le physics, strings interact in a way that is almost uniquely specified by mathematical self-consistency, forming an apparently valid quantum theory of gravity. Since its birth as the dual resonance model which described the strongly interacting hadrons as strings, the term string theory has changed to include any of a group of related superstring theories and larger frameworks such as M-theory, which unite them. A shared property of all these theories is the holographic principle. String theorists have not yet completely described these theories, nor have they determined if the