Quantum mechanics is a knotty tangle of mathematical, practical, and philosophical threads, itching to be unravelled.
The Quantum Universe (And Why Anything That Can Happen, Does)Publisher: Da Capo
Length: 256 pages
Authors: Brian Cox and Jeff Forshaw
Publication date: 2012-02
This could be a momentous year for physics. Near Geneva, Switzerland, in a 17–mile long circular tunnel hundreds of feet underground, scientists are accelerating streams of protons to incredible speeds and smashing them against each other. The accelerator, known as the Large Hadron Collider, will soon help scientists prove whether the Higgs boson, a hypothetical elementary particle, really exists or not. More dramatically, it could also find evidence for the hypothesized particles of supersymmetry, or for hidden dimensions, or for something even weirder.
Indeed, this is a propitious time for curious minds to learn more about physics, and in particular about quantum mechanics, its most puzzling and least-understood branch. The Quantum Universe, authored by professors Jeff Forshaw and Brian Cox, feels like a good place to start, especially since Cox has recently been credited with re-energizing popular science in the UK with his TV appearances and rock-star looks.
However, though the book aims to give the so-called 'average person' an accessible account, average persons not already math- and physics-savvy will find it hard work. Its central metaphor, borrowed from the late Nobel-winning physicist Richard Feynman, likens the mathematical probability of finding a particle in a particular location to a clock. The clock travels, gets larger or smaller, its hand whizzes round, it meets other clocks and then (with the help of a little trigonometry) combines with them, until it all starts to feel like a Salvador Dali landscape of exhausted and melting timepieces -- much like one’s own brain when trying to comprehend such things.
On the other hand, novices who bravely stick with this book will be rewarded with many stranger-than-fiction facts about matter and anti-matter, standing waves, the Uncertainty Principle, neutrinos, dying stars, and more, in addition to learning about the embarrassing deficiencies of today’s education system.
One key fact to take away is that quantum mechanics is not just about strange and exotic stuff, but also about the everyday. For example, thanks to the quantum-mechanical properties of semiconducting materials (silicon, mostly) the world manufactures 10,000,000,000,000,000,000 transistors per year, around one billion of which are sitting in your cell phone.
Still, the most mind-boggling aspect of quantum mechanics is neither the mathematical nor the practical, but the so-called 'philosophical' implications of the theory. For instance, when scientists talk about finding a particle in a location, is that the same as saying the particle is in that location? What does it mean for something to be somewhere? Doesn’t quantum mechanics tell us that particles aren’t actually localized in the ordinary sense of the word, but are fuzzy, smeared-out entities, linked to each other and, in a sense, to the whole universe? Isn’t all of reality somehow fuzzy yet quantized, interconnected yet also discontinuous?
Such questions were being discussed by philosophers long before quantum theory came about. Democritus, for example, believed that matter was divided into small parts that were themselves indivisible (he called them 'atoms'); Descartes thought of matter as being smooth and extended (he called it 'res extensa'); and Engels married both perspectives when he wrote that 'there is no leap in nature, precisely because nature is composed entirely of leaps'.
In quantum physics, the most famous illustration of this kind of conundrum is the double-slit experiment, discussed in chapter 2 of this book. When electrons are shot through two slits against a screen, they create a wave-like pattern of dots -- even if one electron is shot today, and the next one tomorrow. So each single electron is in one sense a point-like particle, while in some other sense being not a single particle, but a wave.
Cox and Forshaw choose mostly to steer clear of the mystery, telling us that the 'sole job of the electron wave is to allow us to compute the odds that the electron hits the screen at some particular place', and not to 'worry about what the electron wave actually “is”' (30). They seem to find the so-called "many worlds" solution appealing, but they resist being drawn into a discussion. With this they echo Newton’s famous saying, 'hypotheses non fingo' ('I contrive no hypotheses') or, in today’s cruder version, 'shut up and calculate'. The danger, as they apparently see it, is that exploring the riddles of the physical world, rather than the comforting certainties of the numbers, might open the door to 'all sorts of holistic drivel' (140).
To be sure, there’s plenty of quantum drivel and quackery around (consider, if you can stomach it, Deepak Chopra’s 'quantum healing'), and scientists, being human, aren’t completely immune to it -- hence the attraction of the 'shut up and calculate' approach. Nevertheless, not all investigation of the broader significance of quantum mechanics is quackery; not all holistic thinking is drivel; and some is in fact necessary. If quantum physics studies an entangled and fundamental reality, then it must itself be connected, however loosely, to other forms of human reasoning -- especially to philosophy, itself pretty fundamental.
In any case, avoiding the tricky business of interpretation doesn’t eliminate the riddles, but only makes them more mysterious. What, for example, are we to think about the statement that a ball flying through the air '"knows" which path to choose because it actually, secretly, explores every possible path'? (53); or about the assertion that some aspects of Nature are 'governed by the laws chance'? (7); or about the view that science is 'the investigation of the real, and if the real seems surreal then so be it'? (213) Such pronouncements open the door to quackery and mysticism much wider than the authors want or realize.
Contrasted with their foot-dragging on issues of interpretation, Cox and Forshaw are too quick to celebrate 'the reduction of the tremendous complexity in the world, human beings included, to a description of the behaviours of just a handful of tiny subatomic particles and the four forces that act between them' (3-4). Sorry, but you can’t explain the mating habits of squirrels, or the Thirty Year War, through quantum mechanics -- no matter how good your mathematics. Just like it happens with matter, there are critical discontinuities in human knowledge, as well as crucial connections.
The bombarded and baffled 'average person' need not be put off by any of this. Out of curiosity mixed with frustration, The Quantum Universe should spur us to find out more. Luckily, quantum mechanics regularly produces truckloads of reading and watching material for popular consumption. In addition, we’re fortunate this year to witness live experiments that could forever change our picture of the universe. The end result? There’s no end result. As our knowledge expands and deepens, reality grows gradually less mind-boggling, yet more and more astounding.