KOMPAS.com - Stephen Hawking menemukan cara untuk melarikan diri dari lubang hitam. Spesifiknya, cara bagaimana informasi tidak hancur ketika masuk ke dalam lubang hitam.

Para astrofisikawan selama ini dibingungkan dengan yang dinamakan paradoks informasi. Itu menjadi salah satu misteri terbesar dalam fisika modern.

Paradoks informasi ada karena perbedaan "pandangan" antara teori mekanika kuantum yang bekerja pada materi renik dengan teori relativitas umum dari Albert Einstein yang bekerja pada benda-benda besar.

Berdasarkan teori mekanika kuantum, benda-benda termasuk cahaya memang tidak dapat lolos dari lubang hitam tetapi informasi tentangnya tidak akan hancur.

Namun demikian, menurut teori relativitas umum, obyek sekaligus informasi tentangnya akan rusak begitu masuk ke dalam lubang hitam.

Dalam acara "Hawking Radiation Conference", Hawking mengatakan bahwa dirinya menemukan cara informasi bisa lolos dari lubang hitam dengan memperbaiki teori tentang informasi dan lubang hitam itu sendiri.

Berdasarkan hasil kerjanya dengan Malcolm Perry dari Cambridge University and Andrew Strominger dari Harvard University, Hawking menyatakan bahwa informasi sebenarnya tidak ditelan lubang hitam.

"Saya mengajukan teori bahwa informasi tidak ditelan sampai interior lubang hitam tetapi ada pada batasnya, event hirizon," ungkap Hawking.

"Jika kamu berada di dalam lubang hitam, jangan menyerah," imbuh penulis buku terkenal "A Brief History of Time" ini seperti dikutip Wired, Rabu (26/8/2015).

Hawking menguraikan, ketika informasi tentang obyek atau partikel melewati batas lubang hitam, maka informasi itu akan ditranslasikan menjadi hologram dua dimensi dan bertahan di perbatasan.

Translasi informasi menjadi hologram dua dimensi itu disebut super translasi. Dengan pandangan itu, Hawking mendamaikan perbedaan antara cara pandang mekanika kuantum dan relativitas umum.

Namun, pandangan Hawking itu juga menyisakan soal. Marika Taylor, fisikawan teoretis dari University of Southampton mengatakan bahwa bahkan tidak jelas apakah memang ada yang disebut "batas" dan "bagian dalam" lubang hitam.

Lantas, bagaimana hologram bisa bertahan di tepian lubang hitam. "Tak ada satu pun yang mengetahui bagaimana ini bisa terjadi," katanya seperti dikutip BBC, kemarin.

Stephen Hawking's fantastic vision of black holes may solve 40-year paradox


(CNN)Want to know what happens after you pass through a black hole? Just look around you. You might land in another universe that is similar to our own, if Stephen Hawking is right. Or in a very different one.

The iconic astrophysicist joked about it this week as he unveiled a proposed solution to a deeply fundamental paradox that has confounded scientists and mathematicians for 40 years.

"The hole would need to be large and if it was rotating it might have a passage to another universe. But you couldn't come back to our universe," he said through his speech synthesizer. "So, although I'm keen on space flight, I'm not going to try that."

Hawking has Lou Gehrig's disease, also called ALS, and is confined to a wheelchair, but he has taken a zero-G ride in an airplane and has said he wants to personally travel into space.

Theories collide

"Black holes ain't as black as they are painted," Hawking said. They are not the absolute everything-crushers that imprison matter for eternity, as once thought. That's where his solution comes in.

In our understanding of reality -- from infinitesimal subatomic particles to the infinite vastness of space-time -- two theories have explained so much, but have also been at odds with each other in key points.

When it comes to black holes, Albert Einstein's theory of relativity postulates that information about particles passing through them is destroyed. But the equally important quantum theory says that's impossible -- information from the universe can never vanish.

"Since the 1970s, efforts to combine these two theories have led to mathematical nonsense and have become known as the information loss paradox," said a statement from the conference built around Hawking's new solution.

Science history

The conference itself was a new page in science history.

Famed cosmologist Laura Mersini-Houghton from the University of North Carolina-Chapel Hill assembled some of the founders of modern physics -- many of them Nobel laureates -- to hear Hawking and contribute their brain power at KTH Royal Institute of Technology in Stockholm, Sweden.

It was also a gathering of friends. Hawking's achievements and those of the other scientists have been made possible through the advances of their cumulative work. Hawking presented to an intimate group of about three dozen scientists.



Hologram of matter

In a way, Hawking's solution to the information loss paradox says that one thing is really happening, but that it gives the appearance that the other thing is happening.

The information is not passing through the black hole, but is being stored on what's called its "event horizon" in a "super translation."

Black holes are not objects like balls, but if we picture them that way, we might describe the event horizon as its surface and the super translation a kind of picture painted on the surface by the particles passing through.

"The idea is the super translations are a hologram of the ingoing particles," Hawking said. "Thus they contain all the information that would otherwise be lost."

Bottomless pit of gravity

Black holes defy everyday human perception.

When some massive stars die, they collapse in on their own herculean gravity so extremely that they create an area of space-time that is a "bottomless pit that swallows anything approaching too closely," the organizers say. "Not even light can escape them, since their gravitational pull is so infinitely powerful."

And the super translation is constant, swift, and forceful as matter pours through the black hole.

As a result, the information ends up "in a chaotic and useless form," Hawking said. "This resolves the information paradox. For all practical purposes, the information is lost."

