> needing no further experimental work General relativity is an incredibly impressive theory, even more so when you take into account how few experimental obse

> needing no further experimental work General relativity is an incredibly impressive theory, even more so when you take into account how few experimental observations were required to formulate it. Basically "the speed of light is the same in any frame of reference" and "being in a gravitational field is (locally) indistinguishable from being in an accelerated reference frame". (For the second one, think about being in a rocket ship accelerating at a constant rate... you feel a force pushing you into the floor, just like you would if you were standing on the Earth's surface.) If those two things are true, then GR is the only logical conclusion... but we might have gone another 100 years without reaching that conclusion if it hadn't been for Einstein.