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Oral History Transcript — Dr. Maarten Schmidt

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Interview with Dr. Maarten Schmidt
By Dr. Spencer Weart
At CalTech
October 24, 1977

open tab View abstract

Edwin E. Salpeter; October 24, 1977

ABSTRACT: Early years in Holland and attraction to astronomy; education at Groningen (1946-1949) and at Leiden under Oort (1949-1956); life at Hale Observatories and Caltech (1956-1977). Research on comets, radio map of galaxy, distribution of mass and rate of star formation in galaxy, red shifts of galaxies and quasars, nature of quasars. Views on cosmology, use of 200-inch telescope, and social relations of astronomy.

Transcript

Schmidt:

I think it would be helpful to know something about the format....?

Weart:

Oh, we're simply going to go through your career. There will be periods when we're talking about the scientific and technical parts of it. Then when we finish with a batch of that, we'll go back and catch up on some of the social parts, about institutions you've been in. So we'll alternate between those two aspects.

Schmidt:

Right

Weart:

Unless they get intertangled, which is fine also. Sometimes you can't exactly separate the two. Well, the first thing I wanted to ask you — I'm quite interested in the whole scene in the Netherlands, and why it has produced so many good astronomers. Also, in general, we're just interested in how people get into science in the first place. I know that you were born in Groningen in 1929, but I don't know anything else about your family — who your parents were, what did they do?

Schmidt:

My father was a government accountant. They came from a small village in what is called North Holland, north of Amsterdam. My paternal grandfather was a house painter. My mother's father was a farmer. My father went through the normal career of an accountant and ended up, for a few years, as a top Dutch government accountant; he became inspector general for the Dutch whatever, something to do with the Department of Finance. He liked numbers. I probably inherited it from him. He had one brother, an uncle of mine, who is an amateur astronomer and that helped shape my career, of course. That happened mostly in the war, that I got interested in astronomy. It was dark during the war; everything was blacked out. I became interested in lenses. I must have been about 12 years old. My uncle showed me how, with two lenses, you could make a small telescope.

Weart:

Your uncle was an amateur astronomer?

Schmidt:

An amateur astronomer, and a pharmacist. That was his profession. He showed me how, with two lenses, you could make a small telescope, and then when I came back from summer vacation that I stayed with him, in '42 I think, I wrote him. I wrote him, what could I do with the thing? He said, 'Why don't you see whether you can split that — then, get a double star?' which forced me to go to the library to look up some books to find a double star. Which got me into a astronomy, as a sort of pastime.

Weart:

By the way, did you have brothers and sisters?

Schmidt:

One brother, who is not in hard science at all. He's in the Dutch language.

Weart:

An older brother?

Schmidt:

Yes, four years older.

Weart:

Were there other influences? For example, were they any particular science books you read that influenced you, or other influences on orienting you towards science?

Schmidt:

No, it probably went that way I've just described. I was first interested as a young boy in chemistry, and I had a little chem lab at home. Then I became interested in these lenses, and through the lenses, and my uncle, into astronomy. And only then, I would think, I started to read books that influenced me further. I seem to remember a book by Flammarion which is very thick, and literally very colorful in its descriptions. I've never seen description of single or double stars the way Flammarion could do it.

Weart:

That book seems to have influenced a lot of people.

Schmidt:

I wouldn't be surprised.

Weart:

I know the one you mean. What about your schooling? Was it done partly at home or mostly in the regular schools?

Schmidt:

Mostly regular schools, I would say. In the secondary school there was a subject called cosmography which I probably had in the senior year of the secondary school, 'which is like high school here) — perhaps at the senior end of junior year, I don't remember. It was taught by the director of the school, and cosmography was a funny field to teach because it was mostly spherical trigonometry. That seemed more important, these angles, than anything happening out in the universe. So we heard nothing about the galaxy, rotation of the galaxy or so. It was much more important to find out at what time something was rising, or what altitude above the horizon, silly things like that. Amazing.

Weart:

Did you find it interesting?

Schmidt:

Oh, of course I was rather good at it because I understood all those things from having read all those books. I was well beyond that. I once in a while sort of managed to upstage the director, especially when he once went through the exercise of placing the observer on the North Pole and then drew a hemisphere, as you usually do in this business, in which the North was still at the left and the South at the right. He didn't take too well to it, that I pointed out that every direction was South.

But then he took revenge on me, because on the 9th of July, 1945, there was a partial eclipse of the sun for which I prepared myself very well. We took lots of pictures and determined the beginning and end of the eclipse with great accuracy. It was in the afternoon — it was just after the end of the war, but things were far from normal in Holland yet. School was only in the morning.

And I did this — although we did separate observations — with Jan Borgman who is now a Dutch astronomer at Groningen. I asked permission to stay home that morning in order to prepare these observations and the director would not go for it. The thing was in the early afternoon so we had to rush.

Weart:

Tell me, did you have any choice as to which type of high school you would go to?

Schmidt:

Yes. I could have gone to the gymnasium which emphasized Latin and Greek, of course, or to a school which I can't translate the name of.

Weart:

Sort of a realschule?

Schmidt:

Yes, sort of. Hoch burgerskol, which is a nonsensical name because it means upper civil or citizens' school which is nonsense of course when it's translated. But it had no Latin, no Greek, and it emphasized the sciences and chemistry.

Weart:

I see. And what determined the choice of going to that type of school rather than to the gymnasium, the classical school?

Schmidt:

Just my inclination, at the age of about 12 when I entered that school. One could choose freely.

Weart:

I see. Didn't your parents have a role to play?

Schmidt:

Of course. But they left it mostly to ourselves although there was some pushing, of course. The gymnasium was considered a higher level school. It also took a year longer. My brother took it, of course, with his language interests. I took the other one, which I don't really regret.

Weart:

What sort of feeling did people have about science, in your early home life, during this period?

Schmidt:

That was rather positive I would say. That is, it was a respected field and scientists were highly respected. However, there was a belief that as a career, at least financially as a career, it was not particularly promising. But I think, in fact, in those days, in the early thirties, that scientists were probably low paid.

Weart:

Certainly compared to some of the other possibilities that would have been open, yes.

Schmidt:

Yes. Well, to become a doctor or lawyer obviously, always has been, I guess —

Weart:

But was there any particular feeling about astronomy, as separate from the other sciences?

Schmidt:

Yes. When — it must have been, I think, about at the age of 15 or 16 or so. I did enter the university at the age of 16 which partly was a little bit fluky; it had to do with my birth date which was the 28th of December and I think I was on the wrong side, by a month or so, but actually was accepted in the first grade a year earlier then the rules would allow. I either would have been late or a year early. Then, with this secondary school that was five years only, I ended up as a college student at the age of 16 'and 3/4 of course). Now, let me see when that was. I think it must have been soon after the end of the war, when I indicated I would like to go into astronomy as a career, that my father got rather worried — I think for good reasons. By that time, the pay scale probably had improved, of say, people like astronomers, or it was about to improve. Astronomers were not treated differently, you know, from other academic types within the universities. But there were at that time only 14 positions in Holland in astronomy. You could just look at those people and see that none of them was going to go away, or die for a while, to realize that it was a very tight situation. So I remember that at a very early stage, at my father's request, we met with Adriaan Blaauw. He was fairly young at that time. He'd gotten his PhD in '46 and I think we probably talked to him around that same time, perhaps even before that time. But he sort of managed to put my father at ease about my going in this direction.

Weart:

What was it that attracted you to astronomy do you suppose? What was the feeling about astronomy?

Schmidt:

I don't know. It must be partly the same attraction, of course, that makes it so liked by the public, that makes so many amateurs in the field — some instinctive attraction to knowing about one's environment and where you are in the universe. But these are all words that I think are terribly inadequate to describe something pretty deep. I don't know, I can't say. It's — well, as I said, some curiosity about the overall thing.

Weart:

By the way, did you have any formal religious training when you were a child?

Schmidt:

Hardly at all. One winter, I think, I went to catechism or Sunday School. It was on a Tuesday night or so and that was all.

Weart:

I see. Was this Protestant?

Schmidt:

Yes.

Weart:

What were the feelings about religion in your family?

Schmidt:

Rather light. It was never emphasized. We certainly were not a religious family although my father went to church once in a while. I think my mother hardly ever went and I never did either.

Weart:

Another question about these influences. Of course, this was during the war. Other than the dark skies, did the war leave any important impressions on you?

Schmidt:

In connection with my career?

Weart:

Well, yes, in connection with your subsequent career?

Schmidt:

No, not very much somehow. Of course it must have to some degree because youngsters of that age — and I was, you know, between 13 and 15 or so during the second half of the war — would usually be engaged in their school work rather vigorously and instead, in early or late '44, the schools closed because of the emergency situation that developed when the Battle of Arnheim took place and the railroad workers went on strike and stayed on strike till the end of the war.

Weart:

You were in the area that was affected by the famine and all that?

Schmidt:

No, I was in the northeastern part of Holland, Groningen, whereas the west was much worse affected. We did reasonably well compared to them. Both Borgman an I managed to do all sorts of things, like grinding mirrors and building small telescopes — which was really very odd in a sense, because materially the country was practically depleted of everything. There was no coffee, no tea, no meat, no sugar, I mean, anything you want to mention. And yet we managed, from scarce materials, to build small telescopes.

Weart:

I see. Oh, another question about this — simply because I ask this question of every scientist — what was your reaction when you heard about Hiroshima?

Schmidt:

I saw immediately, I think, it's importance. I remember where I was. I was with my grandparents, north of Amsterdam, north Holland and I saw it in a newspaper. I saw immediately what it meant in terms of potential possibilities in the negative sense. But I certainly didn't manage to explain it to my father or other relatives.

Weart:

Did it have any effect on you? At this time, you were already seeing yourself as a potential scientist and so forth. Or did that seem irrelevant?

Schmidt:

No, that was irrelevant. The discussions as to the responsibilities of science and scientists, relative to society, and things like that, didn't penetrate so rapidly. I was only 15 years old at that time.

Weart:

You were, at any rate, not planning to be a nuclear physicist.

Schmidt:

No. So that didn't enter my mind. That only came quite a few years later.

Weart:

OK — to get back to your going to Leiden — did you expect at that early age to go to college or did this come about fully while you were at the school and so forth?

Schmidt:

No, it was sort of expected.

Weart:

In your family.

Schmidt:

Yes.

Weart:

What was your parents' education? Had they been to the university?

Schmidt:

My mother had no formal education after high school. My father had been to a special school near Rotterdam, some type of specialized academy that had to do with finance and things like that.

Weart:

I see. But they expected you to go to one of the big universities.

Schmidt:

Yes, if I wanted to. They certainly encouraged it.

Weart:

How did you choose to go to Leiden?

Schmidt:

I actually went first to Groningen where I got my BS or the equivalent of that.

Weart:

Oh, is that so? I didn't realize that.

Schmidt:

There's a funny hiatus or uncertainty in my mind. I'm so used now to college taking four years that when I look at my own vita, and I see that I went in 1946 and I graduated in 1949, I can't quite understand it. But it is right. And I know I did nothing abnormal, so —.

Weart:

It was the standard curriculum?

Schmidt:

Reasonably standard because there is no solid standard. It's very different from what we have here. You can take your exams almost any time after you've done your course work, up to one or two years later if you wish. Which means that you can procrastinate and take five or six years for a degree or you can do it quite fast. I must have done it fairly fast. Three years is what the book says and that's what it must have been.

Weart:

So why did you choose Groningen?

Schmidt:

I lived there.

Weart:

You lived at home?

Schmidt:

I lived at home during that time and at this time I saw no reason to go to any other university. I might say that Holland had at that time I think five universities, all government, and then one city university, in Amsterdam. They were not all that different, like private colleges may be here, in their emphasis. It was all fairly standardized. So there's much less inclination there — perhaps it has changed now — to go as far away f rom home as possible, like some of my children like to do. So I just stayed at home.

Weart:

Was it any financial burden on your family? Were you supported by your family during your undergraduate days?

Schmidt:

Yes. It was not there the system at all that graduates or undergraduates are supported for the sake of support. That was not the system over there. I think it was not a major hardship on my parents at that time to send me through college — in other words, the first three years of my university education. No. I seem to remember that the tuition was fairly low, much like now would be for UC [University of California], say, a state school or so, which also has rather low fees unlike private colleges. Our colleges were subsidized in a sense by general taxes.

Weart:

You went in definitely with science in mind, in fact astronomy?

Schmidt:

Yes.

Weart:

What about the instruction? Were there teachers who made a particularly strong impression on you?

Schmidt:

Yes. Many of the, indeed. Probably because one is so impressionable at that age. I had two mathematics teachers by the name of Gerretsen and C.S. Meijer who taught geometry and algebra respectively and they left quite an impression on me. Then there was a lecturer by the name of Ridder. Strange that I remember al of these names because some of my later teachers, I've completely forgotten their names. In physics, we had, let's see — [slaps forehead].

Weart:

I can always look it up.

Schmidt:

I've now forgotten the physicist who taught us, an old sadistic character.

Weart:

Kept your noses to the grindstone?

Schmidt:

Yes, he sure did. And he ridiculed everybody in class always. Even though he faced a class of about 200 or so, he managed to ridicule individuals, especially the girls, who were relatively few, but by tradition, always sat in front, so he would ask them questions and they would be embarrassed. I've forgotten his name.

Weart:

What was the nature of the instruction in general?

Schmidt:

Class, lectures; no homework, no quizzes, no nothing.

Weart:

What about laboratory courses?

Schmidt:

Yes. In physics of course, and in astronomy.

Weart:

In astronomy also?

Schmidt:

There was also an astronomy lab, yes.

Weart:

What did you do in it?

Schmidt:

Astronomy lab actually was rather useful. I remember one of the labs was to draw a map of a simulation of Mars that was up front. And then there was quite a discussion about things that one thought one had seen. I mean, it was not exactly the canals but yes, it was really instructive. I remember, for instance, that the instructor was quite indignant that I had left out, out of the lower half of what hung there in front of the class a certain amount of shading. From the center line, horizontal diameter, down by a quarter of the diameter, there was quite a bit of shading. I'd completely left it out. When I traced back later why I had left it out, I realized that the thing was a fairly irregular piece of paper, and I thought that there was a little fold in the paper and that the side lighting had put a shadow there. So it's very interesting how in doing things like that, you are subject to all sorts of interpretations before your hand is instructed what to draw.

Weart:

Right. A valuable lesson.

Schmidt:

Yes, right.

Weart:

I've never heard of this sort of thing being done.

Schmidt:

No. It was sort of original. One of the other things was that we were given a piece of graduated paper, paper with marks on it like a millimeter scale, but more like a centimeter scale on which somebody had drawn lines in between, very accurately. He knew exactly where they were but we didn't. We had to guess, to a percent, what the reading was. The marks had numbers, 0,1,2,3,4,5, — and between a 3 and 4, you had to guess that a particular line there w as at 3.23, another one was at 4.98. It was fantastic because he then also gave us or we measured accurately, where these darned lines actually were. We found that there was a systematic error, that was a ????????????? function of the place where you had it between.

Weart:

Sort of cosinusodal ???????.

Schmidt:

Right. So if it was like 4.50 or so, you make in those cases a systematic error that I don't remember the sign of but if it was .50, you usually made very little error, not much more than 1 percent. But when you were near 4.10 or so, there was a systematic error of about .03. We plotted the whole thing and then determined the error by first taking out the systematic error. It was a very useful thing.

Weart:

This lab was an original?

Schmidt:

Yes. I think it was Plaut who was a lecturer there and subsequently became a professor; Lucas Plaut, I think.

Weart:

What about the more normal sort of astronomy exercises, looking through telescopes, doing calculations and so on?

Schmidt:

We did calculations but I cannot remember those. Looking through telescopes was not included in that particular lab, no.

Weart:

I see. Did you ever have a chance while at Groningen to see real research being done to use real research techniques?

Schmidt:

Yes. On top of the building, right in the middle of the city, there was a telescope and not that small a one — I seem to remember it was 50 centimeters or so — with which Plaut did observations, mostly for von Rhijn. Now, von Rhijn was really my professor, but he was sick almost all the time, and I met him only once or twice. He hardly appeared. He had acute tuberculosis or something like it. Von Rhijn of course was interested, as you know, in the luminosity function, which still carries his name, and in the distribution of stars in our neighborhood.

He was particularly interested in A-type stars but since absorption is such a difficult thing, he had thought of a way to observe them out where the absorption could be determined from A-type stars. So what we did, on top of the building in Groningen, or Plaut did, was to take spectra with cross-dispersion, one got a spectrum, and then these first and second order spectra next to it, which of course were down.

The cross-dispersion was probably done by a grating, a grind in front of the telescope, you know. You can exactly calculate the difference in magnitude between the zero, first and second order images, as a function of wave length, of course. Since it was done photographically, that was important. So that's the type of observation.

Weart:

And you participated in that, as a student?

Schmidt:

Oh, I went up several times to work with Plaut, to help him, and also to learn, but I never got fully engaged in it. It was a funny thing, there, because of course, it was in the center of the city. One night, when Plaut had to take an object that was fairly far down in the sky, and we were bothered by a particular lighted advertisement on top of a building, we decided that that light was too much. Now, believe it or not, we went down, got on our bicycles, went to that place, which was about a kilometer or so away, Plaut got out a key, and at eye level on the street, he turned off the confounded light. There was a city ordinance in Groningen at that time which, in the case of a few lighted advertisements on top of buildings, required that there be a switch at eye height on the street, and that the observatory be given the key. And we did it once [laughter]. That observatory is gone, by the way and I'm sure the city ordinance is forgotten.

Weart:

If only they would give us the key to San Diego.

Schmidt:

I doubt it. I'd like one to L.A.

Weart:

That's interesting. It would be interesting to find out the history of that ordinance. Tell me, what sort of physics did you learn at Groningen? Did you learn anything up-to- date? Quantum mechanics, relativity?

Schmidt:

No quantum mechanics there. Some special relativity, and no general relativity; only special relativity and the classical fields.

Weart:

How about in astronomy? Did you learn up-to-date things, did you feel?

Schmidt:

Yes, that was up-to-date, the astronomy. It was very up-to-date. It was a broad ranging course that did very well. It went from planetary orbits to structure of the galaxy and dynamics of the galaxy — but mostly structure — all the way to extra-galactic astronomy. Of course, you know this. It was just after the war, in the late forties, when extra-galactic astronomy probably was mostly limited to a description of the Andromeda Galaxy and an indication that there were many more like it.

Weart:

We didn't even have the 200 inch at that point.

Schmidt:

That's right.

Weart:

What about your fellow students in astronomy? Were there any of those that you kept up contact with later — as scientific colleagues or whatever?

Schmidt:

Borgman, the one whom I mentioned, followed me, rather late, because he first went into all sorts of other things, into industry as Phillips Eindhoven and so on, but he finally returned to astronomy. So we were not together at college really. No, I think that from those days, my college days, that I don't remember anyone else that stayed in astronomy. No.

Weart:

Who were these other astronomy students, do you know? Where did they come from? Where did they go?

Schmidt:

I would think that there were hardly any other astronomy students there. The education in college, for physics and astronomy, was very similar. I took the astronomy option, but if you took the physics option, it might be possible that for instance, you could replace the work that had to be done in astronomy by, say, work that had to be done in chemistry.

Weart:

So, those people who were talking astronomy just happened to be interested in it?

Schmidt:

Yes. Most of them were interested in physics and some of them where mathematicians. So the class of perhaps 15 or 20 that I was in, in most physics and astronomy classes, were almost all students who were in the physics option, and a few mathematicians.

Weart:

Have you any idea what sort of careers they were headed for?

Schmidt:

I have not followed most of them very closely. I know that one of them, two of them have become professors at one of the Dutch universities. But I have not managed to follow them.

Weart:

I see. So then you went on to graduate school?

Schmidt:

At Leiden, yes. Oort, who was of course the director of Leiden Observatory, invited me in early '49 to come to Leiden as an assistant. You see, again, going to graduate school, and the decision, but also the process of going to graduate school and being admitted is very different. I could at that time and I think it would still be like this — just indicate that I would continue graduate school at Groningen. Or I could just have written or gone to admissions at Leiden University and said, 'Here I am. So it's open — there's no admissions.

Weart:

What about the decision to go to graduate school at all? Was this already sort of...?

Schmidt:

Yes. Most students went on to graduate school, at that time. Baccalaureate was not a degree that really had much recognition, as it were. Now it has.

Weart:

Was there any question about what your future career would be? You almost faced that when you entered [college].

Schmidt:

Just about, although of course there was still plenty of change to switch around, say between physics and astronomy, or perhaps even other things. But yes, it was not much of a decision then. It was mostly the change of school, since Oort offered me this assistantship at Leiden, which was sort of an opportunity.

Weart:

How did that offer come about? How did he know of your existence?

Schmidt:

It is of course a small country. They had these annual meetings of all the astronomers plus their students together in some place in the country, which is a nice thing. It's small enough so that perhaps of the order of 60 to 70 people would show up there, or even fewer. So people knew each other. And of course, the number of astronomy professors was so small that they all talked to each other quite regularly. And the number of students was again fairly small, so it's not surprising that Oort knew about me.

Weart:

A letter simply came to you?

Schmidt:

No, he just asked me at that meeting, would I come to Leiden to be an assistant? And I'm sure I said yes. You know, Oort was already very well known. I think I might have gone to Leiden anyhow, but since he could take me, the decision could be made at any moment — not like here where, you know, for a year particularly your are writing and get letters of reference and so on. In May, when the meeting was held, I hadn't finally decided whether I would to Leiden — but I think I would have gone anyhow. Leiden was, especially at that time, very much more active than Groningen. Groningen was a somewhat dormant place in astronomy at that time.

Weart:

Ok. Well, let's talk about Leiden which of course is very interesting. Then, we'll come back to your actual scientific work there. I'm curious. There were Blaauw, van de Hulst, Westerhout was there?

Schmidt:

Westerhout was a student, of course.

Weart:

Westerhout was still a student?

Schmidt:

Oh yes.

Weart:

I see. Tell me about them and what the atmosphere was like there.

Schmidt:

The atmosphere, I would say was very much dominated by Oort's personality which can only perhaps be described as that of a scholar and a gentleman. And also of a very nice person. But in order to find that out, you had to know him a little closer. People in general might sometimes be somewhat turned off because Oort was always exceedingly sure of himself. I do remember that, while I was a graduate student, for a long time, whatever I said to him about something, he would never accept it. He was so clever and so intelligent that whatever you said about a certain subject that you were discussing, he always had a better insight in it — which I think in general he had. [Laughter] I remember that day, when I was well along in fact, when I said something and he thought it was a good idea. I really felt very far along, very fine that I'd made it that far.

Weart:

Oort was your thesis advisor?

Schmidt:

Yes.

Weart:

Was it also a formal relationship?

Schmidt:

Yes, he was my thesis advisor. And, of course, one of my professors. The others would have been — Blaauw was a professor there at that time? I can check it, or you can check it — Blaauw's career. Blaauw may have gone to Yerkes around that time.

Weart:

No, I don't have it here so you may well be right.

Schmidt:

I think he was not there most of the time. It was essentially Oort and Oosterhoff 'who was the man of the variable stars, classification of R.R. Lyrae stars in globular clusters and things) and van de Hulst 'who was first a reader or lecturer or whatever you call it, like an associate professor, and then became full professor). Those were the three professors there in astronomy. Oosterhoff was always somewhat in the background but very nice. Van de Hulst at that time was really coming up as the wunderkind, the whiz kid.

Oort had great expectations of hi and confidence in him, which I think were not eventually fulfilled. Van de Hulst has been relatively inactive for quite a number of years now, as you know — he's in administration, the organization of the Dutch space work, and half the time he's been heading this organization between the several unions that has to do with Space Science — COSPAR. He headed COSPAR in its beginning. [BREAK TO GET COFFEE]

Weart:

I want to ask you what these people were like as teachers, particularly Oort and van de Hulst?

Schmidt:

Van de Hulst as a teacher was brilliant. He must have been one of the best teachers that I know. I remember lectures of his about spectrographs, which was none of his business as it were; he was a theoretician. But he'd looked into them and came up not only with the usual stuff about spectrographs, but an evaluation about the performance characteristics and the main features of practically all the spectrographs in astronomy. The one at McDonald, the one at the Newtonian focus of the 100-inch.

Weart:

Real spectrographs.

