Earth orbits the Sun in a slightly elliptical path rather than a perfect circle.

The longer version

Kepler's laws describe orbits as ellipses with the Sun at one focus, and Earth follows that rule with only a slight departure from a circle. The distance to the Sun therefore varies a little over the course of a year. The difference between the nearest and farthest points is only a few percent.

Because gravity pulls harder when bodies are closer, Earth moves slightly faster near perihelion than near aphelion. The small change in distance is far weaker than the effect of axial tilt, so it does not create the seasons. Many comets follow far more stretched ellipses that carry them great distances.

Where this entry sits

The night sky looks calm, yet almost everything up there is moving, burning, or slowly changing. These facts cover planets, stars, the Moon, gravity, black holes, comets, and the story of how people began exploring beyond Earth. The full list sits on the Space and Sky page, where every entry is listed in order.