Re: GR or QED?
George Murphy (email@example.com)
Thu, 30 Apr 1998 07:26:42 -0400
Glenn R. Morton wrote:
> At 02:58 PM 4/29/98 -0400, George Murphy wrote:
> > While there is nothing wrong with noting the high precision of
> >such experiments, it can be a little misleading in the context of
> >anthropic principles because it suggests that the universe must have
> >been fine tuned to this precision in order for intelligent life to
> >develop & that isn't the case.
> I do know that Ross holds that the critical expansion (based upon the
> inflationary view) must be correct to within 1 part in 10^-55 or life
> couldn't exist.
> He says, "How critical is this expansion rate? According to Alan Guth, it
> must be fine-tuned to an accuracy of one part in 10^55." Fingerprint of
> God, p. 124
> What could I learn from you about this claim? As I understand it, there is
> now some significant doubt about the inflationary universe, given the
> evidence for the cosmological constant. While this may not have entirely
> won the day, is Ross' claim correct? Would it contradict your assertion
My comment referred to the precision of local isotropy, not
necessarily to all physical parameters.
It's true that there would have had to be very precise fine
tuning for a cosmological model in which space (not space-time) is as
close to being flat as it is. (I.e., the density d & Hubble parameter H
are in the ballpark of satisfying H^2 = 8*G*d/3.) Inflationary models
provided an explanation for this. If they don't work then for the time
being we have no scientific explanation for this near coincidence.
George L. Murphy