Do you people realize that the GPS system, based, among other things, on hyper accurate time signals from the satellites, must account for relativity? Yes, that Relativity, the one the Einstein figured out. The one where he said that time passes more slowly the closer you are to a gravity source, like, say, a planet. Not appears to pass more slowly, but does pass more slowly. Yeah right. Silly theory from an egg-headed scientist, right? But... If they don't figure into the calculations the amount that Eisenstein said to figure in, the position errors would grow over time such that the whole system would be useless in a week. That's amazing. The satellites are farther away from the source of gravity than we are, so time passes faster on board the satellites, see? Amazing.
