Black holes are objects with so much matter concentrated in one point that nothing - not even light - can escape from a specific area around them. This was a feature of Newtonian gravity; this is a feature of Einstein's general theory of relativity; and when we have a complete quantum theory of gravity, we fully expect the same from it. When a sufficiently massive star dies and its core collapses, going through the stage of atoms, nuclei, neutrons and free quarks, a funny event occurs: even moving at the speed of light, nothing can leave this region of space.
Overcoming this threshold, everything contracts into a singularity in the center of this former star. This is how a black hole is born, and for the next trillions of years it will grow, devouring everything it can reach.
You might think there is a catch:
- Perhaps the singularity can be avoided.
“Perhaps she doesn’t eat everything that crosses her event horizon.
“Perhaps, if you are smart, you can escape from the inside.
But no, these are all immutable truths. No “maybe”. And despite Stephen Hawking's claims that there may be a possible way out, no amount of ingenuity will allow anything that falls into a black hole to leave it.
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Escape speed is a funny thing: it says that there is gravitational "thrust" in a particular area of space, and if your speed exceeds a certain threshold - the escape speed - you can overcome it. At a lower value, the speed will allow you to stay in a stable orbit, where you will not run away, but will fall forever and never fall. And if your speed is not high enough, you will fall on the gravity source from which you are trying to escape.
What does this mean if your escape speed is greater than the speed of light? Since nothing can exceed the speed of light, this means that there is no way to escape. And more than that. If you are inside the event horizon and want to exert force to "push" something that is trying to squeeze you, you cannot. To apply force or to push out means to move the particle outward. But all particles are limited to the speed of light. And if the speed of escape is greater than the speed of light, you will not be able to overcome the point at which you are squeezed; you cannot get out of the singularity. Also, and this is funny, it follows that once you fall outside the black hole's event horizon, you will see the singularity in all directions. The singularity is inevitable.
It also means that if you go to the event horizon and try to lower something beyond it, like touching water with your fingertip, it will never come back. The part of your body outside the event horizon will still be tightened, but the part inside cannot be returned; there is no way to extract material from the black hole - not even force-carrying particles - sucked into the singularity. Your only hope will be that someone merciful next to you will chop off your leg.
Why, then, did Stephen Hawking say that it is possible to escape from the black hole? Why did he say, speaking at Harvard:
Because he wasn't talking about you. He talked about the information that constitutes you at the time of the fall: when you cross the event horizon. When objects fall into a black hole, they have information of any kind: be it matter or antimatter, baryons or leptons, electrons or muons, neutrinos or neutrons. But according to the general theory of relativity (classical, anyway), a black hole has three informational properties: mass, electric charge, and angular momentum.
The famous "black hole information paradox" is that when the black hole finally disintegrates (thanks to Hawking radiation), only total energy, electric charge, and angular momentum remain; everything else is random. In other words, all unnecessary information is destroyed. Hawking's latest work speaks of things far less fantastic than escaping from a black hole; it says that whenever a new particle falls into a black hole, it changes the information encoded on the black hole's surface. And since the surface of a black hole (or surface area) depends on the mass and energy inside it, this information must come out, ground up but encoded in Hawking radiation. Just as a burned book contains information in pages (although not in a very convenient format),the outgoing Hawking radiation may contain information about what has fallen into the black hole.
This is far from escaping a black hole, but represents a possible solution to the information paradox, whatever one may say. However, if you are determined to get out of a black hole, there is only one way to do it, which obeys the known laws of physics: do not get there.
Ilya Khel