Your phone is running Einstein's physics right now.
Your phone is running Einstein's physics right now. Not as a curiosity — as a necessity.
GPS works by timing signals from satellites, each one carrying an atomic clock of extraordinary precision. But Einstein's relativity tells us those clocks don't tick the same as clocks on the ground. Speed slows time down. Altitude speeds it up. The satellites experience both effects at once, and the net result is their clocks run slightly fast compared to yours.
Leave that uncorrected and GPS positions drift by several kilometres in a single day. Your map app would place you in the wrong street, the wrong town — possibly the wrong county.
So engineers wrote Einstein's equations directly into the system. Every position fix your phone delivers, relativity has already been accounted for. Physics this deep, built quietly into something this ordinary.
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