Background radiation

Dave Wilkinson's leadership in the exploration of the CMBR, through his own research and the education of other key players, continued from the identification of this radiation to his central role in a last great experiment, the Wilkinson Microwave Anisotropy Probe.9

9 David Wilkinson was one of the group who planned this book. He did not live to write a contribution (d. September 5, 2002), but Dave's voice comes through in this transcript of an interview conducted by Michael D. Lemonick on July 25, 2002, and recorded by The Educational Technologies Center, Princeton University. The comments we added are in square parentheses and footnotes.

DW: My name is David Wilkinson. I'm a professor in the Physics Department at Princeton. I work in cosmology and astrophysics; I do experiments. I came to Princeton in 1963, was lucky enough to find a hot research topic and rode that to tenure, so I've been here ever since.

Q: What do you think led to your being a scientist, and in particular a physicist?

DW: I became a physicist because of a course in engineering I took in college, called "Cement." And I couldn't imagine taking a whole course in cement.10 I enjoyed my freshman physics course, so I decided I would become a physicist and not a cement engineer. That really was the reason. Plus I really liked physics.

Q: Where did you go to college?

DW: The University of Michigan. I went to school at the University of Michigan.

Q: And where did you grow up?

DW: I grew up about 30 miles west of Ann Arbor in a little town called Michigan Center.

Q: Were either of your parents scientists?

DW: No. My father didn't graduate from high school. My mother worked her way through teachers college at Kalamazoo and ended up teaching math. So I think I got some of her genes for the math and science side. But I got the practical genes from my dad; that's why I'm an experimentalist. He could build anything and fix anything.

Q: So you majored in physics in Ann Arbor. Was there any particular area of physics that you specialized in?

DW: No, not as an undergraduate. As a graduate student, first of all I got a degree in nuclear engineering because that was the hot topic at the time and one could walk out with a Masters and get a fantastic salary of $10,000 a year. But I soon decided I didn't want to build reactors and I went into more of a particle physics mode. I did my PhD measuring how strong a magnet the electron is. It had little to do with cosmology but it was a lot of fun. And I had a great thesis advisor [Dick Crane].

Q: How did you come to Princeton?

10 On other occasions Dave mentioned steam tables.

DW: Fortunately my PhD thesis turned out to be pretty important. Bob Dicke here at Princeton, people at Columbia, Harvard, and Yale, had all tried to do this experiment, and Dick Crane and I did it better. So the old boys network went to work and I got my choice of where I wanted to go. Things were a lot different in those days. And I decided I wanted to come here and work with Bob Dicke on gravitation.

Q: In what sense did you work on gravitation?

DW: When I first got to Princeton I worked on gravitation with Bob Dicke. He was doing ground-based experiments and had just started working on the [shape of the] Sun, and I was intrigued by that project. In the end, I didn't work on it but I realized that I had a real fundamental interest in astronomy. Then Bob suggested a project which involved building a small radio telescope and that just completely clicked with what I wanted to do.

Q: What were you going to do with this radio telescope?

DW: [About the time I came to Princeton] Bob Dicke independently had dreamed up the idea of a microwave background left over from a hot phase earlier in the universe. Not only had he gotten the idea that the universe was filled with this thermal radiation, perhaps, but he had invented in 1946 the instrument to [find it - the] so-called Dicke radiometer, which is famous in radio astronomy circles. So he sort of drew a picture on the blackboard and said, OK boys, go build this. So Peter Roll and I went off to build this little radio telescope that ended up on the top of Guyot Hall [pictured on pp. 214 and 223] on one of those turrets of the building.

Q: Did you at that time have any preference for any particular model in cosmology? Did you like the idea of a big bang?

DW: Cosmology was just completely in its infancy when I came to Princeton. There was still a huge debate going on whether it was big bang or a steady state universe. The steady state universe always looks like it does now, in the past and in the future. You have to play a few tricks with physics to do that, but philosophically it's very satisfying to think the universe will always look like this. And of course there was the big bang theory named by [Fred] Hoyle as a joke. It said that the universe started in a very hot condensed state and then expanded out and its still expanding. So the theories were so crude at that point. There was no data except that the universe was expanding. It was very hard to have any kind of an objective opinion. Of course if Dicke's idea worked out - incidentally this was an idea that had been well published by George Gamow and his colleagues twelve years earlier, but we did not know about it - if that idea worked out, that was very strong evidence for a big bang. There was no way that this heat radiation could be naturally produced in the steady state.

