Superseded scientific theories

 A superseded, or obsolete, scientific theory is a scientific theory that was once commonly accepted but (for whatever reason) is no longer considered the most complete description of reality by mainstream science; or a falsifiable theory which has been shown to be false. This label does not cover theories that are yet to gain wide support in the scientific community (protoscience or fringe science). This also does not cover theories that were never widely accepted. Some theories which were only supported under specific political authorities, like Lysenkoism, may also be included.

In some cases, the theory has been completely discarded. In other cases, the theory is still useful because it provides a description that is "good enough" for a particular situation, and is more easily used than the complete theory (often because the complete theory is too mathematically complex to be easily usable). An example of this is the use of Newtonian physics in many mechanical engineering applications, and even in calculating the orbits of satellites, because the deviation from such physics 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.

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Superseded biology theories

• Lamarckism challenged by Darwinian evolution, but revitalised in Neo-Lamarckism - see also epigenetic inheritance
• Maternal impression - rendered obsolete by genetic theory, but see fetal origins of adult disease
• Miasma theory of disease - rendered obsolete by germ theory of disease
• Spontaneous generation (commonly occurring abiogenesis) superseded by "Omne vivum ex ovo" (all life from the living)
• Recapitulation theory - or "ontogeny recapitulates phylogeny"

Superseded chemistry theories

• Classical elements - discredited by Ja'far al-Sadiq and Rhazes
• Caloric theory
• Phlogiston theory - replaced by Lavoisier's work on oxidation
• Part of Dalton's law
• Vital essence theory

Superseded physics theories

• Emission theory of vision - obsoleted by Ibn al-Haytham (Alhacen)
• Aristotelian theory of gravity - discredited by Muhammad ibn Musa, al-Biruni, al-Baghdadi and Galileo Galilei
• Aristotelian physics - discredited by Alhacen, al-Biruni, Avicenna, Avempace, al-Baghdadi, Galileo Galilei and Isaac Newton
• Ether - failed to be detected by 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
• Emitter theory - another now-obsolete theory of light propagation.
• Persistence of vision - is being debated by investigative psychologists.
• Progression of atomic theory

• Plum pudding model of the atom - assuming the protons and electrons were mixed together in a single mass
• Rutherford model of the atom with an impenetrable nucleus orbitted by electrons.
• Bohr model with quantized orbits
• Electron cloud model following the invention of Quantum Mechanics in 1925 and the eventual atomic orbital models derived from the quantum mechanical solution to the hydrogen atom.

Superseded astronomical and cosmological theories

• Ptolemaic system - obsoleted by Ibn al-Shatir and Copernicus
• Geocentric universe - obsoleted by Copernicus and Galileo
• Copernican system - obsoleted by Johannes Kepler and Isaac Newton
• Newtonian gravity - obsoleted by general relativity
• Luminiferous aether theory

Superseded geographical and climatological theories

• Flat Earth theory
• Hollow Earth theory
• The Open Polar Sea, an ice-free sea once supposed to surround the North Pole
• 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)

Superseded geological theories

• Continental drift was superseded by plate tectonics
• Expanding earth theory replaced by a statist model with Subduction
• Catastrophism was largely replaced by uniformitarianism

Superseded medical theories

• Theory of the four bodily humours - discredited by Rhazes, Avenzoar, Ibn al-Nafis, Ibn al-Lubudi and William Harvey
• Eclectic Medicine - Some say it transformed into homeopathy and pseudoscience.
• Physiognomy, related to phrenology, was the study of one's physical appearance in relation to one's inner character.

Obsolete branches of enquiry

• Alchemy, which led to the development of chemistry - alchemy was discredited by al-Kindi, al-Biruni, Avicenna and Ibn Khaldun
• Astrology, which led to the development of astronomy - astrology was discredited by al-Farabi, Alhacen, al-Biruni, Avicenna and Averroes
• 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.

• Steady State - replaced by an expanding universe model starting with the Big Bang. See also: dark matter.
• Atomic theory - Atoms are no longer thought to be indivisible, but are now seen to be composites.
• Nuclei disintegrate at high energy.
• Heliocentric universe theory - This is still used in the coordinate system of celestial mechanics.
• Newtonian mechanics - extended 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.
• Classical electrodynamics - approximation to quantum electrodynamics
• Bohr model of the atom - extended by the quantum mechanical model of the atom.
• 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

See also

• Science
• Philosophy of science
• Scientific theory
• Falsifiability - Karl Popper
• Paradigm shift
• Creation-evolution controversy

Lists

• List of pseudoscientific theories
• List of minority-opinion scientific theories
• List of discredited substances
• List of famous discoveries
• List of famous experiments