Brian D Harper wrote:
> This will be my last message before signing off for awhile.
> Be back around July 6.
Shucks, lets continue this when you get back.
>
>
> At 08:59 PM 6/22/99 -0500, Glenn wrote:
> >Brian Harper wrote:
>
> >Well, I obviously disagree. Unfortunately, one seldom finds a
> >precise definition of fine-tuning in the literature and one
> >has to read between the lines. For example, the Sciama paper
> >I quoted from would be utter nonsense if fine-tuning were
> >tied to probability calculations.
>
> >Briefly looking through my papers on the AP, the closest thing
> >I found to a definition of fine-tuning is the following from
> >Leslie
>
> >#"Recently, many have argued that either reality as a whole,
> >#or else the spatiotemporal region which we can see, is
> >#"fine-tuned" to life's needs, by which they mean that tiny
> >#changes in its basic properties would have excluded life
> >#forms of any kind. (Talk of "fine-tuning" does not presuppose
> >#a divine fine-tuner.)"
> ># -- John Leslie "Introduction" to <Physical Cosmology and
> >#Philosophy>, edited by Leslie, Macmillan, New York, 1990.
> >
> >One of the things I do for a living is to try to develop
> >models. Leslie's definition of fine-tuning fits
> >perfectly with the way I would use the term in my own
> >work. Suppose I have some model Y which I want to produce
> >some response X (X in my case would usually be to fit
> >some data sets X1, X2, X3 etc. obtained in various special
> >cases). The model has several parameters a,b,c,d....
> >Parameter c, say, would be finely tuned wrt X if it must
> >fall in some very narrow range in order for Y-->X. I
> >would say c is finely tuned regardless of how it is obtained.
> >Probability doesn't have anything to do with it, unless
> >I were to make some bold claim that I had determined c
> >by picking numbers at random ;-).
Oh man are we seeing two sides of the same coin. The narrow range implicitly
assumes that if a wider range were used, then the universe would not be
finely tuned. It implies a comparison. If in your example above, c could
ONLY range from 5-6 (not because of some resultant hospitiable universe, but
because fundamentally c can only be between 5 and 6) then to find a universe
with c = 5.7 would not be considered fine tuning. But if c can assume ANY
value, but only values of 5-6 allow for life, then the universe is finely
tuned BECAUSE of the comparison between the possible range and the range with
acceptable results. . If any value of the nuclear carbon resonance would lead
to the creation of carbon in supernova, then the universe would not be finely
tuned. Correct? You MUST make an implicit comparison for fine tuning to
take place.
>
>
> Now let me go back to your final statement:
>
> "The choice of one out of an innumerable plethora
> of hostile possibilities is what makes the anthropic
> principle work." -- Glenn
>
> Not really. The main point I believe is the fine-tuning
> as defined above combined with the appearance that the
> laws of physics care about whether there is or isn't
> life. Recall Sciama's comment:
>
> "These finely tuned properties will probably also eventually
> be accounted for by fundamental theory. But why should fundamental
> theory _happen_ to lead to these properties?" -- D. Sciama
And lets hope that there are no arbitrary constants in that final fundamental
theory.