<Li> Neither the linear speed nor the angular speed of the planet in the orbit is constant, but the area speed is constant . </Li> <P> The eccentricity of the orbit of the Earth makes the time from the March equinox to the September equinox, around 186 days, unequal to the time from the September equinox to the March equinox, around 179 days . A diameter would cut the orbit into equal parts, but the plane through the Sun parallel to the equator of the Earth cuts the orbit into two parts with areas in a 186 to 179 ratio, so the eccentricity of the orbit of the Earth is approximately </P> <Dl> <Dd> ε ≈ π 4 186 − 179 186 + 179 ≈ 0.015, (\ displaystyle \ varepsilon \ approx (\ frac (\ pi) (4)) (\ frac (186 - 179) (186 + 179)) \ approx 0.015,) </Dd> </Dl> <Dd> ε ≈ π 4 186 − 179 186 + 179 ≈ 0.015, (\ displaystyle \ varepsilon \ approx (\ frac (\ pi) (4)) (\ frac (186 - 179) (186 + 179)) \ approx 0.015,) </Dd>

Planets move in ellipses with the sun at one focus