A constellation of satellites carrying atomic clocks that lets any receiver on Earth calculate its precise location and the exact time, for free, at any moment. Built as a US military navigation system, GPS was opened to civilian use after a 1983 airline disaster, its full accuracy unlocked in 2000. It dissolved one of the oldest human problems — knowing where you are — into invisible infrastructure, then quietly wove its timing signal into the hidden rhythm of financial networks, power grids, and precision weapons, making modern civilization dependent on a faint pulse from orbit.
On May 1, 2000, at midnight, President Clinton flipped a switch and civilian GPS receivers around the world suddenly got ten times more accurate. For seventeen years, the US military had deliberately scrambled the signal available to ordinary people, limiting their accuracy to roughly 100 meters. The moment the scrambling stopped, a hand-held device could pinpoint your location to within ten meters — anywhere on Earth, any time of day, in any weather, for free. Nobody who held one of those receivers that night could have fully grasped what that accuracy would eventually become: the timing backbone of global finance, the heartbeat of the power grid, the guide for a drone strike ten thousand miles away. A military system, briefly switched on for the rest of humanity, had just become the hidden clock of civilization.