[Cover of Sullivan's book 2009, Cosmic Noise]
Sullivan's Cosmic Noise, Cambridge University Press, 2009


NATIONAL RADIO ASTRONOMY OBSERVATORY ARCHIVES

Papers of Woodruff T. Sullivan III: Tapes Series

Interview with Thomas Gold
At the AAS Meeting, Haverford, Pennsylvania
June 24, 1976
Interview Time: 1 hour, 28 minutes
Transcribed for Sullivan by Bonnie Jacobs

Note: The interview listed below was either transcribed as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009) or was transcribed in the NRAO Archives by Sierra Smith in 2012-2013. The transcription may have been read and edited for clarity by Sullivan, and may have also been read and edited by the interviewee. Any notes added in the reading/editing process by Sullivan, the interviewee, or others who read the transcript have been included in brackets. If the interview was transcribed for Sullivan, the original typescript of the interview is available in the NRAO Archives. Sullivan's notes about each interview are available on the individual interviewee's Web page. During processing, full names of institutions and people were added in brackets and if especially long the interview was split into parts reflecting the sides of the original audio cassette tapes. We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for a 2012 grant from American Institute of Physics, Center for the History of Physics, which funded the work of posting these interviews to the Web.

Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event.

Part 1

Sullivan

This is side two, continuing with Tom Gold on 24 June í76. So Woolley just said, "get rid of this..."

Gold

"Get rid of this," and then there was another item. I had wanted the solar department to equip itself with a high definition solar magnetograph. I'd argued that the that most important thing that remain to be done was not just to look at every God damn flare and chromospheric eruption or something, but get to know more about what's going on. And the obvious thing was the magnetic field and so I'd said, "Well, one has to build a much higher-definition magnetograph." It need not be able to measure weak fields. Previous to that, the only magnetograph that people had made using the Zeeman splitting was able to measure down to quite low field strengths and measure the field quite accurately. And I said, "Well that's what's interesting me. I don't care whether the field is 2000 gauss or 3000 gauss but I want it on the scale of the flares."

Sullivan

Right, high angular resolution.

Gold

Yes, high angular resolution, and very coarse resolution in field if you need to accept that. And I had then lined up one Jim Ring who was then prepared to come and join the Observatory and we'd arranged that an appointment would be offered him and so on to build such a gadget. He's a superb optics manipulator and I'm sure he would have done a very good job. And at again Woolley just threw that out, that in fact at the IAU meeting in Dublin just before- well, he was already appointed but before he'd come to the Observatory, he was so rude to Ring that Ring immediately informed me that he was not going to come. So with that attitude, I mean, it was just absolutely clear that I couldn't stay there. And so then when I couldn't stay there, then I dickered a little with other astronomical appointments in Britain and then out of the blue a telegram from Harvard that was offering a full professorship and that sort of clinched the matter.

Sullivan

Was there anything else at Harvard that you should describe relevant to radio astronomy? You were Director there for a year?

Gold

2 years, 2.5 years.

Sullivan

And this was, of course, when many students came through which are now leaders in the field, like [David S.] Heeschen and...

Gold

Heeschen, Frank Drake...

Sullivan

There's about a half a dozen of them. Do you have any idea how you were able to pick what can now be seen as being successfully?

Gold

No, I don't think I can really take any credit for that. That was done with a whole committee working, going over records and so on. Itís also just that to get into Harvard as a graduate student, it tough and you have that selection.

Sullivan

So what attracted you to Cornell?

Gold

Well, the Arecibo situation. I'd been at Cornell for one semester and also on a personal basis liked it better there but only that. And I didn't like the big city life of Cambridge, Mass. I really had nothing against Harvard. I thought them very pleasant, too. But I was not yet so deeply settled there and when Cornell came and said - they'd offered to set up an interdisciplinary center for radio astronomy and various other topics, that would combine engineering and physics and they would want to offer me the directorship of this. Well, I found that was very attractive and that the planning that Bill [William E.] Gordon had meanwhile been doing for building a large radio telescope that that would be part of this package, part of this center.

