taught a course at Occidental College just about the time that Barack Obama was there. So, I tried to keep my hand in it, but really, it wasn't possible to take full advantage of what Carnegie offered and teach well. But even after a couple of years, I thought I might get an offer from Caltech, and I did eventually get offers from U. Texas and U. Hawaii. I got an offer from Carnegie before I heard from Caltech, I wasn’t optimistic, even though I was on the short list, and from there on I gave up on teaching. I was sorry about that, but I tried to keep the spirit alive in public lectures, writing articles in popular magazines, and speaking to lay audiences at many universities and science museums.

Zierler:

Alan, intellectually, when you got to Carnegie, did you see this as an opportunity to continue on with the broad range of work you were doing as a graduate student, or was it time for new projects, new things to think about?

Dressler:

I had already made that break when I came to Carnegie. The world sort of opened up. Santa Cruz was a wonderful place, but in some ways, it was very sleepy at the time. The academic environment in Pasadena was in comparison very dynamic. The people working here were very hungry, dedicated. They were all working on these observational projects on the stars, the galaxies- the stuff I wanted to be doing. Santa Cruz, like most departments, was spread very thin over many disciplines, as you have to do when you educate graduate students in particular. So, there is never much horsepower in any particular direction like there is in a place like Carnegie. So many trying to figure out the history of the Galaxy, how stars are born, age, and die, and how it all fit together in an evolving cosmos. This had been a mission since Edwin Hubble and George Ellery Hale had been here, among many remarkable astronomers.

So, there was a whole enterprise here, and then, great people at Caltech too, some of the smartest physicists in the world. I was inspired, energized, blown away – my whole career just opened up. Once upon a time I couldn't think of anything to do, after my PhD, when I applied for the Carnegie Fellowship. I needed Sandy Faber's help with that. But from that point on, I was always thinking up things I wanted to do – more than I could take on actually, and that made my professional life very exciting. And I turned out to be a creative and productive scientist, more than I dreamed I could be. 

Zierler:

Who were some of the key people you worked with, both senior and your peer level, when you started at Carnegie?

Dressler:

Well, Allan Sandage was the first Carnegie astronomer I worked with. He was an icon, perhaps the most important observational astronomer in the world in that era. We did some studies on galaxies that were intended to take advantage of the DuPont camera and compare the basic properties of galaxies of different morphological type. I would say that he was influential because he was a very smart person, knew the history of the field exceedingly well, and had an encyclopedic knowledge of astronomy. But he also had a very strong and domineering personality, somewhere between confidence and arrogance, and that got him into fights with a number of other prominent astronomers. So, our collaboration worked out for a while, but he seemed to want only disciples, not partners in research, so it didn’t last but a couple of years.

Then, there was another very accomplished, extremely smart, diversely talented professor at Caltech, James E. Gunn, who expressed interest in my work and offered to collaborate on the Hale telescope with some revolutionary equipment he had built. Jim is one of these guys considered as a triple threat: he was a theorist, and observational astronomer, and a person who builds designs and instruments – a rare combination.

Zierler:

How did you connect with Gunn initially?

Dressler:

That's a good question. I think- well, I used to go to all the colloquia at Caltech and that’s where we started to talk. (We didn’t have any at Carnegie when I first came there, but I started a Carnegie colloquium series a few years after I arrived, and I ran it for the first ten years.) He was studying things I was interested in, in particular galaxies at “high redshift,” meaning galaxies far away from the Milky Way whose spectra were ‘redshifted” by the expansion of the universe, and for which we looked back in cosmic time. This was the beginning of reaching back a significant fraction of the age of the universe – there were amazing developments in detecting light that made our telescopes seem to grow by factors of ten to one hundred. Gunn was one of the chief scientists on the team to build the camera for the Hubble Space Telescope, so he was right in the thick of this “detector revolution,” and it allowed us to do things that had not been dreamed of before.

I’m not exactly sure how it started, but Jim was a very friendly guy, and he was easy to talk to, very accessible for such a brilliant guy. When he heard what I was working on and what I wanted to do next, he simply took me under his wing. We had a great relationship, and I learned as much from him as anybody I had ever worked with. It would have gone on a lot longer than the five years or so we collaborated, but Gunn had become disenchanted with Caltech, and he left to go to Princeton, and with the distance, before e-mail and the internet, and his responsibilities with the Hubble camera, it fell apart for us. But he was a very positive influence in my career.

There were of course other people that I talked science with, for example, Leonard Searle and Steve Shectman at Carnegie and Wallace Sargent and J. Beverly Oke at Caltech. They were all very inspirational people. And, during my early years in Pasadena, the crop of postdoctoral fellows, at Carnegie and Caltech, were truly remarkable – all of them went on to important positions in the field and discussing science with them on a daily basis was a real wellspring for ideas. But at the same time, at Carnegie in particular, being independent and doing your own research was very valued. So, even though I had collaborations with Jim Gunn, and continuing work with Sandy Faber – real partnerships, I was taking the initiative in many other studies that I mostly carried out by myself. The Carnegie environment and the superb facilities made that possible. So, you look at my papers from the first ten years, most of them are single author papers. I liked that. But things changed after the Hubble Space Telescope became arguably the most important resource in astronomy. People who enjoyed working alone became almost obsolete. Most of the science has become “big science” and the big advances rarely comes from individuals or from small groups. But I have never felt either as comfortable or as productive in that environment, with dozens of other colleagues working together, so I think that has limited what I could accomplish in the last ten or fifteen years.

Zierler:

What do you think explains that?

Dressler:

Why I feel that way, or why it's gone that way?

Zierler:

I mean, why it's gone that way, that's part of the bigger narrative of big science, right? But for you, intellectually, why has it always been more productive for you to work on your own?

Dressler:

I think a lot, and the problems we work on involve a lot of thinking about riddles and puzzles. These big groups really have to outline an agenda that's very specific. They take this problem, and they outline how they're going to solve it. They organize a program with big ambitions, not just steps, often involving large allocations of major facilities, the Hubble Space Telescope, the biggest ground-based facilities, other space telescopes like Chandra – an X-ray observatory. Usually these plans include vast surveys of galaxies that cover all the bases of what they expect, instead of targeting certain samples of galaxies that can inform a particular, important question. And they have to put together plans that, to me, don't offer much opportunity to discover anything. Too much has been anticipated and planned for and there is, I think, little of the effort that can go to exploring without expectation. I have to say that I've been extremely lucky. I've discovered all kinds of things in astronomy, including the first really convincing case of a big black hole in a galaxy, the Andromeda galaxy, the closest galaxy to us. I had good equipment. I was going to try to find big black holes in active galaxies that are called Seyfert galaxies.

But I had to get something that I thought didn't have a black hole, so I looked at the Andromeda galaxy, and found it had the biggest signature of- stars were speeding up at the center, and that had to be the result of a huge mass, because there was also a strong rotation of the stars around the center, which eliminated other possibilities. What was most significant about that was this was that Andromeda is closest big galaxy to us. If Andromeda had a big black hole, I reasoned that perhaps they all did, and early on, I suggested maybe the size of the black hole seemed to be correlated with the size of the bulge in the galaxy, which has turned out to be one of the most important relationships in this subject, one that continues to baffle us to a large extent- and I discovered that. These were opportunities that were given to me, and I spent a lot more time just thinking about this kind of stuff. I don't see that in those big collaborations. As I said, they have a program, it’s all laid out, and most of the effort goes directly into executing the project they proposed. I'm in a couple of such groups, one is the principal camera, NIRCam, for the soon-to-launch James Webb Space Telescope, and that team has joined with a European team building the NIRSpec (the spectrograph) for Webb, so altogether it’s a hundred persons or more. And I haven’t found people on those teams very interested in what I’m doing for the program, or what I’m thinking about the science, maybe because they all have their tasks, and they’re terribly busy being the functional parts in this big collaboration. There really isn't much time to speculate and wonder, especially to wonder about whether we're going in the right direction. For me, that's a disadvantage of doing big science with big teams. There isn't the cauldron to cook the ideas, and that's still the most exciting part of it to me. 

Zierler:

Alan, how did the Las Campanas Fellowship come about for you? 

Dressler:

The Carnegie faculty realized, I think, just about the time that Carnegie Fellowships, which for decades had been two-year positions, carried a too-short term for the kinds of programs that they wanted their postdocs to carry out, and they didn’t just want postdocs to carry away lots of data that had yet to be analyzed to some other place, where the papers would be finished and published. Carnegie realized that, one, it would be good to let at least some of their postdocs to stay longer, to finish more of what they had started. Adding the possibility of a Las Campanas fellowship meant you might have as much as five years to finish what you were working on. It wasn’t long afterwards, however, that all Carnegie Fellows were given three years with the possibility of extension if warranted, and then the Las Campanas Fellow position was dropped. Part of this change, David, was because the very idea of what a PhD thesis was, and how more ambitious research programs, in general, had become. When you were studying a particular type of star or galaxy, you could hope to come here and do that in two years, publish a good paper, and go on to the next phase, or the next thing. By the time the people coming to Caltech and Carnegie really had enormous goals that seemed to follow from their PhD experience.

Zierler:

Physically, where were you located for these years?

Dressler:

Always in Pasadena, right here. About thirty feet away from where I am right now, in another office. 

Zierler:

Was this a fellowship that you took with the understanding that you would be joining the staff proper, or was that up in the air at that point?

Dressler:

Oh, very much up in the air, in fact, they hadn't had a new staff hire for quite a while. Those positions were so cherished, given that they were, as I said, like a lifetime fellowship. There were hardly any places that had something like that. It was really a fellowship-for-life kind of opportunity, only it paid better. The Las Campanas Fellowship was sort of a launch pad for me, because after a third and fourth year at Carnegie, I had enough of a portfolio of good work and results that I could look around for permanent position at a good place. I don't know if you need to hear this story, but my brother, David Dressler, who was an extremely accomplished molecular biologist, had been caught in a bad political crossfire at Harvard that prevented him from getting tenure. His PhD advisor was Jim Watson, the co-discoverer of the structure of DNA.

As a student of Watson, my brother also had quite a portfolio working with Watson a few years after his PhD, and other institutions were interested in hiring him as an assistant professor. But Watson dissuaded him, assuring him that he would see to it that he would get a professorship at Harvard, and that was everything my brother wanted. But before he actually came up for tenure, Watson left to run Cold Spring Harbor, and he didn't take David with him. Without Watson’s support, the position went to another variety of biologist. My brother was very angry about this and felt Watson had squandered his opportunity, his moment. So, when he found out that I was in the same situation, when I told him I wasn’t worrying about applying for positions before I had to, even though I was becoming well-known, he very unkindly dressed me down and said, "You have to go out and get a job right now. Decide where you want to be, and then get an offer for any good position, and use that as leverage to get where you want to be." I had little choice of whether to fight my big brother on this, so that’s exactly what I did- it was not of my nature to do something like that, but I did it.

Zierler:

Turned out to be good advice. 

Dressler:

Yes, it was. I got offered assistant professorships at the U. of Hawaii and the U. of Texas. And then I made it onto a short list for junior faculty at Caltech. I was casually chatting about this one day with the director and assistant director at Carnegie, George Preston and Leonard Searle, they wanted to know how my job search was coming. I told them, and then spontaneously I added, "You know, Carnegie is the place I'd really like to be. So, if I get the job at Caltech, and accept it, do you think I could come back to Carnegie if you there is position open?" But by this time the two places had just split up, so they said, "No, we don't think so," and explained that “stealing faculty” would be the last thing they would want to do at that juncture. Actually, I think Caltech would have done it if the situation was reversed, but Carnegie people also considered whether something was the right thing to do, in addition to “in our interest.” They said, "But look, that doesn’t matter. If you get the job, take it, Caltech is a great place to be and you will be happy there."

And I, in the greatest moment of chutzpah in my life, blurted out, "Well, since this is really where I'd like to be, I think you ought to hire me now." They were startled, erupted into laugher, and said, "Go away. Just go away, Dressler." And in short order, I found out, they wrote a letter- this is the kind of thing you could do back then, to the president of the Carnegie Institution and said, "We have this opportunity with this young scientist..." And a few weeks later I was offered a staff position at Carnegie – the job. I told my brother about this, and he said, "Ah, yeah. Okay, you did okay." He really didn't know Carnegie from a hole in the wall – no biology – so it was not a big deal to him, but he realized it was what I wanted, so “okay.”

Zierler:

What were you doing with regard to galaxy morphology at this point?

Dressler:

I came to Carnegie late in 1976, and by the summer of 1977 I had started to carry out the proposal I made when I applied for the Carnegie Fellowship, which was to determine the morphological types of galaxies in a large sample of galaxy clusters, a few hundred galaxies in each. As I said earlier, Carnegie had commissioned a new telescope the 2.5-m DuPont just after I arrived. It had a very big field of view, much bigger than the size of the moon, but also had all the magnification of the Palomar 200-inch telescope. This meant I could determine the types galaxies in distant clusters the way nobody could do before. Previous telescopes with a field big enough to cover a cluster had low magnification, so you couldn't see the detail of what kind of galaxies they were. So, I selected about fifty clusters and went to the Las Campanas Observatory in Chile to begin the big task of taking plates for all of them. I can show you one- they're right over there, under that table, in big yellow Kodak boxes. These plates, twenty-inches on a side, were giant compared to what had been used before- big pieces of glass a one-and-a-half millimeters thick coated with delicate photographic emulsions. Believe me, they were difficult to handle in the DuPont darkroom, and I couldn’t use a red safelight to see what I was doing, these plates were too sensitive to light of any color. I never had any experience for any of this, and I had to figure it out on my own. I sliced up my fingers pretty good trying to handle the ~100 photographic plates for this project, and it was a real problem even getting them back to Pasadena, too. A hair-raising, funny story I have told many times.

I was the first person to use the telescope because only the ‘direct camera’ was finished – the other instruments were a few months off, so on my first observing run I had the telescope for two weeks, that was not even common then and certainly not possible now. And most of the nights were spectacular, clear with excellent seeing– that’s how astronomers describe the turbulence in the atmosphere that affects the crispness of the images, and I was amazed right away how clearly I could see the details of individual galaxies. Our shop constructed a light box I used for inspections- it's still sitting here. See that? We modified a drafting machine and attached it to the light box, and I went carefully through those plates months after month, measuring the positions of each galaxy, its morphological type, and other things, how bright was the galaxy and how big was the “bulge” compared to the “disk,” and writing all this by hand in notebooks and finally giving them to a person over at Caltech who transferred all the information to computer punch cards. Do you remember them? When all that was done, the cards were fed into an IBM computer that ran a computer program I had written, this was primitive stuff compared to what we do today, but it was state-of-the-art then. That's when I found the relationship I talked about earlier, the morphology-density relation. I started with investigating what other people had been doing, comparing the proportions of different galaxy types to how far they were from the center, cluster by cluster. There was a trend in my data, as others had found, but it was unimpressive, sometimes strong, other times weak. At first, I was terribly disappointed, all this work, better data than had ever been used for this kind of study, and lots of it, but nothing new!

Then I remember what I had been thinking, as I went through the plates for all those months, the morphological types of a galaxy depended, it appeared, on how many neighbors surrounded it – the local density of galaxies. Where there were lots of galaxies around, few of them if any were spiral galaxies. Instead, most were round balls of stars called ellipticals and their cousins, S0 galaxies, both types showed little or no sign of the star formation we see in spiral galaxies. Spiral galaxies, on the other hand, were found in abundance only in sparse areas. I asked one of the Carnegie staff, someone I very much respected, what he thought of that, should I try to investigate it this connection to local density? He didn’t think it would be worth it. As I told you earlier, astronomers who worked in this field thought these dense clumps of galaxies were transient, so they couldn’t be correlated with what kind of galaxies they were. I was really deflated and I tried for another week or so to come up with something else. But really, I had run out pf ideas, so I wrote a program for the Caltech computer that calculated the local density around every galaxy, how much area do the nearest ten neighbors cover, and waited a day for a ream of computer paper that correlated the type of galaxy with the local density.

What I had suspected was remarkably clear. For all clusters in the sample, the elliptical and S0 galaxies favored the dense places, the spirals the sparse places. A strong relation, and “universal” - everywhere I had looked. I was surprised, boy was I surprised, and I was elated. To find something previously unknown that is so clear says “you have solved the puzzle of this one corner of nature. You have understood it.”

That work was a turning point. It got me noticed in a big way, but it also provided a wealth of data for more studies of galaxy properties in relation to environment. My colleague Steve Shectman had built a very sensitive detector system for a spectrograph on the DuPont, which we used to take spectra of 1268 galaxies that were in the fields of 15 of the fields of my morphology study. We used those spectra to intensity and character of the star-formation in these clusters galaxies, that is, connecting the appearance of galaxies with their stellar populations and the history of star formation. From the spectra we also measured the “redshift,” which told us the relative velocities of these galaxies as they moved around the cluster. I used that information with a novel statistical test I invented to show that the clumps of galaxies in the clusters, as the morphology-density relation indicated, were not transient, but that these denser regions were “sub-clusters” that remained intact over billions of years. This and some other work led to a study with the Hubble Space Telescope by a small team I led to investigate the same morphology/environment/star-formation properties of very distant clusters of galaxies, so distant that they were seen as they were four billion years ago, which added an “evolutionary” dimension to the study of galaxy morphology and star formation with environment.

The data from the Hubble, with its view of galaxies almost 1/3 of the way back to their birth, provided for me more evidence that the morphological types of galaxies were established very early in the history of the universe, not later as, for example, they fell into clusters of galaxies, as many had thought. The Hubble images were revolutionary because you could see evolution of galaxies in an image, a picture. You didn't have to make a lot of measurements or go through a lot of calculations. With Hubble we could see that at about ten billion years ago, three billion years after the Big Bang, the galaxy morphologies all look ragged and strange, the types we see today were not at all common, but that within the next few billion years, the galaxy types we see today became well establish, before the universe was “middle aged” and certainly not as late as the epoch we live in.

