Albert Einstein (March 14, 1879 – April 18, 1955) was a German-born theoretical physicist, who is widely regarded as the greatest scientist of the 20th century. He proposed the theory of relativity and also made major contributions to the development of quantum mechanics, statistical mechanics, and cosmology. He was awarded the 1921 Nobel Prize for Physics for his explanation of the photoelectric effect in 1905 (his "miracle year"). (Read more...)
Photo credit: Oren Jack Turner, Source: Library of Congress.