Kepler Confirms His Third Law: Planets Move in Predictable Harmony
Kepler threw away his greatest insight on March 8, 1618. The math relating a planet's orbital period to its distance from the sun—cubed and squared in perfect harmony—looked wrong at first. Two months of rechecking every calculation, wrestling with the numbers that would've made Copernicus weep. On May 15, he confirmed it: T²/R³ stays constant for every planet. The equation fit Mars, Jupiter, Earth. All of them. But here's the thing—he'd been holding the key to Newton's gravity for decades, and didn't know it. Sometimes you find gold and mistake it for dirt.
May 15, 1618
408 years ago
Key Figures & Places
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