Interview with A. Edward Lilley

Description

Arthur Edward Lilley, 1928-2020. Interviewed 14 August 1979 at Harvard, length of interview: 60 minutes.

Creator

Papers of Woodruff T. Sullivan III

Rights

Contact Archivist for details. See Addresses Needed.

Type

Oral History

Interviewer

Sullivan, Woodruff T., III

Interviewee

Lilley, Arthur Edward

Location

Cambridge, MA

Original Format of Digital Item

Audio cassette tape

Duration

60 minutes

Interview Date

1979-08-14

Notes

The interview listed below was originally transcribed as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009). In preparing Sullivan interviews for Web publication, the NRAO/AUI Archives has made a concerted effort to obtain release forms from interviewees or from their heirs or next of kin. In the case of this interview, we have been unable to find anyone to sign a release. In accordance with our open access policy, we are posting the interview. If you suspect alleged copyright infringement on our site, please email archivist@nrao.edu. Upon request, we will remove material from public view while we address a rights issue. Please contact us if you are able to supply any contact information for Lilley or his heirs/next of kin. Places where we are uncertain about what was said are indicated either with the possible wording in brackets or with parentheses and question mark (?).

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 some Sullivan interviews to the Web in 2012-2013.

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.

Series

Working Files Series

Unit

Individuals Unit

Transcription

Transcribed by TranscribeMe (2018), reviewed and corrected by Ellen N. Bouton (2019).

Begin Tape 122B

Sullivan

And this is now talking with Professor Ed Lilley at Harvard Observatory on 14 August 1979. Well, to start off can you tell me what your educational background was and how you first came in contact with astronomy and then with radio astronomy.

Lilley

Well, I had a -- standby [brief interruption]. I had a BS and an MS in physics from the University of Alabama and the destiny would have been Chicago and physics but Donald Menzel arrived on the scene to dedicate a new physics building for the Alabama Physics Department and I became interested in, from his talk on that occasion, became interested in radio astronomy which he outlined and ultimately visited him here in Cambridge. He became interested in a little effort we had undertaken in Tuscaloosa when the mayor of Birmingham wanted to seal the cornerstone of the new city hall with light that left a star at the time Birmingham was founded. [laughter]

Sullivan

Those are beautiful.

Lilley

This request went from the mayor of Birmingham to the president of the University of Alabama to the chairman of the physics department to the electronics professor, Fred Mitchell, to his graduate student who was me, and I got the task of doing this and we had a 15-inch reflector telescope as part of this new building which Menzel came down to dedicate it. We arranged the photocell and once we got a relay to close, we were home free but to give it local color we soaked a cotton ball in ether and put it in the gap of a Tesla coil and that produced - [laughter]

Sullivan

Those are great. So you find the right star that was 100 light years away.

Lilley

Yeah, Arcturus was about 80 light years away which was what we wanted but it was fast disappearing in the west.

Sullivan

It gave you a nice signal of noise also.

Lilley

Oh yeah. So we had to keep the light going for the dedication ceremony, which came a month or two later, [in a lantern?] which another graduate student had the assignment of keeping [full of water?] Oh that's the way I -

Sullivan

This fellow Mitchell that you mentioned. Is he the one who did some millimeter work later on?

Lilley

Yeah. F.H. Mitchell.

Sullivan

I've never talked to him. Is he still alive?

Lilley

Yes, yes he's at the University of South Alabama. He used to be at Alabama. He taught at West Point. I think he's written a couple of textbooks on physics. He's a very interesting fellow.

Sullivan

And what about there was a colleague named Whitehurst?

Lilley

Whitehurst, yeah. Whitehurst.

Sullivan

He is still at?

Lilley

He spent some time at NRAO.

Sullivan

Was he the fellow that's worked with Mort Roberts on a couple papers? Maybe [inaudible]?

Lilley

Well, my knowledge of him as NRAO is like 15 years ago.

Sullivan

Oh, I see. But there is the guy from Alabama that's been working with Mort named Whitehurst. I can't remember the initials.

Lilley

Well, the age of the Whitehurst I have in mind would be 60 or so.

Sullivan

Yeah, I've never met him.

Lilley

I don't know.

Sullivan

Okay. I haven't gotten to them yet. So anyway, you came to Harvard then in astronomy rather than Chicago in physics.

Lilley

Yeah, and in the same class with Dave Heeschen and some others that from that era, and on arrival here the hydrogen line adjustment was discovered by Ewen and Purcell. The talks and colloquia attendant to that were of great interest to us. And so the enthusiasm for that particular program was a natural.

Sullivan

Now so it was more or less your own initiative to get involved in this. It wasn't Bok coming around stirring up interest?

Lilley

No, we went to the - the best I can recall there was a colloquium given one evening by Purcell one evening, at Jefferson I guess, in the physics department. I got very much interested in that and I forget, the details are vague, but ultimately both Heeschen and I ended up working with Doc [Ewen] and with Purcell with the horn and the other equipment that had been assembled on the second or third floor of Lyman Hall.

