Oral History Transcript — Dr. Allan Sandage
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Session I | Session II
Weart:This is an interview of Allan Sandage by Spencer Weart on May 23rd, 1978. We must apologize for Dr. Sandage’s hoarseness. I wanted to start with some general questions. We're going to be getting into the steps to the Hubble diagram and so forth, but first, I just wondered what changes there might have been in the nature of observing between when you started, 1950s or whatever, and now.
Sandage:The work at the 200-inch was almost entirely photographic in the beginning. The first focus to be activated was the prime focus. And for perhaps five yearsy the two types of observations were direct photographic plates, and spectra by Humason to extend the red shift. Then gradually photoelectric techniques came in. Baum put his first DC photometer at the prime focusy and then developed a pulse-counting photoelectric photometer.
Weart:You learned to use all those things from Baum?
Sandage:The photoelectric photometry became a standard technique that many astronomers had as their training in the 1950s. So I learned photoelectric techniques on the 100-inch and the 60-inch on Mt. Wilson, and it was the same type of equipment; it was.; universaly and it was an observatory instrument. Baum certainly did check all the observers outy the first few times that they used the equipment he developed.
Weart:I see. What about subsequently?
Sandage:In the last five to ten years there's been a revolution in detectors. The changeover began when the DC equipment was transformed to pulse-countingy when Ed Dennison came and the Astro-electronics Laboratory was developed within the Hale Observatories. then there were devices such as Oke's multichannel scannery which was put at the Cassegrain focus of the 200-inch, and many instruments then were developed for that Cassegrain focus. In addition to the multichannel intermediate-band scanner, there was developed an image tube spectrograph, (Maarten Schmidt was involved in that) and that used photographic plates or film pressed in contact with the back end of the image tube.
Weart:SIT or whatever?
Sandage:No, the first generation fast spectrograph which replaced Humason's direct nebular spectrograph at the prime focus was the, Schmidt-Bowen-Dennison image tube spectrograph, at the Cassegrain. The most recent development, which has occurred in the last four or five years, is the use of solid state imaging detectors, of which the best example we have now is the SIT, the silicon intensified target. There's a spectrograph using the SIT detector now at the Cassegrain of the 200-inch. That soon will be replaced by a still more efficient device called at CCD.
Weart:Change coupled device?
Weart:Tell mep how does this change the nature of a night at the 200-inch?
Sandage:For many projectsp you can now sit in a data room; there's TV viewing and guiding at the focal plane, and the images are brought down into the warm control room. For other activities, like taking direct plates or photoelectric photometry at the prime focus, you still have to go and ride in the cage.
Weart:How is your time divided now? Do you spend a lot of time down with the TV, or do you still spend a lot of time in the cage?
Sandage:I've got several programs going which require both capabilities. When the seeing is very good and the north galactic polar cap is up, I'm usually in the cage taking direct plates. There's a new program of mapping the density gradient in the galactic halo, and that requires direct plates and photoelectric photometry for calibration. Then there's a standby program: the survey fields for radio-quiet quasars are being observed for red shifts of the candidate objects, and that's with the image tube spectrograph at the Cassegrain focus.
Weart:I'm interested because it seems to me that there's a changeover, and that twenty years from now there probably won't be very many people sitting up at the prime focus.
Sandage:I don't know whether that's really true, Spencer, because the need for direct photographs--first of all, to find nearby resolved stars, and to extend the extragalactic distance scale, or the size of the H A regions in nearby galaxies--the need for those photographs will always be there. Now, one could envisage putting the astronomer in great comfort, at tremendous expensey by making an automated camera.
Weart:You think it would really be too much expense.
Sandage:I think that's a tremendous expense for just getting the astronomer out of the cage. It's a nice place up there, and you can stay warm in the winter time. It's not as if you're out in the bitter cold, where certainly the efficiency does go down.
Weart:You have these electrically heated suits and so on?
Sandage:Yes. It's certainly a tradeoff, between the expense involved in automating the camera, with a film magazine of some kind, or keeping the astronomer up there. I think that the automation for the photoelectric photometry will proceed, and we'll have television acquisition of the field, and stepping motors to put the filters in and out; everything done by hand can clearly be done automatically, by remote control.
Weart:Does this make any differencey whether you're observing at the prime focus or down in some room watching TV--does this make a difference in your feeling about observing? The effect it has on you?
Sandage:Yes. The way one operates is clearly much more comfortable in the data room, and you can make decisions more easily. You can also keep up with your book work. But there is a tremendous advantage, which is not easily stated, of sitting in the dark in the prime focus cage, close to the instruments. It gives you a great deal more time to think about the consequences of the data coming in. It's certainly true that on the long nights when one guides the direct plates, many good ideas for interpretation come. The mind is put in a state when it's more receptive to call things up from it's deep recesses. I find that that time in the prime focus cage is very important for that type of activity.
Weart:What do you think when you're in the prime focus cage? Is it mainly about the data that's coming in?
Sandage:It's about the next stage in the process. Suppose these plates are fine and they give the following information--what is the next step to solve the problem that's been posed? (Knock on door; brief interruption) Much more to the point is, you have to have contingency plans if the seeing changes, about what to do for the next plate. So you have a good seeing program and a bad seeing program, and you have to trade off.
Weart:So you're always aware of the seeing.
Sandage:That's right. And that's really why I think itli~ii impossible for any long-range program to be in the hands of just trained observers or technicians. I think it's crucial for the astronomer to be at the telescope, conducting the experiment himself.
Weart:Do you ever look up at the stars?
Sandage:You're looking down toward the mirror in the prime focus cage. Certainly, you look out to see if it's clear; you open the neoprene cover which covers the prime focus station and look out.
Weart:I see. Does it get tedious up there, boring, sometimes?
Sandage:I don't find it so at all, no. I usually stay in the cage all night long without coming down. There's music piped up, and there's an intercom to the night assistant, so the information can go back and forth, as to the right ascension and declination and the technical information about the plates. But it's a time really to think about the problem that you're trying to solve. So it's not boring or tediousy in that sense.
Weart:I didn't realize music was piped up. What do you like to listen to?
Sandage:Oh, I'm very Catholic in my tastes. I like classical music very much and I like opera very much, but the night assistants don't always like that, so-----
Weart:They listen to it too?
Sandage:They sometimes listen to it.
Weart:On this subject, tell me, what avocations or hobbies do you have?
Sandage:Well, music is a very important part of my life. And opera, in particular, is a strong aspect of that avocation. I don't play any instrument well; I used to play instruments when I was a boy, but I don't now. My children and my wife are very musical. My older boy has a knack of being able to pick up any instrument and within a week, play it almost first chair; he can play 25 different instruments now. He composes, he plays the piano.
Weart:You must have given him a lot of exposure to music.
