Science for today: "How long is it?"

Pay attention, class:

Welcome to the wacky world of M-theory (the theory formerly known as string). Based around the attempt to fit Einstein's general theory of relativity into the classical world of particle physics, it replaces particles with strings. These strings (depending on their state) appear as different particles.
This has given rise to a number of string theories, unified as M-Theory.

Check out the Official String Theory Website. It's not clear who's published this, but the list of luminaries involved makes for impressive reading. Many of them popped up in Channel 4's The Theory of Everything.

Don't be shy - I've kept the links nice and simple....