In string theory, the nature of reality changes. We are used to thinking that the world is composed of particles, an assumption formalised by the Standard Model. In string theory, however, particles are no longer fundamental: at very short distances they appear to be tiny vibrating strings.
These strings play nicely with both quantum mechanics and relativity. They contain a remarkable amount of content. Indeed quantum strings easily give rise to the particles we observe, for both forces and matter.
Despite its apparent elegance, string theory requires many elaborate concepts. It depends upon supersymmetry, and requires six extra dimensions. There remains no experimental evidence for these exotic demands, which are unpalatable to some physicists.
Nevertheless pioneering researchers have unearthed a rich underlying structure. String theory has significant and appealing dualities, unexpectedly linking diverse areas of mathematics and physics. Strings themselves are merely simple cases of mysterious spacetime membranes. The true framework for strings is grander than its founders could have possibly imagined.
Much current research focuses on the dauntingly named AdS/CFT correspondence. This deep conjecture enables physicists to model a broad range of phenomena. It is not yet fully understood, and much effort is devoted to uncovering its mysteries.
These are the tools in a string theorist’s treasure chest. But the box is by no means full. Today, enquiring minds continue to discover new implements and hone existing machinery. Jump in and take a look at what they’ve found so far.