Einsteins Biggest Blunder

When Albert Einstein formulated General Relativity in 1915, he was not aware the Universe was expanding. Large scale structure in the form of galaxies was not known and all fuzzy luminous nebulae were considered basically similar and within stellar distance scales. Only with Hubble work in 1930 came the realization some of those nebulae were in fact island universes, and that they were not only very far, but also receding from us at enormous speeds. This was not known for Einstein, and since gravitation exerts its influence up to infinity, it was natural for him to postulate some force working in the preservation of an apparent equilibrium among matter, preventing universal collapse. This is why he postulated the Cosmological Constant, symbolized by the Greek letter Lambda, and included a term accounting for it in the field equations. Once universal expansion was discovered, the need for an unknown repulsive agent could be dropped and Einstein dismissed the Cosmological Constant as his "biggest blunder".