Sullivan

So this is '59 now?

Gold

This is now '59, yes.

Sullivan

And what stage was Arecibo at then?

Gold

In negotiation with the Defense Department.

Sullivan

That had all been designed and you had a price and you were just trying to get...?

Gold

No, no, by no means. It was just that the money for it was sort of earmarked from the Defense Department. The background of it goes back a bit further and I have to be very careful about that because there was some strife between me and Bill Gordon in later years. I must be very careful that I don't overstep anything. What my complete recollection is that in '56, I believe, or '57, '57 I suppose, I was in Boulder at some meeting with- well, Bill Gordon was also present. I was then at Harvard and he was at Cornell but I knew him. And he was on an NSF [National Science Foundation] committee to concern itself with the question of building large radio telescopes. And he had at that time so far as I know no notion of doing any such job himself. He was merely an engineer concerned with...

Sullivan

Consultant to this committee...?

Gold

Consultant to this committee. And I discussed with him then the situation. I said, "Well, we have a large steerable dish built at Jodrell Bank." I had always wondered whether a fixed dish, very much larger or a steerable one not so large, was the best to do now that there was a large steerable one. I felt that a very large non-steerable one was the next step to take and I gave him the views that Iíve mentioned to you earlier, about radar to the planets requiring a big and not very steerable instrument and so on. And so I persuaded him to carry to this committee the notion of a large non-steerable dish. Now, and to my knowledge, that is indeed what we did. But then within a year of that time or so he developed- he or Ken [Kenneth L.] Bowles and history does not know exactly who or whether both independently, developed a notion of incoherent scatter from the ionosphere. And he had undoubtedly the wrong picture of the physics of it and Ken Bowles what turned out to be the right version namely, the critical matter whether the bandwidth of the scatter signal is that of the thermal motion of the electrons or of the ions. And I remember the debate and Ken Bowles had no idea why he said the right thing either. And I remember debating it with them on a visit that I paid to Cornell and I even had a bet on the subject. I wrote it up on the wall so it couldn't be lost, in which I sided with Ken Bowles and gave in detail the reason that if you are dealing with a wavelength that was shorter than the Debye length, then you would be following the ions and not the electrons. The electrons would be following the ions and the density fluctuations you would be seeing would be the density fluctuations, of the ions, and therefore the bandwidth would be the ions. And, of course, a very critical because the whole thing would not have been doable. If only now with the most sensitive receivers and the whole of our receiver, only now after that many years been able to get an electron signal from the place where the regime is reversed. In other words, if it had been that it really was the bandwidth of the electron, you'd never have seen it, I think. It wouldn't have worked. And Bill Gordon thought that's what it was. It would not in fact have worked. Whatever calculations he must have made at the time must in fact have been in error because he claimed [?]. But Ken Bowles had it right. But it was this incoherent scatter that Bill Gordon then took as the main reason for building the kind of instrument, which however fitted in this approximate description that we had previously discussed, as being the next desirable thing to build.

Sullivan

So you weren't around pushing Arecibo at that point?

Gold

No. I wasn't and I claim no credit for that, but I do claim that I was the person who first stuffed Bill Gordon's ears full of the notion that the fixed dish in the ground was a good thing. And he had what turned out to be really a wrong reason for building it, but luckily it was turned right by the...

Sullivan

When did this get straightened out relative to the construction of Arecibo?

Gold

I think Arecibo had already begun by then, before Bill Gordon was persuaded that it was going to be the ion bandwidth.

Sullivan

So you're claiming that he really didn't appreciate that the whole thing wouldn't have worked if he had been right himself?

Gold

That's what I would say, yes.

Sullivan

When you got to Cornell, Arecibo was in the talk stage?

Gold

It had not started. It was in the talk stage with the Defense Department and shortly after I assumed the directorship of the Center the first construction meetings and so on were held.

Sullivan

Was this under the Center?

