Alan Dressler

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ORAL HISTORIES

Photo courtesy of Alan Dressler

Interviewed by

David Zierler

Interview date

February 24, 2021

Location

Video conference

See catalog record for this interview.

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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

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Abstract

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.

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.

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.

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.

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.

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.”

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?

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.

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.

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]

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.

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.

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.

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.