War and Peace in the Nuclear Age; Interview with Carl von Weizsacker, 1986

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WAR AND PEACE IN THE NUCLEAR AGE - TAPES A01012-A01014 CARL VON

WEIZSACKER

Fear of German Bomb

Interviewer:

LET'S START OUT TELLING WHAT WE TALKED ABOUT BEFORE, WHEN YOU HEARD

FROM OTTO HAHN IN CHRISTMAS OF 1938. I THINK WE DON'T NEED TO START

EARLIER THAN THAT.

Weizsacker:

Yes, because you have that anyway in another context, already. Well, I

mean, I just want to say, I'm had been working with Otto Hahn, in '36

for half an...half a year. And I...continued to live very close to his

Institute, and as he knew me. And in, just after Christmas '38, Hahn

called me by telephone and asked me can you tell me, do you think there

is a substance, a chemical substance, which ought to be radium, but

which in all chemical reactions goes with barium? And then I said, well

that's a strange question, how do you come to ask that -- such a

question? He said, well, I seem to have such a substance. Then I said,

well, I would think it is barium. He said, yes, I have come to the same

conclusion, but if this is so I have split the uranium atom. So this

was the first way I learned about nuclear splitting, And it was

immediately after Hahn had discovered it himself. And as you see there

was not the slightest intention of using it for anything. He just

wanted to know whether this strange substance was radium or barium. And

it happened to be barium.

Interviewer:

SO THEN AS YOU WERE TELLING US EARLIER, IN FEBRUARY OF '39 WHEN YOU

TALKED TO HAHN AND LEARNED ABOUT THE JOLIOT LETTER?

Weizsacker:

Yes. Yes. I mean the point is it was two months later, the end of

February.

Interviewer:

START AGAIN...

Weizsacker:

In February of '39, Otto Hahn, I visited Otto Hahn, or I visited a

little colloquium in his Institute, in Dahlem, and there I learned that

he had received a letter from Joliot in Paris, in which Joliot told him

that in the uranium fission which Hahn had identified and which Joliot

was easily able to repeat some additional neutrons were produced. So

the uranium nucleus is split by neutrons and by its being split, new

neutrons are released and this was Joliot's discovery in that moment.

And then, in that very moment, when Hahn told us that, the little

group, it was quite clear for us that this meant that probably or

possibly the chain reaction would be possible, a reaction by which the

newly produced neutrons split other uranium atoms and so on

indefinitely, which would mean to release the whole energy or a large

part of the energy contained in the uranium in one step. And when I had

learned that from Hahn, I went to a close friend, Georg Picht, who

lived in Berlin as well, and who was a philosopher, and told him I have

just learned that it is probably possible to make a bomb which will be

able to destroy a whole city and now tell me what is going to happen

now. And we were sitting together the whole night, as you can imagine.

And our conclusion was, if this is so, if this turns out to be

technologically feasible, there is only a choice of two things, either

the institution of war must be eliminated, must be abolished--the

political institution of war--or mankind will be abolished. That means

from that moment on I knew--and I was not the first one to know that--I

should say, I knew that we have this choice. I should just add a thing

which at that time didn't even come to my mind as a third alternative.

Today at least it is quite clear the problem will not be solved by

abolishing the nuclear weapon only. Because it is there. We know how to

make it. And it can be repeated, even if all nuclear weapons would be

destroyed. So while it might be a good thing to abolish nuclear

weapons, the true solution of the problem is not that. The true

solution is to abolish the political institution of war which means a

complete change in the political structure of the world, and this

change has not been achieved so far. And I just say that in that night

in February or perhaps early March, '39, two young Germans were sitting

together and understood that. And Leo Szilard in the United States, as

I later learned, had understood it even several weeks before us.

Interviewer:

AND SO WHAT HAPPENED? WE ALL KNOW THAT IN THE UNITED STATES LEO SZILARD

WROTE THE LETTER WHICH EINSTEIN SIGNED AND IT WENT TO ROOSEVELT AND IT

LED THE WAY TO THE MANHATTAN PROJECT AND THE BOMB.

Weizsacker:

Yes.

Interviewer:

WHAT WAS HAPPENING IN '39-'40 IN GERMANY?