It could appear as if it had been destroyed.
Study shows 'The Universe is slowly dying'

Stephen Hawking Hasn't Solved the Black Hole Paradox Just Yet

their formation. A black hole may arise, for example, from the death of a large star that has run out of fuel for nuclear fusion and collapsed under its own gravity. According to quantum mechanics, the black hole should store the information about the star that gave birth to it as well as any matter that has fallen in since. But if the black hole someday evaporates, it would seem that information would be destroyed.

Physicists have tried to find a way for the information to escape the black hole’s demise via the Hawking radiation. The problem with this scenario, however, is that black holes appear to have no way to impart information to this radiation. Black holes, in fact, are very simple objects according to the theory of general relativity, which first predicted their existence. They have only three properties: mass, charge and angular momentum; other than those quantities, they have no characteristics, no other details—in physicists’ vernacular, they have “no hair.”

Hawking unveiled a potential “answer” to the information-loss paradox—a way to give black holes hair—during a presentation given at the KTH Royal Institute of Technology in Stockholm on August 25: “I propose that the information is stored not in the interior of the black hole as one might expect but on its boundary, the event horizon,” he said. The event horizon is the theoretical border of a black hole, a spherical “point of no return” for incoming matter. Hawking further suggested that the information resides in so-called “supertranslations” on the event horizon, which are imprints that would cause a shift in the position or the timing of the particles that are emitted via Hawking radiation. These supertranslations would be formed by the particles of the dead star and any other matter that fell into the black hole when they first crossed the event horizon. Hawking admitted that the information would not be readily retrievable but maintained that it at least would not be destroyed, thereby resolving the paradox. “The information about the ingoing particles is returned but in a chaotically useless form,” he said. “For all practical purposes the information is lost.”

A “greater state of confusion”

Most physicists say it is too early to know whether Hawking’s idea is a real step forward. His presentation was brief; he and two collaborators—Cambridge physicist Malcolm Perry and Andrew Strominger of Harvard University—plan to publish a paper in coming months detailing their idea further. “I think [the idea] has promise,” says Sabine Hossenfelder, a physicist at the Nordic Institute for Theoretical Physics who attended the talk. “But so far it is not a full solution.”

Hawking described the basics behind his idea that supertranslations can encode information. “That may be,” Hossenfelder adds, “but it is somewhat unclear right now how this happens and how efficiently it happens. Also, the mechanism they have to store information actually allows them to store too much information!”

And supertranslations are hardly the only solution on the table. In recent years physicists have come up with a host of ideas to solve—or further complicate—the information-loss paradox. “To be completely honest I must say that [the paradox] is in an even bigger confusion now than it has ever been before,” observes physicist Ulf Danielsson of Sweden’s Uppsala University, who was in attendance for the presentation. “With Hawking saying that he has solved the information paradox, to me that means now there’s another ingredient that is coming in, and the question is: Will this actually resolve anything or just leave us in an even greater state of confusion? I’m not really sure.”

Larger mysteries

Whatever happens to Hawking’s scenario, the topic will continue to be a hot-button issue in physics. The question is not just an arcane consideration about black holes—it is deeply tied to larger mysteries about the nature and origin of the universe. And to answer the question physicists will probably need not just a better understanding of black holes but a full theory of quantum gravity—a theory that has so far been missing.

Black holes are perplexing objects in part because they invoke two different theories of nature—quantum mechanics, which governs the subatomic world, and general relativity, which describes gravity and reigns on large cosmic scales. Yet the two theories are fundamentally incompatible. What physicists need is a way to describe gravity according to quantum rules. By invoking both quantum mechanics and relativity, the information-loss paradox “gives us a chance to focus what we know and what we don’t know and to try to work out the implications of different hypotheses about quantum gravity,” says physicist Lee Smolin of the Perimeter Institute for Theoretical Physics in Ontario.

Smolin and Hossenfelder recently collaborated on a review paper that summarized all the various possible solutions to the information-loss puzzle and concluded that they mostly fall into six categories, each taking a different tack to resolve the apparent paradox. One possibility is that information really is destroyed—perhaps that prohibition of quantum mechanics is wrong. Another is that inside a black hole a new region of spacetime forms a sort of baby universe, in which information is preserved. Other solutions involve theoretical objects called “white holes”—the opposite of black holes, in which the flow of time is reversed and nothing can fall in, only out (information included). Then there is the chance that black holes never quite evaporate—they only shrink down to incredibly small sizes, thereby preserving the information. Or perhaps information is somehow copied from inside a black hole to outside, so that when the black hole is destroyed the outside copy remains. And finally there are proposals in which information is encoded on a black hole’s horizon in various ways—Hawking’s idea falls into this category. “I think the real situation is unfortunately that we have a puzzle and we have several ways out and we just don’t know enough,” Smolin says. “It might even be that in nature there are different kinds of black holes and some resolve the puzzle in one way and others resolve it in another.”

However the solution turns out, it may affect not just black holes but also a theoretically related event—the big bang. The small, dense state of black holes is very similar to the presumed situation of our universe at its birth, and many of the same physical considerations apply. In both cases the mathematics currently predict a “singularity”—a point of spacetime that is infinitely dense and infinitely small. Some physicists say these infinities are proof that the equations are wrong whereas others maintain that the singularity is a physical reality. If the resolution of the information-loss paradox comes from a quantum theory of gravity that eliminates the singularity, it could imply a different origin for our universe. “Is there still a first moment of time,” Smolin asks, “or does the singularity get eliminated and turn into a bounce so that there was an era of the universe before the big bang?”