It has long been known on paper what happens if you ever have the misfortune to fall into a black hole. But what this entails is less clear. The US space agency NASA has used a supercomputer to visualize what such a journey could look like.
Important context: what are you actually seeing?
Two scenarios are simulated. The first video, which you can see at the bottom of this article, shows what happens if you fall directly into a black hole. In the second, the camera reaches the edge of the black hole. The simulated black hole has a mass 4.3 million times that of our Sun, the same as the one at the center of the Milky Way.
The black hole’s event horizon spans about 25 million kilometers. The event horizon is the point at which the escape velocity becomes equal to the speed of light, meaning that even light cannot escape. In fact, you only see a black void, hence the name ‘black hole’. Surrounding the black hole is a flat cloud of super-hot gas called the accretion disk.
Since everything within the event horizon is black, the accretion disk in the videos is actually one of the only reference points, along with the photon rings, glowing structures consisting of light that passes around a black hole one or more times. Finally, the starry sky is also visible, as it can be seen from Earth.
Falling into a black hole
As the camera approaches the black hole in the simulation, strange things happen. First the light from the accretion disk, but also the background, becomes increasingly brighter. This is because you are approaching faster and faster due to the enormous gravity of the black hole. This allows more photons to reach your eyes in the same time period.
In everyday life, this is actually the same effect as when a police car overtakes you. As the car gets closer, the pitch gets higher because more sound waves reach you in a shorter time. When the police car has overtaken you and moves further away, the pitch drops again.
Even more striking, however, is that as the camera approaches the black hole, you see in both videos how the accretion disk, the photon rings and the background begin to distort. At some point you may even see the same distorted images multiple times from different angles. That’s because the gravity around the black hole is so intense that spacetime itself bends. As a result, you see light coming from two ‘sides’, as it were.
Spaghettification
When the camera finally enters the event horizon, the fun is over. As an astronaut, once you get past this point, you can never escape and you only have seconds left to live. Although light still seeps in from outside, the field of view becomes smaller and smaller the deeper the camera moves toward the center of the black hole.
12.8 seconds after reaching the event horizon, the camera is ‘spaghettified’ by gravity. That word comes from spaghetti and refers to the fact that the force of gravity at the closest point of the camera to the center of the black is so stronger than the furthest point that the camera is stretched into a string of mass that falls inward.
This does not happen in the second video. The camera just reaches the edge of the event horizon, but is then launched back outward by gravity. It is important to note: if you, as an astronaut, find yourself in this situation and escape, you will notice that more time has passed in the ‘outside world’. This is because time moves slower from your reference point as gravity increases. In this example, after a six-hour round trip, you would be 36 minutes ‘younger’ than the outside world. If you’re flying around a rapidly spinning black, like in the movie Interstellar, it’s a different story. In the outside world, many years may have passed, while you have only aged a few hours.
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