String theory

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String theory is a developing theory in particle physics that attempts to reconcile quantum mechanics and general relativity.[1] It is a contender for the theory of everything (TOE), a manner of describing the known fundamental forces and matter in a mathematically complete system. The theory has yet to make testable experimental predictions, which a theory must do in order to be considered a part of science.

String theory mainly posits that the electrons and quarks within an atom are not 0-dimensional objects, but rather 1-dimensional oscillating lines ("strings"). The earliest string model, the bosonic string, incorporated only bosons, although this view developed to the superstring theory, which posits that a connection (a "supersymmetry") exists between bosons and fermions. String theories also require the existence of several extra, unobservable, dimensions to the universe, in addition to the usual four spacetime dimensions.

The theory has its origins in the dual resonance model (1969). Since that time, the term string theory has developed to incorporate any of a group of related superstring theories. Five major string theories were formulated. The main differences among them were the number of dimensions in which the strings developed and their characteristics; all of them appeared to be correct, however. In the mid 1990s a unification of all previous superstring theories, called M-theory, was proposed, which asserted that strings are really 1-dimensional slices of a 2-dimensional membrane vibrating in 11-dimensional space.

As a result of the many properties and principles shared by these approaches (such as the holographic principle), their mutual logical consistency, and the fact that some easily include the standard model of particle physics, some mathematical physicists (e.g. Witten, Maldacena and Susskind) believe that string theory is a step towards the correct fundamental description of nature.[2][3][4][5][unreliable source?] Nevertheless, other prominent physicists (e.g. Feynman and Glashow) have criticized string theory for not providing any quantitative experimental predictions.[6][7]


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