จากนักเรียนท้ายแถวสู่นักฟิสิกส์รางวัลโนเบล (5)
DeVorkin:
How did he gain support for the timing, electronics and things like that?
Koshiba:
I don't know which agency he contacted. I don't know.
DeVorkin:
Okay.
Koshiba:
But he did say he wanted to join, and he brought Gene Beier with him, who was I think at that time an associate professor or something.
DeVorkin:
Okay. So the job was to close down Kamiokande, add the anti-counters, and the timing devices. Did you have a plan to do all this?
Koshiba:
Well, it took more than I hoped. First we emptied the water tank, and then dismantled the bottom part of the phototube array.
DeVorkin:
You had to take out all the phototubes?
Koshiba:
Not all. We left the barrel part intact. We took the bottom part. And then raised the floor by about 1.5 meters and made a new floor and then made this bottom 1.5 meters as a anti-counter layer. Yeah? So the tubes are installed on the new floor, and then at the bottom there were fewer number of phototubes facing outside. Yeah?
DeVorkin:
Right.
Koshiba:
On the side there is a space of about 1.5 meters to 2 meters between the iron wall of the container and the rock.
DeVorkin:
Oh, so you didn't have to build another wall.
Koshiba:
No.
DeVorkin:
The water is contained by the rock. So this water didn't have to be as pure as the water inside?
Koshiba:
Well, it has to be pure, but not as pure as the inner water. Because, after all, light travels the distances of only a few meters. But we did have to do some sort of water leakage prevention.
DeVorkin:
So you coated the rock with something.
Koshiba:
And then also we made an additional layer on top of the detector by lowering the top layer of phototubes. And then we restored 1 meter of additional water there.
DeVorkin:
Okay.
Koshiba:
In the meantime, Al Mann and his group were preparing TDCs, and a front-end computer device. It took longer than I anticipated. They brought their own electronics and started installing. There were a number of problems and so forth, but finally everything looked fine at the very end of 1985. From early January '86, we started taking solar neutrino data.
DeVorkin:
Okay. Let's see, I have a question or two here. From Alfred Mann's book, he said that the first measurement for electron neutrinos started in December of '85.
Koshiba:
December of '85?
DeVorkin:
Yes, through '86. That it was sort of a shakedown period, that you found the background was highly variable, that the rates were higher than the predicted signal, and that there were a lot of problems. Now, I'm curious, at this point did you think that you were actually detecting a solar neutrino flux or did you know that this was a spurious background radiation?
Koshiba:
We knew that there was a tremendous amount of spurious background radiation. He said that he started the first operation in early '85, but he doesn't mention that his electronics didn't function and that he had to bring them back to Pennsylvania to have them fixed and bring them back and so forth.
DeVorkin:
Oh really?
Koshiba:
Yes.
DeVorkin:
He said that the high count rate problem tested the relations between the two groups. Quoting, he said, "tested the patience," and "patience with the other group began to wear thin."
Koshiba:
Yes.
DeVorkin:
Could you explain what he means there?
Koshiba:
What happened is this. My people, like Totsuka, became so irritated by the performance of the electronics, that they started arguing.
DeVorkin:
What kind of arguing?
Koshiba:
[laughs] Shouting at each other. Part of my job in these days was to reconcile the Penn people and my people.
DeVorkin:
How did you do that?
Koshiba:
Well, I talked to each of them quietly. [laughs]
DeVorkin:
Alfred Mann gave the impression that some of your people were reluctant to share the experience that they had in operating the detector.
Koshiba:
I don't think that was the case.
DeVorkin:
That was not the issue then. Okay.
Koshiba:
Our people were very open-minded. For instance, Al Mann brought a brand new, fresh Korean graduate student, who worked here for a couple of years and finally produced a Ph.D. thesis. He said he was very happy dealing with our people, he enjoyed everything, and found everyone very open-minded.
DeVorkin:
So the problem really was with the electronics not working right. Was this the cause of the variable background rate, or was that something else?
Koshiba:
Yes, that was part of the reason.
DeVorkin:
What were the other sources and reasons?
Koshiba:
Our understanding of the background came gradually. For instance, when you added new water to the tank, the background increased. We know that this was due to radon.
DeVorkin:
Radon, yes.
Koshiba:
The control of radon is the most difficult part of background control. We learned the hard way. We made the whole system of the detector airtight, so that the environmental atmospheric radon didn't come into the detector.
