Kepler's laws
This page delivers no verdict; it presents claims and evidence with their sources. No theory in science is absolute. Method
For everyone
Using Tycho Brahe's precise observations of Mars, Kepler found that planetary orbits are ellipses, not circles. His three laws describe how a planet's speed and orbital period vary with its distance from the Sun. Newton later derived them from the law of gravitation. While doing this work Kepler also served as a court astrologer.
For specialists
The first and second laws (elliptical orbits, equal areas in equal times) appear in Astronomia Nova (1609), the third (T² ∝ a³) in Harmonices Mundi (1619). Kepler could not close an 8-arcminute discrepancy in Mars's orbit with circular models, which led him to the ellipse. He thought of a magnetic-like force emanating from the Sun as the cause of the motion.
Claims
- Planets move in elliptical orbits with the Sun at one focus.[1]
Evidence
Supporting
Tycho Brahe's Mars observations, precise to about 2 arcminutes, disagreed with a circular orbit but fit an ellipse.[1]
Challenging
—
Connections
Sources
- Book (1609). Astronomia Nova. Gotthard Vögelin, Heidelberg
Search the literature
Look for scholarly work on this topic in other indexes:
Cite this page
Athena contributors. (2026). Kepler's laws. Athena: The tree of human knowledge. Retrieved November 1, 2026, from https://latifkedi.github.io/athena/en/d/kepler/
@misc{athena_kepler,
title = {Kepler's laws},
author = {{Athena contributors}},
year = {2026},
howpublished = {\url{https://latifkedi.github.io/athena/en/d/kepler/}},
note = {Athena: The tree of human knowledge. Accessed: 2026-11-01}
}Added: September 27, 2026 · Last changed: September 28, 2026 · Page history