Weizsacker:

In Germany. Well, to begin with not very much did happen. And a

collaborator of Hahn, Siegfried Flügge wrote a paper on that in a

German scientific periodical, and this paper as I know was written

after Hahn and Flügge had agreed that it would be better to make all

this thing public and not to keep it secret, because for Hahn, this

meant then at least if the weapon was possible it would not be in the

only possession of Hitler. So he was interested in making it public,

while on the other hand Szilard had tried to make it secret because he

didn't want that it should get into the hands of Hitler. But this was

only a publication and no more. And then in the beginning of the war,

beginning of September '39, the German arms production office, in the

Germany Ministry of Defense or of War as it was called at that time in

all countries, started an enterprise to study the problem. First of all

to study it, but if it would have turned out that we could make nuclear

weapons they would certainly have said we want to make them. It was

quite clear to the physicists who took part in it that it would equally

be possible to make reactor, what we now call a reactor, and it was

also clear that this was the easier job, easier than the bomb. In fact,

as you know, Fermi has made the first reactor in December '42, while

the bomb was only ready in '45, after an immense effort. So as group of

German physicists started at that. I was in the very first --on of the

very first people to cooperate in that. I wanted to know about the

thing. Heisenberg entered it...into it, Hahn entered into it, and we

tried to find out what was the case. I may make the remark that Hahn,

when I told him in October '39 that it might be a good thing for him to

participate in the effort, he said, well I understand this will protect

my Institute, it will protect the people working there as they might be

sent to the front or whatever else might happen, so I think he said, I

must do it. But and then with high emotion, he said, but I tell you if

my work would lead to Hitler getting a nuclear bomb I shall commit

suicide. This was his clear, clear reaction. But it was equally clear

that it was not very probable that we would achieve a bomb, so, and in

fact, this was '39, it was not quite clear, it might have been

possible, but in say late 1940, we had understood that the number of

neutrons produced in one fission act was not large enough for making

the bomb an easy enterprise, We found it would be extremely difficult,

and our conclusion was that we would not be able to make it -- not be

able to make it during the war of course. Well, you have a question?

Interviewer:

YES. COULD YOU TELL US AGAIN, THE GERMAN MINISTRY OF WAR, DID THEY TAKE

THE INITIATIVE TO COME TO THE PHYSICISTS AND SAY WE WANT YOU TO DO

RESEARCH TOWARDS IT? HOW DID THAT --

Weizsacker:

Well, the question who started it is always a difficult question. In

the American case as I learned after the war, the initiative was really

with a few physicists. And I think Leo Szilard was perhaps the leading

spirit of that and Einstein's letter to President Roosevelt was the one

which was certainly instrumental in -- to a certain extent in starting

the thing. And I understand that very well because the physicists knew

about the thing and the physicists were afraid that the German would be

able to make the bomb, which I fully understand as a motive. In Germany

the War Ministry, there in that particular group were one or two

physicists who were fully aware of the situation. One of them was for

instance, Kurt Diebner, who later on, he was not a great physicist but

he was quite a good physicist. And he had followed the whole thing and

he had convinced his superiors that this would be a thing that would

have a good chance of working, and so he induced the office to take the

initiative. And in this sense I would say whether it was really an

initiative of the physicists or not is not quite the precise question.

It was not...the community of physicists who had the initiative, in

that sense the initiative came from the War Ministry.

Interviewer:

SO THE PHYSICISTS FAIRLY EARLY ON DETERMINED THAT IT WOULD NOT BE

POSSIBLE. YOU AND OTHERS FELT THAT IT WOULD NOT BE POSSIBLE TO BUILD A

BOMB DURING THE WAR? THE EFFORTS WENT MORE TOWARD A REACTOR?

Weizsacker:

Yes, this is certainly so, and to be precise, now my recollection may

not be absolutely precise for half a year or so, but as far as I

remember it was more or less around Christmas 1940, a year or a little

bit more than a year after we had started that we said, no, it is quite

improbable that we will be ma -- able to make a bomb. And then we had

to make proposals to the proper -- authorities. And our proposal was to

make a reactor, and we mentioned the distant possibility of a bomb, but

we only said, that's a distant possibility, and we are not proposing to

do it. We were not proposing to do it. So this was the -- but this

again was a little bit later, I think this explicit proposal for a

reactor was made, if I'm... if I remember rightly sometime in '41.

