This simulator shows what you would actually see falling into a real black hole, with every pixel worked out from Einstein's general relativity as you fall. The background is the real sky, from ESA's Gaia map and the Yale Bright Star Catalogue, so the bending of light you see is the bending of real starlight.
The three black holes
Choose one of three real black holes. Their size decides everything, including whether you survive to the horizon:
| Black hole | Mass | Distance | Event horizon radius | Horizon to singularity | Tidal stretch at the horizon |
|---|
| Sagittarius A* (Milky Way centre) | 4.3 million Suns | 27,000 light-years | 12.7 million km | 28.2 s | under 0.001 g |
|---|
| M87* | 6.5 billion Suns | 54.8 million light-years | 19.2 billion km | 11 h 51 min | under 0.001 g |
|---|
| Gaia BH1 | 9.62 Suns | 1,560 light-years | 28.4 km | 63.2 µs | 20 million g |
|---|
Times assume you fall from rest, starting very far away. The last column is how hard your head and feet are pulled apart at the horizon, for someone 1.8 m tall.
What you see on the way in
As you approach, the black hole's shadow grows and the sky behind it is bent into a bright Einstein ring. Stars ahead of you crowd together and turn brighter and bluer, because you are moving towards their light at a large fraction of its speed. Behind you the sky dims and reddens. At the event horizon nothing special happens to you: there is no wall and no flash. But from then on every possible path, even for light, leads inward to the singularity.
Spaghettification
Gravity pulls harder on the part of you that is closer, so your feet are pulled more than your head. Near a small black hole like Gaia BH1 this tidal stretch tears a person apart long before the horizon. Near a giant like Sagittarius A* or M87* it is gentle at the horizon and only becomes deadly much closer to the centre, which is why you can fall through the horizon of a supermassive black hole without feeling anything at all.
Two clocks
The two clocks on screen show your own time and Earth's. The deeper you fall, the more slowly your clock runs compared with Earth's. Your own clock never stops: from the horizon of Sagittarius A* you reach the singularity in about 28 seconds of your own time.
Frequently asked questions
What would you see if you fell into a black hole?
A growing black shadow surrounded by a ring of bent starlight, the sky ahead squeezed into a bright, blue-shifted patch, and no visible change at the moment you cross the event horizon.
Would you be spaghettified?
It depends on the black hole's mass. A small one, a few times the Sun's mass, stretches you apart well before the horizon. A supermassive one like Sagittarius A* has gentle tides at the horizon, and you are only torn apart closer to the centre.
How long does it take to reach the singularity?
Falling from rest far away, about 28 seconds after crossing the horizon of Sagittarius A*, almost 12 hours for M87*, and 63 millionths of a second for Gaia BH1, measured on your own clock.
How big is the black hole at the centre of the Milky Way?
Sagittarius A* has about 4.3 million times the Sun's mass. Its event horizon is about 12.7 million km in radius, smaller than Mercury's orbit.
Is the simulation accurate?
The light paths, colours and clocks are computed from general relativity for a non-rotating black hole, and the shadow it gives for Sagittarius A* matches the Event Horizon Telescope's measurement (51.8 ± 2.3 microarcseconds, 2022). Real black holes spin, which changes the details.
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