Sullivan

More or less learning the ropes of how to use it?

Lilley

Oh sure. I think our intent was to take the equipment to Agassiz Station ultimately and put the horn on an equatorial mount and attempt to survey the galaxy. And of course, the incident which stands out vividly is that for one reason or another the equipment vanished over one weekend and the problem locally became how could this field of research be pursued?

Sullivan

So you knew nothing about this, and all of a sudden it was gone -

Lilley

No, we weren't privy to the political decisions.

Sullivan

So I suppose also you're probably not involved too much in the matter of how could we pursue it here, that is was more the matter of getting more funds and so forth -

Lilley

Well, we were aware that there were possibilities, we kept hearing about the anonymous lady at Harvard who of course was Mrs. Agassiz. We knew that was a possibility. We were aware of the early formation of the National Science Foundation. So I'm reasonably certain that our intent when we came to see Shapley was to promote some enterprise to generate money to restore the loss we had suffered.

Sullivan

And you say when "we" came to see Shapley, who was that?

Lilley

That was Dave Heeschen and myself.

Sullivan

And what was your request to him?

Lilley

Well, our request - well, we notified him of what we regarded as a significant loss and asked him to do something about it, and he did.

Sullivan

And were you asking for a specific dish, or did you want a horn to replace the one - or you just wanted -

Lilley

Well, I don't recall the specifics and the memorandum but, although it's - I think it's around somewhere to find -

Sullivan

Well, presumably it's in his archives, I don't know.

Lilley

Well, there may be a copy here in this office still. The net result is that he raised money from Mrs. Agassiz, which was used as matching funds with a proposal which Dave and I participated in the writing. I believe Bok would have been the principal investigator, conceivably Ewen was the co-investigator, I don't recall. But the proposal number I do recall and it was in the 200s. You know, it was something like the - it was one of the very early proposals that went to NSF.

Sullivan

Right. And this proposal was successful?

Lilley

It led to the 24-foot antenna at Agassiz, equatorially mounted, hydraulics, rack and pin, several driven gear, on the polar axis, a real kluge of a system.

Sullivan

And was that bought off the shelf from some company or was that -

Lilley

No, no. The engineer assigned to that from the DS Kennedy company was Robert Grimsback. And in a way, between his knowledge of what Kennedy could do and our description of what we needed, he formulated the design in his study in Winchester. We went to see him at night and outlined what we needed and the design evolved in his study and was made by the DS Kennedy company.

Sullivan

I see so that was the first of many Kennedy radio telescopes -

Lilley

Yeah.

Sullivan

Well, how long did it take to get this thing operating and what about the receiver also, what were you going to do for that?

Lilley

Well, my guess, it was late '51 or maybe early '52 when the enterprise got underway, and it must have taken a year and a half or maybe longer to bring the equipment to Agassiz and assemble it there. In parallel with that, Ewen had formed the Ewen Knight Company, and I think he also formed the Ewen Dae Company -

Sullivan

Right. You told me about [crosstalk] -

Lilley

[crosstalk] day and night and those early tales. And the equipment, the electronic equipment was built over the Honeybee Cafe in Central Square where Ewen had his early company floorspace. Best of my recollection, Heeschen and I, along with Jack Campbell and other names that I don't recall at the moment, went down there in the evenings and worked as technicians and solder jockeys, assembling the electronics. And ultimately, after the integration of the system at Agassiz, then Dave and I after the early shakedown phase, operated it 24 hours a day, 12 hours each, on and off.

Sullivan

Grueling -

Lilley

Seven days a week, for quite a while.

Sullivan

Now, how was it decided what you were going to work on? Where did the ideas come from as to what to do with this?

Lilley

Well, the ideas came from discussions with Bok. A lot of influence from Bok. Dave and I, as I recall, developed our own ideas, which certainly were part of it. But I believe if we were privy to go back and oversee those discussions in those days, if they had been recorded on videotape, I suspect that Bok was clearly the dominant influence. In fact, the assigning of the regions of the sky to Heeschen and to myself, Bok apparently gave considerable thought to, because it was done on a selected area basis, and selected areas were handed out to me in the anti-center and to Heeschen in the center. And conceivably, Bok already knew there would be a long string of graduate students and he could probably [laughter] divide up--

Sullivan

[inaudible] 21 centimeters.

Lilley

[inaudible] for a long time if you divided it up finely enough [laughter].

Sullivan

And so the idea was to just do a survey in more or less random location in the galactic plane and find out what was going on in a small area, was -

Lilley

Well - Or -? That's my recollection. That one would examine the spectrum of hydrogen from that region, or the spectra from that region, and then determine as much as one could about galactic structure in that particular direction. And bear in mind, we were aware that the Dutch were surveying the galactic plane at the same time.

Sullivan

1Right. So you were not trying to do a grand survey like that?