Q: So you went out to build this radio telescope. How was Jim Peebles involved in this project?

DW: We formed a little group based on Dicke's idea to explore it. Jim did the theory behind it. If there was a big bang would this radiation still look like heat radiation? Would it have the spectrum (the intensity versus wavelength) that one expects from heat radiation? Or would that have gotten distorted somehow between the big bang and now? That was the key calculation that had to be done. He also did a calculation on making elements in an early universe which also, unbeknown to us, had been done by Gamow's group. So Jim did the theory, Peter Roll and I built the instrument, and Bob was the great advisor.

Q: Even though you didn't have a personal opinion about which cosmological model was correct, did you have any sense that if you found this radiation it would be a very big deal?

DW: Yes. If we found this radiation it was certainly going to be a big deal because it would resolve this basic argument about big bang and steady state. Plus it would give us a tool for examining the physics in the very early universe before any stars or galaxies formed. And that was unprecedented: to be able to measure a probe that came right out of the big bang. There was a lot of anticipation. There wasn't a whole lot of hope.

Q: Why wasn't there hope?

DW: The idea that we might actually find this radiation seemed kind of remote to us. First of all, there was no other data to indicate that we were living in a big bang universe. It seemed rather fantastic that this remnant would be around and nobody would have discovered it before. It's not a weak phenomenon. But it turns out, the way radio astronomers do their work, they have much better sensitivity than they need but they can't detect this radiation because it's coming equally from all directions - almost. [Radio astronomers subtract the radiation received when the antenna beam is on an object from the radiation received when the beam is on apparently blank adjacent sky. The subtraction eliminates unwanted radiation originating in the instrument and atmosphere, but it also eliminates an isotropic sea of radiation.] So the more we thought about it and read papers in radio astronomy, the more we realized that, yes, this thing could be out there and nobody would have seen it. You need a very special type of radio telescope to do it.

Q: Tell us the story, the now famous story, of the day you were sitting in Bob Dicke's office having lunch and the phone rang.

DW: The group that was looking for this microwave background, which is what we call it, consisted of four people, Bob Dicke, the leader; Peter Roll and I, the experimentalists; and Jim Peebles, the theorist. Every Tuesday at lunch we would meet in Bob's office and discuss the progress and problems and so forth and try to figure out what we needed to do to get there. There were some very specialized pieces of equipment we had to build, and it wasn't obvious how to do these things. Well, one Tuesday we were sitting there and the phone rang. (That often happened; Dicke was a famous guy so people called him all the time.) He picked up the phone and we went on with our conversation as usual, and then we heard him say "horn antenna." Well, that was one of the very special things you needed to do this experiment. And then he said, "cold load" - cryogenic load - and that was the other thing you needed to do this experiment. So now we were pretty tuned in because at this stage we were about halfway through building the apparatus [with a horn and cold load]. We hadn't gotten it on the roof to observe yet. So we listened to the rest of the conversation, which didn't go on more than 5 minutes, and Dicke hung up the phone and he said - I'll never forget his words - "Well boys we've been scooped." He immediately, in 5 minutes' discussion with Arno Penzias, realized that they [Arno Penzias and Bob Wilson] had been looking at this microwave background, this heat from the big bang, for a year trying to figure what was wrong with their instrument. And to their great credit Arno Penzias and Bob Wilson stuck to it. Often experimentalists will sort of write [things like] that off and say, OK, well here's a little effect that I don't want to deal with, there's probably no important science in here, it's just some quirk in my apparatus. And they overlook it and go on and do their measurements. Well Penzias and Wilson didn't do that. They stuck in there; improved their measurements. That's why Dicke was convinced so quickly, because they had their ducks lined up. They could answer all of our questions. So we went up and visited [Bell Labs] about a week later, looked at their data, looked at their apparatus, and it was obvious that they were seeing what we were looking for.

Q: When you found out that you had been scooped, did you stop working on your experiment?

DW: Oh no! Just because they had found the radiation we didn't stop. In fact we sped up because our apparatus was designed to measure a different wavelength than Penzias and Wilson had used. And this was the crucial test of the idea. No one would believe that what they were seeing was heat from the big bang without measuring this spectrum that I talked about, intensity versus wavelength. [Thermal radiation] has a very special shape. So we charged ahead in order to try and verify this spectrum at a different wavelength than they had. The discovery papers [on the Bell Labs detection and the Princeton interpretation were submitted] on my birthday in May and our [measurement] paper [was submitted the following January]. So we were about six months behind them.