DeVorkin:
Was this difficult to find out or was this difficult to decide?
Koshiba:
Yes. We knew that radon was giving the trouble, but we brought in a specialist in radon measurement, and gradually controlled the radon contamination.
DeVorkin:
Did the Pennsylvania group and your group have different styles of research that maybe didn't mesh too well? Did you have different ways of solving technical problems?
Koshiba:
I think the main difference probably was due to the fact that Al Mann mostly worked on accelerator experiments. In the case of accelerator experiments, the environmental background is nothing.
DeVorkin:
Yes, because the signal is so huge.
Koshiba:
Yes. But in an experiment like this, the environmental background is the one you have to fight against. And since there was no established procedure to get rid of it, you had to resort to trial and error. That is kind of an irritating process.
DeVorkin:
It can make patience wear thin, as he says.
Koshiba:
Yes.
DeVorkin:
But your people understood this, I take it.
Koshiba:
We have been doing underground experiments for many years.
DeVorkin:
Yes. Was there any feeling among your younger colleagues that you could do the whole project alone, that they resented the people coming in?
Koshiba:
Probably at some time these younger people might have thought that if the boss could get the funding from the Japanese government we would have been much better off.
DeVorkin:
Did you convince them otherwise, or did you just let them think what they wanted?
Koshiba:
As the result of a rather long history of international collaboration experience, I realized the important thing was to understand the other side's feelings, their approach to science, and so forth. So I took time to explain this philosophy not only to my people, but also to Al Mann.
DeVorkin:
That's a very important diplomatic function.
Koshiba:
Well, sometimes one has to be diplomatic.
DeVorkin:
Yes, exactly. I'm not sure where to bring this in, but you know last night you talked about the deep water
Koshiba:
DUMAND?
DeVorkin:
The DUMAND project. Who asked you to head that? Did that come after this or before this?
Koshiba:
I don't remember exactly, but it was in the very early days of the project DUMAND, which must have been about 20 or more years ago.
DeVorkin:
So it was before your collaboration with Alfred Mann.
Koshiba:
Yes, before Kamioka started.
DeVorkin:
Okay. We should not forget to talk about that later on. But let's stay with Kamioka. You finally were able to reduce the background by the end of 1985. When did observations then actually begin with what you call Kamiokande-II?
Koshiba:
In the beginning of '86.
DeVorkin:
Had you actually found evidence for solar neutrinos or ?
Koshiba:
No. In order to see the signal of the solar neutrino, you had to go through various stages of background reduction, and in order to do that you had to accumulate a certain number of events. As always, the signal was masked by the background. We didn't try to extract the signal when the supernovae neutrino came.
DeVorkin:
I see. So you were in the pure data collecting mode.
Koshiba:
Mm-hmm [affirmative].
DeVorkin:
And you were probably going to go for several months yet.
Koshiba:
Mm-hmm [affirmative].
DeVorkin:
Okay. Well, that brings us to February of 1987 then.
Koshiba:
Yes.
DeVorkin:
And February 23rd. I would like very much for you to walk me through the experience. I know that you had written it out in a review paper, but it would be nice if you could flesh it out for me here, give me sort of the third dimension of what it was like when you received the news, and how you put everybody to action.
Koshiba:
Well, I will try to recollect the situation, but my memory is fading, and probably you had better check with the article I have given you.
DeVorkin:
Right. Certainly.
Koshiba:
The occurrence of a supernovae in the southern sky was first brought to our attention by a Pennsylvania colleague who sent a fax to Gene Beier, I believe.
DeVorkin:
It was a fax from S. Bludman.
Koshiba:
Bludman, yes.
DeVorkin:
Okay. And you received that on February 25th, which was two days after the event.
Koshiba:
The next day a friend of our's, a theoretical astrophysicist, Sato, also brought the news to us.
DeVorkin:
Yes. K. Sato.
Koshiba:
K. Sato. He's a professor at the University of Tokyo now. I immediately contacted the Kamioka shift to send the tapes immediately. As you already know, in those days we recorded the data on tape, and when about 20 tapes had accumulated over a week or so, they were shipped it to the University of Tokyo, where we had a big computer to analyze the data. But of course we couldn't wait until the next shipping, so I ordered the immediate shipping of the existing tapes.
DeVorkin:
I just have a very simple question. When you shipped the tapes, did you make a backup?
Koshiba:
I don't think we did. After all, tapes are not cheap.
DeVorkin:
Yes.
