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Oral History Transcript — Dr. Martin Schwarzschild

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Interview with Dr. Martin Schwarzschild
By Spencer Weart
At Princeton
July 30, 1975

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Martin Schwarzschild; July 30, 1975

ABSTRACT: A preliminary interview with Martin Schwarzschild prior to the Sources for the History of Modern Astrophysics Project. They discuss developments in astrophysics and astronomy and possible people to interview for the project and why.

Transcript

Weart:

Itís understood that this is for the use of the project, and that nobody will make any further use of it without asking your permission. Nobody will quote from any tape we make.

Schwarzschild:

No, and particularly since we are now going to discuss names. Isnít that right? I have to rely on your discretion.

Weart:

Right. What I would like is for you to tell me what you think have been some of the most important developments in the field, letís say since the time that you first became aware of what was happening in the field, and what names you would associate with these developments.

Schwarzschild:

All right. May I, right away, say, there is the solar system, with lots of development in celestial mechanics, and in the physics of the solar system, and lots of theoretical effort regarding the origin of the solar system. That is a field I know nothing about. But a possible good source of advice, sort of as a senior man, just retired, is FRED WHIPPLE, the former director of Smithsonian Astrophysical Observatory. I think heís certainly a person that comes to mind.

Weart:

WHIPPLE?

Schwarzschild:

Right. But I mean, that is a field, both on the celestial mechanics side, and on the physical side, Iím terribly ill acquainted with.

Weart:

Thatís fine, because so am I, and one canít study everything, and frankly Iíve decided that in this study, we wonít cover too much of the solar system except for internal constitution of the sun and so forth, which relates very closely to more general astrophysics.

Schwarzschild:

Now, if we think in terms of objects of study rather than techniques, which may not be the most useful, then in a very rough way, we cover a large part of modern astrophysics if we think in terms of stars, individual stars, stellar systems — our galaxy but also other galaxies, individuals — and then the assembly of galaxies, essentially cosmology. So maybe we should go through these three fields, to which contributions in all the modern fields of techniques, really, are full. I mean, you could also divide it by optical astronomy, space astronomy, radio astronomy and to some degree one should not quite forget that one wants to be sure that there is also a distribution by techniques.

Weart:

Right. We can talk about that a little later, perhaps. Iím sure there are some men whose names are more associated with techniques than with the particular objects, shall we say. I think thatís fine. Why donít you start with the objects, letís say, with the stars. And the period weíre covering, I guess, would be back to about the time you were a graduate student.

Schwarzschild:

All right. Iím speaking without having thought about it before — one of the first big steps in roughly the time period you mention was the determination of the chemical composition of the surface of the sun, by [Henry Norris] RUSSELL, who is not alive. And ever since, a phenomenal development of spectroscopy of stellar atmosphere has occurred. And again thinking in terms of roughly my age group or even a little older, so that they remember — JESSE GREENSTEIN at Cal Tech certainly has experienced in his own lifetime very strongly this development, and has played a magnificent role himself.

Weart:

Heíd be a good person to interview, too, wouldnít he?

Schwarzschild:

Yes. Very lively, and an extremely nice person. Occasionally he has strong opinions. Thatís up to you historians, to try to put into the right light. (Laughter) I mean, one big very important name during that development — and indeed for the whole also, organizationally, for astronomy in this country — is STRUVE. JESSE GREENSTEIN would be a very good source. Connected, but largely driven by different group, is the field into which my own work falls, the stellar interior, which has an observational side, largely through the photometric work of clusters of stars. There, the person who has played, to my mind, the key role is ALAN SANDAGE. Heís not of Cal Tech but of the Hale Observatories. Heís in Pasadena, the Santa Barbara [street] address. But there are many, many more people. SANDAGE is a somewhat more complicated person, but I think a person that has played, historically, a terribly important role. Not only in this field, but also in the cosmological field, which has interactions, so itís very natural that he has been active in both fields. And therefore when we come to the cosmological field, I think it will be very difficult to avoid. I mean it would be terribly natural to consider him on the list. The stellar interior, particularly stellar evolution, has a very large portion purely on the theoretical side. There, in the earliest part, of that period you mentioned, CHANDRASEKHAR would be a person with a very strong historical sense, very much in the English tradition, you know, — an active historical sense.

Weart:

You know, his papers have already been deposited, at University of Chicago.

Schwarzschild:

I mean, he is of a stature that is of an extraordinary kind.

Weart:

It also shows his great historical sense, too, that he should already have made the arrangements and put them there.

Schwarzschild:

I see. He has a much greater sense of science history than the majority.

