Monday, April 29, 2013

String Theory: Did God Have Any Choice?

I am reminded of this question by the opening chapter of a book I have just started reading: The Trouble With Physics: The Rise of String Theory, The Fall of a Science, and What Comes Next by Lee Smolin.  Smolin, who is skeptical of string theory, has justified criticisms about the extent to which string theory has monopolized particle physics and the over-exuberance of some of the proponents of the theory's proponents.  He does not quote them asking, "Did God have any choice?" but it actually has been suggested by some enthusiasts that no, God did not have any choice; no other laws for the universe were possible.

Ambrogio de Predis 007

You don't have to be either a physicist or a theologian to see that this is poppycock.  We can imagine all kinds of laws that might govern the universe.  We do this not only in scientific conjecture, but also whenever we write books of fantasy or science fiction.

Not only does such a suggestion both border on blasphemy and also contradict the everyday experience of telling, hearing, and reading stories, it perpetuates the idea that modern physics advances very much like it did in ancient Greece:  scientists sit around and tell stories, and whoever tells the best story "wins".  This completely obscures the fact that physics is an intrinsically experimental science.  The literature is full of elegant theories that nevertheless are contradicted by experiment, and Mother Nature always gets the last word.  Of course, the most damage was done by Albert Einstein, who really did think his theory was so beautiful that it must be true; so far, Mother Nature seems to agree.

In reality, the situation is not that bad.  The best book I have finished on string theory and why it is appealing is Out of This World: Colliding Universes, Branes, Strings, and Other Wild Ideas of Modern Physics by Stephen Webb.  Webb's book makes it clear that the "inevitability" of string theory is a conjecture (not proved) that is constrained by the known symmetries of the gravitational, strong nuclear, and electroweak forces, together with a dash of aesthetic beauty. 

To illustrate what this means, imagine I am trying to understand how many finger are on my right hand.

  1. I perform one experiment and find that there are fewer than 6 fingers on that hand.  
  2. I perform another experiment and find  that my right hand has more than 4 fingers.  
  3. Finally, I declare that the laws of nature are beautiful, and a beautiful law would be that the number of fingers on a hand is an integer.  
There is only one solution left:  I have 5 fingers on my right hand.  I might make a brash statement that "God had no choice" but to give me 5 finger on that hand, given conditions 1, 2, and 3.  But of course, the experiment does not really constrain God's choice; God's choice constrained the experiment.  I could easily have been born with more or fewer than 5 fingers on my hand, as was the case with some of my acquaintances.  As for the requirement of an integer number of fingers, some people lose part of a finger, and in any case one might argue that the thumb does not count as a whole finger.

Why then is such a ridiculous claim made about string theory?  Either because the speaker does not really understand what he's talking about, or because he wants to make a shocking statement that makes him seem more important than he really is.

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