Interviewer:

SO WHY WAS IT THEN THAT THE EMIGRE PHYSICISTS IN THE UNITED STATES FELT

SO STRONGLY THAT GERMANY WAS... COULD VERY LIKELY DEVELOP AN ATOMIC

BOMB FOR USE DURING THE WAR?

Weizsacker:

Yeah. Of course, that's the question you must necessarily ask. I mean

now I was in Germany and I know a little bit about our motives and even

I would say of motives of Germans. You could never be quite certain

because in the Nazi rule one did not always tell his true view. So even

about the motives of some of my fellow scientists in Germany I

may...may not be fully informed. I know my own motives. On the other

hand with the American motives, as far as I'm informed as far I learned

about it, I think in 1939 at the beginning when Szilard wrote

Einstein's letter then neither the Americans nor the Germans knew that

it was so difficult. We in Germany expected that the war would -- might

last a year or so, or perhaps two years, we did not expect five years.

And on the other hand, to do it in one year or two year seemed

improbable anyway, but one couldn't know. And I think that Szilard

expected a long war and he was right in that as he was right in most of

his predictions. And he might have thought that we might very well

succeed. And he did not know and we did not know at that time the

precise figure, the precise number of neutrons to be produced in one

splitting in one fission experiment, of one case of fission. So he

might have been right. Later on-

Interviewer:

COULD YOU START BACK JUST A COUPLE OF SENTENCES WITH THE POINT THAT IF

YOU HAD KNOWN HOW MANY NEUTRONS WOULD BE PRODUCED BY EACH FISSION IT

WOULD HAVE BEEN DIFFERENT.

Weizsacker:

Well, I mean the point is, when...in the beginning we did not know the

number of neutrons. We did not know some other things too. I mean there

were cross-sections of substances by which you can produce slow

neutrons and a lot of complicated questions. I just mentioned the

number of neutrons as one example. And the most important one. And I

say as long as you didn't know the number of neutrons produced in one

single fission you could not know about the whole thing. If there had

been less than one neutron per fission it would not have worked at all.

If there had been ten neutrons per fission it would have been extremely

easy to make a bomb. In fact it turned out it was a little bit more

than one, but not so very much more, and therefore it was a thing which

would be very hard to achieve, and the estimate how hard to achieve,

that is a difficult thing. And I can easily imagine again that our

American colleagues during the war came to understand slowly that

probably what they could not achieve soon would not be achieved soon by

the Germans. But again it is far more difficult to guess sitting in

America what the Germans know, than it is for the Germans to know what

they know themselves. So far as it was easier to see that with our

knowledge we would not be able to make it. But it was not so difficult

--so easy for the Americans to know since they might imagine that we

might have found a way which they would not have found. So I can fully

understand that our American colleagues in say until '43 or so thought

we might be quite dangerous. And then slowly they understood that since

it was as difficult as they realized we would probably not do it

either. And the first confirmation that we had not even tried it came

when my office in the University of Strasbourg was ah, captured in '44,

I was no longer there, and they found my whole files. And by -- they

read in my files and found that we were very, very far from the bomb.

And I had left the files there because I knew that's not an interesting

matter. I was not aware that the Americans would think we were close to

the bomb.

Interviewer:

GIVEN THAT EARLIER IN THE '30S BEFORE THE WAR STARTED THERE WAS SUCH AN

INTERNATIONAL COMMUNITY OF PHYSICISTS, THOSE SCIENTISTS WHO ENDED UP IN

THE UNITED STATES, MANY OF THEM KNEW HEISENBERG AND KNEW YOU AND KNEW

OTHERS. WHAT I'M WONDERING IS, KNOWING YOU THE WAY THEY DID DO YOU

THINK -- WHY DID THEY THINK THAT PHYSICISTS WHOM THEY HAD WORKED WITH

AND WHOM THEY HAD KNOWN WOULD TRY TO DEVELOP A BOMB FOR USE BY HITLER?

JUST POLITICALLY SPEAKING, WAS THAT A RELEVANT --?

Weizsacker:

Of course I mean that was a relevant question. And that now is a

question of how they thought about us. And again they must have --but I

can say what is my guess or what is my knowledge after having talked

with them after the war. And one thing in the letter of Einstein to

President Roosevelt, my name is mentioned, and it is mentioned because

Szilard knew me, or he knew my name, but he didn't know me personally.

