When Einstein developed general relativity the closest thing to a practical application that could even be imagined at the time was a slightly more precise description of where to look for the planet Mercury in the sky, and yet now we’d all be literally lost without it.
Anyway: fund basic research.
GPS satellites move at 1/100000 the speed of light, causing their clocks to tick slower by 7 microseconds per day, and orbit at a height that makes their clocks tick faster by 45 microseconds per day. Two relativistic effects, both at the 1 part in 10 billion level, both essential for GPS accuracy 🧪
