Editing Elementary particle (section)

=== String theory ===
{{Main|String theory}}

String theory is a model of physics whereby all "particles" that make up [[matter]] are composed of strings (measuring at the Planck length) that exist in an 11-dimensional (according to [[M-theory]], the leading version) or 12-dimensional (according to [[F-theory]]<ref>{{cite journal |doi=10.1016/0550-3213(96)00172-1 |arxiv=hep-th/9602022 |bibcode=1996NuPhB.469..403V |title=Evidence for F-theory |year=1996 |last1=Vafa |first1=Cumrun |journal=Nuclear Physics B |volume=469 |issue=3 |pages=403–415|s2cid=6511691 }}</ref>) universe. These strings vibrate at different frequencies that determine mass, electric charge, color charge, and spin. A "string" can be open (a line) or closed in a loop (a one-dimensional sphere, that is, a circle). As a string moves through space it sweeps out something called a ''[[world line#World lines as a tool to describe events|world sheet]]''. String theory predicts 1- to 10-branes (a 1-[[Membrane (M-theory)|brane]] being a string and a 10-brane being a 10-dimensional object) that prevent tears in the "fabric" of space using the [[uncertainty principle]] (e.g., the electron orbiting a hydrogen atom has the probability, albeit small, that it could be anywhere else in the universe at any given moment).

String theory proposes that our universe is merely a 4-brane, inside which exist the three space dimensions and the one time dimension that we observe. The remaining 7&nbsp;theoretical dimensions either are very tiny and curled up (and too small to be macroscopically accessible) or simply do not/cannot exist in our universe (because they exist in a grander scheme called the "[[multiverse]]" outside our known universe).

Some predictions of the string theory include existence of extremely massive counterparts of ordinary particles due to vibrational excitations of the fundamental string and existence of a massless spin-2 particle behaving like the [[graviton]].