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Stephen Hawking: black holes do not exist (as we understood them)

Black hole

A January 24, 2014 story in Nature reports that Stephen Hawking, the famous theoretical physicist, has announced that there are no black holes, at least as people have been given to understand. The existence of bodies from which no light escapes is incompatible with quantum theory.

Hawking is attempting to answer a question that has vexed the theoretical physics community for the past couple of years. Hitherto it was assumed that black holes have an “event horizon” beyond which nothing, not even light, could escape. An astronaut passing through the event horizon would not be aware of what was happening until he was crushed in the black hole’s core.

However a recent though experiment suggests that in order for an event horizon to be compatible to quantum physics, the astronaut instead would be burnt to a cinder. However for this to take place, Einstein’s General Theory of Relativity would have to be flouted.

Hawking has suggested a new model for how black holes, as such, work.

“Quantum mechanics and general relativity remain intact, but black holes simply do not have an event horizon to catch fire. The key to his claim is that quantum effects around the black hole cause space-time to fluctuate too wildly for a sharp boundary surface to exist.

“In place of the event horizon, Hawking invokes an ‘apparent horizon’, a surface along which light rays attempting to rush away from the black hole’s core will be suspended. In general relativity, for an unchanging black hole, these two horizons are identical, because light trying to escape from inside a black hole can reach only as far as the event horizon and will be held there, as though stuck on a treadmill. However, the two horizons can, in principle, be distinguished. If more matter gets swallowed by the black hole, its event horizon will swell and grow larger than the apparent horizon.”

Eventually the apparent horizon can dissolve, releasing the trapped light and matter, albeit in a different form.

All of this may seem to be more than a little complicated for the lay person. But rest assure it will be argued about and chewed over by the theoretical physics community for some time to come. In any event a lot of science fiction stories about people being trapped in black holes may have become obsolete.

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