# Calendopaedia - Kepler's Laws of Planetary Motion.

### Kepler's First Law States

The orbits of the planets are ellipses, with the sun at one focus of the ellipse.

[This means that the distance that the earth is from the sun varies.]
### Kepler's Second Law States

A line joining the planet to the sun sweeps out equal areas in equal times
as the planets travel around the ellipse.

[This has the implication that the speed of the planet along the orbit varies
as the distance from the sun varies.]
### Kepler's Third Law States

The square of the period of a planet divided by the cube of the
radius of the planet's orbit is a constant.

[This means that the greater the distance from the sun, the longer the orbital time.]
For a drawing see The Earth's Orbit.

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