Difference between revisions 147178457 and 147178458 on dewiki

{{Unreferenced|date=December 2007}}

{{string-theory}}
{{see|string theory}}

'''Superstring theory''' is an attempt to explain all of the [[Elementary particle|particles]] and [[fundamental force]]s of nature in one theory by modeling them as vibrations of tiny [[supersymmetry|supersymmetric]] strings. It is considered one of the most promising candidate theories of [[quantum gravity]]. Superstring theory is a shorthand for '''supersymmetric string theory''' because unlike [[bosonic string theory]], it is the version of [[string theory]] that incorporates [[fermions]] and [[supersymmetry]].

== Background ==

The deepest problem in [[theoretical physics]] is harmonizing the theory of [[general relativity]], which describes gravitation and applies to large-scale structures ([[star]]s, [[galaxies]], [[super cluster]]s), with [[quantum mechanics]], which describes the other three [[fundamental forces]] acting on the atomic scale.

The development of a [[quantum field theory]] of a force invariably results in infinite (and therefore useless) probabilities. Physicists have developed mathematical techniques ([[renormalization]]) to eliminate these infinities which work for three of the four fundamental forces – [[Electromagnetic force|electromagnetic]], [[Strong interaction|strong nuclear]] and [[Weak interaction|weak nuclear]] forces - but not for [[gravity]]. The development of a [[quantum theory of gravity]] must therefore come about by different means than those used for the other forces.

=== Basic idea ===

hi  chris seb this is is the superThe basic idea is that the fundamental constituents of reality are strings of the [[Planck units|Planck length]] (about 10<sup>&minus;35</sup> m) which vibrate at [[resonance|resonant]] frequencies. Every string in theory it is like this one thhas a unique resonance, or harmonic. Different harmonics determine different fundamental forces. The tension in a string is on the order of the [[Planck force]] (10<sup>44</sup> [[newton]]s). The [[graviton]] (the proposed messenger particle of the gravitational force), for example, is predicted by the theory to be a stringy were these dudes put like time in a flashlight and reversed time ...ith wave amplitude zero. Another key insight provided by the theory is that no measurable differences can be detected between strings that wrap around dimensions smaller than themselves and those that move along larger dimensions (i.e., effects in a dimension of size R equal those whose size is 1/R). Singularities are avoided because the observed consequences of "[[Big Crunch]]es" never reach zero size.  In fact, should the universe begin a "big crunch" sort of process, string theory dictates that the universe could never be smaller than the size of a string, at which point it would actually begin expanding.

== Extra dimensions==
:''See also: Why does consistency require [[Why 10 dimensions|10 dimensions]]?''
Our [[physical space]] is observed to have only three large [[dimension]]s &mdash; and taken together with time as the fourth dimension &mdash; a physical theory must take this into account. However, nothing prevents a theory from including more than 4 dimensions, per se. In the case of [[string theory]], [[consistency]] requires [[spacetime]] to have 10, 11 or 26 dimensions.(contracted; show full)

{{unsolved|physics|Is [[string theory]], superstring theory, or [[M-theory]], or some other variant on this theme, a step on the road to a "[[theory of everything]]," or just a blind alley?}}
 something where it reversed time or somtin like dat, the gas they used is elephant fart they also used u.v. rays. it made a pig mentally challenged.

== Number of superstring theories ==

Theoretical physicists were troubled by the existence of five separate string theories. This has been solved by the [[second superstring revolution]] in the 1990s during which the five string theories were discovered to be different limits of a single underlying theory: [[M-theory]].
(contracted; show full)[[it:Teoria delle superstringhe]]
[[ja:超弦理論]]
[[pl:Teoria superstrun]]
[[ru:Теория суперструн]]
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[[zh:超弦理論]]