Black hole theory not so black and white, says Stephen Hawking

Black hole theory not so black and white, says Stephen Hawking

Stephen Hawking attempts to make peace between quantum mechanics and general relativity

Theoretical physicist Stephen Hawking recently published a short, two-page paper in which he questions his previous assertions regarding black holes. In it, he states that it in fact may be possible to escape the extreme gravitational pull of a black hole. Or maybe he doesn’t. The scientific community isn’t yet sure what to make of the release, but if black holes do behave the way Hawking suggests, it may lead to a greater understanding of quantum physics and general relativity.

Stephen Hawking caused a stir in 1974 when he began applying quantum mechanics to black holes, because quantum mechanics doesn’t integrate well the the theory of general relativity. In particular, Hawking’s application of quantum mechanics suggested that rather than black and eternal, black holes are really more “gray,” emitting small amounts of radiation until they eventually shrink and evaporate. When they go, everything with them including light and information goes too.

Adherents to the general relativity theory took umbrage with this, as they believe that information about matter cannot be destroyed. Hawking held fast to his theory until recently, when he admitted he had miscalculated and conceded that perhaps black holes only temporarily hold on to this information, releasing it as they evaporate.

The paper released January 22, titled “Information preservation and weather forecasting for black holes,” contains no calculations and has not yet been peer reviewed. It centers around the idea of a black hole’s “event horizon,” a sort of “point of no return” beyond which nothing, not even light, can escape. They’re what cause the rift between quantum mechanics and general relativity, known as the “firewall paradox.” Essentially, anything leaving a black hole would create massive amounts of energy upon exit, creating a wall of fire at the event horizon that would consume anything falling towards the center. This is what goes against general relativity, as according to it, crossing a black hole’s event horizon should be uneventful.

Hawking’s solution? Just eliminate the idea of black holes altogether, or at least as we currently understand them.

The idea would help calm the commotion surrounding the two grand theories by eliminating the crux of the dispute – the event horizon. Hawking suggests that what some call an event horizon and others a firewall are more or less the same thing. He instead proposes an “apparent horizon,” a surface that traps light but can take on many forms depending on quantum fluctuations.

“The absence of event horizons means that there are no black holes — in the sense of regimes from which light can’t escape to infinity,” Hawking writes.

“The picture Hawking gives sounds reasonable,” says Don Page, a physicist and expert on black holes at the University of Alberta in Edmonton, Canada, who collaborated with Hawking in the 1970s. “You could say that it is radical to propose there’s no event horizon. But these are highly quantum conditions, and there’s ambiguity about what space-time even is, let alone whether there is a definite region that can be marked as an event horizon.”

The point of Hawking’s paper is to resolve the firewall paradox, finding a way to make quantum mechanics jive with general relativity. Eliminating event horizons also eliminates the firewall, which would still mean quantum information is “lost.” Hawking satisfies this by suggesting that since the structure of a black hole is so complex and variable below the horizon, information that escapes is altered drastically. It isn’t “lost” in the sense that it ceases to exist, only in the sense that it’s nothing like what it was before it entered the black hole. An information zombie, if you will.

“It will be like weather forecasting on Earth,” Hawking writes. “One can’t predict the weather more than a few days in advance.”

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