In 1974 Stephen Hawking argued that black holes destroy information. A black hole can become a cloud of radiation if it becomes evaporate. Information about what fell into the black hole is lost during the process.

The problem has been open for more than 45 years, but the pieces began falling into place in 2019. The idea that part of the inside of a black hole is hidden is the result of a new understanding of spacetime and how it can be rewired.

Black holes are the inescapable nature of these new ideas.

A One-Way Street

Trying to get out of a black hole is the most difficult thing to do. When spacetime collapses in on itself in a violent feedback loop of squeezing and stretching, black holes are formed. The abrupt end of an entire region of spacetime at the black hole is called the black hole singularity.

The area where escape is possible from the point of no return is divided by a fine line. The event horizon is this line. Light doesn't fall into the singularity at the farthest point from it. Nothing can escape from behind the event horizon, even if it were possible to travel faster than light.

There is a one-way nature to this boundary. It is a strong prediction of the general theory. When this theory interacts with the wild world of quantum mechanics, the danger begins.

Something Out of Nothing

Black holes can be redeemed from being greedy monsters thanks to quantum theory. When they consume a certain amount of energy, they give it back in the form of Hawking radiation.

absurdity is not the worst allegation made against quantum mechanics. There is a sea of particles that make empty space feel empty. These particles act as the glue that holds space time together.

Particle pairs that are close to a black hole become separated from one another. The newly divorced particles peel away from the horizon in opposite directions, with one member crashing into the singularity and the other escaping the black hole's gravity. The process draining the black hole causes it to get lighter and smaller as it emits energy from the incoming particles. The law requires the particles trapped inside to carry negative energy in order to account for the decrease in the black hole's energy.

The black hole appears to be burning away from the outside. The words on the book's pages are imprinted on the pattern of the light and ashes. The information is preserved in principle. If a black hole were a normal system like a burning book, the information about what falls into it would be hidden. This is difficult because of the quantum-mechanical relation among the particles.

Einstein's Enemy

The issue starts with the end of the union of the particles. They are connected by a quantum union even though they are not in the same place. Rejected as an absurdity by the physicists who predicted it, quantumentanglement is perhaps one of the strangest parts of our universe. Albert Einstein, Boris Podolsky and Nathan Rosen came up with the idea of a rebuttal to the theory of quantum mechanics. The theory must be incomplete because of Einstein's description of the phenomenon.

Two coins in a superposition, which is the quantum phenomenon of being in multiple states until a measurement is made, could be considered heads or tails. The chance of observing the pair of coins in either orientation, both heads or both tails, is one half, which is why the coins are facing heads and tails at the same time. The coins can't be found in opposite orientations. The measurement result of one coin is used to predict the result of the other coin. The randomness of the pair is perfectly correlated.

The scientists were concerned that the two coins didn't have to come into contact with each other. The coins could be in different parts of the universe. The results of the two random measurements were linked, and Einstein was not happy about it.

Einstein is in a position of being both correct and incorrect. Distinguishing quantum mechanics from classical physics is important to him. He got the wrong idea that correlation does not imply causality. The measurement outcome of one does not affect the other's fate. A new, higher degree of correlation is possible because of quantum mechanics.

Information Lost

If they were coins, they would be seen to be heads or tails because of the randomness of the radiation. We can't say anything about the contents of the black hole from the randomness of the radiation. Unlike the mechanical kind, an evaporating black hole does a thorough job.

The amount of entanglement between the radiation and the black hole can be measured by looking at the lack of information. One member of an entangled pair is random and the other members are all gone by the end of the process. The calculation of randomness goes by a number of names, and it grows with every emerging Hawking particle, peaking at a large value once the black hole has completely disappeared.

This pattern is different from what happens when information is kept. In such a case, the entropy has to fall to zero by the end of the process. When you think about a standard deck of cards, you can see that the rule is based on intuition. The number of possibilities on the other side of the cards is a measure of the amount of knowledge you have about them. There are 52 possibilities if you've only been dealt a single card. As you are dealt more cards, the entropy goes up to 500 trillion for 26 cards, which could be any of 500 trillion different combinations. When you have 51 cards, the possible mixes of cards go back up to 52. Once you have all the cards, you're certain of what you have, and there's nothing left in the deck. The Page curve applies to all normal quantum mechanical systems. The Page time is when the entropy peaks and begins to decline.

