The center of the black hole is called a singularity. It is a dimensionless point of space-time. The singularity has neither length, width nor thickness.
A black hole is the remnant of a dead star. Some stars bigger than our sun, when they die, crush their remaining mass into a dimensionless point called a singularity.
Black holes are mysterious bodies. No information seems to be able to leave a black hole. It appears that information that enters a black hole is lost from the universe. If this is true it violates a very deep principle of physics called the Second Law of Thermodynamics, or entropy.
Entropy is also known as hidden information. Well, black holes are said to destroy information but entropy will only tolerate information being hidden in a black hole. It is an unprincipled thing and an unlawful thing that black holes seem to snuff the life out of information.
The Second Law of Thermodynamics insists that disorder is always increasing; increase in disorder, or entropy, means going from complex to simpler, and you can never go backwards from simpler to more complex in (and this is its main point) A CLOSED SYSTEM like the universe. Our universe is not open to the "outside" to receive any more energy than it started out with. The universe does not have an endless supply of energy. When what it has is completely used up it cannot remake any more or get any more. That's it.
Of course, there are local areas of open systems in the universe. For example, the solar system. In an open local region like our solar system, processes can start out simple and get more complex. Life is much much much more complex than say rocks. Superficially it seems something simple like a rock could not evolve into a complex living organism like a bacteria. But does a simple nonliving thing evolving into a living thing more complex like a virus violate the second law of thermodynamics? Let us see. Nonliving things are much simpler than a mitochondria and this organelle, that is in all of our cells, is much simpler than a bed bug. But entropy says "My law is inviolable, you are not allowed to go forward into the LAND OF COMPLEXITY, it is the private preserves of the GODS". So, does it take a miracle to create life, because only a miracle could violate the law of entropy?
Well! Hmm. . . But wait, the second law only applies strictly to closed systems like the universe so it does not necessarily apply to the Earth. The universe's entropy increases relentlessly as times goes marching forward. The amount of entropy you have today in the universe as a whole is greater than the amount of entropy that was in the universe yesterday. However, it is possible for a localized area like a star with planets orbiting around it to have things evolve from simple to complex. Take the Earth. It has a source of energy. Our Sun replenishes the energy that our Earth uses up. To go from simpler to more complex requires input of energy constantly. The Sun has been a constant source of energy for billions of years, and will continue to supply energy for many billions more. When the sun stops shining, about five billion years from now, life on Earth will be starved of energy and all life on the planet will go extinct from decay, unless some of us leave and find a different star. The Sun provides a constant source of energy so when things on Earth changes from a simpler thing like a bacteria to a eukaryote to a little worm, the law of entropy is not being violated.
So, yes, you can start out simple and become more complex because you have a dependable energy source. The total amount of entropy in the universe increases over time but local areas within it can go from a disordered state to a more ordered state when a local energy source like the Sun is available to replace the used up energy. Of course, stars do not have an inexhaustible energy supply and when they all burn out (in about a trillion years), God help us (!?)
Now, if you lock up a rabbit in a cage and he has eaten all his carrots he could die if he can't get replacement food soon. But there are sources of carrots on Earth that it can find, and if you let it free before it is too late it will replenish its energy supply and stave off death and decay, fending off entropy from its tendency to reduce us all to dust. However, entropy gets the last word when we die. Eventually each of us decays and return to dust.
ENTROPY IS HIDDEN INFORMATION
How does entropy relates to information? Entropy is hidden information. For example if you reduce a Pinto automobile to a pile of rust the information for reconstructing the car is still there in the rust pile, but almost a hundred percent of the time you reorganize the rust pile you will just get another rust pile. The Pinto information is hidden, and it would take practically an eternity to randomly fit the rust pieces together to get back a Pinto. The information is not irretrievable it is just too deeply hidden to find it by random reconstruction.
BACK TO BLACK HOLES:
For several decades it appeared to science that a black hole is an information sink-hole that was irretrievably sucking information from the universe. However Bekenstein
Well, a black hole's surface area measured in these bits, a measure of its entropy, is really a measure of the information hidden in its surface area. If one square centimeter of its surface area contains that much square Planck units, then a black hole is one mother of a haystack! Stephen Hawking showed that a black hole's entropy is one quarter its surface area, measured in square Planck units.