And my father was high ranking diplomat. He was in the German Foreign

Office at that time. And it looked quite plausible that if I told my

father we can make a bomb, my father might have told Hitler and Hitler

would have said, well, just go on, do it! The fact that my father was

in close connection with the German resistance was not known, and if it

had been known it would have been deadly for my father, my father would

not have survived this knowledge. Second, what I thought about these

matters was not well-known to Szilard who had never seen me. Again

about Heisenberg. Heisenberg was a German patriot. Heisenberg had had

the opportunity of leaving Germany in '39, still in '39, and had

returned into Germany from the United States and for instance, Sam

Goudsmit had seen him then and knew that Heisenberg had decided to

return to Germany, so he could think perhaps Heisenberg wants to make

bomb --

[END OF TAPE A01012]

Interviewer:

DO YOU THINK THAT THE EMIGRE PHYSICISTS IN THE UNITED STATES, WHO KNEW

YOU, WHO KNEW HEISENBERG, WHO KNEW THE GERMAN PHYSICISTS FROM THE BORN

INSTITUTE, DID NOT THEY KNOW THAT YOU WOULD NOT WANT TO DEVELOP A BOMB

FOR HITLER, OR WAS THERE SOME DOUBT? WAS THEIR FEAR JUSTIFIED?

Weizsacker:

Well, I mean their -- I should say that they had the fear is known to

me. That they feared we might make the bomb. And whether it was

justified or not, I should first say the information they possessed was

not sufficient to dis -- dispel the fear. In Einstein's letter to

President Roosevelt, my name is mentioned... is mentioned, that was

Szilard who knew my name quite well and knew that I was a nuclear

physicist. And he might have thought -- my father was in high position

at the German foreign office that I might tell my father and my father

might tell Hitler, and then Hitler would have said, well, go ahead with

the bomb. He did not know and he could not possibly know that my father

was in close connection with the German resistance. And if he had known

Hitler would have known too, or the Gestapo would have known too and

that would have been the end of the life of my father. And about

myself, again since he did not know me personally it was difficult for

him to judge. In addition, also about Heisenberg, I would say, that

Heisenberg had been in America in summer '39, had seen for instance Sam

Goudsmit at that time and had said, "I want to return to Germany." And

this of course, could open up the suspicion that he wanted to go home

in order to make those bombs. Now as to the true situation, I think we

should not go into one of the extremes. Some people have said that we

the German physicists, by a conscious effort made it impossible that

Hitler should have gotten a bomb, should have got a bomb. This is not

so. I should not say so -- say that. Others, Goudsmit, for instance,

thought we were very eager to make a bomb, but we were not able to do

it. This is -- neither this is true. But the point is when we learned

that we could not do it we were relieved. We were profoundly relieved.

But had we been able to make it I shall not say for certain what we

would have done. Some of us might even have, as I said about Hahn,

committed suicide, or tried to make it impossible. Others might perhaps

wanted to make it, and human nature is not an easy thing to judge, but

I know that we were profoundly relieved when we found we couldn't make

it. But this was not known to our American friends. And then, the they

-- we knew around the end of 1940 that we could not possibly make it.

The Americans did not know that we knew, and they did not know that it

was so hard, because they could imagine that we might have found an

easier way than the Americans have found. And if I'm rightly informed I

think it only dawned slowly to our American colleagues that it was so

difficult that the expectations that the Germans would have been able

to make it during the war with the...under the conditions of air raids

and all the other difficulties that this was very improbable. Finally,

they learned that we were extremely far from even trying to make a bomb

from the files which I left behind when I had left Strasbourg, where

then I was a professor. And they read the files and found evidently

there was absolutely no German effort to make a bomb.

Interviewer:

WHY DO YOU THINK THE HITLER REGIME DIDN'T PUSH FOR A BOMB? WHY DO YOU

THINK THEY DIDN'T COMMIT MORE RESOURCES, INDUSTRIAL FACILITIES, MONEY?

