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Interview of Allan Sandage by Bert Shapiro on 977 February 8, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/32867
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In this interview, Allan Sandage discusses his work with Edwin Hubble. Topics discussed include: California Institute of Technology; astronomy; Carnegie Observatories; photographic photometry; Rudolph Minkowski; variable stars; Cepheids; Mount Wilson Observatory; classification of galaxies; galactic distances; Milton Humason; Walter Baade; Henrietta Swope; red shift; Richard C. Tolman; H. P. Robertson; Grace Hubble; Knut Lundmark.
You want me to reminisce, essentially?
Yes, well, I, starting from the beginning.
OK. Your questions are really, when I first met Hubble, and under what circumstances? As you know, the California Institute of Technology began a course in astronomy in 1948, and I was one of the first graduate students in that course … We students were isolated from Santa Barbara Street for quite a while, and then one day Greenstein came in and said that Hubble at Santa Barbara Street wanted somebody to work for him... and Greenstein said, "Why don't you go up to Santa Barbara Street and talk this over with Hubble?" That was kind of a frightening situation, because Hubble was very well-known, and in coming from Illinois, I had in the back of my mind all I the time wanted to do cosmology or extra-galactic work. I didn't have the courage, I guess, to come up and see him on my own, and when Greenstein said that he had been asked for somebody to come up, I did come up and talk with Hubble. The work that he wanted done was to do detailed measurements of the apparent magnitudes of galaxies on new 48-inch Schmidt plates; … it was a question of the application of techniques of photographic photometry to extend or make more precise the work that he'd done by eye in the middle 1930s on the distribution of galaxies. He outlined this problem and asked if I thought I could do it, and I told him I could, because I had been trained as an undergraduate at Illinois along just those lines of photographic photometry. That was a very lucky break. During the summer I started to do the measurements from the first plates. He more or less left me alone in this; he said, "Here's the plates, here's the standard sequences that have been transferred onto the plates; you see what you can do in deriving the log NCM) curve,” which is the growth curve of galaxies with apparent magnitudes... He left me alone with the problem and went to Colorado. 1 asked Minkowski, who was also on the staff, when Hubble was going to return; Minkowski was in the basement at that moment and he came back and said, "Hubble won't be back for many months — he's just suffered a major heart attack.”The phone call I was informing Minkowski of this. That was a tremendous blow. The question came, what to do? I spent the rest of the summer trying to do the work. He went through a long period of recuperation and didn't see anyone for four or five months or longer. I went down to his house some six or seven months later, and he wondered what the results of the work had been, and we discussed it. I'd stopped because of a systematic error in the magnitudes, a small I error, three-tenths of a magnitude, which wasn't very much, but I thought it was very much at the time. He said, "Why did you stop the work? Three-tenths of a magnitude is nothing, you've got to see the broad picture and you've just got to push ahead and do it." So he was fairly disappointed that the work hadn't continued. But the plate material was not really adequate to get as faint as he wanted anyway. The second year term at Cal Tech had started and there wasn't really much time to work on this. Hubble then came back to the office about a year later — it was probably the end of 1950 that he started working on a restricted schedule after his heart attack. This time he could not observe with the 200-inch; he needed somebody to make the direct plate observations at Palomar, because of his physical condition. A precedent was set by the Director saying, Hubble can't make the observations himself, he has 35 nights scheduled on the telescope, he has organized the whole thrust of the work of the 200-inch — and they hired me as a graduate student to go down and make the observations for Hubble on the mountain. He in fact did not observe with the 200-inch from 1950 to about 1952 because of the first heart attack. He then did go back for a few runs (my memory is not really very good) but he never started a full I-scale observational program again by himself, and by the circumstance of his health, I was his assistant from 1950 to 1953 on the mountain. There were lots of opportunities for contact, because I would go down to the mountain at least three nights every dark run, and during the course of the next few years probably more... Hubble would then take these plates that were brought down from Palomar and he would blink them in the basement. It was not only 2403 but MIOI, M51, M81, all members of the highly resolved system of galaxies, just outside the local group, that he knew about from his surveys with the 100-inch (but the 100-inch just wasn't adequate to get faint enough). So I took the plates, he blinked them and started the catalogs for the variable stars. He brought me into the actual work of the analysis of the plates, fairly detailed and fairly suddenly, so that I knew, for example, that new novae had been found in M81 on the plates taken at the beginning of the run; that would be fed back to what we did in the second and third part of the dark run. During the period of observation I learned a great deal from him, because we'd have conferences every week. Then he began to turn over to me plates that he had not analyzed from the 