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Build your own planetary system in three dimensions, to scale, and see how long it lasts. The solar system starts from where the planets really are on the date you pick; drop a body into orbit with a click, throw it with a drag and watch its path before you let go. Bodies that touch merge, bodies that leave are lost.
Real masses, distances, radii and speeds (1 unit = 1 au) Planet positions from JPL Keplerian elements for any date 1800–2050 Leapfrog integrator with live energy-drift readout Circular-orbit drop and slingshot throws with trajectory preview Two-body orbit ellipses, merging collisions and escape tracking Orbit readout in km/s, au, days and years: eccentricity, period, bound or escaping Spacetime well from the true potential, cel-shaded bodies, fading trails Solar system, binary star, figure eight, star cluster, protoplanetary disc