NATIONAL RADIO ASTRONOMY OBSERVATORY ARCHIVES

Papers of Woodruff T. Sullivan III: Tapes Series

Interview with Cyril Hazard
At the Institute of Astronomy, Cambridge
September 20, 1978
Interview Time: 1 hour, 6 minutes
Transcribed for Sullivan by Pamela M. Jernegan

Note: The interview listed below was either transcribed as part of Sullivan's research for his book, Cosmic Noise: A History or 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.

Sullivan

Ok, this is talking with Cyril Hazard in a follow up interview on 20 September ’78 at his office in the Institute of Astronomy in Cambridge. One basic question I didn't ask you before was what was your background training before you got involved in things at Jodrell Bank? What field?

Hazard

Physics. I took physics degree at Manchester.

Sullivan

At Manchester. And then you just continued?

Hazard

Then I just continued, yeah.

Sullivan

Was it more or less accidental that you got involved in radio astronomy or had you always had a liking for astronomy?

Hazard

No, I hadn't any liking at all, in particular. I mean except in the general sort of sense that I think people think they would like to do it when they see the pretty pictures in books and so on but no more than that. I think it was just one of those things that, you know, with so many grants being offered, and I was offered a grant that more or less said go to Jodrell. As it turned out as a matter of fact, I knew about Jodrell accidentally. In the sense that Greenhow who was working there on meteors, we were both from the same school and we were [?] in together at the time. So he used to going out regularly. I suppose there was some connection there, but no, it was accidental. It was just as likely, I think, that perhaps I'd have been put on cosmic rays or something like that at Jodrell, I don't know.

Sullivan

Once you did show up for the first day of work so to speak, how was it decided what you would work on?

Hazard

Well, I was just put with [Alan] Maxwell and [Alec G.] Little in a hut over there and they were doing scintillation work and I was told to build a stabilized power supply. I didn't know any electronics at all, but that was my first introduction.

Sullivan

I see.

Hazard

So I learned a little bit about it there. I mean, that was about all. That would probably be the only step, I think, going on in radio astronomy. Although [Victor A.] Hughes, Vic Hughes, was using the 20 foot, building a receiver to start plotting drift curves over the Milky Way.

Sullivan

For the 218 foot?

Hazard

Yes, which had been built, of course, to detect cosmic ray showers originally.

Sullivan

Right.

Hazard

But then...

Sullivan

Meteor radar work was also going on wasn't it?

Hazard

Yes, that was in other parts. We weren’t really connected with that, although in fact later on when there would be a lot of that stuff going on in the next rooms in the same hut and so on. But at that time there was a 20 or 30 foot steerable dish there which was, you sort of went out at night and clumped the ground a little bit.

Sullivan

Right. This is the one that Rod [Rodney D.] Davies did HI observations on at one time also?

Hazard

Yes, I guess it would be.

Sullivan

And what was the gain used for?

Hazard

Scintillation work on Cassiopeia and Cygnus and so on. I think probably that same term suddenly towards the end of that task, [Robert] Hanbury-Brown came and he started to work on the 220 foot. Hughes, I think, was still working on meteors- I can't remember if he was still there. But then I went over to work with Hanbury-Brown, on that experiment of doing the drift curves, which he never did actually.

Sullivan

Right.

Hazard

But that’s what we started off on with.

Sullivan

So you never actually published anything to do with what you started out.

Hazard

No.

Sullivan

Well, the question of Hanbury-Brown is really quite striking as I put together your bibliography because of fifteen papers you have in radio astronomy before 1960, all but two or three are Hanbury-Brown and Hazard.

Hazard

That's right. We worked very closely together.

Sullivan

Can you tell me what the nature of the relationship was? Was it both of you equally building equipment and interpreting or was there some division of duties?

Hazard

When I went over to work, I think the receiver was pretty well finished. There were things like getting the stabilized power supplies and so on, batteries and getting everything stable enough. There was a lot of antenna work to do. But I mean, I was learning at that time.

Sullivan

So you started off that you were just a greenhorn.

Hazard

On the electronics side, yes. I mean everything that I knew about electronics I learned from him.

Sullivan

But then after some years passed, you certainly must have become more equal colleagues in a sense.

