The Order of Time - Carlo Rovelli ***

There's good news and bad news. The good news is that The Order of Time does what A Brief History of Time seemed to promise but didn't cover: it attempts to explore what time itself is. The bad news is that Carlo Rovelli does this in such a flowery and hand-waving fashion that, though the reader may get a brief feeling that they understand what he's writing about, any understanding rapidly disappears like the scent of a passing flower (the style is catching).

It doesn't help either that the book is in translation so some scientific terms are mangled, or that Rovelli has a habit of self-contradiction. Time and again (pun intended) he tells us time doesn't exist, then makes use of it. For example, at one point within a page of telling us of time's absence Rovelli writes of events that have duration and a 'when' - both meaningless terms without time. At one point he speaks of a world without time, elsewhere he says 'Time and space are real phenomena.' The difficulty I think Rovelli faces is that he uses the common physicist's approach of talking of a model as if it were reality. 

The wofflyness often gets in the way of understanding. For example, when talking about the second law of thermodynamics and entropy, he claims (I think - it's difficult to tell exactly what he is claiming) that the only reason we perceive the arrow of time from the increase of entropy is the way we label things. The implication is that, for example, the atoms in your body are no more ordered than the atoms in a scrambled mess - it's just that it's easier to see the order in your body because on the scale of atoms everything is blurred, but if we could see every atom exactly, whatever configuration they would be in would itself be unique. It sounds impressive, but skips over the way that fundamental quantum particles are indistinguishable. The arrangement of the cloud of atoms is only unique if you can tell one hydrogen atom (say) from another.

This is rather a shame, as Rovelli covers a considerable amount in what is a distinctly short book (though, thankfully, you get more for your money than in Seven Brief Lessons). Amongst other things, Rovelli passingly covers the special and general theories of relativity, thermodynamics and, of course, loop quantum gravity. And it's particularly frustrating because his attempt to put across the idea that it’s better to model reality in terms of events rather than things is a very powerful one which isn't often seen in popular science - but the message could easily be lost in the confusion. You come away with very little information - far more that rapidly disappearing odour.

I've no doubt this book should do well for those who are impressed that a physicist can refer to Proust. But I like a popular science book with significantly more meat in it, rather than vague impressions.

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Review by Brian Clegg