Mass curves spacetime — visualised here as a warped 3D grid,
the classic 'rubber sheet' analogy. Photons (yellow) and massive
particles (blue) both follow the curvature; close enough to the
event horizon (black sphere) and nothing, not even light, escapes.
The event horizon sits at the Schwarzschild radius,
Rs = 2GM/c². This simulator maps that directly to the
"Mass" slider, scaling the black sphere's size. Just outside it,
at 1.5×Rs, lies the photon sphere — the tightest
orbit light itself can hold, shown live below.
- Mass — sets M, growing the horizon and the pull on nearby paths.
- Observer distance — moves the camera in/out and exaggerates how strongly light-bending reads visually, the way a wide-angle lens near a real black hole would magnify lensing.
- Kerr spin — toggles a simple rotating-black-hole look: a faster, asymmetric accretion disk plus a highlighted ergosphere ring, the region around a spinning hole where spacetime itself is dragged along.
- Launch photon / particle — fires a test object and lets curvature (not a scripted path) decide its fate.
Real-world check: the Event Horizon Telescope's 2019 image of
M87*'s shadow captured light bent around exactly this kind of
photon sphere, and astronomers already see the same lensing
effect distorting the images of background stars that pass
behind ordinary (non-supermassive) stellar-mass black holes.