what is black hole information paradox?
352119
The black hole information paradox results from the combination of quantum mechanics and general relativity. It was a contentious subject for science since it violated a commonly assumed tenet of science - that information cannot be destroyed. See Liouville's theorem (Hamiltonian) and unitary transformation.\n\nIn 1975, Stephen Hawking and Jacob Bekenstein showed that black holes should slowly radiate away energy, which poses a problem. From the no hair theorem one would expect the Hawking radiation to be completely independent of the material entering the black hole. However, if the material entering the black hole were a pure quantum state, the transformation of that state into the mixed state of Hawking radiation would destroy information about the original quantum state. This violates Liouville's theorem and presents a physical paradox.\n\nMore precisely, if we have an entangled pure state and we throw in one part of the entangled system into the black hole while keeping the other part outside, we get a mixed state after we take the partial trace over the interior of the black hole. But since everything within the interior of the black hole will hit the singularity within a fixed finite time, the part which is traced over partially might "disappear", never to appear again. Of course, we don't really know what goes on at singularities once quantum effects are taken into account, which is why this is conjectural and controversial.\n\nHawking was convinced however because of the simple elegance of the resulting equation which 'unified' Thermodynamics, Relativity, Gravity and Hawking's own work on the Big Bang. This annoyed many physicists, notably John Preskill, who in 1997 bet Hawking and Kip Thorne that information was not lost in black holes.\n\nThere are various ideas about how the paradox is solved. Since the 1998 discovery of the AdS/CFT correspondence, the predominant belief among physicists is that information is preserved and that Hawking radiation is not precisely thermal but receives quantum corrections. Other possibilities include the information being contained in a Planckian remnant left over at the end of Hawking radiation or a modification of the laws of quantum mechanics to allow for non-unitary time evolution.\n\nIn July 2004 Stephen Hawking announced a theory that quantum perturbations of the event horizon could allow information to escape from a black hole, which would resolve the information paradox. Basically, his argument assumes the AdS/CFT correspondence which states that an AdS black hole is dual to a thermal conformal field theory, which is unitary. However, as of 2004 the full details of the theory have yet to be published, so most peers are reserving judgment before accepting the result. When announcing his result, Hawking also conceded the 1997 bet, paying Preskill with a baseball encyclopedia (ISBN 189496327X) 'from which information can be retrieved at will'. Thorne, however, remains unconvinced of Hawking's proof and declined to contribute to the award.\n\n\n[edit]\n\nThe Equation\n\nEntropy of a black hole.\n\n\nS = &#92;frac{c^{3}A}{4 &#92;hbar G}\n\n\nS = entropy, c = speed of light, A = surface area, ħ ("h-bar") is the reduced Planck's Constant (or Dirac's Constant), G = constant of gravitation.
901382
You have this slightly wrong. The correct formula is:\n\nS=Akc^3/(4 hbar G)\n\nThis is a statement on the entropy of black holes. k is Boltzmann's constant, c is the speed of light, hbar is plank's constant divided by 2 pi, G is Newton's gravitational constant and A is the surface area of the black hole's event horizon.\n\nNotice that this means that the entropy of a black hole is proportional to the surface area of it's event horizon, rather than the volume it encloses as would normally be expected.
1059153
A black hole is a singularity in spacetime. In other words, its a place where the stress energy caused by a gravitating mass is so large that spacetime curves to a single point.\n\nIt is not possible to know what happens on the other side of a black hole because all of the laws of physics are discontinuous at its boundary. Thats not to say that they change inside the black hole, its just to say that there is no experiment that can be done or observation made outside the black hole that can ever tell you what is going on inside it.\n\nFalling into a black hole is odd. As the gravitational field increases, time relative to places with a lower gravitational field runs slower. At the event horizon of the black hole (just before you fell in) the escape velocity is the speed of light, and so it would be akin to travelling at the speed of light (which is impossible). Time for you would extend infinitely, even those outside would see you fall in.
238837
Decades ago the mathematician and physicist Stephen Hawkins set out to disprove the great myth of the Black Hole. In his attempt to disprove the theory of the Black Hole he instead ended up proving there existence through mathematical model. When we think of a telescope, we instinctively think of an optical telescope. Today we have radio scopes, X-Ray scopes, gamma ray scopes and the list goes on. I do not know of a single image of a real live Black Hole that has been taken. What they look for is the perbutations that surround a Black Hole based on mathematical model. I hope this helps.