Sandage:He has a lot of exposure in the home. Both my wife and I are quite strongly dedicated to music, and the two children think that the opera hobby is interesting. They know a lot of opera now. I tape the opera every Saturday, from the Metropolitan. Another hobby is cooking. I started three or four years ago to try to understand how to cook, starting from no knowledge at all and it's gradually coming. Bread, it took me three years to really understand how that works, but that's coming fairly well now. I used to garden a lot, but I don't garden very much any more. I'll have to go back to it when the boys leave for college, but I don't do that now.
Weart:It's amazing you have time for all that.
Sandage:No, that rests the mind quite a bit. And I read very much. I read novels, I read autobiographies, and I still read lot of philosophy.
Weart:I'm trying to get a picture of you as a whole human being. Would you mind telling me your religious affiliationy if any?
Sandage:I'm not formally a practicing religious person. The background that civilization has passed through in its attempts to understand the mystery, and the formal religions that have been formed out of that attempt--the cosmology of the common man--is a fascinating segment of human history. I think no one can really understand where we are now, regardless of their beliefs, unless they understand the history of the traditions in all three or four of the major faiths. So I've read quite extensively in the New and Old Testaments and in the texts of Buddhism and Taoism, to try to really understand the human condition as it's been codified in the formal religious.
Weart:Do you have any religous convictions? Are you a Christian or -
Sandage:I don't know what I would call myself. I believe that the revealed religion, in the formal aspects of what the Christians believe, is a mystery, and it should be treated as a mystery. I really don't believe that there's any conflict between science and religion. I am certainly not in sympathy with the Fundamentalists. A religion is a form of philosophy which is much deeper than the literal interpretation of the Bible that the Fundamentalists will say. But I'm also not an atheist, in the Fundamentalist sense. It is, I think, rather impossible really to give a concrete answer to that question. There's a mystery out there, and it's outside the realm of science. Science can only answer the question of how, when and where, and perhaps what, but not why. The question of why is outside the scientific purview; but that's still part of the whole picture.
Weart:Do you feel that there's a harmony between science and religion? To be more specific, for example, between what we now know about cosmology, about the way the universe was formed, and what the old religions have said?
Sandage:Well, the cosmology of the Old Testament is a theory. It's a way to describe the mystery. Clearly it's not true in the literal sense. But that doesn't mean that the description is any less--well, it's a poetic description of something that happened. And it did happen: the world was created. If you believe anything of the hard science of cosmology, there was an event that happened that can be age-dated back in the past. And just the very fact that science can say that statement, that cosmologists can understand the universe at a much earlier state, and that it did emerge from a state which was fundamentally different--now that's an act of creation. Within the realm of science, one cannot say any more detail about that creation than the First Book of Genesis says.
Weart:You can't go back before the first millisecond or whatever.
Sandage:Whatever. That's right.
Weart:There's some limit to--.--
Sandage:--to the description that science can give, on the basis of the clues that have not been wiped clean by the subsequent expansion.
Weart:And beyond this is mystery that you spoke of?
Sandage:Well, I think the whole rationality of the universe is a mystery. The fact that Newton's equations or Einstein's equations work is one of the world's great mysteries. And in that sense, I'm very religious.
Weart:I sympathize with that.
Sandage:But religion is not the right way to describe it. It's a feeling that there is order in the universe that is not understood, within the framework of the present description that is scientific. That order is what scientists are trying to uncover. And it's the fact that every discovery that's made shows even greater order, instead of disorder, that makes science possible, first; but alsor that is the basis upon which a philosophy of science can be built.
Weart:From your description it sounds as if this could almost provide a guide, in a way, in your work. That is, you're always looking for a greater order.
Sandage:Well, I don't know. I think of myself as a hard-nosed scientist. I think there's no room in the time one spends in the laboratory for religious speculation, for anything but attempting to find out what the facts are, independent of the noise, to pull the facts out of the noise. Then the process of model-building begins. One of the principal aims of science is to built models, and the raw materials for those models are the data that you collect in the laboratory. And there's no room whatsoever, in the data collection, for speculation. It's a very strange combination of talents that a good model-builder has. He has to have speculative ability, he has to have generalization ability, he has to induce and deduce at the same time. It's an art. Yesterday we said there's no place for art in science. I didn't mean it that strongly. There is a place.
Weart:Art in the sense of a skill?
Sandage:Of a skill, of intuition, of jumping to the answer without knowing the logical steps--all of the great people in science have at one time or other stated how they've arrived atconclusionsy and it's by the strangest mental process of non--logical deduction, or induction. Poincare has this marvelous essay. You've got to prepare the mind, as Pasteur saidy and then something miraculous happens in the interconnections of everything you've put in the mind.
Weart:You've experienced this yourself?
Sandage:Two or three times. I think if a person is really very lucky in his lifetime, he will experience some feeling of elation at a construction he's made that works.
Weart:Which times were these for you?
Sandage:Well, when I've been able either to solve a problem that I thought was impossible, or when a hypothesis was proven. The final observational proof that radio-quiet quasars existed, those two or three months of all of the intermediate steps (many of which proved to be incorrect in the meantime)-- when I was going down that road and seeing, or believing, how things fell into place and drove the problem to a particular solution--when all that was going on, in period of six to eight weeksy there was never a time before that, that was anything like that. That really was a very exciting time, and a mentally active time. In a longer-range situation, the completion of long-range programs such as finally making the last step that Tammann and I did do in the steps toward the Hubble Constant--now clearly that problem is not solved ......
Weart:Still, that was the last step of a very long program.
Sandage:That was the last step that we had outlined, over a period of four or five years, and when that was made, that was a. much quieter type of elation.
Weart:So it's not this instant, like Poincare talks about stepping down from a bus or whatever, and having it come like that (snaps fingers)--
Sandage:I have had certain periods of that instantaneous recognition. For example, when suddenly I realized that the blue interlopers were really the same blue objects that Haro and Luyten had been cataloging. Or, during the entire time of the radio quasar quest, the times on the mountain when tentative identifications were taken to the mountain and then photoelectric: photometry would show that it was in fact an identification. There was about eighteen months in 1963, when the first four or five quasars had been isolated--four objects had been isolated before Maarten got the red shift of 273. Then the whole field completely opened up, and many techniques were used to identify. So in a period of about a year, there were fifteen candidates one always took to the mountain, and as those statistics piled up and the first Hubble diagram of quasars was coming out--that was a very exciting time also. But there was no flash of insight that we're talking about, when the things came together. One other time for me I think, of insight--a somewhat more gradual devlopment--was when I was working on the paper in 1961 of the observational tests of world models with the 200-inch. That was a review paper and a semi-theoretical paper. There were hardly any observations in it. It was a challenge that I didn't know whether I could do or not. Every week parts of that became clearer, when the volume elements for example in co-moving coordinates, the analytical expression for the volume elements, fell out. Or the analytical expression for the time. Up to that time, all of those things had been given in series expansions of the red shift, but with the knowledge that there were closed forms within the Friedman modelst it was a question of how to find those closed forms. And, as all those equations became understandable, and the integrations were there, and more insight was developed, and one lived with the problem for month after month--there was a euphoric feeling of really understanding a subject that seemed so un-understandable before. So the personal development during the writing of certain papers, that at the moment they were begun seemed possible to complete--that's always a----
Weart:--as the paper progresses, the things fit together, particularly a mathematical one where the formulas come out in a nice closed form.
