 The project's roots began in 1939 when, at the urging of Leó Szilárd, Albert Einstein signed the Einstein–Szilárd letter to US president Franklin D. Roosevelt expressing his concerns that Nazi Germany may be trying to develop nuclear weapons.Albert Einstein (1879–1955) was a theoretical physicist and philosopher, widely regarded as one of the most influential and best known scientists and intellectuals of all time.A German-Swiss Nobel laureate, Einstein is often regarded as the father of modern physics.