Fission, used in war

In 1945 the United States detonates a fission bomb over Hiroshima and then Nagasaki. The physics is a chain reaction in uranium or plutonium, worked out in the Manhattan Project. A reactor, which uses the same chain reaction slowly, had already been demonstrated by Fermi in Chicago in 1942.

The contribution on a technology tree is concentrated energy from the nucleus, and the political fact of a weapon that can destroy a city. Civilian nuclear power comes later and remains a fraction of world electricity. It is not an ancestor of the transistor or the robot.

This card is a side branch on purpose. The path to computers runs through radar, vacuum tubes, and the transistor, which were pushed by the same war but are a different invention. Fission does not lead to the chip.

The year is the use in war, not the discovery of the nucleus, which is decades earlier.