Koshiba:
The tapes arrived on Saturday, I believe.
DeVorkin:
Yes, let's see, it says they arrived Friday afternoon.
Koshiba:
Oh yes, Friday afternoon. There was a girl graduate student, whose name appeared on top of all the Kamioka publications.
DeVorkin:
Okay.
Koshiba:
She was a lucky girl; she became famous for that. We taught her how to analyze the data, and what the signal would look like; she had written a set of criteria for picking up the event. I had to leave Tokyo that weekend, so I was away on Saturday and Sunday. Monday morning when I came back to laboratory, Totsuka brought me this clear neutrino signal.
DeVorkin:
What's it like ?
Koshiba:
That's it, uh-huh.
DeVorkin:
Figure 5.1 in your article on observational neutrino astrophysics?
Koshiba:
Mm-hmm [affirmative]. Wait a minute.
DeVorkin:
It's page 294.
Koshiba:
Yes. This is the signal.
DeVorkin:
Right.
Koshiba:
Since our background stays at this level, this does mean something.
DeVorkin:
I would say so. You have at least 11 points there. And that occurred at, oh, I can't quite read it, but 1743 304.
Koshiba:
That's the time marker.
DeVorkin:
The time marker, yes. These are the times in seconds. Now, I couldn't help but noticing, and you do talk about it here, you have a gain check blank that occurred just a very short time before.
Koshiba:
[laughs] We were lucky, huh? [laughs]
DeVorkin:
That's pretty amazing.
Koshiba:
Almost every day we do a gain check.
DeVorkin:
And that's pure luck, I take it.
Koshiba:
Mm-hmm [affirmative].
DeVorkin:
You do describe it in here as something like that.
Koshiba:
Another piece of luck was the following. You see this event occurred on Monday I believe, and if it were a usual Monday our people would have to take the train at around 4:30 in the evening so they would have left the cave.
DeVorkin:
Oh, a usual Monday.
Koshiba:
The event happened at 4 hours and 35 minutes. So if it were a usual Monday, our people would have stopped the operation and changed the tape and then come out to get the train. So the data would have been lost for 35 minutes.
DeVorkin:
If it had been a regular Monday. But this was a hol
Koshiba:
Yes. Luckily, this was a special Monday in which the people stayed until later. So we had a number of pieces of good luck. I told you I am a lucky man. [laughs]
DeVorkin:
By March 2nd you knew that the signal was genuine. That was the March 1st entry, and that's on page 295 of your record. But then you waited until Monday, March 2nd to call representatives of the collaborating institutions. Was it at that point that you made a public announcement?
Koshiba:
No.
DeVorkin:
Oh. What happened?
Koshiba:
I had written there that the first announcement of a supernovae neutrino observation was made by the Italian group.
DeVorkin:
The Mont Blanc group, yes.
Koshiba:
Yes. Which is hours away from our signal band. I felt that we had to be very, very careful. If by any chance we made a mistake, nobody would believe our results in the future. So I told all the members of my group to make every conceivable check.
DeVorkin:
Oh, I see.
Koshiba:
And I told everybody to keep their mouths shut.
DeVorkin:
Yes. That's exactly what this record says.
Koshiba:
When I felt safe that this was not due to any unlucky background coincidence, or anything of the sort, but was really a genuine signal, I started writing up a paper for the Physical Review Letters; Al Mann and Gene Beier helped me with the English wording. But I wrote the draft myself.
DeVorkin:
I just have to ask a question though. A lot of the others were sending their announcements to the Central Bureau for Astronomical Telegrams at the Smithsonian so that they could be announced very quickly. That's one of the ways the priority in astrophysics is established. But you chose to send yours instead to
Koshiba:
Physical Review Letters.
DeVorkin:
Yes. And you did not send an Announcement to the Smithsonian.
Koshiba:
Well, after I had sent a paper to the American Physical Society, I contacted
DeVorkin:
Brian Marsden. Is that right?
Koshiba:
Mm-hmm [affirmative].
DeVorkin:
So everybody was checking for errors.
Koshiba:
Yes. When I finally sent the manuscript to Physical Review Letters, I told my collaborators, "Now you can talk about it." Of course, Al Mann wanted to make several long distance calls addressed to John Bahcall and other people. I told our collaborators that, "You can announce the content of the abstract." The abstract appears at the top of our paper, and gives the essential parts signal times, the number of events, and so forth. Now comes a rather touchy point. Just about this time I received a long distance call from one of the IMB collaborators.
