Inner Solar System

Centered on

This simulation shows the four inner planets of the solar system, as they orbit the Sun. Moving out from the Sun, we see Mercury, Venus, Earth, and Mars, in that order. The strip at the bottom shows what the other four objects look like in the sky, as viewed from an observer on whatever object is at the center.

Note that there are various scales in the picture. The relative sizes of the planets (and, in the strip at the bottom, their relative apparent sizes) are approximately correct. At that scale, however, the Sun should be shown 60 times larger than it is (or, the planets should each be 60 times smaller than they are shown). Also, the planets are shown much larger than they should be, with respect to the distances between the various objects.

On March 12, 2019, Physics Today published a commentary by Tom Stockman, Gabriel Monroe, and Samuel Cordner, that looked at which planet was the nearest neighbor to Earth. Often, people think that our nearest neighbor is Venus, and Venus is certainly the planet that has the smallest minimum distance from Earth. However, if you average the distance between Earth and other planets over time, you find that Mercury is, on average, our nearest neighbor. (The Sun is, on average, even closer, but the Sun is not a planet.) An implication of the study is that Mercury is the nearest neighbor, on average, to all the other planets in the solar system, for the same reason it is Earth's nearest neighbor, on average.

This simulation allows an exploration of this idea, and the simulation tracks the distance at any time, as well the average distance. The planets (or the Sun) are shown in order of increasing current distance, in astronomical units. One astronomical unit is the distance between the Sun and the Earth, which is very close to 1.5 x 1011 m.