When astronomers refer to “information” they are referring to all the content and relations within a certain piece of matter or process. The “information loss paradox” is based on the fact that physics tell us matter cannot be destroyed, but only transferred and transformed, and its information is preserved in something new. Water, for example, can become vapor or ice, but the information contained in its liquid form will be incorporated into the new stage.
However, for a long time, it seemed that black holes could capture all matter and light which came into their gravitational pull. Once information was sucked inside, it could never escape. And since light could never escape from the black hole, its rim constituted what was termed an “event horizon” – a sort of point of no return – beyond which any outside observer couldn’t see.
Forty years ago, Stephen Hawking proposed that black holes could eventually annihilate themselves through the evaporation of energy caused by radiating particles. Therefore, all the information inside a black hole would be permanently lost. However, this contradicted the laws of quantum mechanics and for decades it has remained a conundrum, which scientists haven’t been able to explain.
Last year, however, Hawking said that he had been wrong and that it was possible for information to be held in a black hole – or as he now calls them, “grey holes” – and then be released back into space. This, he said, was possible according to the laws of quantum physics, but a debate between scientists over whether and how this information could be retrieved is still ongoing.
Science Daily says that the new study may provide some answers to this. It quotes Dejan Stojkovic, PhD, associate professor of physics at the University at Buffalo, who said,
“According to our work, information isn’t lost once it enters a black hole. It doesn’t just disappear.”
Stojkovic said that even physicists, who believed that information was preserved inside black holes, have been unable to prove it mathematically. But, his new paper, he claims, gives precise calculations showing how information is preserved.
Phys.org explains that,
“Instead of looking only at the particles a black hole emits, the study also takes into account the subtle interactions between the particles. By doing so, the research finds that it is possible for an observer standing outside of a black hole to recover information about what lies within.”
“Interactions between particles” it continues, “can range from gravitational attraction to the exchange of mediators like photons between particles.”
Although such correlations are not new, many scientists have dismissed them as too small to be of any importance.
Stojkovic says the difference in his study is that,
“Our explicit calculations show that though the correlations start off very small, they grow in time and become large enough to change the outcome.”
This, he believes, marks a new step forward in answering the contradictions arising from the information loss paradox.
Stojkovic’s study called, “Radiation from a Collapsing Object is Manifestly Unitary,” was published on March 17 in Physical Review Letters, undersigned by PhD student Anshul Saini, who was its co-author.
