What Happens If You Fall Into a Black Hole?
The short answer
It depends on the size of the black hole. Fall into a small one, a few times the mass of the Sun, and you are stretched into a noodle long before you reach its edge. Fall into the giant one in the middle of our galaxy, about 4 million Suns, and you cross the edge in one piece.
Scientists really call the stretching spaghettification. And to friends watching from far away, you never quite get there.
Why you stretch
Gravity pulls harder the closer you get. Fall in feet first and your feet are pulled harder than your head, because they are closer. So your body stretches along the fall and gets squeezed thin from the sides. NASA puts it this way: "squeezed horizontally and stretched vertically, resembling a noodle."
The pull itself is not what tears you apart. The difference in pull between your head and your feet is.
Why bigger is gentler
The edge of a black hole, the event horizon, is the point of no return. Its distance from the middle grows in step with the mass. For one Sun it is only 2.9 km (1.8 miles). A few Suns make a ball roughly 17 to 30 km across, about the size of a city. Packed that small, the difference in pull is brutal well outside the edge.
Astronomy magazine worked out that head to feet difference at the edge. For a black hole of one Sun it is around 19.6 billion m/s². For one of 100 million Suns it is about 0.0000019 m/s². Sagittarius A*, at about 4 million Suns, is a giant too. Its edge is so far out that your head and feet are pulled almost the same.
Gentle only holds at the edge. In NASA's 2024 simulation of a fall into a 4.3 million Sun black hole, the camera takes about 3 hours to reach the edge. It is spaghettified 12.8 seconds after it crosses.
What your friends see
Someone watching from far away sees something else. Your image slows down, turns redder and dimmer, and seems to freeze just short of the edge. Then it fades out of sight. They never see you cross. For you, falling, time seems to run normally.
Key numbers
| What | Number | Source |
|---|---|---|
| Mass of a small (stellar) black hole | from a few to hundreds of times the Sun's mass | NASA Science, Black Hole Types |
| Lightest known black hole | 3.8 times the Sun's mass | NASA Science, Black Holes |
| Distance from the middle to the edge, black hole of 1 Sun | 2.9 km (1.8 miles) | Astronomy magazine, Ask Astro on small black holes, 2023 |
| The Sun squeezed into a black hole | less than 6 km (well under 4 miles) across | NASA JPL, Marc Rayman |
| Width of a black hole of a few (3 to 5) Suns | about 17 to 30 km across | Our arithmetic from Astronomy magazine, Ask Astro on small black holes, 2023 |
| Mass of Sagittarius A*, the black hole in the middle of our galaxy | about 4 million Suns | ESO and the Event Horizon Telescope, 2022 |
| Head to feet difference in pull at the edge, black hole of 1 Sun | around 19.6 billion m/s² | Astronomy magazine, Ask Astro on small black holes, 2023 |
| Head to feet difference in pull at the edge, black hole of 100 million Suns | about 0.0000019 m/s² | Astronomy magazine, Ask Astro on small black holes, 2023 |
| Mass of the black hole in NASA's fall simulation | 4.3 million Suns | NASA Goddard (Schnittman), 2024 |
| Simulated camera's fall to the edge | about 3 hours | NASA Goddard (Schnittman), 2024 |
| Time from crossing the edge to spaghettification, in the simulation | 12.8 seconds | NASA Goddard (Schnittman), 2024 |
What the film simplifies
- "A ball about the size of a city" is our own comparison. No source uses those words for a few Suns, but the arithmetic gives about 17 to 30 km across.
- Crossing in one piece is not surviving. The film stops at the edge on purpose: NASA's simulated camera is spaghettified 12.8 seconds after it crosses.
- "Slip across" sounds slow and calm. The fall only feels calm: by the edge you are reaching speeds ever closer to that of light.
- In the film the stream fades out "right at the edge". The sources say the image freezes just short of the edge, or just outside it, then fades.
- "Technically, he's still buffering" is a joke. In practice his image fades out of sight, so the chat doesn't watch him forever.
- Rocket, his respawn, the chat and the black holes drawn as characters that slurp and snore are cartoon. "Another time zone" is a joke about distance, not a real time difference between his head and fins.