Schmidt:

Real spectrographs, mentioned by name, got their main characteristics out and illuminated what was important to know, the speed and things like that. It was very cleverly done. Oort as a teacher was very different. He did not take you by the hand and guide you to where you could understand, as it were, almost anything, by carefully measured steps. Oort would always talk at a quite elevated level, and never step down. Which sort of had the effect of segregating, I think, his listeners and his students into two groups — the one group that learned an awful lot, and the other group that didn't profit very much from this. I'm sure that Jan Oort simply wasn't interested in the second group. I think he felt that his lectures were designed to get people to the level or stage where they could do interesting research, but not just for their general education. That he left to others, as it were. So there's a bit of description, not complete, of course.

Weart:

By the way, how much direction did Oort exercise over the sort of research that people did, both students and also other people at Leiden?

Schmidt:

A lot. An enormous amount. He would talk to essentially everybody in the observatory — except, of course, the students of van de Hulst he would hardly talk to. He would not interfere in the usual thesis supervision.

Weart:

Would he talk to van de Hulst about what van de Hulst and his students were doing?

Schmidt:

He would talk about what van de Hulst, certainly, himself was doing — little about his students, I think. But he would talk to all the other astronomers in the observatory about what they were doing. He'd usually do it by an innocent question, at coffee or whatever, of how things were going. And then the scene would shift to his office where the man was invited in to continue the story. And it wasn't long until he got to hear that, you know — this was interesting, and that might be done that way. His advice of course was always so deep and so correct that he had a great influence on everything that happened. Everything.

Weart:

I see. It was done in a gentle sort of a way.

Schmidt:

Yes, but very persuasive and by the power of his intellect, there was nothing anybody could do about it.

Weart:

I see. He simply persuaded you by intellectual force.

Schmidt:

Yes, that's right.

Weart:

How were his personal relations with people around there?

Schmidt:

His personal relations? Except for the relatively few people, I think, who could not stand his intellectual dominating, as it were, they were very good. He was always very correct and friendly, and his wife is also a very, very nice person, so that, especially for the younger people, at times they acted almost like parents.

Weart:

As a student, were you ever to his house?

Schmidt:

Yes. Not to dinner, I think, but once in a while to a larger gathering. Only later on were invited to dinner, or was I invited to dinner, I think.

Weart:

Some of the other students or astronomers would come over, that sort of thing?

Schmidt:

Those would be occasions of that kind, at Christmas or so.

Weart:

I see. Did you discuss your scientific work much with the other students. The astronomy students, formally or informally?

Schmidt:

Yes. There was lots of talk about the work you were doing and about what they were doing. [COFFEE ARRIVES, SHORT BREAK]

Schmidt:

So the exchange with others was very much like it would be these days, you know, with astronomers among themselves.

Weart:

Were there any clubs where students would talk with each other in a more formal way?

Schmidt:

I don't think so. I don't remember that.

Weart:

What about seminars, colloquia, journal clubs?

Schmidt:

There was a journal club, later on.

Weart:

Later on?

Schmidt:

Yes, I think that was probably started in '54 or '55 or so, in which the literature was [reviewed]. And there was a regular seminar every week, at which both the professors and the students talked. But with relatively few visitors, except when they happened to come through. One wouldn't attract them from elsewhere. I think I once gave a — The first one I gave, I was told to talk about the corona and the zodiacal light which I knew nothing about. Anyhow, those were given weekly.

Weart:

I see. So it was only partly a way of keeping up with current research and partly a sort of training seminar?

Schmidt:

Yes, both.

Weart:

How large was the astronomical community there anyway?

Schmidt:

At Leiden? That would have been say in the early fifties. Besides, those three professors that I mentioned, there would have been a few other astronomers, like Walraven, van Herk, and then perhaps ten graduate students or so, of that order.

Weart:

You mentioned Westerhout. Were there others that —

Schmidt:

Westerhout, Muller, he's now with ESO [European Southern Observatory] I think. Van Woorden, whom you probably know. He's at Groningen now. Wulcher, who's now director of ESO.

Weart:

They were pretty much all bound to — or many of them —

Schmidt:

Yes, right. Of course, those are perhaps the ones I remember easiest. There was young Jan Wolfer Muller who went to South Africa, whom I saw, I think, a few years ago there, but who is not all that prominent anymore —

Weart:

It must have been quite a lively group.

Schmidt:

Kwee, who is still at Leiden, a variable star man. And so on.

Weart:

Were there places where you would get together informally, any important bars or restaurants? Boarding houses or whatever?

Schmidt:

There was a student house, or a house for students, at the observatory, Number 2. It was Number 2 in the complex there.

Weart:

Oh, there was a Director's residence and —

Schmidt:

Sternwecht 2 it was called and that's where I lived for quite a number of years. And in the other rooms were Klee, Westerhout and van Woorden. So we often went out together to dinner, or we had dinner at home, and one of us would make it. Especially Klee would make marvelous Chinese dinners, just fantastic. So we had a lot of contact with each other that way, of an informal nature.

Weart:

Did you talk about things besides astronomy? Did you personally, or they, show interest in philosophy or the sciences or whatever?

Schmidt:

Well, I don't think you could call it a science, but obviously, young people like that talk about things that are philosophical, I'm sure, although I don't remember it in detail. Most probably about girls too.

Weart:

And politics?

Schmidt:

Probably some politics. Not much, I think. Can I mention one thing at this stage Spencer? It is likely that — unless you already know about it — if you go on like this, you're going to overlook something that happened during my graduate education, which was a lengthy interruption, which you probably don't know about. I spent 1-1/2 years in Africa during that time.

Weart:

Oh, I didn't know. My next question was, 'Did you do all your training at Leiden or spend some time elsewhere?' But I never would have thought of asking you about Africa.

Schmidt:

Oh, you're perfect, you see, and I shouldn't have said anything, just sit back and wait. 'Laughter).

Weart:

No. I was going to ask whether you had attended conferences and things like that. I certainly wouldn't have asked you about Africa.

Schmidt:

I did attend conferences but let me first get Africa in. It was an unusual episode, in a sense, but I'll make it fairly brief. Let me describe the chronology of my graduate education. I came there in July 1949. I was called to military service in Holland and did not get an extension any more during the summer. In September '49, I went into the military service. After six weeks of basic training, the army couldn't decide where to assign me, you know, for the subsequent 18 months. That went on for four weeks, during which I did rather little and then they dismissed me. They couldn't decide. I wasn't the only one. There were 11 others in this particular group I was with that the army managed to not assign through bureaucracy or whatever.

Weart:

It wasn't because you were a graduate student?

Schmidt:

No, no.

Weart:

In general did all the graduate students have to go into the army?

Schmidt:

Well, some of them got extensions beyond that period. I don't quite remember, but I think most of them had to. At the end of your undergraduate education, there came this moment that most of them had to serve. At that time at least. So I got out of the army in early November and went back to the observatory and managed to get back into the course work which had already started, of course. And then, right on the last day of the year, while I was sitting there and doing my thing, Oort called me in and said, would I be interested next August 'and I did that in fact, in August, 1950) to go to Kenya? An expedition of the Leiden Observatory had been stationed there since 1946. The expedition, consisting of van Herk and his wife and a Dutch navy lieutenant, was there to measure declinations of starts, from a point on the earth's equator, azimuth measurements.

Weart:

I see, you sit right on the equator —

Schmidt:

Right. You sit on the equator, your telescope is just above the horizon, in fact 7 degrees, and the azimuth of rising and setting, the difference of those two is two times 90 degrees minus dec. It has the advantage that refraction doesn't come in; it's a horizontal angle. It was already tried there in 1932 for a short while, under the famous de Sitter and after the war van Herk had been sent out — It was a major effort for the Dutch of course because even nails were still rationed when they left in 1946. How they managed to get that thing sent off, I don't know. Anyhow, in '49, the lieutenant was told by the navy that his three years of leave were up and he should come back to the navy. They wanted somebody else to finish doing the work, which was to take another year. So lo and behold, in August 1950, I went to Kenya and stayed there till November or December 1951. '

Schmidt:

So I was in Kenya. I had a very interesting period there. You know, life is different there. We lived on Timboroa Hill — that's what it's called. It's actually a mountain 9,600 feet high, and we lived on top. We reached it by four wheel drive, off the main road from Nairobi to Lake Victoria, about halfway in between, and did there lots of observations. We observed the whole FK — it would have been three or four, it must have been three at the time — we did the whole FK — 3 with come GC stars in between. But the idea, in case you want to be terribly technical, was to find out about delta 'delta 'delta)). Delta 'delta) is the error in declination, and then, the error in declination as a function of declination — so it was delta 'delta 'delta)) we were after.

Weart:

I understand.

Schmidt:

I did, in the meantime, some observations of the zodiacal light — that were never published because they were terribly incomplete and so on — with a photoelectric multiplier, and with German war searchlight mirrors, large mirrors. Very interesting. But it never yielded anything.

Weart:

Must have been nice clear skies. That was the first time you saw really clear skies?

Schmidt:

Yes. At 9,600 feet high, you do get a beautiful sky and no city lights to interfere. It was beautiful country; it was a pleasant climate because it was that high.

Weart:

So you did a lot of things around there. You observed the stars, you —

Schmidt:

We mostly observed the stars at night and repaired the road in day time because the road from the main road to our place, which was perhaps 1,500 feet up or so or perhaps even more, was terribly bad, and we had to repair it. I think I spent the whole month of August 1951 with our laborers, just to improve the road. Get rocks at a quarry, while it was raining all the time.

Weart:

Was this your first practical experience with any sort of a real research program?

Schmidt:

Yes, right, under very strange conditions.

Weart:

To return to Leiden, what were your duties as assistant there?

Schmidt:

That's a good question. I think that there were probably hardly any formal duties. You were expected to observe. But I would think that every graduate student, by moral pressure, was sort of expected to observe, at night time. So we divided up the telescope time. The telescopes again were right on the compound of the Leiden Observatory there in the middle of the city. I went soon into comet observations.

Weart:

But did you have freedom to choose what you would be observing?

Schmidt:

Yes, I think to quite a degree it was my own choice. I think I had been to the first or the second Liege International Colloquium — as you know, it's still held every year. It was the first or second one, and I remember Whipple was there and Wuram and Dufet and all. It inspired me, that conference, I think, to try and measure the emission bands due to CN and CII Swan bands and so on, in cometary envelopes — to measure their brightness as a function of distance from the sun. So I got a number of interference filters, and with photoelectric photometry, undertook that program.

Weart:

Photoelectric?

Schmidt:

It was photoelectric at the time, with a 931A [photo multiplier].

Weart:

Oh, with an old 931A?

Schmidt:

Old 931A.

Weart:

In those days, they were not so old.

Schmidt:

That's right, it was just out.

Weart:

You mentioned also in Africa you used photoelectric things?

Schmidt:

Yes. This was also a 931A, or a 1P21. The 1P21's were so expensive at that time.

Weart:

Were they?

Schmidt:

Yes, they started out being very expensive. I think they were selected 931A's — I haven't even remembered this, the term 931A. It just popped in my mind.

Weart:

Then you were quite up on the latest instrumentation, in fact?

Schmidt:

Yes, we were. In fact, I remember that at Leiden, we even did pulse counting which was not to appear in general all over astronomy until quite a few years later.

Weart:

It was very difficult to do pulse counting with the electronics they had then.

Schmidt:

Yes, that's right.

Weart:

Always counting the wrong pulses —

Schmidt:

Yes, right. The dome would move and so on but we did pulse counting at that time. We first started with a Braun recorder of course.

Weart:

A Braun recorder?

Schmidt:

I may have to take that back. Because the first night, I remember, that I observed — Oosterhoff introduced me and said, 'OK, I'll go home now for coffee and you can take over.' It was like this: it was with a galvonometer, which projected a beam of light on the wall, on a big scale, and the way you read it, Osterhoff taught me, was as follows: You sat there at the desk while the telescope was going, it took only a minute or so, and you had your piece of paper there. You looked up, you said, '15.8". You looked up, 16.0 off. You did that five times and you went to the next star. The needle of course was going [back and forth].

Weart:

But his isn't pulse counting, this is —

Schmidt:

No, that was the first [system] we did. This first experience was in fact in 1949, that I'm talking about. It was really very early. We got into the pulse counting business through Walraven, I'm sure, who was an electronic wizard. That was probably '53 or '54. Quite a step from the one to the other. I'm not even sure if there was a recorder in between. There must have been.

Weart:

Ok, so then to be an assistant it was in effect like a fellowship?

Schmidt:

I think so. Yes.

Weart:

How was the work organized around the observatory? Who made sure that the telescope was kept in order, that sort of thing? Was it just shared around?

Schmidt:

Oh, I remember, there was some Friday meeting at which the director, Oort, with the top man of the shop and with several astronomers, would discuss everything that was going on at the observatory; the upkeep of the telescopes was also discussed there, and priorities assigned to the shop and so on.

Weart:

I see. But as far as you were concerned, it was simply a device that was there to be used.

Schmidt:

Yes. I ought to volunteer one thing about the salary and the vacation of the assistants. What I got at that time was actually sometimes called a two-thirds assistanship. The reason was that Hertzsprung, who had been director of the observatory before Oort took over in 1946, had two assistantships; and he used them as slaves, I'm sure. He decided that he wanted another assistant but there was no money in the university for that so he took the two assistantships and divided them in three together, so those became two-thirds assistantships. What I got when I came was 10 guilders per month. The whole thing was 165. But the funny thing was that the original assistants also got three weeks vacation. When these were divided into two-thirds assistantships, each of the then assistants got two weeks vacation. So I did have two weeks vacation.

Weart:

I see. That was cut into two-thirds also. Nevertheless you continued working full time.

Schmidt:

Of course I did. There was nothing two-thirds about what we did. [Laughter]

Weart:

Right. I don't suppose the amount of vacation time you were given mattered because after all, your duties were simply to be doing your research.

Schmidt:

Yes. That's right.

Weart:

So you did this paper on the evolution of brightness of comets.

Schmidt:

Yes, that was attempting to do observations of the way the emission lines changed. I should say that really, rather separate from that interest of mine, there developed or had already developed Oort's interest in this comet cloud — that is sometimes called Oort's cloud of comets. One of the investigations Oort and I did together, very early, was about the rate of change of the brightness of comets with distance to the sun. That had nothing to do with this attempt to observe emission lines and see how they behaved. That checked a comet model by Levine, I believe, at that time, or whatever. But that was quite separate from that.

Weart:

I see.

Schmidt:

This article with Oort was an archival study throughout the entire literature for every conceivable comet going back very far in fact to come up with the rate of change of brightness in various solar distance. And, we found that so-called 'new' comets, that had apparently come in for the first time, changed their brightness much more slowly, with solar distance, than did old comets. Comet Encke has a strong dependence of its brightness on solar distance, and new comets have very much less. That was interesting, that we could find some physical characteristic that seemed to distinguish between those two types.

Weart:

I see. I also have that in '53, you had a paper on streamers in the solar corona, electron densities.

Schmidt:

Yes. Seems an odd bunch of different interests. I did as a research job, for van de Hulst, measurements of plates taken by Richtmyer on a solar eclipse observed in the Pacific, I think, in 1936. A fourfold camera, with a direct and then three exposures, all simultaneous, with different polarization directions. I studied the entire distribution of brightness in the corona, as far as it could be seen, and the streamers, and published the results, which were sort of reasonably good. That was a research project.

Weart:

It was in effect assigned to you?

Schmidt:

Yes, right.

Weart:

Tell me, we haven't really talked yet about the instruction proper at Leiden. At this point, how much physics for example did you get?

Schmidt:

I got quantum mechanics from Kramers, by the way. Golly, how much more physics did I get there?

Weart:

General relativity?

Schmidt:

I don't think I was taught general relativity, believe it or not. I don't think so.

Weart:

When have you learned general relativity? Was there every a point, when you sat down and —?

Schmidt:

I don't think I ever learned it.

Weart:

Pieces here and there?

Schmidt:

That's right.

Weart:

What sort of the balance, in your instruction, in terms of classical stellar studies, spectroscopy, galactic, extra-galactic?

Schmidt:

It was all course work again.

Weart:

Lectures?

Schmidt:

Yes, right. All lecturer courses. I don't even remember any lab. Of course, the students were supposed to go out at night and observe with the telescopes so that became less perhaps necessary. But the courses had the usual sort of areas, like the interstellar medium, the sun and the solar corona, galactic structure and dynamics, the usual subjects. Radio astronomy was also given by van de Hulst, when it got started, as it were.

Weart:

He gave a special course in it?

Schmidt:

Yes. That course is now given probably everywhere, I think.

Weart:

Did you or any of the other students every get together and try to get a course in any particular topic?

Schmidt:

That is, we asked for something?

Weart:

Yes.

Schmidt:

No, I don't think so. If we had self-propelled activity, it would exhibit itself in research that we did. For instance, this corona work, although I think that it was probably an arrangement between Oort and van de Hulst and I, Hank [van de Hulst] needed somebody to do that so they talked to me and I said 'Yes.' I did, for instance, another research project while a grad student that was really very large. It was the 21-centimeter — the first 21-centimeter determination of the spiral structure.

Weart:

Yes, we'll get back to that —

Schmidt:

— and it was just a research project as a grad student. It was not my thesis work.

Weart:

I see. It was not your thesis work?

Schmidt:

No. It was a model of the galaxy, a gravitational model.

Weart:

I want to get back to that, but first, just general questions about the instruction. So you would take these courses, and then there would be exams at some point?

Schmidt:

This sounds strange — but, at your own convenience.

Weart:

The European system.

Schmidt:

At you own convenience. So, in most of the cases, I took the exam between one and three years later. I don't think it's too good a system, you know —

Weart:

— but there was one exam for each course?

Schmidt:

Yes. And it was a private exam. In other words, you talked to a professor and he said, 'Ok, some to my house at 2 PM on Saturday' or 'on Monday afternoon.' So you went there, had a cup of tea, and sort of lightly talked about the subject. Then it depended on how well you did, whether he would go into a very thorough examination or would, after a while, say, 'Well, I'm sure you know it all.' You know. After all, they know you very well, of course, anyhow.

Weart:

Then you had to have so many courses of this sort, in order to —-?

Schmidt:

— yes, there was a list of things one had to do, and so on—

Weart:

I see. Tell me, was there much interest in cosmology around Leiden in the fifties?

Schmidt:

No. If you mean what is now called cosmology, having things to do with the universe, the overall density or the like — no. You see, in the early fifties, since '51, the 21-centimeter line was discovered, which had been predicted by Hank van de Hulst and also by Shlovskii in '45 the attention was almost entirely concentrated on that. It was a very exciting time. So between '51 and '56 or so, almost all the activities in the observatory were aimed at that.

Weart:

You must have at least talked about the ideas of Big Bang and Steady State and so forth?

Schmidt:

Yes, we did. And I remember Fred Hoyle coming in and giving a lecture about the Steady State. I think he gave the lecture in '52 or '53. I still remember that Fred gave a lecture and said that in a couple of months time, he would go to Pasadena, and then they would check on the works, you know, they would check on it with the 200-inch. I remember that I already at that time was skeptical enough about the thing that I asked him in detail, what did he mean in detail to 'check up' with the 200-inch, how do you do that? I didn't quite believe that it could be done. So he sort of said a few work, I don't remember what, but that was my first exchange with Fred Hoyle as an innocent graduate student who was listening with some awe but also a slight distrust about how can you 'check' with the 200-inch? I think Fred had just given the Reith Lectures on BBC, so he was well-known already.

Weart:

I see. Do you recall what your attitude and the attitude of the people there was toward Steady State? Or Big Bang, for that matter?

Schmidt:

Not for sure. It never got over there any sympathetic reception, but I cannot remember any discussions in detail about it. Oort was certainly not in favor of wild speculation ever. He always wanted to, and still wants to, stay very close to the observations. So I'm sure he thought it was wild.

Weart:

I see. Now, a little more about your relationships with outsiders. You mentioned that occasionally visitors came through. Did you feel that you were pretty much up on what was going on in the rest of the astronomical world?

Schmidt:

Yes, I think so.

Weart:

How did you usually learn about new things?

Schmidt:

Usually at a colloquium I would say. And also, we had a morning tea, morning coffee, at 10:30 at which the entire observatory gathered.

Weart:

Every day?

Schmidt:

Yes, every day. Usually it would last 15 minutes or sometimes a little longer. There were never any speeches or central discussions or so, but one would hear about things, if something interesting happened. And since Jan Oort was very well informed and know about things, it would penetrate.

Weart:

I see. What journals did you read regularly?

Schmidt:

I think I took a subscription to the Astrophysical Journal in 1952. And to the Astronomical Journal later but I certainly would read those two, of course. I read the usual other ones, the Astronomical Nachrichten, the Observatory, Monthly Notices [of the Royal Astronomical Society]. There were some French magazines at that time that now don't exist any more I'm sure that one read. We read fairly widely.

Weart:

Did you read articles on a variety of subjects or did you just go in to look for particular things?

Schmidt:

That I can't remember. But, we were fairly well informed, I must say. I'm certainly not following things as well now, certainly not through literature reading, as I did at that time.

Weart:

It was more through journals then than there would be now.

Schmidt:

Yes. And of course mostly because of a lack of time at this moment, and a proliferation in the overall output.

Weart:

And of course also your position is different. Jan Oort may well have heard of things before they came in the journal.

Schmidt:

That's right.

Weart:

Tell me, just a general question, to back off from it all — what was it about Leiden, or the Netherlands in general, that made the Netherlands such a center for astronomy?

Schmidt:

That's a good question. I imagine it has to do with personalities: with the nature of Kapteyn, first, who of course died in '22 and then I would think with Oort who got his PhD, I think, in '26 or so. There may have been somewhat of a gap there. But it has to be the scientific leadership of each of those that set the stage. They must have attracted younger people into that field and so on. There's no other way I can understand what happened. And I still don't quite understand it, of course. It's a phenomenon.

Weart:

There wasn't anything about the universities themselves or the observatories that made them particularly different from other places?

Schmidt:

No. You might way that if Holland, as a consequence of this, in terms of overall facilities, reflected the excellence of the astronomers that were educated there, that really only happened of the order of ten years ago, when the Westerbork facility was built there. That was a major achievement and in terms of the nation's total budget, it was a sizable thing. It cost on the order of six million dollars, I believe, six or seven million dollars. So, no, it was not in material things that it exhibited itself at any time before 1955 or 1960. It must have just been the persuasion to attract people — not only do you have to have scientific leadership, but something else that attracts young people. Not only that but also, the best young people only because you don't want to have an enormous school there.

Weart:

Somehow you were attracted before you even know Oort was there so to speak.

Schmidt:

That is quite true. I'm afraid, indeed, that if you checked individually about all the astronomers, you'd say, 'Quite an output of this country.' Now, check with them each individually, it may well be that none of them will really point directly to Kapteyn or to Oort and say, 'He did it.' And yet —

Weart:

It must have become —

Schmidt:

It must have been, to some degree. These were of course people who were known in the country. Jan Oort is well known in Holland as a scientific leader.

Weart:

Ok. Well, it's a mystery.

Schmidt:

It is a mystery, in a sense. But then, the whole way in which schools develop, it seems to me, is a mystery. Look in this country at what happened at Yerkes and at Harvard. I think you can see waves. Ups and downs that are pretty frightful in their aptitude.

Weart:

Yes, and it has something to do with personalities.

Schmidt:

Yes. In the middle fifties, Yerkes was almost at the top of the heap. And think of all the people who were there: Stromgren, Struve, Payne-Gaposchkin, Hiltner, Morgan, everybody. And yet, I think that since recently, there were well, they are not terribly prominent any more, to say the very least.

Weart:

Yes.

Schmidt:

It worries me sometimes, these waves.

Weart:

That it can happen.

Schmidt:

It can happen at any place.

Weart:

Yes. One never knows.

Schmidt:

That's right.

Weart:

Well, I don't know — if you have a 200-inch telescope, I image that would tend to dampen some of the fluctuations.

Schmidt:

We'll see.

Weart:

We'll see.

Schmidt:

By the way, I immodestly would consider myself — I may be wrong — in a sense, almost the last member of the Kapteyn school.

Weart:

The Kapteyn school?

Schmidt:

Yes, the Kapteyn school. I don't know whether it's a generally recognized school. Nonetheless I think he started something, that had to do with the systematic investigation of the structure of the galaxy in a way that was not analytical, like Charlier and others had done, but when he really had counts and little bins in which he placed stars and things like that. Which led of course to his, and later to fan Rhijn's, luminosity f unction. Van Rhijn of course was his most influential and famous pupil there.

But there were also people like Bok and Luyten and van de Kamp, Oort, Blaauw, who all came out of that school, at it were. And the next generation after Blaauw has as its members people like Westerhout, who I think is not very much in it, he's doing other things an Wulcher, who is not. And I somehow feel — partly because of the work I've done in galactic structure, but also because in an unexpected fashion, to jump to the present, that I now find, since about five or seven years, that I use these Kapteyn-like methods in finding out about the distribution of quasars in the universe.

