The Butt Ugly Weblog

Uh, there's a couple of nice bits in the animation, but most of it is in fact nonsense, at least as far as string theory is concerned. Bryanton seems to equate the wavefunction (that describes the set of possibilities of a particle) with the extra spatial dimensions in string theory, which is utterly and completely wrong. His points about curvature in the extra dimensions (the Möbius strip example) are good, but could be illustrated just in the four-dimensional case. The rest of it is either very muddled or just plain wrong.

String theory is a quantum theory just like the usual quantum mechanics of a point particle. The need to introduce extra spatial dimensions arises from reasons of mathematical consistency (there are some extra conditions that appear when you quantise a two-dimensional object). But it would be misleading to say that the quantum states of the system are somehow orthogonal to our four-dimensional universe: the extra spatial dimensions are just that, new directions just like length, width and breadth (and notably, not timelike).

It would be nice to see a visualisation of this sort that also gets the facts right. Andrew J. Hanson has created some nice images of three-dimensional cross-sections of Calabi-Yau manifolds, for example.

http://www.cs.indiana.edu/~hanson/

[Calabi-Yau manifolds are the shape that the extra six dimensions need to have for string theory to yield physically sensible results.]

And of course, everybody knows that M-theory is in fact eleven-dimensional, so Bryanton misses at least one. :-)

- Hannu, recovering string theorist

--Hannu, 06-Aug-2006

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