Weart:That's the only real theoretical paper you did of that nature, isn't it, where you really go into advanced theory?
Sandage:Well, I wrote three theoretical papers on that subject. There were two papers following that.
Weart:What is it that keeps you working--long nights, a lot of work and so forth?
Sandage:What keeps you working, Spencer?
Weart:I'm interested in the subject.
Sandage:I'm fascinated with the subject also. Clearly, if the interest in astronomy weren't there, then there'd be something strange about working this way. I'm very interested to solve posed problems. It's a puzzlesolving syndrome.
Weart:Has it been this way from the beginning?
Sandage:From the beginning. From as long as I can remember, back into my childhood, the setting of goals and the completion of those goals seemed to me to be where all the actions of the process of living was. I thought everyone was made that way. I think Ilri-i extraordinarily fortunate that some chemical makeupy or something in the mental process, has been with me forever like that. Itlii-~ not hard to work. I am very bored if I'm not trying to reach a predetermined goal
Weart:I understand that.
Sandage:It's certainly true that there have been periods of inactivity. There have been periods of depression, in the sense that once a problem is solved, and there's no immediate short-range goal--that is, there are several very long-range goals----
Weart:--things that you're doing every year---
Sandage:--all the time. But that's not enough. I think there have to be smaller problems. For example, the high-latitude galactic nebulosities, the reflection nebulae--that was perhaps the most interesting small problem that I can remember.
Weart:It appeared by accident, didn't it? You had no idea that would be there.
Sandage:That's righty that appeared. We were doing a survey on 127-04 plates those are the new fine-grainedy red Kodak plates that allow one to go much fainter than coarse-grained plates to find distant clusters of galaxies, to extend the Hubble diagram. But on many of those plates, in the north galactic pole, there appeared wispy nebulosities. So these nebulosities were found, and they were in high latitudes, and that was new and strange. And the question was, what were they? Well, the hypothesis was that they were reflection nebulosities illuminated by the general light in the galactic-plane. That then required a solution of scattering problem. Now, for a theoretician, that was trivial. But it was not trivial for me, and the working out of that problem took three or four months of very concentrated trial and error work, and then a very short paper appeared. But that was one of those times. The solution to that problem was an excitement.
Weart:I see, there are periods when you'll find a short-term problem and you'll really work on it, and then you're sort of waiting for the next one.
Weart:Well, to get back to where we left off yesterday, we were talking about quasars. There's still the question of the N galaxies, where you were searching for variations, and so was Oke independently. For one thing, you and Oke were observing the same galaxy, 3C 371?
Sandage:Apparently so, yes.
Weart:I would have thought normally you'd knw very well what other people were doing.
Sandage:Not in detail. You know the general areas people are working on. And there's quite a bit of overlap, because two different people approach a given problem from different directions. Oke was looking at the energy distribution with his multichannel scannery and I was monitoring quasars for optical variations as the identifications were proceeding. This was in 1966, and the great thrust for optical identification was still on. It was tailing off; the peak had been reached about 1965. But just in the process of the enormous observing list that each observer accumulates 3C 371 appeared on both lists.
Weart:I see, because your lists are so large.
Sandage:We overlapped at lunchtime at Palomar one run, and we were talking about various things, and it transpired that we both had found a variable galaxy. Because there was fuzz around 371, that was clearly a galaxy underneath from the very beginning. We compared notes, and lo and behold, it was the same one. So the papers didn't come as a surprize to either of us. We understood that each of us had found it independently.
Weart:I see. Did this have any impact upon your own thinking about the cosmological distances of quasars?
Sandage:No. It was really clear, I thinky at a very early time that quasars were at cosmological distances. In 1963, at the Hamburg meeting of the IAU, there was not much discussion; Schmmidt had only found the red shift two or three months before that. But by 1967, in the joint discussions, the pros and cons were well understood. In the invited discourses of Ryle and myself at the Prague meeting of the IAU the evidence was presented. Ryle's evidence was that the radio galaxies, which no one contested, had linear sizes of the double radio sources that were identical with quasars. And my evidence was that the Hubble diagram for elliptical galaxies formed the lower luminosity bound to the quasars, and therefore, the simplest model was that they were events in the nuclei of normal elliptical galaxies that could only make the composite brighter.
Weart:Then also a little later you did counts, finding either constant or outward increasing space density, that was about the same time.
Weart:In that paper on the counts, you say, "This eliminated the local hypothesis." It didn't eliminate it for your it just eliminated it, period.
Weart:Tell me about the subsequent development of your views of quasars. You were telling me last night, what your current view of quasars is or what it might be. How this came, and----
Sandage:It's not mine, clearly.
Weart:Oh, I realize you didn't originate it. I'm asking everybody, because I'm not only interested in the history but I’m trying to get a cross-section of what people's views of these things are now.
Sandage:In the attempt to understand the great energy source involved, many mechanisms have been proposed by many people, and in the discussion of these mechanisms certain generalizations have stood the test of time. One is a dynamical runaway--and this is Spitzer, Axford, Gold--where, when the density becomes high enought then dynamical friction will cause the orbits of stars to decay, and matter is then drawn into the nucleus. Coalescence or collisions occur, and the potential well deepens, and you have the beginnings of a black hole or at least a very interesting high-mass, high-density, almost singular point.
Weart:A supermasive object at least.
Sandage:That is right.
Weart:And this seems to you currently the most interesting?
Sandage:From a strictly astronomical point of view, I think there's no question, and most astronomers also believe this; first of all, that Seyfert galaxies, N galaxies and quasars are part of the same phenomenon, it's just a matter of how high the rheostat is turned up; that they are events in the nuclei of galaxies; and that quasars themselves are events in the nuclei of elliptical galaxies. Therefore, whatever the detailed mechanism is--the Spitzer dynamical runaway, perhaps even a black whole to begin with, and matter circulating in the last few orbits around the black hole radiates--the astronomical problem is solved. Not the physical problemy but the astronomical problem.
Weart:Can you trace how you came to adopt this view? Was there any particular point or reason why you picked this up? Clearly in 1963 no one had any idea what the mechanism might be.
Sandage:That's right. I would say that the view of what the physical mechanism is, is the prevailing view. It's the canonical view. There are some variants of that. We talked about how one came to that.
Weart:Right, but in terms of the mechanism, was there any particular time when you began to adopt this? Is this very recent that you've adopted it?
Sandage:The beliefs in the physics have come perhaps in the last five years, it seems, the various theories and the successes and failures of those theories. The fact that it's somehow connected with the nuclei of galaxies, where the potential well is the deepest, automatically forces you to some sort of dynamical runaway problem. And that problem was solved initially by Spitzer. I think it's the survival of the fittest theory that is involved.
