“What this meant,” Freedman explains, was that there was “a one-in-one-million chance that, given how much hydrogen [is] in the earth’s atmosphere, when Castle Bravo exploded, it could catch the earth’s atmosphere on fire. Some scientists were extremely nervous. Some made bets about the end of the world.” This was not Freedman’s first atmospheric nuclear bomb test. By 1954 he had worked on more than
