GPS satellites experience time faster than we do on Earth.

The time difference experienced by GPS satellites is a real-world application of Albert Einstein's theories of relativity. According to General Relativity, gravity warps spacetime, meaning clocks closer to a massive object like Earth tick slower than those further away. At an altitude of approximately 20,200 kilometers, GPS satellites experience much weaker gravity, causing their clocks to run faster by about 45 microseconds per day.However, Special Relativity also plays a role because the satellites are moving at speeds of roughly 14,000 kilometers per hour. This high velocity causes time to slow down for the satellites by about 7 microseconds per day relative to a stationary observer on the ground. When you combine these two effects, the net result is that satellite clocks gain approximately 38 microseconds every single day.To ensure the system remains functional, the atomic clocks on board the satellites are programmed to tick at a slightly slower frequency before they are even launched. Specifically, they are set to 10.22999999543 MHz instead of the standard 10.23 MHz used on Earth. This precise adjustment allows the signals to synchronize perfectly with ground-based receivers.If the U.S. Department of Defense and the Global Positioning Systems Directorate did not account for these relativistic effects, the errors would accumulate rapidly. Within just 24 hours, the positional data provided by the satellites would drift by more than 10 kilometers. This would make the entire system useless for navigation, aviation, and military operations.