Clocks That Lie on Purpose

Every satellite in the Global Positioning System is carrying a lie. Not a malfunction. Not a defect. A precisely calculated falsehood, programmed into its atomic clock before the rocket ever leaves the ground, because the alternative, a clock that tells the truth on the launchpad, would become wildly, dangerously wrong the moment it reached orbit.

This is the strange, true story of how that lie was built, and why it had to be.

In 1905, a patent clerk in Switzerland proved that…