We spent quite a bit of time discussing how energy shows up in earlier physics, so how is it carried here? Strings can carry energy in essentially three ways: by being stretched (like the energy stored in a rubber band), by moving as a whole (like a point particle), and by vibrating (like a guitar string).
Let's go over the new parts in a bit more detail. The effective mass of a string depends on its length: stretching it costs energy, and its "natural" mass is zero. As for vibrations, they will travel around the string in one direction or the other (we arbitrarily call them "left-moving" and "right-moving" to distinguish the two). But because the strings are so small, those vibrations can't be seen directly: they would look like a form of internal energy to us. You may already see where I'm going with this: a string's vibrational energy will look like mass to us. But first, we'll add quantum mechanics to the mix.
(The vibration modes shown here look like the quantum particle on a circle, but don't be fooled! These are purely classical motions at this stage.)
Up to my research page.
Up to my professional page.
My personal site is also available.
Any questions or comments? Write to me: jensens@alma.edu
Copyright © 2004 by Steuard Jensen.