Mysterious “islands” help to explain what happens to information that falls into a black hole
Theoretical physics has been in crisis mode ever since 1974, when Stephen Hawking argued that black holes destroy information. Hawking showed that a black hole can evaporate, gradually transforming itself and anything it consumes into a featureless cloud of radiation. During the process, information about what fell into the black hole is apparently lost, violating a sacred principle of physics.
There is a fine line within the collapsing region that divides the area where escape is possible from the point of no return. This line is called the event horizon. It is the outermost point from which light barely avoids falling into the singularity. Short of traveling faster than light—a physical impossibility—nothing can escape from behind the event horizon; it is irretrievably lodged inside the black hole.
Particle pairs that straddle the event horizon of a black hole, however, become forever 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 gravitational pull in the form of Hawking radiation. This process is draining for the black hole, causing it to get lighter and smaller as it emits energy in the form of the outgoing particles.
The irony is that Einstein himself is in a superposition of being both wrong and right. He was right to recognize the importance of entanglement in distinguishing quantum mechanics from classical physics. What he got wrong can be summed up with the truism “correlation does not imply causation.” Although the fates of the particles are inextricably correlated, the measurement outcome of one does not cause the outcome of the other.
The destruction of information inside black holes spells disaster for physics because the laws of quantum mechanics stipulate that information cannot be obliterated. This is the famous information paradox—the fact that a sprinkling of quantum mechanics onto the description of black holes leads to a seemingly insurmountable inconsistency. Physicists knew we needed a more complete understanding of quantum-gravitational physics to generate the Page curve for the Hawking radiation.
Fluctuating Wormholes Eventually my colleagues and I realized that both the information paradox and the newer firewall paradox arose because our attempts to meld quantum mechanics and black hole physics were too timid. It wasn't enough to apply quantum mechanics to only the matter present in black holes—we had to devise a quantum treatment of the black hole spacetime as well.
The relevant physical effect of these temporary wormholes is to swap out the interiors among the different black holes. This happens literally—what was in one black hole gets shoved into one of the other copies far away, and it assumes a new spacetime interior from a different black hole. The swapped region of the black hole interior is called the island, and it encompasses almost the entire interior up to the event horizon.