galileo

How GPS works: 31 satellites, trilateration, atomic clocks, and the relativity correction that keeps fixes accurate to a few meters on a phone.

In 144 years, European thinkers traded inherited doctrine for measurement, experiment, and proof, and built the method science still runs on.

In January 1610, Galileo saw four stars near Jupiter that moved. Within a week he understood the solar system would never be the same.