1 jan 1940 ano - 1940

Descrição:

May 3 - German troops occupy Norway, seizing the world's only heavy-water production plant at Vemork.
May 19 - Frisch and Rudolf Peierls submit a memorandum to the British government estimating the critical mass of uranium 235 needed for an atomic bomb and urging a bomb research project.
June 3 - German scientists fail to observe neutron multiplication in the reactor in Hamburg.
June 15 - Using the Berkeley cyclotron, Philip Abelson and Edwin McMillan demonstrate that neutrons captured by uranium 238 lead to the creation of elements 93 and 94, neptunium and plutonium.