GPS is fundamentally a translation tool: it converts time into distance. A satellite sends a signal, your phone catches it, and the delay between those two events tells the phone exactly how far away the satellite is. Everything else is about making that measurement precise enough to be useful: accounting for bad clocks, satellite geometry, and eventually, Einstein’s theories.
I had an idea of how GPS works, but this explainer visually shows it. Math, physics, and Einstein’s theory of relativity. All in a thing that we use every day and we don’t even think about it.
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