(Inside Science) -- In "Inside the Third Reich," a memoir by Albert Speer, the former minister of armament of Nazi Germany recalls an exchange he had with the physicist Werner Heisenberg and Adolf Hitler:
"Heisenberg had not given any final answer to my question whether a successful nuclear fission could be kept under control with absolute certainty or might continue as a chain reaction. Hitler was plainly not delighted with the possibility that the earth under his rule might be transformed into a glowing star."
By 1942, Germany had mostly given up on trying to develop a nuclear bomb, largely due to logistical reasons, while the U.S. plowed ahead with the Manhattan Project and became the first nation equipped with nuclear weapons. But how serious was the concern that these bombs might set the entire world on fire?