Gold

Yes. It was immediately from the beginning put under the Center and therein then lay the problem that when the thing became a very large project, then Bill Gordon felt that he should not have been constrained to be under anybody's center and wanted to be directly under the Vice President for Research as a separate thing. My center had another 20 different contracts but none of them were as big. So at any rate, this produced some troubles. Bill Gordon just wanted to be totally independent. Although I think that I never interfered with his management of his contract in any way. Unfortunately not, because I had misgivings about the feed right from the beginning, which turned out to be correct.

Sullivan

Can you be more specific?

Gold

A contract was given to one Allen "K" in Cambridge, Mass. for the feed which was the only technically difficulty scientifically.

Sullivan

Not this support structure but the feed itself?

Gold

The line feed was the only thing where there was an electrical scientific problem involved. And K Industrial Company claimed that they had solved that, no problem.

Sullivan

This had never been done before, such a long line feed?

Gold

Never been done, not even an object of that general nature. I had some experience with antenna work during the War. I understand antennas, I think, quite well and I was very skeptical of this object right from the start. When it was finally put in there the whole dish was 6 dB below par, that's an awful lot, it's a quarter of the size only that it should be for the collecting area. And I suspected the feed was involved. There was a period where Bill Gordon kept saying, "Oh, no, it will only just be- maybe this is not quite correctly adjusted focally and we'll have to move it up a bit and move it down a bit." But two years went by and it still wasn't any better. Then eventually a little bit of a more careful survey was done of the electrical properties of the whole system and it showed that it was indeed in substantial error. And then I invited Ron [Ronald N.] Bracewell to Cornell and discussed with him whether he would spend some time on the matter of trying to find out what was wrong with it.

Sullivan

What year is this with Bracewell?

Gold

I suppose it must have been '64 or '65.

Sullivan

So the two years before that was when there was this adjustment and troubles?

Gold

I forget. When was Arecibo finished? The main construction?

Sullivan

'61 or '62, something like that? I'm not positive.

Gold

'63? And maybe Bracewell was there in '65, something like that. But anyway, Bracewell then investigated the matter and I also had one Vic Rumsey given a small contract for investigating feeds of this nature and before long Bracewell had already come up with the first key idea of why it was wrong. The azimuth modes of the radiation pattern of the feed and demonstrated. That was an error in that and I think [Victor H.] Rumsey came up with a polarization error calculation that showed that to be also substantially wrong and it was quite clear that the feed was basically no damn good. Then followed a very distressing, to me terribly distressing period. It was a very major item to us. 6 dB was no joke. And of course Bill Gordon was always a little bit constrained to belittle it and say, "Well, we still have the discrimination of the other advantages," but I couldn't really see myself supporting, speaking in favor of a successful instrument that was 6 dB below par. So I organized that ARPA, who was giving us money then, allow me to place a contract for a better feed. We couldn't possibly do that ourselves. We decided we had the input from people like Rumsey who had worked by then for over a year and Wielebinski worked for over a year on this deal. And we had a reasonably good idea of how one might go about it.

We then went to Allen Love at Automatics in California. He's a great antenna designer. We placed a contract with him to go into that. And all was fine, he made some measurements and he then suddenly told me he was momentarily stuck because there was a problem that he could not solve. At the moment I don't place correctly which the electrical problem was. But in any case there was a serious technical problem and he at that moment neither he nor I nor Rumsey nor anybody else saw a clear way through that. So I said, "Well, in that case, we'd better sit back and think for a little while." But you're running a big contract there and if we sit back and think all your staff and everything else gets put on the payroll of this contract and we run out of money before we've done the thinking. So I said, "Should I not interrupt the running of the contract temporarily and so Automatics will not charge any overhead?" And so Love says, "Yes by all means, there's no point in wasting our money that way." So I go to ARPA and I say, "We wish to make a temporary interruption of this contract and we will resume it as soon as we've been able to puzzle out this. At the moment all we want to do is tell Mr. Love think about it." So we do that and a short time later a statement comes from ARPA [Advanced Research Projects Agency], "It is obvious that you have failed with the whole contract work and we've decided instead of temporarily interrupting it we've cancelled it." By the time that this letter comes, Love has already found what is a brilliant solution to this whole problem. It turned out to be a brilliant solution. So I write back furiously and say, "No by now we already know how to do it." Too late. Out. Finished. We then go on for three years before under somebody else's management, [Gordon H.] Pettengill, the Defense Department allows another contract to be placed.