Weizsacker:

Yeah. Well, first of all I should say how much effort was made. The --

in addition to the budgets which existed anyway, to the budgets for the

Institutes and for paying the salaries and so on, the whole effort

during the war in Germany had, the size of DM 8 million, which at the

currency as it was then, corresponded to $2 million. And the American

effort as is well known was $2 billion, a thousand times more. So the

German effort was minimal as compared to the American. Second, why? And

I say, even if we had tried to spend $2 billion or DM 8 billion mark we

would not have succeeded. This we did not know for certain and we --

nobody of us in Germany ever had the idea that during the war any

country at war could spend such an enormous amount of money for an

enterprise whose success was not certain. And when we learned about the

bomb of Hiroshima, we were absolutely surprised. Heisenberg needed 12

hours to believe it. I was present. I remember. He said, this is not

possible. This must have been something else, because I know how

difficult it is. And when we learned some weeks later that $2 billion

had been spent for it, we were amazed. We had never thought that

anybody would try such a thing. But I say, even with $2 billion we

would not have achieved it, given the fact that our technology was not

as good as the American technology. That Hitler had been able to expel

more than 50 percent of the really good physicists, and that during the

effort, during the war with air raids with all possibilities of

discovering in such a small country as Germany what was going on there,

it would -- an enterprise like Los Alamos or Oak Ridge or something

like that would have been destroyed by an air raid and the whole effort

would have been destroyed too. So in fact we were right in thinking

that we could not do it. But we were in error thinking that nobody

could do it, the Americans could.

Interviewer:

SO HITLER WAS NOT PURSUING SOME KIND OF WONDER WEAPON?

Weizsacker:

Well, I mean when Hitler or Goebbels spoke about the wonder weapon in

the late part of year... the war, I think they were thinking of V-1,

and V-2, that means of the rockets, not of the nuclear weapon. And I

don't know whether Hitler ever was told about the possibility of nu --

the nuclear weapon. He may have been told, but I remember, perhaps an

interesting story, a detail. I once talked to one of our military

superiors about the question, whether the whole enterprise was known to

Hitler and what was the consequence. And he said, "Please, please,

please, don't try to inform Hitler about this. Because when the Fuhrer

learns that such an idea exists, he will say, all right, half a year

from now the bomb will be there. And then you will be the ones who will

not do it. You will be unable to do it. And all the difficulties that

arise from that will be yours."

German Physicists Reaction to Hiroshima

Interviewer:

COULD YOU NOW TELL US ABOUT THE CIRCUMSTANCES IN 1944, IN WHICH

THE--GERMAN SCIENTISTS YOU INCLUDED WERE CAPTURED AND ENDED UP IN

ENGLAND?

Weizsacker:

Well, I mean '45. '45. I mean we were captured at different places, and

under different circumstances. And it was a group of ten which was

assembled late in April, '45, first brought to Heidelberg, then to

Paris, then to Belgium, and in early July, I think 3rd of July to

England to Manchester, not very far from Cambridge. And there we were

as we were told, detained under His Majesty's pleasure. We were treated

like, well, we were well treated. Treated like as you would say,

captive generals or so. And we didn't know why we were interesting.

Evidently we were interesting somehow in connection with our war work

because we saw what was the selection of physicists who were brought

there. But since we did not know that the bomb was already underway, we

felt we are not very interesting. But we were kept there, we were told

absolute secrecy was necessary. We were told, if anybody learns in the

world that you are here, 24 hours from now you will be in another

continent. But for the rest, we were treated well. And there we were

sitting, and one day in August we learned why. When the radio brought

the news of Hiroshima.

Interviewer:

OK, HOW DID YOU PERSONALLY REACT TO THE NEWS OF HIROSHIMA?

Weizsacker:

Well, I would say I told you before that my first great shock came when

I learned that the bomb might be possible in February of '39. And this

shock was the greatest I ever had about the thing. But I knew now there

is still some time and perhaps the world situation will become such

that it will be able, it will be possible to overcome war, and still it

was not quite clear that the bomb was possible at all. It was only

probable. Now when I first learned about Hiroshima... my impression

was, now I know what will be the main enterprise or the main occupation

for the rest of my life. To do something about the consequences.

Interviewer:

DID YOU BELIEVE IT? MAYBE YOU COULD ANSWER THAT AND THEN TELL ME ABOUT

HEISENBERG BEING SO UNBELIEVING.

Weizsacker:

The I gave you just a picture about...about my reaction. And when I

heard about the -- when I heard this news through the radio my

immediate reaction was, this is true, this must be so. But Heisenberg,

for instance, who was by far a better physicist than myself, and who

had really been the man....been the man who was the intellectual leader

of the whole enterprise, needed something like 12 hours in order to

believe it. And this was because he knew how difficult it was, and he

could not imagine that the Americans might have done it, and therefore

he concluded it must be something else...which erroneously or perhaps

with some purpose, is called a nuclear bomb. But then when more news

came through, of course he had to accept the fact, and when we learned

finally that $2 billion had been expended for that, we said, well,

perhaps with $2 billion it was possible. But this had been absolutely

beyond our imagination to do such a thing.