Weart:

Yes, I noticed that.

Schmidt:

I find myself very much a descendant of his there.

Weart:

I was going to ask, at a much later point, whether you think it came from this.

Schmidt:

Oh yes, definitely so.

Weart:

And this you learned came essentially from Oort or just from general people there?

Schmidt:

Yes. It was of course taught in class. But, yes, also in general. Plaut also taught it I think — it's something you're aware of over there. At least, you were. I'm sure they now think mostly about radio astronomy.

Weart:

Well, let's talk about those things then. There were two things essentially. One was the spiral structure which you mentioned.

Schmidt:

Yes.

Weart:

One was the model of the distribution of mass in the galactic system.

Schmidt:

Right.

Weart:

I don't know, I find it a little difficult to distinguish between the two of them because they were both done from this Kwee, Muller and Westerhout survey.

Schmidt:

That's true.

Weart:

But let's sort of start from the beginning with the 21-centimeter. What are your recollections of that whole development?

Schmidt:

My recollections were that first, the line of course was discovered in '51.

Weart:

Do you remember that?

Schmidt:

No, I was in Kenya in '51. But I remember that — I think it was before that, while the installation was already up 'that I remember), and that was somewhere in the eastern part of Holland, it must have been in early '50 — I remember a meeting at which Oort announced that the installation had burned down. The line hadn't been found yet, but there was this Woods-Berg? Antenna and the installation had burned down. I think what they did, at the same time, they somehow also let go of the engineer. And, I'm sure they then got Muller in, C.A. Muller, who is not the Muller I mentioned as a student.

Weart:

Another Muller?

Schmidt:

Oh yes, the radio astronomer, engineer. He was very good. I think the burning down of the installation and the getting in of C.A. Muller there probably contributed to the Dutch just making it, also at the same time, the Australians of course as Hugh and then Dicke or whoever at Harvard, and then — it all happened within weeks of each other.

Weart:

There are a few other stories like that. The apparatus broke, so we had to rebuild it and t hen that allowed us —

Schmidt:

— the next generation can help. Both people and instruments. Ok, the line then was discovered while I was away in Kenya, so I didn't see that, or experience that from nearby.

Weart:

People were very excited about it when you got back.

Schmidt:

Yes. But I didn't give it all that much attention at that time because I was getting back in December '51. For the second time, I had to start in the middle of a year of lectures and lecture courses in Holland are always for a whole year. So I didn't miss a term, I missed one-third of a year's length of lectures and I had to work like anything to catch up. So I didn't pay attention to things at first, very much; except probably most likely in the summer of '52, when something unusual happened. There were measurements then in progress at Kootwijk, which was the Dutch Radio Observatory then.

A survey done every 2-1/2 or every 5 degrees along the galactic plane that of course gave rise to the first map of the outer spiral structure. And there was so much reduction work to be done at that time that some time in the early summer, I think of '52, one morning at coffee Oort and van de Hulst said that they were sorry but everybody had to stop what they were doing; you were all invited into the classroom and there would be records and there would be instructions on what to do with them. So, everybody, students —

Weart:

I see. Making measurements of the tracings —-

Schmidt:

Yes, right, and they had to be corrected for antenna patterns, oh my God, for bandwidth effects, etc. So we all worked like crazy. And I think that that is what yielded the first paper with spiral structure which was written by Oort, van de Hulst and Muller. That probably did come out in the BAN, I think in '52 or so. I'm not sure about the year exactly. But that event happened, where we were all told that, I think for a whole week, we had to work at this.

Weart:

That's not so bad.

Schmidt:

They had to get ready for a conference.

Weart:

They were in a great hurry to get it out.

Schmidt:

Yes.

Weart:

It was a hot subject, other people were on it.

Schmidt:

Yes, and there were no computers at that time. There was no way to get it out unless everybody — so we did it. Now, that gave the outer arm. You know that when you look through the galactic plane, at a longitude of, what shall we say, 40 degrees away from the center, that there is this horrible confusion in the inner part of the galaxy because nearby stuff and farther stuff which is at the same galactic radius has the same radial velocity—

Weart:

—right, you're looking at—

Schmidt:

But in the outer stuff, there's no such confusion.

Weart:

It's not double-valued.

Schmidt:

Right. So what they did at that time was to come out with the outer spiral arm which was very impressive of course.

Weart:

Along just zero latitude.

Schmidt:

Right. The next thing that happened was the investigation of the highest velocity you can see as a function of galactic longitude.

Weart:

Again, if you take just the highest velocity —

Schmidt:

—that has to do with the rotational velocity, of course, and with your own. So that was done by Kwee, Westerhout and Muller. And that gave rise to a rotation curve. And next came my research on the spiral structure in the interior part —

Weart:

This was essentially before you got into the model of the mass distribution?

Schmidt:

Correct. So that rotation curve of Kwee, Muller and Westerhout allowed me to do two things. One was to determine the spiral structure in the interior part of the galaxy, and I did effect a separation between near and far contributions, which was very tricky. And second, for my thesis work, I used that same rotation curve which they had to build a model of the galaxy — of the overall mass distribution. So those two were in a sense rather different investigations, although they both used the rotation curve. The one was to get the hydrogen distribution in the interior part — and it's still a minor part of the mass, of course — and second investigation was to understand the dynamics of the whole thing, by finding out the mass distribution that would give rise to such a rotation curve.

Weart:

Right. To get back a moment to the spiral structure of the inner galaxy, how did you come to this problem? Why was it that you picked up this as a problem? Was it assigned to you?

Schmidt:

With Oort, you never knew whether it was assigned to you or not. And, I cannot remember, for that reason. I'm sure that he talked to me about it, and made me see that it was an interesting problem. So I undertook it. And it probably was really assigned.

Weart:

I see. But in a painless way.

Schmidt:

Oh yes. It was a major job. I mean, for a research project while you're a graduate student, it was an unbelievable job.

Weart:

I'm curious about how the calculations were done. There was an enormous amount of calculation.

Schmidt:

Incredible

Weart:

You thanked Mr. E. deRooy. What was this, was it with hand-cranked calculators and so forth?

Schmidt:

Yes

Weart:

Who was this de Rooy?

Schmidt:

Well, he was a computer— The Leiden Observatory did have, and probably still has on the order of six or seven human computers.

Weart:

Oh, that many? Full time?

Schmidt:

Yes. Probably that many at that time. They would do calculations as assigned by the astronomers. So I gave precise instructions to Mr. deRooy as to how he should proceed and checked all the time and talked with him and so on.

Weart:

Were those people mostly women, by the way?

Schmidt:

No, they were all men.

Weart:

Why is that when at most other observatories, they were all women?

Schmidt:

I can't say.

Weart:

So it was just a matter of setting him up and he would turn the crank. Was it literally the hand-cranked ones, or were they machines in those days? Motor -driven?

Schmidt:

Oh, definitely not motor-driven. I'm trying to remember whether he used a machine. He probably did, one of these small hand-cranked machines, deGow, whatever it is. No, I don't think it was motor-driven. Although, who knows?

Weart:

It may have been. So this work — to what extent did you regard it or did people regard it as your own work and to what extent was it just sort of regarded as Leiden work?

Schmidt:

Well, when you went out with it to conferences, then of course you considered it very much a part of the Leiden program, because it all hung together. Because in the meantime Westerhout was doing a much better job of the outer part of the galaxy. I suddenly remember, mentioning Westerhout: since we got so much material, we finally moved to the attic of the observatory, Westerhout and I did, because there was such massive stuff, records and so on.

And I remember, we imported two girl computers there. So we did have extra help, and they were girls, which was sensible. It was a very massive job. But the method I followed, which is explained in the paper, was very much my own, although I'm sure I discussed it regularly with Oort. I think in the main, it was my own method I used there, to separate these contributions.

Weart:

The idea using the latitude effect?

Schmidt:

Yes.

Weart:

I see. He sort of discussed it as a problem and you came up with this possible way of doing it.

Schmidt:

That's right. The way I found out it could be done was, at the highest frequencies, corresponding to the highest velocities that Kwee, Muller and Westerhout had found, I measured the [latitude] width of the layer in degrees; and since you knew where those points were, you could in effect plot the thickness of the layer in parsecs versus distance from the center. And it turns out to be quite consistent, a slow increase, or perhaps not even an increase. I could just set a value for that. So that was then used as an angular distance meter, as it were.

Weart:

This was all using measurements—-

Schmidt:

Yes, that I took myself.

Weart:

Oh, that you took yourself? I wasn't clear about that.

Schmidt:

Oh yes, at Kootwijk, because the measurements had to be done; one had to move the antenna at a fixed frequency, say, slowly at a constant longitude, varying [galactic] latitude, in order to get a profile. No, it was probably done in right ascension, but that angle is well, etc. — that required special measurements, which I all did myself.

Weart:

I see. I wondered why they had a latitude survey — you saw the need for it and went out and did it.

Schmidt:

Right. And, in fact, I think that I observed all the material, in toto, that went into this determination, myself. It was on the order of probably between seven and nine weeks of observing.

Weart:

I see. I probably hadn't read that paper carefully enough. I hadn't understood that from the paper. It almost seemed as if these observations were just there in the first place.

Schmidt:

No.

Weart:

I see. But you mentioned working with Westerhout. Westerhout helped you run the thing, or showed you how to run it?

Schmidt:

No. Locally, Muller was responsible for helping observers to run it. But Westerhout was doing, parallel to me, a new determination of the outer spiral structure. A repetition of what had already been done, but now three-dimensional.

Weart:

I see. Tell me about this spiral structure, I wonder, did the interest have anything to do with Morgan's work starting about the same time, for tracing spiral structure with early-type stars?

Schmidt:

Yes. We thought about it a lot and wondered very much whether we would get the same structure. In fact, we were very confident that we would, and somewhat surprised when it didn't seem to fit so well. That was very much in everybody's attention, of course.

Weart:

How did you feel that your work was accepted? Later on, Bok had some objections to some of these arms, some question of whether they were trailing or leading, whether it was spiral or irregular.

Schmidt:

I think, in the beginning, we were perhaps a little over-optimistic about the reliability of what we got. It's only after a number of years that you realize the limitations of a method like that. It was such an enormous amount of progress over what could be done before because suddenly, you were looking all over the galaxy without trouble with absorption, got quite accurate velocities — it was like heaven! The inner spiral arm seemed to be somewhat inclined but only a small angle and the outer spiral arm, I seem to remember, was not inclined at all. We were somewhat puzzled about this. And Morgan and Osterbrook and Shapley's arm, of course, was rather badly inclined. I think when Bok wanted to make different connections from the north to the south, that is, from longitude 90 to 270, we were perhaps somewhat surprised. But I never felt unhappy about the reception of this work in the community. No.

Weart:

I see. Speaking of that, I notice that you first presented results at IAU Symposium No. 4 at Jodrell Bank. Do you recall that conference?

Schmidt:

Yes. Although I think 'perhaps I should bring out a publication list for you) at an earlier time, I talked at a neighborhood meeting in Brussels, about comets I think. Probably in 1950.

Weart:

Right. But I mean, this was the first time you'd talked about your spiral structure work.

Schmidt:

Yes, that's right. I went to, I think, two conferences in Jodrell about radio astronomy in '54 or '55 or so.

Weart:

I see. It must have been an interesting meeting because people point to it as being one of the places where radio astronomy had clearly been established.

Schmidt:

Yes.

Weart:

Do you remember the size or character of these meetings?

Schmidt:

Yes. Not very large. People like Hanbury Brown were there and Smith who had given this beautiful, highly accurate determination of the position of Cygnus A. I would also not be surprised if it was in this first or second meeting that the first evidence came up that Cygnus A was, in fact, not a radio source that sort of covered the galaxy but that rather, it was two sources away from the galaxy. — which was quite a revelation.

Weart:

This was one of the first places where radio star statistics began to be discussed.

Schmidt:

I think that was true too, yes. Yes.

Weart:

Perhaps it didn't make too strong an impression at that time?

Schmidt:

Well, we were somewhat distant from it, but very interested. I did feel that when I went to that first meeting in '54, I think that it was sort of like the beginning of radio astronomy. And I must say, I made a conscious decision when van de Hulst asked me at Leiden, did I want to go? (Or I may even have asked to go.) I felt that this was indeed a step. I was going into radio astronomy, as it were. It was clearly that. It was to be sort of the beginning of radio astronomy in Holland.

Weart:

You saw it as a coming field, and thought that you might become a radio astronomer.

Schmidt:

Yes. Which of course I was, for a while. And my subsequent interest in radio astronomy has not really subsided.

Weart:

No, you've always kept two feet in it.

Schmidt:

Yes.

Weart:

Well, before I forget to ask you about these meetings —local meetings — were there a lot of local meetings?

Schmidt:

Oh, yes, they have a club as they called it, the Neederlands Astronomen Club, which meets I think two or three times a year nationally at various places. But this neighborhood meeting [of ca. 1950] was one, I think, for the Benelux countries, or whatever. It was held in Brussels.

Weart:

Did you get to the Neederlands Astronomen Club meetings quite regularly?

Schmidt:

As a student, yes.

Weart:

This was an important thing for people to go to?

Schmidt:

Yes. That's where I would hear people like Minnaert, who was of course a very great lecturer and others.

Weart:

OK. To get back then to the 21-centimeter work, the distribution of mass and the dynamics, that problem, was this your thesis project?

Schmidt:

Yes.

Weart:

I see. How did it happen that that was your thesis project rather than something else? Could not the spiral structure have been your thesis project?

Schmidt:

Yes, it could have been. I cannot exactly way why the one became it and not the other one.

Weart:

Were they begun simultaneously or did one follow the other?

Schmidt:

No, I think the mass distribution was started later. But the decision as to which was to be the thesis subject — I cannot say how it was taken. We may have felt that this spiral structure business was somewhat difficult as a thesis subject, because one would give reports about it several times, you know, at meetings — even the preliminary thing was probably shown at some meeting. I can't say.

Weart:

Again, this was a problem that came out of discussions with Oort?

Schmidt:

And this work on the central part of the galaxy, I think, is also always putting models together but not too much pure theory.

Weart:

At Leiden, was there any feeling that there were theorists and there were observational people?

Schmidt:

Yes. I think that was right. People like Oosterhof and Walraven were very much more observational; they always did observations. And, although one would perhaps not call Oort a pure theorist, nonetheless, I think one would view him and he would view himself as a theoretician.

Weart:

And what were you?

Schmidt:

You can either ask me what I was or what I am. And I think I haven't changed very much. I think I'm rather on the observational side but not limited to that. I think I feel rather strongly, since you mention this now, that certainly in astronomy, you cannot separate people into theorists and observationalists only, but that there must be an in-between type of people who interpret, integrate, and — what shall I say? — explain the observational evidence 'what radio astronomers now do with their maps) to where it is 'clean.' Raw observational data are nothing that has any impact, really. Or can only be misinterpreted by theoreticians and vice versa perhaps. My work on quasar distribution, in fact, does almost nothing but squarely discuss and face selection effects — which usually, of course, are sort of said to be, 'Well, there may be selection effects, but we'll hope they're not too bad.'

Weart:

Whereas you rely on selection effects.

Schmidt:

Yes, and I try to be so systematic about them that one can discuss them, in effect, accurately. So I think a third type of person is needed and that is where I find myself perhaps best at home. But it often leads to observational evidence or methods or materials that one wants — because when you do this so-called cleaning up you say, 'Oh, we need this, we need that complete sample.—' So that's how I determine my observational program.

Weart:

I see. To get a good sample.

Schmidt:

That's right. I'm somewhere in that 'between' position — or between that 'between' position and the observer, I think, because I do observe.

Weart:

I see. If you were in a place that didn't have large telescopes, perhaps you'd be recommending to other people observational programs to follow?

Schmidt:

Yes. Who know?

Weart:

Before we get to your move here, a couple of other questions. You were still doing comets I notice and you did something on molecular bands with van Woerden.

Schmidt:

It was that same program that I started early and van Woerden took it over; we may have written a joint article about whatever results came out.

Weart:

I noticed that you continued to have some interest in comets. In fact, there's a picture of a comet on the wall over there. Which at first, from a distance, I thought was some peculiar galaxy with a jet, but I see that it's actually a comet.

Schmidt:

Yes. That was not done by me. I was given that picture.

Weart:

You have written a paper now and then on comets?

Schmidt:

Not since that time, really. No.

Weart:

I see, so it hasn't been a real continuing interest?

Schmidt:

Well, I must say I'm somewhat interested in them, but not as an actual research activity. I might say 'which is sort of anecdotal) that the last time I got involved with comets, unofficially, was when I saw the prediction for Comet Kohoutek which was supposed to become exceedingly bright. And when I saw that announced in the cards, I realized that the predictors had not taken into account this work that I'd done with Oort in 1951 or so.

Weart:

It was a new comet.

Schmidt:

It was a new comet. It had a very large major axis, perhaps unmeasurably large, you know, close to zero, and I realized they'd taken a steep rate of increase of brightness with solar distance, the usual steep thing like with Comet Encke. And I realized it was much too steep.

Weart:

I see.

Schmidt:

So I devised a revised prediction of the brightness. But I wondered what to do with it.

Weart:

Announce it to the daily news?

Schmidt:

Public expectation had been raised to such a degree that anybody who would come out and say that it wasn't right would probably be considered a spoilsport. Moreover, I had no assurance I'd be right anyhow.

Weart:

Since, in fact, they're not completely consistent, these comets, anyway.

Schmidt:

That's right. There are always variations among them. However, I thought it was badly overdone. I called Marsen about it, or explained to him or wrote to him what I thought was wrong. I did two things. One is, I talked to Marsen, and he may have put in the cards a statement — I don't know. He may have referred to that publication in the cards, suggesting that the brightness might be rather lower. I'm not sure. I also called Carl Hennays of the astronauts office because they were counting for their program in whatever was flying, Apollo X, an extensive program. I told him that I thought that the thing would be, oh, more than five magnitudes fainter, and he might keep that in mind. And he thanked me. And it wasn't bright, of course; it wasn't bright at all.

Weart:

Yes. Well, let's see, anything else we should talk about, for the Leiden period, before we move on to Mt. Wilson-Palomar?

Schmidt:

No. That's about it.

Weart:

One question on personal life — you married Cornelia Johanna Tom. What was her background, her education, when you met?

Schmidt:

She was a nursery school teacher. She was educated for that in Leiden at some fairly progressive school over there to which her grandmother had also been so it cannot have been that progressive. I actually met her at the observatory. The ladies of the observatory once got it in their heads that they wanted to give a party for the people at Sternewacht 2 who were the bachelors, the graduate students.

Weart:

Who wee the ladies?

Schmidt:

Oh, Mrs. Oosterhoff, and Mrs. Sieger, 'Carl Sieger was at that time at the observatory for a very long stint) and Mrs. Walraven, I think. They wanted to give us a party. And we said, 'Oh, not a party, we don't even have girls.' You know. They said, 'OK, we'll supply the girls.' It would be interesting to hear my wife's story on the other side of this. But anyhow, there were some girls, and believe it or not, one of them was her. Which gives entirely the wrong impression about her, I might say.

Weart:

It's a perfectly neutral impression. Does she have any separate career?

Schmidt:

She had I think just started then as a nursery teacher and kept doing that until we left for America in the middle of '56.

Weart:

Tell me again one of these questions that I ask everybody. How do you think the fat that you're an astronomer has affected your marriage, your children and so forth?

Schmidt:

I think rather little. My wife would complain that I'm away fairly often. These are of course mostly observing runs. But I would think it's not a lot more than other men are away from their families for travel or whatever.

Weart:

Yes, my wife complains that I'm away right now.

Schmidt:

Of course. Yes, I bet you. So I would still maintain that it has rather little effect, I think.

Weart:

OK; so then you came to Mt. Wilson-Palomar as a Carnegie fellow in 1956. How did that come about?

Schmidt:

Oort had written to probably Baade, although it may have been Bowen or both. These days, that goes by application. In those days, it went by that system; Oort wrote Baade and I was offered a fellowship.

Weart:

Why did he feel that you should come to Mt. Wilson? Just for the experience?

Schmidt:

Yes, I think so. He probably felt, wisely, that it would broaden somebody's astronomical experiences to do observing at the larger telescopes. But he may have seen something else in me, I don't know. He would not just do that for everybody. Let me think — in that period of time, I really think I was the only one that he sent here.

Weart:

So he had somehow noticed you.

Schmidt:

I'm sure. Yes.

Weart:

All right. Well, then, when you got here — there's a whole lot of questions. In the first place, before you even left, how did you perceive American astronomy? What was your image of it?

Schmidt:

Uneven. The work at the largest telescopes, of course, drew a lot of attention and was so unique that it got attention quite often. And, I think it was also felt at Leiden — since people like Oort and van de Hulst were so exceedingly critical — that certain other work done by some, American astronomers was of rather low quality. So, I think the impression was uneven. But of course, the really important feature was the work done on the large telescopes.

Weart:

So. Mt. Wilson was really seen as one of the places to go?

Schmidt:

Yes it was.

Weart:

And then, after you came here — there's two sides. One is what your initial impression was when you got here and the other, thinking back now, what the differences were between ——- [Added later] Anyone specific? I'm particularly curious as to how Hubble, Shapley, and Russel were seen at Leiden, although of course that's a bit before your period. Leiden and here. That has two sides. One is America versus the Netherlands, and one is simply Mt. Wilson as compared with Leiden.

Schmidt:

Yes. Well of course the big difference between there and here, that is Mt. Wilson, was that at Mt. Wilson each of the astronomers was a rather strong individual with his own program; one didn't have the impression that one person was sort of guiding things. Each of them seemed to be — well, perhaps a prima donna, without the bad association that might go with that word. Each of them as an authority.

That might not go for absolutely all of them, but it went for most of them. And that was quite a difference with the situation in Leiden, where Oort dominated strongly, and van de Hulst was also quite good and somewhat independent, but that was it. In a sense, that does describe in general also a little bit, I think, the difference between American and Dutch astronomy. But it's not an independent statement because Dutch astronomy is so much dominated by Oort and by Leiden. But at that time, for instance, you would also find at Harvard and at Yerkes a number of people who were all very individualistic, and who went their own way — would often fight with each other too.

Weart:

I have a feeling that Yerkes and Harvard, in that period, perhaps more revolved around one person than Mt. Wilson would have.

Schmidt:

I don't think so about Yerkes. This was in '56

Weart:

Oh that's right, it's already '56. I was think of —

Schmidt:

— right — remember, around that time, the Yerkes directorship changed almost every year —

Weart:

Right. No, I'm sorry, I was thinking of a little bit before when Struve was still there —

Schmidt:

— Stromgren and Morgan.

Weart:

Yes, you're quite right.

Schmidt:

I think, for instance, we have here at Cal Tech again the same situation, where each of the astronomers is an independent sort of authority, and there is no guiding overall force. As long as that work, it's fine. So that's quite a big difference, I think. But it had as much to do with Oort's leadership and dominance as with anything else.

Weart:

I see. What about contrasts in the social environment, the way people would get together or the way things would happen?

Schmidt:

Not a big difference. People in Holland were not used at all — although they've changed a bit since that time — to go to dinner. They don't go to dinner there; they would get together for the evening, perhaps, if they did, but not for dinner. Dinner was not used there as a social contact, as a social event. Whereas here, especially at that time, it was very prevalent. But, except for that, I think social contacts were somewhat similar. Perhaps a bit more intense here than they were there, I think.

Weart:

Closer personal relationships?

Schmidt:

I'm not sure about that but there was more social contact. Whether the personal relationships were really closer, that might or might not be the case.

Weart:

That's a different question.

Schmidt:

Yes.

Weart:

What else struck you when you came here?

Schmidt:

I think the obvious thing. The possibilities with the telescopes were extraordinary. But we don't have to go into that, since you know. I don't know. What are you after, things outside astronomy too?

Weart:

Things having to do with the way astronomical research was done. I really don't know what I'm after.

Schmidt:

OK. No, astronomy is a pretty international science as far as that goes. When you have been at one center that is active, even though perhaps in a limited part of the science, and you go to another center, you do recognize that kind of activity there again, though in perhaps different fields.

Weart:

Was there a difference in the style of research, the way of going about doing work?

Schmidt:

Not terribly different. If anything, it was more thorough in Holland. Things once in a while might be published from here that in Holland would have been investigated further, or more thoroughly, but then there was much more — the enormous amount of material that becomes available from a place like this makes it imperative to keep moving too.

Weart:

Did you have a feeling that one of the things that was going on here was simply accumulating material, accumulating data?

