Re: [asa] The Multiverse - Physics or Metaphysics?

Hi, David,

Thanks for the recommendation. I was reading various reviews of Smolin's
book on Amazon last night. One person gave the impression that it was "not
for the layman" and rather heavy on the physics. I notice it is also
controversial. One long and angry review even describes it as "a
post-modern attack on Science" !!

In view of the Smolin quote I gave (which is quoted in a review of "The
Trouble With Physics" in Physics World), I would have said it was more like
Smolin is trying to defend science against the invasion of non-science.

The full paragraph (from the physics world review by Houghton Mifflin) is:

If we accept string theory as valid while it evades observational tests, how
can we legitimately rebut arguments about the "intelligent design" of the
universe? The honest answer is that we cannot. For these arguments, too, are
not falsifiable; they do not allow testing by measurements. To me, string
theory and intelligent design belong in the same speculative, unproveable
category, and Smolin apparently agrees. "The scenario of many unobserved
universes plays the same logical role as the scenario of an intelligent
designer," he argues. "Each provides an untestable hypothesis that, if true,
makes something improbable seem quite probable."

I wouldn't put it quite like that. However, the thought that occurs to me
does seem to put the nail in the coffin. Suppose string theory, or some
other theory like MWI actually IS true. Then it necessarily follows that in
some (rare) universe, the so-called "anthropic coincidences" will indeed
occur. No-one can question the logic behind that (unless there is a finite
and too-small number of universes in the multiverse - e.g. one estimate of
sting theory is 10^500, which is not enough to defeat Koonin's odds of
10^(-1018).

However, let us suppose that such an explanation is possible for some rare
universe. My counter to that would be that it is also possible that an
alternative, as yet undiscovered mechanism will be discovered through
scientific research, that will make the emergence of life much more
probable. If this is the case, then the number of universes where this
mechanism happens will be much greater than the number where
"chance"/anthropic selection occurs. Of course, we don't know what this new
mechanism is - we haven't discovered it yet. But to appeal to the
multiverse as an explanation seems to me to be just as much an "argument
from ignorance" as the Intelligent Design argument.

So even if the multiverse is true, we still have to do "normal" science to
explain apparent coincidences in the appearance of life. All the multiverse
explanation does is give the atheist the comforting feeling that if there
isn't another mechanism, that at least there's an explanation that doesn't
involve God.

There is, of course, another nagging philosophical point, however. We rebut
Intelligent Design as non-science because it appeals to something with
universal (in the figurative sense of the word!) explanatory power. The
same applies to the multiverse. But to appeal to as-yet-undiscovered
science is also an appeal to something that potentially can explain
anything. It's the only thing to do for a scientist, but it seems to me
that it's still a philosophical commitment.

Iain

The review is at http://physicsworld.com/cws/article/print/26951

On 9/11/07, David Opderbeck <dopderbeck@gmail.com> wrote:
>
> Though I'm not competent to comment much on the merits, since you
> mentioned Lee Smolin, his book "The Trouble With Physics," which I read last
> year, is a great read. He convincingly argues that string theory isn't
> really a strong theory as "science" (convincing to me at least) and includes
> a very interesting discussion of the sociology science and theory
> development. (Amazon: http://tinyurl.com/2weed3)
>
> On 9/10/07, Iain Strachan <igd.strachan@gmail.com> wrote:
> >
> >
> > > If I understood, you are referring to string theory as "the most
> > > successful cosmology." I would caution care here, because string theory has
> > > not made any testable predictions and so it is dubious that it can claim any
> > > success at all. It has been formulated to be consistent with what we know
> > > in nature, but in trying to make it consistent, so many unobservable
> > > dimensions and extra degrees of freedom had to be put into the theory
> > > *ad hoc* that it ended up predicting this "string landscape" that is
> > > so large that now you can get any answer imaginable and not just what we
> > > observe. If the theory has to give you every possible answer in order to
> > > also give you the one right answer, then it is questionable that it is
> > > really a useful theory at all. This is why it has been called into question
> > > by many leading scientists. You could have produced the same result using
> > > any other framework other than strings. I hope you are aware of this.
> > > There are many ways to formulate a framework that can include everything we
> > > know plus a lot more. Simply keep adding unobservable degrees of freedom
> > > until the framework allows the right answer. The key to science is Occam's
> > > razor in which the fewest number of *ad hoc* assumptions gives you the
> > > correct answer. So the critique on string theory is exactly correct, as
> > > many scientists have formulated it.
> >
> >
> > Again, this is very much along the lines I've been thinking. I see the
> > same line of reasoning in my field of statistical pattern recognition, and
> > data-fitting. Given any data set of any size, one can fit a model that
> > agrees exactly with all of the data points by having sufficiently many
> > degrees of freedom (adjustable free parameters) in the model. N data points
> > may be exactly fitted by a degree N-1 polynomial. e.g. one can always
> > fit a parabola (degree-2) through three points. But this observation can
> > never tell us anything interesting about the data - for it to be interesting
> > in any way (and to have any predictive value) the number of degrees of
> > freedom must be very much less than the number of data points.
> > Specifically, with the exact fit, one "overfits" the data, meaning that the
> > function defined between the data points will oscillate rapidly and be
> > highly sensitive to the measurement noise. By the same token, Koonin's
> > paper invokes an unlimited number (as many as necessary) of parallel worlds
> > (in the MWI sense) to get over the apparent extreme improbability of life.
> >
> > I just discovered the following quote on the Wikipedia entry for Lee
> > Smolin, one of the strongest critics of string theory:
> >
> >
> >
> >
> > *The scenario of many unobserved universes plays the same logical role
> > as the scenario of an intelligent designer<http://en.wikipedia.org/wiki/Intelligent_design>.
> > Each provides an untestable hypothesis that, if true, makes something
> > improbable seem quite probable.* [3]<http://en.wikipedia.org/wiki/Lee_Smolin#_note-1>This
> > again is exactly what I have been saying from the start (though Smolin is
> > talking about string-theory based parallel universes rather than in the MWI
> > sense, the argument is the same). Koonin's paper contains at the end a
> > complete dismissal of Intelligent design. However, as Smolin's quote makes
> > evident, what Koonin replaced it with was something that fails in just the
> > same way.
> >
> > Quite pleased I had independently arrived at the same idea as Smolin. [Smug
> > mode off]
> >
> > Iain
> >
>
>

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