Alexander Friedmann

Alexander Friedmann

Ignoring the cosmological constant as an unnecessary “fudge factor,” Friedmann solved Einstein’s dilemma of how to account for the fact that the universe had not already collapsed by supposing that it began with an initial expansion, and that the effect of gravity would be to gradually slow the expansion. He predicted that if there were enough mass in the universe the expansion would eventually reverse; while if the mass were too little the universe would continue to expand forever. And if the amount of mass were just right the expanding universe would slow down and come to a virtual standstill, neither collapsing further nor infinitely expanding.