[Oort, 1953]
Jan Hendrik Oort, 1953



NATIONAL RADIO ASTRONOMY OBSERVATORY ARCHIVES

Papers of Woodruff T. Sullivan III: Tapes Series

Interview with Jan Hendrik Oort
At Green Bank WV
7 September 1971
Interview time: 15 Minutes
Originally transcribed as typescript only, retyped to digitize by Candice Waller (2016)

Note: 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). The original transcription was retyped to digitize in 2016, then reviewed, edited/corrected, and posted to the Web in 2016 by Ellen N. Bouton. Places where we are uncertain about what was said are indicated 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 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.

Click start to listen to the audio of tape 3B the 1971 interview.

[Begin Tape 3B]
Sullivan

This is an interview with Professor Oort at Green Bank on 7 September 1971.

Oort

In fact, it was the first paper by Grote Reber, I think, which impressed me greatly.

Sullivan

That was in 1940 in the Astrophysical Journal?

Oort

Yes, 1940, I think, Astrophysical Journal, which just reached us during the War in some way in which I don’t remember, but it may have been just before we got involved in the War. And that indicated immediately that one did receive radiation from the Galaxy and that this could come from all parts of the Galaxy and would overcome the great stumbling block for the investigation of the galactic disk – and the absorption of light. So I think right away I realized that this would be extremely important, too, for galactic research in which we were specializing in Holland.

Sullivan

You had no doubts about the reality of Reber’s results?

Oort

No, but that may be because I was not sufficiently critical . . . (laughter) and did not know enough about the techniques of radio observations.

Sullivan

Can I just ask you one thing: Had you thought about the radio spectrum at all before you knew about Reber’s results?

Oort

I had heard about the older observations while I was at a summer school in Harvard. I don’t remember the year now, but that was certainly after Jansky’s paper came out. Greenstein and some others discussed it, but they thought mainly of radiation from dust particles, as I remember, and so I wasn’t overly interested at that time because we wanted to get beyond the dust; we were not so much interested in getting at the radiation of the dust itself. And so I forgot all about it, which was a shame, of course, one should have realized right away the possibilities which there were - But nobody apparently did at the time, although they had thought about the problem, like Greenstein, and some others -

Sullivan

It’s easy to see with hindsight – looking back is so easy -

Oort

Yes. It seems a shame, but partly this is Jansky’s fault. Jansky himself, I mean. If I had been him I would have pursued this more strongly, I think, at the time, because he realized it quite well. And, I don’t understand why he got so discouraged by the attitude of the astronomers, and so, why he wasn’t sufficiently convinced himself that this was a matter of very first importance. But anyway, my connection with the radio astronomy started only with Grote Reber’s observations, and I made plans, during the War to get a much larger instrument that would have a smaller beamwidth to investigate -

[End Tape 3B]

Click start to listen to the audio of tape 4A the 1971 interview.

[Begin Tape 4A]
Sullivan

Now you said there was a colloquium at Leiden. You suggested, did you not originally, to Van de Hulst to look for possible radio lines?

Oort

I don’t remember exactly. I mean, it was a plausible idea to suggest this and – I don’t remember whether I suggested it or whether he thought of it first. But, he usually says, I think, that I suggested it in the first place.

Sullivan

That the way I’ve usually heard it.

Oort

I’m sorry, I don’t remember. But anyway, this made things much more promising still. But yet, when we made plans for starting radio observations after the War, we took this possibility of observing the line only as a possible extra that we might get, but our plans were really made for observing the continuous radiation. We planned right away to get receivers for 21 cm, and so, if possible, observe this line. We were in a pretty bad position after the War. Not only because so much had been destroyed and we were poor, but also because Holland had not taken any part in the radar developments that had been going on in other countries during the War. So, we hadn’t anything like the experts that they had in Australia and England, and in the United States. But our main advantage then was the strong interest from the astronomical side -

Sullivan

In the structure of the Galaxy?

Oort

Yes.

Sullivan

Was your main interest in a line in order to get radial velocities?

Oort

Radial velocities and densities, of course, yes.

Sullivan

Of the hydrogen - ?

Oort

- to measure the rotation of the Galaxy in other parts.

Sullivan

Of course, you’d worked on the galactic rotation many years before, and this would be a way to see across to the other side of the Galaxy.

Oort

Yes, the whole problem of structure, and the dynamics of the Galaxy, I had been very much interested in already, long before the War.

