Thursday, 6 February 2014

Black Holes, Science And Religion

Fiery black hole debate creates cosmological Wild West - space - 05 February 2014 - New Scientist

As the above New Scientist article shows, one of those little frissons of excitement is spreading through the worlds of theoretical physics and cosmology, just as it did a couple of years ago when the folks at CERN thought they had discovered neutrinos which could travel faster than light. Now another fundamental idea is being questioned, reassessed and reconsidered.

This little flurry of excitement was caused a few days ago by Stephen Hawking's briefest of brief papers in which he cast doubt on the nature of black holes - cosmological objects which he was largely responsible for promoting in the first place. I commented on this at the time from an evolutionary perspective so I won't go over it again. The interesting thing now is how scientists react to new thinking which challenges established ideas and, so far as this blog is concerned, how this contrasts to the way religions react to challenges to their basic dogmas.

A clue, of course, is in the word 'dogma'. Only religions need dogma; science has theories, hypotheses and axioms, none of which are sacred and all of which are open to challenge.

What we will now see, and as the New Scientist article shows, is an exchange of ideas and a brief flourishing of new thinking as the old ideas are reassessed and the new ideas are tested and evaluated. No one will be offended because someone doesn't agree with them. No one will call for bans and proscription. No one will be expelled from this or that academy and deprived of their living for heresy. No one will be prevented from teaching in a university and there will be no campaign to have the wrong physics taught in schools because someone's political ambitions hang on the old ideas. And no-one will organise a cabal of offended 'eventhorizonists' to get the 'anti-eventhorizonists' banned from Twitter and have their blogs spammed with obscenities.

The reason religions need to do this, of course, is because they have no means of verifying their claims and no basis for testing and resolving conflict. There are simply no facts or evidence to look at and none of their claims are permitted to be falsifiable. Even officially contemplating the possibility of being wrong is unacceptable.

Now, what does science do when faced with questions which strike at the heart of basic theories?

It's not as though the underlying problem with black holes was unknown. It has been accepted that there is a fundamental paradox at the heart of modern physics because, quite simply Relativity and Quantum Mechanics don't quite join up, since Relativity and QM were formulated. Mostly, because Relativity deals with the very large, and Quantum Mechanics (QM) deals with the very small, physics can continue quite happily while paying lip-service to the paradox.

The 'storm' (maybe that should be 'fire-storm') is over the place where these two theories come into conflict in black holes where, according to Relativity, a large mass becomes concentrated into something very small, so at some point Relativity has to give way to QM as science seeks to explain what's happening. Something somewhere needs to cross a bridge (should that be a Planck?) but we've no real idea what this bridge could be or if it exists. If one or the other is slightly wrong, there might not even be a gap to bridge. The trouble is, they both look right and both have been confirmed time and again with observational and experimental evidence.

But, according to QM, there should be a firewall at this point and according to Relativity, there shouldn't be anything other than highly curved spacetime. They can't both be right.

It was Stephen Hawking's attempt to bridge that gap which has caused all the excitement because, in effect, he's suggested the point where Relativity and Quantum Mechanics come into conflict, the so-called event horizon where nothing which crosses it can ever come back out, may not exist. So, no firewall, no conflict, no event horizon, but no black holes either, at least as we thought we understood them.

But, this means information can escape a black hole - which QM says is impossible - the information paradox.

So how are the 'high-priests' (it's an analogy, creationists!) of physics reacting?

A star that collapses gravitationally can reach a further stage of its life, where quantum-gravitational pressure counteracts weight. The duration of this stage is very short in the star proper time, yielding a bounce, but extremely long seen from the outside, because of the huge gravitational time dilation. Since the onset of quantum-gravitational effects is governed by energy density --not by size-- the star can be much larger than planckian in this phase. The object emerging at the end of the Hawking evaporation of a black hole can then be larger than planckian by a factor (m/mP)n, where m is the mass fallen into the hole, mP is the Planck mass, and n is positive. The existence of these objects alleviates the black-hole information paradox. More interestingly, these objects could have astrophysical and cosmological interest: they produce a detectable signal, of quantum gravitational origin, around the 10−14cm wavelength.

The fuzzball construction resolves the black hole information paradox by making spacetime end just before the horizon is reached. But if there is no traditional horizon, then do we lose the elegant relations of black hole thermodynamics? Using an argument similar to modular invariance, we argue that the answer is no; the completeness of fuzzball states implies that the generic fuzzball indeed reproduces the thermal properties attributed to the traditional hole.

We propose that in quantum gravity one needs to impose a final state boundary condition at black hole singularities. This resolves the apparent contradiction between string theory and semiclassical arguments over whether black hole evaporation is unitary.

If information escapes from an evaporating black hole, then field modes just outside the horizon must be thermally entangled with distant Hawking radiation. But for an infalling observer to find empty space at the horizon, the same modes would have to be entangled with the black hole interior. Thus, unitarity appears to require a “firewall” at the horizon. Identifying the interior with the distant radiation promises to resolve the entanglement conflict and restore the vacuum. But the map must adjust for any interactions, or else the firewall will reappear if the Hawking radiation scatters off the cosmic microwave background. Such a map produces a "frozen vacuum," a phenomenon that is arguably worse than a firewall. An infalling observer is unable to excite the vacuum near the horizon. This allows the horizon to be locally detected and so violates the equivalence principle.

Did you spot the threats, the indignant offense, the quoting of dogma and reference to scripture in sacred texts, the chanting of sacred chants designed to shout down doubt, the calls for removal and excommunication or the demands for suppression?

Me neither.

In former times, religion's high priests would have been calling for bans, proscriptions, sackings, torture and execution of all these scientists for daring to express ideas which were not in full accord with their dogmas. When we stopped them doing that in Europe we started to make scientific progress and moved swiftly out of the Dark Ages.

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