Hazard

Well, only on the interpretive side I would say we pretty well worked from early on because we both turned out to know nothing. At that point where I started out knowing nothing and didn't progress very much beyond that in electronics. I mean, I could build a receiver, of course. By the time I'd finished, I built my own receivers at the end that would work and built all my own stuff, my occultation stuff. And I was interested in antennas after that. But I started off knowing nothing about it, and he was, of course, very good at it.

Sullivan

He'd been in it for twenty years.

Hazard

Yes. He was experienced. And on the other hand, we started off in a more equal footing on the astronomy. We both knew nothing.

Sullivan

Is the fact that he is always first an alphabetical thing, a seniority thing?

Hazard

Yes, it's an alphabetical thing mainly. I mean, I could, I think it would be rather invidious to go through it, but I could point out various things about them.

Sullivan

As to who worked more on one or the other?

Hazard

Yes. I mean the early writing he would do most, certainly on the M31 stuff, the analysis and so on we did together. The one about the clusters and galaxies and so on, that was my idea. And then we got to the model of the galaxy we started out with a staff of nine. Seems like M81, and things like that, would be pretty well the same. Things like Tycho’s supernova was an accident, I mean in that...

Sullivan

What about the Class 1 versus Class 2 sources, at least as [Bernard Y.] Mills called them?

Hazard

I did most of the analysis for that. I know that, I remember that. I don’t think there would be any argument about that.

Sullivan

That was your thesis largely, wasn't it?

Hazard

No, it was extragalactic. It was in there, but I would say the list of sources in there were pretty well entirely mine.

Sullivan

The other thing of course that is quite striking is that most of these papers, about three-quarters of them, are all based on this single antenna at the same frequency, same receiver I suppose.

Hazard

That's right.

Sullivan

You were really milking it for many years.

Hazard

That's right. And I think in many ways it was a pity that it sort of stopped at that point.

Sullivan

What stopped?

Hazard

You know, that shortly after that the whole thing was pulled down.

Sullivan

Oh, after you left.

Hazard

Yes. I mean they did build a tower after that you could tilt it over much easier than we could do it. And, in fact, I used it later on after I went back to do a 92 megahertz, with an interferometer and so on. No, I think the point is that you were stuck with a single frequency at that time because you, the upper frequency, about 160 megahertz anyhow you could get up to because of leakage through the dish. Even if you could have gone a bit higher, well, you couldn't really go any higher at that time. And if you came down any lower the beam width was bad and so on. But you know, you were pretty well fixed and locked in a pretty narrow thing anyhow. And of course what was happening by then was that it took a year or two to get the equipment going and then there was lots to do with it. But then I think that by certainly over that sort of period, things were changing, talking about interferometry and so on. There were other groups which Hanbury-Brown was more involved with.

Sullivan

We talked about the whole [Roger C.] Jennison thing in the last talk.

Hazard

Yes, and then the interferometer made an angular size and so on. A lot of that was going on while I was away.

Sullivan

You were away from 1954-57 is that right?

Hazard

Something like that yes.

Sullivan

This was military service?

Hazard

Yes, national service. So when I came back, which is a thing that you had down there actually. When I came back, I actually came back to work on the new interferometer which was being built. I sort of passed I was coming up from Portsmouth where I'd been working for the Admiralty and I passed in at Jodrell on the way back, and [A. C. Bernard] Lovell said to me, "Did I want to go back?" And then I think thought for a spell and probably said yes and we went down to Portsmouth, New Zealand...

Sullivan

So it wasn't that obvious to you that you were coming back then?

Hazard

Right. It wasn't that obvious. I hadn't, well, I had certain reasons for that, but then it wasn't at all obvious, not at that particular time. So- that I would have gone back. So I went back to work on the interferometer with [Henry P.] Palmer and so on, and I got as far as considering the size of the antennas and in fact, designing largely I think, or certainly taking part in the building of the first outstation antennas and so on. And I wasn't terribly interested in that work and certainly didn’t like working in the group anyhow, so I gradually drifted out of that again basically.

Sullivan

I see. I don't think that you ever published anything to do with that group either.

Hazard

I never published anything. I drifted off after about six months or a year onto my own again.

