Every GPS satellite is launched with a clock deliberately set to run slow, because Einstein's relativity speeds it up by about 38 microseconds a day once in orbit — and without that built-in correction, your phone's location would drift by roughly ten kilometres a d - Space Daily

Every GPS satellite is launched with a clock deliberately set to run slow, because Einstein's relativity speeds it up by about 38 microseconds a day once in orbit — and without that built-in correction, your phone's location would drift by roughly ten kilometres a d Space Daily