Black holes are regions of spacetime where gravity is so intense that nothing can escape once it crosses the event horizon. Predicted by Einstein's General Relativity in 1915 and named by John Wheeler in 1967, they remained theoretical curiosities until the first direct image was captured by the Event Horizon Telescope in 2019.
Stellar-mass black holes form when massive stars collapse at the end of their lives. Supermassive black holes — millions to billions of solar masses — lurk at the centers of nearly every galaxy, including our own Milky Way (Sagittarius A*, 4 million solar masses). How they grew so massive remains one of the great open questions in astrophysics.
Black holes are not just cosmic vacuum cleaners. They are laboratories for extreme physics: Hawking radiation connects quantum mechanics and gravity, gravitational lensing bends light into Einstein rings, and tidal forces near the horizon can stretch matter into spaghetti. These simulations let you explore these phenomena with real equations from General Relativity.