DeVorkin:
This was either March 9th or 10th.
Koshiba:
Before that. I cannot tell you exactly what day it was, because my diary was stolen in Rome.
DeVorkin:
What? Ohhh!
Koshiba:
I had a little pocketbook in which I jotted down significant events.
DeVorkin:
A day book sort of. And it was stolen?
Koshiba:
In the subway in Rome.
DeVorkin:
Oh no! That would have been a wonderful thing to have.
Koshiba:
Yes. I missed it too. But what happened was this. The young man from the IMB collaboration wanted to make it out that IMB was, in fact, the first discoverer of a supernovae neutrino, before Kamiokande.
DeVorkin:
And before Mont Blanc as well.
Koshiba:
No, Mont Blanc we don't worry about, because by that time we knew that their claim was spurious.
DeVorkin:
Really?! Oh, I see.
Koshiba:
Mont Blanc.
DeVorkin:
I knew the time didn't agree.
Koshiba:
But they didn't consider the possibility of a correlated background, which I analyzed in our paper and also in that paper.
DeVorkin:
Yes. So that was pretty much discredited completely.
Koshiba:
It was a very long conversation, but finally I became angry. Because Sugawara, head of the theoretical division at KEK, spent two months every year in Hawaii with a good friend in the University of Hawai, an Indian-American theoretical physicist, by the name of Pakvasa. And John Learned of that university belonged to the IMB collaboration.
DeVorkin:
Okay.
Koshiba:
Since KEK is one of the sponsoring institutions, Sugawara knew about our finding the signal and the signal type. Before I could release the news of the abstract of our paper, he telephoned Pakvasa with the signal time and so forth. This was immediately brought to the attention of John Learned, who was a collaborator of IMB. John Learned started searching for the signal, using the Kamioka signal time, and found it in the IMB data.
DeVorkin:
So the IMB people weren't looking for the signal?
Koshiba:
No. They were looking for a signal at the time of the Mont Blanc signal. Of course they couldn't find signal. Okay? However, unless they were given some specific short time period to look for, their detector background level is 20 to 30 MeV, because of the small number of photons they can observe. Okay? Therefore there are lots of background in the 20 to 30 MeV area. And unless you specify this is the time period, you just cannot look all the way.
DeVorkin:
So yours was easy to see because your background rate
Koshiba:
Was very low.
DeVorkin:
In their case, the signal was there, but it was swamped by the background, so you had to know exactly where to look.
Koshiba:
That's right.
DeVorkin:
So both groups were frantically looking, but you could find it right away, I mean comparatively.
Koshiba:
This I knew because Sugawara later confessed that he leaked the information to the University of Hawaii.
DeVorkin:
But was it really a leak? I mean, he just was being collegial.
Koshiba:
But when the principal investigator of the experiment said to keep quiet until everything was made certain.
DeVorkin:
Yes. How did you feel about that?
Koshiba:
Well, I felt bad. But Sugawara immediately contacted John Learned, and received a copy of John Learned's manuscript to the other members of the IMB collaborators. Learned's manuscript stated that knowing the Kamioka signal time, he searched part of the IMB data and found the signal.
DeVorkin:
Well, that's honest. But who was it who ? What was the nature of the phone call, though, to you? What were they trying to get you to do?
Koshiba:
This man wanted to convince me that IMB found the signal independently of Kamioka, and that happened before Kamioka's discovery of the signal. That's what he tried to convince me.
DeVorkin:
And did you believe him?
Koshiba:
Of course not!
DeVorkin:
But you didn't know at the time that it had leaked, did you?
Koshiba:
Well, I was suspicious. The next day Fred Reines made a long distance call to me, because they were having an IMB group meeting, and this man must have been saying let's claim that we discovered the signal independently, and first, and so forth.
DeVorkin:
You're not telling me who this other person was.
Koshiba:
No. I'm not going to tell you, because that was a dirty trick he played on me.
DeVorkin:
But Fred Reines was not the person, I mean obviously.
Koshiba:
No. When I received this long distance call from the young man at the IMB collaboration, I was furious. I called up Sugawara, and he finally admitted that he did give away the time information, but promised me that if any problems arise, he would get John Learned to testify. Later I received a copy of Learned's internal memo. The next day Fred Reines called me on the phone, while in the middle of an IMB group meeting, and said that he knew this young man had called me on the subject.
DeVorkin:
He was a junior member of their group, sounds like.
