StarSim-X

StarSim is a Newtonian n-body gravity simulator powered by a real physics engine. Use the edges of the screen to change time and gravity, pinch to zoom, tap any body to see its live mass, position, speed, momentum and kinetic energy. Let bodies collide: slower contacts tend to merge, faster ones shatter into pieces; momentum and energy are conserved exactly. A planet that gains enough mass can cross the threshold and ignite into a star with its own glow. Watch each body's trail in its own color, and follow every collision and merge step by step in the console panel (with m, v, p, E and collision heat). Built-in systems include a binary star with two planets, our own Solar System (with the Moon), and a three-body collision test. Or type your own initial masses, positions and velocities into the table and watch gravity decide what happens, or tap Random for a different scenario every time. Build your own small universe. A full astrophysics reference is included: the real formulas behind the simulation, a table of actual celestial bodies, and a short history of orbital mechanics from Ptolemy to Einstein; all of it in six languages. This app collects none of your data, saves none of it, sends none of it. No account, no ads, no in-app purchases.