Sullivan

Can you summarize in just a couple of sentences, what was the view of the structure of our Galaxy in 1940? Was it a spiral?

Oort

Oh yes, I don’t think many people seriously doubted that it would have a spiral structure at that time. There were some people doubting this when I started my astronomical work, but that was around 1920. At that time there was still much disparity of opinion on this – though I don’t remember for myself that I ever thought that the spiral nebulae would be anything else but other galaxies. But anyway, it was clear that it was extremely important to be able to study spiral structure of our own Galaxy.

Sullivan

Were you the Head of Leiden Observatory after the War?

Oort

I became Director right after the War. I was Assistant Director before that time. Professor Hertzsprung, who is a Dane, was Director before the War and stayed on during the War. I was, myself, absent from Leiden for about half of the War because they closed the University for reasons I don’t have to go into now, but which were connected with the dismissal of a very famous Jewish Professor at Leiden. After the War, I approached the Government. The Prime Minister at that time happened to be a man who was a Professor in Delft of Geodesy, I knew him quite well; he was very much interested in astronomy in general and in this project, and so notwithstanding very difficult circumstances he helped the very early support for this project of building a large radio telescope which ultimately became the 25m telescope in Dwingeloo. But -

Sullivan

But you got ahold of the Würzburg thing - ?

Oort

Yes; it took some time, of course, to design this large instrument and to build it. But meawhile we had got hold of some Würzburg “Riesen” which were standing in the dunes in Holland and which had been brought to a place where they could be used by the Post Telegraph Telephone service in Holland. There came again, a man who was an officer, who was an amateur astronomer, and wanted to be using a Würzburg for solar observations -

Sullivan

Oh really? What was his name?

Oort

de Voogt. He helped us very much in those early days, because he had several of these Würzburgs, they were put up at the largest radio transmitting station in the Netherlands. This might not seem the best place to put up a telescope for receiving extraterrestrial weak signals, but it was put up there and worked quite well. It provided the first map of the spiral structure of our Galaxy.

Sullivan

Were you using German receivers also, or only the antennas?

Oort

No, no, just the reflectors -

Sullivan

I guess that was very-low-frequency radar that they were using?

Oort

I don’t know at all what they used. Possibly the (?). But the receivers were no longer there and were not suitable for our purpose anyway. We had to start from scratch in that respect and for that reason it took us pretty long to get our things working properly.

Sullivan

And, I understand, there was a fire at this time also – do you remember?

Oort

There was also a fire at one time which destroyed what had been built and so that delayed us to some extent.

Sullivan

How much do you think that delayed things? Do you remember?

Oort

I have no idea, but I’d think something like half a year or a year – of that order.

Sullivan

Did you realize that the group at Harvard was also working on this?

Oort

Oh yes, we had close contact with those groups, especially the group at Harvard. On our part, it was not really the problem of competition, very much, we were just interested in getting this line observed somewhere. (laughter).

Sullivan

Right, right - And, I guess -

Oort

And then you see we followed it up more directly than they did at Harvard. At Harvard they were not interested in the astronomical problem so much as in the technical problem. We were mainly interested in the astronomical problem.

Sullivan

Now, they actually found it first and they telegrammed you to confirm -

Oort

Yes, there was very little difference, naturally -

Sullivan

Did they telegram you to confirm it or did you independently find it about the same time?

Oort

As a matter of fact, Van de Hulst happened to be at Harvard just at that time, and I had a long telephone conversation with him, again through the PTT (laughter) – we got free-telephone over that distance – and so we exchanged the news about the 21cm line by telephone, he being in Harvard at that time -

Sullivan

I see. But this was before you had found – detected – it?

Oort

No, this was just at the time that we detected it.

Sullivan

I see. It looks like the dinner may be starting here. Was the Würzburg at Dwingeloo or was it down at Leiden at that time?

Oort

No, it was not in Dwingeloo nor in Leiden, it was at the Kootwijk transmitting station – long distance transmitting station of the PTT.

Sullivan

I see

Oort

It was not so bad, because they had all the laboratory facilities there, and it wasn’t such a bad place as it would seem. (laughter)

Sullivan

Well, I think maybe we’d better end now for this session – thank you very much. That is the end of the interview with Professor Jan Oort on 7 September 1971 taking in from 1940 to 1951, but we need another interview post 1951, or course.


Modified on Wednesday, 13-Jul-2016 09:31:53 EDT by Ellen Bouton, Archivist (Questions or feedback)