1098294
no. The definition of black hole is that what comes in, never comes out anymore.\n\n"What goes in must come out?" is a saying, not a law of physics
31855
Like the posters above have said, the known laws of physics break down inside a black hole. Anything which passes inside the event horizon is no longer visible to anyone outside. What happens inside is just pure speculation, take your pick:\n\na. Matter, light and other trapped energy is compressed to incredible density\n\nb. Everything breaks down into its ultimately basic constituents (quarks, strings, whatever).\n\nc. Everything passes through a 'worm hole' to a 'white hole' somewhere else in the universe or in a different universe. A white hole (no one has ever observed one) is the opposite of a black hole, where everything is emitted out. It would appear like an incredible sourc of light.\n\nd. Black holes accumulate matter and energy, and ultimately the whole universe is concentrated into one single black hole. Suddenly "Let there be light", and it all explodes in another Big Bang to form a new universe. This is also called the theory of oscillating universes.
57542
Scientists think that, at some point in the very distant future, all of the mass in the universe will be dominated by four or five supermassive black holes.  At first glance, this doesn't square with the second law of thermodynamics (since that's a rather low entropy state), so someone postulated that there would be such a thing as a lighthole which would re-emit everything that fell into a black hole.\n\nThat was utter nonsense.\n\nStephen Hawking put his brain to work on this problem, and solved it in a day.  He realized that, as predicted by Einstein's famous equation, gravitational fields can spontaneously create pairs of particles (one being normal matter, and the other being anti-matter).  Under normal circumstances, the matter-anti-matter pair would annihilate, but if the pair forms on the event horizon of a black hole, one of the particles would be drawn into the black hole, while the other would be emitted into space.  By doing this, the black hole has expended some of its gravity, and therefore its mass.\n\nThe answer to the conundrum is that Black Holes are slowly evaporating through this process, and we've named it the Hawking radiation, accordingly.  If the Universe is ever dominated by a handful of supermassive black holes, that won't violate the Second Law of thermodynamics since they're slowly falling apart anyhow.\n\nThere is no need for a white hole to exist, nor is there any observational evidence even suggesting that they might.
377533
None. electron hole pairs is simply absence of electron in an atom or molecule. Black hole is a collapsed matter in the Universe due to strong gravity.
554770
A black hole is believed to be a neutron star that collapsed in itself because of extreme gravity. The gravity would get so strong that it forces even time and space into itself including light (that's why it's called black). Also associated with a "wormhole" and figured to be a portal to parallel universes or looped back to this universe in a different time, after the theory of the Einstein-Rosen-Bridge.\nI don't know if someone tried to measure the value of the gravity or if there is even a speculated formula but I don't think so.
78383
black holes are connescted with wormholes, which could connest one part of the universe to another. It is proven that when an objext is moving close to the speed of light, time slows down. Going through a wormhole your traveling that fast and since every one else is traveling at normal time, you are staying younger longer therefore you could go into the future where everyone else couldnt
418807
It's still currently debatable whether you actually can get information out of a black hole.