Sullivan

Well, while we're talking about this, what about this business about the data you had left and [?], could you set me straight on that?

Hazard

Oh yes. What happened was that when we were considering these sources in the galactic plane that one of the things which I did do, more or less for amusement and I can probably find you the sheets somewhere I wrote it on. I sort of decided to draw baselines and measure the half-widths of these things and estimate the sizes from the broadening of the beam. And it was fairly obvious from these things that these things looked to be about a degree, degree and a half or something like that across. I was just doing this on my own and I don't think Hanbury was terribly convinced about this, and maybe I would have pursued the matter a little bit further, if I'd been there I suppose. But I sort of left at that time and more or less forgot about it...

Sullivan

Right.

Hazard

Until I went back again, and when I found out that they measured, I just locked up this whole hostility.

Sullivan

Now what do you mean they had been measured?

Hazard

Well, in the meantime of course, I mean, the idea was coming that these were extended and one of the motivations for building the interferometer there, which Hanbury-Brown was starting at time on the, Dick [Anthony Richard] Thompson I suppose, on the measurement of angular sizes, was to measure the angular sizes of these particular sources which required fairly short baselines anyhow.

Sullivan

I see. So they had forgotten that something had been gotten out of your data or...

Hazard

They probably didn't know anything about it.

Sullivan

Yes.

Hazard

I mean, Hanbury probably knew but it was probably just one of those things where he said, "Hey, look, you know, these things look a little bit extended, if we measure them this way." And they probably didn't pursue the matter at that time very far. Except that we, I guess that we thought to extend them from this data, but whether it was worthwhile publishing because the difficulty of drawing baselines and so on. In fact, knowing what I know about these things now, I would have published it. But I was never very good at getting published anyhow.

Sullivan

So you're saying you went back to your old estimates and found that...

Hazard

That they were pretty well right. In fact I can probably find it.

Sullivan

Interesting. When the 250 foot was being planned and built, largely, that was while you were gone, but even before you were gone, there were certainly strong plans for it. Did you think that was a good way to go? Were you in support of that whole concept?

Hazard

Well, I think so at the time.

Sullivan

And what would be your reasoning?

Hazard

Well, we'd done so well, I suppose, with the very limited sky coverage and the limited sensitivity and stability and so on that we had on the 210 foot. There was obviously a lot that could be done, and I think that it was just a logical extension of the work we'd been doing, and it was rather difficult the way we were doing it, laborious. It would have been nice to have a much bigger one.

Sullivan

Okay. We didn't talk about the paper you had in 1951 on Cygnus "I" as you called it.

Hazard

Yes.

Sullivan

Where you measured its flux and position and also looked at the ionospheric scintillations. First of all, was it clear to you that they were ionospheric?

Hazard

I think so, yes. Because there was a lot of other work going on at Jodrell at that time on scintillations.

Sullivan

Little and Lovell.

Hazard

That's right. So we knew what these things were, yes.

Sullivan

And what about the nature of this Cygnus source, was it sort of a complete puzzle at that time? This was, of course, before the 200 inch...

Hazard

I think so, yes. I think that, in that respect it was clear to us, certainly it was clear to me by 1953 that they were all extragalactic pretty well and that in an article in the Observatory. It's not in a paper, it's the report of a meeting in the Observatory.

Sullivan

Yes, I think I've got... no, I don't have that year, but you're right, it's an RAS [Royal Astronomy Society] meeting.

Hazard

1953, I think. 1954.

Sullivan

Okay, I'll check that.

Hazard

And I stated it then and also in my thesis that whatever the reason behind it was, we were pretty convinced- actually by 1954 that these things...

Sullivan

But Cygnus...

Hazard

But Cygnus...

Sullivan

It was in the plane. You would have concluded, but it wasn't large, though.

Hazard

Cygnus was done by about then, wasn't it? Around 1954?

Sullivan

The identification?

Hazard

Yes.

Sullivan

It was actually late 1951; it was published in 1954.

Hazard

That's right. So we knew about Cygnus. I think that the point was that we were pretty certain that nearly all the sources out the galactic plane, were extragalactic.

