We’ve been talking about time here on Saturdays for weeks.
I explained the relationship between the concept of “time” defined by Albert Einstein as “what the clock measures” and entropy in thermodynamics; Then I said that the same entropy takes place in the theory of information.
We calculate the molecules, atoms and subatomic particles that are the subject of entropy and the “bits” that are the subject of “information” with the same equations. That is, quantum-level particles and “information” are identical, interchangeable, whether they have mass or not. At least that’s how it is mathematically.
After the famous “Bell’s inequalities” equations published in 1964 by John Bell, one of the greatest physicists of the 20th century, which I have described here before, it was not difficult for physicists to jump into “Quantum information theory”. Because this entropy identity was very obvious.
Quantum information theory has one big taboo or golden rule, “Knowledge cannot be destroyed,” the theory says. This rule is just like the first law of thermodynamics, which says “Energy changes form but cannot be destroyed”.
Is it really so? So information cannot be destroyed?
Another great physicist of the 20th century, Stephen Hawking, published his popular book “A Brief History of Time” in 1988, which brought him worldwide rock star fame. The book’s backdrop was Hawking’s black hole research, which entangled the world of physics.
Black holes are a mathematical necessity and a theoretical phenomenon that emerged from Einstein’s general theory of relativity. Such a large mass will come together in space-time that that region of space-time will collapse under the influence of gravity and will not allow even light to come out. This “thing” was called a black hole. We even take pictures of them today, but when Hawking was working on black holes, very few physicists believed they existed yet.
Hawking was wondering what was going on at the point of the black hole called the “event horizon”.
The “event horizon” refers to the final point at which a tiny photon, the particle that makes up the light, can save itself from falling into the black hole’s gravitational field. If it passes that point, the photon cannot escape falling into the black hole.
While thinking about the event horizon, Hawking thought of the laws of thermodynamics and entropy. There was tremendous gravity inside the black hole; this gravity naturally meant a very high amount of energy and heat. It would be expected that a closed surface that gets so hot would “transfer heat” to the outside, albeit little by little. So nothing was leaking out of the black hole; there was a “radiation” coming out.
This was called “Hawking radiation”. According to Hawking, if black holes were left on their own, they would disappear in a very long time due to this radiation leak.
Let me remind you here: Yes, we observed and proved black holes theoretically 100 years after we saw them theoretically exist, but we have not yet observed “Hawking Radiation”. Therefore, everything we say about black holes losing mass by emitting “Hawking radiation” and disappearing after a very long time is theory.
So if the black hole is disappearing, what happens to all the material that once formed it and then fell into it? The answer was clear: That material, too, was turning into “Hawking radiation” and disappearing.
But what fell into the black hole was not only “material”, it was also “information”, “information” of a quark, a lepton, a neutron, an electron, etc. Wouldn’t that “information” disappear with the black hole?
The gigantic problem called the “quantum information paradox” or also called the “Hawking paradox” is central to today’s discussions of physics. (Just a few weeks ago, a group of physicists announced that they had solved this paradox. According to the theoretical framework they established, the black hole transfers the “information” within itself to another black hole through a “wormhole”.)
Aside from the fact that black holes will shrink and disappear over time, there is also the issue of what is going on inside the black hole.
Hawking said that the “arrow of time” is of three kinds, not one. I wrote the first one before, the arrow of time arising from the laws of thermodynamics. The second is our psychological sense of time, the chronology created by our brain. The third is the “cosmological arrow.” That is, our universe continues to expand, not contract.
So, is there an arrow of time inside the black hole? Well, there must be very, very high entropy inside the black hole. If we define the arrow of time, that is, the direction in which it flows, as an increase in entropy in a thermodynamic sense, does the entropy increase or decrease inside the black hole?
Let’s continue on this topic.