M-Theory

In theoretical physics, M-theory is an extension of string theory in which 11 dimensions are identified. Because the dimensionality exceeds the dimensionality of five superstring theories in 10 dimensions, it is believed that the 11-dimensional theory unifies all string theories. Though a full description of the theory is not yet known, the low-entropy dynamics are known to be supergravity interacting with 2- and 5 dimensional membranes. This idea is the unique supersymmetric theory in eleven dimensions, with its low entropy matter content and interactions fully determined, and can be obtained as the strong coupling limit of type IIA string theory because a new dimension of space emerges as the coupling constant increases. Drawing on the work of a number of string theorists, Edward Witten of the Institute for Advanced Study suggested its existence at a conference at USC in 1995, and used M-theory to explain a number of previously observed dualities, sparking a flurry of new research in string theory called the second superstring revolution.