Sullivan

Well, in fact, here's the final sentence of your thesis where, "It is therefore considered, in opposition to the ideas current at the commencement of the work discussed in this thesis, that the majority of the Class II sources so far observed are probably extragalactic objects." That's May, ‘53.

Hazard

Yes.

Sullivan

And so it seems that at least in your mind, now was this generally what people were thinking at Jodrell in radio astronomy?

Hazard

No, I think, I don't know exactly when this came about, but if you look at one of the Solvay Meetings in London a couple of years before, ‘51 I suppose, when [Fred] Hoyle and [Thomas] Gold were arguing.

Sullivan

There was one on ionosphere and other phenomena or something. That may be the one you're talking about. University College in London?

Hazard

Yes. University College.

Sullivan

Yes, I know the meeting.

Hazard

They were arguing that they were extragalactic and both Hanbury-Brown and [Martin] Ryle were arguing the opposite way. And I don’t think I had any particular ideas about that...

Sullivan

At that time.

Hazard

At that particular time, I can't remember, but...

Sullivan

What was it that made you so convinced by ‘53 that they were extragalactic?

Hazard

Well, in my thesis what I did was that I worked out the background radiation for a start, and it was fairly obvious to explain all this stuff in terms of normal galaxy with some sort of reasonable dispersion, it just had to be a little bit brighter. That it wasn't difficult at all to explain those things.

Sullivan

Explain what?

Hazard

Background radiation, the 600°K that sort of frequency.

Sullivan

The galactic background.

Hazard

The isotropic background.

Sullivan

Right. But you had split up the general background into an isotropic component and a disc component.

Hazard

Yes, yes. And it was fairly obvious by then that you could explain this in terms of galaxies. You have to have reasonable dispersion. They radiate in Virgo for a start, which I was talking about looked as though you could explained it with the same sort of enhancement that...

Sullivan

Right.

Hazard

I can't remember now, but I can’t remember exactly, I can't remember that far back exactly, but I know that by that time I was convinced that they were extragalactic, for whatever the reasons might be now. But certainly that was one of them- you could explain that radiation, that isotropic background in terms of the intergalactic emission from galaxies.

Sullivan

Based on nearby galaxies you had detected?

Hazard

Based on nearby galaxies that were detected and the fact that to explain radiation in Virgo rightly or wrongly, which I interpreted that to that also made it an enhancement of the emission over what you would have got from ordinary galaxies that we'd been looking for galaxies in clusters as well. [?] But certainly through working on normal galaxies, although the work on normal galaxies was certainly one of the reasons why Hanbury-Brown was arguing against it early on that the ordinary galaxies were too faint. But you see, you had Cygnus and so on by then and so it was basically a matter of working up what the density of these objects had to be, you know, what the density would be. And what I think I showed was that if you took the, you get the relationship between the background density, the flux from the galaxy, and the density and what it showed is that if you up the, if you took the density equal to that of an ordinary galaxies then you could explain it all with some sort of dispersion about that in just a couple of magnitudes or something like that. So I thought that meant a long tail, of course, but again, I didn't explore the term because again, that was the time I was leaving, but...

Sullivan

This would be a dispersion in the ratio of radio flux through optical.

Hazard

Optical flux, yes.

Sullivan

So you had some of what we would now call 'radio galaxies.'

Hazard

That's right. That's right. Well, I mean...

Sullivan

Most of them were emitting normally...

Hazard

Yes, I didn't pursue that matter any further at that time, but if you just took a reasonable ratio to these things then everything sort of fell into place. I mean, I think that was probably, I think it's in that most reasons would have been in that Observatory article.

Sullivan

Okay, I'll check that. I'll certainly have to look at your thesis, also. What about this business in ‘52, you mentioned that radio isophotes seem to agree with galaxy counts, and then later on, I guess ‘53, you talked about this strip from 11 to 13 hours and 40° to 70° dec [declination]. This is what we now call the 'super galaxy' or some people do anyway.

Hazard

Some people do, yeah.

Sullivan

And there were arguments at that time, I think also, at the Paris Symposium, about the reality of this. Can you tell me what you had and then how you interpreted it?

