Tuesday, February 06, 2007

Leaning on a weak reed

Many people don’t believe the Bible because the Bible is soooo unscientific. Here’s a revealing window on the world of contemporary physics:

**********************************************

Stringing physics along
Review: February 2007

The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next_Lee Smolin_2006 Houghton Mifflin 416pp £25.00/$26.00hb

"Hypotheses non fingo," wrote Isaac Newton 300 years ago in the second edition of his Principia Mathematica. It has been variously translated as "I do not make hypotheses" or "I do not feign hypotheses". Instead, Newton established laws of nature such as his theory of universal gravitation – simple, economical equations of broad explanatory power able to account for diverse phenomena both known and yet to be observed. His natural philosophy became the dominant paradigm of the mechanical world-view and, more generally, what we call the scientific method.

In the last few decades, however, physical theory has drifted away from the professional norms advocated by Newton and other enlightenment philosophers. A vast outpouring of hypotheses has occurred under the umbrella of what is widely called string theory. But string theory is not really a "theory" at all – at least not in the strict sense that scientists generally use the term. It is instead a dense, weedy thicket of hypotheses and conjectures badly in need of pruning.

That pruning, however, can come only from observation and experiment, to which string theory (a phrase I will grudgingly continue using) is largely inaccessible. String theory was invented in the 1970s in the wake of the Standard Model of particle physics. Encouraged by the success of gauge theories of the strong, weak and electromagnetic forces, theorists tried to extend similar ideas to energy and distance scales that are orders of magnitude beyond what can be readily observed or measured. The normal, healthy intercourse between theory and experiment – which had led to the Standard Model – has broken down, and fundamental physics now finds itself in a state of crisis.

Lee Smolin, a theorist at the Perimeter Institute, Waterloo, Canada, has written a thoughtful, provocative book that squarely addresses these problems and advocates a solution in bold new approaches to physics. A principal aim of The Trouble with Physics is to re-engage theory with what actually occurs, or may occur, in the realm of observable phenomena. The book also addresses such core questions as: Why do quarks, leptons and gauge bosons have the diverse masses they possess? What are dark matter and dark energy? How can quantum mechanics and general relativity be combined into a single theory?

String theory originally shared most of these goals, but it got caught up in its own mathematical beauty. Like Narcissus, it increasingly began to contemplate its own reflection, to the exclusion of observable phenomena. To evade comparisons with dross reality, for instance, string theorists have invoked an unseen "metaverse" of parallel universes corresponding to the "landscape" of 10500 possible solutions that might exist. The fact that our universe has spawned galaxies, stars, planets and intelligent life is explained away by the anthropic principle. Of late, a few leading theorists have even begun to suggest a radical new philosophy of science, rejecting Newton, in which hypotheses no longer require observable evidence in order to be accepted as valid theories. To a hardened experimenter like me, this is blasphemy.

So it is refreshing to hear from a theorist – one who was deeply involved with string theory and championed it in his previous book, Three Roads to Quantum Gravity – that all is not well in this closeted realm. Smolin argues from the outset that viable hypotheses must lead to observable consequences by which they can be tested and judged. That is, they have to be falsifiable. Newton's theory of gravitation, for example, could later account for the orbit of Halley's Comet – not just those of the Moon and planets for which it was originally formulated. But string theory by its very nature does not allow for such probing, according to Smolin, and therefore it must be considered as an unprovable conjecture.

http://physicsweb.org/articles/review/20/2/1/1

5 comments:

  1. To add to the article Steve cites, in an interview one year before he died, physicist Richard Feynman similarly weighed in on string theory (excerpted from Not Even Wrong: The Failure of String Theory and the Search for Unity in the Physical Law by Peter Woit):

    "[Feynman:] Now I know that other old men have been very foolish in saying things like this, and, therefore, I would be very foolish to say this is nonsense. I am going to be very foolish, because I do feel strongly that this is nonsense! I can't help it, even though I know the danger in such a point of view. So perhaps I could entertain future historians by saying I think all this superstring stuff is crazy and is in the wrong direction.

    [Interviewer:] What is it you don't like about it?

    [Feynman:] I don't like that they're not calculating anything. I don't like that they don't check their ideas. I don't like that for anything that disagrees with an experiment, they cook up an explanation -- a fix-up to say, 'Well, it still might be true.' For example, the theory requires ten dimensions. Well, maybe there's a way of wrapping up six of the dimensions. Yes, that's possible mathematically, but why not seven? When they write their equation, the equation should decide how many of these things get wrapped up, not the desire to agree with experiment. In other words, there's no reason whatsoever in superstring theory that it isn't eight of the ten dimensions that get wrapped up and that the result is only two dimensions, which would be completely in disagreement with experience. So the fact that it might disagree with experience is very tenuous, it doesn't produce anything; it has to be excused most of the time. It doesn't look right."

    Feynman apparently also quipped, "String theorists don't make predictions, they make excuses."

    ReplyDelete
  2. This comment has been removed by the author.

    ReplyDelete
  3. Unfortunately, I've not read it.

    But why read when you can watch it, since the TV series is available for free online? (I'm totally kidding, though. Obviously it'd be best to do both.)

    ReplyDelete
  4. Jiminy Cricket2/07/2007 9:17 AM

    Bernie said:
    "Has anyone here read The Elegant Universe?"

    Yes.

    "If so, thoughts?"

    Supersymmetry and the graviton/quantum gravity are the two missing pieces to move us towards a grand unified theory, be it string or otherwise. Once that happens, bye-bye to the singularity and hello to a new cosmology.

    ReplyDelete
  5. Berny said:
    Has anyone here read The Elegant Universe?

    If so, thoughts?

    ***************

    I've read it. It's already rather dated.

    ReplyDelete