Sullivan

To actually build the feed?

Gold

That other contract is then done to exclude me carefully because I had goofed, is their story. It picks up precisely where we left off, it has big major meetings with all kinds of important antenna consultants. It ends up advising that the Love solution be accepted, which is the one that he had had at that time. It goes back to Automatics, they design the feed, the feed is built, it works brilliantly. And three years were lost and in addition to an extreme measure of annoyance for me.

Sullivan

Was that '68 when the feed finally worked?

Gold

Something like that, yes.

Sullivan

Was this when [?] came into the scene under Pettengill?

Gold

No.

Sullivan

That was still later?

Gold

That feed is nothing to do with [?]. That feed is the circularly polarized feed which is the difficult thing. The linear polarized feeds are regarded as trivially simple right from the start.

Sullivan

And these are the ones with [?].

Gold

That was my prescription from the beginning that [?] was making. It's just say a tailor-maker the width of a guide so it makes the right phase velocity in measuring and you can't go wrong. And that's all [?] been doing. I mean I won't belittle him. He's done it very well. But that never was a problem. The great electrical problem had only to do with how to- when you did not have this freedom because it emits circular polarization and for going through the ionosphere you must do circular. And so we were involved with that difficulty. And then Love had found this brilliant solution with little hacks every few inches, which is what the present feed is. I mean, the final thing after all the heavy meetings and all the nonsense that went on three years clean wasted, it was finally built and the cost must have been enormously more than what it would have been if that initial contract had been allowed to continue. That was the biggest mess I ever got into because an absolute idiot in the Defense Department by the name of Colonel [Dowel?], I know this is going down on record but I wouldn't even mind if he heard it, who must have been the worst manager of large sums of money that I've ever seen.

Sullivan

When did Arecibo do its first astronomical observations?

Gold

I don't remember.

Sullivan

Was it only one feed?

Gold

Oh, no. It was on time with the old feed.

Sullivan

With the 6 dB loss.

Gold

Yes. Bill Gordon, I think, was largely inclined to smuggle the whole problem away, to just say, "Well, it's a very fine instrument and all is well, nobody needs to calculate just exactly how many dB it ought to be or the flux units you ought to be seeing from a source." Well, I wasn't quite willing to do that. Bill Gordon, I suppose, thought that I would pick on the shortcomings of the instrument to irk him. I think he took it as a bit of a personal sort of thing.

Sullivan

What did you see as the major contribution to astronomy that this instrument could make besides the radar astronomy?

Gold

Well I was myself very keen on the radar, of course. I was very keen also that we should have an in-house radar team which finally when NSF took over they did not want. That was also a bone of contention between me and the NSF. I thought it was absolutely ridiculous to have an instrument like Arecibo which was so ideally suited for radar and not have a permanent team on the site to use it for radar. It's very difficult to do radar as a guest observer because you have to do it year after year, every step you take helps you for the next round of observation. You have to get the ephemerides more accurate than they are known before, before you can even observe the next thing, you see. So it was through my intervention there that I got Pettengill onboard in the first place, made him Associate Director. He then got the radar business working and that was my management. And I had hoped to build up from Pettengill a permanent group there.

Sullivan

I suppose you were also interested, you were involved in this controversy over whether space ships would sink in the dust in the moon and so forth and the radar would help to discriminate this thing?

Gold

Well, I was certainly keen on Moon radar. Mind you, I am terribly misquoted on this business of space ships sinking in the Moon.

Sullivan

It's not directly radio astronomy but I'm still curious as to what you'd say about it.

Gold

Well, in fact I used the earliest radar data to say that it was clear that the Moon had a dusty surface which was remarkably smooth. And the earliest data that were relevant to this were the 10 cm data taken at TRE [Telecommunications Research Establishment] in Britain. And they showed a very substantial central brightening, central bright spot on the moon.