Hazard

Yes, again, it's all in my thesis. What we had was that when we drifted across this region what you found out was that there were fluctuations in the background emission, faint ones. They were only a degree or so. And what I did was that I took a Shapley-Ames catalog, on the back of the Shapley-Ames catalog, there were counts of galaxies done to something like half magnitude in various magnitude ranges.

Sullivan

Right.

Hazard

And I integrated that over our beam and I plotted what the distribution was of galaxies.

Sullivan

Smooth to your beam.

Hazard

And I found out that there was this resemblance between that and our beam and that this in fact, they would have the radiation from these things would have to be up by some factor to give the sort of- the amount of stuff we were getting by about a factor of ten or something like that.

Sullivan

Over our own galaxy?

Hazard

Over our own galaxy, over the ratio we'd found for other galaxies. And I found if you upped it by that amount, in other words put a dispersion in the thing, you could explain these things. The galaxies in bulk statistics were behaving differently from the individual galaxies that we'd got the normal ones. And there's an extension of that, of course with explaining the isotropic background I suppose, that it convinced me that most of the stuff was extragalactic. But anyhow, we found this bumps and if you looked at them you could see that some of them were, in fact, sources sitting in there. And it looked as though you could explain it just on the basis that you had an excess of galaxies there which is exactly the way it had been explained, and we were looking at a fairly wide beam, and sort of smoothing all this stuff out. Now I still think it was probably right, but there's been some argument about it which I couldn't understand what the arguments were. They didn't seem to make very much sense, quite honestly.

Sullivan

How does increasing the dispersion in this mean value of radio to optical magnitude or flux, how does that give you a higher...

Hazard

Brighter. The brighter one was just to get more and more bright ones and it really just said that among the...

Sullivan

But if the mean one doesn’t change?

Hazard

Yes, but I think the magnitude one...

Sullivan

If you still have a symmetric distribution...

Hazard

I'm not sure if that's true, because if you knock one up, if you take one galaxy and make one a hundred times as strong and one a hundred times as weak, and you take the three of them together...

Sullivan

Oh, logarithmically.

Hazard

Logarithmically, yeah.

Sullivan

Ah, you have a logarithmic distribution.

Hazard

Yes, a logarithmic distribution.

Sullivan

And you increase - that'll do it.

Hazard

Exactly. That's exactly what it did.

Sullivan

That'll do it, every time. Yes.

Hazard

So that's basically what it was, which is basically the way one looks at it now exactly.

Sullivan

Okay. Well, let's talk a little bit specifically - you had an article in Phil. Mag. [Philosophical Magazine] in 1953 about taking all the data on galactic plane surveys at that time and out of the plane to fit to a grand model and there were three components- the isotropic component, which you said was probably extragalactic; radio sources in the galactic center heavily concentrated which you associated with the population 2, and also these extended sources that you had in the HB survey.

Hazard

Yes sound about the way it must have been.

Sullivan

And 415.

Hazard

[?]

Sullivan

And a disc of ionized hydrogen to give the galactic plane, I suppose.

Hazard

Yes.

Sullivan

Well, first question I would ask is did this seem to you to really be a satisfactory model or were you satisfied with this?

Hazard

Well, reasonably so. I think it's still a ways from being reasonably right, but I think you've got to understand what the real motivation for that was. It was slightly different. It arose, that one, because there'd been, I think, [John "Jack" Hobart] Piddington had written some papers showing that the radiation across the galactic plane was the function of frequency.

Sullivan

Right.

Hazard

And I looked at it one day and it just struck me that it was, what he was plotting as to beam width. And so I played around a bit. I remember saying to Hanbury, "Look, all this is the beam width that’s just being produced here and the radiation across the plane could be a thin strip- it could be a line you're going to get the same answer."

Sullivan

Yes.

Hazard

And that was the first time that we realized I think, that he really realized, what was going on. That in fact, you couldn't restore these things. It was obviously all these restorations, you see, at that time when working and that really all you did was get back to the beam width, and once you were close to the beam width, there was nothing much you could do about it. And that the plot which he was working on were quite consistent with being a line distribution. And it was, we didn’t follow it up any further than we took it in that paper, which basically, I think, shows in the beginning that the narrow distribution can explain it all and that the rest of it is just beam width effects.

