Superseded Scientific Theories

Superseded Scientific Theories

A superseded, or obsolete, scientific theory is a scientific theory that was once commonly accepted but that is no longer considered the most complete description of reality by a mainstream scientific consensus, or a theory which has been shown to be false. This label does not cover protoscientific or fringe science theories with limited support in the scientific community, nor does it describe theories that were never widely accepted. Some theories which were only supported under specific political authorities, such as Lysenkoism, may also be described as obsolete or superseded.

In some cases a theory or idea is found to be baseless and is simply discarded: for example, the phlogiston theory was entirely replaced by the quite different concept of energy and related laws. In other cases an existing theory is replaced by a new theory which retains significant elements of the earlier theory; in these cases, the older theory is often still useful for many purposes, and may be more easily understood than the complete theory and lead to simpler calculations. An example of this is the use of Newtonian physics, which differs from the currently accepted relativistic physics by a factor which is negligibly small at velocities much lower than that of light. All of Newtonian physics is so satisfactory for most purposes that it is more widely used except at velocities not small compared with that of light, and simpler Newtonian but not relativistic mechanics is usually taught in schools. Another case is the theory that the earth is approximately flat; while it has for centuries been known to be wrong for long distances, considering part of the earth's surface as flat is usually sufficient for many maps covering areas which are not extremely large, and surveying.

Karl Popper suggested that a theory should be considered scientific if and only if it can in principle be falsified by experiment; any idea not susceptible to falsification does not belong to science.