60-inch and the 100-inch. Among these were plates of M33 and M31. The problem there was that he'd found a class of very bright variable stars, with absolute magnitude at that time thought to be -6 on the old distance scale — the brightest variables that had been known, there was nothing like this known in our galaxy. There were four or five of these in M33 and two of them in M31. He said, "Here's a series of plates on M33 that goes back to 1909 from the 50-inch, taken by a lot of people 11— he took most of them after 1920 when he came on the staff — and of M31, the 100-inch series started in 1920. These variable stars are on them. We don't have any idea of the characteristics of the light curves, or the colors; suppose you see what you can do about working up the photometry.” This meant going to Mt. Wilson and transferring magnitude scales ftom selected areas into the regions of the variables in M33 and M31... So I went to Mt. Wilson, made the observations, analyzed the plates without telling him the results, got the light curves, and did a preliminary analysis of the absolute luminosities. About 1952, a year after these plates had been turned over, all of the material was discussed with him. 1 think it was my training in Illinois and the fact that the old-fashioned techniques of step-scale photometry could be done that lead in 1952 — while he was still I on the staff — to the offer to join the staff before graduating from Cal Tech. He was extraordinarily kind in the training that went on during this three-year period, and brought me as a very young man into the mainstream of what he had started to do on the 200-inch. All the time he outlined the observations to be made with the 200- inch, which continued along with these other smaller projects. As a man he was an extraordinarily impressive individual. It was somewhat hard to get really close, but there was a large difference of age between us... The taking on of students was a new activity for him also; I think he had never done that before. The interaction between us was somewhat formal at the beginning, but his kindliness and patience was a trait that, for a young, quite shy person, was a crucial aspect of our relationship …
Would you describe what he did (in the blinking?)
...You look in an eyepiece that allows you to see... the same star field alternately on one plate and then the other, and any object that varies will I wink out at you; a variable star will I be larger or smaller on a given plate than on the reference plate ...You do this with your whole stack of plates in sequence and mark the candidates for variability on the charts. You often rediscover then, with a blind eye for the past, the real variables. Now, at the plate limit it's extraordinarily difficult to decide what is really a variable and what is a slightly differing image due to grain clumpiness or background effects. So the Cepheids in M31, and M33, which he had discovered with the 100-inch twenty or thirty years before, were very much easier than the plates taken with the 200-inch, where he was trying to go out three magnitudes fainter to bridge the distance gap beyond the local group. This was an order of magnitude more difficult problem. What he did was to maintain catalogs of these four or five galaxies. He wanted to find the variables first, and this was the beginning of a long-term project to determine their apparent magnitudes and their periods… He found 1 think seventeen variables in 2403 and determined preliminary periods from the first three years’ observations.
What were his efforts directed towards?
Baade had questioned the distance scale, the distance to the Andromeda nebula which was the first step in the long chain; the first season with the 200-inch, Baade had made the discovery, much to his surprise, that he was not resolving faint enough in M31 to reach the RR Lyrae stars, which he would have to reach if the distance to M31 is what everyone had believed from 1930 until 1951. So almost with the first plates that were taken, Baade realized something fundamental was wrong. There was a great ferment at the observatories — Hubble didn't like to believe that his distance was wrong, but the evidence seemed to be irrefutable, so he was attempting to go back to his reconnaissance work in the 1930s and build the foundations of the distance scale from scratch again. I think he must have realized — he was 63 at the time — that the work could only be started, that it was a long-range prospect. To find Cepheids beyond the local group itself was a very important first step, but to work them up and analyze them — I think he knew that he couldn't follow that through. There were several aspects to the problem. Whitford and Stebbins had shown five years earlier that the magnitude scales fainter than 16 that everyone had relied on were just wrong. The Mt. Wilson system of magnitudes that was used worldwide in the Mt. Wilson catalog had a scale error which was progressive from 16th fainter, so the fundamental basis of the distance scale had to be restarted from scratch by setting up photoelectric sequences and transferring those in a second step to the fields in question. Hubble and Baade organized this by getting a photometrist on the staff in 1949 and 1950, William Baum. He was to build the first photoelectric photometer at Palomar and build photoelectric photometers for Mt. Wilson. He was to redo the magnitude scale to as faint a limit as it was possible to go in those days, and then those areas where the scale was set up were to be transferred by photographic means to the other systems. Hubble had begun the organization of all of this. I think that he realized that it was laying the groundwork for a real attack, after his very fundamental reconnaissance.
What, were some of his other efforts, or was all of his effort directed toward that?