Schmidt:

Yes. And that was an impression that we knew in Holland about this place. I think that, at Leiden and also perhaps at some other European observatories at that time, people sort of felt that it was partially their role to interpret or to attempt the interpretation of what was observed at places like this. Now, in some instances, that might have been a sort of self-grandeur that they felt; here in Pasadena they will make the observations, we will interpret it for them. But in some cases, I think it was perhaps justified to feel that way. It was indeed true, especially before radio astronomy, that people over there had the leisure to think deeply about things, while people here were and always are pressed by enormous possibilities. These days also by instrument development and what not.

Weart:

Certainly there was a feeling in American that you couldn't let these big telescopes go a day without observing something.

Schmidt:

That's right.

Weart:

And perhaps in Leiden there wasn't that same feeling?

Schmidt:

Well yes there was that same feeling because even the medium-sized or small-sized telescopes that were there had to be worked every night. Oort would regularly check whether we were working them. For a good reason: while over here you are assigned time, there's a schedule you go there, you stay up on the mountain and things like that, over there it was in the middle of the city. So you had a social schedule, you would go somewhere. Then you had to find out, sometimes by calling back, whether the weather had improved; its very variable in Holland. So once in a while you could, you know —

Weart:

I see. You might be sitting there and the sky had cleared.

Schmidt:

Yes, it has happened. So there is little bit of that role that European astronomers I think, at that time, some of them, felt they had, in thinking about what was gotten in places like Pasadena. I don't think that they have that feeling any more, to that degree.

Weart:

Why? Because they have their own telescopes now?

Schmidt:

Partly because they have their own telescopes and radio astronomy. It may be because people at that moment who are over here, some of them at least, have quite a lot of theoretical insight, and therefore do manage, in the first round, to expose what is theoretically important. I don't know.

Weart:

At one time, some people had the feeling that if you analyze a set of observations, you should go back and sort of replenish the stock. If you use up some observations, you should go out and take some more for the next generation. Was there any of this feeling?

Schmidt:

Where, at Leiden or here?

Weart:

Either place.

Schmidt:

Over here, I think that whole concept would not make sense. Because almost all the astronomers here observe a lot, so that they certainly add to the observations much faster than they use them up from previous generations. No, I don't have that feeling. In Europe people were powerless, as it were; they might use up observations of the past, but — The only place w here perhaps this played a role was, I would think, in astrometrey. There it makes sense to think along those ways, because if you do second epoch plates for proper motions, and you determine these proper motions, you come out with membership of the Hyades or so — I think it's natural that you think, 'Hey, what about the future? I've used these first epoch plates from 1915 or so, what's going to be done in the year 2000?' And therefore you would plan ahead, and take some first epoch plates for proper motions and things like that. I don't see that much, in astrophysical things.

Weart:

OK. To get back more specifically to Mt. Wilson-Palomar, there had been in the thirties some distinction between the spectroscopist and extra-galactic people. Did you notice any division like that by the late fifties when you were here?

Schmidt:

Perhaps just barely, although it was going or had just about gone, I think. I'm sure that people like Paul Merrill, Joy, Sanford, and some others were indeed spectroscopists. Yes, I think, now while I'm thinking about it, that I have to re-interpret what I thought you said. It is still there, of course. But at the moment, it is perhaps more clearly put as: people who can work in dark time, versus those in light time. Light time would be spectroscopists who use the Coudé or relatively bright stars. But these days you have to add infra-red people to them, where you go for the faintest galaxies or quasars, that are so faint that you are really bothered by any extra lights. So the distinction still lives on, but it is changing its shape slowly, a little bit, I think. You see, the — what did you call them? The people who did galaxies at that time?

Weart:

Extra-galactic people.

Schmidt:

Extra-galactic work — yes. They did of course, mostly, at that time, direct photography, isn't it so? Baade? Although Minkowski of course did mostly spectral work.

Weart:

In any case, they were at the prime focus rather than the Coudé.

Schmidt:

Yes, right. So I think it's changed into dark and light.

Weart:

What were you? Were you a prime focus person, a dark time person?

Schmidt:

Yes, I was immediately dark.

Weart:

Were you attached to anybody or were you sort of a floating fellow?

Schmidt:

I was sort of floating. If I was attached to anybody, I think it would be to Baade. I had written Baade before I left about certain programs I could do [asking] his reaction to it. And to everybody's surprise in Leiden, I got a reply from him. You know, Baade never, never answered his correspondence. The observational work I did as a Carnegie fellow was totally unsuccessful.

Weart:

What did you do?

Schmidt:

There never was anything published from it, or hardly at all, and it was a complete failure. I can say that now happily.

Weart:

May I ask what it was?

Schmidt:

I thought it would be interesting to check on certain things having to do with the rotation of the galaxy, especially the outer part of the rotation curve, by finding very distant open clusters. Getting their distance from the usual photometry that was then very current, UBV and so on, Johnson-Sandage methods, etc. — and then to get radial velocities and see how it checked with the rotation curve. The program never really worked out for the clusters. I had particularly bad luck with weather.

I had trouble with transformations into the UBV system. I never finished the work and I never published it. One of them, NGC-6939 got pretty close to finished and I may have talked at an ASS [American Astronomical Society] meeting about it, I think. But even that was never published because I was unhappy about the final accuracy of the photometry. I got a different reddening from the giants than from the main sequence stars. I think that it later was soon rediscovered as being due to the ultraviolet excess of certain clusters. And I didn't quite catch that at the time, I didn't publish it.

Weart:

Now, you must have had just a few nights?

Schmidt:

Not a few. I got quite a few nights at the 60 and the 100 inch telescope. I didn't get any nights at the 200 inch.

Weart:

Was this through Baade? You asked Baade for them?

Schmidt:

No. Fellows could get nights at the 60 and the 100 inch telescopes.

Weart:

By application.

Schmidt:

Yes. They could not get time on the 200 inch. That simply was out of the question.

Weart:

I see. Did you also attend classes here, that sort of thing?

Schmidt:

No.

Weart:

Strictly working.

Schmidt:

Yes. The other thing I undertook was this business about the effects of star formation, or rather, the effects of star formation on the interstellar medium, and the gas.

Weart:

This is the question of the initial luminosity function?

Schmidt:

Yes.

Weart:

I was going to ask you about that in more detail.

Schmidt:

I took that up over here, in fact, during that time. In the middle of my fellowship, which lasted two years, yes.

Weart:

I want to get back to ask you how you got into that, but first a little more on the non-scientific side. I'm not quite clear how you went from the fellowship to becoming a permanent staff member here.

Schmidt:

I went back to Holland.

Weart:

You went back to Holland after your fellowship ended.

Schmidt:

Yes. In fact, I was asked by Cal Tech to become an assistant professor in astronomy.

Weart:

While you were here?

Schmidt:

At the end of the fellowship, yes.

Weart:

By whom? By Greenstein?

Schmidt:

By Greenstein and by Bacher, who was at that time the division chairman and who sat over there.

Weart:

Oh in this office?

Schmidt:

This desk was over there and I sat over there and Jesse [Greenstein] sat over here, and he sat behind his desk and faced this way.

Weart:

I see, so he was in the southeast corner of East Bridge, in fact.

Schmidt:

Yes.

Weart:

But you told them no?

Schmidt:

Yes, that's correct.

Weart:

So you went back to Holland, to what?

Schmidt:

I had an allegiance to Holland at that time, especially to Leiden. I felt I couldn't step out. It had certainly not been the idea, when I left, that I would just leave forever. So I went back to Leiden.

Weart:

Did you have a post there?

Schmidt:

Yes. I was, in the beginning, Adjoint Scientific Officer. The very lowest position you could possibly think of.

Weart:

What did an Adjoint Scientific Officer do?

Schmidt:

Just whatever I did, you know — work hard and earn little.

Weart:

I see. But again, you were free to do your own research?

Schmidt:

Yes. I had no teaching. It was a research position, quite right.

Weart:

I see. And what sort of future did you have in front of you, there in Holland?

Schmidt:

After I was an Adjoint Scientific Officer, I did in fact become a Scientific Officer.

Weart:

Which is the same thing only a little more pay?

Schmidt:

Let me be sure of the historical accuracy of all this, because I wonder, I have to watch it here— I may have become an Adjoint Scientific Officer while I was still a graduate student. W; On your World Who's Who in Science entry, you have yourself as Scientific Officer at Leiden in 1949; maybe that's what the assistantship was called?

Schmidt:

That's a bit generous; not really. I think that in '53, at the end of the assistantship, I probably became already Adjoint Scientific Officer.

Weart:

I see.

Schmidt:

And then a couple of years later, or when I got my doctorate, I probably became a Scientific Officer. Then I think when I came back to Holland, I became Scientific Officer First Class.

Weart:

I see. All these things are precisely the same except some have slightly less inadequate pay than others. Is that right? No duties other than to do your research?

Schmidt:

That's right. So then, while I was in Holland — although I'd like to get back sometime to this star formation thing —

Weart:

— we will —

Schmidt:

When I returned to Holland, I got a feeler from here, after about a year, I think. It must have been very early. I returned in May '58; perhaps late in '58 or early '59, I got a feeler. I'm sorry I never asked him before he died, because it was a ruse. Minkowski wrote me a letter in which he wrote that he had recently seen Lindblad — Lindblad Sr., of course — and Lindblad had told him that I was interested in going to Pasadena after all. And it was an out and out lie because I hadn't seen Lindblad since I came back. Also Lindblad was not typically the person with whom one would discuss things like that. You know, he was a very senior astronomer, very staid; I would not have discussed it with him anyhow.

Weart:

So Minkowski either was mistaken or made it up?

Schmidt:

No, he made it up, I think — I'll have to ask Jesse [Greenstein]. But I think I've asked him, and he is not sure. Of course Rudolph [Minkowski] died. Apparently this was well chosen, that moment, because we were wondering. In fact, on my salary we were losing money. We had to go in a rather expensive apartment because of the housing difficulties in Holland. I think I was losing money at about the rate of 5 or 8 percent of my salary per year and things were tight. Also, after a year in Holland, things apparently seemed to look more attractive on this side. I did indicate to him that he might be right so I soon got a letter from Jesse Greenstein and offers were made. I thought quite a while about it. And I finally was appointed as associate professor of astronomy starting in October or September '59.

Weart:

Completely on the Cal Tech side?

Schmidt:

Completely on the Cal Tech side but also at the same time [I was] a staff member of the Mt. Wilson-Palomar Observatories which is this joint thing we have with Carnegie where from either side, we are appointed as staff members.

Weart:

But your salary came from the Cal Tech side.

Schmidt:

Entirely, yes. So I became associate professor in '59.

Weart:

I see. Did you feel a joint loyalty? Or did you feel a loyalty primarily to Cal Tech? I'm never quite sure how it works out when you're a member of two organizations.

Schmidt:

At that time, I was mostly interested in going back to Pasadena. I remember I wrote Bowen who was then director of the Santa Barbara Street office [location of the Carnegie Institution staff] — and of the Mt. Wilson-Palomar Observatory as a whole — I wrote a letter to Bowen asking him whether, in case I were unhappy at Cal Tech, which I didn't know too well at that time, there was any possibility of transferring to Mt. Wilson. And he wrote a slightly non-committal letter back at that time. Ironically, by the way, the only way I have achieved this is by now becoming director of the place; I will in fact be half paid [from], and have an office half time at Santa Barbara Street. Through this funny road I've made it — if I ever wanted it. 'Laughter) That's a devious way of getting back to the Carnegie Institution.

Weart:

Well, again, before we get to the past rate of star formation, I'm curious about your first few years here. For example, what courses did you teach? Were there some that were particularly important to you?

Schmidt:

I taught soon an introductory course, very general, for sophomores. The freshman course here is culture. And, it happened to be given by somebody else — I think Jesse used to do that. So, I was involved in the teaching of sophomores. And also in graduate course, I gave in the beginning the galactic structure and dynamics course, and I gave essentially the first course in radio astronomy here — since there was no radio astronomer here who had any teaching assignments. The people that were here then were Bolten and Stanley.

Weart:

Who were completely non-teaching types.

Schmidt:

That's right.

Weart:

You volunteered to teach this?

Schmidt:

Yes, it was arranged and I thought it an interesting challenge. I did it quite a number of years, until Alan Moffett took over, when he became professor of radio astronomy here.

Weart:

By the way, do you in any sense see yourself as a radio astronomer?

Schmidt:

Well, a slight bit really. Because even though my work for instance on quasars has been aimed at the optical properties — red shifts, emission lines, whatever — nonetheless I've kept very close contact with what's going on in the radio astronomy, especially in that field. For instance, I found two years ago, as you may know, that the cosmological evolution, density change, of quasars, is in fact different for those different radio properties. Steep or —

Weart:

Right, flat spectrum and so on—

Schmidt:

— So, although you might say that doesn't make you a radio astronomer, and it doesn't, nonetheless I am very aware of it.

Weart:

I guess the reason I asked is because at one point, you almost made a decision to be a radio astronomer.

Schmidt:

Almost.

Weart:

But there never was a decision back, away from it?

Schmidt:

Well, perhaps taking the position here at Cal Tech was the step out of it. Because if I'd stayed in Holland, I'm sure I would have sort of been drawn into the radio astronomy work which was proliferating, of course, eventually with the Westerbrook installation, it became very interesting and very vigorous.

Weart:

So you recognized this at the time?

Schmidt:

Yes. On the other hand, Cal Tech did have radio astronomy at that time. In '59 when I came back, it had been going on for a few years. In fact, one of the first things I did when I came here was to get involved in the determination of red shifts of radio galaxies.

Weart:

Yes, I want to get back to that too. All right, just a couple of other questions then about when you were here, through the sixties and so forth but particularly the early time. How much of your time would you say was spent on research, how much on teaching, how much on administration?

Schmidt:

In administration, almost none. In teaching, it was usually three hours a week throughout the year, and it must have taken in total on the order of, say, eight hours per week; so perhaps 20 percent time on teaching. If you include student activities in general, like supervision of theses and so on, perhaps it was 25 percent. On that order, throughout a year, 20-25 percent, and the rest on research.

Weart:

I see. Did you keep any particular hours? Your daily schedule?

Schmidt:

I think in the early days I came here fairly late, like 10 o'clock, perhaps 9 or 10 o'clock and would often work at night, also in the office, perhaps. Although not after we came back, because we soon lived in Altadena which is six miles up.

Weart:

So you got on a more regular schedule.

Schmidt:

Yes.

Weart:

What about at Santa Barbara Street? What sort of hours did people keep there?

Schmidt:

I think they came in not too terribly early, and probably worked on the average somewhat late. I remember in '56 till '58, when I was there, that both Sandage and I kept typically the hours of between......

Weart:

Again, asking about the atmosphere, both around here and Santa Barbara Street —— in the first place, how much contact did you have while you were here with Santa Barbara Street? This would be up through the sixties, let's say.

Schmidt:

Quite a bit, with individuals — like Sandage and Arp. With Kraft, while he was there; Kraft and I did some work on Cepheids in the early sixties.

Weart:

Where and how would you get together with these people?

Schmidt:

Usually going there, or they come here. Somehow people seem more often to go over there. And just talk to them.

Weart:

Was this in general how people would get together to exchange ideas about research, just an individual would go one place or the other?

Schmidt:

I think so, yes.

Weart:

What about seminars, colloquia? Any particularly important ones?

Schmidt:

There is a Wednesday seminar which is held here, and which is, in a formal sense, a joint one between them and us. Our involvement is rather deeper— also because there's lots of Cal Tech faculty not in astronomy and students who attend, so it's a somewhat asymmetric affair— but it's supposedly the joint seminar between the two groups.

Weart:

What about the Physics colloquia? Do you go to that sort of thing regularly?

Schmidt:

At the moment I go quite regularly but that has to do with my present position.

Weart:

Right. But in the sixties, let's say.

Schmidt:

In the sixties, off and on. I would perhaps go to every fourth or fifth colloquium or so.

Weart:

Would this be fairly typical of the astronomers around here?

Schmidt:

No, in general I think they go less. But it varies a bit. [Brief interruption].

Weart:

What about other things, informal seminars, groups, people getting together in some regular way?

Schmidt:

The staff will get together. I would say mostly through things like meetings about instrument development or so. Especially with the Las Campanas telescope. That happens quite a lot, that certain groups came together to discuss instrument design and building. There are sometimes staff meetings or staff lunches, perhaps six to ten times per year or so. There's an observatory committee that's fairly large, eight people, so that's another basis for contact.

Weart:

What about lunches at the Athenaeum [CalTech Faculty Club]?

Schmidt:

On Friday there is a lunch at the Athenaeum that is attended sometimes by 40 to 50 people. Again, it's somewhat asymmetric. There is less involvement in these things that happen over here on the part of the Carnegie people, than there used to be when Baade and Minkowski would come.

Weart:

It's changed since you first came here?

Schmidt:

Yes. There has been less involvement from that side. That may perhaps change again in the future.

Weart:

What about this SINS seminar? Did you have anything to do with those?

Schmidt:

Yes. I sometimes gave one and went to many of them. It was set up by Willy Fowler's group. For Stellar Interiors and Nuclear Synthesis. It became a good theoretical — you know, cosmological — type. Not in the narrow sense, but in the broad sense, anything having to do with the nature of galaxies, stars, element formation, isotopes, meteorites, aimed at chemical evolution perhaps, nuclear evolution, but as broad as necessary. It was very interesting, I think.

Weart:

How much interest have you had in these questions of, particularly, chemical evolution and stellar evolution and so forth? Do you follow those things closely?

Schmidt:

Yes. My interest and my activity in this business, on the effects of star formation, started I think in '57. I think it was in '57 that I attended an AAS meeting in Cambridge, Mass and had lunch with Sidney van den Bergh who asked me about everything that was happening in Holland with the galaxy and the 21-centimeter work. He was interested in the fact that we had known but had not thought about it hard, that only a small fraction of the mass of the galaxy seemed to be left in gas form. Soon after the conversations with me, he published a paper in which he said that in about one or two billion years, it's going to be all over. Because it started all with gas, and now there's only a few percent left, and you extend that and you'll find a zero percent in a few years, as it were.

Weart:

Right, I see. So you heard about this directly from him?

Schmidt:

In fact, I informed him about the state of the gas content in the galaxy. Then he wrote a paper in which he made this claim, that things [star formation] would soon be over.

Weart:

I see, so he was concerned about this problem.

Schmidt:

Yes, that's right. He started it. And as soon as I saw his paper I was irritated because I thought it was ridiculous. And I still think of course it's ridiculous. You see, the decline in the gas content has to do with the rate of star formation.

Weart:

I see. You mean, in his paper, he seriously proposed, not that there was some problem, but that in fact it was going to be all over—

Schmidt:

Well, let's say he said there was a problem. But anyhow, he just stated it in his paper. It irked me a bit. But only then did I see what he was after and I thought that had to be all wrong. I thought, well, the rate of star formation of course depends on the amount of gas there is. You cannot just run out, like a car.

Weart:

Right.

Schmidt:

So I soon wrote a paper myself in which I essentially went the other way and said: 'Let's say the rate of star formation is some power of the gas density.' And at first, at least, it has to be first power: No gas, no starts. That gave rise to this paper; I think it was published in '59. At any rate, almost in the meantime, Salpeter did his work, which came out somewhat earlier, I think, on the initial luminosity function.

Weart:

Right, that came out in '55.

Schmidt:

Oh, in that case I must have known about it, of course. But he also wrote a paper in '59 which was published almost adjacent to mine, I think. The Salpeter luminosity function had existed since that time, indeed, but he also had a paper about the rate of star formation etc. — I think it was adjacent to my paper — and we came to fairly different conclusions. But anyhow, as you may remember from that first paper, I then felt that the power of two would fit better with certain aspects of the observations than power one. Namely that the rate of star formation went with the second power of gas density.

In '63, just around the time of the discovery of the red shift of quasars, I had a second paper. I made things in more detail and discussed especially the evidence, as far as chemical evolution was concerned [for] the rate of change of metal abundance and how many G-type dwarfs should be of low and high metal abundance. I then hit a problem that I tried to resolve by making the rate of star formation a different power of the gas density for different masses of stars. By that time I realized that things became so complicated that I got disenchanted with the field and didn't work in it again.

Weart:

That's just what I was going to ask you about.

Schmidt:

Yes. That's exactly what happened.

Weart:

Because it was getting so complicated.

Schmidt:

Yes.

Weart:

I'm quoting from your paper: 'Choice of a particular form is quite arbitrary.'

Schmidt:

Yes.

Weart:

What I'm particularly interested in is this: The question that the evolution of the solar neighborhood may have been strongly coupled to the evolution of the central parts of the galaxy, in which case it gets much more difficult.

Schmidt:

Yes, indeed. Because I had to assume that it was a closed box or a closed cylinder, otherwise—

Weart:

— right. I'm intrigued with this whole question of the possibility of stuff moving around in the galaxy. Right back at the beginning, there was the question whether if the gas seemed to be used up, it might be replenished from the nucleus, or something like that.

Schmidt:

Yes, right.

Weart:

That was van den Bergh?

Schmidt:

It's quite possible that he said that, yes.

Weart:

Now, I just wondered whether both, at Leiden, even before you left and so forth, and then here, was there some general feeling among those people, from the 21-centimeter observations, that there was a lot going on in the galaxy, that there was activity, there was a moving thing? If you go back to the thirties or whatever, one just sees the galaxy as a collection of stars, in a sense.

Schmidt:

Yes.

Weart:

And then somehow, around this period, there is beginning to get a feeling that gas was in falling here and coming out there and so forth. Do you recall any development?

Schmidt:

No. No, that was not very strongly realized, I think. Around that time, the 21-centimeter people used velocities to get distances from the galactic rotation effect. Therefore, most of their concern was as to whether there were substantial deviations from circular motion. There was one case where, also, through Guido Munch's work here, it had been shown that there were cases where there were big differences, big deviations.

Guido found it as follows: in the direction of Perseus, Guido found that there were interstellar absorption lines in stars that had a bigger negative velocity than the stars themselves. This is the direction in which the galactic rotation effect gives you negative velocity, and it better be about half the amount, of course, interstellar absorption—

Weart:

Because on the average it's half as far—

Schmidt:

— yes, yet it was larger. And that concerned us very much. And we also saw on our maps in that direction in Perseus, funny structures; the velocities must be affected. And then many years later it was found that it was perhaps even a shell. At that time, no, there was not that impression of violent things happening with the gas, that one now would have. No, that was not at the center of attention.

Weart:

I see.

Schmidt:

I was thinking at the time I said that, of course one had to assume here that the solar neighborhood was a closed entity, as it were. I was more thinking of relatively slow, secular drifting around of stuff, rather than real outbursts and things like that.

Weart:

Still, when you announced this stuff in a colloquium at Liege in 1960, you certainly seemed very excited by what you had found about star formation.

Schmidt:

Yes.

Weart:

But you mentioned, by 1963 it seemed very complicated and difficult.

Schmidt:

Yes. In 1960 at the Liege Colloquium, I was probably the most optimistic. I gave curves of how X, Y and Z should change throughout the galaxy, I believe. I may even have come up with a statement about how in the halo, you could understand this or that. It was the most positive moment; my confidence peaked. After that, I got less and less impressed by the reliability of these considerations.

Weart:

Also, there was the question of the depletion of hydrogen. One result you came up with was, that one possibility was that the primeval gas may have contained quite a lot of helium — because otherwise, how could you explain that there was no helium gradient in galaxies.

Schmidt:

Let me specify that. You see, the prediction I did make in Liege in this paper of '60, which was a '59 conference, was that there had to be a helium abundance gradient. One of the first jobs I did here, in fact, and that was with the 200-inch, was to try to find that in nearby galaxies, because it seemed easier to check in nearby galaxies over their face rather than in our own galaxy. I concentrated especially on the Andromeda Galaxy, and took some very long exposures with the 200-inch, interior ones there that in fact required three nights of exposure for one spectrum.

And the results that I got were that there was no change in the helium to hydrogen abundance ration, over the face of the galaxy. I remember when this became clear — that was while Fred Hoyle was here — that we had discussions about the interpretation of all this. It was not long after that, I think — I'm not sure about it, but at some time, they came up with the claim that you would always expect from a Big Bang 27 percent or so helium. I'm not sure about exactly when they started to claim that. Now, that observation was not absolutely reliable because I had to make assumptions about the size of the helium ionization region.

Weart:

Did you see this as having any effect on cosmology? I notice that you also did some work on the distribution of mass in M 31 — you talk about the mass to luminosity, you know, the M/L ratio, and so on. Were these things that were beginning to interest you at that time?

