1600s / 17th century history on the 15th of May
1618 : Johannes Kepler confirmed his discovery of the third law of planetary motion, which he first discovered 2 months earlier on the 8th of March but originally rejected the idea.
1618 : Johannes Kepler confirmed his discovery of the third law of planetary motion, which he first discovered 2 months earlier on the 8th of March but originally rejected the idea.