Much of his effort was directed toward the study of the nearby resolved galaxies. He also had a parallel effort to improve the classification systems of galaxies. The 200-inch offered, for the first time, high resolution direct photographs from which the early questions of the difference between ellipticals and spirals (could be settled), or the family traits amongst the spirals themselves, whether there were multiple arms of a type that could be traced al I the way from the Sa sequence to the Sc's and then into the irregulars. He was still very interested in the reason for the sequence of classification. He was stil1 very cautious that it did not represent evolution, or at least he wasn't claiming any evolution… When he would make up an observing list for a given run, the resolved galaxies were on them, and as time permitted better photographs for the classification problem were gotten. One had an observing list of maybe a hundred objects per run; most of the effort was spent on the Cepheid and nova problem in the nearby M81 group, but there were these peripheral efforts. He was really very much interested in the galaxy problems. Humason was heavily involved in attempting to extend the velocity-distance relation for cosmology, and that was also directed by Hubble; the lists of clusters of galaxies that Humason would attempt to get red shifts for on his run in the dark run were made up by Hubble. And when 1 was his real assistant, in the last year and a half of his life — I was brought onto the staff essentially before I had finished my education and given time of my own on the 200-inch, but this was to work closely with Hubble on determining the apparent magnitudes of the brightest cluster galaxies that Humason was getting red shifts for. When Humason would bring down spectra and measure them and give the results to Hubble, Hubble would make out the observing lists of those clusters where magnitudes had to be determined, again by photographic techniques of building up the squared images in the prime focus of the 200-inch, and by transfers to these areas that had the standard magnitudes determined by Baum photoelectrically. Hubble then continued to extend the magnitudes and the red shifts out to the distance of the Hydra cluster, which was Humason's greatest limit, with a red shift of only two tenths. One says "only" because it's very much more extended, but with the photographic techniques available in the spectrographs, that was an absolutely unique limit, because the sky brightness was already swamping the galaxy spectra. There were no good sky subtraction techniques as are available now with the electronic spectrographs. Humason didn't have those techniques, so it was his skill I that brought out the absorption lines in spectra of the galaxies. Hydra was at that time the most distant galaxy cluster that Humason could get. He tried very hard to get more distant ones. He spent the better part of two dark runs on a cluster whose red shifts we now know is about 120,000 kilometers a second, which is a red shift of about four tenths. And looking back over the old spectrograms where we know where the Hand K lines are, he just couldn't have read that spectrum. I was involved, during Hubble's lifetime, in checking out the candidates for the very distant clusters of galaxies that were being found in great numbers as the sky survey of the 48-inch was progressing. Up to that time almost al I of the clusters of galaxies had been chance discoveries on the edges of small-area plates with the 100-inch on Mt. Wilson and some with the 200-inch. But as soon as the sky survey of the 48-inch went into operation… as the direct plates of that came down to Pasadena, lists were made of candidates for distant clusters. These would be photographed with the 200-inch, brought back to Pasadena, and given to Humason, would measure the blind offsets from those photographs. That is, he couldn't see the galaxies to set on the slit, so with the measurements on the direct photographs taken a month before he could blind offset his guiding eyepiece and get the slit on the galaxies…
Humason didn't extend the Hubble diagram beyond a red shift of two tenths, but he did obtain many red shifts of clusters from 30,000 to 60,000 that fleshed out the whole diagram. Up until this time there were only some ten clusters that defined linearity of the velocity-distance relation. These had been worked up by Hubble, and the last paper on the subject was written in 1936… Although the relation looked extraordinarily good, the generality of the expansion still had to be proved, the isotropy of the expansion over the whole sky... So part of the fleshing-out project was for Humason to get as many clusters as he could, and it was here that the all-sky survey of the 48-inch was crucial. It's interesting to look back before 1948, how really spotty the surveys were upon which these vast conclusions had been reached; I'm amazed at the correctness of those generalities that Hubble made, that the whole effect was universal…
What was the nature of your conversation with him?
They were almost always on technical aspects of the work. He was interested in the nature of the results from the observing runs, and we'd talk about what had to be done next. He'd then tell me, there were three novae found on this series of plates from M81, and we have to continue to monitor those. Because from the normal novae one can also get an estimate of the distances. So the progress reports and what had to be done next were involved. He talked a little bit about the cosmological aspects. There was a ferment here. The group consisted of Hubble and Humason at the nucleus, and Minkowski to some extent, although he was not so directly involved, and Baum and myself attempting to get magnitudes. We all knew what had to be done in the next weeks to prepare the others for what they had to do in their aspect of the work, and there was a fairly strong conversational aspect, and discussions week by week. I was still a graduate student during a lot of this, so it was not a day by day activity in the office, but I'd come up once a week, and at the end of every run bring all the plates up and we'd discuss the plates. There was very little discussion of the theory, there was very little discussion of the philosophical aspects — that was taken for granted; it was taken that we all knew why we were doing it and we all knew that the curvature of space was the goal — the nature of the universe, the large-scale structure of the universe, were the reasons for doing it, and were just taken for granted. There was not much teaching involved, no tutorials; it was a research activity and everyone knew what they had to do. He was a formal man. I think I was frightened in the presence of Hubble, who clearly had a reputation at that time. It was the culmination of an ambition that I'd had since I was ten or eleven years old to be in this place, and just to be in the temple of Santa Barbara Street was the most frightening experience that could be imagined for a young person. Just to take a 100-inch plate and have it in your hands was like touching the most precious thing that you could conceive of in the world. It was an experience that can't be described in ordinary terms. It's hard now for me to really remember anything but the awe and the tremendous feeling of extreme opportunity that had been placed in my path, and whether I could rise to the occasion or not. Every day, I think, was a testing period, and to be accepted by the group was in the forefront of the mind almost continuously. It took fifteen years, I think, to overcome that. I don't have that awe coming into the office now in the same way. I think the universe is frightening in that way that Hubble as a person was frightening in the early days. But it's hard now to recall, except to know that it was an experience and a half.
