Sunday, June 09, 2013

About time

Here’s a book review of mine that appears in today’s Observer.


Time Reborn: From the Crisis of Physics of the Future of the Universe
Lee Smolin
Penguin, 2013
ISBN 978-1-846-14299-4
319 pages, £20.00

Farewell to Reality: How Fairytale Physics Betrays the Search for Scientific Truth
Jim Baggott
Constable, 2013
ISBN 978-1-78033-492-9
338 pages, £12.99

At an inter-disciplinary gathering of academics discussing the concept of time, I once heard a scientist tell the assembled humanities scholars that physics can now replace all their woolly notions of time with one that is unique, precise and true. Such scientism is rightly undermined by theoretical physicist Lee Smolin in Time Reborn, which shows that the scientific view of time is up for grabs more than ever before. The source of the disagreement could hardly be more fundamental: is time real or illusory? Until recently physics has drifted toward the latter view, but Smolin insists that many of the deepest puzzles about the universe might be solved by realigning physics with our everyday intuition that the passage of time is very real indeed.

Clocks tick; seasons change; we get older. How could science have ever asserted this is all an illusion? It begins, Smolin says, with the idea that nature is governed by eternal laws, such as Newton’s law of gravity: governing principles that stand outside of time. The dream of a ‘theory of everything’, which might explain all of history from the instant of the Big Bang, assumes a law that preceded time itself. And by making the clock’s tick relative – what happens simultaneously for one observer might seem sequential to another – Einstein’s theory of special relativity not only destroyed any notion of absolute time but made time equivalent to a dimension in space: the future is already out there waiting for us, we just can’t see it until we get there.

This view is a logical and metaphysical dead end, says Smolin. Even if there was a theory of everything (which looks unlikely), we’d be left asking “why this theory?” Or equivalently, why this universe, and not one of the infinite others that seem possible? Most of all, why one in which life can exist? A favourite trick of cosmologists is to beg the question by arguing that it only gets asked in universes where life is possible – the so-called anthropic principle. Smolin will have none of that. He argues that because life-supporting universes are generally also ones in which black holes can form, and because black holes can spawn new universes, a form of cosmic natural selection can make a succession of universes evolve towards ones like ours.

In this scenario, not only is time real, but the laws of physics must themselves change over time. So there’s constant novelty, and no future until it becomes the present. The possible price you pay is that then space, not time, becomes illusory. That might seem an empty bargain, but Smolin asserts that not only could it solve many problems in fundamental physics and cosmology but it is also more amenable to testing than current ‘timeless’ theories.

That attribute might endear Smolin’s speculative ideas to physicist-turned-writer Jim Baggott. Smolin caused grumbling among his colleagues with his 2006 assault on string theory, The Trouble With Physics. In Farewell to Reality, Baggott now castigates theoretical physicists for indulging a whole industry of “fairy-tale physics” – strings, supersymmetry, brane worlds, M-theory, the anthropic principle – that not only pile one unwarranted assumption after another but are beyond the reach of experimental tests for the foreseeable future. He recalls the acerbic comment attributed to Richard Feynman: “string theorists don’t make predictions, they make excuses”.

Baggott has a point, and he makes it well, although his target is as much the way this science is marketed as what it contains. But such criticisms need to be handled with care. Imaginative speculation is the wellspring of science, as Baggott’s hero Einstein demonstrated. In one of my favourite passages of Time Reborn, Smolin sits in a café and dreams up a truly outré idea (that fundamental particles follow a principle of precedent rather than timeless laws), and then sees where the idea takes him. In creative minds, such conjecture injects vitality into science. The basic problem – that the institutional, professional and social structures of science can inflate such dreams into entire faddish disciplines before asking if nature agrees with them – is one that Baggott doesn’t quite get to.

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