Albert Einstein, German-Swiss-American mathematician and physicist.

Albert Einstein, German-Swiss-American mathematician and physicist. Einstein's (1879-1955) main contribution to science was the theory of relativity, regarded by many as the most important theory in the history of physics. His special (1905) and general (1916) theories of relativity proved the concept that time does not exist at the same rate for everyone and everything. Special Relativity produced the equation which expresses the equivalence between matter and energy: E=mc squared. In 1921, Einstein received the Nobel Prize for Physics. His Jewish origins meant that he had to leave Germany during the Nazi period, emigrating to the USA and taking American citizenship. (Photo by Oxford Science Archive/Print Collector/Getty Images)