GPS Requires Einstein's Theory of Relativity to Work

The satellites powering GPS run faster clocks than those on Earth — because time passes more slowly in stronger gravitational fields (general relativity) and faster for objects moving at high speed (special relativity). Without corrections for these relativistic effects, GPS coordinates would drift by around 10 kilometres per day. Einstein's abstract physics is baked into every turn-by-turn direction.

Source: American Journal of Physics — Neil Ashby (2002)