Thanks for the replies. But guys and gals, explain to me like I'm a 6 year old please! My grasp of physics is tentative at best. I'm trying to get my head around some of these concepts by picking up my studies where I left off in college more years ago than I care to admit.
I'm not as interested...
In Einstein's thought experiment (if I understand it correctly) a person in a sealed elevator in space accelerating at 9.807 m/s2 would not be able to tell the difference between that and the effect of gravity on Earth.
Is there any sort of experiment the person in the elevator could do that...