Zierler:

Alan, just to broaden out the discussion a little, in the early 1980s, were you paying attention to all of the excitement surrounding inflation?

Dressler:

Yeah, I was very fortunate because I made several visits to Cambridge University in the early eighties. It is one of the power centers of astrophysics and was a crucible of early work on how dark matter controlled the birth and growth of structure in the universe, in particular “cold-dark-matter.” The team of Davis, Efstathiou, Frenk, and White – the Four Horsemen they were called were in Cambridge quite a lot, and they were arguably the major proponents of this model. I was lucky enough to hear it all from the horses’ mouths, so to speak when I was there. It wasn't clear at the time how it impacted my research; I was keenly interested in how the origins of the “age of galaxies,” but it turned out to be highly relevant. These were ideas about the smoothness of the very early universe and how early fluctuations grew enough to seed the formation of galaxies, these ideas were wrapped up in the notion of an epoch of inflation where the size of the universe grew exponentially in the first fraction of a fraction of a second, that was a requirement if the universe we see today were to exist, which it does! In fact, at that time, astrophysicists were looking for these fluctuations in the “microwave background,” the light that emerges from a time before galaxies, but not finding any.

The fact that we knew they had to be there because they grew into galaxies and galaxy clusters today, but we couldn't actually see them with the extremely sensitive microwave “telescopes” we had on the ground and in space, was incredibly puzzling. So, there was a lot of talk about how the fluctuations grew fast enough over cosmic time, and, it turned out that the major answer to that conundrum was dark matter. The fluctuations were in fact there but tracing the dark matter. The baryonic matter hadn't responded to the growth of structure in the dark matter, so the fluctuations in microwave light were hundred times weaker. But at the same time, this whole question of how the fluctuations ever grew to be the galaxies we see today were was absolutely dependent on the universe having this inflation period, because otherwise they wouldn't be remotely big enough to form galaxies and clusters. I met Alan Guth in MIT, and I remember talking about all this, and I was convinced almost right away, even though it was a hard thing to believe and even harder to prove. 

Zierler:

It still is. 

Dressler:

But it was very exciting, both dark matter and inflation. The mid-eighties were hot times in the field of cosmology!

Zierler:

Did you see your work in galaxy formation and evolution as feeding into those larger questions about the start of the universe?

Dressler:

Absolutely.

Zierler:

In what way?

Dressler:

Well, in the sense that I was picking up the story at a later time. I knew I needed those things to happen, and I wouldn't have been satisfied and said, well, you've got your fluctuations. What happens to them? I am a big story kind of guy. I already was thinking about the issues that came out in that material I sent you about, the HST & Beyond report. I was already thinking about this origins question, and what were the key steps? When people talked about origins in terms of the particle universe, I said, "No, no. You're never going to convince me that what happened in the first three minutes is really crucial to us being here." But galaxies, I felt, this really was the first thing that happened, which if it hadn't happened, we wouldn't be here. That's very interesting because dark matter is not something hidden by its complexity, whatever it is, dark matter is the simplest of things. But dark matter was necessary, because of the size of those first fluctuations, to bring the baryonic matter together, and then gravity concentrated them in the formation of stars. With only a small adjustment in things, you never would have had stars and galaxies. First, you needed galaxies and then stars. Otherwise, the universe would have just dissipated, and maybe a lot of universes have done just that, somewhere.

Those would-be universes without enough complexity to lead to life, which is the most complex thing we know of. So, I started making this argument pretty early that looking at the birth of galaxies was crucially important, because that was, to all intents and purposes, our origin. Of course, that was because of the chemical composition, the heavy elements that the stars make, which enables the complexity, but also because if there hadn't been galaxies formed at this epic, nothing complex would have come about. And then you connect that back to the physics. Of course, you wouldn't get these right conditions of dark matter and baryons if you hadn't had the first three minutes. But in one case, you could sort of draw the line directly from us to the formation of planets and life. It was very hard to do that from the conditions in the first 10-24 seconds, or even first three minutes, even though that connection is there. 

Zierler:

On the question of thinking about the situation where galaxies are conducive for life, did you ever see your work as relevant for astrobiology?

Dressler:

Yes, I did. This Origins program brought me into close contact with astrobiologists at that time. After the HST & Beyond report, NASA reorganized its astrophysics directorate and created the Origins program. So, they had an Origins sub-committee, and I was chosen as its first chair. Astrobiology was coming into its own– remember all the excitement about the Mars rock with the supposed little worms? That was what NASA Administrator Dan Goldin was really interested in when I was led into his office to pitch the big cryogenic space telescope that became the James Webb. So, I had a lot of contact with those scientists. There was a prominent group at the NASA Ames Center, and my committee was worried about how to expand and fund new facilities that allowed astronomers to look for life on other planets, by looking worlds with water in their atmospheres and, if we were really lucky, oxygen and methane, harbingers of life. Then, later on, I wound up serving in higher level NASA committee, the SSACC, advisory to the Associate Administrator, leader of the Science Directorate, and much later on the National Academy’s “Space Studies Board, where I was brought in direct contact with the astrobiologists. There were important, sometimes fruitful, sometimes frustrating discussions about the meager resources for astrobiology, especially work that was supposed to be carried out on the Space Station, but really wasn't adequately supported. I was really interested in what they were trying to do and worked to support them as vigorously as I could, so although I didn't really work the field, I was very glad to be associated with those scientists. In fact, one of the things I've liked most about my career is that, while I've not worked on planets and looking for planets and looking for life, and those kinds things, I've been right in contact with all the people who've been doing just that.

For decades, I did what I could in terms of programs and facilities to make sure these fantastic opportunities were realized, because I'm really interested in the whole story. I want to see all those things go forward, as much as, or maybe more, than my own science programs. So, that’s why the HST & Beyond Report emphasized that this whole idea that the motivation that really drives us. It's not just, oh, we're interested in the answers to these questions because we want to increase our own knowledge of the universe. Not just that. We want to know where we came from. It's an ancient human obsession, and we shouldn't be embarrassed about saying this is what's driving us. A lot of scientists are in fact embarrassed, although I think fewer of the next generation of astronomers. They don't want to give the impression that there's an emotional component to our science, a passion, or there's something we're looking for, otherwise we're not objective. To me that’s nonsense. We may want certain things to be discovered, or understood – that’s human, but it doesn’t bias the outcome of these programs. A good scientist knows that there’s no sense in that. You have to convince your colleagues of what you believe, but that takes evidence and reasoning and the truth is, well, the truth.

Zierler:

Or even a religious component, because so much of religion is based around those questions. 

Dressler:

My committee had met for about a year about what the possibilities were for new directions and facilities, we had some very good ideas, and then I went away and wrote the first draft of that report, and a long, many might say passionate introduction in particular. I tried to spin all this into a narrative about origins. It had- I don't know if you read some of those early things, but it had a very emotional component. Our first meeting after I had sent it around, I could tell there were a lot of misgivings. But my colleagues were good about it. They said, "Gee, not sure I could put my name on this." I said, "Well, why?" They said, "Well, you know, it just doesn't sound like a scientific report. There's all this stuff about human passions, and looking for origins, and even science fiction, and all those kinds of things woven into our case." I overcame that resistance before long, because these were very smart scientists and they were honest about what drove them to be scientists and what they dreamed of doing. I said, I think we have to be honest about it. Certainly not all eighteen committee members were happy about this, but in the end all but a few got to like the idea. It was inevitable that I would do such a thing, because I had written a book in 1984, Voyage to the Great Attractor, which has a very passionate last chapter about human beings and their relationship to the universe, and this idea that we are in fact at the center of the universe in a meaningful way, the anti-Copernican conclusion, because “we are understanding it” and not the other way around. Places like Earth, with its unimaginable complexity, are the centers of the universe.

I think that the Copernican revolution was a kind of a swindle in the sense that we got displaced, displaced, displaced, displaced from a central position in the cosmos that we thought we had. It became so ingrained that more than one of my colleagues actually said, "The last ignominy – when we found out we weren't even the most common matter in the universe." And I said, "Wait a minute. You've got it backwards. We're special. We're baryonic matter. We're in this place of enormous complexity that's very, very special." They had gotten so into this idea that we're not in the center of the galaxy, we're not in the center of the solar system, our galaxy is not in the center of the universe, blah, blah, blah," that when it came down to dark matter, people actually said that. "We're not even made of the most common material." That's how clueless they've become. Carl Sagan was a genius, and I revere him, but one his mantras was that “Human beings have got to get over this idea that they're special.” Nobody likes to hear that. It's not a good sales pitch in astronomy. We are a very vain species, that’s obvious. We may be the only species that’s capable of being vain, but you must admit we’ve turned it into an art form.

I’ve been talking to people on airplanes, at public lectures, in the coffee shop, for so many years, explaining what I do and what we’ve learned about the universe, and invariably they say, "It's so overwhelming. I just can't get my head around it. How do you keep from feeling insignificant?" Or worse, “it makes me feel insignificant.” Always the same thing. So, I began to use a new pitch: "You know, this is the great discovery, that Earth, in fact, is an incredibly special place in the universe. Only in places like this can great complexity develop – as life. As incomprehensibly immense as the universe is, there have to be countless places like this. But they’re still unimaginably rare – special! We're one of those outposts. This is how the universe knows itself, at places like this, through beings like us." That’s been a big hit. We are important. So, what we’ve got here, this incredibly special place, we mustn’t fuck it up! The HST & Beyond Report absorbed that idea as crucial to our work, us, human beings, carrying the torch.

As I said, when my director here read that last chapter of “Voyage,” he said, "You’ve made a big mistake: Nobody is going to trust your science again because you're showing that you're emotionally involved." I was kind of crushed, but I couldn't change how I felt, and that's the way I am. But he was wrong. I never considered that I wouldn't be just as objective and just as hard on myself about the science if I cared about it, felt passionately about what I do, because I believed in a certain nobility in our work. I knew I would never get a preferred result just because I wanted it, burying what I didn't like in the bottom drawer– not me. And I’m confident the vast majority of scientists are just like me, but they are just worried about even something saying what he did about them. So, I never considered this a conflict, being emotional and passionate about astronomy, and being objective about my work. We were really lucky. When that report went public, it hit right at the time when NASA and its Hubble Space Telescope were all over the front pages, and so our report was a big hit as well. Today, you most reports like HST & Beyond that incorporate the looking for origins them, including the idea of humanity’s quests to understand our place in the universe. It’s a staple and should have been a long time before. 

Zierler:

Alan, when did you get involved in thinking about starbursts at a higher redshift? 

Dressler:

That was a discovery, because I don't think we were looking for anything like that. Back in the mid-1970’s, Gus Oemler, and Harvey Butcher had been among the first astronomers to use the supersensitive new CCD detectors to look at distant clusters of galaxies – about four billion years back in time. They found significant fraction of blue galaxies in these clusters, compared to today when the fraction is small, about ten percent or less. Blue galaxies are almost always spiral galaxes, but starforming spirals and not common in today’s clusters. So, they said that while these earlier dense clusters of galaxies are full of old, dead galaxies, they also have a lot of blue galaxies, and these blue galaxies are likely be spirals. That’s a big change in the makeup of the universe in the last thirty percent of its lifetime, so people were skeptical. Because Jim Gunn and Jim Westphal led the team to build the first camera for the Hubble Space Telescope, they had privileged access to the best of these CCD detectors: for astronomy they had to be pretty special, with high efficiency and low noise. So, they had a pocketful of “spares” that they were going to use in a large new spectrograph for the 200-inch, a mockup of the Hubble camera but adapted for ground-based work.

Waiting for this big project to be finished, Gunn bought some off-the-shelf commercial lenses and other components and configured a small single-detector instrument to put at the prime focus (at the top) of the 200-inch telescope that would look at distant galaxies and quasars with greater sensitivity than had been done before. So, Jim and I set out to check whether those blue galaxies were in fact star-forming spiral galaxies, by taking the spectra of them, which hadn't been done, and looking for the emission lines from glowing gas around young stars that would indicate that they were in fact actively birthing stars, as spiral galaxies do. That was the study we were carrying out with the first multi-slit observations, and we gathered enough spectra to show that, yes, most were part of the cluster population, not ‘interlopers’ and there were quite a few star-forming galaxies, but they had unusual spectra compared to today's spirals. We had galaxies that had no ongoing star formation at that time but had had high rates of star formation recently, enough to make them blue. Our spectra showed that most of this blue light was coming billion-year old stars (A-stars) born in a burst of star formation that had ended, rather suddenly.

We published a paper and that those kind of galaxies, with a burst of star formation, are very rare today in clusters today, and even rare among most galaxies, which are not members of rich clusters Yet, these were apparently common about four billion years ago, not very long in cosmic terms. Why? It took a long time before astronomers thought much about what that meant. But now, it's part of the orthodoxy that, at earlier times, galaxies were still being assembled, bashing into each other, with lots of gas involved. They were much more volatile in terms of forming stars than they are today. It’s a feature of the younger universe that is part and parcel of building galaxies. This topic, star formation histories for galaxies, is now my main focus. We've got some results about younger galaxies, meaning galaxies that formed very late in the universe, what I call the cosmic autumn but my colleagues call ‘cosmic afternoon’ – I like the history of the universe in terms of a year, not a day. At this time, four to six billion years ago, galaxies were pretty much supposed to be finishing up their star formation, and by then a substantial fraction had ended altogether. But my colleagues, including Gus Oemler, Louis Abraham, and Mike Gladders, in particular, found about twenty percent of galaxies at that time had formed most of their stars within only one or two billion years earlier than when we were viewing them.

These are galaxies that are comparable in size and mass to the Milky Way, but with a very different history of star formation, we call them “late-bloomers” and the run counter to the paradigm that most of my colleagues rely on. We don't understand this result, indeed, many of my colleagues don’t even believe our result, but we are continuing to explore this, because it is very puzzling, from the point of view of physics: how could a Milky-Way’s mass of gas, raw material for making a galaxy, have hung around to form stars so comparatively late in the universe, when most galaxies had completed most, and sometimes all, of their star formation.

But now, with the James Webb, I'll be able to look at the first billion years, in particular, and observe galaxies beginning, assembly when the universe was very young. We’re talking about baby galaxies, maybe 60 percent or more of their mass in gas, not stars, full of fuel, in a way, ready for combustion, so to speak, and also being bashed by the profusion of baby galaxies surrounding them. At this time the universe must have been an extremely dynamic place. So, we’ll have the opportunity to see how they were forming in real time – as it happened. Only astronomers get to see history in the making, for real!

The universe is so young at that point that for even a single galaxy, you can look at the full history of its brief life, from a single observation. The colored light we will collect, the spectrum, contains not just the light from stars forming at that time, but over its brief but eventful half-billion-year life. So, you can say, "Oh, it had a burst here, and then it went dormant, then powered up again!" It’s something you can't do today- look at the full history of star formation in a galaxy, because looking back from recent times, stellar population older than a couple billion years all look alike, that is, you can’t distinguish a billion-year-old population from one seven billion-years-old, so no “history.” We've all dealt with this degeneracy for so many years, that it’s so strange to be in this position where we will actually be able to watch it all happening and get the earliest histories completely, even though it’s all in the remove past.

A lot of my colleagues are wondering, will we get any galaxies at a redshift of eleven, twelve, fifteen. That means back to the time when the universe was only 200 million years. It's going to be hard: they're going to be exceedingly faint. My colleagues think it's necessary to actually see them in order to see the actual birth of a galaxy. I haven't really been able to convince the team that a complementary approach, maybe a better one, is to look at older galaxies, for example, ages of 600 million years, and read in the history what they were doing when they were only 200 million years old. Like tree rings, in a way, checking the wet years and the dry years from the rings on a single tree, instead of looking for trees of all ages and counting The more conventional approach is to count galaxies at different epochs to construct a history, which is more following a whole population, rather than looking at individuals. I think that may be harder, and maybe less complete, and accurate.

This approach suits me. I've always based my science on observations of individual objects, try to see what their histories are, and use that to sort out what happened. The thing in astronomy these days is “big data” – comparing huge numbers of galaxies by properties. It's like if you wanted to study what people are like, and you went and measured big populations of millions of people, and wanted to know all about them: their weight, and height, etc. And then you had these graphs of all these common properties. Well, you'd know a lot about “people,” but you really wouldn't know much about “persons,” and how they vary from one another. Within the variation is all the interesting information. Another example, if you were to try to do a big survey about the health of people, you'd find, in general, most people are in good health. You wouldn't learn anything about the people who weren’t in good health, and why they aren’t. My work, with a couple of my colleagues here at Carnegie, over the last four or five years, has been to look for galaxy star forming histories that show not the overall trend of what the average galaxy is doing, but what's the dispersion in histories? More to the point, why is there a dispersion? And it's true in human populations, too. You'd like to know why some people shoot up to seven feet tall, and why some people never get over three feet. If you can’t answer that question, you are only describing the growth of human beings, but not really learning how or why.

Zierler:

Alan, I wonder if you could explain the Great Attractor Model and how it came about. 

Dressler:

I can try! This is not a simple story. Mostly, astronomers use the Hubble relation, that distance is proportion to recession speed, to map out in the universe. It's hard to get an actual distance to a galaxy, given how immensely far away everything is, but if you know that things are all arranged by distance because the universe is expanding, as Hubble had discovered, you can say, this galaxy is so many millions of light years away, or billions of light years away, because it's receding at a certain speed. That’s Hubble’s Law. But the universe is full of galaxies, so at a detailed level that breaks down, because if you have a lot of galaxies close to each other, they also have motions caused by mutual gravity. In fact, as the universe expands, the densest places don't expand at all, because gravity can be strong enough gravity to overcome the expansion. So, if you simply used Hubble’s Law in such a dense region, you'd actually mistake how far away many of the galaxies are, based only on their velocities.

