J. Robert Oppenheimer: When I came to you with those calculations, we thought we might start a chain reaction that would destroy the entire world.
Albert Einstein: I remember it well. What of it?
J. Robert Oppenheimer: I believe we did.
J. Robert Oppenheimer: They won't fear it until they understand it. And they won't understand it until they've used it. Theory will take you only so far.
Edward Condon: Why would we move out to the middle of the desert for two to three years?
Leslie Groves: Why? How about because this is the most important fucking thing to ever happen in the history of the world.
J. Robert Oppenheimer: Since when are you British?
Klaus Fuchs: Since Hitler told me I wasn't German.
Leslie Groves: Are you saying that there's a chance that when we push that button... we destroy the world?
J. Robert Oppenheimer: The chances are near zero.
Leslie Groves: Near zero?
J. Robert Oppenheimer: What do you want from theory alone?
Leslie Groves: Zero would be nice.
Answer: The short version is "no, not really". Much like in the film, the possibility was considered, a lot of calculations were done, and it was agreed by everyone privy to them that the chance was basically zero. Also like in the film: "what do you want from theory alone?" - it couldn't be guaranteed to be absolutely zero, but then the chance of almost anything happening is never absolutely zero. A 1946 report by three of the scientists stated: "whatever the temperature to which a section of the atmosphere may be heated, no self-propagating chain of nuclear reactions is likely to be started. The energy losses to radiation always overcompensate the gains due to the reactions."