Divergence

How it works

Three bodies of equal mass attract each other according to Newton; gravity is smoothed at short range so that no two bodies lock into a tight pair. An integrator advances their motion in small, fixed steps, with exactly the same numbers for both skies; without an intervention they therefore stay equal down to the last bit. When you grab a body in the right sky, it is first set back to its twin on the left; then you may move it within the dashed ring, or nudge it with the button by the chosen size across its direction of travel. The three-body problem is chaotic: every close encounter of two bodies enlarges the difference until it is as large as the system itself. A nudge a thousand times smaller only delays that moment by a few orbits.

It is drawn with Canvas 2D, without WebGL. Every body leaves a trail of its latest positions that fades with age. In the right sky, hollow rings show where the bodies would be without the nudge; the line to them is the distance. It is given as a share of one sky's width, and “Apart after” counts the seconds until it exceeds 5 %. So that no body disappears for good, a soft edge brings it back; that edge exists only on the stage, not in physics. With reduced motion nothing animates; after a nudge, both skies are computed at once up to just after the moment they part and drawn as a still picture. All colours come from the design tokens.