[Interruption]

Sullivan

You said you had used the 10 cm TRE data.

Gold

To say that the Moon had a much too smooth a surface at 10 cm to be understood as the impact scarred hard rock surface and I'd taken that to imply a dust covered Moon. I had always insisted that it was dust, that it was a deep that deposit of it, but by no means that it would be soft. I had said in those earliest years such things as it's a deep deposit of small particles that makes up the plains on which Denver stands. Yet when you land on your plane in Denver you don't expect to sink kilometers down. So I definitely said that the deposit is very deep but how firm or loose it is I cannot tell. I would say that the main danger in a landing would be blowing of dust in the exhaust and that indeed it was. That was a danger and the first mission was almost aborted because of that. And that I insisted on would be the case because then I couldn't see that it could be firm enough not to blow up in it. But so far as the bearing strength I said I don't know. My feeling is that in the vacuum itís much more cohesive. I've written that in many papers- much more cohesive than such a powder would be in air but even in air such a powder might well have enough bearing strength. On the other hand I said one thing, I said, "Without having been treated by wind and water the Moon's surface is not assured of having everywhere been tested with a certain load." Well, on the Earth almost everywhere you know it has been so tested. I said there are a few places that have not been so tested and then one has to walk with the greatest of care, namely glaciers. The snow on a glacier has only been there for a short time and there you don't know when it's safe. And I said well, I would regard it in the same sort of light of saying, if I were to walk around on the Moon that had not been tested with wind and water I'd prefer to be on a rope. That's what I said. But for the bearing strength no, I thought that probably the vehicle would be all right but I would bear it in mind that there is a possible problem.

Sullivan

You were not particularly interested that Arecibo shed light on this...

Gold

Well, you see, let me say one more thing. The newspaper people always came out with this absolute rubbish that when I said the deposit is some kilometers deep, they wrote, "Gold says you will sink kilometers deep." And I can stand on my head, I said, "Look you go to a sand dune and it's so deep and you don't expect to sink to the depth of that." And I found out in the end one reason for that is that they'd all read Mr. Arthur Clarke's rubbish of moon dust who acknowledges he had the idea of dust from me. And then he wrote a novel out of that in which people apparently, Iíve never read it, do sink out of sight. So that's how this whole miserable story comes about. But it pursues me around the world. People saying, "Oh, but you weren't right about the depth of the dust." I said, "Well I'm damn right about the depth of the dust and I never said you would sink that deep into it." But it's always the same story. People always identify the depth of the dust with the sinkage.

Sullivan

What you're talking about is how far you have to go down to get to bedrock?

Gold

Yes.

Sullivan

And what is the current story on that? I guess it's not known really, it's only been probed indirectly anyway, a couple of meters.

Gold

My lunar colleagues always hoped that the bedrock is just below the deepest that they have probed to. The radar evidence from the Moon is absolutely over-powering that there is no bedrock to a depth of several hundred meters. Because at the long radar wavelengths we've seen the Moon at 7.5 meters resolved in fine detail and at 7.5 meters the transparency of the soil that we've measured is such that you would go of the general order of 50 wavelengths-100 wavelengths into the ground. And if there were a rough bedrock underneath you would see the echo from that, it would give you a much brighter Moon than we have and it would give you virtually no limb-darkening. And the moon is limb-darkened by 32 dB.

Sullivan

Was there anything else in your direction of the whole Arecibo building and so forth?

Gold

Well, I then organized- I was always the one to organize more the radio astronomy work there while Bill Gordon was interested almost entirely in the ionosphere.

Sullivan

What was the main thrust of the radio astronomy programs?

Gold

Mixed, all kinds of things. And, of course the moment the pulsars came along we were very hot on the pulsars.

Sullivan

But you weren't particularly directing a program that you had interest in. You were just taking proposals and just deciding their merit?

Gold

That's right. I was taking proposals, I was deciding their merit. I was discussing here and there individual programs with people but that's all.