Did he ever indicate anything about his feeling about the interpretations of red shifts?
No. I have gathered all I know about his deep philosophical feelings from his writings. It was almost always on a technical level that we talked. He was of a poetic nature, he was an intellectual of a most profound type, but he didn't really open up in these ways, in philosophical discussions, at least with me. And he was first and foremost a scientist; and his philosophical leanings clearly came out in his writings, but he stood for no softness in the science. There was a way for proof, and one had better not make any mistakes. I remember the first paper I wrote, the results of these bright variables in M31 and M33. He said, IIGC "write the first draft of this,” and that was a training and a testing. It was awful — I mean the writing style and the putting together of the thoughts in some coherent English. He was a very good writer. He read it, and he didn't talk very much about it but he clearly indicated that I'd better learn to write and there were techniques to be overcome. In the gentlest of ways and the most sparse of criticism he let it be known that he expected more. I remember I thought that I cannot let this man's opinion of me be anything but the very best, and therefore I really have to try extraordinarily hard. But he was gentle, he was not a tyrant. His closest associate at the Observatory was of course, Humason, and even Humason after 30 years said that very seldom did he and Hubble have personal conversations. He kept himself somewhat aloof from the staff. I don't think that was purposeful; I think he was just in tune with this magnificent project that he'd had since 1920. He saw the vision, and he was more attuned to the office as a place to get things done than as a place to socialize with col leagues. He was professional in almost every contact that he had, at least with other astronomers. Now, he moved in intellectual circles in Southern California at the time, and as you know amongst his friends were Stravinsky and Huxley; Huxley and his wife were very good personal friends of Hubble's while he was alive, and Mrs. Hubble and Aldous Huxley and Gerald Herd remained close friends until Huxley died.
Did he ever disagree with you? Did he ever discuss his long-term observational program what he would like to do beyond what you were doing?
No, he never did. It seemed so clear-cut what had to be done, to go beyond the 100-inch, use the power of the 200-inch, which was so profound. It was such a big step forward and it opened up so many things that it was just like children in a candy store, I'm sure, to al I the astronomers involved. There were only some twelve astronomers that could use the 200-inch, and they had been planning in their own minds what they were going to do for years. Baade had planned to re-do Hubble's work in extraordinary detail in M31 for the Cepheids, and that's work that took Baade and Henrietta Swope some ten or twelve years after the beginning of the work, in 1949, to complete. It was all laid out what had to be done. The red shift was crucial; that was the most profound of the discoveries in the 1930's and that had to be extended. So Humason was giving an enormous amount of time to pursue the red shift studies, parallel with that had to be the determination of the apparent magnitudes, and Hubble would get those determined in any way that he possibly could. He didn't really speculate very much on the interpretation-what it meant. I never heard him really talk about the curvature of the universe or experimental geometry, doing was Gauss had done. There was very little of that in his writings. There was a strong philosophical trend to the writings, that here we have a reasonable sample of the universe for the first time, that it's important to find the deceleration, but he never made that next statement: Once we have the deceleration, we will be able to determine the following. He was primarily and principally an observer... Hubble was extremely interested in finding out the nature of the red shift, but he did not in fact mount crucial experiments for that — I think it was first of al I too difficult at the time. He mounted for the first time the experimental test to determine the intrinsic geometry by counts, but I don't think he really believed the answer, up until 1938 when the analysis was done. He realized that he was really overstepping what the data could be made to prove. It looked like a very complicated problem at the time. He used the equations of the change of volume with distance that Tolman had invented starting in 1929. The coupling between Tolman and Hubble must have been very good, because Tolman supported Hubble in many of his activities. Yet Hubble did not make the connection between the deceleration and the intrinsic geometry explicitly in any of his writings; all of that can't be about by a fusion with H.P. Robertson, who was also a supporter or Hubble's and took Tolman's place on the Cal Tech campus. Robertson and Hubble were very good friends, they had a lot of interaction, but they were of a different generation, they were fifteen years different in age, and approached the problem slightly differently. The fundamental paper by Robertson in the PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, which was given in 1954 or 1955, he dedicated to the memory of Hubble. There explicitly he begins to made the modern correspondences between what can be measured and what it means in terms of Einstein's coupling of geometry and dynamics. Hubble, I think, characterized himself as a pure observer. There were press conferences, for example, when Humason would get a large red shift. Both Humason and Hubble would go to the press conference, and the reporters would ask, "So what? There's a large red shift, 60,000 kilometers per seconds for Hydra, what does that mean, what can you do with it?" And at least in the later years, there was always a modest statement; that it was still a reconnaissance, we're still trying to see whether the law of red shifts extends further out. He would never say, "If we can determine whether the universe is slowing down, or not slowing down, then we can determine in fact, for the first time experimentally, the curvature of space." That's a public relations type statement. He was a cautious man, and whether he really thought in those terms or not is not really understood by me. We never really did talk about cosmological models... The disruption from 1938 waiting for the 200-inch to be completed, then going into war work and coming back in 1946, and then with the 200- inch operable in 1949 and the more immediate questions that Baade raised about the distance scale, may have caused him in his mind to think, "Okay, we have to get this problem solved and then cosmology will fallout." He was more a practical man than theoretician.
