msb@lsuc.UUCP (Mark Brader) (02/14/86)
With regard to this: > When the first nuclear bomb was exploded by the Manhattan project, there was > a pool started to predict the force of the explosion. One scientist predicted > that most of New Mexico would be wiped off the face of the Earth. And this: > ... I am not certain > about the historical development, but it seems to me that *at the > time* of the first atomic bomb, there was no way to exclude the > possibility of starting a chain reaction in the atmosphere or ground > with a reasonable degree of certainty. I would like to quote some passages from the book "Lawrence and Oppenheimer", by Nuel Pharr Davis (Simon and Schuster, 1968). To summarize briefly: The second quotation above is simply wrong. There was certainly betting on whether the atmosphere would explode, but it should be obvious that anyone who really believed that would be elsewhere or would have objected. It seems obvious to me that it was dark humor. Okay. The time is July 1942. Teller conceived the idea of the hydrogen bomb following a conversation with Fermi a few weeks before, and now he is presenting it for the first time. From pages 130-131: Going to a large blackboard in Oppenheimer's office, Teller computed the heat buildup. The final figure, he pointed out, was enough to "melt" the Coulomb barrier between light nuclei. Most specifically it would fuse deuterium ions into helium. ... The result, he concluded, would be a superweapon of unlimited power. The deuterium-deuterium reaction was thoroughly familiar. ... Nevertheless, Oppenheimer stared at the blackboard in wild surprise, and the other faces in the room, including Teller's, successively caught the same look. The heat buildup Teller had calculated was enough not only to maintain the deuterium reaction but also another between its reaction products and nitrogen. ... Teller had correctly calculated the heat production of a fission bomb; Oppenheimer saw it, with or without a deuterium wrapper, setting afire the atmosphere of the entire planet, and no one at the conference could prove he was wrong. Physicists are always exasperated when accused by outsiders of meddling with forces beyond man's puny comprehension. Nevertheless, those in the room were among the world's best, and that is exactly what they felt they had been doing. ... Oppenheimer suspended the sessions. He decided that Compton ought to know that the program he was directing seemed pointed toward igniting the air and ocean. ... Compton was vacationing at a lake cottage near Otsego, Michigan ... [and] by this time atomic leaders were forbidden to fly. Compton gave Oppenheimer directions for getting to Otsego by train and morning after next met him at the little station. Driving out to a deserted strip of beach, Compton listened to the story. He decided that the fission program would have to be abandoned unless Oppenheimer could definitely dispose of the heat question. "Better to be a slave under the Nazi heel", he summed up, "than to draw down the final curtain on humanity". Aside from such wisdom Oppenheimer had little to expect from the long train trip except that it gave him time to think. He checked and rechecked Teller's mathematics. The following week he reconvened the theoretical group. Bethe and the rest had also done some anxious checking. They confronted each other in one of the high moments of science history. ... ... Both [Oppenheimer and Bethe] surpassed Teller in mathematics. They found a mistake in Teller's figures. He had roughly but correctly calculated heat production in the bomb; he had overlooked certain aspects of heat radiation. Revised calculations by the whole group made ignition of a deuterium wrapper [i.e. the hydrogen bomb] seem possible but uncertain. How completely they ruled out the possibility of igniting air and water is an interesting question. On this point Teller, who was there, takes a different view from Compton, who was not. "We made absolutely certain -- I was more deeply involved in this than anyone else -- that no such catastrophe could occur", Teller says. Compton, on the other hand, told Pearl Buck that the physicists hemmed and hawed a long time. Then on his orders, he said, they computed a three-in-a-million chance, which he felt was low enough to be worth taking. The discrepancy between the two versions probably arises from the fact that certainty is a state of mind based on not having to depend on someone else's calculations. Allison, who was not there either, sided with Compton. "... I knew the doubts continued still in 1945. At the Metallurgical Laboratory we weren't supposed to tell the younger people. They kept making the discovery for themselves and coming to warn us." This three-in-a-million chance is presumably the same one referred to in this passage from pages 165 and 167: Oppenheimer ran into such varied problems of morale as to obscure the fact that he had one unvaried policy for dealing with them. This was to do what he could to let every scientist on the Mesa know what he knew. To inaugurate this policy he put Serber forward as his spokesman at a lecture series beginning on April 15 [1943]. ... [In the lectures, Serber said:] As for blowing up the earth by igniting the atmosphere, all calculations were against it. Still, he said, the true scientist should consider every possibility, including that of being mistaken. So many computations were involved that one had to admit a statistical probability of an error lurking somewhere among them unrecognized. The chance for an unexpected end to human affairs he would put at three in one million. It had to be deduced so tenuously that one might as well apply it to both the fission bomb and the more violent thermonuclear. In other word, the calculations showed that there was certainly no problem, so there was only the possibilty of repeated errors. Finally, this from pages 234-235: One of Fermi's traits that caused his colleagues to rank him in the genius class was his knack of extrapolating problem solutions that hid just beyond the range of mathematical proof. On ... July 15, [1945,] he gave a chilling demonstration. It began with a graceful compliment to Oppenheimer. If the bomb failed to go off, Fermi said, no one else could ever do better to make it go off, so Oppenheimer and the laboratory would have proved implosion impossible, and this would be the best of good news for mankind. Less obvious and more interesting, he went on, was a point about atmospheric ignition: long study of the possibility had put him in a position to handicap the odds on two contingencies: "I invite bets", he said, "against first the destruction of all human life and second just that of human life in New Mexico". [Gen.] Groves listened frowning. He had got up a series of press releases to cover all the eventualities he could foresee. The most drastic was that Oppenheimer and the other physicists who were to man the forward station would be wiped out; this he planned to explain by a statement that they had accidentally touched off an Army ammunition dump while enjoying a holiday at Oppenheimer's ranch. Now Fermi exasperated him by raising a contingency for which he was unprepared to account. He decided that Fermi was merely making a bad joke out of a desire to relieve tension. A good many of the senior physicists present felt that Fermi was not merely joking. Posted by Mark Brader
cipher@mmm.UUCP (Andre Guirard) (02/19/86)
In article <1115@lsuc.UUCP> msb@lsuc.UUCP (Mark Brader) writes: > ... long study of the possibility had put him in a position > to handicap the odds on two contingencies: "I invite bets", he > said, "against first the destruction of all human life and second > just that of human life in New Mexico". This was a "no-risk" bet, since if Fermi lost he would no longer be around to pay it off. > [Gen.] Groves listened frowning. He had got up a series of press > releases to cover all the eventualities he could foresee... Likewise, in the first case a press release would be superfluous. "In a posthumous press release, General Groves declined to comment on last week's destruction of all human life." It would be interesting to see what he would have had to say about the destruction of New Mexico. "And so I said to him, I said, how many times have I told you not to play with matches? And _now_ see what you've done! But there was no answer." -- /''`\ Andre Guirard ([]-[]) High Weasel \ x / speak no evil ihnp4!mmm!cipher `-'