At a glance
Runtime 1 minute 13 seconds · Topics: Black holes, Gravity, Tidal forces · Captions on YouTube · Full script below
Test yourself
Why does a small black hole stretch you apart before you reach its edge, while a giant one lets you cross in one piece?
Answer
The stretch comes from the difference in pull between your head and your feet. A small black hole's edge is very close to its middle, so that difference is huge there. A giant's edge is so far out that your head and feet are pulled almost the same.
The edge of a black hole of one Sun is 2.9 km from its middle, and that distance grows in step with the mass. About how wide is a black hole of 4 Suns?
Answer
4 times 2.9 km is about 11.6 km from the middle to the edge, so the ball is roughly 23 km across. That's about the size of a city.
A friend watches from far away as you fall into a giant black hole. What do they see, and do they ever see you cross the edge?
Answer
They see your image slow down, turn redder and dimmer, freeze just short of the edge and fade out of sight. They never see you cross.
The script
Host: Fall into a small black hole, and you end up like this guy.
Rocket: Chat! Look how tall I am! Clip that!
Host: Gravity pulls harder the closer you get.
Host: Go in feet first, and they get pulled harder than your head.
Host: You stretch out long... and your sides squeeze in thin.
Rocket: My fins are in another time zone!
Host: Scientists really call this spaghettification.
Rocket: That's a real word?!
Host: A small black hole crams a few Suns into a ball about the size of a city.
Host: Its edge is the point of no return... and you're a noodle long before you get there.
Rocket: Okay, bad run. Respawn!
Rocket: New plan. We go bigger!
Host: Weirdly... that's the smart move.
Host: The black hole in the middle of our galaxy weighs about 4 million Suns.
Host: Its edge is so far from the middle, your head and feet get pulled almost the same.
Host: So you slip across its edge in one piece.
Rocket: Wait, that was the edge? I didn't feel a thing!
Host: The bigger the black hole, the gentler the fall.
Host: But to his chat, far away, his stream slows down...
Host: turns red... and fades out, right at the edge.
Host: Technically, he's still buffering.
Sources
- Falling objects stretch out like noodles, a process astrophysicists call spaghettification; NASA's simulated black hole has 4.3 million Suns; the camera takes about 3 hours to reach the edge and is spaghettified 12.8 seconds after crossing; a faraway watcher sees the image slow and freeze just shy of the edge; "If you have the choice, you want to fall into a supermassive black hole".NASA Goddard (Schnittman), 2024
- The event horizon is a black hole's point of no return.NASA SVS, 2024
- A body near a black hole is squeezed horizontally and stretched vertically, like a noodle; spaghettification is a real term; the lightest known black hole is 3.8 times the Sun's mass.NASA Science, Black Holes
- Stellar black holes range from a few to hundreds of times the Sun's mass; Sagittarius A* is 4 million times the mass of the Sun.NASA Science, Black Hole Types
- The larger the mass of the black hole, the weaker the tidal forces at its edge, because the horizon grows in step with the mass.NASA Imagine the Universe
- Your feet feel a stronger pull than your head; small black holes tear you apart before the edge; at a supermassive black hole your body stays intact as you cross.HubbleSite Black Hole Encyclopedia (STScI), tidal forces
- You would cross the horizon without any noticeable change; a falling clock seems to slow, redden and freeze at the edge to a faraway watcher, but ticks normally for someone falling with it.HubbleSite Black Hole Encyclopedia (STScI), falling clock
- The black hole at the center of the Milky Way is four million times more massive than the Sun.ESO and the Event Horizon Telescope, 2022
- The Sun as a black hole would be less than 6 km, well under 4 miles, across.NASA JPL, Marc Rayman
- A black hole of 1 Sun has an event horizon radius of 2.9 km (1.8 miles); the head to feet difference in pull at the edge is around 19.6 billion m/s² for 1 Sun and about 0.0000019 m/s² for 100 million Suns.Astronomy magazine, Ask Astro on small black holes, 2023
- A faraway watcher sees a falling object redden and fade out of sight, but never sees it cross the event horizon.Astronomy magazine, Don Lincoln (Fermilab), 2022
- You are stretched because your feet are nearer than your head; an outside watcher sees you get dimmer and redder until your fading image freezes just outside the event horizon.UC Berkeley Astronomy, Astro 10 slide
- A black hole's boundary is known as the event horizon.Harvard CfA, 2012