A chip in your pocket can pinpoint you anywhere on Earth using clocks orbiting 20,000 km overhead — and it would be wrong by miles without Einstein. This short course explains the satellite constellation broadcasting time and position, how your phone finds itself by measuring distances (trilateration), why it takes atomic clocks accurate to nanoseconds, and the relativity correction GPS builds in to keep from drifting 10 km a day.
A chip in your pocket can pinpoint you anywhere on Earth using clocks orbiting 20,000 km overhead — and it would be wrong by miles without Einstein. This short course explains the satellite constellation broadcasting time and position, how your phone finds itself by measuring distances (trilateration), why it takes atomic clocks accurate to nanoseconds, and the relativity correction GPS builds in to keep from drifting 10 km a day.