Sullivan

But how did you get around the spectral information? That was a big problem of course, to understand how the spectrum came about. You had ionized hydrogen in the disc and yet the spectrum of the disc radiation was not that of ionized hydrogen, I wouldn't think.

Hazard

But it is at the lower frequencies, you see, because what happened there was that that didn't really play any role until you got below 100 megahertz because it was quite narrow. And that didn't get any lower until you got below 100 megahertz, but in that paper what it'll say, I think, is that if you actually go down to about 30 megahertz, then what you will see is the dip in the galactic plane, which is what you...

Sullivan

The absorption, right.

Hazard

The absorption- which you do see, of course. And so that what you're expecting to see, and I think it says in that paper, possibly I can't remember, that you get these different behaviors depending on the aspect of the galaxy and depending on what frequency you're looking at. When you go to very high frequencies, you'll get the gas. You go to very low frequencies, then, if you're looking at it edge-on then you're looking at the absorption due to the gas starting to dominate. [?] the aspect dependent. Whether it is or not, I'm not quite sure, but in principle, that's right.

Sullivan

I gather that at that time you were not aware of the Russian work done on synchrotron radiation.

Hazard

Not really, no.

Sullivan

Did you know at all about [Hannes] Alfvén and [N.] Herlofsen and [Karl Otto] Kiepenheuer had suggested this mechanism?

Hazard

Not really, no.

Sullivan

Kiepenheuer suggested it for the galactic background.

Hazard

What date was that?

Sullivan

1950 in Phys. Rev. [Physical Review]. Just a short little article.

Hazard

No, nobody took much notice of it for several years after that. I mean, before it really as far as I can remember.

Sullivan

Except the Russians.

Hazard

Except the Russians, possibly, yes.

Sullivan

So apparently then you were not really worrying about keeping up with what they were doing- that was just a separate ball game?

Hazard

No, certainly I didn't, I don't think I knew anything about it at that time. I think so. I mean...

Sullivan

I think that's right. We can see if there's any...

Hazard

Certainly at that time there wasn't. What date is that one?

Sullivan

This is ‘53- it was submitted in June of ’53 and there are no references to any Russian papers.

Hazard

No.

Sullivan

Okay. However, now here, skipping to 1960, in Observatory you do argue with Hanbury-Brown that the disc of the Milky Way is synchrotron radiation coming from spiral arms.

Hazard

That's right.

Sullivan

So by that time you were embracing the synchrotron concept.

Hazard

That's right. I left 1954-57, I came back...

Sullivan

Yes, that was sort of a critical period.

Hazard

I found nothing had changed very much, as I can remember, not very much.

Sullivan

Really?

Hazard

I can't remember the...

Sullivan

Well, in terms of the adoption of synchrotron as an idea, perhaps.

Hazard

That's right. That changed. And what happened, I think, was I went back to work when the 250 foot came into operation and in the meantime I'd started to work on occultations, so that was...

Sullivan

Right, but you did look at M31 and M33 on the 250 foot?

Hazard

I looked at M31 and 33 and quite a stack of other ones.

Sullivan

Did that give you any new information about those galaxies?

Hazard

Oh...

Sullivan

Or was it just sort of a refinement of the previous...

Hazard

No, no, there was nothing known about them. I mean, [?] rubbish before, I mean, M33 hadn't been detected before, had it? Or did we detect it? No, we hadn't.

Sullivan

I guess that's right; you hadn't detected that one.

Hazard

Had we?

Sullivan

I don't think so.

Hazard

No, we hadn't, and neither had anybody else.

Sullivan

Yes.

Hazard

Although they said they had but that other indication was spurious of these galaxies.

Sullivan

From that 1C survey, especially.

Hazard

Yes, that's all spurious. They hadn't been detected before. So that we got M81, although to be quite fair we suspected M82 at the time. You know, we weren't, I remember at the time we weren't, but after a bit we were a little bit dubious because of position and so on. But for at least one or two points obviously, I mean certainly we made a real mess of the stuff in clusters of galaxies because, I mean, that was a thing I discovered one night when I was reading some book, probably [Edwin] Hubble, and I just worked out that we would get elliptical if we looked and integrated the radiation from a cluster, we could get the limit to the clusters that way, you see, elliptical by the limit to the radius from a cluster. And when we looked at several of them, there seemed to be sources there of course.

