Is the distance between the Sun and the Earth always the same?
No. Earth’s orbit is elliptical, which means it’s closest to the Sun once a year (called perihelion), and farthest from the Sun once a year (called aphelion). Currently, perihelion occurs the first week in January, at at that time Earth is 91,402,725 miles from the Sun. At aphelion, in early July, the Earth is 94,509,130 miles from the Sun. These distances change over time, because the eccentricity of Earth’s orbit varies. Currently Earth’s orbit is slowly becoming more circular, but in a few thousand years it will start to get more elliptical again. We can compute this for several thousand years into the past and future, but when you start going out to a million years, the uncertainties become so great that the results are worthless. However, the *average* distance between the Earth and Sun is very constant, and won’t change much even if the eccentricity of the orbit changes. Over very long timespans — billions of years — the Earth will gradually move farther from the Sun, because t