Interviewer:

AND WHAT ABOUT OTTO HAHN'S REACTION TO THE NEWS?

Weizsacker:

Well, Otto Hahn, I think fell into despair, Not for long. He was a man

with good vitality.

Interviewer:

I'LL START OVER AND SAY, "WHEN HE HEARD THE NEWS OF HIROSHIMA..."

Weizsacker:

Yes. Well, when Otto Hahn heard the news of Hiroshima, I remember very

well that the first thing we, the others thought, or one of the first

things we thought, now we must take -- take care of Hahn. This is such

a horrible news for Hahn that we must try to be present in order that

he should not do something very bad to himself. Now time passed and

Hahn was always horrified by the fact, but he later on decided that

after all nuclear energy, peaceful use of nuclear energy was a good

thing and this was a consolation to him.

Interviewer:

WHY DID HAHN REACT SO STRONGLY, SO DESPAIRINGLY COMPARED TO THE OTHERS

OF YOU?

Weizsacker:

Well, I mean we all were in a way shocked. That is quite clear. But the

shock went into slightly different directions. And for Hahn, you see,

this had been the great discovery of his life, uranium splitting. He

did not yet know that he would receive the Nobel Prize for that, but it

was quite clear that it was worth a Nobel Prize and one of the best

ones. And Hahn had been very, very concerned about the problem that

Hitler might...might get the bomb. And Hahn had wished very clearly for

a western victory all through the war. He wanted to get rid of those

horrible Nazis. And then in August 1945 he learns that those whose

victory he has wished have committed such a horrible crime. That was

Han's reaction. And he said, "And I made it possible." Repeat it. Keep

it with the music.

Niels Bohr

Interviewer:

ONE THING I WANTED TO ASK IN THE BEGINNING THAT I SKIPPED OVER, MAYBE

YOU CAN BRIEFLY TALK A LITTLE BIT ABOUT THE BOHR INSTITUTE AND THE

OTHERS THAT YOU KNEW THERE, AND THE OTHERS THAT WE IN OUR FILM,

WEISSKOPF, AND THE PRE-WAR ATMOSPHERE WHERE THE PHYSICISTS WERE SHARING

AND COLLABORATING.

Weizsacker:

Yeah, well I'm very glad to speak about Bohr's Institute. That was

really the great experience of my younger years, I would say. Ah, the

nuclear -- no, nuclear is not the word here, the atomic physicists,

those who worked on the model of the atom, theoretically under the

guidance of Bohr, who we called Copenhagen our Mecca felt like a

family. We have always been speaking of the family of atomic

physicists. It was not a very large family. I would say something like

30 people, 40 people, perhaps spread over the world, but coming

repeatedly to Copenhagen. And Bohr was the revered master of the whole

group. So I cannot speak about Bohr without expressing this sense of

reverence. Well we were all young. When I met Heisenberg this was quite

accidental. I met Heisenberg in 1927 when I was at the age of 14, and I

met Bohr when I was at the age of 19. And I came into that group, and

it was a group of very much interested young people. Interested in what

they knew was a unique opportunity, once in history to find, to find

these laws of nature, to reveal some of the basic laws of nature. And

we knew very well they had not been known before, and they were found

now. And no later generation had the chance of finding them because

they were found. It was like a Columbus situation. You can discover

America just once. And this was corresponding to this situation.

[END OF TAPE A01013]

Interviewer:

MAYBE YOU COULD TELL US THAT STORY.