Q: What was the reaction of the astronomical community to these papers? Was the big bang accepted pretty much immediately?

DW: The astronomers did not like it much, and the physicists didn't like it much - for completely different reasons. The physicists didn't understand any cosmology at that time. It's completely different now; a lot of physicists work in cosmology. At that time, Dicke's group and a few others were the only ones working in cosmology. So there was no way that they could evaluate the science. And certainly with one measurement at one wavelength everybody was skeptical, including us. We stuck our necks out and published [a paper (Dicke et al. 1965) interpreting the Penzias and Wilson (1965a) result] saying we think this is heat from the big bang. That was pretty roundly laughed at. Even after we got our data point I got a lot of questions at meetings and got grilled. But gradually people started accepting it. These big paradigm shifts in science are always hard to swallow because, whether you like it or not, you're in one camp or another. Certainly the steady staters did not like this at all. The big bangers had a little trouble with it, because why did it take till 1964 to discover this stuff? Radio astronomy had been around for 15 years. So there was a lot of sort of detailed knowledge that needed to be accumulated before you really realized that these measurements probably indicated discovery of heat from the big bang.

Q: Once the idea of the big bang started to be accepted and people really did accept that this was radiation left over from the fireball, what did you decide to do next? Did you have any thought of leaving cosmology and doing some other experiments?

DW: As the idea was gradually accepted that this radiation really was from the big bang, more and more people started coming into the field and making measurements, of all different sorts. All of which agreed with predictions of the big bang theory. I saw this as a wonderful opportunity to do some groundbreaking research, because here was a brand new phenomenon coming from the very early universe, something we never had before - not even come close to it. This radiation dates from when the universe was only about 300,000 years old, and that's in a 14 billion year old universe. So this stuff came right from the beginning and it looked like we probably had an opportunity to do some really fundamental measurements of the early universe. I would have been crazy to get out of the field at that point. There were just too many opportunities.

Q: What was your next series of experiments? What did you decide to do next?

DW: The next thing we did, after the initial verification that the spectrum looked OK, was to ask ourselves, is this stuff really coming from everywhere in the universe? That was a crucial test. If this was some kind of new radiation from our own galaxy then it would be concentrated in the Milky Way. If it was truly a universal phenomenon, then it should be coming the same from all directions. Bruce Partridge, who was here at the time, and I modified the original apparatus [that had been used to measure the intensity] to scan the sky and look for little wiggles [in the intensity]. This is the so-called anisotropy in the radiation, which is a big industry these days. Well, we didn't have very much sensitivity. Radiometers these days are a million times more sensitive than the thing we had. We set this thing up on top of Guyot - again. Part of the experiment was to try and switch the beam a lot. So we had a big reflector that would come up in front of the antenna and deflect the beam up to [the North Pole, and then the reflector] would go down, the beam would go off to the equatorial plane. Well, we didn't quite apply enough oil to this thing so it started squeaking and the undergraduates were really annoyed by this thing because it went on all the time so it was squeaking away at night. So somehow those guys scaled the wall of Guyot and went up there and dismantled our reflector. This is one of those funny stories about Princeton undergraduates and what they'll do to do something different. Anyway that experiment went on for a year. All the data came off on chart recorders with pen and ink. Bruce and I would come in every day and spend about two hours reading those charts by eye, writing down long columns of numbers because at this point computers weren't around. There was no way to record the results digitally. And after a year we concluded that yes, this radiation was very [close to] isotropic, better than a tenth of a percent. And again it fit the prediction of the big bang theory. That was really a part-time thing, to carry us over to when we could build new technology. Meantime, while we were taking this anisotropy data, we were building much more sensitive receivers.

Q: When did you start using the more sensitive receivers?

