Comments on: What Bohr told Beria

By: Soviet drawings of an American bomb | Restricted Data

Soviet drawings of an American bomb | Restricted Data — Fri, 30 Nov 2012 15:26:24 +0000

[...] about where this information was coming from. The document itself was written by Igor Kurchatov for Lavrenty Beria, dated June 4, [...]

By: Spruce

Spruce — Thu, 06 Sep 2012 10:13:46 +0000

At least to me that reads like a very simple question and even stranger for that. Basically, that question seems to come down to “is implosion used in the bomb?” And if that is indeed the question, Bohr’s answer is obvious and utter lie.

That question seems like a check question. It is asking of something Soviets know from their own source, but is highly classified by US. Thus, a great question for evaluating whether Bohr is willing to provide more sensitive information.

By: Alex Wellerstein

Alex Wellerstein — Thu, 02 Aug 2012 18:50:19 +0000

Somewhere (I think in an oral history that was done with Robert Bacher?) I read of an account where General Groves and Richard Tolman were traveling with Bohr on a long train ride (maybe to Los Alamos). Both agreed that Bohr needed to be supervised on the entire trip — they didn’t dare leave him to his own devices. Tolman initially agreed to sit with Bohr. Eventually he got so frustrated that he found Groves and told him he was giving up. Groves said that he didn’t want to sit with Bohr; Tolman said back to him that he was the General, so Bohr was his problem to deal with!

By: Jacob Hamblin

Jacob Hamblin — Thu, 02 Aug 2012 15:04:02 +0000

Thanks for the response. When I first encountered Bohr’s tiresome politics (as an undergrad reading Sherwin’s A World Destroyed in a Larry Badash seminar) I remember being baffled that he was allowed to go back to Copenhagen so soon, and being sympathetic to Churchill’s instinct to lock him up!

By: Alex Wellerstein

Alex Wellerstein — Thu, 02 Aug 2012 13:54:14 +0000

It could be a reference to a tamper, but it’s hard to know.

By: semisonic

semisonic — Thu, 02 Aug 2012 13:40:11 +0000

22. Question: Is the phenomenon of overcompression of the compound under the influence of the explosion used in the course of the bomb explosion?

Could this be an exploration of materials used that help to contain the first split-seconds of initial reaction so that the reaction can be more efficient – before the bomb casing disintegrates?

By: Alex Wellerstein

Alex Wellerstein — Thu, 02 Aug 2012 12:59:13 +0000

The thing is, in 1945, the Super still seemed pretty feasible, because none of the details were worked out. One of the scientists at the time — I think it was Carson Mark — put it something like this: the classical Super was a very difficult thing to prove that it wouldn’t work. It wasn’t until the computing power of the early 1950s that they were able to really say, “this isn’t feasible, you can’t just put an atomic bomb next to fusion fuel and have it ignite” (which non-coincidentally led to coming up with Teller-Ulam). I think Bohr’s total dismissal of it is not on a technical basis. The attitudes towards the technical feasibility Super at the end of World War II were very positive; it was only after more careful study that it began to be thought to be infeasible.

It’s not too different from Groves’ dismissal of it when asked by the press at Oak Ridge — a non-denial that effectively constitutes a denial.

Put another way: again and again Bohr seems to say something is unimportant or irrelevant when it appears more likely that he just doesn’t want to talk about it. It’s a clever response, because an outright denial to talk about something likely draws more interest to it than a casual shrug. (Or, in Bohr’s case, a tiresome lecture on politics.)

I suspect Bohr must have known the number of neutrons emitted on fission of U-235 and Pu-249. It’s the sort of detail that the-guy-who-came-up-with-the-theoretical-model-of-fission probably would have found out. Especially since a number (but not the number) for U-235 was already something published prior to the Manhattan Project (Joliot claimed it was 3.5 in 1940; it’s more like 2.5).

It’s hard for me not to see #19 as a gentle probing to see if he’ll cooperate, and his lack of cooperation is apparent. Anyone working with the technical side of things at Los Alamos would have known that U-235 and Pu-239 were in the bombs; Bohr’s feigned ignorance has to be a total lie. Publicly, the fact that they enriched U-235 and also produced Pu-239 was well-known (published in the news accounts, Smyth Report, etc.), so it wouldn’t have been any stretch.

One thing I didn’t mention is that Bohr was notoriously hard to understand — he mumbled, he digressed, he pontificated, he worried endlessly about having every word perfectly chosen. One doesn’t get too much of a sense of that from the transcript other than the pontificating. I wonder how much difference there is from the transcript and what he actually said — I suspect quite a lot of interpretation went into interpreting this and transcribing it into Russian, which might explain why some of the answers seem garbled.

By: Jacob Hamblin

Jacob Hamblin — Thu, 02 Aug 2012 07:42:52 +0000

Fascinating as usual. Really great analysis and fun to read. I wondered though whether Bohr is really hiding the number of neutrons. Can’t he just be emphasizing that you need more than two for there to be a chain reaction, the sine qua non of the whole deal? I agree the answer to question 19 is really odd, and it makes me wonder if I have misunderstood a great deal about what people knew when. Surely his answers must need to be credible, so it is perplexing. As for the super, your take is fair enough but he could also simply be expressing skepticism that it could be done, right? Or simply pointing out that it had not been realized, which was true. There was ample room for skepticism in 1945, before Teller-Ulam. And he doesn’t deny the possibility of making the A-bomb bigger on technical grounds. They are already big enough for the job, he seems to say. They are unreasonable.