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Elegant Universe Airs Tonight on PBS
fatarfy writes "USA Today among others has an article discussing tonight's presentation of Brian Greene's Elegant Universe, which discusses String Theory. It airs on PBS. From the article: 'The two segments of the show turn their spotlights on a crisis in physics, one invisible to the general public but increasingly embarrassing to the discipline. Simply put, Einstein's unbelievably accurate explanation of gravity, known as general relativity, is completely out of whack with the equally accurate explanation of electromagnetism, radioactivity and atomic forces known as quantum mechanics. The theories are mankind's most fundamental views of verifiable reality, and the disagreement means that something important about the universe eludes our understanding.' Sounds like it's worth watching."
Don't try too hard to find "Brian Greene's Elegant Universe" in your local listing. Instead, just watch Nova as planned, as that's the show which will be covering the topic. Part one is tonight. Part two is next week.
I don't know why the article (at least), or the headline (even better) didn't mention this. It's sort of the inverse of "The Lone Gunman are Dead".
Yes, it's in one of the seven links. Did you click all seven? I didn't.
Actually, PBS is allowing you to view the program on the website after both airings. (this week and next week)
From the site:
"Immediately following the broadcast of "The Elegant Universe" on October 28th and November 4, watch the entire three-hour special here. Each episode will be divided into chapters and can be viewed with the QuickTime or RealPlayer plug-ins. "
And the link:
http://www.pbs.org/wgbh/nova/elegant/program.html
It's a bit dated, but this bibliography has some of the more interesting works in the field.
> In order to be taken seriously -- indeed, to even be considered scientific
> -- a physical theory should be falsifiable.
Unless, of course, it happens to be _true_.
I'm not sure whether you meant this reply as a joke or not; the moderation suggests so, and perhaps my humor detector is even worse-off than it usually is. But it seems possible to me that your reply is serious, so (being both a physicist and an educator) I can't help myself . . .
Perhaps the most widely misunderstood property of modern science is that no proposition, no scientific theory, is ever proved to be absolutely true. No matter how much evidence you accumulate in favor of some theory or model, there's always the possibility that next week someone's going to come up with an experimental or observational result that requires that theory's revision or even outright rejection. Scientific theories can only be proven false; they can never be proved true.
"Yeah, yeah," you might be saying, "but I wasn't talking about whether theories can be proved true or not; I was talking about whether or not a theory actually is true. After all, even if we can't ever know with 100% certainty that a particular theory is true, it may still be true." Yes, indeed. But that's irrelevant to my original point, the one to which you replied. Since we cannot ever know with certainty whether any theory we put forward is absolutely true, and thus any theory is always subject to scrutiny, our requirement that the theory be falsifiable -- that it be possible to conceive of an experimental or observational result which would rule the theory out -- still stands.
I heard Greene on NPR's Science Friday He says that some recent work on the theory predicts some effects which may be testable in a few years by the newest generation of "atom smashers" currently under construction at CERN and elsewhere.
We may get to that "falsifiable" stage relatively soon...
http://mathworld.wolfram.com/Calabi-YauSpace.html
The above-linked page has a rough definition of the kind of space a 10-dimensional string theory might live on. I don't know why they take a product $M \times V$ --- why not allow a more general bundle of C-Y 3-folds?
The imaginary version of string theory which exists only in my mind has the universe as a bundle of Calabi-Yau 3-folds over $M$ (a real 4-manifold with a Minkowski metric, or something like that... anyway, a $(3,1)$ form --- that's a Minkowski metric, right???). That's 10 dimensions. The 11- or other-dimensional kinds of string theory, I have no idea.
Being an algebraic geometer (in training), I think of a C-Y 3-fold as a smooth projective complex 3-dimensional variety, or manifold, with trivial canonical bundle.
Well, that's the space. Then all kinds of crap happens *in* the space, with strings and stuff, and that's a whole nother story...
Er? QED is arguably the most accurate theory - something like what, 11 different measurements of alpha yield the same result to 10 digits or so? (I want to say that this is in Peskin & Schroeder's Quantum Field Theory, but I could be wrong). However, for one, that's only QED, not quantum mechanics in general. It's not like QCD is well tested - at all.
And, for two, it depends on what you mean by "accurate". Certain portions of GR - for instance, the equivalence principle - have been tested ridiculously accurate - 1 part in 10^12, or something like that. Plus, if memory serves, the binary pulsar measurement was ridiculously good in agreement.
QED is by far the more accurately tested theory of the two. By *far*. But if you group all quantum field theories together, then it's not so good (because strong strong interactions are just as hard as gravity), and "quantum field theories in general" start to look about as accurate as general relativity.
I think the basic idea is that QM and GR are fundamentally different theories. You look at them, and it sounds like you're talking about two different Universes, with two different physical laws. And the problem is, that within the domain of their accuracy (GR is large-scale, 'strong' gravity, QFTs are generally short-range 'weak' interactions, but only because the long range stuff is classical) they're both extremely accurate - about as accurate as the measurement can make. And the main problem is that no one has a friggin' clue how to unify the two.
Well, they have a clue. It's just that most of the time, that clue makes the universe look like a complete disaster. It's like in the 1930s, during the revolution in particle physics: "who ordered THAT?"