Tal Cohen's Bookshelf: A Collection of Personal Opinions about Books
(In reply to Eran Belinsky's message posted on Wednesday, 20 May 2009 at 16:23 GMT)

Tal Cohen writes in reply to Eran Belinsky:
Yes, Smolin discusses Khun's theory in this respect, and claims the situation is a bit more complicated here. With normal ''paradigm takeovers'', once refuting evidence begins to appear, the ''old guard'' first tries to fix the paradigm as much as possible, but eventually a better theory appears, which explains the results better, and sometimes even explains results which the old paradigm simply cannot explain -- at which point we have a paradigm shift. But here, string theory (ST) is not facing any refuting evidence; in fact, at the moment it seems like refuting evidence simply cannot exist.

Which brings me to your second question: at the moment, it seems like, indeed, no experiment can ever be conceived that will refute ST. That's because ST is in fact a vast landscape of theories (each with different values to various variables); none of these theories, if I understood Smolin correctly, was ever actually written down, and perhaps none can be. And, if ST is ''real'', only one of the immeasurable number of theories applies to ''our'' universe. Which one? We don't know.

So, if some future experiment does refute some version of ST, it never refutes ST in general, because ''believers'' can always claim that it simply shows that some other variant of ST is the real one.

The converse of this problem is that ST can't be used to make predictions; we don't know which version of ST is the right one, so we can't use it to predict any experimental outcomes.

The landscape of variants is so vast that it clearly violates basic scientific ideals (Occam's Razor comes to mind). Smolin finds it shocking that ST believers pick the Anthropic Solution to this problem, i.e., claiming that the universe is the way it is is because, of the huge number of potential universes, this is the one in which conscious life could evolve.
[391] Posted on Wednesday, 20 May 2009 at 16:46 GMT [Reply to this] [Permalink]

Archer Krantz writes in reply to Tal Cohen:
What are the major challenges against the anthropic principle? Is there a publication you can point to? I'd like to look into it since on the surface the principle seems reasonable. Is the argument against it simply an argument against the multiverse explanation of quantum physics?
[429] Posted on Monday, 19 October 2009 at 17:14 GMT [Reply to this] [Permalink]

Tal Cohen writes in reply to Archer Krantz:
In a way, it is indeed mostly an argument against the multiverse theory. I recommend you read Smolin directly for his detailed arguments (I don't have the book at hand so I can't provide any reference he cites.)
[430] Posted on Monday, 19 October 2009 at 21:47 GMT [Reply to this] [Permalink]

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