Weart:I attach some of this to Lyndon-Bell. He was the first person that I recall putting forth the idea of a black hole at the middle of galaxies.
Sandage:That's right. I'd forgotten that entirely.
Weart:How do you feel about black holes? What is the probability that there are black holes?
Sandage:(laughs) That's like asking, what's the probability that qo is less than one? It either is, or it isn't. I don't know anything about black holes.
Weart:So you would neither be surprized if did or if they didn't exist.
Weart:Some people will say now quite definitely that black holes have been detected.
Sandage:I don't believe they've been detected. In the sense that the several good cases are not positive in (requiring large) mass.
Weart:OK, I can go along with that. To get back to some of the institutional things, I'm curious as to what in general was the effect of quasars and this whole development on the staff, both in terms of competition in-house and also competition with people at other institutions.
Sandage:There's no question that it changed the nature of the interaction of staff members. Since this is a very independently operated scientific observatory, where any staff member is free to do whatever he pleases, and there's no scientific direction, then when a new field opens up there's a great deal of interest and many staff members will become involved. There's normal communication and normal actions, as to what is proper and what isn't proper. I think there was a great deal of competition that was generated. In retrospect it was all very good, because it caused an enormous amount of work to proceed. The small amount of friction and personal conflict was generally solved before it became serious.
Weart:What would the mechanism be for solving this?
Weart:Between the two people concerned?
Sandage:Among the many people concerned. There were problems in the first two or three months of the announcement of the red shifts, primarily between people at Cal Tech, of priority, of wanting to be part of the discovery picture. All those problems which seemed so important have been sorted out, and they are all quite united and strong friends and colleagues now.
Weart:I'm interested in the way that the problems do get worked out. Is it completely informal or has there been any formal–?
Sandage:There's no formal way of solving staff conflicts. 1: think it's the good-naturedness of the people involved, and the understanding of the personal issues, where there were personal issues--certain things that are done and certain things that are not done--and I really believe that both at Santa Barbara St. and at Cal Tech, the personal animosities are almost nil amongst the staff now.
Weart:At present. That's what other people have told we too. Is it because the quasar thing has died down, in a sense--that there's no urgency?
Sandage:I don't know why it is. I think that it's not as important to the people involved. They were a lot younger at that time.
Weart:Which means that they had more---
Sandage:--more drive for priority recognition.
Weart:Because they needed recognition more, in a way, I suppose.
Sandage:People think they need quite a bit of recognition in the early time.
Weart:Did people feel that their main rivals were around here, or were they very concerned about other observatories?
Sandage:It certainly is true in all aspects of a rapidly developing subject in physics--one has a number of examples in the high-energy physics community--that there are races involved. Kitt Peak with Roger Lynds got into the quasar identification, and he was extraordinarily successful. He built in short order the fastestt most efficient spectrograph. Margaret Burbidge at Lickthen got into the problem. That not only drives the science forward, but it keeps everyone honestr and it gets to the solution of the very much more difficult problems that much faster. And no one suffered because of it.
Weart:Did people at that time feel a special need to reserve data until it could be analyzed?
Sandage:No. I've heard this statement from many people that came down from the mountain during that interval: they said, "Every month we come down from the mountainy we have a publishable paper.'' And in fact, if you look at the volume of short identification papers, either optical identification or spectra or photometry, there' s a flood.
Weart:So the point would be to publish it as fast as possible.
Sandage:Just as fast as possible. And in fact, this competition between people, within the observatory and among the three or four observatories involved, within two years took the identification of quasars from eight or niney in the first few monthsy to over 200.
Weart:Considering how far away they are--
Sandage:--how faint they are, it really was a strong push.
Weart:Was there any concern at this time about excessive attention by the press?
Sandage:Certainly the press coverage of the fast-breaking exciting field was present. There's concern about press coverage of science in general, on any subject. I don't know what you mean by concern. I don't think many people played to the press. The danger a scientist always has, when he does appear in the public press, is the censure of his colleagues, and whether the press report is correct or not, it's a medium which most scientists eventually find it is to their disadvantage to be in. So yes, the attention given to this in the press could not help but have caused common problems among scientists, where it always occurs.
Weart:OK. Well, let's get on to the steps to the Hubble diagram, and in general, your work on these long-range programs. We can't cover it all, globular clusters, H II regions and so forth--I don't think we need to go into all the details. I want to take some points. First I'm curious about general things about doing long-range programs like this. To take first things first, the question of money. Your early papers don't ackowledge any grant support, but 1: notice that starting around 1970 you began to get NSF grants, a few tens of thousands of dollars, and I suppose other grants for cosmology work. How did it come about that you began to apply for grants-:'
Sandage:Well, the program that was begun in 1950, to extend the Cepheid criteria beyond the local group, concentrated on the M81 group. The observations for Cepheids in NGC 2403 and M81 extended over a period from 1949, when the telescope first went into operation, to 1963; that was 14 years. To work up that material required some assistance. Gustav Tammann who was a young Swiss Ph.D. student (or held gotten his Ph.D.) that I met in Switzerland during a conference. Bowen said I could employ somebody to come and help with the work if I could find somebodyp so from 1963 to 1967, he came.
Weart:I think you could have had a large choice of people.
Sandage:It takes a very special skill. It takes incredible patience; it takes a certain long-range pont of view also; it takes a certain attitude. Those people are really very rare.
Weart:And you somehow recognized--
Sandage:At this conference one had three weeks to observe people, talk to people, and see whether you could judge. Henrietta Swope has that patience; Baade had that patience; Hubble had that kind of patience. This man clearly was unique and good. He was then brought over and his salary for three years was paid within the Carnegie Institution itself. That didn't solve the problem. That got 2403 done, but it did not continue the work. To continue the work, we had to find a salary for Tammanny and that was what the NSF grants were for. The success in 2403 was sufficient to continue beyond the Cepheid stage to the seven papers that finally emerged; it was the funding of his salary that we're talking about, and that was NSF.
Weart:So it wasn't particularly pressure from Carnegie or whatevery saying people would have to go out and get grants, that sort of thing?
Sandage:Well, he could not have been employed without the NSF grant. The Carnegie Institution budget is so very tight, that that was the extent of their resources.
Weart:I understand. How did you learn how to write an application? Did you just sit down and write one?
Sandage:Well, the process of learning to write is a very long one and I think a very crucial one, for anyone going into science. I think scientific paper-writing ought to be taught to graduate students. The technique of writing was developed over many years, out of the necessity to write the results of research up, and there was no special talent needed in addition to thaty to write NSF grants. It's crucial, clearly to state the objectives, to mount a sufficiently persuasive caser so that the referees will say, "We just can't turn that down." There's a way of writing that is honest, correct, but persuasive. One has to put oneself in the shoes of the person reading it to see if they'd be persuaded.
Weart:Referees could be the same for a paper or a grant applicationy the same sort of thing.
