13 February 1961
Dear Director Jahn:
I am pleased to have received your letter of 6 February, which reached me just after I had sent a letter to you.
I am glad that there is a strong fight against having atomic weapons on Norwegian soil, and that my former pupil Professor Bastiansen is taking a good part in it. My wife and I are very fond of Bastiansen - he is a fine man.
In three days now I shall fly to New York to present the new petition to Dag Hammarskjold and to make a public announcement about it. I think that my wife will not go with me, although she would like to do so. Circumstances are such that I shall have to take the plane at midnight Wednesday night, arrive in New York Thursday morning, present the petition to the United Nations, hold a press conference, and then catch a plane back to Los Angeles the same afternoon, Thursday. I have decided that, rather than have my wife submit to such a strenuous schedule for a night and day, it is better for me to go alone.
During the last month we have gathered the signatures of 38 Nobel Laureates and about 100 Fellows of the Royal Society, as well as about 100 members of the U. S. National Academy of Sciences, to this petition. We are now printing 10,000 copies, with space on each sheet for ten signatures, in order that a mass collection of signatures can be made.
I have been disturbed by the statements made by Professor Freeman J. Dyson of the Institute of Advanced Study, Princeton. His article "The Future Development of Nuclear Weapons" is, I think, not a well-balanced one, in that he discusses future developments that have extremely small probability, so far as the future of the next ten or twenty or thirty years is concerned.
I have made a copy of the article, and I enclose it. It is not a very good copy, but I think that you can read it.
First, let me answer your question as to what a strategic atomic weapon is.
During recent years the people who have been analyzing the question of the possible nature of nuclear war have introduced the term strategic atomic weapons and the term tactical atomic weapons. They seem to use these terms in the following way: strategic atomic weapons are the great weapons with great destructive power, which might be used to destroy the enemy country completely, smashing the cities flat and killing most of the people. Tactical atomic weapons are small weapons that might be used by an army in the field to attack another army, in such a way that the first army, after the attack, is able to move into the territory occupied by the second army I think that in a rough way one can say that strategic atomic weapons are weapons in the megaton class, like the 20-megaton bomb that was exploded by the United States on the first of March 1954; similar bombs have been exploded also by the U.S.S.R. and Great Britain. It is bombs of this sort that are carried in the Polaris rockets of the Polaris submarines and that are presumably also carried by the short range and long range rockets.
Tactical atomic weapons are weapons in the kiloton range. Probably the Hiroshima and Nagasaki bombs, with explosive energy equal to twenty kilotons of TNT, might be considered tactical atomic weapons, in that the range of great destruction would not extend more than a few miles from the hypocenter, and the danger from fallout and from neutron-induced radioactivity would not be very great after a few days. The military forces seem to be interested also in much smaller weapons. So far as I am aware, the smallest atomic bomb that has been tested had an explosive energy of only seventy tons of TNT. It contained, however, about as much plutonium as a 20-kiloton bomb. It had been adjusted in such a way that only about one percent or perhaps a still smaller fraction of the plutonium underwent the fission reaction during the explosion. The costs of one of these small atomic bombs is just about the same as that of a 20-kiloton bomb. The amount of explosive material is about the same, approximately ten pounds of plutonium, which costs $64,000.
The principal point that Dyson makes in his article is that it might be possible at some time in the future to achieve a fusion reaction on a small scale, using deuterium or tritium or lithium in some combination, with the reaction set off by use of ordinary high explosives (TNT) or in some other way, not yet discovered. The possibility of making small bombs that involve only fission is closely related to the problem of making fusion power plants.
Dyson in his article gives the impression that there is reasonable hope (or fear) that this might be achieved in the immediate future; that is, in the period of time that is significant with respect to the disarmament negotiations that are now going on among the great powers.
I think that Dyson's article is grossly misleading, in that it gives this impression. The fact is that physicists generally are rather pessimistic about the possibility of developing fusion as a source of power during the next 25 years. Moreover, the problem of developing fusion power is a far simpler one than that of developing a weapon based upon fusion alone.
Although, of course, I know that it is dangerous to make categorical statements about future discoveries, I myself feel that it is highly improbable that any development of the sort suggested by Dyson could be achieved in the next fifty years, even if the nations were to continue along the path of increasing military activity and increasing antagonism.
There are some possibilities that need to be considered, such as that of manufacturing in some way a supply of mesons that would bring the deuterons of heavy hydrogen so close together that they would undergo the fission reaction. The practical problems connected with the schemes of this sort that one might devise are so great as to make it seem now that they could never be overcome. Nevertheless, we cannot, of course, deny that there is a possibility that something will be discovered by the physicists during the next ten or twenty years that would change the situation.
There are some of the statements that Dyson makes that I agree with. I too feel that we cannot have permanent peace in the world until secrecy is abandoned by the U.S.S.R. However, it is expected that the negotiations toward disarmament would bring the abandonment of secrecy by the U.S.S.R., as one consequence of disarmament.
One important point about Professor Dyson's paper is this. He is talking about a possibility (in my opinion an extremely small possibility) that a nation such as the U.S.S.R., that continues to carry on vigorous research on weapons might succeed in making tactical weapons that depend upon fission only - small atomic bombs - and that it might make these weapons by the hundreds of thousands. This development would not change the situation at all with respect to the big bombs, which can destroy the United States and the U.S.S.R, and other parts of the world. These big bombs can now be made cheaply enough and in large enough quantity to do the whole job. The discoveries about fission that he foresees would not change the world situation with respect to big bombs at all, because the amount of plutonium required to explode a big bomb is so small that its cost is not an important factor.
Please let me know if there are any points about this matter that you would like me to discuss further.
Sincerely yours,
[Linus Pauling]
February
13, 1961