Koshiba:
Yes. Fred was quite apologetic. He said he was sorry that this has happened. He said further, "Would you be satisfied if we included the following sentence at the end of our paper?" The sentence went like this, "First they searched for a signal at the time of the Mont Blanc experiment. They didn't find any. Then, knowing the signal time of Kamioka experiment, they searched for a signal and indeed they found one." "Does that satisfy you?" Fred said. Yes, that's fair. I'm happy about that.
DeVorkin:
Yeah. So that was all cleared up.
Koshiba:
Mm-hmm [affirmative]. Fred was very fair.
DeVorkin:
Yes. Well, he already had his Nobel Prize.
Koshiba:
Not yet.
DeVorkin:
Oh no! '95, okay, I'm sorry. Okay.
Koshiba:
No, he was a fair person.
DeVorkin:
That was what actually happened.
Koshiba:
Mm-hmm [affirmative]. Not many people noticed the last couple of lines of their paper. So many American scientists think that IMB and Kamiokande made independent discoveries.
DeVorkin:
That's why. But it's in the literature. I can find it in
Koshiba:
It's in the original paper. Yes.
DeVorkin:
Okay. That's fine. It makes sense that with your lower background you can find things a lot faster. Did either group have the ability to search at that time automatically, in other words by computer? Or ?
Koshiba:
We didn't have an automatic supernovae watching device. We now have one.
DeVorkin:
What happens now if a signal is ?
Koshiba:
If it occurs say about this scale, then it will be known to the shift person within a minute. It gives a warning.
DeVorkin:
Do red lights start flashing?
Koshiba:
Yes.
DeVorkin:
Do they really?
Koshiba:
Well, not exactly, but it does give a warning.
DeVorkin:
Uh-huh, that something has happened.
Koshiba:
Then the information would be sent to this astronomical union, the what you call it
DeVorkin:
Oh, the Central Bureau of Astronomical Telegrams. Yes, which is of course one man, Brian Marsden. Right. There was a press release made by the ministry of education?
Koshiba:
Mm-hmm [affirmative]
DeVorkin:
And simultaneously by the University of Pennsylvania?
Koshiba:
Mm-hmm, mm-hmm [affirmative].
DeVorkin:
And you say this was the end of the hectic days.
Koshiba:
Yes. [laughs]
DeVorkin:
There was not a big public response? Didn't people, news and ?
Koshiba:
Well, yes. TV and newspapers wrote about it. First of all, I didn't intend to have a press release, but the collaborators, especially Al Mann, wanted to have one.
DeVorkin:
Oh, I see.
Koshiba:
Originally I thought I would do it in the University of Tokyo. But the minister of education people heard about it, and wanted to have it in their own building.
DeVorkin:
Well, it was a big deal, I imagine. It certainly was in the United States. It was on the 6 o'clock news constantly, what was being revealed, what was new. Now, how did this supernovae event change life around here? Your primary program was solar neutrinos, and proton decay? Is this all correct? So was this discovery disruptive of the normal routine, or did it take a while for you to get back to the normal routine?
Koshiba:
Well, I told all of my collaborators to concentrate on solar neutrino observation. They went back immediately to the solar neutrino analysis.
DeVorkin:
When did you start getting solar neutrino data?
Koshiba:
Let's see. It took more than half a year before we could make the background subtraction and see the sign of the signal.
DeVorkin:
And what did you conclude from that?
Koshiba:
Well of course you see when the statistics are low you cannot say very much, but the first paper on solar neutrinos was published I believe at the end of '87. I don't remember. You better check that with a reference.
DeVorkin:
Yes, I can do that.
Koshiba:
But in the first paper we already knew that indeed the flux was lower than theoretical expectations by a factor of more than two.
DeVorkin:
You found a little more than Davis did.
Koshiba:
Mm-hmm [affirmative].
DeVorkin:
Yes. But it was still closer to Davis than to Bahcall's theoretical predictions. And has that stayed pretty much the same all this time?
Koshiba:
Mm-hmm [affirmative].
DeVorkin:
Even with the Super-K?
Koshiba:
Yes. Forty-six percent or something.
DeVorkin:
Mm-hmm [affirmative]. Did you start hiring your own astrophysical theorists here to try to sort out what the differences were and what the problems were?
Koshiba:
No, we didn't hire theoretical people. We were just experimentalists. But we had colleagues in the physics department. K. Sato is a good theoretical physicist.
