Black holes and revelations in the Mail

Edit: After a quick email conversation with the author, the article has now been rewritten (direct link). Although it still has a slightly cringeworthy headline, it no longer contains misunderstandings about the paper and is all in all pretty good! I’ve hidden the original post behind the cut.

A paper has recently been put up on the “e-print” site arXiv, “Structure and Mass Absorption of Hypothetical Terrestrial Black Holes” by A.P. VanDevender and J. Pace VanDevender. In a nutshell, the paper looks at things called Gravitational Equivalents of Atoms or GEAs: black holes that are as small as atoms and are orbited by particles trapped in the black hole’s gravity, in the same way that electrons orbit the nucleus of an atom. The Big Bang should have created microscopic black holes – the early universe was so small and hot that even tiny clumps of matter would be able to grow into black holes – but according to our current understanding of physics, the small ones should all have evaporated by now.

When black holes evaporate, they should release something called Hawking radiation. We’ve not managed to see Hawking radiation yet, which means one of two things: either there were not very many black holes created, or our theories about black holes evaporating are wrong.

The paper seems reasonable,* but then the whole point of the paper is to ask “what if?” What if our current understanding of gravity is completely wrong on small scales and micro black holes don’t evaporate after all? What would black holes look like then? What could we search for in the lab that might tell us how black hole evaporation works? Or, as the paper puts it in the very first paragraph:

Quantum evaporation of mini black holes has been so thoroughly studied theoretically that it has become a keystone to the development of theories of quantum gravity – even though quantum evaporation has not been verifi ed experimentally or observationally. Consequently, the need to test the theory has become urgent. So far, attempts to directly observe the x-ray signature of the final stages of evaporation have been unsuccessful. We examine a complementary approach – looking for small black holes whose existence would invalidate the quantum evaporation theory as it is currently formulated.

That sounds pretty clear: the paper is explicitly working out something that is impossible according to physics as we understand it, and proposing a way to search for these “impossible” objects, so if we do see one we know that our theories are wrong somewhere.

How does the Daily Mail cover it?

Revealed: How mini black holes pass through the Earth daily without causing any damage

Yep, in the Mail “These objects are impossible but may exist if physics is wrong” becomes “These objects exist and are here right now!”

The article is riddled with silly mistakes – for instance:

And unlike the larger black holes that swallow everything – even light – past a certain point, the mini black holes instead hold objects in an orbit.

Mini black holes swallow light just like large black holes – that’s the definition of a black hole after all – and there’s nothing odd about orbiting a black hole either. In fact, we’re probably orbiting one right now – Sagittaruis A*, the core of the galaxy. What is different about mini black holes is that – according to the paper – they are so small that matter orbiting them should be affected by quantum mechanics. In other words, instead of being able to travel around the black hole however it likes, the matter prefers to stick to a few fixed orbital “energy levels”. This means that matter tends to get stuck in these fixed orbits rather than falling straight into the black hole. The same principle also explains why electrons orbit the nucleus of the atom instead of just falling into the nucleus, which is why the VanDevenders compare black holes to atoms.

This is a bit of a tricky idea to explain, I admit – I’ve almost certainly made a bit of a mess of it there – but it’s better than the nonsensical claim that black holes can’t eat the earth because:

the mini black holes would pass so quickly through the planet that particles already bound in orbit around the GEA would be rapidly stripped from the mini black hole.

which seems to have come about by misunderstanding part of the paper (p. 5) which explains what it looks like when a GEA hits the Earth – namely, the outer material falls off, you get a sudden burst of energy, and the black hole continues on its course, naked. The black hole itself however would remain perfectly of capable of devouring things! The key things that would stop it eating the Earth are a) it would take trillions upon trillions of years to eat the Earth atom by atom and b) matter tends to orbit it instead of falling in to the core.

That said, I don’t want to lay into the journalist who wrote it, Lewis Bazley. According to his LinkedIn profile, he’s not a science journalist, he does news and showbiz. The bulk of the blame for this article rests with whichever editor thought it would be a good idea to make a showbiz journalist write about cutting edge theoretical physics.

* For the most part. It seems a bit odd to claim that GEAs might not evaporate because of quantum gravity, then later claim that GEAs are large enough that you don’t need to take quantum gravity into account when working out how they behave, but I should stress that quantum gravity is beyond my expertise. I should also point out that arXiv is not peer reviewed – it’s a place to upload papers before submitting them to a journal. That doesn’t make the paper wrong – most physics papers these days are put on arXiv – just that other experts in the field have yet to comment on and review the accuracy of the paper before it’s properly published.

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