March 9, 2006

The Fabric of the Cosmos was given to me by one of the many ex-physicists at work. I’d previously read Greene’s The Elegant Universe, and found it interesting but perhaps a bit long: I suspect that attempting to get a whole book out of explaining string theory without using mathematics might have been a bit ambitious.

The Fabric of the Cosmos is lovely to read. Greene takes a couple of questions as his theme: Are space and time a “thing”, or merely about the relationship between things? Where does our perception of an “arrow of time” come from? He begins with Newton and Leibnitz and works forward through Special Relativity, General Relativity, quantum mechanics and modern attempts to unite the latter two, introducing concepts like entropy and inflation theory along the way.

Greene has a gift of explaining technical concepts clearly. Sometimes he chooses an appropriate analogy, but more often it’s a straight explanation written with the clarity of someone who has a deep understanding of the subject themselves but still retains some idea of how hard it was to learn it. I learned some things which I’m pretty sure were new to me rather than things I knew and then forgot (for example, I don’t think anyone ever explained that a flat, Ω=1, universe can either be spatially infinite or have toroidal topology).

Personal digression into “when I was at Cambridge” nonsense: My own, somewhat limited, success as a physicist relied mostly on my ability to do really evil calculus: given some likely looking equations, I’d just dive in and emerge, gasping, with the answer. My supervisors were always writing remarks like “more words, please!” on my work (oddly enough, these days my code is pretty well commented). Nevertheless, I did OK on the Cambridge course, which was basically about testing your ability to do this stuff really fast in an exam and to think on your feet in supervisions. This was fine until the later years when they started to ask questions which tested actual understanding, and I hit my head on stuff like the Feynman path integral like Asimov hitting calculus and realised I couldn’t just do the maths anymore. I don’t really have a physicist’s intuition, but in my defence, I mostly didn’t have people like Greene as lecturers (with some notable exceptions), but rather the “101 Great Moments in Calculus” sort. They almost certainly had the deep understanding, but they weren’t so good with the the words either. I’ve no idea whether it’s still like this, and it’s probably my fault for not reading around the subject in the stupidly long vacations that Cambridge undergraduates get. Nevertheless, there should be more educators like Greene.

Greene also conveys something of the wonder and strangeness of the universe. Space is big, as someone once said, but it’s also odd. Its constituents behave in ways which are so different from everyday objects that it’s hard to believe these objects are built up of such stuff.

I was reminded again that the majority of the universe is so unlike Earth that it beggars belief that some people could believe it was all put here for our benefit (“He also made the stars”, apparently) or that an entity who could create the whole thing would be concerned with the inhabitants of an insignificant little blue-green planet.

Rant over. Green writes engagingly. I’d recommend the book to people who want to know the secrets of the universe.

Continuing my theme, there was story a little while back about a quantum computer that can do calculations without actually running. I was annoyed that nobody in the popular science press seemed to get further with an explanation than “ooh! quantum! straaange!”. Luckily Sean Carroll rides to the rescue, with an explanation involving puppies and lettuce. Great stuff.