DW: We started using the more sensitive receivers in the late 1960s, early 1970s; took them to mountaintops because water vapor in the atmosphere bothered us so we wanted to minimize the amount of water overhead. Mountaintops seemed like a good idea. Turned out it wasn't because of all the turbulence going over the top of the mountains. So the next thing we did was put our radiometers in scientific balloons and fly them from Texas. I had a wonderful graduate student named Paul Henry (who's very active in the [Princeton University] graduate alumni association). He built a radiometer with my help, trotted off to Texas, attached this thing to one of these big balloons and sent it up to 90,000 feet. Very successful piece of work, pushed the limit on the fluctuations down quite a bit - we almost discovered what is called the dipole in the radiation. That is, half the sky is warmer than the other half because we're moving [through the radiation in the direction of the warmer half of the sky], so there is a Doppler shift that makes half the sky look warmer. Peebles had predicted this, predicted its magnitude. And if you look at Paul's data, he saw it, but not with enough conviction that we were willing to say we've discovered the dipole.

It's another curious story. Paul saw the dipole at about the right magnitude, but almost completely in the opposite direction from what we had predicted. To predict the direction you assumed that the center of our galaxy is fixed with respect to the radiation and that we are moving through the radiation because of rotation of the galaxy. So you know which direction we're moving and that should be the warmer direction in the sky. Well it turned out the warmer direction was the other way. There was a lot of head scratching about that. I spent several days in the library trying to convince myself the astronomers had the right sense of rotation of the galaxy, which they did. So the only interpretation was that the galaxy was actually moving very quickly in the opposite direction, and it's turned out that's the case. But it was one of those surprises in science, those things you don't expect that happen, and you do a lot of head scratching before you publish something like that.

Q: So you could have discovered the dipole and the bulk flow in the same experiment.

DW: Yeah. In this really crude apparatus that Paul and I built. It was a real Rube Goldberg by today's standards.

Q: Meanwhile, while you were doing these balloon experiments and looking for the dipole and maybe even seeing it, I understand that by the mid 1970s you also began talking to people about a satellite experiment. How did this COBE (Cosmic Background Explorer) satellite business start?

DW: It became clear that what one needed to look really carefully at this anisotropy and to look very carefully at the spectrum of the radiation to see if it fit this classical thermal spectrum - intensity versus wavelength -[was] to get into space. You had to get the atmosphere out of here. These are pretty delicate measurements, and the atmosphere causes all kinds of trouble, mainly from water vapor and oxygen emission. And it's clumpy in the atmosphere, and you see all these clumps go through; it makes your signal noisy.

Several of us who were active in the business - Rai Weiss, John Mather, Mike Hauser, and I'm sure I'm forgetting somebody11 - got together at [the Goddard Institute for Space Studies] near Columbia University, and started talking about a satellite to do both of these jobs, to look at the spectrum and to look for the fluctuations, if there were any. That was a long haul. It took several years, of course, for NASA to go through its usual procurement procedures and start sending us money. It was a fairly complicated satellite, complicated orbit. So there was a lot of interaction with NASA engineers. The science team got pretty big and unwieldy as people wanted to join. Then Challenger [the Space Shuttle disaster] came along and put us back 5 years because COBE was supposed to be launched on the shuttle. Well that wasn't going to happen after Challenger because we needed a west coast launch and NASA cancelled its west coast launch facility after that. So the Goddard Space Flight Center engineers completely reconfigured the satellite.

Well, that's a little bit of a distortion. We always had in the back of our head that maybe we'd have to go on a Delta rocket, so it wasn't a complete coincidence that this thing could be modified to fit into a Delta. We didn't have to change any of the structural stuff. We did have to make some modifications in shielding and so forth.12 So that took several years.

11 Hauser's recollections of this meeting are presented on page 418. His records show that the meeting included John Mather, who initiated the meeting, Michael Hauser, Dirk Muehlner, Patrick Thaddeus, Rainer Weiss, Joe Binsack, and David Wilkinson.

12 Michael Hauser describes the situation in more detail. "In the initial COBE studies, NASA required the designs to be compatible with either a Delta or Shuttle launch, but early in the design phase NASA decided on the Shuttle launch. The spacecraft and instruments were built and being tested when the Challenger disaster occurred in 1986. After some months of uncertainty, NASA decided to launch COBE on the last remaining Delta rocket. GSFC engineers had to re-design, build and test the spacecraft structure and Earth—Sun shield (deployable instead of fixed as in the Shuttle version design). The FIRAS and DIRBE instruments for