Weart:Did you ever have an important application turned down?
Sandage:Oh yes, many times.
Weart:Any idea why, what is it makes for one to be turned down'? I'm interested because NSF keeps no record of applications that are turned odwn, so it's very difficult to find anything out about them.
Sandage:I applied for funding of several projects, several different places, and it all depends upon the weight of the referees' reports. Referees are human beings with motives. Sometimes the proposals are not good; sometimes they're good but the referees don't want to see the work done. A whole variety of reasons.
Weart:Getting back to the long-term programs, I'm curious how they evolved. You've engaged in a number of programs, ten, fifteen year things. Do you ever find that you need to change them in the mind.
Sandage:Oh, sure. They are evolving every month; the main, direction remains the same, but the details of how to solve each particular problem, or the order in which the problems are solved, depends upon what seems possible at the moment, or what piece of information is needed to proceed. A long-range program I'm involved in now is the mapping of the halo. That involves four or five segments, and those segments are going on continuously, but the emphasis put on any given segment changes from month to month.
Weart:I see. Do you discuss this with people, how you are to modify the program?
Sandage:No, not at all. I think if you have an idea how to do research, it comes naturally. Clearly the intuition is a crucial part of reaching the solution to a problem. I think intuition in science is very important. How that comes about, why some people have intuition and others don't, I think is a matter of training, not native ability. It's a matter of burying yourself in the problem--Feymann used to say, "Thinking like an electron.''
Weart:Referring specifically to that question of long-range, programs, suppose for example there's a strong advance in equipment or detecting ability in the middle of a program. This would have a strong feeling on your program, I suppose?
Sandage:Not necessarily. I'm not necessarily one to change methods that I know will work, because another method is somewhat more efficient. Any way to get the answer is all right with me, as long as the technique doesn’t compromise the data collection. If a tried method works but there’s a better way that is more complicated, that takes a lot more sophistication, takes technicians, I will tend to go the old-fashioned way that I know will reach the answer.
Weart:Does it ever happen, for example, that Kodak stops making an emulsion that you’ve been using, or that a photo-electric detector goes out of service?
Sandage:No. But there are ways around those technical problems; one can always solve every problem that is put in one’s way.
Weart:What’s the attitude been at the observatory towards these very long range programs, in particular toward the heavy demands they make on dark time?
Sandage:I don’t know. The time allocation committee allocates the time. The requests are dealt with as they come in year by year.
Weart:You’re not in the room when they talk about your programs.
Sandage:No, but I know the outcome. Time is given, and that must mean that to that extent the observatory supports the work. It’s a curious place, because the director does not tell any staff member what science he thinks should be doing. There’s hardly any feedback, as to whether the staff believes that the programs that one’s doing are correct or not. But that’s the advantage of this place, also. The good people, left alone, will produce good science, and the bad people, left alone, will produce bad science. Both good and bad science come out of every place.
Weart:I have some specific questions, here, but you may be able to tell me about it better yourself, about what have been the high points for you of the Hubble diagram programs.
Sandage:The crucial thing for Hubble, that was the keystone of the qualitative statement that the universe expands, was the fact that red shifts are correlated with apparent magnitudes. Now all the time that Hubble and Humason were working, the measurement of the apparent magnitudes of standard candles, which were the first-ranked cluster galaxies, was done photographically. When it became possible to measure these objects photoelectrically and increase the sample, then it was out of some sense of duty to improve the statistics on the Hubble diagram. I think I felt that it was my responsibility, being at the observatory, to improve the Hubble diagram by using as many clusters as it was possible to do, first to check the universality around the sky, and then to go as far as the red shift measurements (which) had been done by Minkowski and Humason.
Weart:When you sayr your responsibility, why yours? Wasn't it a responsibility of the observatory’s?
Sandage:Well, the staff was very small in the early days. The nebular department, after Hubble and Baade retired, consisted only of me. So that's the answer.
Weart:I see, OK. You also started H 11 regions, another long program.
Sandage:The extension of the Hubble diagram, the filling out of the Hubble diagram with photoelectric magnitudes and many more clusters than Hubble and Humason had, was a program that was contemplaed as early as 1955. When the availability of the photometer on Palomar was a reality, about 1960, then that project was begun. However, the quasars were foundy and that sidetracked a very large number of people at the observatory from the things that they had been planning. Quasars sidetracked me from 1960 to about 1970. About 1966 or 1967, 1 went back to the photoelectric photometry of a large number of the first-ranked cluster members, galaxies. There are two segments of the observational cosmological studies-one, the improvement of the statistics of the Hubble diagram itself, that's independent of the distance scale; and second, obtaining the Hubble constant, which is the distance scale problem. (Telephone interruption)
Weart:We were talking about the first-ranked ellipticals. Tell me a little more about thaty first, how you came to pick these as standard candles.
Sandage:Hubble and Humason had done that previously, in their papers of 1931 and 1934.
Weart:Then your paper, I guess, with Mayall and Humason.
Sandage:That's right. In that, we re-did the photometry with transfers to photoelectrically determined selected areas. Baum had begun measurements of the faint standards selected areas, and I'd made the photographic transfers to that. That was an interim step to improve the photometry. The number of clusters involved was very small--only 18 in Humason, Mayall & Sanclage, and there were not more than twelve or fifteen in Hubble & Humason--that was a fairly small sample upon which to base the generalization of the entire expansion of the universe, everywhere isotropic and homogeneous in distance. The direct attack on the problem started about 1966, the photoelectric photometry of first-ranked cluster galaxies. A side issue, which turned out to be very interestingy was the reason the first-ranked cluster galaxies had such a small dispersion in absolute magnitude. That we still don't understand. There's two schools of thought. One is, it's just a statistical problem with a luminosity function that steepens toward the bright end; the second is that it's a crucial upper limit caused by some physics in the formation process of collapse out of a Jeans length, and there's a certain upper limit to the mass. Those two possibilities are still debatd; the data that are required are clear--what should be obtained--but the problem isn't solved.
Weart:I'm interested in the evolution of this, the growth of people's concern about evolution, particularly of clusters as clusters. You did some work on the relative brightness of first, second, a third-ranked (galaxies in) clusters. Would you say that there's been an increase of interest or revival of interest in evolution of a cluster as a whole?
Sandage:The ideas as to how clusters form and subsequently evolve have been generated in the last five years by a number of theoreticians. This gives a base upon which to do science, the cosmology of clusters. The field really has begun as a new fieldr with these speculations of an ordinary Friedman expansion but slowed because of the mass contrast, with positive energy, because the clusters appear to be bound. There's a model for the dynamics, which then can be tested observationally. The evolution then of individual galaxies comes from just the interaction times, the crossing times and the collisional crosssections. Those are all calculable items. Many observtional programs suggest themselves now, to test the various hypotheses. So it's a field that really only began ten years ago. But that's; true of many fields in galaxies now. Whereas Hubble and Humason dominated the field, now there are 200 cosmologists around the world, and many new problems have been raised.