Did he ever talk about the 200-inch and the relative success of it, or the lack of success of it?
He had such a short opportunity to use it. After his heart attack he did not observe for about a year and [a] half with it, and he was just crestfallen. He then did go down and begin to use it again in the last year of his life. They mounted bells up in the prime focus cage so if another heart attack were to come he could signal down, and they mounted a special alarm system in his room in the monastery. His wife was very concerned about his observing, but this is what he had to do. It was at this juncture that it was quite clear that he needed somebody to take just the physical load off him in observing, and it was through this opportunity that I did come.
Did his doctors instruct him to discontinue observing?
I don't really know. He did not lead a sedentary life. He walked still from his office down past the Huntington [Library] to his house every day, and that's a distance of about three miles. On the day he died, I had seen him either that morning or the morning before — my office at that time was on Santa Barbara Street; I still hadn't gotten my degree but I was not in residence on the campus. So we talked, and I can't really remember what we talked about. He customarily left at 11:30 and would stride out with his walking cane, down Santa Barbara Street and down Lake Avenue. It took him about 45 minutes to make the walk, maybe 50 — and he got home and his wife was there, outside, and he collapsed on the lawn of his house.
A cerebral hemorrhage, I think, was the final cause of death, a massive, instantaneous attack on his lawn before he got into the house — at least, that's the understanding. Mrs. Hubble called Humason and Humason went down and helped her. She, of course was extraordinarily upset. All the time that I talked with Humason he did not know where he was buried. There's no knowledge of the local people, at least, where he's buried... The funeral arrangements were private and I think no one went to the funeral. There's a mystery about that, at least in my mind. She then took upon herself to collect all his papers and organize them for the Huntington Library… She was always close to his career, and understood what it was he'd done — his greatness as an astronomer. And he shared intellectual pursuits with her. They were really and truly intellectuals, they would read Gibbon all the time, they would read Shakespeare, they would talk continuously about music, art, literature, plays… All the time that I knew them, they were formal with each other in some noble way. I can't describe it, that was just his nature, even at home. I did get to know them socially quite well during this period of the last year or so... I got to know her quite well also. She's a very marvelous woman, and after he died she and I talked about many things. I, as a very young person, learned about these other aspects of life, of learning and achievement, from her.
Did you learn anything about Hubble from Humason? Did Humason talk to you about Hubble?
Yes, he did. What did he say about Hubble?
Humason and I became very good friends, both before Hubble died and after Hubble died. Humason was Hubble's confidant. He was essentially the only person that Hubble ever talked with, and only occasionally would he become less than formal or less than astronomically professional with Humason. There were times that Humason would explain Hubble to the staff here, because of his aloofness. I think that it was just in his nature, I really don't think that it was any attempt to be better than anyone. Humason did say that Hubble occasionally was upset that he could not communicate more personally with the other members of the staff… Minowksi was also a good friend of Hubble's. Baade and Hubble had a good working relation, but I think that they were scientific rivals. Hubble was very proud of Baade — proud is not the word, he was quite supportive of Baade, and thought that he did magnificent work of a detailed nature, that there was no sloppiness at all. Yet Baade being interested in galaxies, clearly there was some rivalry, and there was no collaboration. Baade also was upset that the whole of the thrust of the dark time use of the 100-inch from 1930 to 1940 was for the red shift problem and not for the detailed analysis of the stellar content of the galaxies. Baade had the idea that from the study of the stellar content of galaxies you could solve the cosmological problem through the back door, and he said that publicly. In fact, now with the coalescence of Hubble's program with the knowledge of stellar evolution, which was built essentially on the populations differences that Baade had enumerated in 1940, those two streams are coming together in that way. But I'm sure that it took both approaches, and it was just extraordinarily lucky that both types of people — the Baades and the Hubbles — were here at that crucial time with the large instrumentation, to both be allowed to pursue their individual aspects of essentially what is now the same problem. It looked in the 1930s and the 1940s that it was not the same problem; the stellar content of galaxies didn't look to have very much to do with cosmology per sea But now the understanding of the early history of the collapse phase of galaxies and the formation of stars and the whole chemical evolution from the halo to the disk, the whole explanation of the Hubble sequence in terms of initial conditions of formation, is more along Baade's line of thinking than Hubble's completely phenomological approach. Hubble really was not a theoretician, he was a practical observer who understood the significance of what he was doing in a qualitative way; he was the greatest qualitative astronomer of the last 400 years because he did make the correct qualitative judgments. He himself was not so proud of the numbers, his distance scale, the value of the Hubble constant of 350 kilometers a second per million parsecs... Hubble would be less crushed by a change in the quantitative aspects of his picture than would Baade. Baade would be very upset, I'm sure, if his magnitude scale were wrong in M31. That's just the difference of the German way and the Hubble way — I was going to say the English way — Hubble was an Anglophile, and he had a lot of the nobility of the English.
