Hawking delivered a lecture in 2007 for NASA's fiftieth anniversaryNASA/Paul alers

Seven months following his death, Professor Stephen Hawking’s final work has been published. A continuation of his groundbreaking research on black holes and Hawking radiation, the new scientific paper illustrates that some of the information engulfed by black holes can be preserved.

Changes in a black hole’s temperature and entropy, or disorder, can preserve some of an object’s information upon black hole consumption. The new paper was co-authored by Sasha Haco, a PhD student at Cambridge, Professor Malcolm J. Perry, and Harvard’s Professor Andrew Strominger.

The paper demonstrates the possibility of recording black hole entropy changes via what they dub “soft hair”. The term refers to the cloud of photons, or particles of light, lying on a black hole’s periphery. These photons respond to the profound gravitational force emanating from the black hole. By recording “soft hair” behaviour, entropic information can be gathered.

Professor Perry, who works in theoretical physics at Cambridge, told the Guardian, “what this paper does is show that ‘soft hair’ can account for the entropy”. However, he went on to add, “we don’t know that Hawking entropy accounts for everything you could possibly throw at a black hole, so this is really a step along the way”.

Stephen Hawking was a hugely influential physicist at Cambridge and winner of countless awards and honours. Up until his death he was director of research at the University’s Centre for Theoretical Cosmology.

A pioneer in his field, Hawking predicted in 1974 that black holes emit blackbody radiation, named Hawking radiation. Hawking radiation leaks from black holes and can account for their shrinking out of existence. His theoretical work for the first time linked together branches of quantum mechanics and general relativity.


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However, the evaporation of black holes throws up profound questions regarding the nature of information. Quantum mechanics rules that information is never lost, but is encoded and conserved.  On the other hand, the evaporation of black holes seemingly requires physical information to be permanently destroyed. This conundrum is known as the black hole information paradox and has puzzled physicists for decades.

The new paper seeks to address this information paradox. Perry emphasised that this “is definitely not the entire answer” but there are “slightly fewer puzzles than we had before”.

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