Lilley

In fact, Walter Baade came by during this period and in effect told Heeschen we were wasting our time because the Dutch had all of the observations that would be of use in this one-shot field, and they were now in the process of reduction. So we were, in effect, wasting our time [laughter].

Sullivan

Amazing. Now, your thesis came out in '54 and in the introduction to it, anyway, the whole thrust is that you going to study a dust cloud and find out what was going on there, but it seems like this may have been a little bit later on that you reasoned, "Well, okay, what's going on in the anti-center and what can I make of this astrophysically?" So you've changed it from a random location to a more physical sort of thing, is that correct?

Lilley

Well, I think in the anti-center, as I recall, the gas fell off quite rapidly north of the plane. And south of the plane in the Taurus dust complex it held up with latitude rather strongly. And it seemed fairly clear that the outstanding difference between the north and south portions of the plane was the huge dust complex south of the plane. So in order to test that we then went parallel to the plane about 15 degrees as I recall, through several other heavy regions of dust including Perseus and Orion, and in each instance a large of amount dust seemed to correlate very well with enhanced or sustained emission from the hydrogen.

Sullivan

Can you give me some idea of what it was like to observe at Agassiz at that time? What was the standard procedure?

Lilley

I think I was living in a misnomer called the summer palace which was a 1930s plywood pre-fab. Heeschen was living in the Agassiz cottage, which was slightly higher class accommodation. We worked 12 hours a day each, and passed each other, as it were, on the change of shift, and it was mostly setting the local oscillator, arriving for a shift for 12 hours, thermos bottle and sandwiches. Was a log of the positions to be observed. Setting the local oscillator where you needed it for the particular region of the sky. Setting up the coordinates which meant in right ascension operating this hydraulic system which tended to leak and clunk. And carrying on like that for 12 hours, and then stumbling back to reduce data and go to bed.

Sullivan

Now this was a single channel system, was it not? Were you tuning yellow to get the whole - ?

Lilley

The yellow scan and a signal channel and a [inaudible] channel, the [Paris?] channel being separated far enough so that it was not moved through the emission, and the difference of those two channels was the quantity displayed.

Sullivan

And then of course you had all the reduction to do on the script chart recordings.

Lilley

Oh, sure.

Sullivan

So what would you say was the main result from your thesis?

Lilley

The regions of interest were characterized by lots of dust and I think switching to looking at it from the zone of avoidance enabled a calculation of the total quantity of dust, and there seemed to be a very good correlation between the total extinction in the direction and of the number of hydrogen atoms, with an average quantity of about 100 to 1 for the mass density ratio of hydrogen to dust.

Sullivan

So there was a lot of gas in these clouds which was not uniformly known at that time or accepted.

Lilley

Yeah.

Sullivan

Were you thinking at all about the possibility of molecular hydrogen? What [component?] that might be or is it - ?

Lilley

I suppose it was discussed. I don't recall specifically. I don't think it was included in any of the papers written at that time.

Sullivan

Yeah, I didn't see it in your thesis at all.

Lilley

I think molecular hydrogen may have been discussed but it certainly wasn't written down. And there was no apparent way of finding it.

Sullivan

Okay. So having gotten your degree, then what was the next step?

Lilley

NRL. In fact, Fred Whipple suggested NRL because of the presence of the 50 foot antenna coming online and thought that would be a good place to be, and as it turned out it was.

Sullivan

And so what did you find in the way of a group and what was going on when you got down there?

Lilley

Well, the principle characters I recall in the group were John Hagen, Ed McClain, Fred Haddock, and Cornell Mayer. Also, Ben Yaplee, and perhaps others I would [inaudible]. But those were the fellows. The main impression of the first days was that the apparent discovery of hydrogen absorption by Hagen and McClain, which was an intriguing concept, in fact -

End Tape 122B

Begin Tape 123A

Sullivan

Lilley on 14 August 1979. So we were talking about H1 absorption, you said they had discovered this phenomenon.

Lilley

When I arrived at NRL the phenomenon had been discovered and as I found out later in my notebook, that I kept at the time of my thesis, Fred Whipple had suggested to me that it might be interesting to look in the direction of discrete sources and observe the spectrum of hydrogen in those directions. And pretty clearly what Fred had it in mind was the analogy between that configuration and interstellar absorption lines in the specter of stars. Now, in the case of hydrogen, I believe the technique that Hagen and McClain had used was to tune the particular frequency with these single-channel systems we were discussing earlier tuned to the peak of the hydrogen line, and point the antenna adjacent to the discrete source, which as I recall was Taurus A. Then while tracking the peak of the hydrogen line, swing the antenna beam through the discrete source and when they did this they found that the peak intensity of the hydrogen line went through a null coincident with the position of the discrete source. Apparently, they had not considered or had not yet obtained the spectrum, in the direction of the source.

