Retrodiction

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Retrodiction (or postdiction, though this should not be confused with the use of the term in criticisms of parapsychological research) is the act of making a "prediction" about the past. This is especially useful when one wishes to test a theory whose actual predictions are too long-term to be of immediate use. One speculates about uncertain events in the more distant past so that the theory would have predicted a known event in the less distant past. This is useful in, for example, the fields of archaeology, climatology, evolutionary biology, financial analysis, forensic science, and cosmology.

Michael Clive Price has written:

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.^[1]

Postdiction, in a slightly different sense, is used to evaluate speculative theories such as those formulated by theoretical physicists. In this case it refers to predicting known (but not necessarily past) events. For example, a theory attempting to extend or replace the standard model that fails to predict the existence of known particles has not met the test of postdiction.