Obsolete scientific theory

An 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; 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.

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 usable.)

Table of contents

1 Obsolete biology theories
2 Obsolete chemistry theories
3 Obsolete physics theories
4 Obsolete medical theories
5 Obsolete branches of enquiry
6 Approximate theories
7 Theories whose significance was overstated
8 See also

Obsolete biology theories

Lamarckism - but revitalised in Neo-Lamarckism - see also Epigenetic inheritance
Intelligent Design theory - obsoleted by Darwinism, now revived by a few
Weismann Barrier - generally accepted, contested by a few
Miasma theory of disease - obsoleted by germ theory of disease
Spontaneous generation (or abiogenesis)

Obsolete chemistry theories

Caloric theory
Phlogiston theory - replaced by Lavoisier's work on oxidation

Obsolete physics theories

Flat earth theory
Aristotelian theory of gravity - discredited by Galileo
Aether
Heliocentric universe and the Copernician model - obsoleted by Johannes Kepler and Isaac Newton
N-rays
Plum pudding model of the atom - assuming the protons and electrons were mixed together in a single mass.

Obsolete medical theories

Theory of the four bodily humours
Eclecticism (medicine) - medical history - some say it transformed into homeopathy and pseudoscience

Obsolete branches of enquiry

Alchemy, which led to the development of chemistry
Astrology, which led to the development of astronomy
Phrenology, was once widely studied but now considered a pseudoscience
Numerology, developed into number theory, but now considered a pseudoscience

Approximate theories

Here are theories that are no longer considered a complete representation of reality, but are still used in particular domains. For many theories a more complete model is known, but in practical use the courser approximation provides good results with much less calculation.

Static universe - the Big Bang and dark matter threaten to destroy this comfortable world picture
Universe - the world is all that is the case (Tractatus Logico-Philosophicus). The possibility of Multiverses is one of the consequences of Cosmic inflation
Atoms are no longer thought to be indivisible, but are now seen to be composites
Nuclei disintegrate at high energy
isochronous time - if there was a Big Bang, then time did not exist before the first time step; but we use clocks everyday.
Geocentric universe theory - this is still used in the coordinate system of Celestial mechanics
Newtonian mechanics - obsoleted by Theory of Relativity and Quantum mechanics. Still useful in engineering and physics at either middling (human) scales or where apreciable fractions of the speed of light need not be considered.
Bohr model of the atom - allows for exact solution of the Hydrogen atom, but larger atoms are not well described
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

Theories whose significance was overstated

Land bridges - Though temporary connections between land masses sometimes allowed migrations (as when sea levels were lowered during ice ages), the actual splitting of continents by plate tectonics has been more important.