Now, back in the early 1980’s I was working with a team studying elliptical galaxies, those round balls of stars, on the mistaken belief that these would be the simplest objects to understand how galaxies have grown over time (star formation), and how the stars are moving inside them (structure). This team had seven collaborators, and had assembled data for about 400 galaxies, at the time, a unprecedently big sample This was one of the first of those big groups, although, again, a very small group compared to today’s collaborations. We had access to telescopes all around the world, which we needed to carry out an all-sky survey, and to get the total brightness, brightness profile and spectra of, in great detail. This group was led and put together by Sandy Faber. We started making our observations, which took years.

At about the same time, another team, led by John Hurchra and Jeremy Mould, had been measuring redshifts (velocities), for many thousands of galaxies – also unprecedented. For many of the spiral galaxies in their sample, they also had measured how rapidly the spiral galaxy was rotating, data that could be used to determine the absolute brightness, and that means they could compare the absolute and observed brightness and determine a distance that could be compared to the distance you get with the Hubble relation. It’s basically saying: we measured the distance to a galaxy, found what it’s recession velocity should be for that distance, and compared that to what the measured velocity actually is, with the difference called the peculiar velocity – for about a hundred galaxies. Their team had had been working the Virgo Supercluster a vast volume of space that contains the Virgo cluster but also many rich galaxy groups. Within the Virgo Supercluster they were the first to see this effect of gravity perturbing the Hubble expansion flow: galaxies in the direction of Virgo were streaming toward it, actually a retardation of the universe’s expansion. We could see the pattern in their data – a triumph! So, the Virgo Supercluster was an attractor, gravity holding galaxies back, pulling them back in, as they tried to disperse with the universal expansion. Galaxies closer to the center, the Virgo cluster itself, were completely turned around and destined to join the Virgo cluster in time.

One thing that was particularly interesting about their result was its connection with our own Milky Way galaxy’s motion in space. From maps of the cosmic microwave background, sort of a universal reference frame that represents the whole universe, our galaxy has a clear motion- very substantial, about 600 kilometers, or 400 miles in a second! In a sense, this was a different way to measure peculiar velocity – for our Galaxy only. When first discovered, it seemed puzzling. How could we be moving so fast? We're not in a rich cluster, just out in the boonies. People said, "Well, Virgo over here is pulling us toward it too. That's not exactly the direction we’re moving, but part of it is."

So, here’s where our team of seven comes in. In order to measure how much pull our Galaxy is getting from an over-density (higher than the average density of galaxies in the universe) like the Virgo supercluster, you need to measure a distance to the galaxy independent of Hubble’s law, as had been done for spiral galaxies in Virgo. Our study of elliptical galaxies, quite by accident, found a new technique for measuring the distance in this independent way, so we could measure the peculiar velocity for all the elliptical galaxies in our sample, and look for a pattern of in-fall like the Virgo study had found. Several years into our project, when we plotted the peculiar velocities of all the galaxies in our sample, we found the same kind of pattern of in-fall that had been measured for the Virgo supercluster. There seemed to be a streaming in one general direction, which happened to be better aligned with the direction the Milky Way is moving with respect the microwave background. However, we were surprised, because there was no cataloged familiar supercluster in that direction, and no rich clusters either. At that point, Ofer Lahav, an astronomer at Cambridge and a friend of our team, used an extensive galaxy catalog and made a pseudo-picture by painting all the galaxies, at their brightness, on a hemisphere (half) map of the sky, in the direction of the streaming flow.

Lo and behold, there was a massive, very large glow of light from all these galaxies, sliced in half by the dusty plane of our Milky Way – one reason this supercluster had not been noticed. On the cover of Voyage to the Great Attractor is the picture Ofer made. Put the two things together, the huge cluster-less supercluster and the large-scale streaming of galaxies we found, and you have the Great Attractor – a name I blurted out, without thinking, at a press conference. So, it looks plausible that the combination of the flow towards the Virgo supercluster with the flow towards the Great Attractor explains the large peculiar motion of our own Galaxy. So, we published that. It was an exciting result, but not embraced with any enthusiasm, is how I’d kindly put it. The principal criticism came from the people who were working on the cold dark matter model. They said that such a giant swell – the overdensity we called Great Attractor, was too big a perturbation to grow from those fluctuations observed in the microwave background. But there was a catch: at that time, the cold-dark-matter practitioners were convinced that the dark matter was enough to close the universe, which means that the density of essentially all matter that would bring the universal expansion to a full stop – eventually. That reasoning had merit, even I bought the idea that Ω = 1, because if the value started out even a tiny bit larger or smaller than unity, the universe would have collapsed quickly, or expanded incredibly rapidly, forever, and either way was fatal for us being around to even argue it, if you know what I mean.

Of course, by this time, astronomers were developing different ways to actually measure the value of Ω -- the ratio of the measured matter density divided by the critical value – that the theorists were requiring to be 1.00000000… and the funny thing is that all such attempts showed that the matter density was maybe twenty-five percent of the critical value, nowhere near the Ω = 1. It’s interesting for me to look back on this controversy in terms of the history of such issues: it was hard to ignore that the Great Attractor was there and also hard to ignore that its ability to provide the missing component of our Galaxy’s motion. You could see this big swell of galaxies in the sky. You could measure that, within the errors, all galaxies in its direction are speeding toward it, but still, the theorists rejected it, the Virgo supercluster’s contribution- yeah, but not the Great Attractor, it’s just too big. In other words, it’s an amusing example of theoretical prejudice, however sensible, fighting observed facts, and guess what? their objections vanished only a few years later when theorists acknowledged that there was no evidence that there the density of matter in the universe was that high, quite the contrary. The Great Attractor was accepted, for a while, at least, and especially after it was discovered, in the late 1990s, that the universe is accelerating, and that “dark energy,” when added to the “dark matter” makes up the critical density physicists said the universe must have, Ω = 1 – how about that!

Of course, we still don't understand it, neither have we found the composition of dark matter or understood the physics of the dark matter. So, the whole controversy about the Great Attractor disappeared over time, and it seemed like nobody was interested in it anymore. It went from being impossible to being uninteresting in a few years. Oh yes, people said, there are Great Attractors all over the universe, the galaxy maps now showed, and this just happens to be closer than we might have expected. Sandy Faber and I continued to work the evidence for the Great Attractor in the 1990s. We made better measurements that confirmed the early work. However, only in the last ten years did I see that the Great Attractor was getting panned again. Large galaxy surveys have been made that have been used to measure the peculiar motion of tens of thousands of galaxies, many more, and much further away, that what we had been doing. What is available now is a much greater quantity of data that is of very low quality when compared to the task, and no surprise that some studies have concluded something that I think is ridiculous: that the peculiar motion of our galaxy arises on a huge scale, much bigger than the Great Attractor, which they see as a pimple. Ironically, this has the same “too big” problem that the Great Attractor once faced, but that seems to have been swept under the rug, or maybe just forgotten. What I find really annoying is that this new work seems to entertain the possibility that none of this is due to gravity, but this apparent motion of our Galaxy with respect to the universal frame is just baked in, representing some further “new physics” we don’t yet understand, or worse, one we can’t even articulate. So, I’ve gone back to working on the Great Attractor, using a much more accurate way to measure the peculiar motion, to prove that the center of the Great Attractor is not moving with respect to the microwave background. That will demonstrate conclusively that it is gravity that is at work, and peculiar motions, wherever we see them, are from gravity in the surrounding volume, as it must be, and not over some vast scale. I will publish this paper next year, and probably nobody will care because it's no longer surprising that the universe is full of Great Attractors, but it's my duty to defend the integrity of well-known physics in this era of crazy stuff our physics can’t explain – dark matter and dark energy.

Zierler:

I wonder if you could talk, in late 1980s, about the state of black hole research. Supermassive black holes, the ubiquity of massive black holes. What was going on? What were some of the exciting developments at this time?

Dressler:

Well, as I was saying, I had actually made a big step in this, which was prompted by remarkable evidence from Wal Sargent and Peter Young at Caltech, for a supermassive black hole in the center of giant elliptical galaxy, M87, at the center of the Virgo cluster we just talked about. M87 has a jet of glowing gas coming out from the center, also seen in radio and x-ray light, so astronomers considered it likely a dormant quasar, much like a dormant volcano. The amount of energy released in a quasar has to be in some way linked to a supermassive black hole, as Cambridge astrophysicist Donald Lynden-Bell had speculated in 1969, because no amount of star-power could release so much energy so fast, but the extreme release of gravitational energy associated with huge black hole could. So, Young and Sargent looked for evidence of that in most likely ‘nearby’ quasar-like object and, with spectra from the 200-inch Hale telescope, showed that, yeah, the speeds of the stars dancing around the center of M87 increased the closer you get to the center. They made a model that would explain this, including black hole with a billion times the mass of our Sun. Extraordinary, but surely the most likely explanation. People generally accepted it, but of course, it was an extraordinary result, and, by Carl Sagan’s excellent rule, extraordinary claims require extraordinary proof. And, in fact, you could actually model the increasing speeds of the stars without a supermassive black whole, fairly easily, by saying that the stars are not dashing in and out randomly, but that they anisotropic orbits: the further out stars would simply be on more circular orbits around the center, with stars closer in on thin, plunging orbits. Sargent and Young made the conservative assumption that all the stars were on isotropic orbits, so by invoking the very high standard, many astronomers consider this likely but not yet proven. (Measuring the anisotropy of the orbits of stars is done routinely nowadays, but it was beyond the state of the art back then.)

So, I decided I would try to look at two other active nuclei galaxies, those that had tremendous energy pouring out from their centers, presumably from supermassive black holes. Unlike M87, these were not dormant: each had an intense blue searchlight that screamed “massive black hole.” I went to the 200-inch, where a new CCD detector had been installed on Bev Oke’s ‘Double Spectrograph.’ My idea was to look at the spectrum in the near infrared, to see the starlight with and lessen the blast of blue light coming from their massive black holes, hoping to see the sign of stars moving faster and faster at their centers. Since there were no such observations focused on the stars in the centers of such galaxies, I needed to look at two galaxies that were not candidates for massive black holes, and what would be better than our nearest neighbor, Andromeda, and diminutive companion, the elliptical galaxy M32. I was carrying out another project with the 200-inch at the time, so I was waiting for a night with excellent seeing – the sharpness of the images, to get the best measurement of the stars moving at the very center. I got lucky, an excellent night came along and I pulled the charts out of my briefcase (yes, a briefcase), and I got the spectra along the major axis of the two active nuclei galaxies and our two neighbors. When I came back to reduce the data, I found that, for the two galaxies targeted to as having black holes, I failed, because there was still too much blue light coming from the glowing gas in the quasar, it overwhelmed the ordinary starlight. Very disappointing.

But to my utter amazement, there was a clear signature of stars going nuts-o in the centers of Andromeda and M32. In both the nearest major galaxies to us, massive black holes seemed to be hiding in their centers, and these were no quasars, at least not now. The data were stunning. In particular in Andromeda, the signature of a massive black hole was not only a rise in the swarming speed of the central stars, but also a rapid increase in their rotational speed around the center. And that was critically important, because it meant that isotropy, or the lack of it, was not an issue the way it could have been in the M87 case that Young and Sargent had studied. Seeing a very large rotation told us what the orbits were like – no ambiguity of how to calculate the mass required to speed things up. I reported these results in a paper that discussed how infrared spectra were extremely good for studying the collected motions of stars, with a rather modest coda that said the evidence for Andromeda and M32 was strongly suggestive of massive black holes in each, about fifty million times the mass of the Sun in Andromeda and ten million times in M32. A couple of years later, Doug Richstone, a theorist colleague of mine, and I wrote a paper that went much farther, arguing there was really is no way out of it- these galaxies had supermassive black holes, based on the circular orbits of the center of Andromeda. We concluded that the mass density there must be higher than any state of matter we knew for sure exists. I’m phrasing it that way because, after the paper came out, we heard from a number of theorists who said things like “what if it’s a giant ball of neutrons, pions, gravitons…who knows? These alternatives were more exotic than a supermassive black hole, so how could they use that to say we hadn’t demonstrated, beyond reasonable doubt, that a supermassive black hole inhabits our nearest neighbor?

I didn’t get it. In the end, this quite upset me, because I think our paper on M31 really was the final nail in the coffin, so to speak, that we had confirmed a supermassive black hole– full stop. But for some reason I don’t think we get the credit for that, and it wasn’t until a decade later when the black hole at the center of the Milky Way was confirmed beyond any doubt – they found individual stars with their orbits curving around the black hole in accordance with gravitation theory, that the field said “now we know for sure there are supermassive black holes.” I think that work is fantastic, it got a deserved Nobel prize but I really think people should have acknowledge that Richstone and I were the first to make a case that couldn’t be challenged in any sensible way– that’s usually good enough in scientific studies.

On the other hand, I do get some credit for being the first person to suggest that the mass of the black hole was in proportion to the mass of stars in a galaxy’s bulge (that big swell of starlight you see in more edge-on spirals) and not in proportion to the mass of the entire galaxy – the disk plus the bulge. I took those observations of black holes in Andromeda and M32, I accepted the Young and Sargent measure of a billion solar masses in M87, another measurement of a black hole in the Sombrero galaxy, and an upper limit on the mass of our own Milky Way’s black hole – undetected at the time, and I said, “If you ask whether the mass of the black hole is proportional to the mass of the galaxy, that’s clearly not right – a poor correlation”. But just consider the spheroid part of the galaxy – leave out any disk – and the black hole mass does scale with that. Even with four galaxies and an upper limit, that was quite clear. And I published that, in 1989. People thought that was nuts. How could I do that with just four points? And I said, I only looked at two possibilities, nothing else, the total mass of the galaxy and the mass in one of its two components. What else could it be correlated with? It's not like I looked around for everything I could correlate it with. There's a galaxy, it's this massive, it has two components, so I'll just talk about the one property it made sense to look at.

There’s a reason why I like to take credit for that too. It was an important result, that the mass of the black hole could in some way relate to structure hugely bigger, beyond any direct connection – that suggested the bulge of a galaxy and its black hole must form together, or under a common influence, and that was an essential clue to how a galaxies form. A year later Sandy Faber assembled a group to study that, the Nukers we called ourselves, based primarily on this one correlation, and by the time we completed that work, many years later (mostly with excellent data from the Hubble Space Telescope), this correlation that I had first seen was confirmed beyond any doubt (and the credit, to all intents and purposes, given to the team) But the mechanism, how does this correlation emerge as galaxies grow? And over what time in cosmic history was the relationship in place when the universe was only three billion years old remains an issue of great interest and study– hundreds of papers so far, so I’m proud of being the first person to make the connection, that was an exciting discovery.

Zierler:

Alan, I wonder, at what point, just to foreshadow to just a few years ago with the Event Horizon Telescope, at what point was the black hole research community thinking about the possibility of capturing a real image of a black hole? When did that start?

Dressler:

Oh, relatively recently, I think. I had heard of the project to put these radio telescopes around the world “together,” electronically speaking, but I didn't know about how well it was going, even though I knew vaguely that it had the capability to resolve the proper scale at the very center of a galaxy But what I was clued into, from back ten years back (when I was still working on NASA and National Academy committees tasked with new programs) was the idea that you could see the event horizon with an X-ray space telescope to see the effects of high energy radiation emitted at the event horizon of the black hole. That extreme resolution came from using X-rays and building a very long X-ray lens. I think it’s still on the NASA wish list, and it would be a great complement with what has been learned from the Event Horizon radio project.

Zierler:

So, to be clear, in the late 1980s, the very idea of seeing a black hole, observationally, this was outlandish. This was not on your radar at all. 

Dressler:

I don’t think it was. We were seeing strong evidence of a supermassive black holes through the motions of the stars and, in a way, an X-ray image or a radio image is no different – it’s evidence for a supermassive black hole, but it’s not the black hole itself. In the Event Horizon image, the black hole is what you don’t see, in the middle! The other thing we should remember is that even though evidence was definitive by the time we were working in 1990, there were still questions about why these supermassive black holes were not found in purely disk galaxies, although I wasn’t surprised by that. So, it came down to whether a theorist was willing to raise the bar of evidence high enough to exclude anything else that could be responsible, whether such a thing in nature exists or not. And many remained skeptical on that basis. So, it wasn't until those observations of the stars in the very center of our Milky Way that showed them whipping around, just as they should be, and requiring a ridiculously high density of something, that those physicists seem to give up the fight: "Okay, we give up. They really are black holes." So, I give some credit for their stubbornness. Extraordinary claims do require extraordinary proof, even if we didn’t all agree on what extraordinary proof was. However, and I think this is maybe what you’re driving at, the image from the Event Horizon radio imaging is not better evidence than what we doing in the 1990’s, and it is certainly not better than the Milky Way black hole evidence, in my opinion. If Event Horizon were all we had, many theorists would still be holding out for better proof, or at least they should be. Because, as I say, the Event Horizon image is just that, evidence for a black hole but not an image of a black hole, because by definition, you cannot see a black hole! So, in the early days nobody was saying, "If only we could image the field of a black hole, then we’ll know for sure, but that’s too difficult.” If someone was saying that, they were wrong.

Zierler:

So, the question then really is, it's not that you were surprised that black holes could be seen. It's just that you were surprised the way they turned out to be seen. 

Dressler:

Yeah, it’s just the technical achievement that I didn’t expect so soon. I mean, we knew what the size scale of the Event Horizon was, and you're talking micro-arcseconds, extremely fine resolution. You're talking about gigantic optical telescopes that we don't have, probably won’t unless we make big interferometric optical telescopes in space. Or the more exotic things X-ray telescope that could achieve that resolution but might not be very useful for any kind of work, and that might be too expensive for just one project. So, really, the way they did it, was very impressive. You have separate data, detection of radio light from a small region in the target galaxy, from many telescopes over the world. Usually, you would combine the beams in way that the time signatures and spatial parameters are well enough constrained that you achieve interference of the light and that allows you to make an image. We have such radio interferometers- that’s the most common type of radio telescope around the world. The great achievement with Event Horizon was combining the light from many telescopes a world away from each other, so to speak, in order to see the “fringes” of interference that made an image possible. Very impressive. I don't think the world had been waiting to see that, but these scientists believed that people would be a visceral connection with such an image. Good for them!

