|Nov3-05, 07:31 PM||#1|
Steven Weinberg bets Andrei Linde's life, and one dog
see page 13 of the paper:
"As for me, I have just enough confidence about the multiverse to bet the lives of both Andrei Linde and Martin Reesís dog."
a Steven Weinberg position paper on the string theory landscape, to be included in the book "Universe or Multiverse?" (Cambridge) where Lee Smolin also contributed "Scientific Alternatives to the Anthropic Principle"
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|Nov5-05, 03:56 PM||#2|
Tony Smith has done some helpful library work and come up with three quotes from Steven Weinberg which show a trend.
1986 - Weinberg said “… In the last two years, theoretical physicists have become intensely excited over the idea that the ultimate constituents of nature … are … strings. … [each of]… these theories … has no free parameters in it … ’solve the string theory’ … mean[s] to find out what these theories predict at much lower energies than 10^18 GeV …
The aim today is to try to find out whether the theory does in fact predict the standard model of the weak, electromagnetic, and strong interactions.
If it does then the second question is, what does it predict for those seventeen or more parameters of the standard model … the mass of the electron, the mass of the quarks, and so on?
If it does, then that’s it. …”. (from his 1986 Dirac Memorial Lecture)
1992 - Weinberg said “… Physicists will certainly keep trying to explain the constants of nature without resort to anthropic arguments. My own best guess is that we are going to find that in fact all of the constants (with one possible exception … the cosmological constant …) are fixed by symmetry principles of one sort or other and that the existence of some form of life will turn out not to require any very impressive fine-tuning of the laws of nature. …” (from his book Dreams of a Final Theory)
2005 - Weinberg said “… when the effort to extend the Standard Model to include gravity led to widespread interest in string theory, we expected to score the success or failure of this theory in the same way as for the Standard Model: String theory would be a success if its symmetry principles and consistency conditions led to a successful prediction of the free parameters of the Standard Model.
Now we may be at a new turning point, a radical change in what we accept as a legitimate foundation for a physical theory. …
Unless one can find a reason to reject all but a few of the string theory vacua, we will have to accept that much of what we had hoped to calculate are environmental parameters, like the distance of the earth from the sun, whose values we will never be able to deduce from first principles. … Theories based on anthropic calculation certainly represent a retreat from what we had hoped for: the calculation of all fundamental parameters from first principles….”. (from his paper Living in the Multiverse at hep-th/0511037)
Why has Weinberg relaxed his standards for a well-founded physical theory from
“predict … parameters of the standard model” in 1986
anthropic principle only for the cosmological constant / vacuum energy in 1992
“much of what we had hoped to calculate are environmental parameters” in 2005 ?
this was posted as the 34th comment on Peter Woit's blog about this paper
Tony Smith's homepage is
Tony is pointing out a lowering of standards in what Weinberg requires
as far as explaining the parameters of the standard model.
He asks what is the reason for this declining expectation of physical theory, at least on S.W. part and perhaps on some others' as well. Weinberg's paper could be read as apologetics for this decline in expectations, explaining and justifying it, or at least placing it in the best possible light.
As such it may well advance the dicussion of the surrounding issues by providing a exemplary statement of one of the possible viewspoints
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