Albert Einstein Einstein did not return to Germany. He settled in the United States and became an American citizen in 1940. On the eve of World War II, he endorsed a letter to President Franklin D. Roosevelt alerting him to the potential development of "extremely powerful bombs of a new type" and recommending that the US begin similar research. This eventually led to the Manhattan Project. Einstein supported the Allies, but he generally denounced the idea of using nuclear fission as a weapon. He signed the Russell–Einstein Manifesto with British philosopher Bertrand Russell, which highlighted the danger of nuclear weapons. He was
Albert Einstein in popular culture Albert Einstein in popular culture Albert Einstein has been the subject of, or inspiration for, many works of popular culture. On Einstein's 72nd birthday on March 14, 1951, United Press photographer Arthur Sasse was trying to persuade him to smile for the camera, but having smiled for photographers many times that day, Einstein stuck out his tongue instead. This photograph became one of the most popular ever taken of Einstein, often used in merchandise depicting him in a lighthearted sense. Einstein enjoyed this photo and requested UPI to give him nine copies for personal use, one of which he signed