Information Paradox of Black Holes
What are Black Holes?
A black hole is a cosmic object in space with such great density that its gravity will capture everything that comes near it. The black hole's "event horizon" is the boundary of the region in which if object drift into, it will never escape from. Even light can not escape. Hence, the term black hole and its invisible characteristic.
This unusual characteristic produces some seemingly paradoxes.
The Information Paradox
It was thought that if materials fall into the black hole, it is lost
forever including any information about that material. It also means
that the internal state of black hole does not depend on the materials
that fall into it and that make it up.
An article from Ohio State University which calls Black Holes "fuzzballs" explains it well. It says ...
"That kind of uniformity violates the quantum mechanical law of reversibility, he [Samir Mathur] explained. Physicists must be able to trace the end product of any process, including the process that makes a black hole, back to the conditions that created it. If all black holes are the same, then no black hole can be traced back to its unique beginning, and any information about the particles that created it is lost forever at the moment the hole forms."
That is why many
physicists believe in the alternative which is that information can not
be lost. This contradiction is known as the information paradox of
So the question is "Does information get lost if it falls into a black hole?" This is analogous to asking "Are Black Holes Unique?" Or is every Black Hole the same?
Oglethorpe University article had once
listed the "information paradox" as among top ten unsolved problems in
physics. The article also explains what physicist mean by "information"
by saying ...
"As defined in physics, information is not the same as meaning, but simply refers to the binary digits, or some other code, used to precisely describe an object or pattern."
"Information" does not mean ideas, thoughts, or memories, it means the physical bits of the object. For surely, if a person fell into a black hole, the person's memories contained in the person's head would be lost.
In 1997, Stephen Hawkings (Cambridge) and
Kip Thorne (Caltech) had made a bet with John Preskill (Caltech).
Hawkings and Thorne was on the side that information is lost in a black
hole. Preskill believed that information is maintained. The wager was a
set of encyclopedia.
Resolution of the Information Paradox
The Ohio State University article suggests that
Preskill won the bet. Because with the rise of prominence of string
theory, information can be maintained in sub-atomic strings within the
black hole. The article says ...
"Since Mathur’s conjecture suggests that strings continue to exist inside the black hole, and the nature of the strings depends on the particles that made up the original source material, then each black hole is as unique as are the stars, planets, or galaxy that formed it. The strings from any subsequent material that enters the black hole would remain traceable as well. That means a black hole can be traced back to its original conditions, and information survives."
Michio Kaku also believes that information is not lost when he writes in his book Parallel Worlds ...
"That is why I personally feel that when someone finally calculates what happens to information when it disappears into a black hole in string theory, he or she will find that information is not really lost but subtly reappears somewhere else." [p230]
There are other possible resolution in which information can survive.
Black holes emit thermal radiation known as Hawking radiation due to quantum effects. In July 2004, Hawkings conceded to the bet and explained that information that falls into a black hole can come back out via quantum perturbations of the black hole's event horizon. Hawkings paid Preskill a baseball encyclopedia. Thorne however remain unconvinced and did not contribute to the award.
Kaku explains the the idea in Parallel World as ...
"if an object such as a book fell into a black hole, it might disturb the radiation field it emits, allowing information to leak back into the universe. The information contained within the book would be encoded in the radiation slowly seeping out of the black hole, but in mangled form. " [p230]
Some people theorize that perhaps the information that fell into the black hole passes through a wormhole and comes out of a "white hole" in a parallel universe? Hawkings think not. As quoted in physicsworld.com, Hawkings says that "The information remains firmly in our universe," he told the conference.
"I am sorry to disappoint science fiction fans, but if information is preserved, there is no possibility of using black holes to travel to other universes. If you jump into a black hole, your mass energy will be returned to our universe, but in a mangled form which contains the information about what you were like, but in an unrecognisable state."
Kaku says ...
"However, no one believes that this is the last word on the subject. Until string theory is fully developed, or a complete quantum gravitational calculation is made, no one will believe that the information paradox is fully resolved." [p230]
- Black Hole Information Paradox - Wikipedia