Kepler's law

American  

noun

Astronomy.

1. any one of three laws governing planetary motion: each planet revolves in an ellipse, with the sun at one focus; the line connecting a planet to the sun sweeps out equal areas in equal periods of time law of areas; or the square of the period of revolution of each planet is proportional to the cube of the semimajor axis of the planet's orbit harmonic law.

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Etymology

Origin of Kepler's law

After J. Kepler

Example Sentences

The generalizations which can be collected on the subject from direct observation, even such as Kepler's law, are mere approximations: the planets, owing to their perturbations by one another, do not move in exact ellipses.

From Project Gutenberg

Jupiter, which shows the greatest effect, makes the circuit of his orbit in 4,333 days instead of 4,335, which it would require if Kepler's law were strictly true.

From Project Gutenberg

But in another respect the change is of the utmost importance, since it enables us to extend Kepler's law, which relates solely to the sun and its planets, to other attracting bodies, such as the earth, moon, and stars.

From Project Gutenberg

As solar pressure, atmospheric drag and other forces act on them, they obey Kepler's law; their orbit times decrease until they approach the Schuler 84-minute period.

From Time Magazine Archive

The moon's time of revolution, when so near the earth as barely to escape contact with it, must have been, by Kepler's Law, more than two and less than two and a half hours.

From Project Gutenberg