@Brandon9000,
Einstein changed relativity after he visited Hubbel, now get over it......
Einstein's Greatest Blunder
The Cosmological Constant
Much later, when I was discussing cosmological problems with Einstein, he remarked that the introduction of the cosmological term was the biggest blunder of his life.
-- George Gamow, My World Line, 1970 [1]
Einstein's remark has become part of the folklore of physics, but was he right? He certainly had cause to feel rueful about the cosmological constant; he had introduced it into his general theory of relativity in 1917, as a last resort, to force the equations to yield a static universe. Even at the time, he apologized for doing so, because it spoiled the elegant simplicity of the field equations that he had struggled so hard to find. Of course the universe is not static, just as his original equations were trying to tell him; his blindness lost him the chance to make one of the great predictions in physics. Even worse, a little more analysis would have shown that his static universe was not stable, and would have started to expand or contract if its perfect equilibrium was disturbed in any way.
The most banal reason for Einstein's blunder might have been a simple failure to think through the consequences of his own ideas (in itself, very unusual for Einstein, but he was mentally and physically exhausted at this time). His 1917 paper finishes with the following:
It is to be emphasized, however, that a positive curvature of space is given by our results, even if the supplementary term [cosmological constant] is not introduced. That term is necessary only for the purpose of making possible a quasi-static distribution of matter, as required by the fact of the small velocities of the stars.
So Einstein was aware that his equations had non-static solutions, but he had convinced himself they were irrelevant because the stars were known to move very slowly compared to the speed of light. He seems to have missed the possibility of a coherent large-scale expansion or contraction, in which the motions of the stars near any observer would be negligible. If we can make this excuse in 1917, it fails in the 1920s when Einstein read and commented on the work by both Friedman and Lemaître which explicitly demonstrated the expanding solutions. Although Einstein originally thought there was an error in Friedman's paper, he was soon convinced that it was mathematically correct; but his comments on both papers were that the physics was "tout à fait abominable" (as he told Lemaître in person!).