One evening that I vividly recall, McClain and I had an opportunity to do this. We set up the 50-foot antenna pointed toward the discrete source Cassiopeia A, and started scanning in frequency and I vividly recall McClain kicking the radiometer that Ewen had sold to the Naval Research Laboratory because the old chart recorder was quite literally banging from one limit of the scale to the other. And we had to reduce the gain on the recorder to get to the spectrum on a scale. And for hours that evening, we scanned back and forth the spectrum of Cas A watching these three huge absorption lines come and go repeatedly. It became clear that evening that Cas A was beyond the second spiral arm and we knew that the Baade-Minkowski result of 500 parsecs was off at least by a factor of six and possibly more.

Sullivan

Are you saying right from the first time you observed it you already had it in your mind this interpretation of distances and so on?

Lilley

Well, we knew that if the absorption occurred in the-- by the time McClain and I were observing that weekend, I believe we had had sufficient discussions -

Sullivan

I see. Okay.

Lilley

- to be at ease with the idea that absorption of the continuum from the discrete source was probably the responsible agent.

Sullivan

And you had thought about the idea of using it as a distance indicator, also?

Lilley

Oh. Sure. Yeah. But whatever tentative thoughts we may have had were certainly galvanized that evening. Because it was clear that there was a lot of gas between us and Cas A.

Sullivan

Were you influenced at all by the Davies and Williams paper, about the same time, suggesting this as a distance method? Do you remember the Nature short paper?

Lilley

I remember the paper. The timing, I don't recall.

Sullivan

'54 is the date of that.

Lilley

Yeah. So I don't recall.

Sullivan

Okay.

Lilley

The problem became how to write it down. How to write down what was going on. That possessed me for a while. I couldn't get that out of my mind and knew that while getting the distance was interesting, and the impact on the distance to Cas A, in particular, was considerable interest in the astronomical community, the lingering problem was to attempt to write down the -

Sullivan

The equation of transfer -

Lilley

The radiative-transfer considerations. And I first tried using the cloud model. And it went into a NRL report. A copy of that report went to Ed Purcell who was travelling frequently to Washington and came by to see me at NRL. And he explained to me that all of the Omega's that we were using to write it down, the Omega-I's and the Omega-J's, had kept him up one full evening. And he drew a three-dimensional diagram on the blackboard. He said he thought that if he understood all of the Omegas, he could probably draw it. You know how Ed is in reducing everything to startling simplicity.

Sullivan

These were beam-celled angles, and cloud-celled angles.

Lilley

And solid angles for the absorbing clouds, and of course you have [inaudible] opacity of the cloud, the angular size of the discrete source, the beam, and on and on. But [he reduced?] space to an angular one-dimension amplitude for another coordinate of both the - to represent both the continuum and the emission cloud and frequency [inaudible]. So on this configuration of the discrete source looked like a wall. Continuance in frequency rising in intensity to a peak, and then disappearing in angle.

Sullivan

Right.

Lilley

So it was really a wall, and hydrogen clouds being monochromatic occupied only a finite width on the frequency scale, were much weaker in intensity than the discrete source in terms of brightness temperature. And if they happened to lie in front of the discrete source and were opaque, they would cut a notch in the wall [crosstalk].

Sullivan

It was just a difference between the [inaudible] temperatures.

Lilley

Right. And so we liked that diagram very much and had it drawn up at the NRL art department that made up that sort of thing. And it got passed around quite a bit. We mailed it back to Bok here at Harvard, who rolled it out on the floor one evening in Agassiz Station, and asked all of the students, he told me, to explain it [laughter]. So those were the early days.

Sullivan

So in the Hagen, Lilley, & McClain '55 ApJ paper that went through all the theories, primarily your contribution was the theoretical interpretation of all this equation of transfer and so forth?

Lilley

Well, yeah. I spent a lot of time on that, and tried it out on everyone I could find at NRL, Haddock, Mayer, a physicist named [Amit?] who may or may not still be there.

Sullivan

You haven't explicitly mentioned the business about - in the first paper by Hagen, they claim themselves that it appears that what they're saying is they thought the continuum source was actually blocking the hydrogen. Is this a fair statement?

Lilley

That seemed to be the impression when I arrived, and I think that's the impression you got from the first brief paper. But those were lively days, and the transition from that concept over to the one that we finally published occupied a a lot of hours of discussion and trial-and-error at NRL.

Sullivan

Sure. Well, it's easy to look back now and say, "Well, how could they have thought that?" but -

Lilley

I do remember Purcell's general comment about the complications of the cloud model putting everything in terms of small, solid angles, and attempting in a way to use a summation procedure to write down the equation of transfer. And in those days, we were traveling a bit for the Navy, and McClain and I went on a trip to West Virginia to look at a site which I believe was Sugar Grove?

Sullivan

Mm-hmm.

Lilley

Sugar Grove. And somewhere in my file is the stationery from some motel where McClain and I stayed, and being unable to sleep one night, I got up early the next morning, 4 or 5 AM and started an attempt to write down the transfer consideration the way it should have been written down in the first place. [laughter] And I finally got that right, which is on the tail end of the article.