Zierler:

To return to an earlier thing we were talking about, about you not being afraid to convey emotion, and the bigger questions in science. On that day, with the Event Horizon, the image of the black hole, how did you feel? Did that have a visceral impact on you?

Dressler:

No, and maybe I’m not being clear enough here. I didn’t think, “Okay, now we’ve seen a black hole, and now I believe!” I already believed, and this was just more evidence, not something altogether different. I got that buzz from the Milky Way black hole data- if I had needed a clincher, that was it. Even this was not the charge I got from some other discoveries. For example, I was writing a letter recently to John Mather, the P.I. of the COBE microwave satellite made exquisite measurements of the cosmic microwave background. The theoretical prediction was that the spectrum would have the shape of a “blackbody,” a skewed bell-shaped curve that results from an amount of matter in equilibrium, absorbing as much electromagnetic energy as it is emitting, frequencies of light that scale with temperature. The prediction is extremely well understood and precise, and when I saw that this was the exact spectrum the COBE satellite had measured, my heart skipped a beat. I was at an American Astronomical Society meeting when Mather unveiled the results, standing with an overflow crowd attending his lecture. It was days of transparencies and overhead projectors. Mather slid that onto the projector, and it appeared on the screen. Perfect agreement, as least as perfect as you could measure. Error bars blown up 1,000 times so you could see them. The audience gasped. That really got me. That was physics. That was science. That was also another Nobel Prize.

Zierler:

You have to explain. Why? What's the big difference? 

Dressler:

If that fuzzy picture from the Event Horizon had looked a little different, the physics of matter at the horizon of the black hole might have needed tweaking. But there was no chance that black holes would be “ruled out” unless no ring with a dark hole was seen, and everyone knew it had to be there because we all acknowledged that these giant black holes are real. Nothing changed, it was a huge technical challenge to extend our sight in this new way. I think the results was foretold, if only they could overcome the challenge of making this world-size telescope. But the prediction of a blackbody was such straightforward, definite prediction about the universe, about the Big Bang, that it really had to be a black body, with no funny kinks or bends in the spectrum. And that was because this light was emitted at a time when the physics of the universe was comparatively simple, with none of the complicated physics of the modern universe with its zoo of interacting elementary particles and radiation fields, multiple energy sources– lots of variety. Compare this to 400,000 years after the Big Bang: the epoch when the cosmic microwave background emerged, electrons, protons, light, simple electromagnetics in an expanding, cooling plasma, was dead simple. There was no wiggling out of this if the spectrum departed substantially from the blackbody form. Our bets were all in for the Big Bang. A 3.2 degree Kelvin blackbody the only winning hand. I should add that it had been known since the 1960s, from ground-based experiments, that the temperature of the background radiation had to be approximately three degrees, that was what sunk the “steady-state” universe theory and crowned the Big Bang model as the winner. But COBE was the first opportunity to see the full wavelength spread of the spectrum and to make truly exquisite measurements.

A lot of physicists didn’t consider cosmology a real branch of physics when I was starting out. I remember that from the 1970s, but the COBE result changed most of their minds. They saw that the cosmological state of the universe is quantifiable; there had been decades of measuring the expansion rate, Hubble’s constant, that never led to an agreed-on value, but the precision of the CMB spectrum blew that skepticism away. And in the decades since, cosmology has been one of the most exciting fields of physics, and we’re learned of things we never even suspected and understood fundamental physics from the cosmos– experiments that couldn’t be done in laboratories, that are carried out by the universe for us. So, you see, those kind of things, for example, the discovery of the expansion and much later the acceleration of the universe, the CMB temperature and fluctuations from which all structure today emerged, inspire the soul of a physicist. Compared to discoveries like that, a picture of a massive black hole just doesn’t ring the bell. Not for me, anyway.

Zierler:

But it's interesting because from the world of observation, theorists will say, in general relativity, they knew that black holes existed. But I wonder if your approach to knowing they existed is really coming from a different perspective than a general relativist. 

Dressler:

I think you're right. It could very well be that. But on the other hand, compare the feeling of awe from astronomers when the first gravity waves were detected, recording merges of neutron stars and of black holes. Now that is of the same magnitude as seeing that black body curve. It's reassuring to astronomers when those giant leaps are made, because most of us don't work that close to physics very often. It's all in there, but we don't manipulate it every day. When you have something like the detection of gravity waves that is that dispositive, and you see those curves of the “ringing” from a merger of such exotic objects, it tells you, you really have learned things about the universe, and it reminds you that how amazing it is that human beings could work out such complicated physics, design an mind-bogglingly difficult experiment, take twenty years to build it, work ten more years to improve the sensitivity to where you might see something, and you do, and it confirms general relativity to the nth decimal place, well, you realize that we’re reading and decoding the universe at a level that is way beyond what we once thought was possible. And remember, the theorists predicted exactly what those “ring downs” would look like, and there they were.

Unfortunately, there's too much stuff in my line of work now that's not predictive. People make huge computer simulations of the universe, and they get things that look like galaxies, sitting in the halos of dark matter we have postulated. But the only thing they really model is the halos, and then to compare to galaxies, they need to play around with what the physical processes might be like to build a galaxy of stars on that halo: recipes, if there's a dark halo, then there's this much gas, and it combines like this, and the star formation occurs at this level, proportional to the gas to the second power, because blah, blah, blah. And they run this mish-mosh and they say, "Look, it kind of looks like a galaxy disk." But they knew what they were trying to match when they started. So, they’ve changed and tuned their code until they reproduce what looks like galaxies, and they're proud of the fact that the physics looks reasonable, plausible. But they didn't predict anything. Every time we tell inform these theorists about new properties of galaxies, or better measured parameters, they simply just diddle the code until they match it.

The dark matter halos themselves, that’s a different matter, they’ve predicted what the superstructure of the universe is and how galaxies are clustered, and they’ve turned out to be right. That’s a real theory because they postulated the existence of something and made predictions based on it. But when it comes to the properties of galaxies, they’ve done no such thing. Never have the N-body simulations predicted something about real galaxies that we didn’t already know. If you can't predict some phenomena that isn't known, you’re not really doing theory. Unlike the CMB spectrum, or the mergers of neutron stars, or the theory that massive black holes are the engines of quasars, these cold-dark-matter simulations have not predicted something that was unknown, that either did or didn't fit the prevailing model, and had to be thought about, because whatever the prevailing model was, either it wasn't compatible with that, or they hadn't actually checked to see if that was something that they thought should exist. Whew! Those kinds of tests are so powerful, and when you discover something that you didn’t know before you started, that validates what you're doing as scientist. 

Zierler:

Alan, the next thing I want to discuss, of course, is HST & Beyond, but I propose, we're coming up on the two-hour mark. How about we take a five-minute intermission, and come back refreshed? 

Dressler:

Sounds good. 

Zierler:

Okay, see you then. 

Dressler:

See you then. 

[BREAK]

Dressler:

I must say, you're making this very easy. 

Zierler:

Oh, good. Well, this is what I do for a living, so I'm happy to hear it. 

Dressler:

Yeah, you can keep your day job. As I was walking down the hall, I was thinking about this whole question about emotion in science. I think I'm an unusual person for a scientist, not unique by any means. But when my director said "Nobody will ever believe your science" after reading this…” I think he was saying he couldn't imagine trusting any scientist who admitted that how he felt about things he or she was working on. So, in a way, it was a judgment he was making about himself. But while it’s clear to me that many, perhaps most scientists appreciate things other than science, I seem to have an unusually strong connection with the arts, music, paintings, and drama in particular often evoke very strong reactions in me. I play piano, mostly it’s song writing, and it’s the emotional release that I love the most about it. art and science are both the same human activity: the brain striving to represent the world in human terms. But science has rules, and because it does, we can do good science even if we're passionate about the work and its outcome. But the other, with few rules, allows for an essentially limitless variety of emotional expression, it requires it. Most scientists prefer to look objective, regardless of what they feel about how their work is going. I trust myself to be objective even when things are not working out like I thought they would, like I hoped they would, and to a large extent that’s because being really wrong about something I’ve promoted in my science would be very painful. That keeps me on the straight and narrow; it’s probably why I’m so proud of my track record. I’ve not published anything that turned out to be wrong, or foolish, or wishful thinking.

Zierler:

Alan, we'll jump back in, first with some brief administrative history. The Association of Universities for Research and Astronomy, what are the origins of this group, and how far back does your association go with it?

Dressler:

A very interesting history. Up until the 1950s, observational astronomy was dominated by private ground-based optical observatories, Carnegie was a leader, so was Caltech, Texas, Harvard, Michigan, there were maybe a dozen major players. At this time, when the funding for science from the federal government was on the upswing, and lot of astronomers at other, mostly smaller universities, were fed up with their lack of access to these telescopes, and domination of the field by few institutions mostly funded by private sources or state funds. AURA, then, was founded on the urging of a relatively few important astronomers who represented this discontent. Astronomers were starting to have these decadal surveys then, the first in the 1960s, chaired by Lick astronomer Alfred Whitford and charged with reviewing the state of the field and suggesting the type and scope of new investments by the National Science Foundation. One thing that was very clear was the imperative of making resources available to more people. So, to form the Association for University Research in Astronomy, a number of universities chartered together, including some that had had observatories of their own. AURA was a management company, essentially, and they founded what became the National Optical Astronomical Observatories, NOAO.

I came to Carnegie at a time when the national effort was ascendant, it looked like the future of ground-based astronomy would be mostly lie in federal funding through NSF. But within ten years, the initiative shifted back to the privates,” for reasons that are not simple or clear. They led the building of a class of eight-m telescopes, Keck, MMT, Magellan, Hobbe-Eberle and the emphasis at NOAO shifted to providing comparable facilities to these, rather than leading the way. That is where my own involvement with AURA started. Even when I first came to Carnegie, I realized that a good system of “public and private” facilities was essential if the U.S. was to going to be competitive with the big investments in Europe and Japan. It was not common for astronomers who had privileged access to big telescopes to be very involved in the national effort, with the possible exception of the Decadal Surveys that the National Academies ran that focused on prioritized, federally funded new facilities. But I had worked a little with the Kitt Peak four-m telescope and had lots of friends at NOAO, so it seemed natural for me to involve myself, so in the mid-1980s I began to work very to bring things together, to downplay the competitive aspects of public versus privates and emphasize they complementary nature and the importance of advocating for both sides. For example, there was a NOAO-sponsored conference in Coeur d’Alene where the future of large telescopes to be built by NOAO were widely discussed. At that conference I suggested that the national observations, NOAO, should build two 8-m telescopes, one in in the northern hemisphere and one in the south, and drop their ambitious plan to build a gigantic telescope of four 8-m mirrors combined together. I thought this was too far beyond the state of the art and that it would weaken NOAO in its ability to serve the large community that depended on the national facilities. After Coeur d’Alene the emphasis shifted to a pair of 8-m telescopes at NOAO’s two sites, at Kitt Peak in Arizona and in the southern hemisphere near Cerro Tololo, Chile, the site of another four-m.

As I said, I was the first person at Carnegie to cultivate the public observatories side of the field, and because of my interest, I served on NSF committees and on the panel for ground-based optical astronomy of the 1990 ‘Bahcall’ Decadal Survey, where I and several colleagues argued for a closer, mutually supportive system of private and public facilities. Many colleagues made a point of appreciating that I was playing this role, especially since so many on the private side were hostile to, and some even vocal about it, the money going to the public facilities. I was reaching across the aisle, as it were.

The other ingredient that led to my leading HST & Beyond was AURA’s management role of the new Space Telescope Science Institute, STScI. In 1993, the community was struggling with the apparent failure of the Hubble Space Telescope, a potential disaster because so much of the hopes of the community were dependent on Hubble, a long sought-after facility with fantastic capabilities. Astronomers were really not responsible for the blunder, a perfect mirror polished to the wrong shape. Although Jim Gunn, my collaborator for many years, had written an open letter to the community that blamed the culture of astronomers for taking too little interest, and not properly supporting, the instrumentation side of the field. That was true, I thought, but the actual problem was that this was the most complicated machine ever built, with about 10,000 people involved, from maybe one hundred companies and institutions. There really was no management structure that had been perfected for bringing all the people and their work together, so the big error was directly traceable to a couple of people involving in making the mirror who did not follow the testing protocol and their manager, who failed to follow procedure that would have caught the mistake. Ironic, isn’t it, that the one of the most basic components of the telescope, the mirror, could contain so fatal a flaw and not be caught. Fortunately, it turned out to be just barely possible to change the cameras on Hubble, using the flawed mirror, and recover the extraordinary spatial resolution that the Hubble was capable of.

So, back to the story of HST & Beyond. It was far from certain that the Hubble could be fixed in the summer of 1993, and AURA was justifiably concerned that STScI’s role in forefront astronomy might fade in just a few years, with the Hubble handicapped, and there was nothing in the planning stage that could fill the void. The future of astronomy was very much in doubt, NASA, the butt of many jokes and cartoons about the failure was not committing to start a new project, especially one that would require a decade or two to build. They had many other areas of space science they needed to support and were not going to commit to starting on a replacement. What they were willing to do was to mount what they described as the most ambitious (and potentially dangerous) space mission to-date (including Apollo): the repair of optics and instruments in a way that had not been planned. They were not optimistic that such a mission would succeed but were willing to put enormous resources from that part of NASA to try. So, that was the situation, great uncertainty about the future of Hubble. This must have been very depressing for AURA, because I imagine they realized that Hubble in its present state would support the STScI for a few years, but not the ten or twenty years that had been anticipated.

AURA called me that summer and told me how NASA was going to try to repair the Hubble, but we were not to count on it, and so it was time for the community to face this and ask what was the plan for space astrophysics if the Hubble remained compromised. The AURA president, Goetz Oertel, speaking for the AURA Board, said “We'll help you form a committee of the best people to look at what the future might be.” He said that, while it may be very difficult to talk NASA into building another big telescope, if the Hubble can’t be fixed, we need to try to do just that, and we need to start the planning in the next year. After all Hubble took twenty years to build, so we'll have to start the work now. So, we selected very good group of astronomers and astrophysics, including technical experts and Ed Weiler, at that time the head of NASA’a Astrophysics Direcotrate, and, as I remember, we had our first meeting on the phone, spitballing, we might say, laying out the groundwork, for what we might talk about. Of course, one possibility was a replacement for the Hubble Space Telescope, but many on the committee felt it would have to be something new, not just a repeat of what failed. It might be important to be able to do many of the things that the Hubble would do, but it couldn't stop there. And we had to think more broadly about a program. In a way, this was all very one-off kind of planning. We had these decadal surveys, like and they would look at the landscape every ten years, but sometimes that was not often enough, like this time. And there was no plan being developed about what facilities the community would like to have on a longer timescale, twenty or thirty years down the road. That kind of future planning became common starting, I guess, in the late nineties, which was good.

So, with a some of the best people in the field, we had very wide-ranging discussions at first. We considered many things, including constellations of smaller telescopes and new technologies to build very much bigger telescopes like the Hubble, which, for all intents and purposes, was like a ground-based telescope shot into space. Now people were thinking about taking advantage of the weightless environment, new materials, new detectors, new electronics. After all, designs Hubble were two decades old, so there were new possibilities. And there was the question of what wavelengths of the electromagnetic spectrum would be best covered for a replacement, or follow-up, of the Hubble. All of those issues and possibilities came into our deliberations and were reflected in our recommendations.

Hanging over this was the depressing possibility that the Hubble could not be fixed and perform as well, or at least within shouting distance of its design capabilities. Where we got incredibly lucky was that NASA was able to fix the Hubble, in a daring, spectacular mission in December of 1993. So, before we were well into our process, we knew that we didn’t have to replace the Hubble, but could think more broadly about the future, particularly optical to infrared space telescopes. In fact, we were even luckier than that, because the impact of taking high resolution images from space, free from the blurring effects of Earth’s atmosphere, was hugely underestimated. When the first images started to be released in January 1994, it was like looking at galaxies, star clusters, and the places stars are born, for the first time. Also, it didn’t hurt that all these images were in technicolor, Hubble’s cameras took pictures in different wavebands which were combined to show the universe in color. We had that capability on ground-based telescopes, but it was difficult, expensive, and it didn’t really impact the science, but just like with movies and television, the move from black and white to color was stunning. So, rather suddenly, as I recall, NASA was releasing beautiful color pictures from space of all kinds of astronomical subjects and they were exciting and captivating in a way that had not been expected. It seemed like every day the newspapers, from the front pages of newspapers, New York Times among them, and magazines like Life and National Geographic, and were parading these pictures, and the public was paying attention to NASA in a way that hadn’t happened since the Apollo landings on the Moon. It wasn’t just the public that responded with wild enthusiasm; I think scientists were just as enthralled by what we saw. I want to add something here about those pictures that I think is a great lesson for astronomers. Yes, the Hubble pictures were stunning, but you could find a hundred artists with computer-generated graphics that could make even more crazy, dreamlike pictures. But something I don’t think we realized until Hubble, people grasped that these were real places in the universe, places we were now visiting that we had never known existed, in a manner of speaking, and no human-made imaginary image, no matter how startlingly beautiful it was, could hold a candle to what people saw as REAL.