Weart:

Did you see he had an article recently in BULLETIN OF THE ATOMIC SCIENTISTS, just the last month or so — quite interesting Ė- I think around May or June.

Schwarzschild:

Which one? On which topic?

Weart:

What was it on? Well —

Schwarzschild:

Wasnít there a lecture he gave, an honorary lecture, on patterns of creativity? Shakespeare, Beethoven and Newton?

Weart:

No. Iíve forgotten whether it was about Eddington or about Einstein, I think about Einstein. And cosmology. But Iíve forgotten —

Schwarzschild:

I see. He has worked in very concise periods — drop a topic, start a new one — normally writing a book at the end of every period.

Weart:

I see, just like an Englishman, as you say.

Schwarzschild:

I see. I donít really know the patterns.

Weart:

I think the classical people did do that.

Schwarzschild:

And that sounds, when I mention his name now, very much like his first period, his first book. But I mean, heís a few years older than myself, and in scientific accomplishment far my superior, so as far as he has been active, which was — he sort of switched out of that field somewhere around 1945 or something like that.

Weart:

What other names would you associate with the early, letís say the pre-war work on internal constitution of the stars?

Schwarzschild:

Well, the introduction of nuclear physics into the theory of stellar interior was a fantastic step, and there, the key step was done by BETHE and VON WEIZSACKER, both of whom are alive, BETHE in this country, I think, to get a feeling altogether, not just in that field, but over a much wider field in astronomy, of the growth of interest of physicists in — doing active research in astrophysics — in their formal capacity as physicists, I think BETHE might just be the right man to describe — A former student of him. ED SALPETER, a t the same place — substantially younger than myself, entirely brilliant, and also, I mean, grown up as an official physicist, has become a very major contributor in the field of stellar interiors — one of the main ones.

Weart:

You mean even currently? What period are you talking about?

Schwarzschild:

No, even currently he is very active — but itís not his only field. Personally BETHE entered astrophysics only for a very short spell of essential work. Thereís that one famous paper, that gave the source of the energy for the bulk of the stars. Independent and essentially simultaneously with VON WEIZSACKER, BETHE gave some things more than VON WEIZSACKER. Theyíre always both quoted. And of course that was in 1938, which really was a banner year from that point of view.

Weart:

Because of that?

Schwarzschild:

Because of that. Now, in the early phases, very early phases, I mean, of course, there are the famous names like EDDINGTON and MILNE. I donít know that thatís really — thatís the first call to Ė- thatís a little before the time you want to cover —

Weart:

Yes. Theyíre of interest too, of course.

Schwarzschild:

I mean, you are thinking in terms of international astronomy?

Weart:

Yes. Absolutely.

Schwarzschild:

I think BIERMANN in Germany, Munich — He played quite a role — yes? (interruption)

Weart:

I see we have a whole file drawer labeled ďstellar interiorsĒ here.

Schwarzschild:

My life is so largely in that field.

Weart:

All right, BIERMANN, who else? Perhaps one shouldnít say, who else, but what other major developments and people you associate.

Schwarzschild:

If I may be so forward — may I consider myself as a possible source of description of —?

Weart:

Right Ė-

Schwarzschild:

— particularly the exciting early phases. The roles that, for example, OPIK, an Estonian, played in astronomy — his role and HOYLEís role. And indeed, the question of interviewing HOYLE is — well, his interest in stellar interior, I donít know how large it still looms, but heís obviously one of the —

Weart:

Heís obviously on the list.

Schwarzschild:

An enormously imaginative figure. Whether his own evaluations, I mean, who contributed what, will stand the test of historic study, is quite different. But his influence, if not directly, by way of him being right, but indirectly, by him stirring everybodyís both ambitions and imagination, has been enormous. As an objective source of evaluation, I personally would not put him so high. But as an important factor in driving astrophysics forward, — very tops. On the theoretic side, I was talking about, you know, the interrelation of OPIK, of HOYLE, and of GAMOW and of CHANDRASEKHAR. This whole very exciting period around the time when nuclear physics gave the break, which was I think an unusually interesting period, unusually interesting from the point of view of the interrelation of a relatively small number of people — pretty well those I already mentioned. BENGT STROMGREN, the Dane, and myself, and then a whole slew of the younger generation. Now, I do not know how far in fields like that you want to go.

Weart:

Iím curious, do you feel that the developments letís say since the war have been as important as the developments before the war?

