Gravity and Orbits: free physics simulation
N-body gravity sandbox: planets, moons, binary stars and the figure-eight orbit.
▶ Open the simulationFree, no sign-up. Works on phones, tablets and laptops.
The science
Every mass attracts every other mass with a force that falls off with the square of the distance. A planet in orbit is constantly falling towards its star while moving sideways fast enough to keep missing it. Kepler’s laws describe the resulting elliptical orbits.
F = G m₁ m₂ / r²
Things to try
- Give a planet a little less speed and watch the orbit become an ellipse.
- Build a binary star system.
- Load the famous figure-eight three-body orbit.
Topics covered
solar system kepler n-body planets moon binary star
How to use it
Open the simulation, then change the experiment live with the sliders, checkboxes and buttons in the side panel. Drag objects on screen where it makes sense, and use Pause, Step, Speed and Reset in the bottom bar to study every moment.
Frequently asked questions
What does the Gravity and Orbits simulation show?
Every mass attracts every other mass with a force that falls off with the square of the distance. A planet in orbit is constantly falling towards its star while moving sideways fast enough to keep missing it. Kepler’s laws describe the resulting elliptical orbits.
What is the key equation?
F = G m₁ m₂ / r²
Is the Gravity and Orbits simulation free?
Yes. It runs free in any web browser on phones, tablets and laptops, with no sign-up or download.
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