So, boy, this changed everything for the HST and Beyond Committee. Before the repair mission NASA had little or no enthusiasm for more space telescopes, we got the message, but after the public reaction to the beautiful pictures NASA realized how important this was to their future, I think, and they changed their tune but fast. With our committee we had the opportunity to catch the wave, as I liked to call it, to exploit Hubble’s new journey to the universe in living color and think about how we could go even further in the future. By the end of 1994, the first full year of our work, NASA was already looking to us to see what we would come up with. I think everyone on the Committee agreed: build on this excitement. Show how it's part of something bigger. With the example of Hubble, imagine what you could do with the whole space-astrophysics program. What we needed was a bigger theme, and we came up with one: Origins, where did we come from? Are we alone? about as big a theme as you can get your head around, if you could do that. However, this is where many on the committee got worried that we were getting too involved in non-science issues, emotional ones, things that were also the concern of religious beliefs, for example. Some on the committee didn’t agree that this was a motivation in why they did research, instead they voiced the to understand nature motive. I accepted that, but I also felt that many who were concerned really did consider our origins as a fundamental reason to do astronomy, even if they had been reluctant to voice that in any professional setting, like for example, in a report like the one we were working on, traditionally, a rather dry, deliberate document whose excitement was limited to “expanding human knowledge.” As the year went on, I felt more of the committee members warming to the idea.

So, over that next year, our discussions began to pare down from a dozen or so initiatives to just a few, with Origins – our origins, not the origin of the universe, as the central them. First in line was the Hubble Space Telescope, our model for a great origins mission. Here was an instrument that delivered us a view of the universe when it was only one billion years old, and infancy compared to today’s fourteen-billion-year age. This was the epoch of the birth and early building of galaxies, of the first generations of stars, and this was a critical step in why we are here. Tune the physics of the universe a little differently and there would have been no galaxies, no stars, no heavy elements made inside those stars, no complexity, the hallmark of our universe and life. It could have just expanded forever into a diffuse sea of hydrogen and some helium, cooling, glowing ever more faintly, a sad and lifeless conclusion to the greatest event ever. Hubble was going to help us unravel, lay out, understand, this key moment of the universe. There was so much to do, that could be done much further back in cosmic history than we had expected to see with the Hubble. So, when we learned that NASA was committed to run the telescope only to 2005, less than ten years, we made our first recommendation as extend the life of the Hubble to 2010 or beyond.

Of course, there was an argument to build an even larger telescope, one that could see even further into the past to when galaxies were more like one hundred million years old. But to do that, we knew we needed a telescope capable of sensitive infrared observations, because the light from so long ago was redshifted by the universe’s expansion. And to do that the telescope had to be much colder, cryogenic, than Hubble, which was essentially at room temperature because of its proximity to the Earth. On the committee was Harley Thronson, an astronomer who focused on IR observations and had been part of an earlier proposal to build an infrared telescope somewhat bigger than Hubble, and running very, very cold. A telescope that size, with sensitivity in the near infrared, would likely get us to this true “birth epoch” for galaxies. And it was something that absolutely had to be space, since the Earth is warm, and any telescope built on its surface will be blinded by its own infrared light. Not only the birth of galaxies, but other things we wanted to do but couldn’t: the infrared lets you peer through the dust in the cradles of star formation to see what’s going on, and there were applications to what we called “active nuclei” galaxies, those like quasars that have supermassive black holes. Harley’s telescope had been proposed but not accepted in the NASA competitive process, but there were very good studies of the possibilities. It soon became apparent an infrared-sensitive telescope, only modestly bigger than Hubble, would be 1000 times more sensitive for IR observations. A huge, game-changing capability that would let us complete the investigation of light coming from a wide range of astrophysical sources, places in the universe that were all connected in some way with how we got here– origins. As time went on, this next generation infrared telescope became our second, and our principal, recommendation.

Connected to that, but something rather different that NASA had been hoping to build: the capability to observe planets around other stars. The problem here was that the parent stars would be a billion times brighter than a planet like Earth circling it. Infrared observations, in particular, would possibly allow us to suppress the star’s light so that you could see its family of planets. The method that looked most promising at that time was interferometry, where you make one telescope out of several, and they can be widely separated to that you get the resolution of a gigantic telescope by connecting, with beams of light, many smaller ones. Just like we were talking about earlier with the imaging with the black hole with radio telescopes. Radio astronomy had perfected this connection of telescopes, relying on the interference of light gather from each, and the way to do this looked at the time to be with several infrared telescopes working together as an interferometer. The plan that was being developed was called the Terrestrial Planet Finder, because everybody thought finding a planet like Earth would be on target to the question of how we got here and how common is life. And the key was to separate the small planets by “blanking out” the central star via interferometry. However, the technical challenges were great, this was well beyond state of the art. Of course, it played perfectly into our Origins them- search for life in our own Galaxy, directly by finding other planets like Earth. If we could take spectra of those planets we could learn if they have water on their surfaces, like Earth– and oxygen/methane in their atmospheres, most likely that would have been generated by life on the planet. Jackpot!

So now we had three recommendations. I discovered that I really liked to have three and would follow that all my future committee work where recommendations were the goal. There’s a symmetry, and you can build a program with three legs that stand together and are complementary. (Recommend two things and only one of them gets built. More than three, and maybe nothing gets built.) In the case of HST & Beyond: (one) continue to operate Hubble for a longer time – all that was required was a (substantial) support level already in the budget, (two) a somewhat bigger telescope that nevertheless offered huge advances by being an infrared, cryogenic telescope – a big new investment was needed, and (three) development of technology for a terrestrial-planet-finder interferometric space telescope.

Zierler:

Alan, in terms of the planning that went into it, from the beginning of your chairmanship of the committee, was the idea always to produce the document that advocated ultraviolet optical infrared for space astronomy, or was that a process that developed over time?

Dressler:

It wasn’t that focused, by choice. Especially with the uncertainty of Hubble repair, we all thought it was important to cast the net wide, you don’t often get a chance to do that. But I think that Hubble’s success narrowed our focus considerably. I don’t mean that we couldn’t have chosen something else, for example, go full bore on the search for and study of planets around other stars. Another thing that had been talked about, particularly in the context of the Hubble issues, was the “all the eggs in one basket” approach. Some of my colleagues were strong proponents of developing some sort of standard platform that could be used for a generation of space telescopes, for example, one for the ultraviolet, one for the visible, and two for the broad IR regions. I think that, if the Hubble repair had been unsatisfactory, this could have been a major recommendation of HST & Beyond: to develop a telescope prototype that would be adaptable to different programs according to the specific capabilities required for a broad or narrow science goals. Then we might have discussed some of the science priorities as we saw them and left it up to the next Decadal Survey to rank the proposals and choose the first application of this approach. Yeah, it was wide open.

There were people who believed in building interferometric telescopes on Earth and in space, and they had a variety of programs they wanted to do with it. I think we discussed a lot of things. It's hard for me to remember what the next most important thing was that we discarded. Several of us thought that a scaled-up Hubble, with the same capabilities but a larger mirror, would be our choice if the repair didn’t go well. There had been a study previous, before the Hubble was even launched, a ten-meter telescope that much more ambitious, but one thing that had going for that idea was that it would be an advanced technology replacement. To first order, Hubble looks like an Earthbound telescope that got launched. It’s big and heavy, the kind of mirror that is stiff because it can support its own weight – even though destined for a weightless environment. So, there were lots of possibilities when we started out. That earlier proposal, for a the “next generation space telescope” (NGST, a name we borrowed for our big recommendation) didn’t have a chance of real investment, in my opinion, because the Hubble hadn’t even been launched when they completed their study. In comparison, our NGST, what became the James Webb Space Telescope, was going to utilize state-of-the-art technology. We knew it was going to be a lightweight structure, possibly it would need to be deployed from a folded position for launch, would need sophisticated mechanical and electrical components to function in a cryogenic environment we knew that telescope was going to be deployable, and have all kinds of engineering improvements for constructing big structures.

As it turned out, that was arguably the greatest hurdles in building the Webb telescope, that it needed a deployable tennis-court-sized sunshade, made of five fragile layers, to keep the telescope at a temperature of forty-deg Kelvin – what you needed for great infrared sensitivity. (The mirror for the Webb was finished maybe six or seven years before the sunshade, the latter was that difficult.) So, we knew that the new technology would need to be explored and adapted before the nature of NGST would become clear, so we tried not to be too presumptuous about the requirements, of which the most important was the aperture size, the diameter of the mirror. Late in our deliberations NASA told us they were looking for something in the half-billion-dollar neighborhood (this was just for construction, not including development, launch, operation…) and fortunately there had been a recent study by the Ballistic Missile Defense Organization for building a four-m aperture spy satellite telescope for which they had made a cost estimate, so based on that, we recommended that the telescope be four-m or larger, and if turned out that more advanced structures would allow building a more gossamer-like thing that could be much bigger- great. That would make it much easier to accomplish our goal of seeing the births of galaxies. But we put out the report with that rather unspecific specifications for NGST, but NASA seemed happy to grab the ball and run with it, even before the official version of HST & Beyond was printed, I believe.

Zierler:

When you say NASA, who were the key people in NASA who were excited about what you were reporting?

Dressler:

Dan Goldin was the NASA Administrator – the longest serving head of NASA, appointed by President George H. W. Bush and carrying on through Bill Clinton and George W. Bush. He’s very important to the story of the James Webb Space Telescope. Working for Goldin was Wes Huntress, the Associate Administrator for Space Science. Space science was divided into four science directorates, focusing on the Sun, the Earth, solar-system planets, and astrophysics, and Huntress also ran an extensive engineering effort to support these directorates. Ed Weiler served under Huntress as Director of the Astrophysics directorate. Weiler actually served on the HST & Beyond committee, ex officio, as required, but extremely valuable in terms of the perspective that NASA had, or might have, of what we could propose.

The HST & Beyond Report was favorably looked on, certainly by AURA, who chartered it, and by the astrophysics community. So, when I say NASA grabbed it and ran, I think of April of 1995, when Hubble was doing fantastic work and even more amazing results were coming: the stunning, earth-shaking Hubble Deep Field picture would appear in less than a year. The momentum for NGST just built and built. And I believe that part of the reason HST & Beyond caught on was that it was something new for these reports to see a big idea- origins, holding things together. Not just hardware, and not just the science of doing this and that, but something bigger. Here were astronomers showing the passion they had for their work, something very human that appealed to the general public. And, foregoing modesty, I heard from many of my colleagues that the writing of the report was inspiring, or even poetic. At least for those people, having a sense of exploration and a journey to answer humanity’s oldest questions was a welcomed addition to the kind of reports we had been writing. I noticed that soon reports in the other areas of space science moved in that direction as well. I don’t think anyone is embarrassed nowadays about writing about a sense of purpose in what we’re doing.

And, NASA needed something like HST & Beyond. Since the Apollo program, they tried a lot of things, Skylab, the Space Shuttle, building the Space Station, the Mars landings, all great, but nothing had gotten the public engagement they got going to the Moon. It was clear that Hubble was doing just that. They were in the mood to accelerate the astrophysics program after Hubble’s celebrity status was apparent. NASA bought onto HST & Beyond’s recommendation to extend the life of the Hubble right away, that was a no brainer. (It’s interesting, isn’t it, that we were hoping to extend the life until 2010, and today Hubble is still delivering great science, more than a decade after that.) That's another good thing about having several proposals in a report. You want to have one thing that you know is a slam dunk. By that time, we knew NASA would extend the operational life of the Hubble, but it hadn’t been announced. One for us! Our recommendations are getting done. And then, like I said, they started to think about the engineering of this next telescope. NASA was already exploring IR interferometry as a technique for finding planets, but that was going to be difficult and development had not really moved very far. But I should add, there was at the same time a sort of embarrassment that these initiatives were happening between decadal studies, going contrary to the history that no big astronomy programs, in space or on the ground, proceed until blessed by the whole community. This Decadal Survey process, carried out by the National Academy of Sciences, is something that astronomers did first, and we're very proud of it because very few fields have managed to come to consensus about what should come next.

Physics is a field that has famously failed at it, and for some areas, like biology, it’s hard to imagine how to bring such an enormous, diverse field together and to agree on anything. But the federal government likes Decadal Surveys because members of Congress are very often lobbied by scientists from their states to promote new laboratories, facilities, and projects. For the most part, the members don't really have the expertise to judge which things to build and which not. Scientific pork may make sense if there is a strong benefit the state and its citizens, but they are grateful to have a clear idea of what scientists from across the country have agreed are the field’s priorities. They point to the list and ask the proposers, is your project on this list? If not, goodbye! Over the last decade the other NASA science directorates have followed in astronomy’s path by writing their own decadal reports. There's even been talk about doing something similar in other sciences, branches of physics doing it, but the challenges are often considerable, with Federal laboratories and large Universities primarily promoting their own interests.

You can see that making the HST & Beyond recommendations mid-decade, and having NASA begin to act on them, put us and them in an embarrassing position. So, it was agreed that the work would be preparatory, and nothing substantial would be built- no cutting metal or even any major hardware started until the whole community had a chance to weigh in with the next Decadal. The process would begin in 1998, so it wasn't all that far off.

But I’ve skipped over one very important moment in my career, when I was called to personally present the recommendations of HST & Beyond to Dan Goldin, NASA administrator in mid-1995. It was really his blessing that was missing. Wes Huntress and Ed Weiler came to me together and explained "We’re on-board, but you've got to go sell this to Dan Goldin. He’s infatuated with the Mars rock and wants to put everything into finding life on Mars." Do you remember the rock with the fossils from Mars? 

Zierler:

Sure. 

Dressler:

It was potentially a monumental discovery. Rocks collected in Antarctica, which had been knocked off the surface of Mars millions of years ago and orbited around before running into the Earth, were being scrutinized, and one in particular, Allan Hills 84001, seemed to show the fossilized remains of some worm-like creatures. If that were true, then a huge step in the Origins program may have already been taken. Of course, if Mars and Earth are exchanging rocks, this makes it impossible to be certain this life on Mars started independently of life on Earth. But still Bill Clinton got on television and announced what was, potentially, the most exciting discovery ever in the search for life beyond Earth. So, naturally NASA Administrator Goldin wanted to put a whole lot of resources into the Mars program, who could blame him? And he was the boss. So, compared to that, what chance did the building a new telescope to look at distant galaxies have? Huntress and Wiler said, "Alan, you've got to convince him that this is as exciting as the Mars thing. It’s not going to be easy."

So, they were going to shove me through the door, and they did, and I made a very simple argument. I brought a big picture of the Andromeda galaxy, coffee-table-book size, and I brought a picture from the Hubble, with a few spiral galaxies, much smaller than Andromeda. I laid these in front of Goldin, put my finger on one of the smaller spirals and said, “When we look out into space, we look back in time.” Then I laid my finger on one of the small spirals and said, “these galaxies are a billion years younger than Andromeda, our closest neighbor.” Then I moved my finger to a small group of galaxies that were barely visible, "These galaxies are like young children. They will grow up to be like this galaxy (I pointed at Andromeda), or our Milky Way, and we humans are here because they did." I paused three beats and continued, “We want NASA to build a big cryogenic space telescope so that we can see galaxies when they were born, as babies.” At that point Goldin looked pleased, maybe even excited, and he asked a couple of questions. It was a very short pitch, the whole thing was over in a few minutes. I was walked out, while Huntress and Weiler stayed behind with Goldin and his science advisor, France Cordova. Perhaps five minutes later, they came out and said, "Wow, terrific. He's in. He bought it." That was all it took. You have to know how to do these things. I didn’t talk numbers, or redshifts, just pictures and plain English. That’s where the passion comes in, to do this, you actually have to feel that way.

Goldin as an enthusiastic supporter of NGST was great, but he was a very impulsive person and what happened later, at the 1996 American Astronomical Society annual meeting in San Antonio, nearly put the program on a path to certain failure. Goldin chose that meeting to formally announce that NASA was going to begin a design study of NGST. There had been a dinner with Goldin and local organizers and important astronomers before his address, and I had been invited and was marched into the auditorium as part of his entourage. It was packed. I was seated in the front row, and Goldin is maybe ten feet over me on the dais, and soon after he makes the announcement, he looks down at me and says "This telescope is exciting, but Alan Dressler, you've made a mistake, it's much too small. My people can build an eight-meter telescope at the same cost." People were shocked in the room, and no more than me. He did it in almost a mocking way, I was embarrassed but that wasn’t the problem. The problem was he set the bar way too high, basically calling for something that couldn't be done. The cost of a telescopes usually scales the square of the aperture, or more, so it should be at least four times more expensive to build an eight-m than a four-m. So, it's hard to imagine how you build it for the same price. Goldin was famous for this kind of stunt: he was the prophet of “better, faster, cheaper,” something left over from his days in aerospace. NASA engineers knew this was crazy, “better faster, cheaper” they said: choose two! Of course, there was the possibility of breaking the cost curve, meaning use technological advances to keep the price below four or five times as much, but not for the same money. But that’s what he wanted and that’s where we started, on a road that was headed into a ditch.

A year or so later Goldin told me over dinner that he felt it was important to challenge his engineers. But unfortunately, it led to a whole effort in that direction, trying to build a many billion-dollar telescope for one or two billion. Of course, his people knew this from the get-go, but NASA never wanted to admit to Congress how much it was really going to cost, because they didn’t think Congress would go for it. So, for more than ten years the budget grew and grew, It had a twenty-year life of “near death,” because even after they scaled it back to a six-meter it couldn’t be built for what was allocated by Congress, which of course was what NASA requested. It was a fantasy budget. The worst moment was in 2013, when the telescope was supposed to be a few years from launch, but it became public knowledge that they didn’t have nearly enough in the budget, and a blue-ribbon commission who analyzed the project blew the lid off it, calling for billions more and a launch date of 2018, still five years off. And, of course, even that didn’t hold, it looks like JWST will launch in late 2021 but a total life-cost (including nineteen years of operation) of about ten billion dollars. The negative consequences on many other space science programs at NASA was substantial. I remember the last time I pleaded to scale back to the design HST & Beyond had advised, a single four-m mirror, a telescope that didn’t have to be folded like origami to fit into a rocket faring. It was just me and Ed Wilder. I’ll never forget what he said, “Alan, I’d rather build the first in new generation of telescopes than the last in the old generation.” I had to admit, that would be better, it would open up the future. I agreed.