A difference in personality, wasn't it?
Yes, it certainly was a difference of personality. Hubble's numbers were not as important to him as his ideas. The crucial test of a qualitative nature for the nature of the expansion would have fascinated him, whether the surface brightness does decrease or not. I think he was after the basic physics, but from a phenomenological point of view — he had a great deal of Bacon in him, the Baconian approach instead of the approach of Kant or Goethe or somebody like that. That's not a good analogy. He was more for the broad picture than for the small details. And that's the reason that I think he probably looked with unhappiness on the prospect of having to go back and start to do it all over again, and that's what the 200-inch permitted one to do, to go back and do the numbers right. And al I we've really done in the last 30 years is to go back and try to do the numbers right. And that would have not interested him. However, I'm not being fair either to him or to the present situation. The crucial aspect of getting the numbers right is to make the correspondence between the time scales which can now be brought into play, namely the ages of the stars and the age of the galaxy when it collapsed during the col lapse phase (and you can only determine that by age-dating the oldest stars, as in globular clusters). That al I came essentially after Hubble's time. It's the correspondence of that age with the Hubble constant which gives the expansion age of the universe, and you have to have the numbers right for those correspondences to come out right. He would have been interested in the qualitative comparisons of that — and the radioactive clocks, that is, the age of the chemical elements.
Did he ever talk about things that annoyed him or upset Never. You never heard things about people? No, he never talked about his col leagues at all. Or on the world at large?
He was above all that. Yes, he was very upset about politics, he was very upset about Harry Truman, extraordinarily upset. I was in his office one day — I remember this so well, because it was so unlike him — we had been talking for an hour about some technical aspects of what we had to do next, or what he wanted to do at the telescope. There was a knock on the door — the door was closed — and two men, I think in Navy uniform, came in and said, “Oh we’re sorry to disturb you. Hubble looked at them and smiled and said “Do come in. We were doing nothing but complaining about that terrible man in the White House.” (laughs) And there was nothing, absolutely nothing, in the conversation before that that had the faintest hint of politics. To this day, I don't know why he said that. Maybe it wasn’t the "man in the White House”I but it was some complaint about a national figure who I think was the president…
He didn't ever express anything like that before, you can't think of any reason...?
I guess I knew that he clearly was a strong conservative.
A republican? Yes, and he was an extraordinary patriot in the old school. I suppose my belief in that comes from different sources; one, talking with him, and secondly, reading some of the things he wrote, the American Legion speech that he gave about the nature of one's duty to one's country. And just his whole aura—I'm sure we must have discussed things besides science. But we never discussed philosophy per se, we never discussed the purpose or meaning of life. To young people some of those questions are so crucially important that they feel if they could talk to somebody that would have the answers, they'd do it — well, I never felt I could talk to him about some of those deep questions that all people have. I know the problems were crucial for me at the time, but I never talked to him about it. I just never would have thought of talking to him about it. I don't know why that is, whether he was always so formally scientific with me, or just what it was. It was the formal conversation of a diplomat, is the only way I can put it — there was no easiness to it; he was warm, but there was always a wall. There was a great age difference. We liked each other I'm sure, and there was no friction at al I, but there was a day-by-day formality. And that was the old school, that must have been the way that things were run before the turn of the century, for example. It was just more formal than, for example, the students at Cal Tech at this time. It was a different period. There are a couple of questions here... the fact that he did his own work, was that indicative of anything? No, almost everybody did their own work. It wasn't an Eastern tradition, was it?
