# Kepler's Laws of Planetary Motion

Kepler's laws describe the motion of the planets in the solar system.

## Kepler's first law (Law of orbits)

The orbit of every planet is an ellipse with the sun at one of the two foci.

## Kepler's Second law (Law of areas)

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

## Kepler's third law (Law of Periods)

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

### Kepler's third law formula

\(\large{ P^2 = a^2 }\) |

### Where:

Units |
English |
Metric |

\(\large{ P }\) = planet's distance from the sum | \(\large{mi}\) | \(\large{ mi }\) |

\(\large{ a }\) = semi-major axis of the planet's orbit | \(\large{mi}\) | \(\large{mi}\) |