Zierler:

Alan, on that point, in the mid-1990s, of course, the way I understand it, the Clinton Administration viewed what it was going to fund in physics broadly conceived almost in binary terms. Was it going to be space, or was it going to be high energy? So, in the post-SSC era, it seems that that question was pretty decisively answered in favor of NASA. But I'm curious, from your perspective, if you felt that there was more budgetary flexibility as a result of the SSC decision? Was that something that was felt from your vantage point at all?

Dressler:

On the contrary, the SSC was the reason we lived in fear that JWST would be cancelled. It had happened there, and similar amounts of money was involved, and it was clear to us that the big sin that project had committed was not having a good idea what the SSC would cost and going back to Congress with new numbers every year. Also, we thought that, had it been finished, the SSC was probably a ten-billion-dollar project. And here we were following the same road. The fact that the SSC was cancelled was a precedent that almost killed the NGST too, because the cost of it was going up and up, and a lot of people were saying just like the SSC. I not sure I was even aware of what you say about the Clinton administration’s plan. Probably naive of me, but I thought both physics and NASA were very well-positioned at that time. High energy physics at Fermilab was a worldwide leader, and I was sure the U.S. wanted to continue to dominate the world in that subject. And certainly, by that point that NGST was going forward, it was clear that we were world leaders in space astronomy, too, partly because of the worldwide attention the Hubble had gathered.

So, both those things, it seemed to me, would be well supported, and I think Congress was expected to do so. But clearly, there were limits to what they were willing to invest. It may be that the Executive Branch had that strategy, but I don't think NASA felt under threat. For one thing, they thought of themselves as having this stable, growing budget, and their track record for at least finishing things and having them succeed brilliantly was excellent. So, for them, I think, the budget was going to continue, and, within reason, they could do whatever they wanted. NASA at that point was not interested putting all their eggs into human space exploration. And I don’t think the physics community felt threatened either. Funding for the national labs, Livermore, Fermilab, Argon, was very stable, too. I never heard anything remotely like NASA and DOE were in a competition. In fact, we thought we were mutually supportive. So, it's very interesting to hear that. But it's interesting that in both cases, the failure to be realistic about what things were going to cost, in one case it did wreck the SSC, and in the case of JWST, it nearly did, too. I mean, to tell the truth, I don't know how we kept the thing alive. 

Zierler:

Now, your involvement in the NASA Origins program, did this flow very naturally from HST & Beyond?

Dressler:

Yeah, absolutely. Basically, Origins is all over the report. I tried to make this point that missions that these missions solar systems and planets and those other missions that were about the birth of galaxies, the sort of alpha and omega of why we're here. Everything in the middle, that was chemistry, the formation of the elements in stars, cradles of star-forming regions, and things. Some of that was well done from the ground, but as Hubble matured, it made a huge contribution to that subject too.

But to me, galaxies and planets there were the two things that you needed to do in space that bookended the challenge of understanding human origins. I always liked to emphasize that it wasn't the origin of life, or the origin of the universe, but it was human origins that we were talking about. Because that's the nature of our species. We want to know where we came from. That eventually got me into trouble, too, because for a while, there was a sort of clean division. They formed an Origins Subcommittee, and they put Hubble and a couple other missions in the portfolio. And there were missions that were focused on understanding exotic physics, for example, black holes, but nothing that really had to do with us. So, that wasn’t part of origins, but the purview of the Beyond Einstein Subcommittee, all the amazing, exotic things that the universe has to teach us about physics that we can learn about nowhere else. But eventually there were missions straddling Origins and Beyond Einstein and NASA got more and more uncomfortable with the ambiguity. To me, it was mysterious why they needed the division to be so sharp, artificial, really- seemed like a bureaucratic reason, something about budget lines I was told. So, unfortunately, they stopped using this idea of human origins and started just calling everything origins, and that now included the origins of the universe, which of course meant it covered everything, and so it now meant nothing. But we had nice run of about five years when I led the Origins Subcommittee, and we produced beautiful booklets and brochures. The decadal survey did happen, and already, they we were realizing that NGST was going to cost too much, much more than they had told OMB and Congress. But what could we do? The Decadal Survey got the cost estimates form NASA, nobody else. A lot of the blame was shifted to the Decadal Surveys, but really they were just trusting NASA to be accurate and candid about the costs. Eventually this led to a bit change in the Decadal process of how we estimated the cost of things, with an independent entity reviewing NASA’s budgets. So, as it evolved, JWST continue to cause lots of problems. I think it's amazing that this thing is going to be launched, and by God, I hope it works. It will be such a catastrophe if- If it fails it would be really a twenty-year heartbreak. But if it succeeds, and I think it will, it’s going to be absolutely fantastic, just like the Hubble was.

Zierler:

Yeah. So, Alan, on that point, given that it's twenty years, how would you measure some of the goals at the time relative to where we are now? Is this a timeframe that, looking back, you're not surprised by? Is this moving slower than you anticipated? 

Dressler:

No, actually, I think it's just about what we said. The knowledge of the universe up to what the Hubble has done is quite extensive now. And we’re much better prepared, from the point of observations, theory, and analysis, then we would have been if JWST was launched in 2013. So, the time hasn’t gone to waste. But neither has the work we anticipated been carried out from some other advances in either ideas or hardware. We know now, better than ever, that the first half billion years holds the secrets to how galaxies emerged, how generations of stars that changed the chemistry of the universe were born. And to reach that last frontier, you need both a gigantic telescope on the surface of the Earth, or an infrared telescope in space. Since those two things have yet to materialize, this last ten years, in particular, has been planning to use JWST, and trying to make even bigger ground-based telescopes a reality. Astronomers have been talking about building gigantic ground-based telescopes -- something in the neighborhood of thirty-m of aperture, a gain in light gathering power of an order of magnitude since the 2000 McKee-Taylor Decadal Survey, I had served on a panel for ground-based optical-infrared facilities in the 1990 Bahcall Decadal Survey, and this time I was put in charge that panel, and I’m sure my work on HST & Beyond got me that opportunity. You might think I would have wanted, or expected to chair the space astronomy panel, but remember we were hoping this 2000 Decadal to bless the course we had charted, and to do that fairly it had to be somebody completely uninvolved with that planning. The Survey chose Steve Beckwidth, then the STScI Director. I should explain that running one of these panels was not the same thing as serving on the main committee that did the final prioritization, but the missions and facilities they prioritized were chosen by these topical panels who had selected them out of (typically) dozens of initiatives that the community had forwarded.

Perhaps, then, it’s not surprising that my co-chair Todd Boroson and I raised the issue of a huge next-generation ground-based telescope at the first meeting of that panel. We hadn’t received such a proposal, and Todd and I thought it was essential that it be one of the things considered. Fortunately, one member of the panel was Jerry Nelson, the creator of the Keck ten-m telescopes, and he and a major player in Keck, Chuck Steidel from Caltech, were easily persuaded to return to the powers-that-be and to consider the idea. By the time of our second meeting, planning for CELT – California Extremely Large Telescope had begun. That's where we came up with the big telescope on the ground, for similar reasons. You needed a really big telescope to study galaxies in their earliest times, and for studying ‘extra-solar’ planets, those around other stars. Most everybody thought JWST and a giant ground-based telescope would be feasible by 2010. But twenty years later none of it has been actually realized. Only the European consortium, ESO, is in full construction of their giant telescope, a forty-m destined for Chile. The U.S. effort has spawned two projects: CELT became TMT, Thirty-Meter-Telescope, and U. of Arizona, makers of giant 8-m mirrors, and Carnegie started a program now called Giant Magellan Telescope, which has an effective aperture of twenty-five-m. Both of these are well advanced technically, one might say, ready to go, but the money, from private, public, and foreign sources, has been unable to reach the about $two B required for each facility. The 2020 Decadal Survey is reviewing this issue and, if support is strong enough, federal money would be sought, we hope for both projects, with the imprimatur of ‘first-ranked’ by the Decadal.

So, it’s all taken a lot longer than we thought, we are better prepared in terms of knowing what questions we want to answer about the birth of galaxies, and now also what generates such remarkable diversity of planets around other stars, which JWST and these giant ground-base telescopes will begin to tell us. Looking back, I’d say our planning has been good, our goals have been the right one, but the projects we chose have been more difficult to build that we imagined. In hindsight, maybe smaller bites would have been better, but I don’t think the time required to make these big steps has been at all wasted – we haven’t been sitting on our duffs for ten years!

Zierler:

Broad question: at the turn of the century, early 2000s, even into the 2010s, what were some of the major debates about ground base telescope versus space base telescopes in terms of the most important work to be doing at the time?

Dressler:

There were debates about just that, and some strong advocates on both sides. Steve Beckwidth was rather obnoxious arguing his belief that no more ground-telescopes should be built. And he had some more reasonable allies who thought that was the future, so why wait? From my point of view, they both have their place. The reasons are quite simple. There are two: First, ground-based telescopes have had much bigger mirrors for the same investment, and light is so often the limiting factor in our research – things on the frontier are usually very faint. Second, ground-based telescopes remain accessible, which means you can update the instrumentation over their lifetimes, usually about fifty-years.

As time has gone on, these factors have been more blurred. Hubble received many new instruments in its career, courtesy of extremely expensive and perhaps even dangerous Space Shuttle missions. And, as they have grown in aperture, ground-based telescopes are not ‘way more bang-for-the-buck,’ as I mentioned, JWST has a cost lifetime cost of about ten-billion dollar, but these ground-based super-telescopes are reaching billions-of-dollars too. There has been a clear advantage for space telescopes in terms of spatial resolution, Earth’s atmosphere really blurs the images of distant galaxies, for example, and Hubble has taught us that fine spatial resolution opens up investigations to include a much better understanding of the physics. However, we are perfecting “adaptive optics” that correct for the blurring of Earth’s atmosphere, over small fields, and this makes them more comparable to space telescope capabilities. After all this back-and-forth, perhaps it makes sense that both ground- and space-based telescopes will be needed for at least the next twenty years.

Zierler:

For you personally, the kinds of questions that were most compelling to you, what particular telescope, space-based, or land-based, were you most interested in seeing to fruition?

Dressler:

I wound up concentrating on the ground-based facilities that Carnegie runs at Cerro Las Campanas, our observatory in Chile. Only in the last five years has my work begun to focus on JWST. For several reasons, it became hard for me to get observing time on the Hubble after 2010. Most of the time was going to big collaborative groups, you can understand that, with such an expensive facility, you want to include as many astronomers as possible. And also my programs seem out of the mainstream, like my resuming the study the Great Attractor. I was unhappy about not being able to use the Hubble in that project, but that is really not that surprising given my position at Carnegie, where I have been encouraged to explore what interests me, not what is fashionable. This was central to Andrew Carnegie’s vision, even though public funding didn’t exist in his time, that there would be subtle pressures from all kinds of institutions to work on certain kinds of programs, he wanted to support some scientists, in a number of fields, to follow their own star, so to speak.

So I mostly turned my attention to Magellan, the pair of six-meter telescopes Carnegie, U. of Arizona, Harvard, U. of Michigan, and MIT had built and were operating. I had built a multi-object spectrograph for the Hale 200-inch prime focus in the 1990s, and at least one of these telescopes needed such an instrument. I had always thought of myself as a person who likes to build things, even though that has not dominated my career. In 1998 I turned my attention to leading a team of ten engineers in building a gigantic multi-object spectrograph for Magellan-Baade, one of the two telescopes, and that became nearly a full-time work for me until its commissioning in 2004. I was still doing some projects with other astronomers who had access to the Hubble, which kept my hat in the ring, but mainly I directed my future research to using this instrument– IMACS, Inamori-Magellan Areal Camera and Spectrograph, following the Carnegie model using instruments others had built, or building one myself, when I needed some new or special capability to do the science. For a six-million-dollar project like IMACS there is a huge amount of work, a lot of it stressful, but there is great satisfaction when it works, and it works well. IMACS has been the most-used instrument in the Magellan family, for all its seventeen years. That means lots of science has been done on it by many others, science that I never thought of or expected, but science that is great. And that is so satisfying.

Zierler:

Alan, on that point, in so many ways that collaboration is a two-way street, with the discovery of the accelerating universe, do you see any of the work that you're involved with during these years as relevant to that, and vice versa, in what ways did the discovery influence some of the work you and your colleagues were doing?

Dressler:

Well, I did work on the large-scale structure of the universe in the 1980s and nineties, but cosmology is really a separate field from what I was doing. Charting the expansion of the universe, with precision, has a direct link to fundamental physics, really physics that may understand in now other way. But this kind of precision has only been possible in the last two decades, and the Hubble has been one of the prime reasons. Wendy Freedman, one of the leaders in this field, was Director of the Observatories for ten years, and she assembled a group that used the Hubble and our Las Campanas facilities to first measure the expansion rate of the universe to unprecedented accuracy, and then to advance the discovery, by two other teams, of the acceleration of the universe. This result in particular has challenged our understanding of fundamental physics, and though we still don’t understand it, there doesn’t seem to be any way that this isn’t historically important work. Because of all the work done on this project at Carnegie, a tremendous amount, I was shoulder to shoulder with that for a long time, and the fact that I'm not on the team hasn’t kept me from following it very closely. That's fine. That's part of the good thing about being at Carnegie. You feel part of an effort that isn't just a bunch of people working on the same project, but the whole idea of the astronomical enterprise. The other side of cosmological research centers on precision measurements of the microwave background, which, of course, completely dovetailed into this whole question of the universe is flat, and dark energy reignited all that. And now, there's actually a controversy about the simple expansion rate based on a disagreement between the supernova and cosmic microwave background results. Well, with all that as background, the answer to your question is, perhaps sadly, none of these great cosmological questions and results has really affect my work, which has increasingly been about star formation histories of galaxies.

By the time galaxies get to the ages where I study them, cosmological matters have little effect, by then, cosmology is old news or maybe its young news. The stuff that was set in motion at the cosmological scale is long gone. It's not even easy to see how a different cosmology would have led to very different kinds of galaxy. And, even if it does, it's still very speculative and mysterious So, it hasn’t really affected my research. But when you're working on a part of the puzzle, you don't necessarily worry about everybody else getting their pieces of the puzzle sorted out? You're happy to be part of that enterprise that those issues are being worked out. Since I've been fully engaged in the community that was working on those things, dark matter, and models of the universe, and computers, and so on, and since it's all been going on around me, I guess I've always felt part of it. Succeeding in the things I'm doing would not be very satisfying if it wasn't immersed in this grand picture of how we got here, and how the universe became like this. How did it start from being smooth to this riotous, complicated structure? It's really a profound question.

One has the feeling, being at Carnegie, where the very first observations in 1924 that showed we live in a galaxy, a universe with billions of others, and then in 1929, when Edwin Hubble’s observations, combined with others, were used to show that this universe is expanding, I think of that as the birth of cosmology right here. When we've had to write up about our activities here, we sort of sum up our mission as understanding the universe of galaxies. And it's sort of a century-long endeavor. It's been a century now, and I think, in some ways, I believe in twenty or thirty years it will be all settled. Then, Carnegie astronomers will probably focus on other things, probably planets around other stars, how they form, how they evolve, is there life on them? So, there's a sense of identify here- I think most people are not fortunate to be in a place that has that kind of identity, and you feel a part of the whole history and its mission. Universities have to staff more broadly in order to teach, to educate graduate students for many different careers: X-ray astronomers, radio astronomers, particle physicists. The university environment is great, if you're interested in all those subjects, and I am. I would have enjoyed being immersed in that, and I try to keep up. But in a sense of a coherent goal in your life, and for your place, it's not the same thing. Not the same thing. 

Zierler:

Alan, how did you get involved in the EOS Decadal Survey? 

Dressler:

Let's see. Well, I think, short answer is, people decided I'm good on committees. I’d done a good job with HST & Beyond and the Ground-based Optical-IR panel of the 2000 Decadal. Then, of course, I had by the 2010 Blandford Survey, I had spent more time working with NASA and space missions. I was part of study teams that were trying to develop the space telescopes that could detect planets around other stars. Terrestrial Planet Finder was the name of one of the concepts. So, maybe it was obvious that I should try my luck with the space panel. I was hoping to be on the main committee of the 2010 Decadal, but that committee is hard to staff, because there are so many scientific interests and diversity issues that have to be attended to, and I'm just an old white male. But I think people did recognize that I was very capable in terms of gathering people together, laying out how we would come to some sort of consensus: what were the boundaries of what we were trying to think about? How were we to figure out, together, what we should do? I do think I have a special talent for that, as a chair, listening to my panel members, pulling out the threads, repeating them, getting people to interact, figuring out who was skeptical and trying to find out why they're skeptical. I like that and I like getting to consensus. It’s never unanimous with smart people, but consensus is good enough.

So, I had been very successful in the HST & Beyond, and I have been very successful in that 2000 ‘ground-based’ committee. You remember about the three recommendations rule: two of the three things we recommended are now the main attractions: the gigantic telescopes, and the LSST (Large Synoptic Survey Telescope), a time-recording survey of a large fraction of the sky, repeated again and again– this is now renamed the Rubin telescope, in honor of Carnegie (DTM) astronomer Vera Rubin. (The third thing was a program to support instrumentation on the ‘private’ ground-based telescopes, in return for observing time on them for everybody. It was a big success, and it did a lot of good, but a short-sighted Astronomy Division director at NSF canned it when his budget got tight – pound for pound, I think it was the best thing they were doing.) Our recommendations to the 2000 Decadal Survey were adopted in their program, and they all have come to pass (or are coming to pass). In recognition, again, I was given the chair of the space panel, limited to space telescopes involving light (there are plans for gravity telescopes).