No. (laughter) I don't know who's going to listen to this tape, but in any case let me tell you the difference between East coast and West coast astronomy. That tradition still goes on, that almost all the staff members here at the Observatory did their own work. That isn't to say that there was not a staff of computers. But what they did was to take the spectrograms after the astronomer measured them and just do the reductions. The reductions were done in parallel, two people did them independently. But the fundamental work of measuring the plats for proper motion that Van Maanen did, the measuring of the plates for positions that Nicholson did to get the first orbit of Pluto, all of the measurements of the Cepheids, that was done by the staff astronomer. Baade blinked al I of his plates, he had no one to blink the plates. Henrietta Swope didn't blink the plates. After the variables had been found and the magnitudes transferred by step-scale photometry to standards, she then got the light curves. She was not in the ordinary, normal sense an assistant, she was a highly trained astronomer, and so it was a collaborative effort with another astronomer. But it's so rare, or was rare, that any staff member had anybody else do the work of getting the data off the plates. The micro-photometry was done by the spectroscopists, for example, for equivalent widths, by themselves. They ran the plates through the machines. It's a closeness to the work, total immersion in the problem. The people at Lick do the same thing, and now people at Kitt Peak essentially do the same thing. I think that the tradition of having lots of people get the material off the plates has really disappeared, even in the East.
There are just a couple of random questions, if you don’t mind.
No, not at all.
In finding the Cepheids in M31, why do you think it was Hubble who found those as opposed to anybody else?
He had the 100-inch. Now, there have been statements made by young historians that the thing could have been done with a 30-inch.
Yes, I’ve read those.
That’s absolutely incorrect. Anyone who would look at plates taken with the 60-inch, even, on Mt. Wilson, if they were to try to blink those plated to find the Cepheids, they’d fail. It’s one thing to sit down and ask what the limiting magnitudes; it’s a very subtle discovery. Attempting to find Cepheids by blinking the original plates is an interesting exercise — it’s hard. Hubble was a really good practical person; he was a good observer. In that sense of knowing what to look for and with tenacity pulling things out of the plates, he was unsurpassed…
Did Hubble ever talk to you about his moments of discovery or what it was like to do that?
What did he show the most enthusiasm about — when did he seem to have the most JOY?
You see, he was quietly enthusiastic. It would have been out of character for him to jump up and down and say, “Hey, look here, we’ve got three Cepheids last month — terrific!" I’ve asked myself exactly the same question, and I just can't remember. Whereas with Baade, you can remember that he was bubbling over continuously, just a boiling cauldron. He'd tell jokes; he'd always have interesting comments. Hubble was more businesslike with me, and I can't really remember those aspects of his personality. Humason tells a very interesting story. Mt. Wilson is very formal, there's a linen tablecloth on the monastery table — it's nice, I think it's a bit of civilization in the wilderness. And everyone that's on the staff sits at a particular assigned place-the 100-inch observers sit at the head of the table, the 50-inch observers sit to his right, and so forth, and that tradition is still maintained. Wei I, when Hubble went to observe on the mountain he wanted to make sure that the evening conversation was of the right kind. So the story goes that he would go down to the monastery about four o'clock in the afternoon, look up a subject in the ENCYCLOPEDIA BRITANICA, the 11th edition which is up there (that's the best edition, there's all kinds of neat literary things in the 11th edition) and he'd bone up on it. Then at dinner he would call on somebody to discourse on the subject, and of course it was out of the blue. So he'd come in — just like high table at Cambridge or Oxford college, you know, where your survival depends upon your wit, your digestion depends upon whether you can one-up the next guy over. He had a bit of that about him, and it can only be trying to bring in the high table atmosphere. That's the story Humason tells. I never saw any of that.
Did Humason ever tell you about any failures or anything that Hubble regarded as a failure?
(laughter) I don't think Hubble failed in anything. The idea has never crossed my mind. No, he never told me about any failures, nor did Hubble.
There was no thought about that?
No, Hubble never seemed to have to struggle. I can't explain it — he did work terribly hard, and he did tell me that the way to success is to do a project and then throw all the material away and do it away, because now you know how to do it. His projects were always long-term, there was never any short-term aspect, never anyone or two night stand operations that could be made into a little note. If you look at the character of his work it was always general. It was, for example, proving that the nebulosities were reflection nebulae in our galaxy. Not writing a paper on a single one but waiting until he had amassed 50 or 70 of them and found the exciting star. Every paper he wrote was a classic. This reflection nebulosity one in 1922, for example, is still quoted. It was the definitive paper on the mechanism, which is reflection from a bright star, and he showed that any star cooler than a 83 star did not have enough ultraviolet flux to excite the gases that were present to fluoresce, but rather the dust in the nebulosity reflected. Most people nowadays, and a lot of people in those days, would find an example or two and write a paper, but he waited until he had it done. His insight into the problems that he should tackle was infallible. I don't know of any major project where his insight wasn't correct and that he didn't finish. He left virtually no unpublished material. They were always enveloping investigations. If a young person wants really to study how to choose one's research problems, some sort of a definitive study of Hubble's published works from a psychological standpoint would be very rewarding. It was the Mt. Wilson tradition, and Baade had it also. Adams had it, the whole of the details of the Hertzsprung-Russell diagram. No one understood stellar evolution from the time Russell in 1912 first made the diagram until very late in the game 40 years later... And the long-range problems of the Mt. Wilson Observatory were crucial to that, that is, the spectroscopic parallaxes which were discovered by Adams and Colshuder here…
Did he talk about people that he particularly liked, or whose work he admired?
