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BLACK holes may be filled to the brim with giant strings and vibrating membranes. The idea contradicts the conventional view of black holes, which says that all the matter inside is crammed into an infinitely dense point. And by providing a way for black holes to send out information about their contents, it could resolve a profound paradox in physics.

Samir Mathur and his colleagues at Ohio State University in Columbus were investigating a puzzle called the black-hole information paradox. The gist is that the theory of quantum mechanics says information must be preserved – it cannot be created or destroyed – but black holes seem to be the ultimate cosmic shredders, destroying all information that passes into them.

In the 1970s, Stephen Hawking showed that any energy falling into a black hole is eventually spat out again as radiation. He found that this radiation carries no record of what went into the hole. That is because Hawking radiation is generated at the “event horizon”, the boundary of the black hole, while all the stuff that falls in is supposed to be crushed to a point, called a singularity, at the centre of the hole (see Graphic). There is no way for the singularity to be in contact with the event horizon, so the information within it is lost. Hawking famously bet a set of encyclopedias that black holes would never be shown to hold any information about what is inside.

Now strings could resolve the paradox. According to string theory, subatomic particles are made of tiny strings and membranes. These are normally incredibly small – about 10⁻³⁵ metres long. In the crushing conditions of a black hole, however, they would lose their independence and get tangled together. Mathur calculated the effect of this, and found that it would make the usually taut strings loose and stretchy. In fact, they could stretch to become as large as the black hole itself (Nuclear Physics B, vol 680, p 415).

In most ways, this “fuzzball”, as Mathur calls it, behaves just like a classical black hole. Though there is no sharp event horizon, even light could not escape if it got too close. “The tangle of strings absorbs anything that falls on it,” Mathur told 91av. But there is a crucial difference. Hawking radiation would be emitted by the stringy surface of the fuzzball, so it could carry information about what originally fell in.

Mathur has not yet convinced everyone. Cumrun Vafa of Harvard University points out that the calculations only work for a black hole with the maximum possible electric charge. But Mathur is confident that when he does the more difficult general calculation, the result will stand.

If so, it could also change ideas about the early universe. It might mean we no longer need inflation theory – the idea that space exploded outwards incredibly fast, moments after the big bang. Inflation is supposed to explain why the temperature of the whole universe is so uniform. But Mathur thinks that just after the big bang, strings and membranes might have been packed together tightly enough to go soft and stretch out, just as in a black hole. This web of connections stretching across the early universe could have evened out its temperature without inflation. It might even be that the universe did not emerge from a singularity at all, but from a fuzzball.

It will be hard to prove whether he is right. Hawking radiation is incredibly weak, far beyond our current powers of observation. The best test of Mathur’s idea in the short term may be to work through the maths and see whether it really does make quantum mechanics work for black holes.