Stephen Hawking: 'There Are No Black Holes'

ananyo writes "Stephen Hawking has proposed a new solution to the black-hole firewall paradox, which has been vexing physicists for almost two years. The paradox troubles physicists because if the firewall scenario is correct, Einstein's general theory of relativity is flouted. But the classical theory black hole cannot be reconciled to the quantum mechanical prediction that energy and information can escape from a black hole. Now Hawking has proposed a tantalizingly simple solution to the paradox which allows both quantum mechanics and general relativity to remain intact — 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 spacetime to fluctuate too wildly for a sharp boundary surface to exist. As Hawking writes in his paper, 'The absence of event horizons mean that there are no black holes — in the sense of regimes from which light can't escape to infinity.'"

Comments

Apparent Horizons, but no Event Horizons

[PvtVoid]

In this picture, there would still be astrophysical black holes in every meaningful sense of the word, i.e. condensed objects from which light would not escape. Such objects would have an "apparent horizon", which can be defined locally by the property that all lightlike geodesics are ingoing.

What these black-hole-like objects would not have is an Event Horizon, which is a global property of the spacetime, and is only defined by the behavior at asymptotic infinity. It's a neat resolution of the whole mess: way more sensible than firewalls.

But it's still just hand-waving -- note that the entire argument relies on AdS/CFT, which assumes the black holes are embedded in de Sitter space, which has a negative cosmological constant and is most definitely not the kind of spacetime we live in. And AdS/CFT is itself an unproven conjecture, although it is supported by many specific example cases. Until somebody comes up with a theory of quantum gravity, this stuff is all guesswork. Caveat emptor.

Re:But it is horribly wrong anyway.

[RaceProUK]

Newtonian Gravity isn't correct either, we still use it in limited scope. It doesn't mean that Relativity is prevented from the same usage.

But it is still far from correct and the day people finally accept that and move on, maybe some actual research will get done. Dark Matter and Dark Energy are literal blackholes of knowledge that rips Relativity apart in every sense of the metaphor.

There is hardly a contradiction, just you putting meaning where there is none.

You know that building you live in? Built with Newtonian mechanics. That's why it stays up.

And the sat-nav in your phone? That uses general relativity. If it didn't, it wouldn't be able to locate you in the right country, let alone on the right street.

Newtonian mechanics and general relativity have been proven correct many times over. What they are though is incomplete. And there's a mountain of research happening right now to work out why.

Re:SubjectsInCommentsAreStupid

[SirGarlon]

There is huge variety within the Christian religion. Quaker, Roman Catholic, Pentacostal, Amish, Russian Orthodox, Mormon, Coptic, Presbyterian, Christian Scientist, and the newer "non-demoninational" churches all count. It's really hard to characterize them all beyond the very basics.

There are certainly people who call themselves Christian, and reject science. There are also people who call themselves American, and reject religion. It's no more accurate to say Christians are opposed to science than to say Americans are opposed to religion.