What is the eccentricity of the Earth's orbit?

Answer 1

A circular orbit is an ellipse but with zero eccentricity.

The eccentricity of an orbit measures how far off-centre the Sun is. For the planets' orbits which are almost circular, they are well represented as circular in shape but with the Sun off-centre by an amount equal to the average distance times the eccentricity.

The Sun is therefore at a distance of ae from the centre of the near-circle. For the Earth a = 150 million km while e = 1/60, so the Sun is 2.5 million km from the centre of the circle and our distance varies between 147.5 and 152.5 million km (closest in January each year).

Answer 2

The Earth's axis completes one full cycle of precession approximately every 26,000 years. At the same time, the elliptical orbit rotates, more slowly, leading to a 21,000-year cycle between the seasons and the orbit. In addition, the angle between Earth's rotational axis and the normal to the plane of its orbit moves from 22.1 degrees to 24.5 degrees and back again on a 41,000-year cycle. Currently, this angle is 23.44 degrees and is decreasing.

Answer 3

The eccentricity of Earth's orbit is numerically defined as 0.0167.

Where does that figure come from? The variation in mean orbital radius of 149.6 million km is ±2.5 million km; 2.5 divided by 149.6 = 0.0167.

Answer 4

The earths eccentricity is approx. 0.0167 The earths eccentricity is approx. 0.0167

Answer 5

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