Sullivan

I see. [I can add it on there?] Well, okay. Continuing NRL, you had another paper in ApJ in which you talked about the idea of using a big dish in the - looking for absorption was more a sensitive method than detecting lines, and so you obviously were thinking about other line possibilities. Can you tell me how that went?

Lilley

Well, of course, we all discussed after hydrogen what's next? And we all were considering various ways to increase the sensitivity of the system. Now, it turns out that that particular suggestion of looking at absorption against discreet sources is - that it does not account for the increase in the - noise, but on the other hand, that's always been a - and we knew that, and had always been some debate about isn't it easier to look for a big signal than a weak signal, and both of them in the presence of comparable noise. And well, you have to decide for yourself on that one.

Sullivan

Right. Right. But what lines were you thinking about at that time? And then I know that you actually did under - do a search for OH with Al Barrett.

Lilley

Well, I'd have to go back and look at the paper. I suspect if we - that we were aware at least of the OH - OH lines. The papers by Townes and Shklovskii, they hadn't mentioned CH, [inaudible] OH -

Sullivan

[inaudible] the main thing, but also CH was mentioned, and the water vapor line is mentioned by Townes.

Lilley

And most of us in those days were in close touch with Townes. In fact, I made a number of trips to Columbia. Gave some early colloquia there. Those lines undoubtedly must have been in mind. And in those days, about, well, I don't recall the timing exactly, but Al Barret did show as a new employee, I'm not sure whether for one year or longer.

Sullivan

Yeah, I think he had an appointment, or fellowship, or something for a year or something.

Lilley

Yup, and I do recall that we worked out the OH problem on the blackboard, and the reason I recall it so vividly is that he taught me about the physics of OH and I taught him about the observational situation between here and Cas A. We combined those things and on the blackboard because the photographs happened to be taken at the time. There's a prediction of the opacity in the direction of the Cas A.

Sullivan

That's the strongest component.

Lilley

And on the photograph, it says 0.16. And in the paper that Merrit participated in some years later, the published opacity is 0.16.

Sullivan

This is about 10 years later actually or [inaudible].

Lilley

Well, yeah, it was some time later.

Sullivan

Yeah. Is this an official NRL photograph that was taken?

Lilley

Oh, that's around in the files here somewhere. I suppose it was, yeah.

Sullivan

I would like to see a copy of that.

Lilley

But there weren't any cameras around the NRL.

Sullivan

Oh, that's right. They'd have to be official, right at NRL.

Lilley

Right, they would have to.

Sullivan

Paul, hold on second. I'll see if I can--.

Lilley

Okay.

Sullivan

So, you then apparently said well, let's go out and try to find this OH line.

Lilley

Yeah, Al and I looked for OH. I suppose this was in '56. I suppose we looked at - . We didn't know the frequency precisely then so it was a bit of a chore. I'm reasonably certain we looked at Cas A. I think a comet came through at about the same time and we took a quick look at the comet.

Sullivan

For the OH line?

Lilley

For the OH line. I suppose in retrospect if we had looked at the galactic center, we would have found it from what we know now about the skies of the line.

Sullivan

Yeah, I've looked at that report. I think the frequency was off.

Lilley

Right.

Sullivan

And I can't remember now if it crossed at some point or whether it was just the center of your search was way off and I can't remember. But that certainly was the first search for OH that I know about anyway. Well, you went into an NRL report. I was just wondering why you didn't publish in the standard astronomical literature.

Lilley

I would have thought we did as an abstract anyway when they -

Sullivan

Well, it was an abstract, oh yes, an AJ meeting, an AAS meeting.

Lilley

They probably didn't think it was more than that [inaudible] limit.

Sullivan

Were there any other searchers that were done for other lines at that time?

Lilley

I don't recall. I had an interest all along in lines. I gave a colloquium here on other lines when I was a student and had a chapter in my thesis on other lines including carbon monoxide which Bok convinced me it would be prudent to remove that chapter.

Sullivan

Oh, this is in your draft.

Lilley

[inaudible] book. Oh yeah, I'm sorry. Yes, in the draft. He [inaudible] removed that because of its speculative qualities.

Sullivan

I see. Okay, now also while at NRL, you and Ed McClain apparently decided to look for hydrogen in Cygnus A. Now, was your idea just to look for absorption like you had done in Cas and Taurus or were you thinking about looking for emission?

Lilley

Well, I think we must have been influenced by the absorption history and undoubtedly expected to see absorption. We looked, and we looked over a fairly substantial frequency range, looking I suppose for narrow features, again, being influenced Cas A and [Sona?].

Sullivan

But were you looking at zero kilometers a second range, I mean galactic range for these absorption features or were you looking - ?

Lilley

Well, in the beginning, we looked at, well, we, of course, included Cas A in the local survey. I mean, Cygnus A in the local survey.

Sullivan

Oh, okay.