268153
Three cosmic enigmas, one audacious answer\n09 March 2006 \nExclusive from New Scientist Print Edition \nZeeya Merali \n\n \n\n \n\n  \nDARK energy and dark matter, two of the greatest mysteries confronting physicists, may be two sides of the same coin. A new and as yet undiscovered kind of star could explain both phenomena and, in turn, remove black holes from the lexicon of cosmology.\n\nThe audacious idea comes from George Chapline, a physicist at Lawrence Livermore National Laboratory in California, and Nobel laureate Robert Laughlin of Stanford University and their colleagues. Last week at the 22nd Pacific Coast Gravity Meeting in Santa Barbara, California, Chapline suggested that the objects that till now have been thought of as black holes could in fact be dead stars that form as a result of an obscure quantum phenomenon. These stars could explain both dark energy and dark matter.\n\nThis radical suggestion would get round some fundamental problems posed by the existence of black holes. One such problem arises from the idea that once matter crosses a black hole's event horizon - the point beyond which not even light can escape - it will be destroyed by the space-time "singularity" at the centre of the black hole. Because information about the matter is lost forever, this conflicts with the laws of quantum mechanics, which state that information can never disappear from the universe.\n\nAnother problem is that light from an object falling into a black hole is stretched so dramatically by the immense gravity there that observers outside will see time freeze: the object will appear to sit at the event horizon for ever. This freezing of time also violates quantum mechanics. "People have been vaguely uncomfortable about these problems for a while, but they figured they'd get solved someday," says Chapline. "But that hasn't happened and I'm sure when historians look back, they'll wonder why people didn't question these contradictions."\n\n“People have been uneasy about these problems with black holes, but figured they'd get solved. That hasn't happened”While looking for ways to avoid these physical paradoxes, Chapline and Laughlin found some answers in an unrelated phenomenon: the bizarre behaviour of superconducting crystals as they go through something called "quantum critical phase transition" (New Scientist, 28 January, p 40). During this transition, the spin of the electrons in the crystals is predicted to fluctuate wildly, but this prediction is not borne out by observation. Instead, the fluctuations appear to slow down, and even become still, as if time itself has slowed down.\n\n"That was when we had our epiphany," Chapline says. He and Laughlin realised that if a quantum critical phase transition happened on the surface of a star, it would slow down time and the surface would behave just like a black hole's event horizon. Quantum mechanics would not be violated because in this scenario time would never freeze entirely. "We start with effects actually seen in the lab, which I think gives it more credibility than black holes," says Chapline.\n\nWith this idea in mind, they - along with Emil Mottola at the Los Alamos National Laboratory in New Mexico, Pawel Mazur of the University of South Carolina in Columbia and colleagues - analysed the collapse of massive stars in a way that did not allow any violation of quantum mechanics. Sure enough, in place of black holes their analysis predicts a phase transition that creates a thin quantum critical shell. The size of this shell is determined by the star's mass and, crucially, does not contain a space-time singularity. Instead, the shell contains a vacuum, just like the energy-containing vacuum of free space. As the star's mass collapses through the shell, it is converted to energy that contributes to the energy of the vacuum.\n\nThe team's calculations show that the
557703
Black holes are huge concentrations of mass in a very small area.  So small that it is too small to contain conventional matter as we understand it.  There is a perimeter around a black hole known as the event horizon.  Beyond this point, nothing, not even light can escape the gravitational pull of a black hole.  If you were to be able to stand on the event horizon and have telescopic vision like Superman, looking tangent to the event horizon, you would see the back of your head.
661081
A black hole is a concentration of mass great enough that the force of gravity prevents anything past its event horizon from escaping it except through quantum tunnelling behaviour (known as Hawking Radiation). The gravitational field is so strong that the escape velocity past its event horizon exceeds the speed of light. This implies that nothing, not even light, inside the event horizon can escape its gravity. It is, however, theorized that wormholes can provide an exit path for energy or matter. The term "black hole" is widespread, even though it does not refer to a hole in the usual sense, but rather a region of space from which nothing can return.
971309
The best way to know that you've moved inside the event horizon of a black hole is by finding that you can no longer communicate with the rest of the universe. For instance, if you were in a probe launched by a nearby mother ship and passed inside the event horizon, all radio contact with the mother ship would be totally lost because nothing can escape from inside the event horizon.
899210
Currently nobody really knows. Einstein's general theory of relativity tells what the gravity from a black hole is, but it doesn't tell anything about what is inside it. The only thing which is known for sure is that an object collapses to a black hole if it reaches a certain density. In the universe that happens for stars with sufficiently high masses. They consist of a lot of particles, but what happens to them after the star has collapsed to a black hole is simply unknown. Part of the problem is that it lies in the nature of the black hole that no signal can escape from it (not even light) so it is extremely difficult to get any information of what's inside a black hole (some quantities can be determined though: A black hole has a well defined mass which can be measured because of its gravitation). A comprehensive theory for what happens to a star when it collapses to a black hole would at least have to incorporate Einstein's theory as well as quantum mechanics and to date such a successful unified theory of that kind hasn't been achieved (although there are some proposals and vague ideas, you have probably heard about superstring for instance).
503211
The X-ray source in the constellation Cygnus, aptly named Cygnus X-1, is the best candidate for a black hole that we know of. Most Scientists now agree that it is a black hole. Stephen Hawking won a nobel prize for demonstrating that black holes do not in fact absorb everything that comes near them, as was previously thought, they can and do emit some particles from near their 'event horizons'. This is known as Hawking radiation.