Weart:How did it affect you when Beatrice Tinsley and so forth began to challenge the idea of first-ranked cluster galaxies?
Sandage:I don't know what you mean by challenge the idea. It's a fact that the first-ranked cluster galaxies have a small dispersion in absolute magnitude. That's an established fact.
Weart:Well, I guess I should say that but the question of the evolution of ellipticals, and how well understood that was.
Sandage:It's really clear what the evolution of the stellar content of galaxies is; from the knowledge of the H-R diagrams, that was clear in 1962 long before Beatrice Tinsley. The burning down from M67 to 188, and the methods of calculatinllthe change of luminosity, that I believe is a solved problem. It was solved in 1962. The details are clearly capable of being worked out with great precision now, and that's what a number of people are doing. How did it affect me? I don't really know that it affected me at all, because it's a problem where the methods toward a solution and the first solution were no mystery. Of course, I was disappointed that Tinsley believed it to be an idea new to me and that I had not discussed it.
Weart:I'm interested in what you say about the growth in the number of cosmologists, that now there's a number of them. Do you identify yourself as a cosmologist?
Sandage:No, I'm really much more interested in stellar evolutionary processes. I'm an astronomer, in the sense that the calibration processes, the determination of absolute magnitudes of certain types of objects, their use in the astronomical context, structure of the Milky Way galaxy and density gradients, those are the problems that occupy me.
Weart:Are you identified by others as a cosmologist?
Sandage:I don't know.
Weart:What has it meant to have a community of cosmologists, or a number of people who are working in this field, as opposed to just a few? Has it changed the character of people's work?
Sandage:Certainly. The health of the subject depends upon the number of ideas that are put out in a testable form, and the number of tests that are made. I think that cosmology was hardly a viable subject until the last ten or fifteen yearsy when all sorts of viewpoints were brought to it. I think it's an extraordinarily healthy thing. One can't help but gain by any knowledge that anybody brings to a subject.
Weart:Was it exciting to you to have suddenly all these colleagues, so to speak? At one time you were pretty much working by yourself. Now there are a lot of colleagues around.
Sandage:Well, in the problems that I still want to solve, it's still up to large blocks of telescope time over several years. The detailed distances, now, to dwarf galaxies just outside the fringes of the local group--there are no colleagues in that particular area. Certainly, it's much better not to work in a vacuum. The data are useful in many different ways, and I'm very pleased to see any data used.
Weart:I see. How do you think most astronomers regard cosmology? Do they see it the same way they would regard other specialties in astronomy?
Sandage:Maybe in certain aspects of atrophysicsy it has a parallel. But astronomy is an exact science; astrophysics is clearly not exact; and cosmology is the most inexact of astrophysics. But it's remarkable what can be found out, in a hard, strict scientific sense, in the cosmological field. The distance scale problem is a solvable problem, without any speculation or musticism. It hasn't been solved yet, but it can be. That's an astronomoical problem.
Weart:You feel that this is the way that most of your colleagues would regard it?
Sandage:There's a whole spectrum of attitudes of cosmologists also. There are very speculative cosmologists, and very speculative cosmologists who only look for the data. I think it's just like any other branch of science that's rapidly moving.
Weart:OK. Getting back to evolution, I'm thinking of a later period when evolution and cosmology get more and more integrated your work on globular clusters, M3, M13y M15, M92 and so on--which I guess is also a long-range program, you observations began back in 1958--and then you came up with values for helium abundance--I'm interested in the development of your interest in helium abundance, and the development of that problem in general.
Sandage:That really is a side issue. If it's true that certain aspects of the color-magnitude diagrams are sensitive to the hydrogen-helium abundance, then if those aspects are accurately measured, clearly one goes to the helium abundancey since it's a crucial dictum, in certain ways, of looking at production of the Big Bang. Two or three years ago there was a very large excitement, that if you could determine the helium abundancer then you could determine qo. That development came from Peebles and from Bob Wagoner at Stanford and one or two others. Many astronomers were doing everything they could to find the helium -abundance, and this just fell out of the globular cluster work.
Weart:I see. In terms of your own interest in the problem, the development of that? After all, before that some people who were claiming that there were some stars of very low helium abundance and therefore the Big Bang theory had to be changedy that sort of thing. Was that one of the reasons you looked into the helium abundances?
Sandage:No, I think the reason that any emphasis was put on the helium abundances at all was because Robert Christie (Cal Tech) showed there was a way to determine the helium abundance from the nature of the horizontal branch in globular clusters, and that horizontal branch morphology and the precise photometry have been a large aspect of the last fifteen years' work.
Weart:Of course you had the photometry already, so you could just ---
Sandage:--it just fell out.
Weart:I see. Now, your main interest in these I suppose was in the age, for comparison with the Hubble age.
Sandage:That's absolutely right. The age dating of the globular clusters, to me, was a very crucial cornerstone. Because from all the arguments, first made by Baade and then consistent with what we know of the halo, and the aspect of high velocity correlation with high metal abundance, globular clusters are the first primeval stars to form in the galaxy. So that gave a peg (on) when the Jeans instability that resulted in our galaxy took place. If we could age date the globular clusters, we'd have a very strong peg in one of the crucial events in the evolving Friedman cosmology. So that was the strong motivation, from 1955 ony to get the ages of the globular clusters.
Weart:I see. There was a problem, in that the ages came out older than the Hubble time seemed to be falling out.
Sandage:Not really, if you looked at the probable errors. The ages determined by Hoyle's models were 20 to 24 billion (years). It was soon shown that Hoyle's models were upper limits, and the models of Demarque at Chicago and Yaler and Icko Then at Illinois, gave smaller ages, around fourteen or fifteen billion. Those had uncertainties of 30 percent, and the Hubble constant certainly had uncertainties of 30 percent. It was the order of magnitude agreement that was so astounding and so important--not the details to within a billion years, but the order of magnitude agreement.
Weart:So you were never too concerned about that?
Sandage:Not at all.
Weart:How much confidence have you ascribed to your values for the Hubble constant--the 75, and now 55 (km sec -1 Mpc -1).
Sandage:Well, 75 has a very interesting history. That first came in 1957, with just a correction for all the effects that were known at that time to what went into Hubble's determination of 530. Then more concrete evidence, in terms of the distance to the Virgccluster via globular clusters, gave an upper limit of 75, using new data, when was it, about 1968. That was always stated as an upper limit. Then the value of 50 that Tammann and I came to was the mean value from these methods. And you asked, how much confidence? I believe the value is 50.
Weart:Plus or minus?
Sandage:I think, plus or minus perhaps ten. So that's twenty percent. But you know, one's talking now of calibrations that are accurate to one or two tenths of a magnitudey in the RR Lyrae stars period-luminosity relation zero point. In the brightest stars that are resolved in nearby galaxies, that calibration. And no one can guarentee that that's the case. So I wouldn't be surprized if the val ue were not 50.
Weart:All the errors could add up the wrong way or something.