Schmidt:

Yes; but mostly because, after the model of the galaxy I had done, it seemed a simple extension, when a good rotation curve for Andromeda came up again from Holland, to use the same technique in order to get a model for Andromeda. There was at that time not a notion that if you got a good mass for a galaxy, you were doing cosmology. It's of course with the bigger masses these days that you get if you take the flat rotation curve and/or the massive haloes that a discussion of the mass of galaxies seems to have a direct effect on cosmology because you're getting close to a total mass of the universe where you can slow the thing down. With the masses at that time, that was not the case.

Weart:

So your program then was still essentially just understanding one galaxy?

Schmidt:

That's right. It was more an isolated clean-up, since it could be done — connect the light and the mass distribution of Andromeda.

Weart:

But did you feel, as you mentioned Hoyle was here and so forth, that when you came up with something, there were cosmologists hovering around ready to pick up what might be of interest?

Schmidt:

That helium finding, I realized, was of cosmological or cosmogonic importance. Because as we immediately discussed, one of the possibilities of course was that it had always been around — because it seemed crazy that in the interiors and the exterior parts of galaxies, you could get so precisely the same, when the total rate of star formation had been so different.

Weart:

One other question and then maybe we should break for lunch before we get into the radio galaxies. I suppose this was one of the first things you did with the 200-inch, looking for these?

Schmidt:

Yes.

Weart:

And with very long exposures?

Schmidt:

Yes. Much longer than I would wish to take in these days.

Weart:

What was it like to go up there and use the 200-inch?

Schmidt:

Oh, fantastic! It was an experience. It's a type of experience one doesn't have any more these days because I don't sit in the prime focus any more. We moved to the Cassegrain focus. Moreover, we have television viewing so that we're now sitting in a room away from the telescope, a lighted room. Observing in the prime focus, on the chair there, with the cover off because usually it was more pleasant to look out, if it was not too terribly cold, than to have the cover on all the time was really an experience.

You really have the inclination there, the temptation — and you do it too, in between moments that you have to guide — to just look around and stare at the sky. To perhaps think about things. Somehow, you're really close to the universe. Partly because you're so isolated from the ground there; in fact, only the great difficulty could you get out of that thing on your own and return to the ground, which is probably 30 feet below you. It's a little bit like space. One could image that space travel is like that, although we don't know unless we did it. But there is this sense of isolation and at the same time, of intimacy with the universe. It sounds trite, but it's an interesting experience — and I miss it now that I don't do it any more.

Of course, at that time, you didn't have image tubes, you didn't have SIT tubes, digital this and that, so everything took so much longer which contributed to the quiet and the atmosphere, as it were. These days [when an] observation is almost over you see all the numbers come out, or you have to look at screens to look at profiles or whatever.

Weart:

Now you almost get the results instantly.

Schmidt:

Right. It is now like photoelectric photometry used to be where you immediately have to check, you know, whether the Braun recorder gave a signal that seemed to be consistent, or didn't change too much, indicating there are [no] clouds.

Weart:

In those days, you might sit up there for three nights and not be sure whether you had the spectrum.

Schmidt:

That's what happened indeed. And it was a good spectrum, actually, but it was fairly scary. How I got the fortitude to do that on one of my very first runs is just amazing. Well, it was probably my second or third or fourth run or so, but —

Weart:

Did you have the time to think up there? You had to guide on a star. One reason I'm asking this is that I realized recently that I've been talking to a lot of people, and we both know what the 200-nice is like and so forth, but I really should ask you to put it down: when you guide, do you have to be watching the star all the time, for offset guiding?

Schmidt:

No. Typically when you're guiding, I would say that you look at the field, you correct the position of the telescope so the thing gets back where you want it, and I would often then not touch the button for a half or a whole minute. It's a little bit different if you do direct photography because any excursion of the star will lead at least to bright star images that have funny jets, of course. But in spectroscopy, where you check whether the star is still in the slit, the slightest excursion along the slit broadens the spectrum a bit which may not be so bad. And if it's perpendicular, you lose a little bit of light. But there is not the type of damage that you get in direct photography. The telescope actually tracks very well and so it's quite relaxed.

Weart:

You had quite a lot of time to think about — anything?

Schmidt:

Oh yes. And even while you guide, you do it automatically; you keep thinking, after a while.

Weart:

Was this winter observing?

Schmidt:

This long exposure was in August, so it was very pleasant.

Weart:

I see. Some people say things about winter observing as being rather different.

Schmidt:

Yes, it is.

Weart:

It gets quite vigorous?

Schmidt:

Yes. In a cage like that, on a good clear night — and of course, you know, the nights that you really observe are hopefully clear — things can cool off an awful lot. And finally, you'd be forced to close the tarp over you, and even then, you're shivering there. We had however Army Air Force flying suits from about 1943.

Weart:

Electrically heated.

Schmidt:

Yes, 24 volts. Oh, that's lovely, it's really great. We really needed that. If you're on the Newtonian platform doing photoelectric photometry, at least you rush back and forth, you stay in motion. But when you sit in the prime focus cage of the 200-inch, you hardly move around. You get very chilled.

Weart:

I suppose you can't move too much, or —

Schmidt:

No. You can sort of contrive to move, you know, just like this, [shifting in chair]/

Weart:

Your moving won't shake the telescope too much?

Schmidt:

No. It's remarkable that you can do quite a bit before the telescope starts to move, before you can see it on the star. You can, however, do it, just by shaking.

Weart:

But it's not easy.

Schmidt:

No.

Weart:

Ok, what do you say we have a break?

Schmidt:

Yes, why not? [Break for lunch at Athenaeum].

Weart:

Now, a lot of what's left is radio galaxies and quasars and so forth. But first, to finish up and make the transition, when you were doing this business on the rate of star formation, you were using the ultraviolet excess to get at the metal abundances.

Schmidt:

Yes.

Weart:

And you thanked Sargent for discussions on spectroscopic abundance determinations and so forth. I'm interested in your previous work, you hadn't done much spectroscopy. Did you know spectroscopy or were you sort of picking it up as you go along ? Because later on, you have to make a lot of spectroscopic type of arguments.

Schmidt:

I guess I thanked Sargent because he was a post doctoral fellow here on Jesse [Greenstein]'s abundance project, and I was discussing with him the relationship between the Delta 'U-B) — the ultraviolet excess — and the abundance. As they had been determined in general for stars, from Coude work. And a major point of interest was the following: The critical Coude people thought that they could get abundances with an accuracy of about a factor of two. Now, a factor of two in abundance corresponds to a Delta (UB) of .06. Could you believe anything like a difference in Delta (UB) of .02, which would correspond not to a factor of 2, but say a factor of 1.2 or 1.3 or so [in abundance]? Why could an integral method, that you do in three minutes perhaps, do better than a detailed spectroscopic study on a high dispersion spectrogram that takes a good man two months? So it was those questions that I discussed with Sargent. It was not my entry into spectroscopy really, but rather trying to understand the significance and the accuracy of abundance determinations based on high dispersion Coude spectra and Delta (UB)'s. That relationship.

Weart:

What was your entry into spectroscopy ? Had this just been in your tool kit all along, so to speak?

Schmidt:

No. I am, although it may sound rather strange, not basically a spectroscopist. In that case I was interested because it so happened in the star formation effect that chemical evolution is an interesting thing, and we need something to look at, and those are the stars and their abundances and the Delta (UB). So I only discussed this spectral evidence with Sargent because he was around, he's critical and knowledgeable. I was not, and even now perhaps, I am not a real spectroscopist, I would say.

Weart:

Did you find you had to do a lot of this sort of thing when you got into spectra of distant objects? You had to go and catch up on how these things work ?

Schmidt:

Yes. Right.

Weart:

I see. How did you get into this program? This is now shortly after you arrived here permanently.

Schmidt:

I arrived in October, '59. In June '60 Minkowski retired. He had been taking spectra of radio galaxies, but only a relatively few, mostly nearby systems like Fornax and 3C 66 — and Cygnus A, of course, very important — and then only one distant one, but that of course was a record that was not to be broken for a long time, 3C 295. But there remained much to be done. He had worked with Tom Matthews, who was a radio astronomer here in the group at that time.

Matthews supplied the identifications from the position work that was done at Owens Valley, with the twin interferometer, the accurate positions. Tom gave the identifications with galaxies; Minkowski would take the spectra and get the distances from the red shift. And when Rudolph [Minkowski] was about to retire, it was clear that this work was far from finished; much more was needed. So I sort of stepped in, and essentially took over that kind of task - as a service essentially to radio astronomy, you know. The most important thing was that one got distances, and therefore luminosities and diameters, of these radio sources, these twin lobed radio sources. There were only relatively few known at that time when I took over, perhaps ten or twenty, and there were many more to be done.

Weart:

What did you see as the aim of the work ?

Schmidt:

The aim of the work was indeed, as I said, to get luminosities and sizes, and about the same time, in '60, but perhaps a little later, came the problem of the total energy of radio galaxies, because when you look at a synchrotron mechanism and come up with a minimum energy, à la Burbidge 's model in which magnetic field energies are balanced in such a way that total energy is least, you get for these very large radio sources extraordinarily large energies, like 1062 or so ergs, which is equivalent to 108 solar [per year]; and therefore you know, at nuclear efficiencies, it's almost the total energy you can expect from thermal burning in a whole galaxy. Admittedly, that did not come up immediately. I think that was not the big problem yet in '60. But that gradually grew throughout the next two years, I think, into rather a major problem.

Weart:

Did you see your work as having anything to do with that ?

Schmidt:

No, not in the beginning. Just to help out in getting red shifts, distances, sizes, and luminosities of these radio galaxies, because they obviously were very interesting, we thought. Although I said that when I came here, it was clear that my choice had been optical astronomy, that has never really perhaps been really executed. I think my interest in radio astronomy remains strong. For that reason, I thought it was an ideal way to do optical astronomy, about something that's of great interest to radio astronomy.

Weart:

Did you get into this mainly through conversations with Matthews, or with other people also?

Schmidt:

I think it was mostly Tom Matthews. And with Minkowski's impending retirement, it seemed just like the right program to take over. So I did it. Tom and I worked together for a number of years, him supplying the identifications, and I getting the red shifts .

Weart:

OK, you were saying that you did discuss these things with Matthews, also with others? Was there any formal structure? Was there a users' group for Owens Valley, any way that the optical astronomers regularly interacted ?

Schmidt:

Not at that time, I think. At that time, there were relatively few visitors to Owens Valley. The twin interferometer yielded these radio positions, which were so necessary. Tom Matthews and Moffett, who was probably a post doctoral fellow of some kind and then, what 's his name it was the 'triple-M' paper, Matthews, Moffett and —Malby. They came out with these results, with the double radio sources and the galaxies in between. I think much of Owens Valley's time at that time was occupied with that particular type of work.

Weart:

How was it formally organized? You never used Owens Valley yourself?

Schmidt:

No, I didn't. No. So I think it was mostly the decision of Bolton and Stanley, how to assign the time.

Weart:

I did you have any input into this ?

Schmidt:

No.

Weart:

I see. So it was really something that just was there, and feeding information to you.

Schmidt:

That's right, and at a rate that was such that there was no need to get involved. They fed things that were so interesting that kept me busy for quite a while. I know that Tom was interested — since somehow everybody is always interested in larger red shift — Tom soon did get interested in following up particularly on sources that were small. The smallest angular diameters in radio, in the hope of getting to things that were more distant .

Weart:

With some sort of generalized cosmological aims?

Schmidt:

: At that time, it already became clear that radio galaxies had luminosities optically just like the brightest cluster galaxies. And since the brightest cluster galaxies for a long time reached out, as you know, to 20 percent red shift with radio galaxies 'since they had emission lines) it was possible which to reach out farther. As of course exemplified by 3C 295, which had 46 percent red shift. So, I think there was also the feeling that you might supply sources for the cosmological determination that way .

Weart:

There was some hope of getting qo?

Schmidt:

Yes I think that time that was already — Sandage was already — I think I'm not placing it too clearly in history.

Weart:

No, that 's about right — that he had seen it as the eventual product of his work.

Schmidt:

That's right. There is this article of Sandage's, what you can do with the 200 inch in this kind of field, in which he had these diverging Hubble diagrams for different qo, cases. And I must admit that I'm not actually sure - it may have been written in '61.

Weart:

You don't have to pin it down exactly here. So this may have seen by yourself as one reason for finding spectra of these galaxies.

Schmidt:

Yes.

Weart:

After all you're given a position, you have to take quite a lot of 200 inch time to —

Schmidt:

— oh yes, right. In fact, I remember that one of the few instances where different people in the observatory got together, this must have been in January 1960, when it was clear that Minkowski would stop the work next June, there was even a small group that came together, consisting of Bowen, and Bolton and Matthews, and probably Guido Munch, perhaps Alan Sandage and myself, how that should be continued. Now, I seem to remember at that time, we decided that each of the four optical astronomers present would take a quarter of the works. But that never happened, and they all and they all went on with their programs. I hardly had a program yet. But still it was of some concern, of the optical plus radio astronomers, how that would be continued.

Weart:

I see. Very interesting.

Schmidt:

One of the rare instance where I 've seen, in this place any general planning .

Weart:

And in fact, it did not happen. But perhaps it wasn't necessary, because you —

Schmidt:

No, then, as soon of course as I took it over, it solved the problem that existed. It was not necessarily a privilege to have it, but rather, how could you make sure that the program kept going?

Weart:

Was that the reasons in fact that you did do it, because you saw this demand for it ?

Schmidt:

Yes . I did . Yes .

Weart:

I see, very interesting .

Schmidt:

But also probably because I did not have a program, except this helium abundance business , that was a really clear candidate for —

Weart:

For your time .

Schmidt:

For my time. I was still rather open minded.

Weart:

You had a certain amount of [telescope] time that you would have .

Schmidt:

Yes, right.

Weart:

I see. In general, though nobody had suggested to people how they should spend their time?

Schmidt:

Oh yes, of course, privately. But usually not that you sit together with a group as a whole, and that the group finally says, 'well, why don't you do that, and take one third of that, and do that?' That's not the way it happens here.

Weart:

It's more that somebody will take you aside and say, 'Why don't you look at such and such?'

Schmidt:

We all try to influence each other, to some degree. I tell Marshall Cohen all the time, that with the VLB [Very Long Baseline interferometer] they shouldn't always concentrate on these few famous sources, but should do a survey of very bright radio sources, and see what's in them. In other words, I try to push on somebody once in a while .

Weart:

Well, again, it's your Kapteyn school  that you should get a systematic sample.

Schmidt:

Sort of. That's right. And of course, that interest of Tom in small radio sources - and how did he know they were small radio sources? I think there was Jodrell Bank work going on at the time; they probably already had their interferometer going, although a small baseline. Some sources were only a few seconds of arc across, perhaps less than a second of arc.

Weart:

Yes and you could tell from scintillations also, which ones were small —

Schmidt:

yes, scintillations were already in vogue, and indeed, they helped too. Anyhow, we knew more or less about the smaller radio sources. So, I remember a number of sources that Tom in fact gave me as part of this attempt to go after small radio sources. And I remember that 3C 254 and 3C 273 were among those. In hindsight, it is somewhat funny. By the way, I'm not placing these two at this moment relative to 3C 48, which I'll touch upon in a moment. But those two, which eventually turned put to be quasars, one with a red shift of .8 and the other one 273, with .16 each of them suffered one lobe shift, which was a plague in radio astronomy at that time, because, you know -

Weart:

I see, you had the wrong location for them.

Schmidt:

In each case, we had a galaxy for the darned thing.

Weart:

Oh, there was a galaxy at the wrong place?

Schmidt:

Right. And in each case I got a spectrum, and in each case it was left with a question mark, because most radio galaxies have some kind of emission line.

Weart:

Right, and these looked like ordinary galaxies?

Schmidt:

Right. So both of them were left up in the air, as it were. Now, I cannot place those two exactly relative to December or October '60, when 3C 48 was found. But it ties in and we'll talk about it. It is a tie-in of radio galaxies to Tom's interest in small sources, and that immediately led to what were to be the quasars.

Weart:

Were you hoping to get very large red shifts also?

Schmidt:

Yes. I did some of my thinking, as I remember, in the darkroom while developing, the four or five minutes that you have nothing to do and you stare. And I remember thinking once that I would be happy to reach a red shift of two-thirds in my lifetime. That seemed like the ultimate aim.

Weart:

That seems very ambitious for that period. This was bef ore 3C 48 .

Schmidt:

Yes. But then one hoped for a long development and a long lifetime, so twothirds seemed to me what I hoped for.

Weart:

I see. So then, 3C 48.

Schmidt:

Right. And 3C 48 strangely enough, went entirely by me. That sounds strange. I had nothing to do with 3C 48, was not particularly well informed about it, never took part in any discussions about it, and was to quite a degree, I think, blissfully unaware of it even, while it happened. Which sounds very ironic or strange at the moment. So I cannot give you a firsthand report of it, because there is none; I was out of it. There must be other sources for this of course, but I think that the first spectra of the star that Tom Matthews identified with 3C 48 were taken by Sandage, I think around October '60. Of course, one can look it up. Anyhow, the five of them, Bolton, Matthews, Sandage, Munch and Greenstein, came with a late paper in the December '60 AAS meeting, at which they announced that they had this stellar object, variable, and a strange spectrum, and blue .

Weart:

You knew that this was happening, it just didn't make any particular impact on you?

Schmidt:

Nothing, I probably knew about it, but I was happily going on with my radio galaxies, and I was not involved for some reason .

Weart:

Is this possibly because it was seen as simply being a star within a galaxy?

Schmidt:

Possibly. I don't know. I have no idea how the others got so readily involved while I'd not.

Weart:

Because in this book by Edge and Mulkay about radio astronomy, they say that radio astronomers took it very much in stride: They always had thought there should be radio stars around somewhere.

Schmidt:

Yes, that's true. I think the radio astronomers indeed were very inclined to call them immediately 'radio stars.' Yes.

Weart:

Yes, they did, that's exactly what they called them. I see. So even when in 1962 Matthews and Sandage announced two more 'stars', again you don't particularly recall this as having had an impact?

Schmidt:

Oh yes. You see, I was involved in every one after that. Every single one, I was involved with. The only persons involved in the subsequent ones for quite a while were Tom Matthews and myself. It was very strange.

Weart:

Matthews and Sandage did announce two radio stars, not radio galaxies but radio stars .

Schmidt:

When?

Weart:

In '62. I don't have the exact 

Schmidt:

 I don't think that's right.

Weart:

Oh, perhaps I have it wrong.

Schmidt:

I think if you find in subsequent work that this is correct, I'd like you to come and check back with me because it doesn't fit with the history I'm going to tell you in a few moments.

Weart:

Let me look something up, just a second. [Short pause]. OK, what I have here is from the Mt. WilsonPalomar Observatory's annual report of 196162; 'Extending the work reported last year Matthew and Sandage identified two additional radio stars, similar to 3C 48, 3C 196 and 3C 286.'

Schmidt:

Well, it is possible that Sandage was involved in that. I wasn't sure of that at all. If Sandage was involved in that, it must have been such that Tom Matthews, of course, made the radio identification, and Alan [Sandage] may have done photometry on this.

Weart:

It's photometry, that's right . It was not a spectrum, it was photometry .

Schmidt:

Yes. Because I got involved in the spectra of all the subsequent ones. And that was probably indeed, first, 3C 196 and 286, then subsequently; 3C 147, that's four, and then 273, which was fifth. Now, for 196 and 286 I took spectra. And 196 never yielded any lines. It did show some emission lines, which of course had been there) but I was rather conservative. Quite a few years later Roger Lynds finally solved the case with excellent spectra, so it is a quasar indeed. But these are very indistinct. The red shift is, I don't know .8 or something. For 3C 286, I saw immediately on the spectra one line at 5130 Angstroms. I couldn't identify it, and I published a note. I don't think there were letters at that time . A letter or a note, whatever the ASTROPHYSICAL JOURNAL had, in I think August, 1962, about this thing. It's only this long. It says, there's the one line. It says that I don 't understand what it is, and it's not shown by this object, that object, that object, or by 3C 48, which otherwise might be similar .

Weart:

So this is a new line .

Schmidt:

Yes. A new type of object; new line, I don't understand what it is . I think it is the first publication in the literature about quasar, that one. It s pre-3C 273 discovery. It complains about my inability to understand what the line was. That case was resolved a number of years later, when a second line was found near 3520. When I looked at the spectra, a few months ago, I did see that line at 3520 on the spectrum.

Weart:

You mean, on your original spectrum?

Schmidt:

On my original spectra the line is visible. But of course, the signal to noise ratio of all these lines in quasars usually is fairly poor. It would have been very interesting if I had seen that line at that time, what I would have done with it. Because the red shift for this thing is .85, and that one line was CIII 1909, and the other line was Mg II 2798. I think I couldn't have handled that case at that time .

Weart:

No. It's unlikely that you would imagine an object that had those two lines in it .

Schmidt:

Right. Anyhow, there was the one line. Then there was 3C 147. There was a lot of activity therefore, because I was just talking about August '62, and in December '62 there was a conference about radio astronomy at the Goddard Space Institute, in New York, Riverside Drive or whatever. It's also a church, I believe, at the same time. It's Robert Jastrow's Space Institute for Space Studies. There was a conference there. And I remember that I gave a speech about 3C 147, in which I thought I saw four lines in the red, and I thought that two of them 'thank heavens I never published this stuff ) were perhaps variable. I thought I saw a certain symmetry about the particular helium lines, and I sort of fantasized a little bit about a possible expanding helium shell. That was number four, 3C 147. Now, of course, I wasn't the only one who was perhaps on the wrong path for a little while. Then, a week later, I think it was, I had an observing run at Palomar at which I observed 3C 273. It had, as you know, been observed in occulation by Hazard in Australia, who had sent the on to Tom Matthews. I'm still unclear in my mind, who actually made the identification with the star. I'm almost sure that Cyril Hazard did it himself .

Weart:

From the [Palomer] Sky Survey?

Schmidt:

Yes, right.

Weart:

By the way, did Mackey and Shimmins also have an occulation?

Schmidt:

Yes, it was a joint paper by them.

Weart:

Oh, I see, it was the three of them.

Schmidt:

Shimmins is a technical man, and Mackey of course was more of an astronomer, and Hazard was the leader of that team. There were a number of occulations that happened in August, I believe. So, it was a star with a jet, and when Tom and I looked at this thing, since it was a double radio source, with one source on the jet and one on the star, Tom and I certainly suspected the jet, which looked strange, of being it.

Weart:

Rather than the star?

Schmidt:

Yes. I think both Tom and I probably thought that the star was just accidental. In other words, that it was [a field star] —

Weart:

I see. And this jet was, something extremely distant.

Schmidt:

Right. But aware as I was, when I went up to Palomar December '62, that the jet or nebula or whatever you call it was exceedingly faint, I first took a spectrum of the star, which was 12th or 13th magnitude . And the first spectrum was totally overexposed. You see, I was used to 18th magnitude galaxies, and a 12.8 magnitude star was difficult to evaluate. We didn't quite know the magnitude. But in the heavily over-exposed spectrum, I saw two lines, one way in the ultraviolet, at about 3200, and then one perhaps 5600, where the spectrum again got less overexposed. The next night, or two nights later, I got better spectra, which showed a number of lines, five lines in total, I believe.

Weart:

On that 12th magnitude, you took the whole night to take the one spectrum?

Schmidt:

Heavens, no .

Weart:

Oh, you shot this, then you went on and spent some time on the jet, something like that ?

Schmidt:

No. Mind you, these were photographic observations; you don't know what you get. And I wasn't sufficiently excited about the thing to interrupt the night to go and develop, while the night is dark. You do that at the end of the night.

Weart:

I understand. What else were you doing that night? I'm just curious .

Schmidt:

Oh, lots of radio galaxies .

Weart:

I see, just more radio galaxies .

Schmidt:

Yes, right.

Weart:

Was this one more amongst the radio galaxies?

Schmidt:

Oh yes. And the observation of the star was just taken sort of in half an hour's time, quickly, — too long, it turned out to be — just to get rid of it. So one knew that it was the nebula [that was the radio source] and then could eventually work on that. But it would obviously be, you know, a nightlong exposure or so; it was exceedingly faint. Just to rule out the star. But even this overexposure seemed to show some lines. So the next night, I got some better exposures. I went back to the valley here. And then there was a funny thing that happened, that was only funny in hindsight, because Jesse [Greenstein] had been working hard on 3C 48 in the meantime. Took spectra of it. Measured all the lines, did a good job at line measurements. Culled out lines that existed and those that were not reliable, and came up with a reliable good line list, with wavelength and line strength. And since the thing looked very strange, he had been discussing that spectrum and had come up with funny element combinations. He had intended the R process. He had written a thick paper about it. [Indicates thickness with thumb and forefinger].

Weart:

How many pages?

