What retrodictions does many-worlds make?
A retrodiction occurs when already gathered data is accounted for by a later theoretical advance in a more convincing fashion. The advantage of a retrodiction over a prediction is that the already gathered data is more likely to be free of experimenter bias. An example of a retrodiction is the perihelion shift of Mercury which Newtonian mechanics plus gravity was unable, totally, to account for whilst Einstein’s general relativity made short work of it. Many-worlds retrodicts all the peculiar properties of the (apparent) wavefunction collapse in terms of decoherence. (See “What is decoherence?”, “Can wavefunctions collapse?”, “When do worlds split?”and “Why do worlds split?”) No other quantum theory has yet accounted for this behaviour scientifically. (See “What are the alternatives to many- worlds?
) Second, the mathematical structure of many-worlds is not isomorphic to other formulations of quantum mechanics like the Copenhagen interpretation or Bohm’s hidden variables. The Copenhagen interpretation does not contain those elements of the wavefunction that correspond to the other worlds. Bohm’s hidden variables contain particles, in addition to the wavefunction. Neither theory is isomorphic to each other or many-worlds and are not, therefore, merely rival “interpretations”. Third, there is no scientific, reductionistic alternative to many- worlds. All the other theories fail for logical reasons.