Sandage:They could, yes. It's a problem of waiting and seeing. One very strong new method is the supernovae light curves and velocity curves, which allow a Baade-Wesselink method to get the absolute magnitudes of supernovae.
Weart:Is it because we're finally beginning to get some understanding of supernovae?
Sandage:That's right, of the spectra of supernovae. There's a way to combine the data to get the absolute magnitude of supernovae, and the whole diagram for supernovae is known--that is, the apparent magntiude against the red shift of the supernovae.
Weart:You've been measuring that for a long time?
Sandage:Not I, no. This is Charlie Koall, primarily. Once the absolute magnitude is known, the whole constant comes. The people working on that are David Branch and his group in Oklahoma.
Weart:Has the theoretical understanding of supernovae been important?
Sandage:Not the mechanism that causes the explosion. That's unimportant in the astronomical context. The only thing you have to say is that the envelope takes on the continuum radiation of a black body.
Weart:I see, so it's pretty much observational.
Sandage:That's right, and you can determine the velocity of expansion of the envelope.
Weart:I see. Now, the next thing is qo. Can you tell me how your ideas on q have evolved with time'' i:)
Sandage:First of all, I'm not really sure in my bones that-, idealized Friedman models mean anything.
Weart:Is this because of the question of a cosmological cnstanty or just in general?
Sandage:Just in general. The universe is much more complicated than a uniform model superimposed on it might indicate.
Weart:Still, the universe is either open or closedy even if one abandons the Friedman model?
Sandage:That's what the theory says.
Weart:I see; you’re not so sure. OK. Is this a recent feeling or did you always feel that way.
Sandage:I think it's a lovely poem. It's a closed problemy a problem that has solutions in a closed way: given Ho, qc, you know everything about the geometry of the universe. That's marvelous, if true.
Weart:Given Ho, qo and isotropic, which you check----
Sandage:–and the idealized model. We know in detail that there is no isotropy, no homogeneity. Things are clustered, they’re clumped, they're not spread out in a nice uniform way. So the effect of clumping on local dynamics is crucial to determine. That's where the excitement is going to lie--to see the effect of the velocity perturbations of the very local galaxies, due to Virgo.
Weart:I'm interested in the growth of your interest in these other ways of getting qo, outside the Hubble diagram, the deviation of local Hubble flow, and also the comparison of Ho with the cluster ages. But going back to the beginning, as I understand it, you were looking for qo , simply from the Hubble Diagram.
Weart:Could you describe the evolution of your ideas, beginning with that, and then as the other methods came in?
Sandage:Clearly, even if the observations are perfect, or the errors in the observations are small, and we could extend the Hubble diagram for galaxies to very large red shifts, both of which can be done, technically--then, as everyone has said, the precise knowledge of the evolution is crucial. I'm not sure we'll ever know that well enough to unequivocably say, "dL/dt, the rate of change of the integrated luminosity, is the value.”
Weart:This is your present view. I'm interested how your ideas have evolved.
Sandage:I think that one tried by every means possible to solve a problem. And you must keep yourself continuously in a state of optimism. Otherwise you can't do science. In the 1962 paper, where the effect of the evolution of the H-R diagram was explicity calculated from the light travel time, it was stated that the formal value of qo was probably reduced to a value of 0.2 by the effect of evolution. There was no statement there of uncertainties in the determination finally blocking the way.
Weart:Right, you didn't come out with a very strong statement. In the paper you left it quite open.
Weart:Yes, but one had the feeling that you believed it.
Sandage:Well, the only way I could then proceed the next four or five yers to get photometry of the galaxies that other people had gotten red shifts for would be to pretend like I believed it----because you also have to have faith that all the obstacles that you can foresee will be solved as you approach them. If you are stopped by obstacles you dimly perceive in the future along the path, then you'll never succeed. So one had to have faith that the Stebbins-Whitford effect will be understandable, or understood, in the early days, or that the effect of evolution will be understood. It's clear that that's one way to proceed, on the Hubble diagram. But there are better ways now; with more thought into the problem, people have understood that the local tests are much more powerful.
Weart:At what point did you begin to get interested in these local tests? Was it talking with people, or–?
Sandage:There was an incident which occured, a challenge to the whole concept of a local linear velocity-distance relation raised by two people called Haggerty and Wirtz. They published a paper in the MONTHLY NOTICES, about 1972, saying that for any reasonable densitites, one must expect the Hubble constant to be a function of distance; that locally, you had to have a parabolic starting off, and that only asymptomatically, as you got out beyond six to ten thousand kilometers a second, would the Hubble constant determined have any global meaning. Well, that simply is not true. And in proving that it was not true, Tammann, (Eduardo) Hardy and myself, in a paper which was called something like, "Tests of the Homogeneous Friedman Model" For some reason, (it was) one of the very few times I've felt compelled to answer the critics. The paper took two days to write; it really was another one of those marvelous, exciting two or three days. Tammann and Hardy went down to the library and spent eighteen hours counting the entire Zwicky catalog--in a period of eighteen hours they had the counts done--to show that the classical Hubble distribution, log N (M), something like .6 M, was correct, and the hierarchical universe concept just was not true. In the process of writing thaty somehow the connection was made--in the mind, two things came together--that in the presence of density fluctuations, you must have fluctuations in the Hubble constant, delta H/H, unless qo was very small, unless gravity played no role. So out of that attempt, which lasted probably seven days total, the idea came that local perturbations could measure qo.
Weart:I see. What about the idea of comparing cluster ages with the Hubble time, as a measure of qo.
Sandage:That was explicit in the 1961 paper, in the section on time scales. So that formed a very steadfast goal, to compare those ages.
Weart:I see, not just to compare the two ages, but also to use that as a test of qo
Sandage:Well, the relation between the two ages is a function only of qo.
Weart:I see. Now, by about 1975, you found that a number of these measures agreed that qo was less than a half. As somebody put it, the universe happened one once. Was it at this pointy when you began to put the thing together, that this became a very strong conviction for you?
Sandage:I think that's right, yes. In the 1962 paper, I didn't really believe, I think, the evolutionary correction enough to know how far, or even the sign, of the correction. It could be that elliptical galaxies would get brighter as they aged. It depended on the steepness of the luminosity function fainter than +4. I was not at all convinced. Clearly, I was influenced by the parallel work of Gunn, Schramm, Tinsley and so on. Clearly, the answer is still not known. But the further one looks at the local deviations of the velocity field and finds nothing--and every month, we see a new measure of the quietness of the field--then the conviction continues to grow.
Weart:What you're doing right now, you mean.
Weart:How does that feel in relation to the concept of a heat death of the universe? Do you see an open universe as a heat death Universe?
Sandage:Clearly it's irreversible, in the sense that the nuclear energy that's generated in the stars is not confined to a closed system that will later re-compress itself. So the universe will continue to expand forever, and galaxies will get further and further apart, and things will just die.