Lilley

And we looked for that. Then, I believe, Baade and Minkowski, I believe those were the people that worked on the [inaudible].

Sullivan

Right, they measured the redshifts -

Lilley

They measured the redshifts. We used the redshift and then the thought might be hydrogen in the vicinity of the source and looked for that.

Sullivan

Oh, okay.

Sullivan

We thought, I suppose, we were going to find narrow lines. Never did. We then saw what looked to be like a gentle and broad absorption line at about the right frequency. The possibility of baseline effects was very much on our mind and we used another discreet source - I'm not sure which one - and took the ratio of Cas A, of Cygnus A to that other discreet source. And even that ratio showed a gentle absorption line of considerable breadth. And we presumed that was the absorption source and published it. It turned out later when we, I think it was Davies who's tried at Jodrell Bank and we again tried it at Maryland Point with the 84.

Sullivan

84 foot, yeah.

Lilley

And no one was able to reproduce that. And to this day, I don't know what in the ratio of the two antenna temperatures could have caused that problem but we gave the data to a number of other people at NRL blindly and asked them to -

Sullivan

Well, as you know, these things still happen today.

Lilley

Oh, sure. And I suppose if we had to do it all over again, we'd do it exactly the way we did.

Sullivan

Was there any trouble in operating so far away from 1420 line interference or in tuning the receiver in [inaudible]?

Lilley

No. No interference that I recall and the system locked alright. [inaudible] figure me measured out to be essentially the same.

Sullivan

Were you still tuning at single channel?

Lilley

Well, we were using the broad channel. We weren't tuning at all. We were actually measuring the antennae temperature at a specific frequency for two sources and reduced, and taking the ratio as a measure, the ratio of the two antennae temperatures as the measure of the ratio of the flux for the two objects which should be invariant across the spectrum over a small range. And that resulting plot could be interpreted as a reduction in the flux coming from Cygnus A at the right frequency.

Sullivan

Okay, were there any other projects you worked on at NRL?

Lilley

There were. In those days, you spent some fraction of your time on NRL objectives, and the remainder on pure research. And what we've been talking about was the pure research side. I did work on some other programs which occupied an awful lot of our time. One was radar returns from [C state?] conditions. These were experiments carried out from the bridge over the river down on what is it, 301 that's south of -

Sullivan

Oh, yes. Yes.

Lilley

They say there's a huge bridge down there, the name of which now escapes me.

Sullivan

You mean the one that's a mile south of NRL or the one that's way down south?

Lilley

Way down. Way, way, down.

Sullivan

Yeah. I know the one you mean. I can't remember the name either.

Lilley

And we used to have a system set up hanging over that and measuring. It was a good fetch across that water and you can get a variety of [C states?] right there. Then another one we worked on was Doppler radar as an airspeed indicator for devices to give the landing signal officer on an aircraft carrier the landing speed of planes coming into land. As I recall, this was the early days of jets attempting to land on carriers and had some trouble judging the critical speed. And I suppose it was researched at that time both at NRL and elsewhere that led to the day-to-day radar speed traps that we enjoy now.

Sullivan

Sure. And you also mentioned that you looked a sight for what became Sugar Grove.

Lilley

Yeah. The Sugar Grove program was coincident with me - the beginnings of it were coincident with my stay at NRL. McClain and I went on a number of occasions to the hills of Virginia and West Virginia looking for a suitable site.

Sullivan

And was the initial purpose of Sugar Grove, indeed, the big dish or was -

Lilley

Yes. The initial purpose was the 600-foot antenna that was ultimately terminated by the Secretary of Defense.

Sullivan

Right. I talked to him and others about that. You weren't directly involved in that too, except for the site survey?

Lilley

No. Only in the site survey. And towards the end, as I recall, we were directly involved when NRL, I believe, decided that after all it might be a good idea to include the basic research justification. And I suppose that this was a downhill, last-ditch fight to salvage the antennae. And we did work for long hours producing basic research justifications for the 600-foot antenna. And I presume those documents have vanished.

Sullivan

This was while you were at NRL or this is later?

Lilley

No. I believe this is while I was in NRL. In fact, I'm sure it was.

Sullivan

And so you left NRL in '57, you were saying?

Lilley

I think that's right.

Sullivan

And then went off to -

Lilley

The immediate cause of relocation was the emergence of Project Vanguard. I was returning from a trip to Europe with John Hagen. And it was on this trip that Hagen was named the head of Project Vanguard. And there was, I believe, a considerable reorganization at NRL at that time. And Hagen was going to head up what then became Project Vanguard and I thought that over and decided that was the time to go to Yale, and did.

Sullivan

And now in the period '57 to [inaudible], I really don't see many publications dealing with radio astronomy anyway. So was this a quiet period at Yale in terms of research? Or--

Lilley

Well, it was a period when -

Sullivan

What was your goal?

