EXCERPT The year is 1950 and a group of nuclear physicists sporting tweed blazers are walking to lunch. They are about to have a conversation that will become something of a legend in scientific circles. Here at the Los Alamos Ranch School, set against the majestic backdrop of the Rocky Mountains, each of them has lately played their part in ushering in the atomic age, as participants in the epoch-making Manhattan Project. This afternoon, spirits are high. The party are joking about a cartoon in the New Yorker that offers an unlikely explanation for a recent spate of stolen public trash cans across New York City. The cartoon depicts little green men, complete with antennae and guileless smiles, returning to their home planet to assiduously unload the stolen bins from their flying saucer. By the time the scientists sit down to eat in the mess hall, housed inside a sizable log cabin on the Los Alamos site, one of their number has turned the conversation to more serious matters. ‘Where, then, is everybody?’ he asks. They all know that he is talking about extraterrestrials—and that, as far as he is concerned, this urgent question is no laughing matter.…