What if your sat-nav was wrong by kilometres — every single day?
What if your sat-nav was wrong by kilometres — every single day? That's exactly what would happen without a correction most people have never heard of. GPS satellites carry atomic clocks so precise they can slice time into billionths of a second. But Einstein's relativity tells us clocks don't tick at the same rate everywhere. A clock moving fast, or sitting higher in Earth's gravity, ticks differently to one on the ground. For GPS satellites, both effects apply — and the result is that their clocks run slightly fast compared to yours. Leave that uncorrected, and your phone's position drifts by several kilometres within a single day. So engineers baked Einstein's equations directly into the system. Every time your phone finds you within a few metres, it's applying century-old physics. Follow Deep Field Vault for more of the universe hiding in plain sight.