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

A superseded, or obsolete, scientific theory is a scientific theory that was once commonly accepted, but that is no longer considered the most complete description of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which were only supported under specific political authorities, like Lysenkoism, may also be described as obsolete or superseded.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, it was originally a profound insight by primitive people who lived in a landscape with hills, rivers, and valleys; viewing a landscape as flat it 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.

Superseded biology theories

Giraffes are often invoked in explanations of Lamarck's superseded theory of evolution.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 subsequently have an offspring with a longer neck. The theory has been superseded by the understanding of natural selection as the primary mechanism of evolution.

• 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 superseded by "biogenesis" and "abiogenesis".
• 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.
• 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 - 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 ether - 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
• Emitter theory - another now-obsolete theory of light propagation.
• Persistence of vision - is being debated by investigative psychologists.^{citation needed}
• 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.

Superseded astronomical and cosmological theories

• 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 at velocities much lower than the velocity of light
• Cosmic ice theory

Superseded geographical and climatological theories

• 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)

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 economic theories

• Rational actor theory, superseded by prospect theory and the study of heuristics

Superseded psychological theories

• 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

Superseded medical theories

• 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 approximations

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 the standard tool in engineering and physics at atomic or larger scales and velocities not approaching the speed of light.
• 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
• Pathological science

Lists

• List of pseudoscientific theories
• List of discredited substances
• List of famous discoveries
• List of famous experiments

Wikipedia content modification information:

• This page was last modified on 6 October 2008, at 04:23.

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