Superseded scientific theory

A superseded, or obsolete, scientific theory is a scientific theory which has lost support due to emergence of new scientific understanding. The term does not include theories not supported by the scientific community or fringe science, or theories never widely accepted. Some theories which were only supported under specific political authorities may be included such as flat Earth theory or Lysenkoism.

In some cases an obsolete theory is still useful because it provides a description that is "good enough" for a particular situation, and is more easily used than a later theory. An example of this is the use of Newtonian physics in many mechanical engineering applications, and even in calculating the orbits of satellites, and the use of Conservation of mass in chemistry; in both cases, the error due to these simplifying assumptions is smaller than other sources of error.

Karl Popper suggested that all scientific theories should be falsifiable otherwise they could not be tested by experiment. Anything that cannot be shown by experiment to be false would therefore be an axiom and have an absolute status, beyond any confirmation or refutation.

Biology

Lamarckism — but revitalised in Neo-Lamarckism. See also: epigenetic inheritance
Maternal impression — rendered obsolete by genetic theory
Miasma theory of disease — rendered obsolete by germ theory of disease
Spontaneous generation (Aristotelian abiogenesis)
Recapitulation theory — or "ontogeny recapitulates phylogeny"
Vitalism — replaced by reductionism and germ theory

Chemistry

Caloric theory
Phlogiston theory — replaced by Lavoisier's work on oxidation
Part of Dalton's law
Vital essence theory

Physics

Aristotelian theory of gravity — discredited by Galileo.
Newtonian mechanics — replaced by special and general relativity, which have greater accuracy
Aether theory of Maxwell — failed in the Michelson-Morley experiment, made obsolete by Einstein's work
Caloric theory — Lavoisier's successor to phlogiston, obsolesced by Rumford's and Joule's work
John Dalton's model that atoms are tiny spheres with hooks that allow them to combine. (Note that otherwise Dalton's atomic theory was quite accurate)
Plum pudding model of the atom, by J. J. Thomson — assuming the protons and electrons were mixed together in a single mass
Ernest Rutherford's model of the atom (electrons can be in any orbit about the nucleus)
Neils Bohr's model of the atom (was accurate for the hydrogen atom only).

See also: Gravity, Alternative theories

Astronomy and cosmology

Ptolemaic system/Geocentric universe — obsoleted by Copernicus and Galileo
Copernican system — obsoleted by Johannes Kepler and Isaac Newton
Newtonian Mechanics — although still widely used, formally obsoleted by Albert Einstein's relativistic mechanics
Steady state theory — superseded by the big bang model

Geography and climatology

Flat Earth theory
The Open Polar Sea, an ice-free sea once supposed to surround the North Pole. Note, however, that global warming has left the North Pole itself free of ice in a number of recent years, and is expected to permanently open the Northwest Passage later in the 21st century
Rain follows the plow — the theory that human settlement increases rainfall in arid regions (only true to the extent that crop fields evapotranspirate more than barren wilderness)

Geology

Geosyncline theory — replaced by subduction
Continental drift — superseded by plate tectonics

Medicine

Theory of the four bodily humours
Eclecticism — medical history — Some say it transformed into homeopathy and pseudoscience

Psychology

Persistence of vision — to a fairly good level it is rejected by investigative psychologists
Behaviorism - now fallen into disfavor, it was widely accepted in the 1950s

Obsolete branches of enquiry

Alchemy — which led to the development of chemistry
Astrology — which led to the development of astronomy
Phrenology — was once widely studied but now considered a pseudoscience
Numerology — as distinct from number theory, now considered a pseudoscience

Approximate theories

Here are theories that are no longer considered the most complete representation of reality, but are still useful in particular domains. For many theories a more complete model is known, but in practical use the coarser approximation provides good results with much less calculation.

Atomic theory — atoms are no longer thought to be indivisible, but are now seen to be composites
Nuclei disintegrate at high energy
The Heliocentric Model and Geocentric Model — still used as computational instruments in celestial mechanics
Newtonian mechanics — superseded by Theory of Relativity and quantum mechanics. Still useful in engineering and physics at either middling (human) scales or where appreciable fractions of the speed of light need not be considered
Bohr model of the atom — allows for exact solution of the hydrogen atom, but larger atoms are not well described
Newton's sine-square law for the force of a fluid on a body — no longer considered useful at low speeds, though it has found application in hypersonic flow
Flat Earth — most ordinary people navigating short distances (hundreds of miles/km) assume the Earth is flat (for example, assuming that all north-south streets in an inner city are parallel). This also extends to assumptions such as that after walking 3 miles west and 4 north, it is 5 miles directly back to the starting point — on a round Earth, it is actually very slightly less

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