Why the big fuss? This implied that information trapped behind the black hole's spherical surface, its event horizon, is irretrievably lost from the universe, since entropy is hidden information. And this is why: Stephen Hawking also proved that a black hole had a temperature which was a startling realization to science. Scientists always believed that black holes did not have temperature; after all, there is nothing in a black hole to be hot. A black hole simply has a surface area consisting of a space-time fabric, and at its center is a dimensionless point; an empty structureless point. A black hole is simply a spherical space-time region with super powerful gravitational attraction. Hawking's theory
But if a black hole has nothing hot in it how come it has a temperature, since having a temperature simply means to be containing hot particles in it? A black hole, remember, is just an extremely highly warped spherical region of space-time created by super intense gravity produced by the singularity at its center. Hawking to the rescue.
A region of space-time devoid of real particles should have a temperature of absolute zero. However empty space has the "quantum jitters" due to virtual particle pairs. "Virtual" meaning we can't actually measure the energy of the particle pair's kinetic motion. Heat and temperature actually measures the kinetic energy of the random motion of real particles. A virtual particle pair, for example, would be an electron/positron. Hawking showed that virtual particle pairs just outside the black hole's event horizon’s spherical surface become disconnected from each other. The black holes super powerful gravity separates the electron from the positron. The electron escapes but the positron is sucked into the black hole. This process causes heat to radiate from the black hole, causing the black hole to continuously shrink until it disappears; disappearing with the information it sucked from the universe. Where is the information? It is gone, zippo, nonexistent.
This controversy splitted the scientific community. One side was lead by the quantum physicist and noble laureate, 't Hooft.
The, "Thou shalt not mess with the second law of thermodynamics" few, eventually showed that they were right. The information stolen from the universe is retrieved as a copy from the black hole. This newest theory is called black hole complementarity.
The concept of complementarity was first espoused by Niels Bohr.
When one observer asks the electron "You are a particle, aren't you?" it answers "YES, very much so!". But if another observer asks "You are a wave, aren't you?" the electron answers "YES, very much so!". Yet when the observer asks "Are you a particle and a wave simultaneously?", the electron's response is "I cannot answer both questions at the same time. If you ask me if I am a wave the answer is yes. On the other hand, if you ask me if I am a particle the answer is yes; ask me either question and I will tell you what you wish to hear!". Nothing that goes on in the 'world' of our experiences is anything like what goes on in the quantum 'world'. If you lived in the quantum world then at twelve noon, say, most of you can be in New Jersey and the rest of you can be everywhere in the universe! In the ordinary world outside the quantum realm that you and I live in, you can only be at one place at a given time. If you ask an electron "Where are you?" it will answer "I am riding on all of the rings of Saturn as we speak". Then you try to correct the electron by saying "You really mean to say you are riding ONE of the rings of Saturn as we speak, right?". The electron responds "You heard me. It's midnight and I am riding ALL the rings of Saturn. By the way, I am also presently at Blimpey's and Popeye's. How do you want your Philly Pepper Steak? I am going to have my Cajun Chicken spicy". Yes, nature in its quantum state is quite shockingly counter-intuitive, but it correctly explains how the Sun shines and how modern technology works. No, quantum theory does not make a lick of sense to anyone; it just works perfectly, and explains the universe beautifully!
The black hole has two sides to it that is complementary. Let us observe Stephen just as he is about to cross the black hole's event horizon. We watch Stephen and his wheelchair ripped apart and is atomized. But from Stephen's point of view he passes harmlessly across the event horizon through to the other side and performing wheelies in his chair; inside the black hole. Both views cannot be true at the same time. However Stephen is right: he is in one piece after he crosses the event horizon.
We are also right: Stephen is torn apart, atom by atom.
But how can Stephen be atomized and in one piece at the same time? You are right; he cannot be both at the same time. Yes, an observer outside can correctly claim he is being atomized, and yes, an observer on the inside can claim correctly that Stephen is in one piece. No one observer can see him atomized and also in one piece because this observer would have to be inside and outside of the black hole at the same time.
We on the outside cannot check with Stephen on the inside, and Stephen, on the inside, cannot compare notes with us on the outside.
Stephen says: "Hey guys I am fine!" but no one hears him because not even a cell phone signal, electromagnetic radiation, or a photon of light can escape the black hole’s super powerful gravity; he might as well be dead.
We say: "Stephen is dead”. We don’t actually observe Stephen atomizing but Albert Einstein’s physics of the general theory of gravity say he is. Stephen, as he nears the event horizon, actually just suddenly disappears from our sight. If we say “Poor devil he is about to be atomized as we speak!” and Stephen Hawking, from within the black hole says he is alive and well, we would never know it.
"I might as well be dead" Stephen says to himself.
Of course, Stephen eventually reaches the central singularity and is doomed.
What is being theorized is that a copy of the information that was Stephen was made and is returned to the universe in the form of "Hawking Radiation". No pun intended!
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