Schwarzschild:

Well, actually, you see, this Ď38 was just about the point where most everybody stopped doing astronomy. So the effects of the Ď38 development really were absorbed into solid research only after an interval. The period to in any case, Ď55, was the first decade, Ď45 to Ď55, to really get nuclear physics into the theory of stellar evolution. And since then, more and more stellar evolution has become a contributor to cosmology, and therefore the work of the younger people since then has taken different turns. Particularly it is starting now to go into the final phases of stellar evolution, where people like ARNETT and others come in, who really is a nuclear physicist, but sort of second generation. He played a very big role. Now, one person whose evenness of judgment and importance of contribution I think probably should be considered is WILLIE FOWLER, also at Cal Tech. Heís a straight nuclear physicist who very early decided to essentially put his life into doing that nuclear physics that astronomers needed. Therefore, his participation was entirely on that part of astrophysics. But also, I mean, the collaboration with the atmospheric people, like JESSE GREENSTEIN has been enormously high, and I think heís terribly balanced in his views.

Weart:

You could give me some other names. Iím very interested in the postwar period. 1955 is 20 years ago now.

Schwarzschild:

Thatís right.

Weart:

And even 1965 is not that recent.

Schwarzschild:

Of the young people in this country, ICKO IBEN in Urbana, and PIERRE DEMARQUE at Yale, I would consider sort of, you know, solid centers. And they have still younger people around them, like PIERRE DEMARQUE has LARSON, and actually ARNETT is with ICKO IBEN. In fact, I think for the field of the stellar interior, that might be enough names. I mean, they themselves —

Weart:

— they will generate more. Schwarzschild — have other feelings. One person that perhaps one should consider in a much wider frame, is CECILIA PAYNE-GAPOSCHKIN, whose most famous work really preceded RUSSELLís in the same field which I mentioned, but who I think has maintained a width of view and a general interest that is not reflected in her own work.

Weart:

I see.

Schwarzschild:

Also I think, although there she might be quite emotionally involved, the whole development of Harvard under SHAPLEY, and then after SHAPLEY under MENZEL and LEO GOLDBERG — I mean, Harvard is an important center.

Weart:

So now weíre to the galaxy, or clusters and the galaxy.

Schwarzschild:

The galaxy. Right. There, the looming figure is JAN OORT in Holland, officially retired, but magnificently active.

Weart:

I see, so he would be a good person to interview.

Schwarzschild:

Oh yes indeed, it would be a shame if you missed him.

Weart:

I must say, his Ė- OORT has been very prominent on everybodyís list so far.

Schwarzschild:

Right at the moment, among living astronomers, few would not likely consider him the record(?) astronomer. His influence has been entirely fantastic, beside his own work. He was here in the spring for two weeks.

Weart:

You know, one thing I must do, when this project has started, I must find out when these people are coming near the New York area, so I donít have to go to Holland or whatever, in order to be able to interview them. Schwar1zschild: One of OORTís sons lives here in Princeton. He is with the Geophysical Fluid Dynamics Laboratory. BRAM OORT. It may be more proper to write to JAN OORT and find out when he makes his next visit.

Weart:

Right, Well, his son — fortunately all this is still some months in the future, so —

Schwarzschild:

But he has been coming here.

Weart:

I see, so he comes fairly frequently.

Schwarzschild:

Once a year or so. If his health keeps well. I mean, heís not that young. But he has been very well, up to now. Now, I preceding him and simultaneous with him, LINDBLAD in Sweden played a big role. He is not alive. His son is now the director of the Stockholm Observatory, PIER LINDBLAD, I think thatís right. Iím not that sure of the first name. Now, going on, in galaxies, there is one field that obviously I am very aware of, even though I have never worked in it, and that is interstellar matter, gases in galaxies, and there I think few would disagree that my own boss, LYMAN SPITZER, has been practically throughout the time, a leader. But one of his students, GEORGE FIELD, who is now the director of Harvard and the Smithsonian [Observatories], you know they are now combined in the directorship, is certainly one of the substantially younger — SPITZER and I are about the same age, and GEORGE FIELD is one of the —

Weart:

— next generation?

Schwarzschild:

Right. And I think would generally be considered as one of the keener, in that field. Now, BART BOK, who just retired, in Tucson, has played an important role in the research on galactic structure. Though possibly not as strong, as a scientist, rather than through his unbounding enthusiasm that he has imparted, and good advice and steering of younger people, has really set quite a record. He was for a while, for ten years, I think, out of the country, after a very big fight in Harvard, a consequence of the succession of SHAPLEY, and was the director of Mount Stromlo Observatory in Australia. But he did come back, and certainly can — well, he must be just a little younger than OORT, and also got his PHD in — I think so — in any case, most of his education in Holland. Now, quite a bit of both stellar research, when it comes to neutron stars, pulsars and also galactic research is in the X-ray region. And there, one of the original pioneers, leading up to these particular, most exciting topics that have come out of it, is HERB FRIEDMAN, but that is again a representative in my age group. He is head of the Naval Research Laboratory, and has played major roles in the space program. He was one of the three or so original pioneers who visited to put their livesí energy, into rocket work as early as Ė what were these German rockets —

Weart:

V-2ís?

