Happy Valentine’s Day, 1989. The US Air Force just gave you a $12 billion gift… and then they immediately broke it.
Thirty-seven years ago today, a Delta II rocket roared off the pad at Cape Canaveral, carrying the first Block II GPS satellite. This wasn’t just another piece of space junk. This was the birth of the “Global” in Global Positioning System. But there was a catch that sounds like a tech enthusiast’s nightmare.
The Tech: Time is Literally Relative
To make GPS work, you need two things: incredibly precise timing and a deep understanding of Einstein. Each satellite carries Rubidium and Cesium atomic clocks, accurate to within nanoseconds.
The Relativity Problem: Because these satellites are screaming through orbit at 14,000 km/h, time actually moves slower for them (Special Relativity). But because they’re further from Earth’s gravity, time also moves faster (General Relativity).
The Result: The clocks on board have to be offset by 38 microseconds per day just to stay in sync with us ground-dwellers. Without that math, your Uber would be miles off within 24 hours.
The “Broken” Feature: Selective Availability
Here’s the kicker: The military didn’t want civilians having that much power. They intentionally introduced noise into the signal—a feature called Selective Availability. It meant your GPS could only get you within 100 meters. It was like having a high-end gaming PC but being forced to run it through a VGA cable.
Legacy: It wasn’t until 2000 that the noise was turned off, giving us the blue-dot precision we take for granted. Today, GPS is the invisible utility that runs our power grids, our financial markets, and—most importantly—your DoorDash delivery.