That panel was especially challenging because there was basically no money for this next decade, thanks to JWST. So, I thought we came up with a good solution for that, too, and that was having a telescope like Hubble, but with this enormous field that would do all kinds of things that we needed. We were looking for something low cost, comparatively speaking, and magically, a Hubble-sized telescope built for spy purposes, a cancelled program, was sitting around gathering dust (in the clean room, of course). This and our other recommendations were, again, accepted as priority goals. But when that came out, people said, "Oh, that's not very interesting," or a number of other gripes. But it weathered that, it's funded and going forward, and now, everybody seems to think it's a great idea after all. It is now called the Nancy Roman telescope, in honor of NASA’s first Chief Astronomer. I've been successful with work for the community. There's no doubt about it. The missions my panels have recommended, chosen from many contenders, and in the last case, created by combining three proposals, what’s happening in U.S. ground-based and NASA astronomy.

Ironically, perhaps, I haven't really had that same effect here, at my institution. I haven't been given many leadership roles, except building IMACS spectrograph, and chairing the Science Advisory Committees for the Magellan and Giant Magellan telescopes, I was the one who brought what became the Magellan project to Carnegie and promoted it strenuously. Unfortunately, that required abandoning another project, with much rancor, unfortunately. Although I was the prime mover in this, I have been essentially written out of the history. I had hoped I might be Director of the Carnegie Observatories one day, but that never seemed in the cards. So, I can’t point to a big leadership role at Carnegie like I can in the broader astronomy community. I regret that, but it led me to a different place, not just a Carnegie astronomer with privileged access to great facilities, but somebody who worked for the whole community and cared about access to good facilities for everybody. I had no particular motive to use many of these facilities myself, but I really love astronomy, pretty much every part of astronomy, and so it feels really great to have put my hands into the works and to have helped guide the field. 

Zierler:

Alan, we already talked about some of the work you've done since you went emeritus, but just to close the narrative loop, I wonder, in the few years before you went emeritus, particularly, if you could explain this amazing distinction between the late bloomers and the old souls. What does that mean, and what are the larger questions that these distinctions relate to?

Dressler:

A good question, thank you. I mentioned that there's been a long-standing problem in astronomy of recounting the history of galaxies, which amounts to the births of generations of stars and amalgamation with other galaxies. Stars in galaxies are born in clusters, and there are always lots of these clusters forming over time- over a long time, for most galaxies. Whenever and wherever they form, the process is very similar: there are a few really massive stars, lots more of moderate mass stars like our Sun, and inevitably many, many more small stars. It's a statistical process, like throwing the dice, but on average these stars of different masses are always made in the same proportions. It seems to be independent of the environment in the galaxy, independent of how old the universe was at that time, pretty much independent of everything we’ve looked at. So, if you look at a galaxy, you could tell what stars are being born right then, easily, because there will be so many very young, massive stars that are easy to see, but you know that the less massive stars are there to, in the same proportions as always. (We call that a universal mass function.)

But what about the stars born millions of years ago, how many of those are there, in other words, what was the rate of star formation at the earlier time? Because it’s easy to see measure the rate of star formation recently, and that means back about two billion years, but it is essentially impossible to tell the older stars apart, that is, how many are three billion years old, how many are five billion years of, seven, nine, etc. The history you can measure is limited to “this many stars in the last billion years” and “a total of this many stars formed sometime between three billion and ten billion years ago,” but I can’t tell you exactly when. This is why, when I started in this field, we knew practically nothing about how galaxies began. For example, most astronomers thought that the Milky Way had a big burst of star formation long ago, in the first few billion years after birth, and then formed stars more slowly and steadily declining to today. Others thought the rate of star formation had been just about constant over its whole history. We just couldn’t know, when we looked at galaxies around us, what most of their histories of star formation were like. But we at Carnegie had an insight. I was working with Dan Kelson, and Louie Abraham, formerly my student, and we had carried out, using the IMACS spectrograph, a of hundreds to thousands of galaxies. We had taken spectra of all these galaxies from the period of a few billion years ago, all the way back to a few billion years after the Big Bang- that is most of cosmic history. And like most people, we could say, "Oh, we can tell you what the average rate of star formation was in all these galaxies way back when." We could map out this overall pattern, for all galaxies mixed together. Sort of like getting a report from every country about what the population growth has been over the last half century. You can get that report, and you can compare it, and you could say, "Oh, this country grew, immigration, probably." No detail, just averages.

What we realized was that, when we were looking at a galaxy as it was five billion years ago, we could from that point determine its star formation rate two billion years back, and then we would be stuck with an average before that, just like before. But now we had a measure of star formation for galaxies over a time that we couldn’t measure starting from galaxies today. Because we're getting closer and closer to the beginning of galaxies, that two billion years is getting to be a pretty big fraction of their lifetimes, as opposed to a galaxy today when the two billion years is only a small fraction of its history. So, we were looking for those kinds of things, and we were observing galaxies four billion years back in time. Specifically, for the sample we chose, about 10,000 galaxies, we could measure the star formation rate over the period of four billion years ago to six billion years ago – that last figure is when the universe was half of its present age, very far back. So, we get greater leverage on the early histories of star formation when you start further back to begin with.

Well, what we found that surprised the hell out of us. We found lots of galaxies, not most, but not rare– about one out of every five galaxies, in which most of the stars in that galaxy were formed in the previous two billion years. We don’t see any galaxies like that in today’s universe. But back then they were apparently common. One out of about every five. So, to repeat the main point, we could measure what fraction of stars formed in the previous two billion years and get a pretty accurate history over that period, and, while we couldn’t get a history for all the stars that were older than two billion years, they amounted to less than fifty percent of the total mass of the galaxy. That was very surprising, because astronomers in this field had this picture that the overall pattern is that some galaxies form all their stars early, and most form only some of their stars early, but after a few billion years more, they have at least half of their mass and are just winding down after that. What we found were lots of galaxies that hadn’t done much when the universe was half its present age, but then they really got to work. That’s why we call them late bloomers. And this kind of galaxy was common three billion years ago and earlier, but basically disappeared before our time. Now, it was hard to convince people because we didn’t have full history, nobody could but we were said we were certain that, in total, there weren’t enough old stars in these galaxies to follow the paradigm history where pretty much everything starts early. In that view, no galaxy waits around billions of years and then gets going!

How many stars were born in the last two billion years was uncontroversial, but that old population that wasn’t there was not generally believed. The late bloomers rested on whether we were missing old stars, maybe they were there, we just hadn’t detected them using our spectra. We had to take this seriously, the late bloomer result was so unanticipated. We didn’t want to be wrong– that’s something all good scientists feel strongly, not just for what it does to your own career, but the consequences for other studies if their misled by your work. It took more than a year to convince ourselves that we weren’t wrong. Dan, in particular, spent a full difficult year producing mock galaxies that we could run through the program, because if we could find a way put in a lot of old stars, but the analysis programs didn’t recover them (for example, could they be hidden by dust?), then our result could be unreliable, and we’d have to withdraw it. But we couldn’t falsify our result. We discovered that we couldn’t say for any galaxy in particular that we were certain it was a late bloomer, but in a group of one hundred galaxies, say, we could be sure that about twenty of them were late bloomers, out of forty we could point to, but we couldn’t be sure which twenty they were. A probabilistic result like this is not unusual, and we may be able to overcome it and point with certainty to late bloomers in the future, but one thing we’re sure of is that this is a large population of galaxies of a kind we didn’t know existed. a couple years trying to devise tests to see whether we could prove ourselves wrong.

What it really says to me is that the way of looking for the average properties of a large sample of galaxies, without knowing what the variance is, washes out any interesting type like late bloomers. Just look at the average height of humans with age. A histogram or a curve that shows the age distribution of all people. If that’s all you ever do, you would never find that there was a person born maybe ten years ago, who stayed baby-sized for many years and then sort of shot up. We know that doesn't happen with human beings because we do study individuals, not just averages, but that kind of growth history does seem to happen for galaxies. The puzzle is, we don't understand what could have held it up the growth process that most galaxies go through, because there was a dark matter halo – the needed substructure, and there was the raw material, gas, but somehow the process didn’t take off. Maybe the halo wasn't fully assembled? We're not sure. But what could delay things? The universe is dominated by gravity, and that’s what causes stars to form. But our result looks very solid, and generally when you find something like that and you can’t explain, that's good – that’s going to teach you something, in this case, something very basic about galaxy formation, I think.

The community of theorists is very slow to respond to this. I get the impression now that many admit these things are real. Their computer simulations don't produce them, but that’s not surprising because those simulations were based on matching the things we know about, so adjustments were made to the physics on a scale we simply can’t model, and those “adjustments” don’t produce late bloomers. And so far they haven't found a simple way to say, "Oh, if I do this and this and this, I can make galaxies that didn't really get going until the universe was half its age." It’s disappointing to me that few seem to be trying. I kind of hoped everybody would say, "Oh, this is a challenge to cold dark matter. That’s great, I’m certain we'll learn something." So far, that hasn’t happened. They’re all engaged in a spectacular dance contest, and no one wants the music to stop. In some ways, it’s not a great way to wrap up one's career, but it's always good to discover something that isn't known. Like I said, I’ve been very fortunate in that respect. 

Zierler:

That's right. Alan, for the last part of our talk, I'd like to ask a few broadly retrospective questions about your career, and then we'll look forward to the future at the end. The first question I'd like to ask is, of course, your career coincides with massive gains in computational power. I wonder how the growth of computational power, perhaps even A.I. or machine learning, has affected observational astronomy. What are some of the exciting developments that may not have been feasible earlier in your career, and where are things today? 

Dressler:

Well, I'm singularly unqualified to make that judgment, as it happens, because I have only brief experience, in the late-bloomer study, with large samples of galaxies. Since my career started out with relatively small numbers of things and tried to understand what makes them different, in a way, and also to find out what really makes them the same, what's the variation and why is there any variation at all? There was never a time in my career where I needed tens of thousands of subjects for these studies. In fact, I'm generally not a believer that any phenomena in the field of galaxy birth and growth require that, because there isn't that kind of variation in the formation of galaxies. I seem to be almost alone in that opinion, and the quest to gather the common galaxy properties for millions of galaxies continues and grows. The justifications are very weak, and the programs are of the nature of “let’s get all the data we can” (which now means a lot) “and then we can be ready to answer any question we may come up with later– there have got to be such questions, right?” I just don’t buy that. If you can’t justify the need for the sample size, and you haven’t run into a problem you can’t solve because you have too few galaxies, they what’s the reason for that large investment.

For some things there are good reasons to get millions of galaxies on the sky, to look at the structure, to make maps, to look for sensitive correlations that bear on the physics of cosmology, but when it comes to studying individual galaxies and how they grow, I don't think those studies have contributed, at least, not because they are big. I almost feel the same way about the simulations which try to simulate millions of galaxies, because they put in things to get the right answer on the average, and that's as far as it goes. Now, I could see that big data has had a tremendous effect on other fields, but not the ones that I've chosen to work on. Since I spent many of my early years studying the morphology of galaxies in connection with their histories, I was recently invited to a conference about machine learning and teaching computers to recognize different kinds of galaxies. Wouldn't I give an introductory talk? I said, "Well, you know, I know very little about machine learning, and I haven't done this morphology stuff for a long time." They said, "Oh, you'll be perfect." I wrote back and said, "I don't want to be the old guy who used to do it by hand, one by one, and now he’s being replaced by a supercomputer! I may believe in what you're doing, and I believe that it's replaced people like me, but actually, I'm kind of glad that I had the ability to do it by eye, and to do it fairly."

It's funny, I participated in a discussion, another Zoom webinar kind of thing, releasing a book by World Scientific, The Origin and Evolution of the Universe that all of us had coauthored. I wrote the “Evolution of Galaxies” chapter and gave my summary of the chapter for the audience. Martin Rees, who is a very famous astrophysicist in Cambridge, was asked to join in because they thought it would draw more people into the webinar. After I gave my presentation, which as very much pitched in the “what are galaxies as individuals, like we’ve been talking about?” the host asked, "Would you like to add anything, Martin?" And Martin did. He basically slashed through everything I had said, and meant: "Well, Alan has failed to measure the big data, big science that has revolutionized this field.” I didn't get the opportunity to respond, "All the things I've told you do not rely on big data or massive computing power." Now, you have to understand, the computers I used when I started were primitive by today’s standards, and I use really great computers now that I do things that I need and do them in very reasonable run-times. But they're not supercomputers, and they're not being used to do absolutely impossible tasks. I just have to be honest about that. It’s possible that Rees’s attitude and approach will be the direction for everybody in the future, but I'm afraid of that, because I the boundary conditions of those kind of projects almost cut through (and off) the kind of work I want to do. This study with the late bloomers was an interesting interception. In that case I did have a very big sample – we could have made this discovery with less than 1000 galaxies, maybe less than one hundred, the bigger sample was helpful, but in no way did it affect whether I believed the result or tell us anything more about the phenomenon. So, I understand why capabilities like that have enabled new things, about cosmology and structure of the universe, for example, but I have yet to see anything new in the study of galaxies, how they formed, how they’ve grown to today, that are a direct result of really large samples– big data.

Like I said, when you talk about life, you talk about the tremendous complexity and tremendous variation in the universe, huge samples and supercomputers are essential for many aspects of the task. But in my subject, there are only like four or five different morphology types. There are histories that are, broadly speaking, three or four histories. This is not in any way complexity. And the other things we attach to those basic properties are specific physics that we learn about exclusively by looking into space. And that, too, is not great complexity, but a clear understanding of fundamental forces of nature. So, for me, my career was perfectly timed. I was the right kind of person who fell into the right job. I liked doing things in small groups. I liked thinking hard about the problem instead of a lot of setting up to do things and busywork. I liked planning what measurements I needed and figuring out how I was going to make then. The preferred approach now seems to pick things that are known but could be more finely described and understood, and getting an enormous data sample, before you ever try to do anything, and beating to death those already known phenomena. You've decided that you need this huge sample and it'll take five years, ten years, lots of money, enormous resources of telescope time, and computer time, and then we're going to do X, X, X, and X, without every justifying why we might need such a vast sample to improve modestly (but enough) on what we already know. My career preceded that, and I was very fortunate that it did. Temperamentally, that wasn't me. 

Zierler:

Alan, an institutional question- it's a counterfactual one because I’ll ask you to imagine other possible career paths not pursued. If you look at all of the science you've been able to do, all of the collaboration you've been a part of, what has been possible because of your affiliation with Carnegie as opposed to if you went the professorial work, and you were doing what you were doing at a place like Chicago or Caltech, or alternatively, if you were working from the inside at a place like NASA or the NSF? What have you been able to accomplish, and what were you not able to accomplish, specifically with a career spent at Carnegie? 

Dressler:

I would say the thing that I've not been able to accomplish is to train students. I did have two good outcomes: one was a post-doc who came here. I think I really affected his career, and the other, the guy Louis Abramson, who worked on this late bloomer project, I think I broadened his astronomy education too. Both of them helped me, and that was wonderful, fulfilling, and productive– wonderful. Of course, my professor friends tell me that for every good student, they have two or three where they put in more than they get out from the students, so that's a mixed blessing. But I know I missed opportunities to be advisor graduate students, and I know I missed teaching, because I like to talk and I like to share, it’s one of my life’s pleasures. So, I missed that.

When it comes to the science opportunities and the other professional things I've done, I can't really think of any place that would have offered me more. I would have been exposed to more exotic, cutting edge science by frequent interaction with physicists. Maybe I would have gotten more interested in the cosmological aspects, for example, instead of focusing on this star/ galaxy pre-occupation at Carnegie. That worked for me, and I think I would have found other things that I would have liked very much that I didn't do here. Although, we are a lot broader than we used to be. We’re expanding into planet research in a big way, for example. So, you asked me, what did I miss by that? Broadly speaking, I missed the teaching, in groups and one-on one. I think that would have helped me. It would have been enjoyable, mostly, and I think it would have opened me up to other things. What I missed most was the mentoring graduate students as they carried out their PhD theses. And I missed something of the intellectual life of being on a campus- that’s certainly the case. I would have gone to a lot of seminars in all kinds of subjects, not just science. But I think the bargain was a good one for me, because I've been very productive, and like I said, the Petri dish I fell into was just the right one. I had no idea, it was not what I imagined for myself, almost serendipity. Most of the people who come here as postdoctoral fellows or as experienced astronomers find it is the place they want to be, but not everybody, some really do want to be at a university, for various reasons, and they leave. 

Zierler:

Alan, a really broad question on discovery and ongoing mystery: because you've been involved in so much fundamental understanding in observational astronomy over the course of your career, what were some of the biggest question marks, dating all the way back to your time as a graduate student, that are now really understand, and for which you have intellectual satisfaction that we really understand these things now? And what are question marks that, perhaps, remain more or less what they were, and in fact, might even be more of a mystery as a result of all of the things that we know we don't know now? 

Dressler:

Well, of the things that I've worked on in particular, this whole idea of actually how galaxies got started, we knew next to nothing when I was in graduate school it was just hand waving, and you could have made almost any model about- oh, most galaxies formed most of their stars in the first few billion years, and the ones that are still forming stars are more or less coasting. That’s about it. What you could extract from determining the ages of the most massive star clusters in our Milky Way galaxy and a handful of others. To see what we have accomplished in the last thirty years is astonishing. In fact, the very idea that we could look back time and see what galaxies were like all the way through, back to almost to their births, which came from new detectors on the largest telescopes, and the Hubble, that’s a Golden Age of discovery. I think I contributed to that, partly from the science I did, and partly because I played a role in getting JWST started, and in building and instrumenting Magellan. JWST will put a big exclamation point on this.

