The basic idea, simple and revolutionary at the same time, to replace the concept of a point particle with a one-dimensional string, has opened up a whole new field of research. Even today, four decades later, its multifaceted consequences are still not fully conceivable.

Up to now string theory has offered a new way to view each particle:

as different excitations of the same fundamental object. It has celebrated success in discovering the graviton in its spectrum, and it has naturally led scientists to posit space-times with more than four dimensions--which in turn has...