Weizsacker:

Yeah. Well, uh the thing about which I'm -- the thing I'm going to

speak now is what I call the great tragedy in the friendship of Bohr

and Heisenberg, because they had been close friends, and they continued

being friends all through their life, but with this great difficulty of

which I am speaking now. That is, in September of '41, Heisenberg and

myself went to Copenhagen, and we had the intention that Heisenberg

should speak to Bohr on the problem of the nuclear weapon. We had been

talking about that long among us. And uh, the motive was that we

felt...it is quite possible that we are not going to be able to make

bombs, th-- as I said, but still, it is not quite impossible. And, on

the other hand, it is quite possible that the other side, the Western

Allies, will make a nuclear weapon, and this is a question on which it

would be wonderful to have uh, an understanding of the scientific

community of the family of atomic physicists, even during the war, an

understanding that none of us is going to make bombs. And we were not

certain whether it would be possible, but we said we should try; and

the one man who would be the only one to be a mediator in this kind of

talks, which could not be made directly because there was war, was

Niels Bohr, partly because he was Danish, mainly because he was the man

whom we all revered like a father. And so we went there. And Heisenberg

uh, started talking with him, they had a walk along Langelinie in

Copenhagen. And uh, when Heisenberg returned from that walk, which was

with purpose made in the fresh-- in the free air in order that there

should certainly be no uh, secret police uh hearing it Heisenberg came

to me and said, "I am afraid it was a complete failure. Bohr didn't

understand." And then I said, "Why?" And then Heisenberg said, "Well, I

started very cautiously speaking about this problem. And when he

finally understood that I was speaking about the actual possibility of

making nuclear weapons, he was so upset that he was not able anymore to

listen to the things which I really wanted to say. "This was

Heisenberg's description of the conversation ten minutes after it had

finished, or half an hour. Uh, now the way Bohr perceived it was

evidently that Heisenberg wanted to be fair to Bohr and to tell him at

least that we were making weapon-- uh, nuclear weapons. While

Heisenberg wanted to convey the message that it is possible in

principle to make them, but that we are probably not going to make them

because we are not able to, and there are-- that we wanted an

understanding that no-- nobody should make them. I have even heard the

version, quite late, recently which never came to my mind as a

possibility, that people thought, and Bohr might have thought, that

Heisenberg even had wanted Bohr to cooperate in the German effort of

making bombs. Now, this was so far from our ideas that, as I say,

before I heard that there are people who think that, it never came to

my mind. But in fact, I say, Heisenberg made a mistake. Heisenberg

ought to have started--

Interviewer:

HEISENBERG MADE A MISTAKE. GO AHEAD.

Weizsacker:

Heisenberg made a mistake. Heisenberg ought to have started -- we know

that afterwards, I mean, we always make our mistakes not understanding

what we are doing. Heisenberg ought to have started by saying, "My dear

friend, Niels Bohr, I am now telling you a thing which will cost my

life if anybody of the German uh, establishment learns that I did it. I

am going to tell you--" and then he would have started. But he started

cautiously. He thought Bohr would understand anyway. And Heisenberg had

that understandable tendency not to tell about military secrets if not

necessary, and so on. And this caution on Heisenberg's side made Bohr

suspicious ~ that's, in any case, my interpretation of the situation.

But what happened in the end was just that Bohr left Heisenberg with

exactly the opposite of what Heisenberg had wanted to achieve. With the

idea the Germans are eager to make bombs, and that is what Bohr

conveyed to our American friends when he came to America in '44. And I

think this may have be add-- or in '43 perhaps, I don't remem-- I don't

know exactly. And this may have added to the error on the American side

that the Germans were quite far in that work.

Britain Keeps German Physicists out of Russian and French Hands

Interviewer:

THERE WAS ONE THING I MEANT TO ASK EARLIER WHEN WE WERE TALKING ABOUT

THE CAPTURE--AND BEING TAKEN TO ENGLAND. DID YOU REALIZE AT THE TIME,

OR DID YOU THINK IT WAS TRUE, THAT THE UNITED STATES AND ENGLAND WANTED

YOU GERMAN PHYSICISTS OUT OF THE HANDS -- POTENTIALLY OUT OF THE HANDS

OF THE FRENCH AND THE RUSSIANS?

Weizsacker:

Well, I mean, this is an interpretation which was quite easy to uh,

draw as a conclusion after we had learned about Hiroshima. Before, we

knew nothing, because we didn't have the idea that bombs were so close

at hand. But when we had learned about Hiroshima and Nagasaki, and we

wondered why are we sitting here, well, since nobody had asked us to

work with the Americans or the English on this matter, it was evidently

not for that purpose that we were detained. But uh, that we should not

come into the hands of the Russians, that was a very natural idea to

us. And that even the French were considered not -- not quite reliable,

was a different question. But we were not so surprised learning that,

too.