Sullivan

And you never, I don't think, actually got involved in any radio astronomy observing yourself?

Gold

No.

Sullivan

Rather curiously perhaps, haven't you ever had that urge with your radar background?

Gold

Well, when youíre directing a big instrument like that itís not all that easy. And also I never spent any long periods of time down there. I sort of got that established, I would go down there once a month, supervise the running of it, straighten out all the personal strife that went on and all the nonsense that went on and then I came back. And I would have had to stay a considerable period of time down there. But I always had a local director and if I stayed down there I was afraid that I would get in his hair. It's always a little touchy business. As far as the overall [?] spent time down there, while Bill Gordon was the local director I wouldnít in any case because there was a little friction and then later it sort of got established that way.

Sullivan

Sure, I can see that. So basically you just didn't have the time?

Gold

I didn't have the time, yes.

Sullivan

The last thing I guess, if you could just talk about the discovery of the pulsars. You heard about them along with everyone else and then what your interpretation was, how they struck you in those first few months.

Gold

I suppose it was the end of the February, when the Nature article that was published, that was the first that I had heard. Frank Drake, who was then the local director at Arecibo, immediately proposed to do observations and I, of course, immediately concurred with that and that was done. I think three days after the Nature article had reached Arecibo, Arecibo already had better data on the then one known position pulsar 1919, had better data on it than Cambridge had ever been able to obtain, of course , because of [?]. My view was immediately that, went back to what I told you earlier the notion, small condensed objects would be able to radiate well because of magnetic fields with gradients and so on. So I immediately worked out sort of a number of things and I worked out firstly what would be the spinning speed of a neutron star that had collapsed from ordinary stellar angular velocities and what would be the magnetic field. And it was a complete surprise to me how enormous these two figures turned out. And apparently a complete surprise to everybody else too. I just invented that figure of 1012 gauss, which is sort of a canonical figure now.

But I just wrote, "Well, I suppose that ordinary stars may have fields of the order of 100 gauss and by the time you collapse it that's what it comes to." And the spin is the same, you see, and the kinetic energy of the spin. And so just from doing these simply calculations I immediately convinced myself that the only sensible source of energy that a neutron star would possess would be spin. The cooling is trivially easy to come to the conclusion that it would be very fast and so therefore any heat from the convection is immediately lost. So if these objects collapsed stars, if they were neutron stars well then the energy must come from the spin, there's no other energy they have. And I calculated various other things immediately: the brightness temperature [?] on the assumption that the pulse length defined the approximate size of the radiating region as it must do. It could be smaller but not bigger. So when I did that I immediately concluded the fantastic temperatures. I think the first sort of figure was 1021. So I said, "Well, obviously you cannot have 1017 ev electrons. You can't have 1017 ev electrons in the vicinity of a small object. You can neither accelerate them nor would they radiate in the radio waves. They'd radiate like crazy in the gamma rays. Or in any kind of curvature even though the field of, I don't know, 10-10 gauss you still radiate gamma rays. So that's obviously nonsense." So therefore I immediately said it must be a coherent radiation that you see. It's the only way in which you get that intensity. So then I said, "A coherent radiation I would understand best as being due to a cloud of electrons whirling around," and I still think to this day that's the best story. Because then they can readily organize themselves into a spatial pattern of coherence.

Sullivan

Like a travelling wave tube, that sort of...?

Gold

That's right. Theyíre all going in almost the same speed in any case, you see. But if you have any other accelerating mechanism to make energetic electrons well then I don't understand that they could be so well organized. The rotation is just ideal for that. And then I immediately noted another effect, namely that the clock precision, the mean precision of the clock, was enormously greater than the pulse-to-pulse precision. And that means that you must have an underlying clock on which the individual pulses can make an error without however resetting the clock by that error. And I immediately said, "Well, that argues completely against it being any kind of radial pulsations." Because if anything was radially pulsating then I would understand it that the next pulse would come into a particular phase of the previous one. The next pulse is sitting on top of the previous. There is no underlying clock.

Sullivan

So that's what put you off white dwarfs from the start?

