Real N-Body Physics
Newton's law of gravitation, computed between every pair of up to ten bodies, every frame. Adjustable gravitational constant and time scale - not a scripted animation.
Real gravity. Real collisions. Watch it unfold.
A genuine Newtonian n-body simulator for iPhone and iPad. Drag the edges to bend time and gravity, pinch to zoom, and let up to ten bodies fall together - down to the collision.
Download on the App Store →Live preview#1
A sample n-body problem: a three-body collision. Fragmentation differs on every run.
What's inside
Collisions & Fragmentation
Bodies merge or shatter into pieces depending on impact speed, with momentum and energy conserved exactly. Slow taps merge; fast ones scatter debris across the screen.
Built-in Astrophysics
The real formulas behind the simulation, a reference table of actual celestial bodies, and a short history of orbital mechanics from Ptolemy to Einstein - in six languages.
What you can explore
Two stars, one center
A binary star system
Two stars orbit their common centre of mass while one planet circles a single star closely and another circles both from far out - two very different kinds of stability, side by side.
Nine planets, one Sun
Our own Solar System
Mercury to Neptune, plus the Moon, with masses and velocities scaled from the real numbers. Zoom out to see all eight orbits, zoom in to watch the Moon circle the Earth.
Tune it yourself
Every number is yours to change
Type your own masses, positions and velocities into the table, watch the vector arrow update as you type, or let the app generate a random system and see what gravity does with it.
Nothing is hidden. Every constant that drives the simulation - even the fragmentation rules - is exposed in a technical panel you can change and reset.
What it doesn't do
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Nothing is savedNo account, no sign-in, no analytics, no trackers - and no local history either. Every launch starts from the same defaults.
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Nothing sent over the networkThe simulation runs entirely on your device. Nothing about what you build or watch is uploaded, observed or shared.
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No in-app purchases, no adsYou buy the app once. Nothing is locked, nothing nags you, no advertising ever appears.
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Safe for children, useful at any ageNo chat, no links to strangers, nothing to stumble into. The physics is the same whether you're nine or ninety.
Full details in the privacy policy.