Retrodiction

The activity of retrodiction (or postdiction) involves moving backwards in time, step-by-step, in as many stages as are considered necessary, from the present into the speculated past to establish the ultimate cause of a specific event (for instance, in the case of reverse engineering, forensics, etc.).

Given that retrodiction is a process in which "past observations, events and data are used as evidence to infer the process(es) that produced them" and that diagnosis "involve[s] going from visible effects such as symptoms, signs and the like to their prior causes",[2] the essential balance between prediction and retrodiction could be characterized as: regardless of whether the prognosis is of the course of the disease in the absence of treatment, or of the application of a specific treatment regimen to a specific disorder in a particular patient: In the scientific method, the terms retrodiction or postdiction are used in several senses.

For example, a theory in physics that claims to extend or replace the standard model but that fails to predict the existence of known particles has not met the test of postdiction.

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.

This is useful in, for example, the fields of archaeology, climatology, evolutionary biology, financial analysis, forensic science, and cosmology.