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Brian Greene’s 1999 bestseller and Pulitzer Prize finalist The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory is more like two books in one. The first half to two-thirds is a highly accessible history of the two main branches of physics, the macro world perspective that culminated in Einstein’s discovery of general relativity, and the micro (I mean, really micro) perspective covered by quantum mechanics. The two theories could not be unified until the advent of string theory, which Greene lays out in still somewhat easy to follow language. The last third of the book, however, delves into deeper topics like the nature of spacetime or the hypothesis of the multiverse, and I found it increasingly hard to follow and, unfortunately, less compelling at the same time.
String theory – more properly called superstring theory, but like the old basketball team in Seattle, the theory has lost its “super” somewhere along the way – is the prevailing theoretical framework in modern physics about the true nature of matter and the four fundamental forces. Rather than particles comprising ever-smaller subparticles that function as zero-dimensional points, string theory holds that what we perceive as particles are differing vibrations and frequencies of one-dimensional “strings.” String theory allows physicists to reconcile Einstein’s theories of general and special relativity with the explanations of three of those four forces (strong, weak, and electromagnetic) provided by quantum mechanics, resulting in a theory of quantum gravity that posits that that fourth force is the result of a massless quantum particle called the ‘graviton.’ Gravitons have not been observed or experimentally confirmed, but other similar particles have been, and all would be the result of those vibrating strings, open or closed loops in one dimension that, under the framework, are the most basic, indivisible unit of all matter and energy (which are the same thing) in the universe.
Strings are far too small to be observed, or to ever even be observed – you can’t observe a string with a particle, like a photon, larger than the string itself – but physicists believe string theory is accurate because math. And that’s one of the biggest challenges for Greene or anyone else writing about the topic: the proof isn’t in experimental results or great discoveries, but in equations that are too complicated to present in any text aimed at the mass audience.
In fact, the equations underlying string theory require a universe of not four dimensions – the ones we see, three of space and one of time, which Einstein treated simply as four dimensions of one thing called spacetime – but ten or eleven. These “missing” dimensions are here, at every point in the universe, but are tightly curled up in six-dimensional forms called Calabi-Yau manifolds, as if they exist but the universe simply chose not to deploy them. They must be there, however, if string theory is true, because the calculations require them. This is near the part where I started to fall off the train, and it only became worse with Greene’s discussions of further alterations to string theory – such as higher-dimensional analogues to strings called 2-branes and 3-branes – or his descriptions of what rips or tears in spacetime might look like and how they might fix themselves so that we never notice such things. (Although I prefer to think that that’s where some of my lost items ended up.)
The great success of this book, however, is in getting the reader from high school physics up to the basics of string theory. If you’re not that familiar with relativity – itself a pretty confusing concept – this is the best concise explanation of the theories I’ve come across, as Greene uses simple phrasing and diagrams to explain general and special relativity in a single chapter. He follows that up with a chapter on quantum mechanics, hitting all the key names and points, and beginning to explain why general relativity, which explains gravity in a classical framework, cannot be directly coupled with quantum mechanics, which explains the other three forces in an entirely different framework. Building on those two chapters, Greene gives the most cogent explanation of superstrings, string theory, and even the idea of these six or seven unseen spatial dimensions that I’ve come across. We’re talking about objects smaller than particles that we’ve never seen, and the incredible idea that everything, matter, energy, light, whatever, is just open and closed one-dimensional entities the size of the Planck length, 1.6 * 10-35 meters long. To explain that in even moderately comprehensible terms is a small miracle, and Greene is up to the task.
This was a better read, for me at least, than George Musser’s book on quantum entanglement, Spooky Action at a Distance, which covers a different topic but ends up treading similar ground with its descriptions of spacetime and the new, awkwardly-named hypothesis “quantum graphity.” Quantum entanglement is the inexplicable but true phenomenon where two particles created together maintain some sort of connection or relationship where if the charge or spin on on of the particles is flipped, the charge or spin on the other will flip as well, even if the two particles are separated in distance. This appears to violate the law of physics that nothing, including information, can be transmitted faster than the speed of light. How do these particles “know” to flip? Musser’s description of the history of entanglement, including Einstein’s objection that provided the title for this book, is fine, but when he delves into new hypotheses of the fabric of spacetime, he just completely lost me. Quantum graphity reimagines spacetime as a random graph, rather than the smooth four-dimensional fabric of previous theories, where points (or “nodes”) in space are connected to each other in ways that defy traditional notions of distance. This would provide a mechanism for entanglement and also solve a question Greene addresses too, the horizon problem, where disparate areas of the universe that have not been in direct physical contact (under the standard model) since a tiny fraction of a second after the Big Bang currently have the same temperature. I didn’t think Musser explained quantum graphity well enough for the lay reader (me!), or gave enough of an understanding that this is all highly speculative, as opposed to the broader acceptance of something like string theory or absolute acceptance of quantum theory.
Next up: Back to fiction with Eowyn Ivey’s Pulitzer Prize finalist The Snow Child.