Superseded theories in science
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In science, a theory is superseded when a scientific consensus once widely accepted it, but current science considers it inadequate, incomplete, or debunked (i.e., wrong). Such labels do not cover protoscientific or fringe science theories that have never had broad support within the scientific community. Furthermore, superseded or obsolete theories exclude theories that were never widely accepted by the scientific community. Some theories that were only supported under specific political authorities, such as Lysenkoism, may also be described as obsolete or superseded.
Some theories have been discovered to be incomplete or not hold precisely, but remain in use as practical approximations. For example, all of Newtonian physics is satisfactory for most purposes, and so is widely used except at velocities that are a significant fraction of the speed of light. It is also simpler than relativistic mechanics and so is usually taught in schools. Another case is the belief that the Earth is approximately flat. For centuries, people have known that a flat Earth model produces errors in long-distance calculations, but considering local-scale areas as flat for the purposes of mapping and surveying does not introduce significant errors.
In some cases, a theory or idea is found 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 that 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 that is negligibly small at velocities much lower than that of light.
Scientific theories are testable and make falsifiable predictions. Thus, it is a mark of good science if a discipline has a growing list of superseded theories, and conversely, a lack of superseded theories can indicate problems in following the use of the scientific method.
- Spontaneous generation – a principle regarding the spontaneous generation of complex 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). Falsified by an experiment by Louis Pasteur: where apparently spontaneous generation of microorganisms occurred, it did not happen on repeating the process without access to unfiltered air; on then opening the apparatus to the atmosphere, bacterial growth started.
- Transmutation of species, Lamarckism, inheritance of acquired characteristics, Lysenkoism – first theories of evolution. Not supported by experiment, and rendered obsolete by Darwinian evolution and Mendelian genetics, though some elements of Lamarckian evolution are coming back in the area of epigenetics (on a very limited scale).
- Vitalism – the theory that living things are alive because of some "vital force" independent of matter, as opposed to because of some appropriate assembly of matter. It was gradually discredited by the rise of organic chemistry, biochemistry, and molecular biology, fields that failed to discover any "vital force". Friedrich Wöhler's synthesis of urea from ammonium cyanate was only one step in a long road, not a great refutation.
- Maternal impression – the theory that the mother's thoughts created birth defects. No experimental support (a notion rather than a theory), and rendered obsolete by genetic theory (see also fetal origins of adult disease, genomic imprinting)
- Preformationism – the theory that all organisms have existed since the beginning of life, and that gametes contain a miniature but complete preformed individual, in the case of humans, a homunculus. No support when microscopy became available. 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 – 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.
- Out of Asia theory of human origin – The majority view is of a recent African origin of modern humans, although a multiregional origin of modern humans hypothesis has much support (which incorporates past evidence of Asian origins)
- Scientific racism – the theory that humanity consists of physically discrete superior or inferior races. Rendered obsolete by Human evolutionary genetics and modern anthropology.
- Mendelian genetics, classical genetics, Boveri–Sutton chromosome theory – first genetic theories. Not invalidated as such, but subsumed into molecular genetics.
- Germ line theory, explained immunoglobulin diversity by proposing that each antibody was encoded in a separate germline gene.
- Caloric theory – the theory that a self-repelling fluid called "caloric" was the substance of heat. Rendered obsolete by the mechanical theory of heat.
- Classical elements – All matter was once thought composed of various combinations of classical elements (most famously air, earth, fire, and water). Antoine Lavoisier finally refuted this in his 1789 publication, Elements of Chemistry, which contained the first modern list of chemical elements.
- Phlogiston theory – The theory that combustible goods contain a substance called "phlogiston" that entered air during combustion. Replaced by Lavoisier's work on oxidation
- Point 2 of Dalton's Atomic Theory was rendered obsolete by discovery of isotopes, and point 3 by discovery of subatomic particles and nuclear reactions.
- Vitalism – See section on biology.
- Nascent state refers to the form of a chemical element (or sometimes compound) in the instance of their liberation or formation. Often encountered are atomic oxygen (Onasc) and nascent hydrogen (Hnasc), and chlorine (Clnasc) or bromine (Brnasc).
- Emission theory of vision – the belief that vision is caused by rays emanating from the eyes was superseded by the intro-mission approach and more complex theories of vision
- Aristotelian physics – superseded by Newtonian physics
- Ptolemy's law of refraction, replaced by Snell's law
- 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
- Contact tension – a theory on the source of electricity
- 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
- Balance of nature – superseded by catastrophe theory and chaos theory
- Progression of atomic theory
- Democritus, the originator of atomic theory, held that everything is composed of atoms that are indestructible. His claim that atoms are indestructible is not the reason it is superseded—as it was later scientists who identified the concept of atoms with particles, which later science showed are destructible. Democritus' theory is superseded because of his position that several kinds of atoms explain pure materials like water or iron, and characteristics that science now identifies with molecules rather than with indestructible primary particles. Democritus also held that between atoms, an empty space of a different nature than atoms allowed atoms to move. This view on space and matter persisted until Einstein described spacetime as being relative and connected to matter.
- John Dalton's model of the atom, which held that atoms are indivisible and indestructible (superseded by nuclear physics) and that all atoms of a given element are identical in mass (superseded by discovery of atomic isotopes).
- 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, including Newtonian physics, superseded by relativistic physics and quantum physics. However, classical physics is a limiting case of the latter two theories, and it is often a very good approximation.
Astronomy and cosmology
- Ptolemaic system – replaced by Nicolaus Copernicus' heliocentric model.
