Superstring theory - known less formally as "string theory" - is sometimes called the Theory of Everything (TOE), because it is a unifying physics theory that reconciles the differences between quantum theory and the theory of relativity to explain the nature of all known forces and matter. According to string theory, at the most microscopic level, everything in the universe is made up of loops of vibrating strings, and apparent particle differences can be attributed to variations of vibration. An object (such as an apple, for example) and a force (such as radiation, for example) can both be broken down into atoms, which can be further broken down into electrons and quarks, which can be, finally, broken down into tiny, vibrating loops of strings.
Quantum theory explains the nature and behavior of energy and matter on the microscopic scale, while the theory of relativity explains it on the macroscopic scale. Taken together, they form the basis for modern physics; nevertheless, integral aspects of the two theories conflict with each other in ways that have never been satisfactorily addressed. Although the theories work perfectly separately, equations involving both don't work at all. Einstein himself, unconvinced that nature would require entirely different modes of behavior for differently scaled phenomena, spent thirty years searching for what he called the unified field theory.
Superstring theory came to the forefront in the 1980s, when Michael Green at Queen Mary College and John Schwarz at the California Institute of Technology demonstrated that it had the potential to be the unifying theory that Einstein sought: one that could be used to describe gravity as well as electromagnetic forces.
According to string theory:
- All forces and particles in nature are derived from variations in vibrations of strings. As an example, gravity is said to arise from the lowest vibration of a closed string.
- There are ten dimensions in the natural world (nine spatial dimensions plus time), rather than the four of classical science (the three spatial dimensions plus time). What causes the extra six dimensions to be largely unnoticed is that they are considered to be compacted or curled up.
- The reason that general relativity doesn't work at the subatomic level is because the equation mistakenly includes a figure for point-like particles. Modifying the equation to include a representation of loops of string, instead, makes the equation work.
- String theorists are currently examining the possibility that the strings themselves have multiple dimensions, and are not, as was originally thought, massless (possessing only length, and no width). The idea is that the strings may actually be membranes.