Schmidt:

Well, you know, perhaps 60-80 or so. I still remember — it must have been about a week or two before the red shift of C3 273 was found — that he came to my office one day, threw the thing on my desk it was probably a few days before C3 273. He was frustrated. He was done with it. He threw it on my desk and said, 'Ah well, this is it, Maarten. This is the best I can make of 3C 48. If you have any remarks, he said, "let me know within a week, and then I'll send it off. Even more ironical, in that very manuscript, a red shift was mentioned as a possibility for 3C 48 of 36 percent.

Weart:

In that manuscript?

Schmidt:

In that very manuscript.

Weart:

Which he hasn't saved.

Schmidt:

I have it.

Weart:

Oh, you do? I see.

Schmidt:

He took the lines that he had, emission lines, in that manuscript, and investigated all possibilities, even sizeable red shifts. And one that was mentioned was 36 percent. Now he did something very unfortunate; as a spectroscopist it must really have bothered him, that he did this. In getting 36 percent, he found that he needed to interpret two of the lines as Neon V, forbidden and they are Neon V you know and one line as oxygen. He found that necessary. He rejected it on that basis.

Weart:

Is it Oxygen-I? No, it's not.

Schmidt:

No. He rejected it on that basis, because he said, it's inconceivable that something can have Neon V, with the ionization potential of 94 volts, and neutral oxygen, Oxygen I. Now, there are two reasons why that was an unfortunate thing to conclude. One, we already knew that Cygnus A shows Oxygen I and Neon V. But much worse, two angstroms from the line that he identified as Oxygen I, in other words, at the same place, there is a Neon V line .

Weart:

Another Neon V line ?

Schmidt:

Yes, that he overlooked. What he would have done, in case that these were three Neon V lines I cannot predict. But in hindsight I think Jesse, months before 273, was as close to the red shift of 3C 48 as he could possibly have been. And he dumped the thing on my desk. I hardly looked at it; I was very busy, and I said, 'Yes, if I see anything funny I'll let you know within a week.'

Weart:

But ln fact, it didn't make any striking impression on you at that time? It was only after reading it later?

Schmidt:

Of course. Yes.

Weart:

So maybe you had gone through it quickly, and

Schmidt:

Oh yes. I don't know if I even saw it at that time. The R' process was sort of prime. Well, I had these emission lines. And in his next run, which must have been late December or early January 1963, Bev Oke used a multi-channel spectro-photometer on the thing, and found a line at 7600 in addition to the ones I already had. So that gave, I think, a total of six lines the one at 3200, the one way out in the infra-red at 7600, and then the four between, oh, 4100 and 5600 or 6000 or so.

Weart:

So Bev knew that you had the spectra, so he came to you with this line ?

Schmidt:

Yes. And I showed him all the wavelengths, and he added his own to it. I showed the wavelengths of the lines, with rough indications of strength, to Bodo Baschek, who was a research fellow here. 'He's a student of Kiel, a spectroscopist .) I showed all the wavelengths to Dr. Bowen. And both Dr. Bowen and Bodo Baschek came up with slightly different interpretations that involved a very small red shift: identification with helium II lines. And an important line was missing. So it seemed unreasonable and unlikely. Nevertheless, one wasn't sure. Well, I think that's where we were on February 5, 1963, which if I'm right was a Tuesday, when I was responding to a request by letter from either John Bolton, who wasn't at CalTech anymore 'I think he was then in Australia) or from Cyril Hazard himself, that I write a letter because they knew that I had the spectrum. W'd written back and said, 'We've taken the spectrum; it looks odd, some emission lines, can't understand it.' So they suggested from there that since they were going to write this thing up for NATURE, would I write a letter that could be published following theirs, a note to NATURE about the spectrum. And it was a fact that I found the red shift while I was writing this article which is sort of the unusual way around.

Weart:

Actually, not. A number of people have discovered things, while they were carrying on a lecture for a colloquium, rather than actually writing a paper.

Schmidt:

Yes, when you have to sit down and do things systematically and that's sort of what happened . What happened was the following. It was in the early afternoon, and I don't know, for some reason I pulled out the spectra again, and I was looking at them. And then it struck me that among the visible lines on that spectrum, of which there were five, if I arbitrarily left out the one that was way in the ultra-violet 'it seemed kind of special anyhow, way in the ultraviolet and very strong), and if I left out one more line, namely the one at 5600 or 5800, that was kind of weak -

Weart:

which was the weakest of the lines, yes —

Schmidt:

The three remaining lines seemed to be going from strong to weak, and with decreasing separations. Strong, weaker, weakest. And I also realized that Bev Oke's line at 7600 seemed to be sort of fitting in that scheme, in that it apparently was quite strong although it was difficult to compare it, because you couldn't see it - but it had the largest separation again . So it looked as if I had a series. But I wasn't thinking of the Balmer series at that moment. Well, just sitting there, for some strange reason, I felt I should make an energy level diagram, which in hindsight is senseless; doesn't matter. I'm just telling you what happened, not what is reasonable.

Weart:

I'm not sure that it's senseless . You were going back to the beginning .

Schmidt:

I was going back to the beginning, indeed. So I decided to make an energy level diagram.

Weart:

So you made a diagram. You drew a diagram?

Schmidt:

I probably drew a diagram. But I was going to get these terms you know, to get some formula that would do it . Which basically may not have been a bad idea, but I wasn't used to this kind of stuff. But I went at it. And it only took a few minutes when I must have made a computing error or so because while I thought I would now get a consistent something; [for the third time] I got something that was way off. I don't quite remember what it was, but that's what happened .

Weart:

Obviously off .

Schmidt:

Yes. So I was a little irritated, and I said: 'Now look here, that seems to indicate that it is not a regular spacing. But I see it's a regular spacing.' I thought, OK, I'll check whether it's a regular spacing. And that was it. I decided to take the ratio of the line at 5600Å to the nearest Balmer line still not thinking of the red shift.

Weart:

Just because the Balmer series ss a regular series.

Schmidt:

Right. So I took the ratio to 4861, and I found a ratio of 1.158. I took the next line, which was at 5035, divided by 4330, and I found 1.160 or so. Then I took the next one. That was 1.158 again. And suddenly it dawned upon me, you know — that third one certainly, perhaps the second but the third one certainly. Then I took the 7600 line and divided by 6563Å, and multiplied by H-alpha; and it was 1.160 or close enough. And the re it was . Suddenly, there was the full realization that it had to be a red shift that it was the Balmer spectrum, shifted.

Weart:

It didn't occur to you that it might be some Balmer-like spectrum highly ionized something or other?

Schmidt:

No. You may have read that somewhere. In fact we spent a lot of time trying to prove or disprove that. Indeed, what happened was that while it was immediately clear that it could be the red-shifted Balmer spectrum, nonetheless — Let me take one step back. When I got that 1.158 as the best ratio, I applied that ratio in the inverse also to that weak line that I had rejected and the very strong ultraviolet line. The weak line gave something like 5007, which was reasonably forbidden 0 III line. 'Which finally turns out to be practically wrong; it's some iron line). And the ultraviolet line landed at 2798 or 2800, and I happened to know that magnesium II was to be expected there; it was also in the sun and so on. The magnesium II seemed very interesting. It was about 2:30 or 3:00 in the afternoon. I walked out in the hallway. I saw Jesse. I said, 'Jesse, come in. I have to tell you something. You won't believe it.' So I told him the story, and he was absolutely aghast. He said, 'We ought to look at 3C 48.' So we finally pulled out the 3C 48 paper which I really looked finally at with real interest, you know, this line list and so on. Then he stood at the blackboard and read me wavelengths, and I would divide them by what seemed I would divide them by what seemed the wavelength of a reasonable identification with a little slide rule. It didn't take long. You know, it took minutes for us, about five to ten minutes after we started with 3C 48, to find a red shift of .358.

Weart:

He didn't think immediately of this 36 percent that he'd had in his paper?

Schmidt:

I think fairly soon, yes. Fairly soon. Because he knew his paper, of course. Two neon V lines were there and they're common in planetary and nebula H II regions. But when, in taking the next farther ultraviolet line, we divided it out, we found 2800 again — here it was the second time the magnesium II line was found in an afternoon — we felt that his had to be it. This was it. So at that moment, when 3C 48 yielded within ten minutes, we both were thoroughly convinced that that was it. We then did the two things. We called Bev Oke in very soon and discussed the whole thing with him, to have somebody to talk to. And, in fact, later, before dinner time, we returned to Jesse's house and sat around and drank. And Naomi [Greenstein] said, 'What's happening?' Because we all came in their house over there, we were almost speechless. We were either yelling or speechless. We sat drinking a drink and Naomi found it hard to understand what was happening. I'm sure we were like a bunch of nuts.

Weart:

When did you tell your wife?

Schmidt:

That same night when I came home, of course. I was late of course.

Weart:

What did you say? 'I've discovered something'?

Schmidt:

Yes. I said, 'Something terrible happened at the office today.' That's the way I expressed it, according to my recollection, that was refreshed a year later. I'm not sure. That's what I am supposed to have said. 'Something terrible happened at the office tonight.' That was brought out by the BBC a year later; I think it was the right recollection. I certainly couldn't remember that for 14 years. The thing that we engaged in most of the rest of the afternoon in the office, before we retired to Jesse's house, and that I spent the evening at home in doing, was to prove that it could not be a heavy nucleus with only one electron somehow. I'm not sure it still made all that much sense to try to disprove that, after 3C 48 came along, in which the neon-V lines, for instance were present. But with the Balmer-type spectrum, there was this fear initially that perhaps if you take a lithium or whatever nucleus and you ionize it — you know, it's ridiculous of course, but we wanted to be absolutely sure. No funny stuff. I in fact managed — although we never published it later — that night to finish the proof that the 3C 273 spectrum could not be something heavier. Somehow things didn't fit. Anyhow, the next day we were all sufficiently sure of the fact that we had a red shift. I paced around the house that night, just think of the consequences of it all. Because it didn't take us long to realize what you could do with this — namely, that if a 13th magnitude object had a 16 percent red shift, what does an 18th or 20th magnitude object have? We already saw essentially the very big red shifts looming, as it were.

Weart:

Were you also struck immediately by the energy problem?

Schmidt:

Yes and no. The energy problem did not exist for these objects because they were rather small, the way it does for radio galaxies. Namely that the stored energy content is so extraordinarily large. Rather, in quasars, what might be called the energy problem is the rate of output of energy per second, which is very large of course.

Weart:

I see, so it didn't fit in with your previous thinking about energy problems.

Schmidt:

No.

Weart:

Because previously it had all been in terms of Burbidge's idea of stored energy.

Schmidt:

I might at this moment interject something else. Fowler and Hoyle, who had been very much aware of and worried about this energy problem for the radio galaxies, had just by this time that I discovered the red shift of 3C 273 finished a manuscript, or almost published perhaps a paper, in which they took a massive object. It was the one where they used a star of 108 solar masses and said they turned a blind eye, a cold shoulder and something else to all the difficulties that might exist there —

Weart:

It was about that time anyway.

Schmidt:

But anyhow, in order to face this problem, to make some contribution to this particular problem of radio galaxies, they considered a massive star, etc., and found an output of energy for the thing of 1046 ergs per second. And the funning thing was that when I first told Willy Fowler, who is very alert and very perceptive about 3C 273, and said it had 1046 ergs per second, he said, 'Yes. Sure.' It was very funny. Other people were astounded, you know, the astronomers. And I told Willy and he said, 'Yes. Sure.' Willy is not normally like that.

Weart:

Tell me, did you immediately go around the next day and so on and tell other people about it?

Schmidt:

Oh yes. We talked freely about it, yes.

Weart:

At what point did you inform people outside Pasadena?

Schmidt:

Geoff Burbidge head about it exceedingly soon. He was in LaJolla. And since Geoff had also sent me, one or two weeks before the discovery, a paper which still appeared, I think in NATURE, explaining the darned thing perhaps C3 48, as some kind of funny star, Geoff's first reaction — historically it's kind of interesting, because it was to become rather a controversy — was rather sour. I still have the letter somewhere, of course. It was written three days after I discovered it, I believe. He said, 'Dear Maarten: Willy told me about your discovery of the red shift of 3C 273 and the bigger red shift in 3C 48. What happened to the variability of 3C 48? Did it go away? Yours, Geoff.'

Weart:

Had that problem occurred to you?

Schmidt:

Oh yes, that problem occurred to us within a day or so. This was interesting because it was the first time, I think, in astronomy that size determinations based on variability played any role. And it was a realization we came to, as soon as we started thinking of all the consequences, you know — big red shifts now — and the thing is variable. My God, we said, it's variable! It must be smaller than a light year. Now, that was not a kind of consideration that had come up in astronomy or that was taught in classes or so. We thought it up on the spur of the moment. And although, of course, it looks entirely obvious, I don't think we were used to arguments where you said, 'It's variable, therefore, it's less than so and so large.' Wow, that's quite a combination.

Weart:

I must say that was the first time I ever heard that argument. After all, what object would on make that argument about?

Schmidt:

That's right. It suddenly became an argument. It's been made several times since, not only —

Weart:

— and it's still there.

Schmidt:

Yes. So that argument suddenly dominated the discussion almost. 'My God, that thing has to be a light year, perhaps even light month, and it throws out 1046 ergs per second!' That was, of course, what had made and kept quasars to interesting, in terms of observable. Not now the interpretation, but purely the observable: the combination of a large red shift with rapid variability. And you can interpret it whichever way you want, but that combination is unbeatable, almost, in terms of basic excitement, the newness of it, I think.

Weart:

Even now.

Schmidt:

Yes.

Weart:

So you sent this paper off to NATURE right away?

Schmidt:

Right. But we also had to first make up our minds what we thought of things.

Weart:

Who do you mean 'we'?

Schmidt:

Jesse and I. Because Jesse and Tom Matthews soon published about 3C 48 and I published everything as a sequel to the letter of Hazard et. al.

Weart:

You mentioned all these people you talked to, Bev Oke, Willy Fowler and so on, but it rapidly became you and Jesse that were sitting and talking about it?

Schmidt:

Yes. The thing was that as soon, in the next few days, as our physicists here at CalTech heard about it, they urged that we look more carefully at the gravitational red shift. Which of course in a sense was correct, because if something is so small that it can even be seen to vary, you might have a sizeable gravitational red shift. And that was one of the first things Jesse and I discussed.

Weart:

Even before that, in your NATURE paper, you mentioned the possibility of a gravitational red shift, only to doubt that was the case.

Schmidt:

Right. So Jesse and I had already essentially investigated this, perhaps not as e exhaustively as we were eventually to do it, but we already had given it quite a thorough first going over.

Weart:

In this first paper, you also mentioned the jet. You don't say so directly, but did you see it as possible that there was some catastrophe going on in this? You were inclined to see this as a distant galaxy, is that correct?

Schmidt:

No. I think that in case the bright star had been a normal galactic star — I think in that case, I would have thought that the jet was a very strange type of galaxy. But once we knew the real center of attention was this very bright object with a big red shift, I guess we didn't think of galaxies any more. We just considered the jet as a jet, like in M-87, which of course has a well-known jet. Which doesn't mean that we understood it, nor that we gave it much attention. The jet has been rather under-discussed, I think, in astronomy.

Weart:

Still in your first reports, you talked of it as it were in a galactic nucleus.

Schmidt:

No, I don't think so. Because there was no good reason. I've tended later to speculate that quasars are a galactic nucleus in formation, or so.

Weart:

Right, but I'm thinking of, originally?

Schmidt:

I don't think I started out that way.

Weart:

So it was almost as if it were a thing unto itself, not connected with galaxies.

Schmidt:

Yes.

Weart:

I see. In one of the [Mount Wilson and Palomar Observatory Annual] Reports it was mentioned as being a galactic nucleus. But that wasn't necessarily your writing, that might be somebody else's?

Schmidt:

I can't remember that. I'd have to see it. It was not our prevalent thinking and has remained speculative.

Weart:

At that time, where did you think the energy came from? In your paper with Greenstein —

Schmidt:

Well, we called it Object X which means that we kept a respectful distance, really.

Weart:

And this was the way you actually thought about it. Something in there.

Schmidt:

Yes. By the way, within a year, there was a sufficient number of people who filled NATURE and other magazines with speculations, of course, about what's actually happening there. Coalescing star clusters, a bit stellar-type body, later as a collection of pulsars, a giant pulsar, matter-anti-matter. I mean, there was no lack of imaginative theorists giving it their attention. So, I did not have strong — I had no idea what it was really. 'Following section closed.)

Weart:

Let's go on — after the collaboration with Jesse, the next year apparently you went back and thought it over again, the problem of the quasar red shifts, whether they could possibly be local. By this time, there is this idea that, who was it?

Schmidt:

At Los Alamos, Terrell.

Weart:

Yes, Terrell.

Schmidt:

Explosion from the galaxy.

Weart:

Things like that. So you went back to square one to think it over again, is that right?

Schmidt:

Oh, I did that continually. I was called upon rather often around that time to speak at conferences. I spoke several times at APS [American Physical Society] meetings. I don't know, 1965, I gave the Warner Lecture for the AAS in Montreal. I spoke at several Texas conferences, that were not all held in Texas, sometimes elsewhere, you know. And every time, since it was usually a review type lecture, I tried to argue completely again why we thought the red shift was cosmological. And in a sense, usually the discussion, especially after the local hypothesis was created, was fairly defensive. In the sense that one could never come up with direct arguments why it had to be cosmological, but rather, why the other things were not so good either.

Weart:

Did you ever have doubts? Was this rethinking mainly to answer others, or did you doubt yourself sometimes that it was cosmological?

Schmidt:

No, I had continually certain doubts — doubts, by the way, that not always came through, for instance, to our own students, equally clearly. I remember, about three or four years ago, a standard sort of Friday lunch at which some students were sitting fairly close to Jesse and me. And for some reason we talked a little bit of history 'this was about five years ago, I think) — I said, 'Jesse, how sure are you of quasar red shifts being cosmological?' Now I shouldn't speak for him, of course, but I think he probably said something like, 'Oh, 90 percent.' I said, 'Wow! For me, it's only 80 percent.' Several graduate students who were sitting around us were stupefied and stunned, could hardly speak.

Weart:

I see, thought it had to be 100 percent?

Schmidt:

Oh, they thought it was 99.999. It was very interesting I think.

Weart:

I see. Did you ever give any credence to ideas like Arp's?

Schmidt:

At times. There were certain phenomena that he showed, that we thought were very disturbing. That is, disturbing for our point of view about the cosmological red shift. However, it was on a statistical basis that we continue to feel that his arguments are weak. Also, very varied: they cannot all be true at the same time. It as it were a shotgun approach, where one is shooting fairly hard, but not all of that can be true at the same time. But once when Arp had this beautiful photograph that showed this connection between NGC 4319, a galaxy, and Markarian or so 2 something, that was a quasar, it looked really remarkably convincing. Of course, in subsequent photographs others, and I think Arp himself, too although he doesn't quite agree, have not really been able to show that that bridge is really there . It's not so convincing. So you have to watch it.

Weart:

Do you feel that Arp's position, not his scientific position but the way people regard his work, has changed with time? Here in Pasadena?

Schmidt:

Not terribly much. I think all of us have become a little more mellow. I think that in the beginning, some of us felt that his methods were unscientific, and that is not something that is very nice or agreeable or polite to say to a colleague, or to imply it to a colleague, even. It was in reality, of course, and difference of emphasis. Many of us felt that if you have two objects that stand close to each other in the sky, and if they have different red shifts, that the red shift is such an important clue to where it is in the universe that you just say, 'Well, it's accidental,' The other person then says, 'No, it's not accidental, and the red shift has a different interpretation'. That, without further solid supporting evidence, seems naive. But I think these days we talk about these things in a much more relaxed fashion.

Weart:

So you may agree with him less but you also disagree with him less?

Schmidt:

Sort of in a sense, I think.

Weart:

Well, your next thing then was going out and identifying the red shifts of more QSS's, 'quasistellar sources' at the time. I'm curious, particularly, about Bowen's role in providing the table of possible lines.

Schmidt:

Yes. That came on the occasion of the large red shifts, up to 2, 3C9 in April or so of '65. I might say, by the way, that I personally considered the detection of these large red shifts an achievement of considerably higher magnitude than the red shift discovery of 3C 273 itself.

Weart:

Why so?

Schmidt:

Because it was an exceedingly difficult job, considering the faintness of the objects, the weakness of the lines in the various objects, the fact that one didn't know the - As you know, the process was to go from 3C 273 to a few quasars with a larger red shift, in which one 'then eventually two, I believe) additional ultra-violet line was seen, and then to use that new ultra-violet line, together with all the ones already known in the visual to be able to find higher red shifts, in which again you find a new line in the ultra-violet. You build it up by steps, your knowledge. It's my feeling that somehow, either by luck or by tremendously hard work and luck to some degree, I managed 'in hindsight to myself) to solve that problem of going from the magnesium II line to the C III 1909 line, the 1550 C IV line, and then Lyman alpha. That took me only two years. With objects on which you don't know the red shift, 18th magnitude quasars with lines that were hardly visible at all, where a continual uncertainty was: does that line exist or not? With photographic spectra, very slow the typical exposures were between two and ten hours. I still can't believe that I did it in two years timer. And also that I didn't flub it. Because obviously, one could have made rather a discreditable performance, if you come out with red shifts of 2 and finally it turns out that they were .1 or so.

Weart:

I'll tell you an anecdote. You mentioned that after 3C 273 you gave a lot of talks. If my recollection is right, one of them was at the University of Colorado, where I was .

Schmidt:

Was it a summer school or not?

Weart:

I don't know, I seem to recall it was a regular physics department colloquium.

Schmidt:

Quite possible, yes.

Weart:

Quite soon after. Here was the man who had discovered it and in my mind, at least, it was very clear that you were the one, not somebody else. You were Mr. Quasar. You came, and you projected on a screen the spectrum of C3 273. And of course, it was a projection, and I looked at it, and I couldn't see anything. But since you were saying so, I could believe that there was in there some kind of very broad lines, fifty Angstroms or something wide and I could scarcely believe that one could identify where the centers of the things were let alone identify them with — I didn't know much about spectroscopy then, but why magnesium, and this other thing was supposed to be neon why not something straightforward, like iron or something?

Schmidt:

Yes, quite right.

Weart:

It struck me as highly suspect. Of course it turned out to be true . You know, I was a very junior graduate student at the time, but I wonder, did some people who knew more also find this rather risky?

Schmidt:

On my trip to Australia, which came so soon after the red shift discovery, I did give a colloquium or a speech at the University of Sydney or so, Australia University probably, and I remember that there was, in the back of the audience at the end of the lecture one exceedingly Britishsounding voice that said, with considerable disbelief, you know, that well, he uttered the same suspicion that these are the identifications; of course there must be other identifications. I murmured something about, you know, you didn't have that much freedom in the Balmer series, and that was of course for 3C 273 a damn strong argument. With others, bigger red shifts, where you had different things like magnesium II, CIII and CIV —

Weart:

maybe only two lines

Schmidt:

Yes, right. But, it's true.

Weart:

But you did not encounter these feelings around here?

Schmidt:

The speech I gave here in April '65, which was at a physics or astronomy seminar 'which was well attended, I daresay) was all essentially identical to the Letter I submitted around that time, in which I did, I think, give a very — you referred to the table that was with the Letter, where did the table come from?

Weart:

Bowen?

Schmidt:

Now, that Letter, I think, apart from the table that was input, Letter was very carefully written and gave precisely the argumentation that was followed in order to get there partly for my own defense, because I found it a bit extraordinary too, ~to suddenly get to red shifts of 2 . One object in which you think you have Lyman alpha a bit dangerous. So that table was important. But after that, the procedure, which was exceedingly systematic, was important; and I explained that here carefully. The table came not only from Dr. Bowen, but also from an article by Art Code in THE ASTRONOMICAL JOURNAL, about lines to be expected in space work. There was one other source, the ultraviolet spectrum of the sun. I would never have thought of the ultraviolet spectrum of the sun as that good a source for quasars or other objects, but it's amazing that many things that you do see in anything, in the ultraviolet, seem to be also in the sun. For reasons I don't quite understand. Dr. Bowen, who had of course been instrumental not only in the discovery of the explanation of the nebulium lines, but also in the collecting later on of data, lines, these terms, separation, wavelength —

Weart:

Bowen was a real expert on it

Schmidt:

I did ask him at that time which lines to expect in the ultraviolet. I still must have his notes about it, which was on a single piece of paper. And the most interesting line that he was kind of proud of, and that in fact was found, was this intercombination line, C III intersystem line, intercombination line, which is half forbidden. That was one, really, in his bailiwick. I'm not sure even that he recommended necessarily any others that have come up. I don't know whether Lyman alpha is obvious — I don't know about C IV 1550. But the C III 1909 line, he really predicted.