- Geocentric universe – made obsolete by Copernicus
- Heliocentric universe – made obsolete by discovery of the structure of the Milky Way and the red shift of most galaxies. Heliocentrism only applies to the selected Solar System, and only approximately, since the Sun's center is not at the Solar System's center of mass.
- Copernican system – made obsolete by Johannes Kepler and Isaac Newton
- Newtonian gravity – superseded by general relativity, to which it is a good approximation unless typical speeds approach that of light in a vacuum (c). The anomalous perihelion precession of Mercury was the first observational 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.
- Many planets and other objects were once thought to exist but are now known not to – see List of hypothetical Solar System objects
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.
- Terra Australis
- 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)
- Island of California – the theory that California was not part of mainland North America but rather a large island
- Inland sea of Australia
- Pre-Modern Environmental determinism (as explanations for moral behavior, as opposed to modern theories such as factor endowments, state formation, and theories of the social effects of global warming)
- Climatic determinism
- Topographic determinism
- Moral geography
- Cultural Acclimatization
- Abiogenic petroleum origin
- Catastrophism was largely replaced by uniformitarianism and neocatastrophism
- Cryptoexplosion craters, now discarded in favour of impact craters and ordinary volcanism.
- Flood geology replaced by modern geology and stratigraphy
- Neptunism replaced by plutonism and volcanism
- Granitization a discredited alternative to a magmatic origin of granites
- Oscillation theory of land-level rise and subsidence during deglaciation
- The following were superseded by plate tectonics:
- Pure behaviorist explanations for language acquisition in infancy, falsified by the study of cognitive adaptations for language.
- Psychomotor patterning, a pseudoscientific approach to the treatment of intellectual disabilities, brain injury, learning disabilities, and other cognitive diseases.
- Theory of the four bodily humours (see also Four temperaments)
- Heroic medicine – a therapeutic method derived from the belief in bodily humour imbalances as the cause of ailments.
- Miasma theory of disease – the theory that diseases are caused by "bad air". No experimental support, and rendered obsolete by the germ theory of disease.
- Phrenology – a theory of highly localised brain function popular in 19th century medicine.
- Homeopathy – a theory according to which a disease can be cured by infinitesimal doses of the substance that caused it
- Eclectic medicine – Transformed into alternative medicine, and is no longer considered a scientific theory
- Physiognomy, related to phrenology, held that inner character was strongly correlated with physical appearance
- Tooth worm, an erroneous theory of the cause of dental caries, periodontitis, and toothaches
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 incomplete
These theories that are no longer considered the most complete representation of reality but remain useful in particular domains or under certain conditions. For some theories, a more complete model is known, but for practical use, the coarser approximation provides good results with much less calculation.
- Newtonian mechanics was extended by the theory of relativity and by quantum mechanics. Relativistic corrections to Newtonian mechanics are immeasurably 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.
- The once-popular cycle of erosion is now considered one of many possibilities for landscape evolution.
- The theory of continental drift was incorporated into and improved upon by plate tectonics.
- Scientific theory
- Philosophy of science
- Fringe science
- Pathological science
- Paradigm shift
- History of evolutionary thought
- Creation–evolution controversy
- List of discredited substances
- List of famous experiments
- List of topics characterized as pseudoscience
- Popper, Karl (1963), Conjectures and Refutations, Routledge and Kegan Paul, London, UK. Reprinted in Theodore Schick (ed., 2000), Readings in the Philosophy of Science, Mayfield Publishing Company, Mountain View, Calif.
- Executive Board of the American Anthropological Association. "scientific racism". AAA Statement on Race. American Anthropological Association. Retrieved 15 December 2018.CS1 maint: uses authors parameter (link)
- "germline theory". Glossary. NCBI.
- Lefers, Mark. "germ-line theory". Glossary. Northwestern University. Retrieved 28 February 2012.
- Jensen, William B (1990). "Whatever Happened to the Nascent State?" (PDF). Bulletin for the History of Chemistry (5): 26–36. Retrieved 6 May 2017.
- De Leon, Professor N. "Dalton's Atomic Theory". Chemistry 101 Class Notes. Indiana University Northwest. Retrieved 26 August 2013.
- Cathcart, Michael (2009). The Water Dreamers: How Water and Silence Shaped Australia. Melbourne: Text Publishing. chapter 7. ISBN 9781921520648.
- An inland sea, the Eromanga Sea, did exist there in the Mesozoic, but not during any period of human history
- Crain, Stephen and Diane C. Lillo-Martin (1999). An Introduction to Linguistic Theory and Language Acquisition. Oxford: Blackwell.
- Steven Novella, MD. "Psychomotor Patterning". Retrieved October 16, 2014.
- Hassani, Sadri (2010). From Atoms to Galaxies: A Conceptual Physics Approach to Scientific Awareness (illustrated ed.). CRC Press. p. 387. ISBN 978-1-4398-8284-9. Extract of page 387
- Casimir, H. B. G.; Brugt, Hendrik; Casimir, Gerhard (2010). Haphazard Reality: Half a Century of Science. Amsterdam University Press. p. 32. ISBN 978-90-8964-200-4. Extract of page 32
- 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.
- Orme, Anthony R. (2007). "The Rise and Fall of the Davisian Cycle of Erosion: Prelude, Fugue, Coda, and Sequel". Physical Geography. 28 (6): 474–506. doi:10.2747/0272-36220.127.116.114. S2CID 128907423.
- Media related to Obsolete scientific theories at Wikimedia Commons