Lilley

The goal at Yale was to begin raising funds to - at that time, I think, a number of us still thought that universities would be strong centers of radio astronomy. It was even later that we got to the thought of regional facilities as a fallback from strong institutions. But my purpose was to go to Yale and to build up a program at Yale in radio astronomy. And these early years were very much involved in writing proposals, raising money, and getting the enterprise underway. And there were no facilities at Yale at that time. I think I did, at that time, go back occasionally to NRL and work with McClain on some experiments. I guess that was the time when we began [inaudible] trying to reproduce the results on [inaudible].

Sullivan

Yeah. Now was Brouwer the head at Yale [crosstalk]?

Lilley

Brouwer was then the director at Yale.

Sullivan

So he must have wanted to get radio astronomy going.

Lilley

He wanted to get radio astronomy going. But perhaps even more so, Harlan Smith wanted to get it going. And Harlan was instrumental in attracting me to Yale. And we worked together a bit during those years to try to get it going. Harlan, being interested very much in the Jupiter situation, helped bring the equipment to Yale. And Douglas was a student in those days.

Sullivan

Yeah. I've talked to Harlan about that. But I didn't actually realize - you weren't involved directly in the Jupiter stuff, weren't you?

Lilley

No, no. He had, as I say, an independent undertaking.

Sullivan

So what was your - what kind of program did you want to get going then?

Lilley

Well, again with the help of NRL, I arranged to have a Würzburg 24-foot antenna moved to the Yale Observatory out in - where is it? Bethany. So at the time, I suddenly decided to come to Harvard, do a change of situations here. We had just moved to the Yale Observatory a 24-foot Würzburg antenna that I had talked the management at NRL into donating for the sake of education and research, this instrument they had, to Yale. I presume, had I stayed, this would have been the first instrument at Yale. An equatorially-mounted 24-footer Würzburg for hydrogen - as I recall, [inaudible] and I were interested in solar parallax at that time. And I'm not sure what else. But that would have the way things might have developed at Yale.

Sullivan

But in any case, this really never got used for anything. I've never heard of any results that came from it.

Lilley

No, the antenna title had been transferred to Yale, and I had it delivered. And the mounting was delivered. Site was selected, and I believe the foundation went in. But I believe that nothing further was done with that at all after I left.

Sullivan

And then you came to Harvard.

Lilley

Tom Gold had just left Harvard. And again, Donald Menzel, who had crossed my path years earlier as a student, was instrumental in inviting me up one weekend and asking me, would I consider coming? And that was a bit of a problem, because I had indeed succeeded in raising some money for Yale. And the question became, could I preserve that momentum and transfer those funds from Yale to Harvard? And after a bit of enterprise, the answer was yes.

Sullivan

Yeah, and now was this to be head of the radio group?

Lilley

Yeah, in the sense that it had a head and was only, I think - head in the sense that one was then the principal investigator for the grant that made radio astronomy a [inaudible]. Those were the days of the first masers at Harvard for hydrogen line research. I believe Eugene Epstein was one of the early students.

Sullivan

And Mort Roberts is also here then, I think?

Lilley

Mort Roberts came a bit later.

Sullivan

And the thrust, it seems - so the research shifted from galactic work to external galaxies?

Lilley

With the masers, it became feasible to do the extra-galactic hydrogen work. And both Epstein and Mort Roberts pursued that vigorously.

Sullivan

Now, it seems like from your publications up through '62 where my bibliography ends, that your own interests, however, were more in space radio astronomy and the prospect for that. Is that correct?

Lilley

Well, my own personal interests certainly went in that direction, although, there were a number of responsibilities still with the hydrogen program. Getting the masers to work reliability, as I recall, was a - we never quite trusted the single spectrum on the extra-galactic nebulae in the beginning. In fact, the reliability of the hydrogen data, I think, was my major concern. It was certainly the major concern that Menzel had. It was the only point that he discussed with me with great care. It was clear that Harvard was extremely sensitive about the quality and accuracy of the data. And in those days, I spent an awful lot of time worrying about specifically that. Nevermind the interpretation that Epstein and Roberts might have placed upon the spectra later, but would they hold up?

Sullivan

Were the bumps real? Yeah.

Lilley

Were they real? But, as you said, my own taste went into, I believe at that time, millimeter observations from the Mariner probe to see whether Venus had limb brightening or limb darkening as the ionospheric or hot surface model would have predicted.

Sullivan

So Mariner 2, I believe?

Lilley

Yeah, Mariner 1 was destroyed by [inaudible] safety officer. Mariner 2 made it all the way.

Sullivan

And those really are the first microwave observations done from space, I think. Is that a fair statement?

Lilley

That was the first probe to another planet, and I believe those were the first -

Lilley

What was the main scientific - the results to come out of that?

Sullivan

Well, I believe it settled the question of limb brightening or limb darkening. It was clearly a case of limb darkening. I believe it eliminated the possibility that Venus could be the meteorological twin of the Earth, having a comfortable environment as a place to go in the future in the space program. It was clearly a hostile environment because the temperature originated at the surface. Due to the limb darkening and the measurement, it has held up. It is, indeed, there 700 or 800 degrees Fahrenheit.