Finally COBE got launched in 1989. Early in 1990, only about [eight] weeks after launch, John Mather announced COBE's measurement of the spectrum and it was spectacular. When I first saw it in December, the hair literally stood up on the back of my neck. I can remember the feeling because my students and I had been plugging away at this curve one point at a time for 25 years, and here all of a sudden was the whole curve spelled out in great detail with tremendous accuracy. No question about it: we were looking at a spectacularly accurate thermal spectrum. When John announced this at the [American] Astronomical Society meeting on January [13, two] months after launch, he talked about the apparatus first and tried to convince people that the experiment was working. And of course people [thought that his] not showing us the results [meant] there must be something wrong. Then he threw down the spectrum and the whole audience stood up and applauded. It's very rare at a scientific meeting for that to happen. But there was expectation. People knew what COBE was going to try to do and didn't have much faith that it would happen, unless you knew a lot about the apparatus. Then all of a sudden there it was - clear as a bell. The universe's big bang. No doubt about it.

[Two] years later George Smoot from Berkeley announced the [COBE] results on the fluctuations, which are much smaller and harder to measure so it took years really to begin to see them in a convincing way; years of averaging, scanning, averaging. Again [the result, this time the detection of anisotropy] was quite a sensation. I'm not quite sure why but the popular press grabbed hold of it. A few scientists made some outrageous statements like looking at the face of God and all that kind of stuff. So it got hyped up to the point where it was ridiculous. I was almost embarrassed to go out and give a talk because of course our colleagues were saying, what are these guys doing? Why are they hyping this up so much?

Q: Was the discovery of anisotropy a significant result, an important result?

DW: It was very important to finally measure the level of the anisotropy and that's because the theorists had all kinds of reasons for believing it had to be there. The main reason is that unless you have some fluctuations in the density and temperature in the early universe, very tiny fluctuations -one part in a hundred thousand for the density fluctuations - you can't make galaxies and clusters of galaxies and all the magnificent structure that we see in the universe today. You can't start out with a perfectly smooth matter measurements of the CMBR spectrum and the CIB required only minor modifications, but the DMR anisotropy instruments had to be re-designed to fit within the reduced volume of the Delta rocket shroud. In spite of these challenges, COBE was launched in 1989, the year in which COBE had been scheduled to be launched on the shuttle at the time of the Challenger loss."

distribution way back there and end up 14 billion years later with what we see in the sky. These were hard calculations. So first [the theorists] said, well, [the CMBR temperature fluctuations] will be a part in a thousand. Well we got to that level pretty fast with the measurements. Well it wasn't there. Well it will be a part in ten thousand. Well that didn't work out so well either when we got there with our measurements. So they were beginning to panic, literally panic. Because the whole standard cosmological model didn't make any sense if those fluctuations weren't there. So a lot of this hype [about the anisotropy detection] that went on came not from the COBE team but from the theorists who were just breathing a big sigh of relief that yes, OK, things make sense again. And [a temperature fluctuation of] a part in 105 is very well accepted now. These little fluctuations are only 30 microkelvin from place to place across the sky - not an easy measurement to make.

Q: So this satellite goes up, was very successful, and as always the question is now what? What's the next important thing to do? Tell us a little bit about your reluctance to work on another satellite and how you finally decided you had to do it anyway.