Weart:

I see. It's remarkable that out of all possible elements and lines, he should come up with it.

Schmidt:

Yes. That was very interesting.

Weart:

It's just that he had a remarkably good feeling for these things.

Schmidt:

Yes, apparently so. Of course there are surprises; the C III nonforbidden line at 977 has never been seen, or perhaps only once. To our tremendous disappointment.

Weart:

I'm also curious, to get away from these things a little, around this period you also had various collaborations with John Bahcall, some papers, on spectra. The constancy of the fine structure constant and so forth.

Schmidt:

Yes. That must have come a little later. It came soon after the red shifts. That must have been around '68 or '69 or so, as far as I remember.

Weart:

Yes, perhaps so, right. Maybe I should ask you about that later, then. Well, the next thing really was the space distribution of QSS' in the 3C catalogs. How did you get into doing that? You've mentioned that this went along with your previous ideas, your previous approach.

Schmidt:

Yes.

Weart:

How specifically did you come to do that ?

Schmidt:

That was soon afterwards, '67, that I was working on that. I think I was engaged at that time in trying to find out I'm a bit uncertain about what happened then, even though it's more recent but I think I was, at first, not expecting necessarily that the space distribution of quasars would be nonuniform.

Weart:

There had been a lot of talk, of course, about the ——

Schmidt:

Radio sources

Weart:

— yes, Log N - Log S -

Schmidt:

Right, but quasars were only 20 percent of all radio sources, 10 or 20 percent, so it was not in the foreground necessarily that these were it was clear that radio galaxies had to do with that, because they were the majority.

Weart:

But perhaps you thought of what you were doing as being somehow like a Log N, - Log S survey ?

Schmidt:

Yes, but since magnitudes and red shifts were available, it already soon became a different discussion in which I tried to sort of do the same thing you do in stellar statistics, where you make different bins of log in this case rows of Log Z, and then horizontally you have something like the magnitude. And then these inclined diagonals, on the 45 degrees, will be sources with the same absolute magnitude. And if there is a uniform distribution in space, then you'd expect that for sources of the same absolute magnitude, the numbers along these diagonals is simply the volume that's available in each of these Log shells or bins or Log Z bins. But the thing was complicated over there by the fact that there was at the same time radio selection, because everything was bright, of course, the nine flux units [in order to get] in the 3CR [catalog]. And I puzzled with that for a long time. I must have puzzled with that whole thinking; I'd have to look up precisely what the tone of my thinking was. But there was at the same time radio selection, and I made different assumptions about how the radio selection would work. It's strange that I cannot remember that too well, because of course I'm engaged in things like this every day now. But it led to this V/Vm method, where I found that it was possible, on the basis of quasars in such a radio catalog which is complete to nine flux units — and the quasar identifications being complete say to 18th or 19th magnitude — to come up with a quantitative V/Vm, which is the volume in the universe out to the object, divided by the volume over which it possibly could have been observed of within the limits of catalogue that you can use that as an indication of where it is in space. Nearby would be a very small V/Vm like a tenth, and near the edge of where it could be seen, like .9 or .99.

Weart:

This had not been done before ?

Schmidt:

That quantity had never been, in that way, derived before. It could have been derived, but

Weart:

It's very straightforward, once you see it.

Schmidt:

Yes, right. But the funny thing is that as soon as you have two limiting parameters, like limiting radio flux density and limiting optical flux density, you cannot work with Ns. Because it has to be Ns or Nm, and there's no way you can marry the two.

Weart:

So you had to somehow find

Schmidt:

I had to find something that married or compromised or took the two into account at the same time, and the V/Vm presented itself as an index for uniformity. Namely, if it's one half, it's uniform, if not, increasing or decreasing.

Weart:

So it was something that you kept thinking over and thinking over?

Schmidt:

Yes, this was really a long puzzle that finally resolved itself in that; and once you are fully through with it, it's as obvious as anything .

Weart:

Once you've done it, it's clear and nobody can argue with it.

Schmidt:

Yes, that's right. This is one of those pleasant things, where you have that feeling. Once this came about, it was as clear to everybody, in fact, as anything.

Weart:

There were two things. First you came up with this method, and then no doubt very shortly after that, wasn't a half ?

Schmidt:

That was the same occasion, of course. I already had from dirty arguments, that were not clean, that apparently the 3CR showed evidence for too much heaping up at the [outer] end. But how to make this quantitative?

Weart:

You had a suspicion of it.

Schmidt:

Right .

Weart:

Was there ever any point at which you said: 'By God, they do increase with distance'?

Schmidt:

Oh yes. Well, as soon as I did that V/Vm test on it, after I had thought out clearly what it meant and how it would have to be enunciated and executed, and then I did it, and I found .67 or .70 or so. It was really funny. It was great.

Weart:

Did this discovery change your own views about cosmology, about the possibilities of it being Steady State? Or had you already pretty strong ideas on that ?

Schmidt:

No. I, of course, thought it was an argument against Steady State . But Steady State was immediately thereafter, even perhaps even before that time but certainly thereafter, claiming that quasar red shifts couldn't be cosmological. Which was their only defense.

Weart:

I'm curious, did you ever give Steady State much credence? Before that ?

Schmidt:

No.

Weart:

Not before that either. So to you, it was simply another argument.

Schmidt:

Yes, in a sense. Yes.

Weart:

What are your current views, by the way, about the possible validity of anything other than the Big Bang?

Schmidt:

Well, the 3 degree background radiation seems to be strong confirmation. But there are problems with it that are not minor, such as an apparent velocity of US that is opposite to rotation, 300 kilometers dead away rather than 300 kilometers in the direction of rotation .

Weart:

Yes, well, the center of the universe is —

Schmidt:

but of course it may still be very uncertain . The fact that this stuff is so smooth, I think, is approaching incredibility, or rather is approaching becoming a major difficulty. And there's a continuing trouble, to some degree, although I don't quite understand the basic arguments there, that the stuff over there ought not to know what the stuff over there is doing [pointing in opposite directions] — that they've never had contact with each other. And why then are they the same to within a tenth of a percent ?

Weart:

This is a philosophical problem.

Schmidt:

Yes. So there are these worries about that.

Weart:

What about your own quasar arguments, in terms of evidence of quasar evolution; this seems like a strong argument for Big Bang.

Schmidt:

I think so, yes. It's a dramatic increase in number density, by a factor of say a thousand or so. It's extraordinary. It certainly points to a very singular early beginning, although we don't get that close to the beginning.

Weart:

Not necessarily a singularity, but at least singular.

Schmidt:

Something singular or remarkable about the beginning.

Weart:

Also I noticed in your work on these things, on this space distribution, you always assumed the cosmological constant equals zero, without any particular attention to it. What are your current views on that?

Schmidt:

I have no views on the cosmological constant. When you just asked me a moment ago whether I thought the Big Bang was right, although I think I would favor it, there is some question however what you mean by the Big Bang. If we are discussing as to whether percent concepts about general relativity are right, and about the overall view about the world, and that the only thing that has to be chosen is qo, the cosmological constant, and things like that it seems to me exceedingly unlikely that we are already that close. I find it just inconceivable that we are that close.

Weart:

I see. That partly answers my next question, which is, what you would say about qo, whether we're at all close to knowing what qo might be.

Schmidt:

I think we are not. I think 'especially, as you know, as seen from this coast) qo is low. But if you ask for any general feeling, apart from what the scientific evidence is at the moment, I think it has to be, what is it, a half, — namely, the critical case. Just out of philosophical ethnic reasons. I cannot believe that it is .356. It's such an important quantity, within the context of — current world models, that on that basis I think it has to be 0.5. Namely an omega of l, you know, the critical , case of density. That doesn't mean that I accept that in my work. In my work, I assume it's quite small.

Weart:

Well, one half is small. But by small, you mean one half or you mean less?

Schmidt:

No, I mean close to zero. I use for my work — for instance in quasars — I assume an empty model.

Weart:

I see. But that's just for convenience.

Schmidt:

No, I could also take the critical case and work it as easily.

Weart:

Why is that?

Schmidt:

Well, the scientific evidence at the moment — as seen from this coast, as I say, just to clarify that at Princeton there are people who feel that omega is very close to 1, perhaps between a half and one, which means a qo of a quarter to a half, which is the critical case. Somehow, most people over here, including Gunn and others, believe omega is quite low, like .06. All I'm saying is , if I have to choose if I had to bet, a longterm bet —

Weart:

Many, many years .

Schmidt:

Yes. I would say it must be the only remarkably significant value that exists, namely, the critical case.

Weart:

I understand, but this also says something about the universe itself .

Schmidt:

That's right. But then I should limit immediately the importance of this great statement I Just made, by going back to what I said earlier namely, that I don't think we really are necessarily on the right track, in detail, so that qo and omega really mean something.

Weart:

That this program will tell you everything about the universe, by measuring two or three numbers?

Schmidt:

Yes; and I don't believe in it.

Weart:

Would you prefer that the universe be closed or open? Do you have any preference?

Schmidt:

Not the faintest preference, no.

Weart:

Either way is all right.

Schmidt:

Yes. Although again, from my esthetic, philosophical, non-thinking prejudice, I would say it must be exactly on the -

Weart:

Because there must be something to determine what value it is.

Schmidt:

Yes. That's right.

Weart:

I understand. I very much understand. To get back a little bit again to the space distribution, you used some of Sandage's photometric data, and I wonder, was this particularly important to this program?

Schmidt:

That was on the 3CR objects, I think. Yes.

Weart:

Right. When I first looked at your paper on the space distribution I thought, my goodness, I suppose in principle anybody could have written this from published data. But then as I looked at it again, I thought —

Schmidt:

I think, although he may by now have published all his photometry, in the beginning he was very slow in getting his photometry out. So it was very hard for — I cut you off — perhaps you could finish this thought?

Weart:

Then in some other cases you cooperated with Sandage and so forth. How does this work, that you get his photometry? You ask him for it? Does he come around with it, or what?

Schmidt:

Well, that must have been, again, other quasar fields, perhaps. I don't know. I don't know exactly what you refer to.

Weart:

Let's make it a more general question. For example, here's a lot of people at Mt. WilsonPalomar taking data, and many of them are concerned with sort of the same kinds of objects.

Schmidt:

Yes.

Weart:

How is it decided who will look at what object, and what is done with whose data when it comes in?

Schmidt:

It is not .

Weart:

It's strictly up to each individual?

Schmidt:

Yes. It really is, yes.

Weart:

Are there any gentlemen's agreements or customs?

Schmidt:

There are probably, at times, gentlemen's agreements, that either may have been specifically discussed, or not. And therefore it doesn't always work out right. It depends entirely on to what degree there is pressure in the field. In the beginning of quasar astronomy there was a lot of pressure at times, so that if one broke a gentlemen's agreement, or did something that one didn't realize was part of a gentleman's agreement because it wasn't talked about, it could lead to some friction or difficulties .

Weart:

Was there a feeling that certain objects belonged to certain people, or ?

Schmidt:

In a sense. But such difficulties or pressures get gradually less in a given field, as the urgency of it decreases.

Weart:

Has the existence of other observatories had an effect? At one time really, to be observed, it had to be observed here; but now there 's competition from outside also.

Schmidt:

Yes. I think in general, that's very good, for all sorts of aspects of observing, because if there is no competition from other observatories, people tend to sit on their data too long, and it never is healthy. It's best to share it with the outside world, even if it's not fully discussed yet, perhaps.

Weart:

What have been the relations, what are your relations in particular, with people who had been working on cosmology? Here the quasars come along, and suddenly it looks like everything will be changed in cosmology.

Schmidt:

That's not quite right in fact, I could almost turn it around a little bit. Most people who discuss quasars in their cosmological context point out, and I think much more often than I think is necessary, that they are useless for cosmology. That's because those people take the limited view that cosmology consists of Ho and qo —

Weart:

for which they are , up till now, useless.

Schmidt:

Yes, that's right, because they have a large range of absolute magnitudes. And you will find in most popular texts that authors set up a straw man, and then shoot at him. In most texts about quasars, you will find that astronomers at one time thought that they could be used for the determination of qo. And then they say, 'However, since they have such a large range of absolute magnitudes, they are useless for that, and therefore of no value to cosmology.' Well, that is ridiculous, because the first five or ten quasars showed that there was a big range of absolute magnitude. And we said to each other, 'Hey, that's too bad.' You know. There's nothing you can do about it. But no sensible person ever thought we'd get qo out of them. So the impact on cosmology has definitely not been on what many people in the more narrow sense consider cosmology, and that is the geometry of the universe, the size and the deceleration. However, I think that if you have a wider, broader view of cosmology, including the formation of galaxies, and the formation of anything in it -

Weart:

Cosmogony, so to speak.

Schmidt:

Yes. Then quasars play a tremendously important role, because I think it's the only kind of object for which you can take a group, and say, 'From the study of the individual members of this group, I find that the rate of formation, or the rate of existence, has been like that,' and then you have this very steep evolution curve . There's nothing else, no other object, that you can point at in the universe that does that.

Weart:

It is remarkable. Have you had much interaction with this geometrical program, 'Sandage's program really is how I think if it) have you had much impact on that, or has it had much impact on you?

Schmidt:

No, not either way. I have felt for a long time that it was very dubious one could get to know that way, because of the uncertainty — because of the assumption that the luminosities are identical, here and there. Things now have become terribly bad because, while stellar evolution tells you that you change this way, the theory of Ostriker's about cannibalism, [of galaxies] suggests it goes the other way. So it can go any way you want.

Weart:

Right. Sandage himself will tell you that.

Schmidt:

Right. So I think by now, it's almost the other way around. You adopt some value for qo, and then it tells you about galaxy evolution eventually.

Weart:

Aside from yourself, how has Sandage and his program been regarded around the observatories, around Pasadena?

Schmidt:

Oh, as a very solid one. If anything, it may have taken too long, in a sense. There is some question, I think, as to whether any program should go on for more than on the order of five or ten years .

Weart:

Oh, is that so? That's rather different from the way people would have thought, let's say, in the thirties about astronomy, I suppose.

Schmidt:

That may be . But look here, I am not saying that longterm programs should not be undertaken. In fact, we believe since we have some autonomy at the observatories here, we believe it's one of our main missions to do long-term programs. But I think a long term program can be, in a sense, perhaps too long, if it goes in the same direction all the time. I'm sure that if Sandage had not been so terribly involved in this way of determining qo, he would have realized three or four years earlier that it was sufficiently doubtful that it was probably not worth pursuing to the fullest any more.

Weart:

I'm interested in this because I'm interested in what you were saying earlier about the realization of the problem of evolution of all these things. One of the things that you've been working on we talked about the space distribution, but we haven't talked yet about your work on the luminosity function of QSS's, QSO's, radio galaxies and so on. Again, how d id you get into this? When you began this, did you hope to work towards, or are you now hoping to work towards, an evolutionary scheme that will encompass all of these objects?

Schmidt:

Yes.

Weart:

This was the original intent also?

Schmidt:

You have asked several times today whether the original intent of a particular thing was to do this or that. I think in every case that you ask this question, I've probably hesitated and thought a bit what was the original [intent]? And I conclude from that, that in my cases, at least in my case, one starts with a particular program, because you see something in it that attracts you; you feel that either through observational effort or by particular way of looking at things — — that you feel you can make sort of a special contribution, either by observations or by a special approach. That doesn't necessarily mean that at that moment, even when you undertake it, you can really see where it is leading necessarily, and that you see: Yes, it will impact on the evolution of radio sources, or the formation of galaxies. Certainly, in my case, I would not normally think through things that far in advance. In other words, I don't have a plan, in general, for the next ten years, where I see that once I get this, that I can then embark on that, and that leads me — The interest, again, I think, is often that you see you can do something, where you feel that the community has left a gap or a hole, or where you can penetrate through your own either insight or observational possibilities, or whatever. So you do it . And of course, you don't stop looking around while you do it, what impact it has. And then sometimes it turns out to have a rather broad impact. Like, I don't think when I started on the quasars I had any feeling or expectation that their space distribution would be so extraordinary. You might say: well, look here, you knew that the rad sources in general did that. But nonetheless, I did not — I wanted to check carefully, on the 3CR. I wanted to understand exactly the identification content so many radio galaxies at that magnitude distribution, and quasars also to see whether we knew all the things in the 3CR.

Weart:

Right. To some context it's the wish to do something systematically, which has, been done in bits and pieces.

Schmidt:

Yes . That's right to bind things together, to come up with a simple description of things. But I don't think in general I plan that far ahead, that I know I'm going to work on the evolution of radio sources or galaxies or so. It won't be long till you find yourself doing it, of course.

Weart:

Tell me, now that you are doing it, do you think that there is some chance of fitting things together into a single evolutionary sequence, from the quasars to normal galaxies?

Schmidt:

Yes, I think so. Whether we will be able to do it, I doubt it. It must be extraordinarily complex. But I still hope and feel that quasars have to do with the birth of galaxies.

Weart:

All galaxies ?

Schmidt:

Well, that of course is a good question. Perhaps only a part of the galaxies . It's a heck of a problem to resolve. But it seems very tempting that something like that happened, and to go after lt.

Weart:

By the way, speaking of quasars, the word itself, 'quasars' the first time I saw it in the Director's reports here was 1967. I guess it was used before then, and then there's your paper in APJ in 1970, where Chandra [Chandrasekhav] put in a footnote saying that APJ regrets that it must now concede the use of the word quasar.

Schmidt:

Yes . But don't forget to read the second sentence, which was a great where Chandra gave me quite a stab, in exchange for this concession.

Weart:

'Now it has been defined' ?

Schmidt:

Yes . He said, 'With Dr. Schmidt's exact definition' you know, and it wasn't an exact definition I just needed the darn thing in there, because I was talking about radio ones, optical ones, and I said, 'Let's call the whole phenomenon together quasars'. You know.

Weart:

Where did the word 'quasar'come from, by the way?

Schmidt:

Jesse wrote an article for SCIENTIFIC AMERICAN which appeared in December, 1963. It was at the time of the Dallas Conference. In that article, he used the word he and I had agreed upon, I think, namely, 'quasistellar radio sources.' But it was a terribly involved term, of course. The word 'quasar' was launched by 'Little Chiu', I think, of Jastrow's Space Institute. We call him 'Little Chiu' because over here at UCLA, you have the elementary particle theorist, 'Big Chiu'. Little Chiu did it in an article in PHYSICS TODAY in January 1964, a month later, in which he reported about the Dallas , Texas Conference — which was the first Texas Conference — at which there had been half a session spent on finding a name for the confounded thing. And all the names had been unfortunate. Nobody liked any of the names proposed there. For the sake of that article, Chiu said, 'Well, let's call them quasars.' You know, an acronym of this and that and somehow it stuck. We didn't take kindly to it in the beginning either, for around three or four years.

Weart:

I see. But eventually you were willing to go along.

Schmidt:

I think I was fairly early, locally, here, to give in and feel we should go that way.

Weart:

Interesting, because for some reason, I don't know why, the way things get named always seems to create problems for people.

Schmidt:

Highly irregular, yes.

Weart:

Let's see, you've also done some work on the absorption lines in quasars.

Schmidt:

Yes. Once in a while. I think Jesse and I were the ones who were first to propose that in one quasar, 0237 23, there were in fact two absorption line systems. Because there was one around, then came another one around, and it was on a flight from here to New York that I got together with Jesse, and that we decided that both systems had to be there. It was a bit of a revelation.

Weart:

I see. Has this had any effect on your ideas about quasars?

Schmidt:

No. As you know, it's either stuff that is shot out by the quasar, which makes them even wilder; or it is stuff that is floating in between. If so, there is much more stuff in between than we thought. It's true, of course, that the absorption lines have never been fitted into a local hypothesis, which I think is an important difficulty for the local hypothesis; to have all these red shifts in between zero and 2 or 3, must be an incredible difficulty for the local hypothesis, which it has never faced.

Weart:

More recently, I find you've been doing work on the mass of the galactic halo.

Schmidt:

Yes.

Weart:

And dwarfs.

Schmidt:

Yes.

Weart:

It seems like a shift away from quasars. It's a new topic. Have you felt that quasars are perhaps not such a simple problem any more, that there's not as much to be found there as there was?

Schmidt:

I thought for a while, I must admit, perhaps three or four or five years ago, that I ought to stop quasar work. But then -

Weart:

why?

Schmidt:

Well, since I thought perhaps I'd done the most original or good work in it that I could do, anyhow. But that was forestalled, I think, by the fact that I then found that certain types of quasars, these flat spectrum ones, have very much less evolution; by which time my appetite got whetted again, and I realized things weren't done yet. At the moment I think I'll stay in it, because we are at the moment engaged in opticallyfound quasars, and that is entirely a new technique again, that's very interesting. But to go to the halo stars, yes, the halo stars, was typically, I think, a case where I found, after listening to discussions about massive haloes, that it was a field in which I could do something, simply because I suddenly realized that I had an insight that I could use to get something that people didn't have yet.

Weart:

But you must have been thinking about it already, to have the insight.

Schmidt:

Yes. Well, in the back of one's mind, one envisages all sorts of problems at the same time.

Weart:

Does this come out of your interest in evolution? You became interested in evolution of galaxies, this direction?

Schmidt:

Well, that's a thing that perhaps is also in the back of my mind here. But it was mostly that I realized that it was ridiculous that there was no luminosity function of population II yet. There was no field luminosity function. It seems there has been a field luminosity function for the disc since Kapteyn and van Rhijn. It was ridiculous not be able to produce one . When Ostriker threw out the tease, or the taunt, that this heavy halo that he wants might be consisting of small stars -

Weart:

I see, they may all be there, and just not looked at.

Schmidt:

Right. I suddenly realized that, in the proper motion catalog, there's most of the material you need for that. But I had to invent a new way of looking at the things, because no methods by which you ordinarily determine the luminosity function was suitable because of the funny proper motion selection. So there was another case, like in the radio and optical selection for the radio sources that I faced with the V/Vm method. Over a year I found a method to attack high velocity stars and come up with a luminosity function. It was great fun. But it was more the fun of the exercise that I realized that I could do something that nobody apparently was seeing and that yet had an impact on a very modern problem namely, the mass of the halo. We now know, thanks to that particular investigation of mine, that if you want to have a massive halo, that is made up of stars, that the luminosity function that I now have will have to be extended below .1 or .2 of a solar mass, with the same slope, to l/lOOth of a solar mass stars in order to get that kind of heavy halo.

Weart:

Which may in fact be the case.

Schmidt:

Which may in fact be the case.

Weart:

A great many very small things floating around.

Schmidt:

That's right. But that was something that wasn't known until that time. But I only stepped in there, I think, because I saw a chance to do something that was sort of fun and not generally realized. And there was a finite amount of work, which is also nice .

Weart:

One last question about quasars and galaxies and so forth. This idea which I guess began with Lyndon Bell around 1969, that all galaxies have something peculiar at the middle of them - if not a quasar, then some sort of strange black hole and so forth. Has this idea had much impact on you?

Schmidt:

Well, yes and no. It certainly, reflects a feeling that I think has indeed existed, perhaps even since 1964, that quasars and nuclei of galaxies have remarkable similarities except for a certain difference in scale. Shlovskii already in 1964 talked in an article about a miniquasar, in Perseus A, in NGC 1275's nucleus. And soon after of course it was discovered that nuclei of some galaxies are variable, which we had never realized. And therefore these size arguments, based on variability rate, could have been used many years ago if we had looked a little more critically at photometry of nuclei at the center of galaxies. Which is very difficult, because the seeing, etc., and the nebulosity around it makes it very difficult to do accurate luminosity of a nucleus . I'm sure that some people have seen variations, and have said, 'Boy, it's difficult to do that in the middle of a galaxy.' You know. 'That shows how difficult it is the thing seems to vary by .2 magnitude.' I think perhaps LyndonBell''s realization was — on the basis, I think, he put up certain numbers that might argue that almost every I'm not sure whether he did that. I've done calculations like that too, and it is certainly possible that almost all galaxies have sort of a quasar remnant in there at their center, although it's somewhat easier to believe it's only a few percent of galaxies that have that.

Weart:

What do you think the chances are that this thing, whatever it is, or quasars in general, have to do with black holes?

Schmidt:

Well, it's a tempting argument, I think. I think it's perfectly possible. For that, again, I would guess that one has to count rather badly on general relativity being correct, because I'm sure it determines that one believes that there are massive stars that you don't see there has to be a black hole. That black holes really can exist in nature. But if so, it seems a very tempting argument, I think. I have nothing against it. That doesn't necessarily mean that I absolutely believe in them, but it seems a very fruitful idea to have in mind.

