String Theory

String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects called strings, rather than the zero-dimensional point particles that form the basis for the standard model of particle physics. The phrase is often used as shorthand for Superstring theory, as well as related theories such as M-theory. By replacing the point-like particles with strings, an apparently consistent quantum theory of gravity emerges. Moreover, it may be possible to "unify" the known natural forces (gravitational, electromagnetic, weak nuclear and strong nuclear) by describing them with the same set of equations. (See Theory of everything.)

For a scientific theory to be valid it must be verified experimentally. Few avenues for such contact with experiment have been claimed.^[1] With the construction of the Large Hadron Collider in CERN some scientists hope to produce relevant data. It is generally expected though that any theory of quantum gravity would require much higher energies to probe. Moreover, string theory as it is currently understood has a huge number of possible solutions ^[2]. Thus it has been claimed by some scientists that string theory may not be falsifiable and may have no predictive power^[3][4][5][6].

Studies of string theory have revealed that it predicts higher-dimensional objects called branes. String theory strongly suggests the existence of ten or eleven (in M-theory^[7]) spacetime dimensions, as opposed to the usual four (three spatial and one temporal) used in relativity theory; however the theory can describe universes with four effective (observable) spacetime dimensions by a variety of methods. ^[8]

An important branch of the field is dealing with a conjectured duality between string theory as a theory of gravity and gauge theory. It is hoped that research in this direction will lead to new insights on quantum chromodynamics, the fundamental theory of strong nuclear force^[9][10][11]