Three-Body Problem

Three-Body Problem is a hands-on 3D simulation of three masses attracting each other with gravity. Students drag any star to a new position, drag the diamond on its arrow to change its velocity, and change each star's mass. Six starting setups are included: the figure-eight orbit, the Lagrange triangle, the butterfly, the Pythagorean 3-4-5 problem, a binary star with a planet and a random start. Readouts show total energy, energy drift, angular momentum and the closest pair, and a twin run shows how a tiny change in the start grows into a completely different future.

• Choose Figure-eight and watch three equal stars chase each other along one looping path, then check that Total energy stays near -1.287.
• Drag Star 3 a little way off its path while the sim is paused, press Play, and see the figure-eight fall apart.
• Turn on the Twin run and compare the Twin separation readout for Figure-eight and for Random chaos.
• Pick Binary + planet and drag the small planet closer to the stars until its orbit becomes unstable.
• Raise Star 1 mass with the slider and watch the other two stars swing round it faster.
• Try Pythagorean 3-4-5 and watch the Closest pair readout drop during a close encounter.

1. 1Explain why the motion of three bodies under gravity cannot be written as one simple formula.
2. 2Describe how a tiny change in starting conditions can lead to very different outcomes (chaos).
3. 3Use total energy and angular momentum readouts to check that a simulation conserves them.
4. 4Predict how changing a star's mass or velocity changes the shape of its orbit.

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