Superseded theories in science and results in mathematics: Difference between revisions

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A superseded, or obsolete, scientific theory is a scientific theory that was once commonly accepted, but that is no longer considered the most complete description of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 falsifiable 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which were only supported under specific political authorities, like Lysenkoism, may also be described as obsolete or superseded.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 elements of the earlier theory; in these cases, the older theory is often still useful because it provides a description that is "good enough" for many purposes, is more easily understood than the complete theory, and may 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. Newtonian physics is so satisfactory for most purposes that many secondary educational systems teach it, but not the "correct" relativity. Another case is the theory that the earth is approximately flat; while clearly wrong for long distances, viewing a landscape as flat is still sufficient for most local maps 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.

The obsolete Geocentric model of the universe places the Earth at the centre.

Superseded theories

Biology

Giraffes are often invoked in explanations of Lamarck's superseded theory of evolution. In Lamarckism, a giraffe is able to lengthen its neck over its life time, for example by stretching to reach higher leaves, and have offspring inheriting the longer neck.

Lamarckism – the theory that non-germline changes are inheritable. Rendered obsolete by Darwinian evolution (see also Neo-Lamarckism, epigenetic inheritance)
Maternal impression – the theory that the mother's thoughts created birth defects. Rendered obsolete by genetic theory (see also fetal origins of adult disease, genomic imprinting)
Miasma theory of disease – the theory that diseases are caused by "bad air". Rendered obsolete by the germ theory of disease.
Preformationism – the theory that all organisms have existed since the beginning of life, and that gametes contain a miniature but complete preformed individual. Rendered obsolete by cytology, discovery of DNA and Atomic theory.
Recapitulation theory – the theory that "ontogeny recapitulates phylogeny". Always obsolete; see Baer's laws of embryology.
Spontaneous generation – the theory that life spontaneously emerged from dead matter today. Rendered obsolete by abiogenesis/biogenesis.
Telegony (pregnancy) – the theory that an offspring can inherit characteristics from a previous mate of its mother's as well as its actual parents; a theory often associated with racism. Always obsolete; see heredity.

Chemistry

Classical elements - discredited by Rhazes
Caloric theory
Phlogiston theory - replaced by Lavoisier's work on oxidation
Part of Dalton's law
Vital essence theory

Physics

Emission theory of vision - discredited 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
Luminiferous aether - failed to be detected by the sufficiently sensitive Michelson-Morley experiment, made obsolete by Einstein's work.
Caloric theory - Lavoisier's successor to phlogiston, discredited by Rumford's and Joule's work
Vis viva - Gottfried Leibniz's elementary and limited early formulation of the principle of conservation of energy
"Purely electrostatic" theories of the generation of voltage differences.
Emitter theory - another now-obsolete theory of light propagation.
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.

All of classical physics, while useful in practice, is in principle superseded by relativistic physics and quantum physics, to which classical physics is often a close approximation.

Astronomy and cosmology

Ptolemaic system - obsoleted by Ibn al-Shatir^{[citation needed]} and Copernicus
Geocentric universe - obsoleted by Copernicus and Galileo
Copernican system - obsoleted by Johannes Kepler and Isaac Newton
Newtonian gravity - superseded by general relativity, to which it is an excellent approximation unless the masses involved are very large or the distances very small. The Perihelion precession of Mercury was the first experimental evidence against Newtonian gravity; it also fails to describe black holes correctly.
Ether theory

Geography and climate

Flat Earth theory. On length scales much smaller than the radius of the Earth, a flat map projection gives a quite accurate approximation to true distances and sizes, but distortions become increasingly significant over larger distances.
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)

Geology

Continental drift was superseded by plate tectonics
Expanding Earth theory was superseded by subduction
Catastrophism was largely replaced by uniformitarianism

Psychology

The Freudian unconscious, superseded by a variety of more specific and predictive theories
Pure behaviorist explanations for language acquisition in infancy, superseded by the study of cognitive adaptations for language.
The blank slate theory of socialization, disproven by research on cross-cultural universals and evolutionary psychology
Persistence of vision - is being debated by investigative psychologists.^{[citation needed]}

Medicine

Theory of the four bodily humours - discredited by Rhazes, Avenzoar, Ibn al-Nafis, Ibn al-Lubudi and William Harvey
Eclectic Medicine - Transformed into alternative medicine.
Physiognomy, related to phrenology, held that inner character was strongly correlated with physical appearance.

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 is considered a pseudoscience
Numerology (as distinct from number theory) is considered a pseudoscience

Theories now considered to be incomplete

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

Steady State was replaced by an expanding universe model starting with the Big Bang. See also: dark matter.
Atomic theory initially proposed that Atoms were indivisible, but now it is known that they are composed of subatomic particles.
Nuclei disintegrate at high energy.
Heliocentric universe theory is still used in the coordinate system of celestial mechanics.
Newtonian mechanics was extended by Theory of Relativity and quantum mechanics. It is still the standard tool in engineering and physics at atomic or larger scales and velocities not approaching the speed of light.
Classical electrodynamics approximates quantum electrodynamics.
Bohr model of the atom was extended by the quantum mechanical model of the atom.
Newton's sine-square law for the force of a fluid on a body is no longer considered useful at low speeds, though it has found application in hypersonic flow.

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 * [[Maternal impression]] &ndash; the theory that the mother's thoughts created [[birth defects]]. Rendered obsolete by [[genetics|genetic theory]] (see also [[fetal origins of adult disease]], [[genomic imprinting]])
 * [[Miasma theory of disease]] &ndash; the theory that diseases are caused by "bad air". Rendered obsolete by the [[germ theory of disease]].
-* [[Preformationism]] &ndash; the theory that all organisms have existed since the beginning of life, and that [[gamete]]s contain a miniature but complete preformed individual. Rendered obsolete by [[cytology]] and the discovery of [[DNA]].
+* [[Preformationism]] &ndash; the theory that all organisms have existed since the beginning of life, and that [[gamete]]s contain a miniature but complete preformed individual. Rendered obsolete by [[cytology]], discovery of [[DNA]] and [[Atomic theory]].
 * [[Recapitulation theory]] &ndash; the theory that "ontogeny recapitulates phylogeny". Always obsolete; see [[Baer's laws of embryology]].
 * [[Spontaneous generation]] &ndash; the theory that life spontaneously emerged from dead matter today. Rendered obsolete by [[abiogenesis]]/[[biogenesis]].