Weart:

I get the impression from what you've said that you don't ever believe entirely in general relativity, let's say in the standard formulation?

Schmidt:

Yes. That's sort of funny, because earlier I gave the impression that I never had any education in it. But I've been impressed by some people's arguments that general relativity has been checked only so lightly, and that all sorts of first order arguments, like the deflection of light from a star near the sun and the other one, what the heck is that, the other test ? those are the first order tests that come up in any theory of gravity. It's only — the shift of the perihelion of Mercury which is a second order test. There's a relativity group of course over here under Kip Thorne that is investigating all sorts of theories of relativity, and I think that they find that there are certain classes that simply cannot be dismissed. So I don't know.

Weart:

I'm asking all these things because I have a strong impression that not only what happened 20 years ago is of historical interest, but also what's happening now. I can't go around and ask people 20 years ago what they were thinking in the present, but I can do that now, put it in cold storage for later people.

Schmidt:

Yes, that's right.

Weart:

OK, we're getting near the end, but I still have some questions of a more social nature. In the quasar field, let's say. One thing: after 3C 273 and so forth, did you get more telescope time than before?

Schmidt:

Yes. In fact, I went up to a peak of about 36 nights, I think, around 1967 or so .

Weart:

All dark nights?

Schmidt:

Yes,~right. Which to me is some vindication of our system of allocating telescope time, in a sense. I'm engaged in this quite a lot myself these days, and we often accuse ourselves of being unable to adjust to changing circumstances. We say, 'Well, we seem to give each other' which is after all what we are doing 'always about the same amount of time; therefore, it almost becomes a right, rather than something you acquire by the excellence of your work'. Nevertheless, the system 'our own system, that is) is apparently sufficiently flexible, and cognizant of the really interesting stuff, that during that heyday of things, I got somehow as many as 36. At the moment, I get 10.

Weart:

Was this because they just gave them to you, or did you push for it?

Schmidt:

I pushed, also. I pushed . But as the only way you push here is by putting in a request. And you don't put any strong language to your colleagues, about the grandiosity of your research. You just indicate what you want to do, and you can either push heavily, by putting in many nights per quarter, or you put in lighter pressure by putting a smaller number of nights in.

Weart:

I see.

Schmidt:

That doesn't mean that if somebody suddenly started pushing heavily, that he gets a lot. We've seen that once in a while, and then the observatory committee doesn't react at all, or it decreases things slightly.

Weart:

But in this case, you asked for a lot and they gave you quite a lot .

Schmidt:

Yes, right. Right.

Weart:

Also, in the quasar field, how have you usually heard of things. Do you usually hear of things before they're published ?

Schmidt:

I used to. It's slightly less these days, because I'm not perhaps that much at the center of things any more, although I'm still quite well informed, I think. But as one stuff that has to do with fantastic things, in BL Lac [Lacertae] objects, funny absorptions or so that happened, or double absorption systems, or an absorption and an emission system that have a funny relationship in a BL Lac it sometimes can escape me for a couple of months, and I hear about it and say: 'By Jove, you missed that.'

Weart:

I see. But in the heyday how did you hear about things? Was it preprints?

Schmidt:

Mostly preprints. And people would call me and talk about their work. But mostly by preprints, I think. Once in a while, by letter.

Weart:

I see. But letters were not the most frequent way?

Schmidt:

No, the preprints really were, I think. Yes.

Weart:

No people save their preprints any more? Do you throw out all your preprints?

Schmidt:

I have an awful lot of preprints. But when I''m going to move out of this office by next July 1, I think I'm going to throw away most of them. Because I realize, I don't even look at them.

Weart:

Yes. I wish there would be someplace which would save a collection of all preprints, just for the archival records. Because they're not always the same as what the final paper is.

Schmidt:

True. It would take a heck of a lot of study to find out, of course .

Weart:

Oh, to check, yes . One would have to look up an original paper. Well, I don''t know, that's another problem. We really have that problem in high energy physics . It used to be, of course, that if you heard of something new, it would be probably by letter. But now, that's probably the least common way of hearing about it.

Schmidt:

At the moment, it is. In the heyday of quasar things, I think I was fairly often called and fairly often got letters from people, yes.

Weart:

Would you call people sometimes when you had something?

Schmidt:

No, not usually. I think I usually sent out preprints.

Weart:

It's a little different; you have many people to talk with some here, but of course some people in other places need to call somebody.

Schmidt:

Yes, that's quite true.

Weart:

You mentioned something earlier that was interesting, and that is, that the character of a night at the telescope has changed. I noticed you did a study with a Princeton team, using an integrating television camera. That's the sort of thing you were talking about?

Schmidt:

Yes.

Weart:

There's another thing here. Not only does it work the night different, but also, you're cooperating with people right there in the mountain, are you?

Schmidt:

In that case, that was the case, yes. That was a very special case, because they had a beautiful instrument that they wanted to try something with, so they managed I imagine that got me to put in a few nights, so we did it together. In the case of modern instrumentation, although one needs certain technical personnel to help you, perhaps, during; the night, it usually does not have the character of a cooperation. We have a programming expert here who often assists these days at the SIT spectrum observations that we do.

Weart:

I see. But he'd be sort of in the same position as your night assistant?

Schmidt:

Yes.

Weart:

Are you continuing to use photography primarily in your work?

Schmidt:

No, I use it very little. We usually now use the SIT which is Silicon Intensified Target video camera spectrograph.

Weart:

Right . But using one of these is essentially like using a photographic plate, in the sense that you don't need somebody else to help you use it?

Schmidt:

We need somebody to do the reductions while the observations are going on. It's a system that allows you to see the spectrum almost immediately, and to even do the final reduction of the whole thing, while the observations are going on with another object. But if you ha ve a busy program you are too busy to do that yourself and it requires another person to do that.

Weart:

I see. So your night really becomes much busier.

Schmidt:

Oh, tremendously busy .

Weart:

You're thinking science instead of pointing the telescope.

Schmidt:

That may be, but we also can do observations, sometimes very fast. Only last week, I worked with my postdoc, Richard Green, on a number of his bright quasar candidates, and in the two nights that we had, I think we made 86 settings. Which is an awful lot of settings .

Weart:

I see. Well, it's a curious thing about the 200inch. A large telescope can either be used to see something that nobody else can or to see a lot of things.

Schmidt:

That's right. I remember that Bowen, in the early days when I was he once happened to be up [on Mt. Palomar] and I showed him a spectrum of a very faint galaxy, a radio galaxy; and the spectrum actually was a failure. You know, it was underexposed, there had been a five hour exposure or so. He wanted to see it, so I showed it to him. And I was a little embarrassed, you see; he was the director of the observatories. He looked at it, and then he turned around and he said, 'I''m glad you're doing this work. It's really at the limit of the telescope.' He said, 'I think there are people 'and he had some people in mind) who really don't make use of the fact that with the 200-inch you can go farther than with any other telescope. So I felt encouraged, in a sense. And I do feel that's the way the 200inch ought to be used, for limiting problems as much as possible. Yet at the moment, I find myself with a problem with Richard Green, who's done this bright quasar survey with the 18inch Schmidt, coming up with what I think eventually will be between 5 and 10 thousand candidates. There's 4 or 5 thousand candidates now, I believe. And we have to look at the spectra. Now, you can go to a small telescope and it will take 12 years, but I don't feel like that.

Weart:

I understand .

Schmidt:

And it is urgent, because the quasar statistics depend on that. The bright end gives you information about this, the faint end about that. We need to have solid statistical information on the bright end, since almost all the UV candidates we get at the bright end are white dwarfs. You have to wade through them in order to find — And we get beautiful white dwarf statistics by the way.

Weart:

It sounds perfectly reasonable to me. The 200inch takes a large number of photographs —

Schmidt:

that's right we try to be as efficient as possible. We try to make a minimum time of transition between one object and the other, and there we go again .

Weart:

I see . Tell me a little now about funding . This gets into the question of new instruments and so forth. Usually one of the first things I look at in a paper, in preparing these interviews, is I look at the end to see who funded it.

Schmidt:

Yes.

Weart:

And in your case, there's nobody.

Schmidt:

That's not true any more. You have to look at the later ones.

Weart:

I noticed, that in fact you've got some NSF grants.

Schmidt:

Yes, I did. Since four years I've had an NSF grant, that has been renewed and that is up for renewal.

Weart:

This funded the publications on quasars with Dennison.

Schmidt:

That's right. That's right . Originally with Dennison, now without him.

Weart:

Tell me about that. What caused this change, applying for funds?

Schmidt:

Well, this may be another reason to keep this information somewhat private for a while.

Weart:

Another section that we'll decide on later on.

Schmidt:

Right. It became clear to me, somewhat belatedly really, that considering the very poor situation in which the observatories find themselves, I ought to go out and get funds for new instrumentation. The observatories -

Weart:

 why you? By that time, you were Executive Officer for Astronomy?

Schmidt:

Yes, but other people do it too. Let me explain

Weart:

people in general should?

Schmidt:

That's right. The observatories of course are funded privately by CalTech, for the Palomar and Big Bear half, and for the Mt. Wilson and Las Campanas side by the Carnegie Institution of Washington. In neither of these two budgets of these private institutions is there any room any more for new instrumentation, or in fact for maintaining old instrumentation. There is no money in there for instrumentation.

Weart:

Only money for salaries and essential maintenance?

Schmidt:

Yes, but the maintenance is mostly for roads and things like that. So the situation is exceedingly tight, and in these days of technologlcal progress with detectors, SITs and SEC vidicons and CCD's etc., it would be too bad to not be able to partake in the benefits and the fruits of these advances and come up with vidicon observations, etc., or whatever you want. In order to stay competitive — but it's not just competition, it is that once you know that the efficiency can be improved, you sort of feel delinquent not doing it. We need the money. And the only way I see that we could get it was for me and others to go out and get a contract, and ask for money from the National Science Foundation for instrumentation. That's how this SIT vidicon spectrograph has been partly funded, not only by my contracts but by severa1 others too. By Gunn and by Oke. And that has been absolutely essential.

Weart:

I gather there was some reluctance originally to do this? To go out?

Schmidt:

No, that would not apply to the CalTech side to which I be long here. No.

Weart:

I see. It was simply that you hadn't done it.

Schmidt:

I just hadn't done it, and nobody had put any pressure on me over here to do it. But I realized myself I ought to do it, because we are in a terribly tight situation with instrumentation. On the Carnegie side there has been until now, somewhat of a policy that it does not encourage or look favorably upon acceptance of federal money. But that is not a fixed policy. It sort of inhibits, a little bit, that process. Not on the CalTech side .

Weart:

All right. I want to ask you about — particularly since you became Executive Officer for Astronomy in 1972, but also what you knew before that — on the CalTech side, what effects there may have been from cutbacks in general science funds? Has it had any effect on the department — never mind the observatories but just the department in general?

Schmidt:

Yes. Well, we did have a lot of postdoctoral fellows until that time, probably together in radio astronomy and optical astronomy on the order of 15 or so. And it was eventually to be cut to on the order of six or so. [The ones left are] Mostly in radio astronomy. '

Weart:

I guess I was one of the postdocs here during the more flush period.

Schmidt:

That's right. You worked with Hal Zirin?

Weart:

I worked with Hal Zirin, yes. I was over here [in Robinson Laboratory] all the time, and yet actually I was supposedly at Mt, WilsonPalomar.

Schmidt:

A complicated organizational arrangement.

Weart:

Yes. But anyway, there was a cutback in the number. What about any changes in the types or ambitions of the astronomy students that have come through?

Schmidt:

I don't think that it has changed much. There are slow fluctuations, admittedly, in the ambitions, I think, of our graduate students. But I don't know, with the small numbers we have, whether it's not just a statistical fluctuation. We again find some of them exceedingly bright and really ready to go out in the world and do astronomy. I don't think there's much of a change. ~o.

Weart:

What about the undergraduates? Since you began teaching here, around 1960 or whatever, have there been any changes in their character? Those who take astronomy?

Schmidt:

Yes . To me, it looks like it. But there is the danger that it's mostly in yourself, of course. After all, the students are getting younger every time while you don't change your age, or the other way around, isn't it right? So there's more and more of a distance . I've found I've heard it from others too, and I still don't know whether it's true, because we all suffer from this systematic effect I just mentioned — that undergraduate students seem to be less and less inclined, gradually, to ask questions, and to involve debate and so on. I thought when I first came, that they were quite ready to put up an argument in class, to defend views, or come up with somewhat aggressive questions and statements. And gradually, they seem to have stopped doing that. Again, it may not be perhaps they do that with the younger professors . I don't know.

Weart:

I know very well that there was a period when professors were complaining that students were more inclined to ask questions. So it might be a universal effect.

Schmidt:

Yes. It may be a totally universal effect. I have to ask some of the younger professors, whether they have a feeling - but then, how can they measure it, because they never knew, in case there's a real effect, what students did in the late sixties/middle sixties?

Weart:

I think if you asked most professors in 1965, they would have said that students were asking many more questions than 20 years earlier.

Schmidt:

OK. I think it's probably a true effect of the times. It would be interesting if it went together with this general sort of increased awareness of things by students in the mid-sixties and late sixties. It's quite possible.

Weart:

So you notice any difference in attitude towards astronomy, specifically either among students or people you talk to anywhere?

Schmidt:

Not among students. Somehow among students I think it's like it always has been, that there is some calling they have, some attraction. It's almost like being a missionary, without necessarily wanting to convince other people. They're just set to go. They don't doubt that they want to do astronomy. You accept that they are in this same frame of mood that you are in all the time, of just wanting to do it. There's no doubt that you want to. With other people I think that in a sense, astronomers suffer all the time just a slight little bit from the fact that it is, after all, not that clear how useful astronomy really is. And now, these periods in time, especially when funding gets tight, or when there are difficulties in the suburbs or people are poor or whatever that the non-relevance 'whatever that means) of this subject comes up again. Astronomy must suffer from this, it seems to me, so much more than fields like physics and chemistry, where it's abundantly clear that these are fields on which society depends, critically, immediately .

Weart:

High-energy physics aside .

Schmidt:

Yes, high-energy, that's true. But even there can argue that you know, it will soon impact on society through physics and engineering and technology.

Weart:

It is remarkable that the two fields which cost the most per scientist are highenergy physics and astrophysics, which are the farthest removed from -

Schmidt:

Yes. That's why one may feel doubly aware of all this.

Weart:

Are you ever made to feel aware of this? The nonrelevance of astronomy?

Schmidt:

I think it happens when any of us goes out into the community and talks with people, that we, you know, do not usually meet, like our own colleagues at other universities, or artists and other professionals but when you literally go out in the country and meet people that have absolutely no connection with university or professional life. And they're sort of aghast at what you're doing. Sometimes I am too.

Weart:

You mean 'why bother', that sort of thing?

Schmidt:

No. But it is kind of strange, to sit here on the earth and peer out and to study what's around you in the whole universe. It's sometimes fascinating to think about your role in this business.

Weart:

What do you think about it? What is your role?

Schmidt:

Sometimes you almost feel that your role is a cosmic one, because the study of the overall reaches of the universe is done by a relatively small number of people, and sometimes you can't help wondering whether there are characters in other galaxies who peer out in the same way, and learn about the distant reaches of the universe. You wonder whether they all find the same thing, or perhaps they start with quasars and finally discover their own planet, who knows?

Weart:

Some astronomers, I can't remember who but somebody here, said to me, 'You know, on this world there are three billion people who are concerned with the surface of the earth, and maybe three thousand who are concerned with everything else in the universe.' That sort of feeling.

Schmidt:

Isn't it odd? It's crazy. While the universe is so much bigger.

Weart:

Yes, that's right . That was the idea.

Schmidt:

Yes, I have that feeling once in a while. I also have strongly the feeling that on the earth, you're so much a link in history, because in science more than almost anything else, certainly in astronomy, you build on what your predecessors did and the concepts they built up from the observations, sometimes very scarce. Then you contribute a little, you put in a couple of links there; it's all being knitted together, and a few of the stitches are yours; and then the fabric goes on. It extends into the future. Perhaps in a sense there is a wish to be not entirely anonymous in this whole business, but to have contributed, you know, one or two stitches to the whole fabric that you say, 'Well, they are there'.

Weart:

Since you became Executive Officer for Astronomy, have you done more popular talks? Have you been called on to go to things that might be involved in fundraising or popularization?

Schmidt:

Oh, fundraising once in a while, indeed. And I do give sometimes talk about physics and astronomy that otherwise couldn't have given. But I have not extended my activities into, say, talking to Rotary Clubs or Lions Clubs or the women's clubs or so. That somehow hasn't happened, and I have not particularly attempted to see assignments like that. But obviously, I will talk, once in a time, to a foundation or to trustees, or to very rich individuals.

Weart:

Would you go to dinner with these individuals, that sort of thing?

Schmidt:

No, usually not. It depends. Sometimes these are larger occasions, and sometimes they are fairly private occasions. It doesn't happen very often. It should happen more often.

Weart:

What do you think it is that encourages a foundation or a very rich individual to give money for astronomy?

Schmidt:

Since rather few do it, I can't quite say that. In the case of individuals, one often hopes that having their name attached to a building or another structure will be of interest, that something that's scientific or around the campus, a lasting structure.

Weart:

In that case it could as easily have been a library.

Schmidt:

Indeed, it need not be astronomy. What attracts people to astronomy, again I can't say. It is, by the way, relatively few these days that find themselves attracted to astronomy. I must say that biology and medicine seem to be by far the most popular subjects to most people.

Weart:

I don't think that's novel, by the way. I can tell you from my reading of history, that's often been the case. But those that are attracted, is it the same sort of thing that attracts you, do you think?

Schmidt:

I wouldn't be surprised, in fact, to a degree. Or at least that feeling, that emotion, that the general public has about astronomy or something mysterious . You know it has to do with your origins somehow, but you don't quite know. It's something that fascinates people .

Weart:

Now, a few questions generally on the evolution of both Hale Observatories and CalTech, since you came here 20 years ago — have they changed? Take both of them together or one at a time.

Schmidt:

The observatories, that is, the Carnegie side, I think there's no doubt that it suffered a lot with the retirement and the death of Baade and Minkowski, who were just extraordinary, you know, outstanding astronomers who put their stamp on Santa Barbara St. very clearly.

Weart:

They were still here and still active when you first arrived.

Schmidt:

Yes. On this side, I think that the department here has become stronger throughout those same years, with the attracting of, say, Sargent and Gunn, to where things are now not out of equilibrium any more. It used to be, I think, that Santa Barbara St. dominated quite strongly, in the earlier days.

Weart:

In fact, at one point there was no department here.

Schmidt:

True. And gradually of course it was built up. But I think now that equilibrium has been reached quite satisfactorily.

Weart:

Any changes in the way things are done or decided? You've only been on the Observatory Committee since 1969, but perhaps you've observed some changes in the way the Observatories are run?

Schmidt:

Yes; the relation between the two institutions, through the Observatories, is something I don't want to discuss at all. Because of my impending role as Director —

Weart:

OK.

Schmidt:

But it has not been an easy association at all, over the last five years. And in fact, it will be one of my main tasks to get a smoother operation going, on the whole. Since that's really before me rather than behind me, I don't want to talk about it .

Weart:

OK. Of course I can appreciate that. I just wonder, before your new post, do you think there are definite expectations of changes which will be made? I'm talking now about the past, so to speak, to the point where you took the post.

Schmidt:

No, I don't think so. I foresee very strongly a period of consolidation. In the sense that, with the Las Campanas Observatory that Carnegie has built in Chile, there is a general feeling across the Observatories that we have reached for a while at least the maximum of facilities that we can handle. We hope, in fact, that we didn't overdo it too much. Which means that we must consolidate and carefully study priorities with the too little money we have. We particularly have to do this, because our position relative to Kitt Peak and Cerro Tololo, as far as the funding picture is concerned, is critical. As you know, Kitt Peak and Cerro Tololo have a budget of 13 million [dollars] whereas that of the observatories here can be estimated at about three. The disparity is so enormous that we must be at a disadvantage. So we have to be determined and selective, and consolidate very carefully, under the circumstances.

Weart:

I understand.

Schmidt:

Private universities and colleges don't have an easy -

Weart:

private institutions in general

Schmidt:

easy going, at the moment. And the federal agencies have not accepted at all that they should give any regular support to optical observational astronomy at all. In contrast to Xray astronomy, radio astronomy, gammaray astronomy. Everything else. We'll see. Perhaps that can be changed . But it's not going to be easy.

Weart:

It'll be a long job. OK, some general questions. For one thing, have you ever thought of changing your research to any field outside of astronomy?

Schmidt:

No. No.

Weart:

Did you ever consider going back to the Netherlands?

Schmidt:

Once or twice, when I was offered jobs over there. But did not give it very lengthy consideration, because somehow I was not inclined to do that. I must be stuck to this place somehow, I guess, especially with this Directorship, of course.

Weart:

Well, now you're certainly stuck for a while. Could you tell me what are the main ways you've spent your time outside of working hours, all through your career? Any interests outside of science?

Schmidt:

Regrettably little . I used to make some music, but I've stopped doing that. I read rather little, unfortunately, I try to play tennis as much as possible, which is a good antidote to sitting at this desk. I watch TV more than I ought to. Well, I like music, and I listen to it, though rarely to a concert.

Weart:

It must be particularly a strain now, because you have to maintain your research, yet in addition you have administrative duties.

Schmidt:

Yes. I was just about to say, what I do at the moment, at home and at night-time, is astronomy.

Weart:

And during the day you're an administrator.

Schmidt:

Right. Yesterday I wrote an article for the IAU symposium. I just turned it in to ????? I hadn't been able to write it up yet during the past three weeks, and yesterday, I managed to do it. It's a terrible way to spend a Sunday.

Weart:

Oh, I don't know. More amusing than many ways, I suppose. In order to get a picture of you all around, would you mind telling me, do you have any religious affiliation now ?

Schmidt:

No.

Weart:

Any strong religious convictions?

Schmidt:

No.

Weart:

Tell me, what do you think about this universe that you've been studying all these years ?

Schmidt:

Now, look here! 'laughter)

Weart:

You've spent a lot of time looking at it, at the prime focus and so on.

Schmidt:

Yes.

Weart:

How does it feel to you?

Schmidt:

Fantastic, of course. People often ask me — which you have been charitable enough not to do today, until you started on religion 'Now, you must have an idea about what a quasar is, ' they say. 'Now you're going to tell it to me.' If I then tell them that I have no particular favorite model or picture of a quasar that I clamp myself onto, they are somewhat surprised . They can't quite imagine it. Yet I f ind it terribly easy. I f ind it possible to work in a field and to have absolutely no idea what I'm talking about. In other words, a true descriptive, pragmatic, being in touch. Quasars — which were so far outside the main stream of things, and are only getting slowly, I think, in the mainstream, mostly because galaxies and galaxy nuclei are sort of going that way now and the quasar are becoming a little bit here and finally the two touch again, —quasars for a long time were these fantastic things, where I thought it made no sense to form and defend a picture about what they really were like. People couldn't quite believe that I could do without it. Perhaps it has something to do with my nature. I'm able to be reasonably happy to work in a field and to really immerse myself in the study of the objects without, to be unkind, a strong prejudice of what they are. I'm sure that some people have said that my prejudices mostly lay in the red shift interpreservation, of course. I think that with religion, it's the same way. I can rind myself - literally, obviously — immersed in the universe, study it, and live in it and suffer in it, and not necessarily have to have an intricate buildup of a guiding force behind it, or whatever. I seem to be able to do without it. Now, perhaps I've just made a description of the true atheist. I don't know. It may be. I don't even know what an atheist is. It may not make sense to talk in those terms.

Weart:

I think you put it very clearly. You try to look and see what you can see that's there, and that's it.

Schmidt:

Yes. And one usually would feel defensive about it, in a sense, but I don't think it's necessarily a lack of imagination. I think religion has an awful lot to do with human psychology. You asked me if I'd ever thought about changing fields. If I had, I think I would have at least in earlier days said that I might have wanted to be a psychologist. Now, at the moment, from what I see or hear, which is very little, I think I have sufficiently little admiration for psychology as it is going an at the moment that I probably would have second thoughts .

Weart:

But perhaps the kind of psychology people used to do, that had to do with, for example, looking at a drawing of Mars and seeing what came out.

Schmidt:

'Laughs) We've gone full circle, I believe. Yes.

Weart:

Well, that was my last question. Is there anything else that we should talk about that occurs to you?

Schmidt:

Since I'm probably saturated and exhausted, it's not surprising if I would not be able to think of anything at the moment.

Weart:

I'm not surprised. We've been going on longer than one usually goes. Shall we stop?

Schmidt:

Yes. Sure.