It’s coming up for a century since Albert Einstein explained the entire ‘classical’ universe. Neatly, and in ways that have been tested every which way, without being disproven.
Albert Einstein lecturing in 1921 – after he’d published both the Special and General Theories of Relativity. Public domain, via Wikimedia Commons.
He never did manage to reconcile quantum physics with his macro-level rules, but there’s no question that Einstein got it right about the big stuff. General Relativity, remember, is actually a theory of gravity. And everything about it has been checked out. Repeatedly.
Still, there are points where his rules break down. I mean, literally. Points. As in mathematical points. Places that have no diameter.
They’re called ‘singularities’, and they’re inside every black hole. We can’t see them, because the singularity is masked by the event horizon. This is the point where the escape velocity of the object exceeds lightspeed – meaning light doesn’t escape, hence the term ‘black hole’.
Einstein predicted that too. And the fact that the singularity was inside an event horizon was the proverbial Good Thing because, according to theory, all the physics we know and love break down at the singularity. There has been speculation they might act as a gate (‘Einstein-Rosen Bridges’). But to Einstein and most of those who came after, it was academic, because nothing could escape the event horizon.
Enter Stephen Hawking. In 1974 he argued that black holes MUST emit particles under quantum rules. Imagine a particle just inside the event horizon. Thanks to quantum uncertainty, it is both on one side and the other. When the wave function collapses, there is a chance that the black hole has radiated a particle.
Black holes, in short, evaporate thanks to quantum effects. It takes a while for stellar-mass holes (and they’d gain more mass than they lost, via matter spiralling into them). But the particle-size black holes possible in the CERN supercollider have a lifespan of a millionth of a second. Or less.
Hawking radiation, however, doesn’t resolve the other paradox of black holes – which is that they cause loss of ‘information’. It vanishes into an event horizon and is gone, violating energy conservation rules and the conservation of information in the physics sense – unitarianism. Various explanations have been offered, none of them entirely satisfactory because the black hole exists at the intersection between the two incompatible theories – General Relativity and quantum mechanics.
This week, Hawking suggested that the best answer to the paradox is to assume that an event horizon doesn’t exist. It merely appears to; in fact the information is re-radiated, chaotically.
Artists impression of a GRB (which is extreme, but not weird extreme). Zhang Whoosley, NASA, public domain, via Wikipedia.
All this is weird. But wait, if you extend the theoretical thinking it can get way weirder.
According to Hawking’s early work, the universe – during the early milliseconds of the Big Bang – might have created a ‘naked’ singularity. Later he revised that idea and said it hadn’t.
But imagine if it had. Naked. A singularity unprotected by an event horizon. Anything could happen. In all probability it would emit particles. But it might emit a monkey with a typewriter, tapping out King Lear. Or Sauron. Or The Heart of Gold. Or something so wild and crazy we can’t comprehend it. The laws of physics – which include probability and the order of events – don’t exist in a singularity.
Feel like you’re trapped inside Dr Who?
Could it happen? In theory, the singularity would become a torus outside the event horizon on a black hole that spun fast enough. And there is a theory – ‘loop quantum gravity’ – which postulates that naked singularities could exist anyway. The theory’s unproven.
And as of this week there’s Hawking’s notion of no event horizon anyhow – turning ‘black holes’ into…well, probably rather more than fifty shades of grey.
Wild? Sure. Weird? Absolutely. But that’s extreme physics for you.
Pass me a bunch of fermions. I’m famished.
Copyright © Matthew Wright 2014
Coming up: More writing tips, science geekery, humour and more. Including the awaited lightspeed-with-custard experiment. Watch this space.