Schwarzschild:

V-2ís, right. He really — I mean, if you want the beginning of the history of off-the-ground, space astronomy, HERB FRIEDMAN is one of the outstanding, very early pioneers. I think one of the names that one should also very seriously consider from a variety of points of view is LEO GOLDBERG, who is the director of Kitt Peak National Observatory, and who has contributed both to questions of stellar atmospheres, enormously — he would be, I would consider, by far the best source on the growth of national observatories, the phenomenon of national observatories, which is certainly, as an organizational phenomenon, terribly important.

Weart:

Yes, one of the things I wanted to ask you about was in fact exactly that.

Schwarzschild:

So, you see, he was in Michigan under — not under MCMATH, actually LEO was the director of the university observatory, and MCMATH had his private solar observatory. But MCMATH was a driver towards the national observatory, and Leo therefore was involved. MCMATH was in some sense very unrealistic. He knew his way around Washington magnificently, but he didnít know his way around the scientists all that well, and therefore LEO played, from the very very beginning, in the first year, sort of a behind the scenes very important role.

Weart:

In the scientific community?

Schwarzschild:

Well, and as an advisor to MCMATH in his various, — he could tell much more. And I think he will not blow his own horn improperly I think one can tape LEO GOLDBERG, on that score, very importantly — By the way, I did not mention solar astrophysics, which normally is segregated from the stars, because on the sun, you can study not just the surface or the interior, but you can also see the hazy outer part.

Weart:

Donít tell me, you know, I spent three years doing that.

Schwarzschild:

Iím embarrassed, I should have remembered. In that field, well, you can pick your own candidates, but you can agree that LEO GOLDBERG Is —

Weart:

— yes —

Schwarzschild:

— is one of the key men. On the instrumental side, though again in the older group, is JACK EVANS, the just retired head of Sac Peak [Sacramento Peak Observatory]Ö

Weart:

— when did he retire?

Schwarzschild:

He retired. His age just came. The best younger man now at Sac Peak, and I think he is now the director, in fact he certainly is, is DICK DUNN. Now, he was —

Weart:

— a great instrumental man.

Schwarzschild:

A very great instrumental man, and I am not clear what sense of historic proportions he has, but as a figure he is —

Weart:

Itís hard for me to evaluate — again, you know, Iím not old enough to have much of a sense of where the people that I know get placed — Iím trying to stay away a bit from solar physics especially because Iím too close to it. Other people can concern themselves with thatÖ but, back to galaxies now, galaxies and beyond, weíve not quite finished with that.

Schwarzschild:

Right. The study of the galaxies, of course — HUBBLE has played an enormous role. Heís not alive.

Weart:

How do I spell it?

Schwarzschild:

H-U —

Weart:

Oh, HUBBLE, right.

Schwarzschild:

Sorry, itís my pronunciation probably, and your spelling.

Weart:

I keep thinking of HERBIG, I donít know why. HUBBLE.

Schwarzschild:

HERBIG, by the way, would be a fascinating man, when it comes to interstellar matter, on the observational side. How even and broadminded is another question, but as a person, very very marvelous.

Weart:

HUBBLE clearly. Actually HUBBLE is one of the very few people that thereís been some historical work done on already. Heís far enough back, and people have started to do it.

Schwarzschild:

If you want my personal opinion, I think that his fame has been built up without any rera1%.relation to his actual contribution. I think he sort of fell into place, as —

Weart:

He found a constant — where his name, that sort of thing —

Schwarzschild:

Yes. I donít mind that that constant was named after him, but I mean, that doesnít, thatís no measure —

Weart:

Right.

Schwarzschild:

— for the contribution. I think that HUBBLE is one of the, to my mind, I suspect, one of the cases where the circumstances have made him a scientific hero. And, if I may be brutal enough to your profession, to say that I think it will not be corrected, that it has gone too far. I believe that basically the suspicion, but one could really check that, obviously, of an expanding universe existed before him. After all, SLIPHER had found the preponderance of the red shifts, isnít that right, before HUBBLE. I would not be one bit surprised if HALE had not clearly in his mind, for the 100 inch, that this problem should be there, and that HUBBLE as a youngster, energetic, strong — he was really an athlete, is that not right, fell into it. The spectroscopic observations, the radial velocity measurements, to the best of my understanding, but I may be very prejudiced on that point, would never have happened with any reliability if it hadnít been for HUMASON. Who started astronomy as a mule driver, when he was a boy of 14 or something like that, driving up the parts of the 100 inch, up to the mountain, and slowly got himself persuaded to be accepted, first as a janitor, then as a night assistant, and so on, and then deputy director.

