# Einstein Albert Einstein (1879-1955), German physicist, US citizen from 1940: formulated the theory of relativity; awarded 1921 Nobel prize for physics. Although complete understanding of his theory of relativity requires a knowledge of the most exotic branches of mathematics, these are some of its basic points: (1) Time is not an absolute. The faster a body moves, the slower its clock runs. A minute on Earth may pass in fifty-nine seconds or sixty-one seconds on planets traveling at speeds different from that of Earth. (2) The speed of light remains constant in all frames of reference. Whether you are moving toward a light source or away from it, the light will still reach you at the same speed (186,000 miles per second). (3) All motion is relative. Therefore, there can be no such thing as absolute rest. (4) Moving bodies acquire mass as they increase in speed. The faster a body travels, the heavier it becomes. As a body approaches the speed of light, it adds mass very rapidly. If it were to reach the speed of light, its mass would become infinite. If this were true it could be seen that no body could ever travel faster than the speed of light. The additional weight acquired by an accelerating body would make penetration of the light barrier impossible. (5) Mass and energy are mutually convertible. See also theory of relativity in this glossary.