Solar System

Scroll or pinch to zoom, drag to pan, and click a planet to follow it.

How it works

The planets aren't pushed around by a gravity simulation. Instead each one follows its real orbit, using the orbital elements NASA's Jet Propulsion Laboratory publishes: how big the ellipse is, how stretched it is, which way it points, and where the planet was on January 1st, 2000. From there it's Kepler's laws. Work out how far around its year each planet should be by now, solve Kepler's equation to turn that into a spot on the ellipse, and draw it. That's why the planets start where they really are today, and why Mercury visibly speeds up as it swings close to the Sun.

The default view cheats. Spacing the orbits out honestly would leave the four inner planets in a clump around the Sun with Neptune far away at the edge, and every planet would be smaller than a pixel. So distances are squashed onto a logarithmic curve and the planets are blown up until you can see them. Flip on True scale to undo all of that. Distances and sizes go back to real proportions, and you'll need to zoom a long way into the dot that used to be the Sun before you find any planets at all.

The orbits drift a little over time, and the elements are tuned for the years 1800 to 2050, so if you let it run for a few thousand years the positions turn into a very good guess rather than a prediction.