He had never an education. And in that sense he never was an astronomer, but he was a magnificent instrument user, of course not an instrument designer, and essentially the observational material, at least the spectroscopic observational material that made the red shift curve, was based on HUMASON. HUBBLEíS plates, I mean plates that HUBBLE took himself and developed himself, were as scratched and dirty as they came — I remember discussions with the photographer of the observatory. He said whenever he had to prepare a plate of HUBBLEís for publication, he had to practically repaint it. Thatís a little excessive — And the star counts of HUBBLEís were ferociously poor, and HUBBLE had absolutely no concept how wrong they were — even though he could have estimated it. Indeed, I remember my teacher in Gottingen, HECHMANN in the field, telling me how completely unwarranted HUBBLEís deductions were on the basis of the possible accuracy that HUBBLE could achieve at that time, and did achieve. Now we know theyíre completely wrong. And essentially, after the famous papers — I think they were in 1935 and Ď36 — one, HUBBLE alone, if I remember right, and one HUBBLE and TOLMAN — HUBBLE essentially stopped doing science and waited for the 200 inch. This is my version of HUBBLE. The famous hero that I believe is an historic hero, not a real hero.

Weart:

Tell me who some of the real heroes were, or half heroes.

Schwarzschild:

I think there, at the beginning of the expanding universe concept, thereís SLIPHER, VICTOR SLIPHER, that is, observations — but I mean, there is something that I feel a little irresponsible about, because I think one can check all that.

Weart:

What you are giving is clues to things that should be checked.

Schwarzschild:

Thatís right, so donít take anything —

Weart:

— no ,no, this is exactly what I want. I want clues as to where to look —

Schwarzschild:

Right. And then DE SITTER, and I donít know on what basis, got convinced that the universe, at some time point, and one has to find out whenÖ

Weart:

Let me shift this now. — discuss these things, quite early on, DE SITTER. Well, he has the solution to Einsteinís equations.

Schwarzschild:

Right.

Weart:

Now, in the post-Hubble period — or from the twenties forward, letís say.

Schwarzschild:

Well, the first big — well, no, HUBBLEíS key work was about Ď36 or so. If I remember. I think, then, the key role went to BAADE, a German-educated astronomer who worked at Mount Wilson as you know. He is also an important figure in the structure of galaxies, and he invented stellar populations, which were both for the studies of stars and for the studies of galaxies very important. And that led him to the first of the major corrections factors, to HUBBLEís expansion. That was what you might call an error that SHAPLEY made, you know, using the variable stars, the variable stars of the two populations, Cepheids, so one factor of two came in then. That happened immediately after the war, if I remember, after World War II. And then, a whole number of further corrections were by and by found, — like HUBBLEíS mistaking H-II regions for stars, and all sorts of things like that. Some of them — I donít know too well how much of that BAADE did and how much of that SANDAGE did, but I think SANDAGE is very attached to both HUBBLE and BAADE, and that would give as fair a picture of both. The only thing is, I think that SANDAGE is a good Mount Wilson man in his assessment of SHAPLEYís work, in all of these fields.

Weart:

The Mount Wilson people have a different viewpoint on these things?

Schwarzschild:

There was an enormous fight, between — SHAPLEY you know, as a young man, did his really great work at Mount Wilson and as stubborn and was as stubborn and cocky as bright youngsters come, and had a fight and was just kicked out.

Weart:

The Mount Wilson people just in general have kept this attitude towards him?

Schwarzschild:

Oh yes. But HUBBLE the worst. I have suffered under a couple of sermons from HUBBLE, ranting in the most unreasonable way against SHAPLEY that you can imagine. Now, SHAPLEY was no angel, either. I mean, SHAPLEY was sufficiently unreasonable, in exactly that same emotional fight. He would try his best to keep his young people from working summers in Mount Wilson. So, unreasonableness was reasonably equally split. And I have no reason to be anti- SHAPLEY. SHAPLEY brought me to this country. Thatís a very very big reason to be grateful to him. But there were very, very hard feelings. I mean, SHAPLEY obviously is a figure, and BOK would be the best, I mean the most congenial source, to get a — I mean, if you want the most positive description of the contribution of SHAPLEY, BOK would be the right person. But the continuation really fell to BAADE, and then BAADE and SANDAGE. Though, one person, not exactly young, but ďyoungerĒ in that way, under SANDAGE, in age group, that I would take extremely seriously is MAARTEN SCHMIDT.

