Black Hole Simulator

An interactive spacetime sandbox. Drag on the map to launch test particles, gravity stars, light rays or spaceships, then watch where gravity takes them.

Black hole: set the spin from −0.99 to +0.99 and see the event horizon, the ergosphere and the prograde and retrograde innermost stable orbits change. A particle layer makes frame dragging visible, an accretion disk orbits the hole, and presets show stable orbits, gravitational lensing, the photon ring and a plunge.

Fly a spaceship with W, A, S and D: its onboard clock runs slower deep in gravity and at high speed, and the inspector shows by how much. Select any object to edit its speed and direction, put it on a circular orbit, see its predicted path and an orbit analysis with energy, angular momentum, periapsis and apoapsis. Place observer anchors and read the spacetime values under the cursor.

Two more pages compare a Newtonian solar system with extra gravity stars, planets, an asteroid belt and comets, and two horizonless exotic objects: a gravastar and a boson star.

A teaching model: pseudo-Newtonian gravity (Paczyński–Wiita) with the exact Kerr formulas for horizon and orbits – not a full general-relativity solver. Runs entirely in your browser; nothing is saved. Best on a desktop screen with a mouse.