I watched a documentary on Einstein awhile back. Fascinating. He wanted to prove gravity was really the curvature of space/time and had to find a way to prove it. Space, he theorized, was a 'fabric' which was bent by the objects in it. The larger objects would warp the space arounfd it and smaller objects would orbit it because they got trapped in this curvature. But how to prove this? He then realized that by ingeniously using our own sun during a solar eclipse, light from behind the sun would appear to bend. This went against his hero Isaac Newton's theory that gravity was a force that pulled us down. Most everyone scoffed at this radical new idea of Einstein's except a guy named Eddington. Eddington believed in Einstein and agreed to photograph a solar eclipse and take measurements. Obstacles such as weather and war stalled Eddington's works but he finally found a good spot to photograph a solar eclipse eventually. Eddington was able to prove Einstein's theory of General Relativity. Oddly enough, Einstein didn't win the Nobel Prize for this but did earlier for his "Special Theory of Relativity" where he showed light was made of photons, and not beams. He gave the money from that prize to his wife so that she would allow them to divorce, freein him to marry his cousin.
Some of this might be a little off but this is my best recollection.
Einstein later said that his help in creating the Atomic Bomb was "single greatest mistake" of his life.