Weart:

Weíre talking now about people who are really important people today, whoíre very active.

Schwarzschild:

SANDAGE and SCHMIDT would clearly be considered very important.

Weart:

What other people would you consider to be very important today, letís say for this last ten or fifteen years, in this field of galaxies, cosmology?

Schwarzschild:

Itís always very dangerous, you know, to try to just think, on the hoof.

Weart:

I understand that. A few names, bubble to the top, and thereís a great mass of others.

Schwarzschild:

Yes. Well, in the Netherlands, I think VAN DE HULST, who was the one who theoretically invented the 21 centimeter line, but has ever since been a very, very influential man; and possibly BLAAUW.

Weart:

Heís in the Netherlands, also.

Schwarzschild:

Right. I mean, they all —

Weart:

— itís curious, isnít it, that the Netherlands has played such a big role in the 20th century.

Schwarzschild:

I think most people would agree that probably it was KAPTEYN, well before your time span, who was in some mysterious way the driving force, far beyond his own research. Then when it finally comes to cosmology, and it sort of shades over, well, the discovery of quasars is obviously one of the key points, and that is something I think that both SCHMIDT and SANDAGE could be much clearer about, and theyíre radio astronomy, of course. That invented the quasars, I mean, originally, it was quasi-stellar radio sources. The discovery came in radio astronomy, and the contribution has stood.

Weart:

I suppose they wouldnít have found them still if it hadnít been for radio.

Schwarzschild:

I wouldnít be at all surprised. Thatís always very hard to say, but it sure came from there. Just like the pulsars. And the whole 21 centimeter development, is it not right, for the galaxies, and for the study of other galaxies, has been enormous. So with regard to cosmology, there is what I would call classical cosmology, HUBBLE type cosmology, that is all that HUBBLE wanted to do, has been done better, but there again, SANDAGE and SCHMIDT are I think much the better sources of further information. The quasars did not come out of it, as a matter of fact, as promising, from that point of view. They are still fantastically important, but since they donít seem to be very good standard candles, itís not —

Weart:

— not so far, anyway.

Schwarzschild:

Right. Right. But then, in cosmology, I think an awful lot has happened from new directions, and one of the sort of problems that most clearly show this new direction is the question of the origin of the heavy elements, the fact that the oldest stars in our galaxy seem to be very low in heavy elements, isnít that right. That is clearly connected with cosmology, and by and by, has been tied more and more strongly to the Big Bang theory — where you cannot make your heavy elements, if purely Einsteinian Big Bang is the right theory. And then, our present attempts of determining the average helium content, which is produced mainly in the Big Bang, is another part of that. And there again, on the question of the chemical composition of old stars, JESSE GREENSTEIN can carry you down the history infinitely better than I.

Weart:

Who would you say were the most important people in this, and also the search for helium and so forth? Would you say people like GREENSTIN?

Schwarzschild:

I think GREENSTEIN has played sort of a central figure. Actually the first papers on an attempt at finding the difference between, in chemical composition, between population I and population II was made by my wife and myself. We couldnít — GREENSTEIN wasnít not yet at Cal Tech. And we couldnít persuade the Old Guard of spectroscopists, the upper floor in the Mount Wilson Observatory, I mean offices Ė- where the spectroscopists were was in practically no contact with the lower floor, where cosmology was done.

Weart:

Is that so?

Schwarzschild:

By doing a couple of papers — they were obviously not, you know, the best professional work, because Iím not, and neither is my wife, expert in this kind of work. We at least got the signs straight, and then real good people, like JESSE, very fast entered the field, JESSE really has been sort of the inspirator, even though I mean, there are many younger men.

Weart:

I really must talk with him.

