A multiverse of probabilities
Ben Freivogel · Physics World · 2010
String theory unifies all of physics, from the smallest to the largest scales. It proposes that the basic constituents of the world are tiny strings moving in a realm with 10 spatial dimensions. Unlike the Standard Model of particle physics, which requires that experimentally determined values of the physical constants be added into it, there are no free parameters in string theory. It would seem, therefore, that one could derive all of physics from the theory without any experimental input. This quality has long been a key element of string theory's appeal. Such first-principles predictions seemed within reach in the heady days of the "first superstring revolution" in the mid-1980s. I even heard that during this period one famous physicist predicted that string the orists would derive the mass of the electron by Christmas.