Reviewed by Ian Lipke
Jim Weatherall has taken possibly the most arid word in use on the planet and written a book that is scientifically precise, rich in history and cultural endeavour, and at all times, engaging. That word is nothing. Take all your molecules, atoms, electrons, quarks and gluons – such old hat science is all about something. Weatherall seeks a challenge and gives us Void: the Strange Physics of Nothing. This is a little book of big ideas written in lively, stimulating prose.
Weatherall builds on the philosophies of the past and takes us rapidly through the centuries to the cutting edge science of today. He describes Newtonian mechanics, Maxwell’s electromagnetism, relativity theory and quantum field theory, and presents ideas about what the world would be like if there were nothing around; he then describes what nothing might mean.
Perhaps you’re thinking by now that Weatherall is not for you, that science is just too unexciting. I can assure you that Weatherall’s language and the decisions he makes to present his ideas combine to make an engaging and colourful treatise. The book includes sophisticated argument but the explanations are clear and the arguments cogent. This is more than a book, it is a Hollywood extravaganza in the restrained garb of a dignified British thriller. It leaves its readers clamouring for more as the beauty of fact overwhelms and satisfies at humanity’s deepest levels.
In Newtonian physics a universe with nothing is thought of in terms of an infinite container into which stuff could be placed or removed without affecting the structure of space itself. This is empty space and time. But space-time has a structure that is, geometrically speaking, fixed and immutable. Questions invoking general relativity about a world with no matter present can be shown to possess a space-time geometry that is rich and dynamic.
Then Maxwell’s ideas on electromagnetism led the way to electromagnetic field theory and what it would mean for a region of the universe to be empty. If electromagnetic radiation e.g. light is all that is present in the region, then it is not empty at all. Since scientists measure how much of the electromagnetic field is present in a region by a quantity known as field strength, knowing what field strength is present is a way of describing how the electromagnetic field is configured.
Determining there is “nothing” in a region of space and time means that “nothing is not the absence of stuff; instead it is just one possible configuration of stuff” (65). Here is the first subtle difference between what scientists and the man in the street mean by nothing.
Einstein’s theory of general relativity was a massive blow to conventional thought. Curvature of space-time replaces what we used to think of as gravitational force. Objects are not accelerating towards each other, they are not accelerating at all; “they are both moving along the straightest lines they can, in a space-time in which no lines are truly straight” (71). The geometry of space-time is partially determined by the matter in the universe, and partly determined by the geometry of the rest of space-time.
“No stuff” does not guarantee “no curvature”. Hence in general relativity thought, “empty” space puts the spotlight directly on “empty”.
Weatherall now mentions another attribute of the “nothing-space” idea. Maxwell’s equations describe electromagnetic radiation – waves that travel from one place to another and oscillate. Einstein realised that general relativity permitted something very similar. It allowed gravitational waves, oscillations in the geometry of space-time i.e. when a gravitational wave passes through some region of space-time,.then the ‘straightest’ lines in that region will oscillate. Further, since “gravitational waves are possible even in empty universes, Einstein realised that they are not themselves a kind of stuff, in the same sense that a black hole is not a kind of stuff. Gravitational waves are also possible in universes where there is matter – but, in those cases, too, they don’t count as being matter themselves” (79).
A gravitational wave can produce energy, perhaps as light or heat or motion i.e. stuff in the ordinary sense. In other words, general relativity tells us that it is possible to make something out of nothing. You might well ask why there are black holes rather than nothing. It turns out black holes are just a variant of nothingness.
This is getting more and more weird. Who has seen a gravitational wave anyway? Where’s the evidence? Funny you should ask. Check what Weatherall relates concerning LIGO and September 14, 2015, when a signal was recorded and found to be two black holes colliding more than a billion years ago. This is powerful evidence for general relativity – “including the rich, dynamic structure of empty space-time the theory describes” (85).
All theories we’ve dealt with so far have in common a state of affairs – a configuration of physical objects at an instant or over time – by imagining bodies, with more or less defined boundaries, located somewhere in space (and time). This is one interpretation of ‘state’.
However, a quantum state encodes probabilities about what you might find if you were to try to measure some physical quantity. Particle-like behaviour is characteristic of quantum fields, but “particle” no longer has its Newtonian label; in quantum physics it describes a particular configuration of a quantum field. This distinction is very important.
In a quantum state we encounter some really strange ideas. The idea of a world of particles strongly suggests that there are stretches of empty space between particles.
Quantum field theory allows no such thing.
In a quantum state you would expect to find any number of particles. But there are cases where it is certain that there is exactly one particle or two and so on in the universe. In some cases it is absolutely certain that there are no particles in the universe. These are vacuum states – royalty in weirdness.
In quantum field theory, a vacuum state is just another state of matter – it just represents the field configuration where we minimise the particle-like phenomena. Other states are usually vacuum states plus particles. But vacuum states are even stranger than you might imagine. “Something” and “nothing” are not mutually exclusive.
A pleasure for a non-scientist to read, told in an exciting manner, captivating even science educators. A book about nothing that has a whole lot of something to say.
Void: the Strange Physics of Nothing
By James Owen Weatherall
Please use discount voucher code BCLUB17 at the checkout to apply the discount.