Schwarzschild:

I think so. Now, I think, on the cosmological side, one should — one should also include some of the new relativists. Now, Iím leaving out the astronomical (and that is mostly solar system) use to test general relativity. Whether you call it astronomy of physics, doesnít make any difference, but itís done with astronomical bodies — you know IRV SHAPIRO, isnít that right — is the figure that I would ask, even though heís very young, heís so outstanding, such a leader in that field. But if you speak about cosmology, as a whole, I think there are two relatively young people, PEEBLES here, and KIP THORNE at Cal Tech. That doesnít say that they have, you know, necessarily done the main contributions, but they are marvelous synthesizers, isnít that right? And both very friendly and very fair. So I think as sources, they would be very good. BOB DICKE has produced, with one of his colleagues, the BRANS-DICKE theory, which has I think played a terrifically important role, just to have an alternative. There was for a while the steady-state theory of HOYLE and his group as an alternative. That seems now to have run into a number of difficulties, which I wouldnít say disprove it, but itís not considered, you know, all that active an alternative. But DICKE has I think taken up that role, and you find — well, I listened at the celebration for CHANDRASEKHAR to a number of talks, on general relativity, because thatís Chandraís present — and there, somehow or other, even though nobody quite wants to believe the BRANS-DICKE theory, indeed, most of the tests have gone against BRANS-DICKE and for EINSTEIN. Itís a very neat testing store. I mean, if you have no alternatives you flounder how to prove anything.

Weart:

Itís an old problem in the philosophy of science, isnít it?

Schwarzschild:

Yes. That is so. So I donít want to not advise BOB DICKE, except I think that PEEBLES and KIP THORNE might be — you know, they are next generation, they are full of prejudices and both very active.

Weart:

DICKE might have things to say about other fields of physics also. Heís been involved in a lot of other things.

Schwarzschild:

Yes. And his impact on astronomy, I mean, itís quite unclear to me, that either PEEBLES or KIP THORNE would be, what they are, if it wasnít Ė- it took JOHNNY WHEELER in part but it also took DICKE very much.

Weart:

Right. Well, letís see, weíve gone on to the — when you went to the BRANS-DICKE THEORY, youíre about the extreme limit.

Schwarzschild:

Right. Now, on the experimental side and on the organizational side perhaps —

Weart:

— my next two questions exactly.

Schwarzschild:

By the way, Iíve forgotten that it comes up on the experimental side, when it comes to X-ray astronomy, I mentioned the pioneer, HERB FRIEDMAN. The outstanding younger one is GIACCONI.

Weart:

Right, I was already writing it down.

Schwarzschild:

Right. Good.

Weart:

You know, I have to go and catch a train and I have to leave here in about 15 minutes, so letís leave aside all the radio astronomy people because I think I have their names. I think I have a pretty good list of their names already. So why donít we talk about some of these other instrumental fields that are not perhaps so famous.

Schwarzschild:

You probably have answers to —

Weart:

— to what?

Schwarzschild:

I mean space astronomy.

Weart:

Yes. Why donít we talk about instrumental developments since the twenties, in optical astronomy? Thatís something which is perhaps not so famous, not so easy to find.

Schwarzschild:

Right. Well, there I would say, on the ground, the biggest steps have been, again, I speak of the SCHMIDT camera, obviously, the coming of the — after the 100 inch, the 200 inch — but I mean, that is more of the same, except in a very decisive matter, but itís not fundamental —

Weart:

— Thatís an organizational development rather than an —

Schwarzschild:

— not a really new technical Ė- but how to get the 200 to move smoothly was a real feat. But I think the Schmidt camera has played an enormous role, not only, as you know, like the 48 inch of course, but as cameras in spectrographs. The ruling of gratings, since the twenties, I mean, it was really only after World War II, in effect, that high dispersion grating spectrographs really became a general tool.

Weart:

I see. You mean, aside from one or two here and there.

Schwarzschild:

Well, I mean, you know, really high definition, first class gratings, that really had the spectral resolution of modern Coudes, the first one was at the 100 inch, at Mount Wilson — as long as DUNHAM, the builder, was there, it was practically impossible to use it, because he changed it every month. So in fact, only —

Weart:

DUNHAM?

Schwarzschild:

DUNHAM, right. Iím exaggerating a little, but it was one of these cases where you had to kick the builder out, before you could use his instruments. And through the war and other interests, DUNHAM did leave. So I think, I would not underestimate — the idea is much older, but the art —

Weart:

Were there any particular people or organizations that are responsible for this?

Schwarzschild:

No — I think that — DUNHAM and the then director, ADAMS, and of course, itís probably unfair, there are probably more names that I should add in all these fields.

Weart:

Is there any company that was particularly associated with instrumental advances, building of instruments of one sort or another?

Schwarzschild:

In these fields, none that I am aware of. Of course by now, BAUSCH AND LOMB is the source of high grade —

Weart:

— right.

Schwarzschild:

The introduction of photoelectric meant a switch of precision photometry from the photographic plate to photoelectric means, that falls in that area. In that field, STEBBINS was the leader. He is not alive. His oldest student, WHITFORD, who is alive, and retired as director but not as astronomer at Santa Cruz, would know the early beginnings of it, and after World War II, the 1P21 [Designation of first commercial photomultiplier] isnít that right.

