1609–1619Reputable sourceWell documented
Kepler's Laws of Planetary Motion
On the timeline · around 1609–1619 ·
What happened
Using the remarkably precise observations of Tycho Brahe, Johannes Kepler discovered three mathematical laws of planetary motion: planets move in ellipses with the Sun at one focus; a planet sweeps out equal areas in equal times; and the square of a planet's orbital period is proportional to the cube of its distance from the Sun.
Why it matters
Kepler replaced the ancient assumption of perfect circles with exact laws drawn from data, turning astronomy into a precise physical science — and giving Newton the raw material from which he would derive universal gravitation.
Sources
Related timelines
- The Universe → — The mathematical laws of the heavens