Weart:Does this strike you as a--
Sandage:That's the way it is. It doesn't really matter, whether I feel lonely about it or not.
Weart:You must have talked about this with a number of people. What have been other people's reactions to the idea of an open universey if there's growing feeling that the universe is open?
Sandage:Well, I think astronomers think about this problem every day, and they cease to be mystified, in a daily sense. Among the general public, there's a tremendous amount of interest in cosmology, and they all find that just being able to ask the questions and get scientific answers is an interesting part of the problem.
Weart:Speaking of the general public, I want to ask a few questions about that. Maybe first, not quite the general public, but your cosmological work has been very frequently cited in the introduction to the Directors' Reports. Has there been a feeling that your workr particularly the work in cosmology, attracts favorable attention to the observatories?
Sandage:I have no idea what the impact of that singling out, has been. What happened is that the director chooses (among) the projects that are written up for him and given to him as the year's work, and I probably tend to be fuller in my accounts of what I've been doing than some other staff members.
Weart:Have you been asked to give talks, meet with people, write articles?
Sandage:In the early days, yes. To give public lectures or to write for SCIENTIFIC AMERICAN.
Weart:And did you? I know you wrote some for SCIENTIFIC AMERICAN.
Sandage:In the very early days I did. And I did give many public lectures, up until about five years ago.
Weart:Why not after that'?
Sandage:Well, I found out that I would rather not.
Weart:So you just turned down requests.
Weart:Is this a personal thing or it has to do with your work?
Sandage:No, it's absolutely personal. I just feel that I would rather been sitting and reducing data than talking about results that either are not certain or that have been proven.
Weart:Are you concerned about the public's attitude towards astronomy?
Sandage:Oh, sure. I think it's very important that the public know what's going on, and the people like Carl Sagan, I think, are doing a very great service to astronomy. He's very articulate and excites the public in a professional way, a proper way.
Weart:How do you feel the public's view has changed with time? Has the public's view of astronomy or astronomers changed?
Sandage:I think that in the time of Jeans and Eddington and Hubble, there was a great deal of public information and there was a great deal of public information and there was interest in it. The popular books of those people had wide circulation, and I think Hoyle did the same thing to our generation. Astronomy is everybody's second science; it's like archeology, it's the general public's escape. Astronomy sells to the general public, all the time. I think people are just innately interested in it.
Weart:What do you think the value of astronomy is for society? For people?
Sandage:It certainly gets one out of a small view of the situation he's been placed in. It's a spiritual enlarger. We'd be very much different in attitudes if we lived in a cloud-bedecked planet, and there was no astronomy.
Weart:That's interesling to think about.
Sandage:If we didn't know that there is something out there bigger than us, that we are part of, we'd be very much different in world outlook.
Weart:Tell me, have your plans for future work been affected by the big new observatories--the impact of Kitt Peak, Cero Tololo, or for that matter the Carnegie Southern Observatory?
Sandage:Absolutely. The opportunity to do things is now much greater than it was before. The large field capability of the 4-meter telescope on Kitt Peak, and at Cerro Tololo, opens up a whole lot of possibilities. I've used the Kitt Peak 4-meter telescope, on programs that went through the competitive process of being evaluated. Before the Du Pont telescope at Las Campanas was put into operation, it had the only large field (with which it) was possible to do the halo mapping project, for example.
Weart:I see. That's a very different kind of survey in a way ...... I guess it's something between a 48-inch survey and a 200-inch survey.
Sandage:Absolutely, yes. It has about one square degree field, and the 200-inch only has about 5/100 of a square degree, so it has twenty times the area of the 200-inch.
Weart:I see. What has been the impact in the past, or what might be the impact on your field, or space astronomy? Has it had any impact on your work so far?
Sandage:Clearly, when the space telescope gets into operation, the improved resolution will be fundamental for the distance scale problem. But other people will do that. That's again going down a side road, where the problems to be solved from the ground are so enormous that I will choose to do thaty instead of going in a strong team effort with many other people to carry the distance scale problem to the space telescope. That's already being planned by a team of peopler some of whom are at the Hale Observatories.
Weart:I see. Well, we're really near the end of my questions, but I wonder, what other long-term programs are you stanting on now?
Sandage:There's a whole recalibration of the brightest resolved stars in nearby galaxies, as distance indicators. Once that recalibration is done, then we have to apply the technique to the 30 or so resolved dwarf galaxies that have red shifts in the range of 0 to only 300 kilometers a second, very low.
Weart:It's pretty good, to be able to resolve 25 kilometers per second. It's down near the lowest that you can resolve.
Sandage:Well, we know that the field is that quiet. That means that the noise on the pure Friedman Hubble expansion, even at 100 kilometers a second, which is a very small expansion velocity, is only 25 percent. That gives the possibility that if we can determine precise distances to all of those galaxies, both in the direction between us and the Virgo complex, and in the direction between us and the Anti-Virgo complex, then if there is an effect of gravity by the Virgo clumping--and we already know what that density contrast is, it's about a factor of 20 (you look toward the Virgo cluster, and you go through a density contrast of 20, at 1000 kilometers a second, and then it drops down again, at 2000)--
Weart:There's a big density bump out there.
Sandage:In the other direction, it's a trough, going down to about 4/10 of the mean value. And then it climbs again to about 1. So if there's any gravitational effect of the clump, there should be a difference in the velocity-distance relation of these nearby things, toward and away from the Virgo cluster. Now, that would be a direct determination of qo. That will take about ten years to accomplish.
Weart:By the way, has the missing mass problem ever had very much effect on your work?
Sandage:That's one of the problems that I don't understand the answer to. I'm sure it will be solved; it's an obstacle that will be overcome. You put that aside, and don't let that stop you. Yes, it's a problem that may in fact change the whole picture.
Weart:But it's not something that you’ve been trying to—
Sandage:I think most people don't have any leads as to how to proceed. You just have to have faith that somehow, in the course of the advance in the next ten years, something will be found that will solve that problem.
Weart:OK. What about other long-range programs?
Sandage:Well, this is going to take ten years. But in parallel with that, the nature of the galactic halo, the mass of the galactic halo—just by brute force methods, photometric distances to all the stars in various directions—
Weart:—this again takes a large telescope.
Sandage:It takes a large telescope with a large field, and requires photoelectric calibration. We're getting that on Mt. Wilson. Photographic plates measured, and then statistical analysis of the results. So those are the two very large programs, and then the number of small ones will always be there.
Weart:Well, that's all the questions that I have. Anything else that we haven't covered? I'm sure that there are a lot of aspects that I haven't thought to ask you....
Sandage:My life has passed in review. I had nightmares last night.
Of being interrogated? (Laughter)
ASTROPHYSICAL JOURNAL 133 (1961): 355-392
ASTRONOMICAL JOURNAL 61 (1956): 97-162
”Limits on the Local Deviation of the Universe from a Homogeneous Model,” ASTROPHYSICAL JOURNAL 172 (1972): 253-264
Session I | Session II