Einstein didn't work on the nuclear bomb at all. According to https://www.amnh.org/exhibitions/einstein/peace-and-war/the-manhattan-project https://www.amnh.org

Einstein didn't work on the nuclear bomb at all. According to https://www.amnh.org/exhibitions/einstein/peace-and-war/the-manhattan-project https://www.amnh.org/exhibitions/einstein/peace-and-war/the-..., he wrote that famous letter to Roosevelt and was later denied the necessary security clearance.