Below is an orrery implemented in JavaScript. My intent with this was to build a simple physical model of the solar system that, while it might not be exactly right in terms of particulars, still got the physics more-or-less correct. Without using any differential equations, just brute force math.

It's obviously still not finished--Saturn, Neptune, Uranus and Pluto aren't included, and the planets weren't in conjunction on January 1, 2012, as this simulation purports--but each of the planets shown does take approximately the right amount of time to complete an orbit around the Sun, so that's good enough for me, for now at least.

To see the code, or to make a comment, visit https://thiscouldbebetter.wordpress.com/2012/12/07/programming-a-primitive-orrery-in-javascript.