Will the Universe be deleted — The Blackhole Information Paradox?
As wonderful as they may seem, Black Holes can be pretty troublesome in many ways. For example, they can possibly obliterate everything that we perceive as our Universe! But aren’t the black holes a part of the Universe itself? To make sense of this, we need to get a better understanding of what these black holes really are.
Since Albert Einstein introduced to us the General Theory of Relativity, he also helped in development of a mathematical model that has helped us in describing the Universe and its dynamics. Spacetime acts as a stage where the Universe is making its play. Matter bends the spacetime and this curved spacetime dictates the motions and dynamics of the matter and also characterizes gravity. Black holes are usually described as a nuisance in this theory. They are considered to be so massive and dense that they bend the spacetime so much that they have nearly infinite gravity. This means that once anything enters a Blackhole, it can never escape it. Consider you are walking on a road and come across an endless pit! It is so deep that if anything falls into it, you will never know what happened to it. Black holes are somewhat similar. They act as an endless pit, where once information goes inside, there is no known way to retrieve that information. Light, as fast as anything can get in this Universe, itself cannot escape the gravity of black holes once entering it.
But the information still may not be completely lost. That the information may still be there somewhere in some form in the black hole. It is just that we won’t be able to get it. The laws of Quantum Mechanics say that information is always preserved. Even if an object changes its state, if we have all its elementary particles and know the properties of the change, we can theoretically be able to retrieve that object’s previous state.
What information are we talking about here? How particles are arranged, the structure is what describes anything. The quantum information of position, velocity and spin of the elementary particles is what the physicists are really interested in. Eventually, the primary building blocks of everything in the Universe are the same. It is the way in which they are arranged that brings a difference. Coal and a diamond are both made of carbon atoms. The difference between them is because of the information about their arrangement. One can understand how basic yet valuable this information is. Without the information, there won’t be a difference between anything. Everything would have been the same! Black holes swallow this information and now it may be lost to us. As said earlier, we still don’t know what happened to that information. It might just be there inside it. Some theories say that the information never enters a black hole but just sticks onto its surface at the event horizon. We don’t know. But this is not our biggest problem.
The real problem starts when we learn about the Hawking radiation, which says that the black holes are slowly evaporating. Although the process is very slow, they are emitting radiation and gradually decreasing in size. The process is so slow that a black hole of mass of size of our Sun, it would take 10⁶⁷ years for it to completely evaporate. Many scientists believe that many trillions of years later when all the stars in the Universe will have fizzled out or been swallowed, there will only be black holes left. And these too shall vanish by evaporating leaving only some radiation behind. This escaping radiation seems to be completely unrelated to the information stored in the black hole. So, the question is, what happens to all the information that the black holes carried? They had information of several stars, of cosmic bodies and much more. Now that these black holes are gone, the information too is lost! And this time it is not the case of us being unable to retrieve it. When a black hole shall vanish, some part of the information about the Universe that it carried will get erased off completely. That means some part of the Universe itself will get deleted. It is an extremely scary thought. This is called the Information Paradox.
The paradox poses threat to the theories of General Relativity and Quantum mechanics, around whom most of the modern physics revolves. If the information is getting destroyed, that means we need to re-write the laws of Physics. Some people believe that the information that enters a black hole gets encoded in the escaping radiation in a way that we cannot comprehend. Some believe that a unified theory of everything will be a solution to the paradox. There’s also a theory that suggests the presence of wormholes that carry this information from black holes to an entirely different Universe. The Holographic Principle theorizes that all the information entering the black hole gets encoded on its surface and is not lost. Information of 3D objects gets projected on a 2D surface, like a hologram. If this is true then it leads to a bizarre thought that our entire reality, as we perceive it, might just be a holographic projection from a 2D surface that is very far. The black hole information paradox has led to some amazing questions that can shake the foundations of the subject.
Some theoretical physicists have very recently proposed in their breakthrough papers that information does come out of the black holes eventually, in simplified gravity models. This may just have resolved one of the most famous paradoxes in Physics. But there is a lot of work to be done before getting a definite answer.
Till then, if you are worried about what legacy will you leave behind, worry no more. Your information will be floating around somewhere in some part of the Universe, at least for trillions of years.
