Duality, Spacetime and Quantum Mechanics

QUANTUM MECHANICS T purpose of this article is to describe some themes in theoretical physics that developed independently for many years, in some cases for decades, and then converged rather suddenly beginning around 1994—95. The convergence produced an upheaval sometimes called "the second superstring revolution." It is as significant in its own way as "the first superstring revolution," the period around 1984-85 when the potential of string theory to give a unified description of natural law was first widely appreciated. Some of the themes whose convergence we explore here are depicted in figure 1. Their diversity is part of the charm of the second superstring revolution, in which a major new perspective on the quest for superunification of the forces of nature has developed from the interplay of esoteric ideas about physics at ultrahigh energies with down-to-earth investigations of the physical properties of gauge theories in four dimensions.