Brian Greene, The Elegant Universe. math whiz physics teacher at Columbia. Excellent book on string theory. I've been reading it for years, without quite yet finishing it. Greene did a documentary version which I've watched on TV more than once, and I just carefully watched the two DVD set. Obviously, I think it's good: and as laymen go, I read a lot of this stuff. Knatz.com has long commented on the excellence of Michio Kaku's book on the same subject: Hyperspace.
pk is forever proclaiming his innumeracy. Maybe it's me, maybe it was my schooling, but anything that looks like arithmetic freezes me like a Jew with a tatoo on his arm seeing a Nazi uniform. Algebra doesn't intimidate me; but neither do I know how to read the symbols beyond x and y and perhaps a power or two. Show me the symbols for calculus and I go as blank as I do for arithmetic. So I'm the last person to comment on the details of string theory, or any other physics. Nevertheless I love the ideas. I especially love the extended Kaluza-Klein space: the eleven dimensions. That's right up science-fiction-macroinformation-pk's alley.
This reader of science syntheses proclaims Greene's book and documentary to be the clearest presentation I've seen of the problems with unification theory: that is, the rift between Einstein's physics of gravity and the quantum world of electro-magnetism, the Strong force and the Weak force. If string theory, now M theory, can unite them, that's quite an accomplishment.
But I see some problems. Hence this bit of scribble. Indeed, pk in his innumeracy, together with pk's general skepticism (together with pk's will to believe), may have a perspective you're not likely to find among the physicists.
First I repeat a point Brian Greene couldn't have been clearer on: there is yet (as of the dates of The Elegant Universe) no experimental evidence to support string theory. String theory has yet made no predictions borne out in the lab or in the universe at large that we know of. Eddington tested Einsteinian Relativity. The testers decided that their results were positive. Physicists all over have tested quantum mechanics and find that no theory has ever tested more reliably. String theory hasn't failed any specific tests: string theory hasn't yet found a testable test. If a string is a million billion times smaller than an atom, how are we supposed to "see" one?
As one or two physicists interviewed in the documentary kept iterating, especially skeptical Sheldon Glashow of Boston University, if you can't test it, if there are no testable predictions, it's not science, it's not physics; it's philosophy.
I'm reminded of medieval Scholasticism. Guys like Edward Witten might have gotten along very well with guys like Saint Thomas Aquinas. Meanwhile, the math is said to be so beautiful I'll have to take their word for it string theory can't be ... wrong.
At one point Greene's NOVA documentary shows two guys calculating away on a blackboard. Finally they get some quantity in common: "256." I am reminded of a joke my mother's boss told her: guy hires a secretary, some young gal, gives her a calculation, tells her to check it twelve times if she has to. She goes off with her pad, comes back. "Did you check your results?" "Yes, I added the column twelve different times." "Good. What did you get." "Twelve different answers." (If pk, like the rest of us, hadn't been declawed by civilized morality, I'd have fed my mother's boss (that bastard's) liver to him.) The two string theorists finally get an answer in common. How many times before that had they gotten answers not in common? (Were any of the new secretary's twelve answers correct?) How does agreement prove anything? It doesn't to pk.
But of course once a physicist submits something for publication, others check it before publication. Then lots of others check it again. The rest of us are supposed to believe that they know what they're doing.
It's a real problem though in science. Once upon a time human calculators checked all human calculations. The human calculators had some agreement on their accuracy ratio. But today's science, weather prediction for example, depends entirely on calculations that humans can't do, let alone check. We have to trust our digital computers not to be allied in fooling us. Thus, science has changed.
And it may have to change further: to accept philosophy.
Tricky business. Slippery ground.
But what ground has ever not been slippery?
But I have one more related gripe to mention. Brian Greene keeps talking about "the beginning of time"; "time's first tick"; "time's last tick" ... String theorists, like relativity people (Stephen Hawking, for example), like the quantum people, talk about time as though time were finite. They can do their math backwards and forwards. Many a scientist with audio-visual equipment is fond of showing film running backwards. Since movies, we can do that: so we do it. But we only observe things, apart from movies, running "forwards." Ilya Prigogine posits time to be infinite. Ilya Prigogine deals with time running only forwards. Makes sense to me. Why don't the others listen?
I've never so much as heard them defend their assumption.
As I've said previously: science needs a good spring cleaning.