"Teller’s calculations were faulty; his prototype would have been a dud. This was first noticed by Stanislaw Ulam... Having shown that the Teller scheme was a nonstarter, Ulam produced, in his typically absent-minded fashion, a workable alternative. “I found him at home at noon staring intensely out of a window with a very strange expression on his face,” Ulam’s wife recalled. “I can never forget his faraway look as peering unseeing in the garden, he said in a thin voice—I can still hear it—‘I found a way to make it work.’”"