Lessons of the Nuclear Age

Interviewer:

I JUST WANTED TO ASK YOU IN GENERAL ONE LAST QUESTION, JUST FOR YOUR

OWN POINT OF VIEW ABOUT-- WHAT HAS BEEN THE MOST SURPRISING DEVELOPMENT

TO YOU IN THE LAST 40 YEARS SINCE NUCLEAR WEAPONS HAVE EXISTED. I'M NOT

SURE I'M PHRASING THAT QUITE RIGHT. BUT, FOR EXAMPLE, ARE YOU SURPRISED

THAT NUCLEAR WEAPONS HAVE NOT BEEN USED SINCE 1945? OK, GO AHEAD.

Weizsacker:

Since my original reaction to the possibility of nuclear weapons was

that this will bring us into the uh, alternative of abolishing war or

ab-abolishing mankind, the thing which I did not foresee in that moment

was that there would be such a long stretch of decades in which this

question was not decided. I would have expected with youthful uh,

youthful uh, shortsightedness, that the whole thing would become--

would come to its consequence far earlier. And when I tried to say what

were the developments I did not foresee, it was that the very fear of

the nuclear weapon delayed the war between America and Russia -- I say

delayed because it can still come -- but in any case, when the nuclear

weapon was there, and especially when mutual assured destruction had

been invented, in the late '50s, it became clear that it was possible

for quite a while to stabilize the international situation by the help

of the threat of nuclear weapons. And this was a thing of which I had

not been sufficiently aware in the beginning. But then when I learned

it, I learned about this specific idea of mutual assured destruction in

'58, it became immediately clear to me that this was a very intelligent

idea, it would give us a breathing space of several decades, but

certainly it, it was not the final solution. So, this was what I had to

learn later on.

Interviewer:

OK. I WOULD JUST LIKE TO ASK YOU TO SUMMARIZE A COUPLE THINGS THAT

YOU'VE SAID IN A BRIEFER STATEMENT, SOMETHING LIKE, TO THE EFFECT THAT

YOU REALIZED IN 1939 THAT THE WORLD WAS ON THE...YOU KNOW, AND THE FACT

THAT HERE, NEARLY 50 YEARS LATER WE HAVEN'T SOLVED THAT PROBLEM IS YOU

KNOW...

Weizsacker:

Yeah. Well, I mean, I may say, I realized in '39, perhaps a bit earlier

than some other people, but certainly not earlier than I realized in

'39 that the possibility of a nuclear weapon, if it were realized,

would mean that we would have to abolish war, or we would abolish

mankind. What was surprising to me, what I had to learn later on, was

that there would be 50 years and who knows how many decades in which

this problem was not solved, because the nuclear weapon itself served

as a preliminary protection against starting a war. But preliminary, I

say. It is not the final solution.

[END OF TAPE A01014 AND TRANSCRIPT]

Transcript

Transcript

Series: War and Peace in the Nuclear Age

Raw Footage: Interview with Carl von Weizsacker, 1986

Contributing Organization: WGBH (Boston, Massachusetts)

AAPB ID: cpb-aacip/15-h707w67c1q

If you have more information about this item than what is given here, or if you have concerns about this record, we want to know! Contact us, indicating the AAPB ID (cpb-aacip/15-h707w67c1q).

Description

Credits: Interviewee2: Weizsacker, Carl Friedrich, Freiherr von, 1912-2007
Publisher: WGBH Educational Foundation

AAPB Contributor Holdings: WGBH
Identifier: 18a97cc53385ff8c9c47df0b3fe493875605c5f2 (ArtesiaDAM UOI_ID)
Format: video/quicktime
Color: Color
Duration: 00:00:00

Citations: Chicago: “War and Peace in the Nuclear Age; Interview with Carl von Weizsacker, 1986,” 1986-02-26, WGBH, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC, accessed May 12, 2024, http://americanarchive.org/catalog/cpb-aacip-15-h707w67c1q.; MLA: “War and Peace in the Nuclear Age; Interview with Carl von Weizsacker, 1986.” 1986-02-26. WGBH, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC. Web. May 12, 2024. <http://americanarchive.org/catalog/cpb-aacip-15-h707w67c1q>.; APA: War and Peace in the Nuclear Age; Interview with Carl von Weizsacker, 1986. Boston, MA: WGBH, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC. Retrieved from http://americanarchive.org/catalog/cpb-aacip-15-h707w67c1q