Albert Einstein (1879-1955) was a theoretical physicist who contributed to the theory of a Special Relativity and formulated the theory of General Relativity. He also contributed to the study of Photoelectric Effect, Brownian Motion and Bose-Einstein Statistics. He was critical of quantum mechanics and has proposed the EPR-Paradox in attempt to disprove it. The last fifteen years of his life were spent in spent unsuccessfully searching for a Unified Field Theory. Born in Germany, he won the Nobel Prize for his work on the Photoelectric Effect in 1921.[1] He immigrated to the United States in the late 1930s where, upon the urging of a colleague in physics, recommended that President Franklin D. Roosevelt develop an atomic bomb project.[2]
Einstein's best-known scientific work is his 1905 papers on Special Relativity. The theory of relativity had already been published by Hendrik Lorentz and Henri Poincaré. Einstein's contribution was to give a description of the Lorentz-Poincare theory without reference to the luminiferous aether, and to clarify some of the physical consequences of the theory.
Einstein then wrote a series of papers applying relativity to gravity using the mathematics of Riemannian Geometry, resulting in General Relativity. Much of the actual mathematics of general relativity was worked out by Marcel Grossman, David Hilbert, and others. Einstein's main contribution was to give an alternate derivation of the field equations, and to apply them to explain an anomaly in the advance of the perihelion in Mercury's orbit.
Sir Arthur Eddington popularized General Relativity by publishing an explanation of it and by attempting to prove the theory experimentally in a dramatic test. Eddington embarked on a highly publicized trip into the Atlantic Ocean off Africa in order to observe the bending of starlight passing nearby the Sun during the total solar eclipse of May 29, 1919. Eddington returned with a declaration that he had proven Einstein's theory of General Relativity, making Einstein extremely famous, when in fact he had selectively used data to attain this result. Eddington was passed over for the Nobel Prize.
Cosmological Constant
Einstein revised his work on General Relativity to include a 'fudge-factor' which he termed the Cosmological Constant. He was trying to account for the apparent steady-state nature of the universe.
Edwin Hubble, of whom NASA's famous Hubble Space Telescope is named in honor, later convinced him otherwise. At one point he had Einstein actually making direct observations alongside him, and Hubble's findings showed conclusively that the universe was indeed expanding, as predicted by certain solutions of GR's field equations in the absence of a cosmological constant. Einstein recanted his original philosophy, and accepted as true the notion of a changing universe having a definite beginning.
He later said of his Cosmological Constant, "It was the biggest blunder of my life."
An interesting end-note on this term: Principle investigators from Princeton University first published findings in 1998 apparently revealing an accelerating expansion for the universe[3]. Because this initially seemed like it might be a sort of 'anti-gravity' effect (similar in concept to Einstein's original notion), it briefly became quite popular for scientists to dub the phenomenon the 'Cosmological Constant' as well. For more information, see: Dark Energy.