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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