More on the bomb

Rudolf Peierls wrote about the decision to use the atomic bomb in Making It New York Review of Books 11/05/87 issue (link is behind subscription, unfortunately), reviewing The Making of the Atomic Bomb (1987) by Richard Rhodes.

Since I only occasionally do Science Friday, I'll let this quotation count as a Science Friday entry:

An introductory chapter is devoted mainly to Leo Szilard's realization in 1933 that the existence of the neutron, just discovered, might make a chain reaction possible. He expected that there might be nuclei which, on being hit by a neutron, would give up further neutrons, and that energy would be released in this process. These neutrons would hit other nuclei, and the result would be a chain reaction, which would continue until the number of suitable nuclei was reduced below a critical amount, or the material was dispersed. Szilard expected that the nucleus of beryllium might serve for this purpose, but this was a misguided idea. Such a result, Szilard felt, would justify the speculations by H.G. Wells and others about the liberation of atomic energy on a large scale for industrial and military purposes, although Lord Rutherford—who had discovered the atomic nucleus—had called such speculations "moonshine." Szilard was, in fact, not the only one to see this point; others did so, including the Soviet theoretical physicist Lev Davydovich Landau. But in the early Thirties nobody knew by what nuclear process such a chain reaction could be implemented.

This reference by Peierls to Robert Oppenheimer reminded me again that "Oppie's" greatest talent was not as a physicist per se, but as a manager.  He had to run what we would now call a "matrix organization", bringing together people in ever-changing combinations to achieve their tasks.  He had to satisfy both the scientists working on the Manhatten Project and the military and civilian officials who were running the war.  And to do it all under conditions of the most extreme secrecy:

Oppenheimer built up the Los Alamos Laboratory on a mesa in New Mexico for studying the fast-neutron physics and bomb design—and later for bomb manufacture. We are told how he inspired a large number of first-rate scientists with a sense of urgency and common purpose, and how he managed to keep down the natural friction between the civilian scientists and the army officers who were running the place.

Peierls describes some of the considerations on the decision to use the bombs on Japan in August 1945:

Meanwhile there had been many discussions about what to do with this weapon. There was little doubt that it would be used on Japan as soon as it was available. One argument for this was undoubtedly that the expenditure incurred by the project, without the knowledge of Congress, by now added up to $2 billion, and the military would be blamed if this had made no contribution to the war. More substantially, the argument was that the use of this weapon would surely lead to the surrender of Japan, thus obviating the need for an invasion, which, it was said, was going to cost more lives (even more Japanese lives) than the bomb.

The idea of a demonstration in the presence of invited observers was considered, but rejected. A scientific panel made up of Lawrence, Fermi, and Oppenheimer, among others, concluded in July 1945 that "we can propose no technical demonstration likely to bring an end to the war; we see no acceptable alternative to direct military use." There was also as yet no complete confidence in the reliability of the design. The Trinity test, it was said, was not conclusive proof that the bomb would explode when dropped from an airplane, and if the Japanese were told of the weapon and it then failed to explode, this would be exploited by Japanese militarists. The obvious alternative of dropping a bomb unannounced on a thinly populated area of Japan, to demonstrate its effect, was not, as far as I know, ever considered. It would have involved killing some people and destroying some buildings; the effects of an explosion in the desert, as at Alamagordo, were stunning to the experts, but would not mean much to the layman.

He also reminds us of the "strategic bombing" context:

In reporting the discussions that led to the decision to drop the bomb on Hiroshima and Nagasaki, Rhodes reminds us of the history of the terror bombing of cities. From the early widespread indignation at the bombing of Guernica and Rotterdam, attitudes changed to such an extent that the deliberate fire raids on Hamburg, Dresden, and Tokyo were considered an acceptable form of warfare. Without this background theatomic bomb raids on Japan might not have taken place.

In summarizing Rhodes' view, Peierls expresses some of his own reservations about the decision made:

He evidently does not think highly of the process by which the use of the bombs was decided. The ancient city of Kyoto was removed from the list of targets, he notes, only by the personal insistence of Secretary of War Stimson, who happened to be familiar with its cultural significance. The conduct of the war, he says, had been "stupid and barbarous," and "the barbarism was not confined to the combatants or the general staffs. It came to permeate civilian life in every country" and "was perhaps the ultimate reason Jimmy Byrnes, the politician's politician, and Harry Truman, the man of the people, felt free to use and compelled to use a new weapon of mass destruction on civilians in undefended cities." I happen to share the author's opinions in all these respects.

[Additional note 08/06/05: The author of that article, Rudolf Peierls, along with  Otto Frisch were the first to calculate that the critical mass of uranium needed for an atomic bomb was a relatively small amount, a key finding in making the production of such a weapon feasible.  It was previously thought that tons would be required.]