What is string theory?
String theory is an incomplete mathematical approach to theoretical physics. It's building blocks are one-dimensional extended objects called strings, instead of the zero-dimensional point particles that form the basis of the standard model of particle physics. By replacing the point-like particles with strings, an apparently consistent quantum theory of gravity emerges, which has not been achievable under the standard model. The term string theory usually, includes a group of related superstring theories and a few related theories such as M-theory. Superstring theory is an attempt to explain all of the particles and fundamental forces of nature in one theory. It is one of the most promising theories of quantum gravity.
There are two basic types of string theories
1. Those with closed string loops that can break into open strings.
2. Those with closed string loops that can't break into open strings.
Pythagoras could be called the first known string theorist. He figured out the first known string physics the harmonic relationship. Pythagoras who was an excellent lyre player realized that vibrating Lyre strings of equal tensions and different lengths would produce harmonious notes if the ratio of the lengths of the two strings was a whole number.
In string theory the elementary particles we observe in particle accelerators could be thought of as the "musical notes" or excitation modes of elementary strings. The string must be stretched under tension in order to become excited. The strings in string theory are floating in spacetime yet like the strings of the lyre they have tension. The string tension in string theory is denoted by the quantity 1/(2 p a'), where a' is pronounced "alpha prime"and is equal to the square of the string length scale.
If string theory is to be a theory of quantum gravity, then the average size of a string should be somewhere near the length scale of quantum gravity This length is called the Planck length, which is about 10-33 centimeters. This means that strings are way too small to see by current or expected particle physics technology. This means that string theorists must devise new more clever methods to test the theory than just looking for the strings in particle experiments.
One of Physics biggest questions is Why is the universe the way it is?
String theorists have been slammed for there inability to answer this question. Now they are fighting back.
If some of the laws of physics where just slightly different the universe would be a completly different, even dangerous place and life may never have come to be. Sting theory has so far been unable to explain why the universe has developed the way it has. What it does show is that the Big Bang produced any e of a number of different outcomes. It can also be used as a starting block for the theory of multiple/parallel universes. But recently a group of mathematicians exploring the geometry of string theory's many predicted universes have come to the conclusion that there may only be one universe after all.