Introduction to M-theory: Difference between revisions

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String theory as described above ran into a problem: another version of the equations was discovered, then another, and then another. Eventually, five major string theories were developed. The main differences between the theories were principally the number of dimensions in which the strings developed, and their characteristics (some were open loops, some were closed loops, etc.). Furthermore, all these theories appeared to be workable. Scientists were not comfortable with five seemingly contradictory sets of equations to describe the same thing.

Speaking at the string theory conference at the University of Southern California in 1995, [[Edward Witten]] of the [[Institute for Advanced Study]] [[second superstring revolution|suggested that]] the five different versions of string theory might be describing the same thing seen from different perspectives.<ref>{{Cite web |url=http://physics.usc.edu/Strings95/program.html |title=University of Southern California, Los Angeles, Future Perspectives in String Theory, March 13-18, 1995, E. Witten: Some problems of strong and weak coupling |access-date=2017-04-08 |archive-date=2020-11-15 |archive-url=https://web.archive.org/web/20201115210233/http://physics.usc.edu/Strings95/program.html |url-status=live }}</ref> He proposed a unifying theory called "[[M-theory]]", in which the "M" is not specifically defined but is generally understood to stand for "membrane". The words "matrix", "master", "mother", "monster", "mystery" and "magic" have also been claimed. M-theory brought all of the string theories together. It did this by asserting that strings are really one-dimensional slices of a two-dimensional membrane vibrating in 11-dimensional [[spacetime]]. Vibrations of higher-dimensional objects (as in three-dimensional vibrating blob or sphere or even more possible dimensions) are certainly a part of M-theory,<ref>{{Cite web | url=https://physics.stackexchange.com/questions/73808/does-string-m-theory-address-higher-dimensional-membrane-vibration-modes | title=Quantum gravity – Does string/M-theory address higher-dimensional membrane vibration modes? | access-date=2017-08-05 | archive-date=2020-11-15 | archive-url=https://web.archive.org/web/20201115210238/https://physics.stackexchange.com/questions/73808/does-string-m-theory-address-higher-dimensional-membrane-vibration-modes | url-status=live }}</ref> but the basic theory of branes is still in progress. Higher-dimensional objects are much harder to mathematically calculate than a point in [[classical physics]] or a one-dimension string in string theory or two-dimensional membranes in M-theory.

==Status==