DeVorkin:
And did you start trying to encourage people like Sato to look at the standard model, this time in terms of the proton-proton reaction?
Koshiba:
K. Sato is more interested in cosmology rather than in the solar model.
DeVorkin:
Has he found any of your data of use for cosmological speculations?
Koshiba:
I don't know, but he did use our result, for instance, in establishing an upper limit on the massive particles decaying inside the sun in relation to the missing mass. He is also very much interested in the latest result on the non-zero mass of the neutrinos.
DeVorkin:
How did that come about? I'd like you to walk me through that observation.
Koshiba:
Well, the first anomaly I noticed was at the time of old Kamiokande. After my retirement at the end of March '87, I was invited to spend four months in Hamburg and one year at CERN. When I came back, I looked at the accumulated Kamiokande data, and I noticed a funny thing, that is, a nu-mu event. The neutrino which produces muons on interaction.
DeVorkin:
Okay.
Koshiba:
A Nu-e event is what the model predicted, but the flux of nu-mu seems to be considerably lower than expected.
DeVorkin:
So you had come back from Hamburg and ?
Koshiba:
No, I had just come back from CERN.
DeVorkin:
Oh, CERN. Okay.
Koshiba:
Back in Tokyo I looked at the accumulated data of Kamiokande and I noticed this, but it is not my type of experiment to compare the absolute flux with the model of prediction, because I don't trust those model predictions. So I took the ratio of the two types of neutrinos, nu-mu flux and over nu-e flux. If you take this ratio, many uncertainties cancel out in the model. One can then compare it with experimentation, which can be derived rather easily and simply. I like to consider the problem in the simple, clear-cut way. How are those neutrinos produced in the atmosphere? The cosmic rays, first of all, have to produce mesons, like pi-mesons or k-mesons. Those particles then decay in thin air into mu + nu-mu. Okay? Decay product muon, when the air is still thin, would have time to decay into an electron + e-nu + nu-mu. Alright, you count the number of neutrinos. In the first decay, you get one nu-mu. Okay? In the second decay, you get one nu-mu and one nu-e. Alright? So originally, nu-e flux and nu-mu flux has to be in the ratio of 1:2. As simple as that. Of course, there is a modification due to a difference in the energy spectrum in the first decay and second decay, but they are minor corrections. And also the contribution of k-mesons makes a minor correction. But this ratio cannot be very much away from 1:2. As I mentioned, the ratio we observed in Kamiokande was 1:1. So there was a factor of 2, which I thought this was real. So I checked the various causes, and had written a draft and circulated it among the Kamioka collaborators, inviting objections and comments, and so forth especially because one of the graduate students of IMB had just published a paper which showed no anomaly in the ratio of the nu-mu flux to the nu-e atmospheric neutrino flux.
DeVorkin:
They found no anomaly.
Koshiba:
No anomaly, the man claimed. But when I looked at the IMB data and took the ratio, it was again 1:1, not 1:2.
DeVorkin:
Using their data?
Koshiba:
Yes. But this young man, in writing up his thesis, didn't want to make the statement which brings a big argument among the professors who judge his thesis. So he concluded that nothing extraordinary was happening, and that everything was in order, that's what he wanted to show probably. But later I heard that this young man was kicked out of IMB collaboration, and later I indeed did admit that there is a ratio discrepancy which is enormous.
DeVorkin:
I take it you published this result?
Koshiba:
Yes.
DeVorkin:
Yes. That's quite interesting. You said you were retired by now? You retired in '87?
Koshiba:
Mm-hmm [affirmative]
DeVorkin:
And that was right after the supernovae.
Koshiba:
That's right.
DeVorkin:
Did it have anything to do with the supernovae?
Koshiba:
No. It's a compulsory retirement at the age of 60.
DeVorkin:
Sixty?
Koshiba:
Yes. The University of Tokyo has such a rule.
DeVorkin:
Okay. So supernovae or not, you retired.
Koshiba:
That's right. The lucky thing was that it happened one month before my retirement. [laughs]
DeVorkin:
How has life changed for you since you retired?
Koshiba:
Well, a retired Japanese professor's life is quite different from a retired American professor. American professors can keep their office at the university, can keep their secretary, and can also keep receiving research funds. None of these perks are available to a Japanese retired professor.
DeVorkin:
Really? But you have been very active.
Koshiba:
The usual thing for a University of Tokyo retired professor to do, is to find a job in some private university.
DeVorkin:
Ah, that's it.
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