Theory links space and time

German physicist Albert Einstein (1879-1955) won the Nobel Prize for physics in 1921. After leaving Nazi Germany, he went to the United States and became an American citizen in 1940.

He is best known for his work on relativity.

Einstein's research demonstrated that earlier assumptions about time and space were inaccurate. According to Einstein, observers moving at great speed would make different measurements about time in each other's systems. Thus, Einstein said space and time were not separate and absolute entities, but formed a four-dimensional continuum, called space-time. His work led to the theory of the continually ex panding universe.