| MadSci Network: Physics |
Sarah, First, imagine a guitar string because there is a strong analogy between this kind of string and the theoretical objects in string theory. Once you fix the tension in a guitar string, the harmonic frequencies (or rates of vibration) are determined. That is, the tension determines the fundamental, the first overtone, the second overtone, etc. If you increase the tension, the frequencies of all the harmonics increase as well. The same is true in string theory. The string tension is a fundamental parameter of the theory. Once the tension is chosen, all the frequencies of vibration are determined, and these in turn determine the masses of the particles in the string theory's spectrum. The string tension can only be approximated because no one knows how to connect the predictions of string theory to the experimentally observed properties of real particles. The usual argument says that 1 divided by the square root of the string tension is the typical length scale of the string and this should be close to the Planck length, 1.6 x 10^-35 meters. But it could be twice the Planck length, or ten times the Planck length, or one hundred billion times the Planck length. No one knows. Here are some resources to explore: http://superstringtheory.com/basics/basic4a.html http://www.pbs.org/wgbh/nova/elegant/resonance.html http://www.discover.com/issues/aug-05/cover http://en.wikipedia.org/wiki/String_theory http://www.damtp.cam.ac.uk/user/mbg15/superstrings/superstrings.html --Dr. Randall J. Scalise http://www.phys.psu.edu/~scalise/
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