Without a single equation, GPS fails within hours.
GPS satellites carry atomic clocks so precise they lose less than a second over millions of years. But there's a problem — Einstein showed that clocks don't all tick at the same rate. Speed slows a clock down; weaker gravity speeds it up. The satellites sit high above Earth, where gravity is weaker, and that difference matters enormously. Left alone, their clocks would drift just enough to throw your position off by several kilometres before the day is out. So engineers did something remarkable: they baked Einstein's equations directly into the system. Every position fix your phone calculates has already been corrected for relativistic time drift. General and special relativity aren't just abstract physics — they're quietly running inside infrastructure billions of people use every morning. Follow Deep Field Vault for more of the universe hiding in plain sight.