Sullivan

Right. This was back in ‘52 now. You had looked at eight clusters and detected two.

Hazard

That's right. And we should have, if we'd been on the ball and known any astronomy, we'd have realized what was going on in NGC 1275, I think. Except we didn't know any astronomy.

Sullivan

One of those was Perseus A.

Hazard

That's right.

Sullivan

I see.

Hazard

I think that if we'd really known any astronomy at all at that time, we'd have caught on to what was happening.

Sullivan

Yes. What about this business about comparison of radio magnitudes and optical magnitudes, that was something that you people pushed quite a bit?

Hazard

Well, we didn't, I don't think we pushed it very hard. What we did was at one particular time, I mean from the point of view of our particular work, it was rather convenient for us to express the optical things in terms of magnitudes for ordinary galaxies, which were comparable in fact to the optical magnetism when we knew what we were doing, and when the ratios were about the same so that we knew that if we took a tenth magnitude, we could detect it and a twelfth we couldn't, and a ninth we could.

Sullivan

Yes. Was this an attempt to help communication with the optical astronomers?

Hazard

Oh, I think it was probably out of just something about magnitudes. It was just to get things onto some reasonable scale; I don't think that the scales were determined. We were working at a single frequency and it was just a convenient way of expressing the things in time I think.

Sullivan

Yes.

Hazard

Then what we found out, of course, was that when we went to the clusters and so on that we'd got all the magnitudes wrong for ellipticals because everything seemed to be going wrong as we got fainter. I think we drew a line and I don't if we really interpreted it, but we should have spotted what was going on, of course, I think, and we didn't really at least draw the conclusions we should have drawn from it.

Sullivan

Which was?

Hazard

Which was that what was happening in these clusters was that these galaxies which weren't normal galaxies at the time.

Sullivan

Normal being defined as...

Hazard

Normal being the right ratio of the...

Sullivan

M31

Hazard

M31 and 51 that type of thing.

Sullivan

Even the ellipticals you thought might well obey that same.

Hazard

That's right, and we should have realized that there were things that were abnormally bright.

Sullivan

Well, it's easy in retrospect to say these things.

Hazard

That's right.

Sullivan

Well, when you came back, the big dish was just going on the air, I think. And you got involved in the lunar occultation work, which we talked about at some length, both there and at Parkes and at Arecibo, but it wasn't quite clear how you got the idea to do these lunar occultations. Do you remember that?

Hazard

Yes. What I can remember is- well, I think things partly started in conversations. We used to talk about how you could do positions and diameters and things like that. We used to talk about this all the time while building interferometers and so on. And I was walking over, I remember, with Hanbury- Brown [?] talking about these things and I think the occultation was mentioned. Now what I did after that was I went to work at, as far as I knew it hadn't been done, I don't think it was ever done in this way but I worked out exactly what you could do with occultations. That if you took the diffraction patterns and so on, because it had been used before just to, somebody looked at the Crab Nebula.

Sullivan

For positions.

Hazard

For positions, but in a crude sort of way, and what I did was that I worked out that with a steerable dish what you could do, using the lobe patterns, you could get angular sizes to better than a second or second of arc, and you get positions with that sort of accuracy.

Sullivan

Yes.

Hazard

And then I wrote a proposal to Lovell for time on the dish to do it. And so the arguments behind this were that you could do surveys with it. And again there'll be reports on this in the Reports to Observatories. I was doing this about 1957, I think. It took a long time to make it work. And the idea behind it was, I mean, what I said was that if you're going to get this sort of resolution, you have to build antennas miles across.

Sullivan

Otherwise.

Hazard

Otherwise, and I said that nobody was going to do that, when in fact they did, of course. They built the Mills Cross, which were pretty big things anyhow, but the argument was that they weren’t going to build these things to get these resolutions. And so that...

End of Tape 117B

[Tape 118A to faint to be transcribed (last 30 minutes of interview). Same topics are covered in Part 3 of interview (6/81)]

Modified on Tuesday, 29-Jan-2013 08:47:22 EST by Ellen Bouton, Archivist (Questions or feedback)