What will happen to humans if they are sucked into a black hole?


NASA Goddard Space Flight Center

A black hole is a dense and massive celestial body with a gravitational force so strong that it can suck in not only matter but also light. Science writer Amanda Gefter is approaching the mystery of what will happen if a human falls into such a black hole. Apparently, it does not mean 'instant death', but unexpectedly strange events occur.

The strange fate of a person falling into a black hole (BBC Earth)

Everyone has probably wondered at least once, ``What would happen if a person fell into a black hole?'' This is more unrealistic than the usual answer.

If a human falls into a black hole, it will split into two, one will instantly burn to ashes, and the other will fall into the black hole unharmed.

◆What exactly is a black hole?
A black hole is a place where the laws of physics that humans have discovered break down. The center of a black hole is a pitch black circle, which is called

the event horizon (Schwarzschild surface). A very strong gravitational field is formed here, and escaping requires a speed faster than the speed of light. Since even light is sucked in, a black hole becomes a completely black celestial body, making it difficult to observe it directly. In other words, images that look like 'black hole photographs' that you often see are not photographs, but model images of black holes created by calculations from a physical perspective.

It is also thought that the black hole's event horizon is on fire, and a stream of fiery particles is dispersed throughout the universe due to quantum effects. This refers to thermal radiation generated by a black hole called Hawking radiation , and after a sufficient amount of time, the black hole radiates all its mass and disappears.

And deep inside a black hole, there exists a place called a singularity that bends space-time infinitely. The singularity of a black hole is a truly unknown place where the density and gravity diverge to infinity, and where the laws of physics and everything else do not apply, and no one knows what will happen here. .

◆What will happen if you are sucked into a black hole?
After reviewing the overview of black holes, the next step is to simulate what happens when you are actually sucked into a black hole.

・Observing humans being sucked into a black hole from a position sufficiently far away from the black hole
First, we will simulate what it would look like if a person being sucked into a black hole were observed from a position sufficiently far away from the black hole.

Suppose we observe a hypothetical person named 'Masaru' being sucked into a black hole from a safe position outside the black hole. At first, Masaru is floating in space, but from there it gradually accelerates as it approaches the event horizon. As Masaru approaches the black hole, Masaru's body appears to stretch and distort, as if he were looking at Masaru through a giant magnifying glass. As Masaru approaches the event horizon, its movement gradually slows down.

At this time, since the event takes place in outer space, there is no air, so you cannot make a sound, but you may be able to use light to call for help from those around you. However, the closer you get to the black hole, the more slowly it appears to be moving from the outside, so even when Masaru sends a message of 'Help me!' with light, he says, 'T......... It seems that it becomes a very long message like '.........'.

Suppose Masaru finally arrives at the event horizon. When it gets to this point, from the outside looking in, it looks like it's distorted and suddenly stops, as if you've pressed a pause button. Masaru, which is almost at a standstill, can be observed very slowly turning to ashes due to the heat of Hawking radiation emitted from the event horizon.

・The world seen from the side of humans who are sucked into a black hole
On the other hand, if you were to be sucked into a black hole, how would the world around you change?

If you approach a black hole straight, you won't feel any impact or shaking, your own body won't become distorted like it does when you see it from the outside, and time will slow down, and you won't notice Hawking radiation. It seems that the body does not burn due to the heat. This is because the person is falling freely towards the black hole, and the person falling does not feel gravity.

From the outside, it appears that there is a wall on the event horizon, but in reality there is no wall. If the size of the black hole is small, the gravity acting on the head and feet of a person at the event horizon will be very different, causing the body to be stretched vertically like a pasta noodle. However, if the black hole is millions of times larger than the sun, the difference in gravity between the head and the feet will be negligible, so a large enough black hole will form a normal body. It is possible to fall to the singularity while doing so.

◆Black hole information paradox
If you observe Masaru being sucked into a black hole from the outside, it will certainly appear to the observer that Masaru's body is burning up in the event horizon. This is not a hallucination, and it is even possible to collect cinders and mourn. From a quantum mechanical perspective, if you observe a person being sucked into a black hole from the outside, all the information that makes up the black hole will stay outside the event horizon.

On the other hand, if we consider Einstein's theory of general relativity, those who are actually sucked into a black hole will not burn up at the event horizon and will be able to pass through it easily. In other words, if we are to be sucked into a black hole, the same person must exist both inside and outside the black hole at the same time, according to both general relativity and quantum mechanics. Physicists call this phenomenon the ' black hole information paradox .'

However, a method to solve the black hole information paradox was discovered in the 1990s. The discovery was made by a scholar named Leonard Suskind, who said that since no one can see the other self inside a black hole, the paradox does not occur. In other words, if you are observing Masaru entering a black hole from the outside, it is natural for the observer to see Masaru disappear, but for Masaru himself, it is natural for him not to disappear, and for the outsider it is natural for Masaru to disappear. It seems that the laws of physics will not be broken because the person observing from outside cannot see inside the black hole, and the person in charge cannot see outside the black hole.

In addition, a thought experiment to elucidate the black hole information paradox was conducted in the summer of 2012 by four physicists, Ahmed Almheiri, Donald Marolf, Joe Polczynski, and James Sully. I am assuming that there is

a firewall in the ground plane.

After all, there are still great mysteries surrounding black holes, and no one yet knows what happens when you are sucked into a black hole.

In addition, in the book ``

Big Questions in Science, '' which summarizes various scientific mysteries that have the potential to be solved, it is said that rather than saying that we do not know what is on the other side of a black hole, it is ``What is on the other side of a black hole? No tool has yet been invented to find out if it exists .'

in Science,   , Posted by logu_ii