DW: Well, what to do next after COBE was a big question. Now, this field had attracted a lot of very good experimentalists around the world. So there was a lot of activity, from balloons, from the ground, from mountaintops, from everywhere you could go, still hampered, however, by not being able to measure the whole sky with a clear shot not looking through any atmosphere. So a lot of ingenious experiments went on during that period of time. We did some in our group here that were good experiments, from Saskatoon and from Chile and wherever we could go where we thought we could get a good quiet sky to look through. But again it became clear that a satellite was needed to really go after these wiggles in detail and to get the smaller ones. COBE had very big beams so the [measured] bumps on the sky were large. One needed to actually have a telescope on a satellite so you get narrow beams and get higher resolution. Everybody knew this, knew that that was the way to do it. But it turned out there wasn't really an appropriate mission defined by NASA to do this. It didn't need a $2 billion-grade observatory, you just didn't need that big a satellite. On the other hand it couldn't be done with a $30 million- - what's called a small explorer - satellite. So some of us were behind the scenes urging NASA to start a new program called the medium-sized satellites. This is another one of these things in science where you recognize that there's the need for [an agency to change] their plans a little bit; takes years. Also, I was not eager to get involved with another satellite project. I like the model of a couple of graduate students and a professor and some undergraduates building an apparatus, going off to Canada or Chile, and making measurements as a team and so forth; and not these huge enormous groups with literally hundreds of engineers, dozens of scientists. And COBE was not a good experience sociologically. The team mostly got along but when it didn't get along it was pretty painful. So I wasn't at all sure I wanted to do this again. Went out to Jet Propulsion Lab because they have a good satellite program out there. I asked them if they were interested, they said oh yeah. Came back; never heard from them for a year and a half. [At] Goddard Space Flight Center though, a friend of mine there named Chuck Bennett called me up out of the blue not knowing that I had gone out to JPL and said, don't you think there ought to be a satellite to measure this anisotropy? I said great, I think so. You want to do it? And he said yeah. I said OK: a couple of requirements. Faster and cheaper I like, [but] it won't be better because it's faster and cheaper: the science team has to be small and tight and everybody has to do something [on] the science team. One of the problems with COBE was that there were people on the science team who really weren't contributing and there was a lot of resentment around that. Chuck completely agreed because he had gone through the COBE experience as well. So that was the beginning of MAP, the microwave anisotropy probe [now WMAP]. JPL came in with a proposal with University of California collaborators, Caltech collaborators. MAP won the competition and we started building it. And that was a completely satisfactory, satisfying experience. It was a small group. Everybody worked. All the jobs were done where they should have been by the people who had the expertise. Very little was farmed out to industry where you have a lot of trouble with contracts, engineers that don't understand the science. So MAP was a very good experience.

Q: I understand the heart of the satellite was actually built right here at Princeton. Tell us a little bit about that.

DW: In the division of labor for MAP we all agreed that the expertise for building the instrument was here at Princeton. We had built a lot of instruments. We had a lot of experience with very high-tech microwave components. We had a good relationship with the National Radio [Astronomy] Observatory in Charlottesville, where there was an ingenious engineer named Marian Pospieszalski who knew how to build an amplifier that was absolutely key to the whole thing. There are 80 of these amplifiers in this satellite, all built by Marian's group. The whole mission couldn't have worked without it. But we had a good relationship with Marian and with the Observatory. So it really made sense to build the microwave instruments here. That's where the expertise was; it just made sense. On the other hand, the satellite and all the associated electronics and support equipment obviously should have been built at Goddard because that's where they have the expertise. That's the way we divided the labor and it worked out very well. We built the instruments here, shipped them down to Goddard, they integrated them into the spacecraft. We did a lot of the testing here before we shipped them, and we did spacecraft-level testing down there. The project went very well.

Q: Tell us the story of the contract.

DW: Working with NASA is sometimes kind of frustrating because the scientists and engineers there usually don't get involved with contracting and the financial reporting and all of that stuff. And there are a lot of requirements. So when the Princeton contract to Goddard to build these instruments [arrived] it was about an inch and half thick and I obviously wasn't going to read this thing -1 was too busy trying to build instruments. I flipped through it and it was all boilerplate. Just stuff they pulled out of the files. It was appropriate maybe to Alcoa Aluminum or somebody like that but it certainly wasn't appropriate to Princeton University. At that point NASA was not collaborating so much with small university groups. Large labs like the Johns Hopkins Applied Physics Lab, places like that, yes. But for small groups like ours the interface was very rough. The financial reporting business I understood: we had to comply. So we actually had to hire a person to do that, Susan Dawson. She was great; she took all that off my table. I sent the contract back and said send me a three-page contract and I'll sign it. But forget about all this boilerplate. And they did, I think primarily thanks to Chuck Bennett, who really wanted this project to go. He was able to convince the contract people that we were not some big aerospace company. That was one of the rough spots but that got resolved very quickly.

Q: Where physically were these instruments built?

DW: The instruments were built in Jadwin Hall in one of our labs in the gravitation group there. Most of the work was done by Norm Jarosik [a senior research staff member at Princeton] and Michele Limon [a postdoctoral fellow at Princeton]. We built a lot of specialized equipment here at Princeton in the machine shops. Having a first-rate machine shop was just essential. We would not have gotten that $8 million contract without a good machine shop. That's the sort of thing that people don't often think about.

I once alarmed the Dean by saying, I don't care what you do with the library but don't take away our machine shop. That shook him up a little bit. The facilities, the people that you have to back you up, and the machines, are really important. NASA actually bought us a couple of very nice numerical machines in order to do this project.

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