2D Orrery: Kepler's Third Law Explorer

Time Speed

Simulation speed 1.0×

Planet Visibility

Selected Planet

Click a planet on the diagram to inspect it.

Current angle

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Orbital period

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Live Readout

Elapsed time

0.0 yr

Days simulated

How it works

This is a top-down mechanical orrery: every planet rides a fixed concentric ring around the Sun, exactly like the gear-driven brass orreries built by 18th-century clockmakers to demonstrate the Solar System.

Each ring's orbital period is not hand-picked — it is computed live from Kepler's third law, T² ∝ a³, where a is the ring's orbital radius in astronomical units (AU) and T comes out in Earth years. Double an orbit's radius and its period grows by roughly 2.83×, not 2× — which is exactly why the outer rings crawl while Mercury laps the Sun many times over.

Drag the speed slider to compress or stretch simulated time.
Toggle any planet off to declutter the view or compare periods.
Click a planet to lock the readout onto its live angle and period.

Top-down view · Sun fixed at center · rings drawn to scale (compressed)