GPS time machines

[PRB]

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.

[Wing_Z]

General Relativity says the clocks on board will appear to tick faster, seen from earth.
Special Relativity also comes into play: because the satellites are moving relative to us (14,00km/h) it makes the clocks onboard appear to tick more slowly.
The guys designing the GPS system knew their Relativity and added the two effects;
the nett sum is faster, so they slow them down before launch.
Once they're up there, they appear to an earthling to tick at the correct speed.

The mind boggles...