# String Theory

1. Dec 10, 2003

### Alethia

Okay I have to do a project on "the string theory." I've done some research on it using sources from the internet and some books--but I don't really understand what it exacly is. All of these things I have read explain it in such complex ways that make it difficult to grasp. I don't understand what it means by 'particles being excited,' or what a 'string' is. I know it is related to "Einstein's Dream." But, to put it blatantly, I do not understand its concepts. Anyone care to explain? ^.^

2. Dec 10, 2003

### Ambitwistor

Read the introductory chapters of Brian Greene's book The Elegant Universe.

What is the context?

Something being "excited" means increasing its energy.

If you're talking about a particle in, say, an atom, then "exciting" the particle means increasing its energy.

On the other hand, sometimes people say that particles are "excitations"; in string theory, particles correspond to different ways that a string can vibrate, so we can say that these particles (vibrational modes) are what you get when you "excite" a string.

A string is, well, a string...

Matter is usually thought of as made up of molecules, which are made up of atoms, which are made up of elementary particles like electrons ... which are not made up of anything else. Elementary particles are zero-dimensional, pointlike objects, which are not themselves made from anything smaller or simpler.

In string theory, electrons are not zero-dimensional points, they are one dimensional strings. These strings are "elementary" in the sense that we thought electrons were: they're not made up of out anything smaller or simpler; they are the simplest, most fundamental form of matter. Electrons are made up of them (or rather, electrons are strings that are vibrating in a certain way), and atoms are made up of electrons and other particles, etc.