Concept

Kepler's laws of planetary motion

Overview

In astronomy, Kepler's laws of planetary motion give good approximations for the orbits of planets around the Sun. They were published by Johannes Kepler from 1609 to 1621 in three works Astronomia nova, Harmonice Mundi and Epitome Astronomiae Copernicanae. The laws were based on Kepler's concept of solar fibrils adapted to the accurate astronomical data of Tycho Brahe. These laws replaced the circular orbits and epicycles of Copernicus's heliostatic model of the planets with a heliocentric model that described elliptical orbits with planetary velocities that vary accordingly. The three laws state that:

The orbit of a planet is an ellipse with the Sun at one of the two foci.

A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.

The square of a planet's orbital period is proportional to the cube of the length of the semi-major axis of its orbit.

The elliptical orbits of planets were indicated by calculations of the orbit of Mars. From this, Kepler inferred that other bodies in the Solar System, including those farther away from the Sun, also have elliptical orbits. The second law establishes that when a planet is closer to the Sun, it travels faster. The third law expresses that the farther a planet is from the Sun, the longer its orbital period.

Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).

Possible passages

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Behold them then returned to the spot from whence they had set out, after having discovered that almost imperceptible sea, which is called the Mediterranean; and the other narrow pond that surrounds this mole-hill, under the denomination of the great ocean; in wading through which the dwarf had never wet his mid-leg, while the other scarce moistened his heel. In going and coming through both hemispheres, they did…
Voltaire, Voltaire's Romances, Complete in One Volume
States what Kepler's laws of planetary motion is; the author is tied to Kepler's laws of planetary motion in the knowledge graph.
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We know that light was not made before the day, and that it comes to us from the sun. We know that the supposed solid expanse between the upper and the lower waters, which is called the “firmament,”[35] is an error of ancient physics, adopted by the Greeks. But as God was speaking to the Jews, he deigned to stoop low enough to adopt their language. Certainly no one would have understood him in the desert of Horeb if…
Voltaire, Toleration and other essays
States what Kepler's laws of planetary motion is; the author is tied to Kepler's laws of planetary motion in the knowledge graph.
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For this system, which is called that of _occasional causes_ (because it teaches that God acts on the body at the instance of the soul, and _vice versa_), besides introducing perpetual miracles to establish communication [157] between these two substances, does not obviate the derangement of the natural laws obtaining in each of these same substances, which, in the general opinion, their mutual influence would cause.
Gottfried Wilhelm Leibniz, Theodicy Essays on the Goodness of God, the Freedom of Man and the Origin of Evil
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Philosophers who discussed Kepler's laws of planetary motion

Pythagoras

Related ideas

Opposing perspectives

Scientific Revolution

Place in the tradition

Part of Cosmology.

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