Sullivan

Right, was the point that if there was limb brightening that it might be an ionospheric contribution to the temperature?

Lilley

That's right. Right, the competitive model at that time was, to the hot surface model, was an ionosphere with a cool surface, something like the Earth. And the spectrum of Venus on wavelengths, which showed 600 degrees, was in fact, not showing on the surface. But showing an ionosphere [inaudible] to Venus. And that model predicted them brightening, whereas, the observation showed [inaudible] dark [inaudible].

Sullivan

Let me just go back to the reliability of the H1 measurements. During the period, not precisely, when you were gone, namely '55 to '60, there were some overinterpretations of bumps and so forth, which I've talked to various people about. Is this what you were reacting against? Essentially, that a reputation developed for overinterpretation, shall we say?

Lilley

Well, I think it wasn't as much overinterpretation as it was the reality or the accuracy of the spectra produced here in those days. My impression is that the thought of, after the very early days, Ewen and Purcell and then the 24 foot very first year or two, the scope and the diversity of the program and hydrogen line research at Harvard expanded tremendously. And conceivably, there was not as much attention to the quality of the spectra, and perhaps, stimulated by the excitement of interpretation, there wasn't as much conservatism in the quality control of the data and the checking as there might have been. Clearly, that was what was on Menzel's mind when he asked me to come, and in effect, our major concern is the quality of the data. The interpretations may come and go, but at least the spectrum should survive the test of time.

Sullivan

What about the factor that - Ewen was providing these receivers, not a member of the Harvard staff. I guess he maybe was officially, but anyway, he wasn't here very much. Then, you had these graduate students using the equipment. It's a very different situation than all other radio astronomy at that time, which was done by people building their own receivers and putting them on the antennas and doing it themselves. Do you think that may have been a contributing thing, that radio astronomy was as it actually is now in national observatories, more of a black box approach?

Lilley

Well, it's a black box approach now. I don't think you can - I mean, my opinion for that split where Ewen was providing me equipment commercially to students and staff members who then used it here, I don't think that eliminates the responsibility of the people who use the equipment from - it doesn't eliminate the responsibility nor does it allow them to transfer the discredit, if you will, back to the manufacturer.

Sullivan

Still, you're saying the calibration, the checks, the reproducibility and so forth can be done [inaudible]?

Lilley

I think it was very early in the hydrogen explosion of papers, and the enthusiasm was more in the interpretation than in the quality of the data. An awful lot came out in a hurry, and some of it didn't survive the test of time. And it was an awkward period.

Sullivan

Let me ask, finally, about your interest in low-frequency satellite astronomy. You said that Dick [inaudible] was the main person, actually, but can you just briefly tell me what you were doing around 1960 along those lines?

Lilley

Well, it's hard to recall clearly, but my impression is that, in the early days, Dick and I discussed the possibilities of low-frequency radio astronomy getting the sensors above the atmosphere. I also recall he was, at that time, a member of the Society of - he was a Junior Fellow in the Society of Fellows at Harvard, which gives a student or Junior Fellow a considerable academic license. So, in effect, in our discussions, we outlined the possibilities that might develop if one could put low-frequency sensors into space. Dick, then, made this one of his main objectives and looked at the problems theoretically and worked out an awful lot of models and also considered the development of the equipment. And his thesis is really a massive effort in outlining the potential of low-frequency radio astronomy, some of which I suspect is yet to be realized.

Sullivan

And you say he actually did get a couple antennas piggyback on some military satellites?

Lilley

He did.

Sullivan

And did any useful observations come from these?

Lilley

I think the nature of the rides, second-class occupancy if you will, and the intermittent performance of the equipment - because, in effect, he had power only at the discretion of the military, and telemetry wasn't all that it might have been. I suspect those early flights were essentially written off.

Sullivan

Well, as you look back over the whole sweep of it, from when you entered the field through the early '60s in radio astronomy, any comments that you'd like to make about how it developed or how it's influenced astronomy as a whole?

Lilley

The only thing that clearly stands out in my mind is the danger of presuming, when you're dealing with a new instrument, that you have some understanding of what likely is to happen. My main impression of those days is something of opening Pandora's Box, and I suspect this is still true, whether it's a new x-ray observatory in space as we have today or of some sensor that might be developed in the future. I think our knowledge of the inventory, if you will, of objects and processes in the universe and the various manifestations they may have now and in the future, I suspect we only have a very dim idea of what that is.

Sullivan

Okay, thank you very much. That ends the interview with Ed Lilley on 14 August '79.

End Tape 123A

Citation

Papers of Woodruff T. Sullivan III, “Interview with A. Edward Lilley ,” NRAO Archives, accessed October 15, 2021, https://www.nrao.edu/archives/items/show/15023.