Kepler's laws of planetary motion

American  

plural noun

1. Astronomy. all three of Kepler's laws considered as a group.

---

Kepler's laws of planetary motion Scientific  

/ kĕp′lərz /

1. Three laws devised by Johannes Kepler to define the mechanics of planetary motion. The first law states that planets move in an elliptical orbit, with the Sun being one focus of the ellipse. This law identifies that the distance between the Sun and Earth is constantly changing as the Earth goes around its orbit. The second law states that the radius of the vector joining the planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse. As such, the planet moves quickest when the vector radius is shortest (closest to the Sun), and moves more slowly when the radius vector is long (furthest from the Sun). The third law states that the ratio of the squares of the orbital period for two planets is equal to the ratio of the cubes of their mean orbit radius. This indicates that the length of time for a planet to orbit the Sun increases rapidly with the increase of the radius of the planet's orbit.

---

Example Sentences

According to Kepler’s laws of planetary motion, the shape of the orbit is elliptical, with the Sun at one focus of the ellipse.

From Textbooks • Mar. 30, 2016

All three of Kepler’s laws of planetary motion can be derived from Newtonian principles.

From "Cosmos" by Carl Sagan

Ptolemy gave the astrologers the information they needed, and Newton explained Kepler’s laws of planetary motion.

From "The Invention of Science" by David Wootton

You may think that this is simply because Galileo’s law is incomplete: Newton’s theory of gravity provides an explanation both of Galileo’s law of fall and of Kepler’s laws of planetary motion.

From "The Invention of Science" by David Wootton