Weart:

The good old 1P21 Ė-

Schwarzschild:

— when there were only very few people who did photoelectric photometry before the war, and then the 1P21 suddenly made an astronomer-proof instrument. And now the development into photoelectric image tubes, isnít that right — well, itís just starting to work. But I think that is a — the switch from the photographic plate to the photoelectric device, I first think of BOWEN, isnít that right, and the 1P21, and now, the two-dimensional array type of tube is a very fundamental development. I have a very hard time knowing who any particular person involved. The 1P21, I forget, was it RCA or Westinghouse or whoever, I think, developed the first one an industrial development, isnít that right, pushed by the war.

Weart:

And the postwar development has been pretty largely industrial also, hasnít it?

Schwarzschild:

Not originally. Astronomers had the greatest need. But then the military took over, and other applications I think only followed the military.

Weart:

Are there any names or any companies that you would particularly associate with the postwar development of these tubes?

Schwarzschild:

The single tubes, I donít know, except for the development of the 1P21, whoever did that. Now, the image tubes, as they come into play, thereís industrial competition, but again, very largely, I think that astronomical need has been one of the major stimuli to that. The military, except in the infrared, has been following. In the infra-red, the military has been — for very obvious reasons — But I donít think that one can under-estimate as another instrumental development, the electronic computer. I mean, I donít know whether you call it an instrument, but it has revolutionized the possibility of using telescopes. I mean, itís unbelievable, how much more effective modern telescopes operate, now, how simply the use of the online computer speeds up the acquisition of data.

Weart:

Simply to be able to point it at a star —

Schwarzschild:

The speed of acquisition, the speed of getting the data off the instrument — I mean, efficiency has easily gained by a factor of two.

Weart:

And when did this begin to happen? In terms at use the telescope?

Schwarzschild:

Sinfully late. It could have started very fast after the end of World War II, and the astronomers were very slow. I would say, it really started becoming active less than ten years ago. But there, the directors of the big observatories can give you the times much better than I. But I remember still, in the early fifties, arguing, as a visitor astronomer, and that had as you know no authority and therefore I could speak very freely, arguing with BOWEN, who was then the director of the Hale Observatories that he ought to hire an electronics technician — one electronics technician.

Weart:

One electronics technician. My goodness.

Schwarzschild:

Didnít work. Inertia for a long while — it was very long. The Europeans have been better in auxiliary instruments, and very much poorer in major instruments.

Weart:

Speaking of BOWEN, you also mentioned organization, and organizational people. Who do you think or what do you think were the important developments there?

Schwarzschild:

Well, the national observatories are the real new feature. And there it is between HEESCHEN and LEO GOLDBERG.

Weart:

Who?

Schwarzschild:

HEESCHEN, the radio astronomer who was the head of the National Radio Observatory.

Weart:

Oh, right.

Schwarzschild:

Regarding the organization of the Hale Observatories, that is a story that in the moment is in such an uproar, that at present to get a proper assessment is very tough.

Weart:

It may not be the time to ask about it.

Schwarzschild:

Right. I mean, that was a peculiar situation. Isnít that right, with the — I mean, everything was normal, as long as it was Carnegie, up to the 100 inch. Then, when Hale in his last healthy yeas, succeeded in getting the funds for the 200 inch, Cal Tech got funds for staffing the 200 inch, and those funds were invested in a way that they disappeared in the Depression. So there was the 200 inch, owned by Cal Tech, and no staff. And then a contract between the two institutions, Carnegie and Cal Tech, was made, which for those circumstances, was right. I think. And worked for a while, very well, and has gotten more and more impossible, in my judgment. That was an interesting collaboration between two institutions — by the way, in many ways, it was the old Mount Wilson Observatory who invented the idea of guest astronomers in a real important way, which has become a keystone. The physicists were rather later, with that idea.

Weart:

Astronomers were always ahead because they had the bigger instruments and so forth.

Schwarzschild:

The bigger and fewer instruments, thatís right. And there is one other interesting example of an organizational type, and that was YERKES in Texas, and their collaboration with the MacDonald Observatory. That was a similar collaboration type. But Iím not sure whether that is as important as the idea of outsiders being given time to exploit great instruments, for which Mount Wilson really has the — But organizationally, the most important is the coming of the national observatories, and I donít want to say whether everything is good about that.

Weart:

No, but — Well, thereís a lot more questions I could ask you, but I must catch a train, because theyíre not too frequent.