List of superseded scientific theories

A superseded, or obsolete, scientific theory is a scientific theory that was once commonly accepted but that is no longer considered the most complete description of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were only supported under specific political authorities, such as Lysenkoism, may also be described as obsolete or superseded.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.

Superseded theories

Biology

Spontaneous generation - is a principle regarding the origin of life from inanimate matter, which held that this process was a commonplace and everyday occurrence, as distinguished from univocal generation, or reproduction from parent(s). Rendered obsolete by Darwinism and abiogenesis.
Transmutation of species, Inheritance of acquired characteristics - first theories of evolution. Rendered obsolete by Darwinian evolution, Mendelian genetics and epigenetics; however, Lamarckism, or some elements of Lamarckian evolution are coming back in the area of epigenetics.
Mendelian genetics, Classical genetics, Boveri–Sutton chromosome theory - first genetical theories. They are part of molecular genetics now.
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". See Baer's laws of embryology.
Telegony (pregnancy) – the theory that an offspring can inherit characteristics from a previous mate of its mother's as well as its actual parents, often associated with racism.

Chemistry

Classical elements – discredited by Rhazes
Caloric theory
Phlogiston theory – replaced by Lavoisier's work on oxidation
Part of Dalton's law^{[clarification needed]}
Vital essence theory, discredited by Friedrich Wöhler

Physics

Emission theory of vision – discredited by Ibn al-Haytham (Alhacen)
Aristotelian physics – superseded by Newtonian physics
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 orbited by electrons.
Bohr model with quantized orbits
Electron cloud model following the development 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 – replaced by Nicolaus Copernicus' Heliocentric model.
Geocentric universe – obsoleted by Copernicus
Heliocentric universe
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 anomalous perihelion precession of Mercury was the first experimental evidence that Newtonian gravity was not totally accurate.
Luminiferous aether theory
Steady State Theory, a model developed by Hermann Bondi, Thomas Gold, and Fred Hoyle whereby the expanding universe was in a steady state, and had no beginning. It was a competitor of the Big Bang model until evidence supporting the Big Bang and falsifying the steady state was found.

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 and practically useful approximation to true distances and sizes, but departures from flatness 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

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

Psychology

Pure behaviorist explanations for language acquisition in infancy, falsified by the study of cognitive adaptations for language.^[1]
The blank slate theory of socialization, disproven by research on cross-cultural universals.^{[citation needed]}

Medicine

Theory of the four bodily humours
Eclectic Medicine – Transformed into alternative medicine, and although not disproved, and used extensively in the East, is not considered by some Western medical associations.
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
Astrology, which led to the development of astronomy
Phrenology, a pseudoscience
Numerology, 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.

Atomic theory initially proposed that atoms were indivisible, but now it is known that they are composed of subatomic particles.
Atomic nuclei disintegrate at high energy.
Newtonian mechanics was extended by the theory of relativity and by quantum mechanics. Relativistic corrections to Newtonian mechanics are unmeasurably small at velocities not approaching the speed of light, and quantum corrections are usually negligible at atomic or larger scales; Newtonian mechanics is totally satisfactory in engineering and physics under most circumstances.
Classical electrodynamics is a very close approximation to quantum electrodynamics except at very small scales and low field strengths.
Bohr model of the atom was extended by the quantum mechanical model of the atom.
The formula known as Newton's sine-square law of air resistance for the force of a fluid on a body, though not actually formulated by Newton but by others using a method of calculation used by Newton, has been found incorrect and not useful except for high-speed hypersonic flow. ^[2]

References

^ Crain, Stephen and Diane C. Lillo-Martin (1999). An Introduction to Linguistic Theory and Language Acquisition. Oxford: Blackwell.
^ Aerodynamics: Selected Topics in the Light of Their Historical Development,book by Theodore Von Karman, 1954, Dover Publications, p10 and following pages Detailed discussion of Newton's sine-square law, invalidity in the general case and applicability at high supersonic speeds.