The destruction of information inside black holes is bad for physics because the laws of quantum mechanics say that information cannot be erased. The information paradoxes are caused by the fact that a sprinkling of quantum mechanics onto the description of black holes leads to a seemingly impossible discrepancy. The Page curve for the Hawking radiation was created by a more complete understanding of quantum-gravitational physics. This task was not easy.

An Eventful Horizon

The challenge was that tweaking the process was not enough to generate the Page curve and send the entropy back down to zero. The structure of a black hole needed to be dramatically changed.

We tried out several ways to modify the picture of black holes using a series of Gedanken experiments. In order to save the sanctity of information, either physics must be nonlocal or a new process must kick in at the Page time. The process would have to break the entanglement between the particle pairs. The option to make physics nonlocal was too radical.

It helps to preserve information, but it also poses a problem. The way the vacuum is maintained by a sea of entangled pairs of particles is due to empty space. At the cost of creating a wall of extremely high-energy particles, our group called it the firewall. The black hole wouldn't be able to enter if there was a firewalls at the horizon. Matter would be destroyed on contact. The black hole at the Page time would suddenly lose its interior and spacetime would end right there at the event horizon. The catch-22 means that any solution to the information paradoxes must destroy what we know about black holes. This would be the quagmire.

Fluctuating Wormholes

Our attempts to combine quantum mechanics and black hole physics were too timid, which led to the information paradoxes. We had to apply quantum mechanics to the black hole space time as well. Enhancing the quantum effects on spacetime is possible because of the large entanglement produced by the evaporation. It is subtle, but its implications are huge.

The path integral of quantum mechanics was used to consider the quantum nature of spacetime. According to quantum theory, particles don't just travel along a single path from point A to point B; they travel along all the different paths connecting the two points. A quantum superposition of all possible routes is described by the path integral. A quantum spacetime can evolve in different ways. If we start and end with two regular black holes, the quantum spacetime within them has a non zero probability of creating a short-lived wormhole that1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556

The chance of this happening is usually very low. The likelihood of wormholes increases when we carry out the path in the presence of multiple black holes. The realization came to me as a result of work I did with Thomas Hartman, Juan Maldacena, Edgar Shaghoulian, and Amirhossein Tajdini.

Islands beyond the Horizon

If some black holes are connected by wormholes, why? They changed the answer to how muchentanglement there is between the black hole and its radiation. In the presence of multiple copies of the system, the key is to measure thisentanglement. The trick is called the replica trick.

The interiors of the black holes can be swapped out with the help of temporary wormholes. What was in one black hole gets shoved into one of the other copies far away, and it assumes a new space time interior from a different black hole. Almost the entire interior of the black hole is encompassed by the island, which is the swapped region of the interior.

The doctor ordered the swap. One way to disentangle the black hole and its radiation is to swap out the island for one that doesn't have it.

A new formula for theentanglement of the radiation when applied to a single copy of the system has been created. The formula that was used to calculate the number of particles outside of a black hole is no longer used. The island and the exterior should not be counted towards the total. The prediction is based on the probability of the swap happening, which is equal to the area of the event horizon. The black hole shrinks as it shrinks. The island formula is used to calculate the Einstein radiation.

Taking the minimum between the island formula and the original calculation is the final step in calculating the entropy. We have been looking for the Page curve. The answer starts off smaller than the event horizon of the black hole, so we use the original formula. The new formula takes the baton from the old one when the black hole is gone.

This result solved two paradoxes with a single formula. The option of nonlocality was dismissed by theAMPS group. The inside of the island is supposed to be treated as part of the outside. The outside of the island becomes nonlocal. The information paradoxes are solved by revealing how black holes create the Page curve.

Think about how we got here. There is an incompatibility between the sequestering of information by the event horizon and the quantum-mechanical requirement of information flow outside the black hole that leads to the information paradoxes. Dramatic changes to the structure of black holes can be caused by subtle yet dramatic effects from fluctuations in the sky. There is a self-consistent picture that allows a black hole to retain its regular structure despite the presence of a powerful nonlocality. The island of the black hole should be considered a single unit with the outside radiation. Information can escape a black hole if it falls deeper into the island.

The implications of spacetime wormholes and the island formula are still being explored. While they make sure that the island is mapped onto the radiation, they don't make a prediction on how much of a difference it makes. wormholes are the missing ingredient in the original estimation of the randomness in the radiation and gravity is smart enough to comply with quantum mechanics. The power of gravity through these wormholes is just as frightening as the power of Einstein's mind. Einstein was correct at some point.