At the same time, I've seen other things that astronomers thought they we believed we understood, for example, the chemical evolution of galaxies, to be revealed to be richer than imagined. In this case remarkable progress has come through traditional ground- based telescopes, and we’ve learned how to follow the buildup of the elements in different epochs and environments, so that this gives us an independent story of how galaxies have grown. And the complexity of it is a subject of awe. A great example of this is the recent confirmation, with gravity waves detected from mergers of neutron stars, of a theory that said that the heaviest elements, including all the gold on the Earth (and everywhere), comes from these (literally) fantastic events, spread out over cosmic time. Another example is understanding the details, from difficult theory, of how supernova explosions produce so much, and so many of the more common heavy elements, that’s just about as fundamental as you can get, if you want to know where we came from.

We’re still learning about those things and have a-ways to go. And, of course, our knowledge of the planets around other stars has gone from zero to amazing, and we’re just at beginning of an explosive growth of this elemental part of the story of the universe, and life. I still believe that finding a water world like Earth would be like a dream achievement, and I really hope that happens in my lifetime, but I have to admit, I'm drawn to all the results on extrasolar planets that are coming out on the way to that civilization-changing discovery. First, I thought, these people are just looking under the lamppost for their lost keys, because the light is good, and not because it’s what we really want to know. But I was wrong. Now, I think they’re building a science from the ground up, and pretty soon it's going to be towering to the skies. I think that's pretty wonderful. I have to say, though, I do cringe at statements like, "Oh, the solar systems we’re finding are completely different than we thought, different than ours." I think that's nonsense. The planets we've discovered may be locations than how things are arranged here, but they are the kinds of planets we see in our solar system, and how they’re arranged both here and elsewhere is the guts of the science. Even scientists are prone to this nasty habit of ridiculing those who came before them as being “completely wrong.” It’s almost never true, but it sounds good in press release.

You know, other things that have really impressed me, though, are not all astronomical matters. Carnegie has an Earth Sciences Laboratory, too. How we have progressed understanding the Earth itself, how its continents have circulated, and how Earth’s internal heat source, radioactive decay, has changed its evolution on a global scale, particularly plate tectonics, and how that might be essential for life. An idea like that was unimaginable when I was in graduate school. We now talk about that a lot in astronomy, how the interior properties of a planet, its store of radioactive energy, its dynamo generating a magnetic field, and more detailed things going on inside we don’t know about, are actually going to be directly impacting whether life is there, and how that planet’s conditions have evolved. Imagine thinking about that in 1980, when we didn't even know of a star we could point to and say there's a planet circling it, that’s like complete ignorance, I would say. And it's not even clear that we can imagine we'll ever know those all the things we want to know.

So, if you want to close on something I heard recently that captured my imagination, Jim Peebles, the great theorist who had blessed my PhD thesis fifty years ago (he’s still going strong), I was listening to Jim Peeble’s Golden Webinar (to get ready for my own) was talking about grasping the size scales of the universe, something I needed to do well in mine. Easy for an astronomer who's thought the vastness of space, the size of galaxies, for their whole career. Well, yeah, they're big and it’s really empty. But it really stops people, you can't get them to continue the journey because they're so blown away by the size of things, something you want to get past. So, he was talking about this, he rolled out old “powers-of-ten” journey where he started close the Earth and the backed his way out, increasing the vista by ten each time. When he got the a view of our whole galaxy he was saying "Well, we're like one of those stars down there, and the distance to their closest neighbor star is four light-years. It'll probably take us forty years under the best circumstances to get to our nearest stars, and how could we report back?" Wistfully, he continued, "You know, there are billions of planets in our galaxy. Could you imagine what it would be like to know what's going on the surface of those planets?" And then he said, in a tone that surprised me- it was a voice of hopelessness I never expected to hear from him. "And we will never know." It was a sense of despair for a person who has been able to conquer a lot of almost insolvable problems. He repeated, "We will never know what's going on in those worlds."

It caused me to think a lot, over the next days. Did he really think that? Did I really think that? Of course, in a way, yes, I do, because we'll never set up a conversation, which is the way we think of things, with any of those worlds. We still have dreams that we will somehow achieve remote sensing that will reveal something about these worlds and maybe even life on them, but even that has got to be pretty limited to a one-way conversation. It gets more interesting every year. Astronomers talk about what we'll be able to say things about the weather on another planets, or volcanos, and astrobiologists talking about whether there is life on this world. But if we ever want to know if there's intelligence, and civilization, and culture, it seems impossible. But I was recounting this to my wife, after losing sleep on this question, and wondering why it bother me so, and well – he's an exceptionally smart person. And, I said to her, "Maybe, to imagine that we’ll have to have a conversation, yes, that’s probably never going to happen. But if I were a civilization on one of those planets, and I wanted other beings to know what goes on here, and what our life forms are like, and life’s evolution and something about our art and science, and history. I think I would realize that I could build a million probes and send them out into our galaxy. And these probes would be like libraries that stored their planet’s history and the history of life. And in 10 million years or so, these libraries would drift to cover the whole galaxy, and that’s nothing compared to the age of the galaxy. I could send them out at maybe one percent of the speed of light, these circulating libraries. And I would know that any civilization like mine would eventually find one and figure out how to read the library as it passes by.” It sounds a bit crazy, but I can imagine a space-faring civilization wanting to do this.

Even we can imagine building such things, and robots maintaining themselves, it doesn't sound impossible, and we’re just primates. So, we might someday know if there really are a lot of civilizations, and what they’re all about. In a way, all these ideas were explored by Carl Sagan in Contact, where a human is transported somewhere else in the galaxy, after plans for building a machine to do that were decoded, plans the aliens broadcast via radio. When she arrives, Jodie Foster hears, from a hologram of her father, that this has been going on for billions of years, and there is a network of civilizations that watches for new members among the stars, and contacts them, when they think we’re ready. We don’t know that this was a real ambassador of this ‘intergalactic union” more likely it was just a smart recording, a “welcome robot.” I thought It was brilliant.

So, back to Peebles, it was interesting to me that there was a sense of limitation and disappointment when he said this. But in fact, we'd be perfectly happy – wouldn’t we? – just to know, without having a conversation, to know what was actually happening on other worlds. I wouldn't be surprised if those probes are out there right now. And we’re so primitive, the way we think about this is pathetic: No, we better not reveal ourselves, because we'll be attacked! which is really a comment about the human species. You can see that side of us on display now; it's really come to the fore in the last few years. 

Zierler:

Alan, that's a perfect lead-in to my next question, which is really a philosophical, or maybe even a spiritual question. If you'll permit yourself that you've gained some wisdom over the course of your career, and in the way that you link your interests in the arts and literature, with a certain fearlessness that it's okay in science to be emotive and attach poetry and wonderment to scientific endeavors. Really broad question, in all of your explorations of how the universe works, what, in the process, have you learned about humanity?

Dressler:

I’ve learned about humanity as a result of my career as a scientist, on balance are not good. It’s about the role of science in creating the prosperity of human life at this moment compared centuries ago and for millennia, when the lives of normal people were “nasty, brutal, and short,” as Hobbes said in 1651. There are still billions of poor people today, but even the lives of the poorest have improved through my lifetime and, by any measure, they live better lives than humans have commonly endured. Why? How? Chemistry, physics, biology and the engineering of their discoveries has drastically reduced hunger, starvation, toil, disease, exposure, infant mortality, and many other hardships that were the norm for almost all of human history. Science has increased what “wealth” an individual human can produce and as a result humanity, as we think of it today, offers to billions of people comfortable lives that can share the bounty of human creations in art, literature, and music, to have time and resources for hobbies and recreation that previous generations did not have, and the opportunity to explore the world beyond their town or farm. This is what we call humanity, today. And yet, to my astonishment, science is not given the credit. Electricity, well, that’s because of Edison and Westinghouse. (Not Maxwell or Gauss, or Franklin for that matter.) Who transformed agriculture? Archer Daniels Midland. (Not Beijernick and von Liebig. Who?) Computers? Well, that’s IBM. (Babbage, Turing – Never heard of them!) I talk with ordinary people about my life as a scientist and I have found that most believe that what has made life incredibly better is great engineering, or they don’t even think about it at all. Their opinions about scientists are things like “scientists are continually changing their minds and are often wrong. We were told to margarine was healthy and butter is not, now scientists say it’s the other way around! And what about Pluto? They said it was a planet and now it turns out they were wrong about that!”

When I was eight years old, I started to be aware of the role that science was playing in making the world a better place, science was doing amazing things. I told you the story about the polio vaccine. I myself had open heart surgery that saved my life, in 1966– the very first attempt at that had been in 1952! I saw transistors revolutionizing the world of entertainment, communication, and just about every electrical device I would ever use. Watson & Crick discovered the structure of DNA, the actual language of life. Of course, astronomers were changing our ideas of the universe. In 1958 Walter Baade, an astronomer at Carnegie, showed that there were different generations of stars – the universe had been “evolving” for billions of years. Humans first orbited the Earth when I was thirteen and landed on the Moon when I was twenty-one. It’s just a smattering, but all around me things were changing fast, things that made me believe that science was responsible for making the lives of humans better, a lot better. I was a little too young to understand it all, but I got the gist of it. I never thought there would be world government- I don't think many people ever wanted that but there was an idea that maybe there would be more peace in the world because of science, because of learning things about who we are, our common humanity, where we came from, things about ourselves that would bring all people closer together, realizing that they were all part of this amazing story that science was telling, truly the greatest story ever told. Even as nuclear weapons were threatening all our lives, there was hope that they might make war obsolete as a way of solving the perpetual disputes between peoples and cultures.

I saw so much that I thought was for the good, I never thought about the forces that stood against this, particularly organized religion that dismissed the very notion of truth or science independent of a supernatural being, and even profitable businesses that aligned against the public good, including sending us to war. (Nowadays you can add to that the incredible harm and violence small numbers of people can do to all of us, thanks to modern inventions of communication and the amount of ‘energy’ they can get their hands on.) So, you can imagine how disappointing it is to find out that, today, there are probably fewer people who recognize the crucial role science plays in making a better world and working for the good of all humanity. Compared to the time of my childhood, I think people in the U.S. are less well educated in science, more skeptical of authority that might flow from facts and truth, more enthralled by religions and other beliefs, less tethered to reality and more interested in alien visitors from space, the supernatural, or vast conspiracy theories. I know less about other countries, but from my reading I think the situation is as bad in many western democracies. At a time when science is the only way to avoid global catastrophe, the unprecedented, existential threat of climate change, we see far too little recognition of the seriousness of our situation.

And I lay much of that on people turning away from science, from any notion of facts or truth, to a transactional process where power is the ultimate decider. I see great tensions, and nascent movements worldwide of societal conflict, and I don't have the faintest idea how or if it's going to be resolved. But I see it as reflective of the Jekyll and Hyde faces of humanity: the passions that drive us to make art, do science, build a better future, seem to have another side, passions and impulses hat drive terribly destructive things. I was telling my wife something I read about our closest biological cousins, chimpanzees and the bonobos. Chimpanzees regularly exhibit our darker side: competition, war, violence. While bonobos are matriarchal and generally peaceful, they maintain their relationships and settle conflicts through sex. If our ancestors were more like the bonobos, would they have been great artists, great scientists, great philosophers, or would those traits wither in a creature that has abandoned conflict as a way of life? Of course, I don't know. But nearing the end of my life I'm very worried that the optimism of my youth that the world was getting better and that all of humanity would reap the benefits, that this was just a child’s view, and that humanity’s darker side, if it prevails over the next several decades, could lead to our demise and, horribly, the destruction of much of the living world that spawned us. I'm pretty sure, now, that I will not live to see these challenges will be met and resolved in a way that my optimism would return, to the hopes and dreams of my youth, and that is source of profound sadness.

Zierler:

Alan, looking to the future, you're humble, so I'll say it for you: your work style of being the sole author of so much of your research, because of the intellectual nimbleness it allows you, to be creative, to think in broad terms, if you connect that work style with all of the discovery that you've been responsible for, surely I would think, and maybe I'm just being naive, this must be a model that resonates with some people, even in our era of big science and huge collaboration. Sociologically, do you see this resonating with the next generation of astronomers? Are there people who question the value of these massive collaborations when so much good work can be done just on an individual basis?

Dressler:

Well, I’m still working in the nest of the Carnegie Institution for Science, and here I can see that many people with a passion for science are looking for that environment in which to grow as scientists. We’re still hiring young people who are already incredibly productive in something close to the style that once dominated the whole field. It’s still here. And I know that there are still scientists that are drawn to this, some of the best, and while I’m not saying that the other big collaboration approach can’t achieve great science, I’m cheered to see that this style that I adopted is still able to do so, and maybe even more likely to do so. If we give young scientists the resources to follow the Carnegie way, then they have a choice; they can limit themselves to the small science path and they can involve themselves in larger collaborations to the extent that it augments what they can accomplish, as I see many of them doing. They tend to be in the creative roles in relatively large groups, and they also tend to pursue their independent work. We hired a couple of astronomers here, husband and wife, who are like that. They both have their own projects. They're doing something with a group of about ten of us and they are part of big projects, too, with facilities like Hubble, JWST, and the best ground-based facilities worldwide.

So, they're doing both, but they greatly value the opportunity to choose, and to work within, both models. I’m really glad they’re here, there’s a lynchpin for the department, and I’m happy that the salary I gave up when I retired was sufficient to hire them both. They were really torn about whether to come to Carnegie, because it wasn't a university, and they liked teaching, and they thought graduate students would be an essential part of their research. They had an excellent offer from one of the best university departments. I told them, "Well, I think you should come here and try it. You could always go to a university if you choose. It's a little harder to go the other way around." There's one astronomer here who's all-in with big science. She's running a huge project, it’s called Sloan V, costing tens of millions of dollars, with our DuPont telescope, her very large team will gather spectra for millions of stars in our Galaxy, covering half the sky. It will be revolutionary in studying how the stars in our own Galaxy created the chemical abundances that built the planets, and life, on Earth for sure, but likely on billions of others.

So, this is really big science happening at Carnegie. I’m not sure our way will survive that, but I’m hopeful that there’s room in the tent for both approaches. We have big science sticking its head in here and there, and we seem to be handling it, but I worry it could change the way we interact, the way we talk, the way we think, that’s the real issue. So, I don't know how that's going to work out, but I also know that a lot of people outside have seen the Carnegie model, and they've tried, in some respects, to imitate it by making fellowships that are really wide open, not a proscribed subject or project and not working for a senior scientist. The number of fellowships like that has grown a lot in the general community during my career, and now there are new places somewhat like Carnegie, for example, the Simons Foundation’s Center for Computational Astrophysics, many centers funded by the Kavli Foundation. I've been noticing the way Carnegie’s model has been spreading, and I’d like to think our institution seed it. Maybe it's almost like an ecosystem finding its balance in the era of big science. Because the facilities that we use are so expensive, it's hard to square it with individuals or small groups. It becomes a matter of diversity and involving large numbers of people in the field, that’s just the way it is when you're spending billions of dollars. I just hope that too much of the science doesn't get lost because of it; I'm not the only one who worries about that. But that’s the way it is and there’s no way around it. My field has gotten really expensive. 

Zierler:

Alan, last question, and let's end on optimism. For the remainder of your career, however much you want to remain active, and however long, what are you most optimistic about, both scientifically and sociologically?

Dressler:

Well, I'm optimistic about both the efforts that are going on in ground-based astronomy and from space. I think there's still strong backing for the traditional studies that have defined the field, and I think there are subjects, like galaxies, their stellar populations, and their histories, that need to be finished up, maybe in the next twenty years, finished in the same way nuclear physics has move on to its fine points and is tying up loose ends. For the blossoming field of extrasolar planets, and the connection to life, those two poles, NASA and other space agencies around the world, and ground-based facilities, are all well-positioned to make extraordinary progress in the next decade or two. If we can really make a convincing case that there are other planets capable of supporting life based on the same chemistry we have here, and even show from remote observations evidence of life on some of them, that will be a crowning achievement for astronomy, one that should secure its support from governments and private sources for the foreseeable future. The science done by these space agencies around the world has never been dependent on majority support in their countries, I think, and that's a fortunate thing, because I don’t think we’ll ever have that. And some other science disciplines are in fact having trouble justifying themselves as worthy of government support when there are so many pressing social issues and climate change research that are crying out for funding. But the fact that astronomy produces results that inspire people- a view to another reality, that’s a precious thing. You look at those pictures from the Hubble and say, "Wow, is that real?" As I said earlier, any good artist can make a picture that is more crazy, colorful, exciting, potentially awe-inspiring but people know instinctively what they are seeing a real, and that is everything.

So, I'm optimistic about the future of my field. I think the resources are there. The technology is there, mostly – some things we still need to build are very challenging. We're not trying to do easy things; we're trying to do very hard things. We have a good story to tell, and there still are enough people in our world who cherish the value of learning, the virtue in reaching out to explore the unknown and the not understood. Still, there are billions of people who are looking backward, to ancient traditions and ways of life. They might be Orthodox Jews who think the apex of their world was the sixteenth century, or Muslims, and Christians who hold fast to the idea that humanity reached its finest flowering in the eight century, or even the first. But I have to say, for the first time, I think the majority of the people in the world are not wedded to the past. That is an optimistic view, one that says we may be finally moving in what I have always thought to be the right direction but are still years of struggle ahead with those who worship the past and cling to the supernatural. I may have believed, when I was a kid, that a transformation was underway, but now I see how far we really are from a new view of the world and our place in it being universally accepted, and how difficult it's going to be resolve the struggles that prevent that, but maybe, I hope, the Herculean effort that will be needed to save our planet from our failure of stewardship will carry us, maybe even propel us, in that direction. You have to be optimistic to believe that right now, but maybe an existential crisis can lead us to a better world for humanity and all Earth’s creatures. We can hope.

Zierler:

That's right. Alan, it has been a great pleasure spending this time with you. You are a fount of perspective and institutional memory, and your ability to communicate the science is so important for the historical record. So, I really want to thank you for spending this time with me. Thank you so much. 

Dressler:

Thank you, David.