Gold

Yes, yes. There is no underlying clock, you see. I can't have a radial pulsation that has no underlying clock. One pulse is determined by the phase of the previous. And that is so clearly in conflict with the most primitive plot that you make of pulsars. That individual phase errors are enormous but then you take the mean over a day and it's absolutely accurate to 8 decimal places, you see. So it's clearly out. And I was very disappointed that people didn't understand that. Even now in the X-ray stuff I had to get up in an X-ray conference at MIT recently and explain all this story again, that they had to investigate the X-ray by the same analysis to see what the right kind of story was. They didn't understand it even now. But in any case that was certainly the thing that persuaded me that there was an underlying clock, an underlying clock that was surely rotational. So I said, "Well, with its rotation then it must be neutron stars because it's much too fast for the white dwarfs than the standard magnetic field strengths of that order the energy is high for the white dwarf." You never had much energy either, you see, because the collapse the big energy comes from the collapse from the white dwarf density to the neutron stars. That's where the big energy comes from and a lot of that goes into the spin. Well, the white dwarf never has much energy of any kind. So I said it was a neutron star, you understand, an underlying clock, you understand the strong magnetic fields, you understand the large amount of energy available in the spin, and so surely that must be the right story. And then I said immediately then you would expect that there would be young ones that are much faster but they would all be slowing down, but that the youngest would be slowing down the most.

Sullivan

Was this before the slowdown had been found?

Gold

Oh, yes, yes.

Sullivan

How long did that take? How long a time scale?

Gold

Well, I wrote the article in Nature in, it was published in May, and Arecibo discovered the slowdown of the Crab in September or October.

Sullivan

Well, the Crab wasn't found until a year later or so, wasn't it?

Gold

That was that same summer wasnít it?

Sullivan

Was it that early, only a few months after the first pulsar? I was thinking that it was a year later sort of thing. Was the Crab the first one to have a slowdown picked up also?

Gold

Yes.

Sullivan

It makes sense because it's slowing down the fastest.

Gold

Yes, it was immediately seen from one day to the next, the slowdown was seen.

Sullivan

Well, I'll check that. I have the idea that [D. H.] Staelin and [E. C.] Reifenstein was summer of '69 or something like that.

Gold

Well, it could be and then it could be that I'm all out by one year. Yes, it was probably right.

Sullivan

But anyway, your slowdown paper you think may have been a year later also?

Gold

No, no, that was absolutely the first.

Sullivan

The prediction was still in the spring of '68.

Gold

The prediction was absolutely the first thing, yes. That immediately said that we'd expect to find pulsars- it said everything, it said we will expect to find them in the locations of supernova shells because neutron stars can only be made as a result of a dramatic explosion.

Sullivan

You were not bothered by the fact that there were no apparent supernova remnants near the others.

Gold

No, I took that in my stride and said, "We'll find younger ones that will have supernova shells." With the neutron stars they should be associated with supernova shells. If the supernova shells are still visible, then they will be younger and they will be spinning faster. We will see them, we will see the spindown and that was just all to be substantiated. Yes, but it may be that it was only substantiated a year later, yes. And then I wrote another paper a year later in which I put in the rate of energy loss from the Crab.

Sullivan

That fit so nicely, right.

Gold

That fit so nicely, yes.

Sullivan

Well, I think that's about it unless you can think of any other comments along the long trail that you've followed that you might like to make.

Gold

I must say, do you transcribe all this?

Sullivan

Oh yes, you'll be getting a transcription to correct and embellish if you wish.

Gold

Well, that's wonderful, but also I'd be quite happy to have a transcription because in fact I've been asked by the National Academy to record a biographical few pages. So, I don't have to go through the misery again, at least some part of it, just the radio part at least.

Sullivan

Yes, you can definitely have a copy of the final transcription. Thank you. That ends the interview with Thomas Gold on 24 June 1976.

Part 1

Modified on Wednesday, 17-Dec-2014 16:28:16 EST by Ellen Bouton, Archivist (Questions or feedback)