How GPS actually works

GPS satellites carry atomic clocks deliberately set to run slightly slower than ground clocks before launch. This compensates for relativistic effects predicted by Einstein: weaker gravity at orbital altitude makes clocks run faster, while orbital velocity makes them run slower. The net effect is a gain of 38 microseconds per day, which at the speed of light translates to ~11 km of positioning error. Engineers correct this by adjusting the satellite clock frequency from 10.23 MHz to 10.22999543 MHz, effectively baking Einstein's general relativity into everyday navigation infrastructure.