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Stephen Hawking speaks at the 2010 Television Critics Association press tour in Pasadena, California.
Credit: Frederick M. Brown / Getty Images
The latest article by Stephen Hawking has just been published by his colleagues in the pre-printed journal arXiv. The team had completed the research a few days before Hawking's death in March.
It was the third in a series of articles dealing with a concept that Hawking spent decades pondering: the paradox of black hole information. Here's how it goes:
Black holes are extremely dense objects that deform space-time and can form when stars collide or giant stars collapse on themselves. Classical physics suggests that nothing could escape a black hole, even in the light. But in the 1970s, Hawking proposed that black holes could have a temperature and slowly flee from quantum particles. This effect of "Hawking radiation" means that the black hole will eventually evaporate, leaving behind a void that will resemble that of every evaporated black hole no matter what it ate during its lifetime . [The Universe: Big Bang to Now in 10 Easy Steps]
This idea posed a problem: during its lifespan, the black hole swallowed a lot of information in the form of celestial objects, but where did this information pass? The laws of physics dictate that no information should be lost: if information existed in the past, we should be able to recover it. Hence the paradox.
In 2016, Hawking and his team proposed that black holes have "soft hairs" consisting of photons (light particles) or gravitons (hypothetical gravity particles) that store at least some of this information, previously reported by Live Science. . These soft hairs surround the "horizon of events" of the black hole, a limit to which nothing, not even light, can escape.
In the new paper, Hawking and his team found a mechanism – which relies on assumptions not yet established – to count the amount of inormation that soft hair can support. "This is consistent with the famous formula now inscribed on Stephen's gravestone," Andrew Strominger, lead author, told Live Science. The formula to which it refers is called the "Hawking Equation" and describes how black holes emit Hawking radiation.
When a black hole swallows an object, its temperature must change, which means that its entropy – or the disorder of its particles – must also change (higher temperatures mean that particles move faster, which means more disorder). In the new study, Hawking and his colleagues have shown that "soft hair" can indeed record the entropy of a black hole, according to The Guardian.
Malcolm Perry, another colleague of Hawking, professor of theoretical physics at the University of Cambridge, told the Guardian that the late physicist "knew the end result" of his work before his death and that, when Perry had it to him explained a few days later before, "he just produced a huge smile."
There's still a lot of information about how this soft hair stores information and about storing all or part of the information that is gobbled up by black holes.
"It's an excellent progress, but we still have a lot of work to do," Strominger said.
Originally posted on Live Science.
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