To me he talked very little about personalities at all. He knew Eddington quite well, they were good personal friends. But I cannot remember him really talking about people. In later years, it's normal to bring personalities always into talk about some work, but whether he did or not with me, I don't know. I can remember Baade talking about personalities, Minkowski talking about personalities, and Humason, but it was a subject that either didn't interest Hubble, because he was interested only in the science, or it interested him so much that he daren't talk about it, at least to me, who was very junior… The only person that I know that came to the office was Lundmark. That is a story, because Lundmark and Hubble were great rivals. And Hubble in his early days apparently was not as generous as his rivals thought he should be about certain aspects, such as the (galaxy) classification scheme which people had been working on. There were papers published by Lundmark on the classification, there were papers published on the kinematics of the nearby galaxies from Slipher's velocities. Lundmark wrote three fundamental papers in the MONTHLY NOTICES. They turned out to be wrong. He put a power series through the data with a second term, which had K times LR times MR2, and he evaluated those. The sign of the coefficient of the R2 term turned out to be negative, which means a parabola, which means that after a certain distance the velocity should go down to zero. So Lundmark said in 1925 that it's clear that one can expect no velocities higher than 6,000 kilometers a second, and we don't understand the reason for the strange kinematics of the local system. So Lundmark was studying that problem, Lundmark had the distances to the galaxies, he had the classification, and Hubble was thought to be less than generous in his written statements, especially in the classification paper of 1926 in the ASTROPHYSICAL JOURNAL. There was an IAU meeting in 1922 or about that time, and Lundmark went and presented his classification system. Hubble had sent a classification system by mail to the RAU, and it was read. Then Hubble claimed that Lundmark had stolen his system. Lundmark hadn't; if you read it very carefully, it's a different system almost completely, and there's a footnote paragraph in a paper by Lundmark called "Studies in Anagalactic Nebulae" in 1'325, which describes this whole episode of the comment of plagiarism, the actual physical meeting of Lundmark with Hubble, and a refutation and a final sentence which really has to be read to indicate the strength of the feeling between Lundmark and Hubble. This had been well after. Then after the 200-inch was in operation, about 1951, Hubble invited Lundmark to come and make all the use he wanted to of the 200-inch plates; he would turn over all the 200-inch plates that had been obtained for classification purposes, that weren't being used immediately for the Cepheid problem. Lundmark had an office, it was the office right next to this one, for about six months. Everyone was tremendously surprised at that. I don't know what the interaction between them was; this was when I was still down on the campus; but it must have been good, because at Lundmark's death, about half of his estate was put into a trust fund for students to work at Santa Barbara Street. With that whole history of tremendous rivalry. Lundmark had cosmology in his hands, but he didn't have the overall integrative ability to make the world picture; out of the same pieces Hubble had. Hubble had a few more with his observations. But essentially other people had gotten the observations for Hubble in the expansion, I mean Slipher and then Humason, and didn't make the correct inferences. Hubble's tremendous ability was to make the correct inferences out of the minimum amount of the information. He had a feeling of what was right, what was beautiful, the same way Einstein did…
There’s just one other thing I want to ask you, and that’s about Humason himself. What was Humason’s understanding of cosmology per se, oh, he certainly understood what everybody understands now, that the galaxies, that a fair sample of the universe is there, but that’s the same way that all the liberal arts students knew. He had a general knowledge, clearly, but as a theoretical cosmologist, or a practical cosmologist designing programs as to what to do next in order to map the geometry of space, he wouldn’t do it. He was involved in many projects at the observatory. He was also one of the ones that did vast spectroscopic parallaxes of the Coue plates on Mt. Wilson, and Humason was a strong part of that 4,653 star catalog. He made the observations and also made the reductions. He was in every sense of the word an observational astronomer. He didn’t have to be told what to do, for example, to design programs in spectral classification in select areas. He was nominated for the gold medal of the Royal Astronomical Society (this was after Hubble died) and there were certain requests for recommendations amongst other astronomers, primarily on the staff here, and they turned him down. I think that’s wrong. His international reputation was stronger than the reputation of the astronomers that had required formal education. He was a great man in his own right.