String theory

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String theory, (or super-string theory when coupled with Supersymmetry), is a class of models in theoretical physics which replace zero-dimensional points (particles) in four-dimensional spacetime with one-dimensional strings in an eleven-dimensional spacetime as the fundamental building block of the universe. The elusive goal is to develop a set of equations that unify all known natural forces (gravitational, electromagnetic, weak, and strong), according to some preconceived philosophical beliefs about how they ought to be unified. Leading proponents of string theory have been Edward Witten of the Institute for Advanced Study and Brian Greene, the renowned author of The Elegant Universe.

There is much debate on whether string theory is truly scientific. Under the positivist philosophy, models must be falsifiable (i.e. it must be possible to define an experiment which could contradict the theory) for them to qualify as science, and then they must survive these tests. In more general terms, a model is not scientific unless we can use it to make predictions about the world we observe, and it is consistent with those predictions. String theory has yet to yield a particular definitive test, or to produce any models that resemble any known particles or forces.

The discovery of dark energy in 1998 was a particularly damaging blow to string theory. It was just the sort of thing that string theorists hoped to explain, and yet string theory cannot explain it. As of today, string theory has attracted strong intetrest among theorists but has not suggested any critical experiments.

Some string theorists, such as Leonard Susskind, say that string theory may not be testable but may still provide insights on multiple universes. His recent book is The Cosmic Landscape: String Theory and the Illusion of Intelligent Design.

External links

The Elegant Universe (Nova TV Series discussing Strings)