Black holes, event horizons and spooky action at a distance
When language just shrugs its shoulders and sighs…
For reasons which I can’t quite fathom, but am happy to be carried along by, I have been reading a lot of popular science books on physics recently. They have to be popular science books, because I only have rudimentary maths (I was thrown out of the maths class when I was thirteen, but that’s another story…). So when I say, as above, that ‘language just shrugs its shoulders’ I mean words, not the language of mathematics. That the mathematics works I take on trust. Even given all that, though, I remain fascinated by the history of science, by how discoveries are made, and what they mean for us ordinary mortals.
One of the most accomplished, witty, and extraordinarily lucid of these popular science books has been Paul Sen’s Einstein’s Fridge: The Science of Ice, Fire and the Universe, which covers the unfolding story of the theory of thermodynamics (and yes, by the by, Einstein did actually invent a fridge).
One of the peculiar things about the world as described by scientists is that there are ‘laws’ - strict rules of behaviour which (unlike our human laws) cannot be contravened. And that is the case with the catchily named Laws of Thermodynamics. Because of the way in which these laws were discovered, they started out as two - 1. The energy of the universe is constant, and 2. The entropy of the universe tends to increase. But then, over the course of the twentieth century, two more laws were added - one at the beginning of the sequence (of course) and one at the end, lying like slices of new bread around the Thermodynamic sandwich. The one at the beginning of the sequence is called the Zeroth Law (again, of course it is) and the one at the end is the Third.
These four elegantly phrased statements (though the Zeroth and the Third sound slightly clunkier to the untutored ear) describe what appear to be invariable and incontrovertible ways in which heat/energy behaves in the world as we know it - or should that be in the world that we know? But more of that in a moment.
One of the charming things that becomes apparent while dallying along the highways and byways of the history of science is the way in which scientists, as they make new discoveries which they then have to name, take the opportunity to pay tribute to places and people they wish to honour. Thus polonium is named after Marie Curie’s homeland of Poland, and the boson was so called by Paul Dirac in commemoration of Indian physicist Satyendra Nath Bose. Physics is thus scattered with remembrances, which, despite the fiendishly difficult mathematics, makes it at heart a very human discipline.
Nor are physicists without a sense of humour - some elementary bosons are called gluons (glue-ons) because they give rise to forces between other particles. And that brings me round to the title of this piece. As physicists step further forward into the post-Einsteinian world of quantum physics, they are finding stranger and stranger things which baffle the mind, if not the mathematics, and challenge nomenclature in ways that are strangely reassuring.
Take, for instance, the German physicist and astronomer Karl Schwarzschild, who, in 1916, published a paper on Einstein’s General Theory of Relativity, which had just seen the light of day the year before. That Schwarzschild was serving in the German army and fighting on the Eastern Front at the time he researched, wrote and published this paper is just one of the mind-bending things about this story. Even more mind-bending, though, is what Schwarzschild came up with. In Paul Sen’s words:
This work made the disturbing prediction that if a massive object such as a star was compressed to a sufficiently high density, it would curve space and time to such an extent that something bizarre would happen. Space and time would become infinitely curved. This supermassive star would create a ‘singularity’, which is a fancy way of saying that the mathematics of general relativity fail and can make no description of what might be going on.
A ‘singularity’ is a wonderfully understated way of describing the discovery of an absolutely What The Fuck entity - and of course, they didn’t stay called singularities for long. They are now more popularly called by the resonantly sinister name of black holes, a name first ascribed to them by US physicist John Wheeler - of whom more in a moment.
At first it was thought that, while the mathematics might work, there couldn’t actually be black holes. That would be altogether too scary strange. But, oh yes, it transpires there actually are. There are places where space and time swirl round like water down a plughole at such a rate that everything is pulled in, and nothing, or almost nothing, can escape. Not even light. The edges of these scarily strange entities are called ‘event horizons’ because, well, that is the horizon beyond which events stop as far as we are concerned. Not that they quite stop, apparently. Because, it seems, there is still entropy, even in a black hole. In fact, as John Wheeler’s doctoral student Jacob Bekenstein went on to prove, in a desperate attempt to demonstrate that the Second Law of Thermodynamics holds good, even in relation to a black hole, so that Whenever the entropy of a black hole increases, so does the area of its event horizon. So yes, black holes are scarily strange, but the laws of thermodynamics which govern our universe still hold true.
However, just when you thought it was safe to cosy down into the world, there is, it seems, something even stranger than a black hole. Something which, for the time being at least, can, apparently, be observed, and even applied, but not explained - and that is quantum entanglement. This relates to the behaviour of some particles, where aspects of one particle of an entangled pair depend on aspects of the other particle, no matter how far apart they are or what lies between them. The effects of entanglement are faster than light - and light is supposed to be the fastest measurable thing in our universe. Quantum entanglement is what the absolute fuck strange and inexplicable, and best described by Einstein’s phrase, ‘spooky action at a distance.’ Which is one hell of an understatement.
The world is an utterly extraordinary place, and often beyond the bounds of our language, so we reach for the familiar and the identifiable to make it manageable. Do we live in a multiverse, with different universes branching off at every moment? Are we in fact trapped in a black hole, so that the expanding universe which we observe is simply an expression of the expanding event horizon beyond which we cannot see? Who knows? Perhaps our children will find out. In the meantime, it’s kind of fun.