Prof Stephen Hawking: 'There are NO black holes' – they're GREY!

Brit uber-boffin Prof Stephen Hawking has quietly published a new paper proposing a radical rethink of the nature of black holes, which have been a major part of his life's work.

Hawking's paper [PDF], Information Preservation and Weather Forecasting for Black Holes has been submitted for peer review and attempts to apply both basic gravitational theory and quantum theory into a unified system.

In an interview with Nature today, Prof Hawking said that, under classical gravitational theory, there was no way for matter or energy to escape from the event horizon of a black hole: any astronaut venturing into one would be pulled out spaghetti style until he or she was crushed by the immense gravitational field.

That's using the classical gravitational theory. In 2012, physicist Joseph Polchinski of the Kavli Institute in California predicted that quantum effects would instead cause the event horizon to be a seething mass of high-energy particles – or a "firewall," as his team dubbed it – which would burn anything venturing inside to a crisp.

So, today, Prof Hawking's new idea seeks to reconcile these concepts. In his paper, he proposed there's actually no event horizon as such, just an "apparent horizon" made up of space-time that's fluctuating too wildly to have a fixed boundary as such – leading to a grey hole, if you will, instead.

"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," the professor wrote. "There are however apparent horizons which persist for a period of time. This suggests that black holes should be redefined as metastable bound states of the gravitational field." ®