Obsolete scientific theories

These are theories that were once commonly accepted but (for whatever reason) are no longer considered the most complete description of reality; or falsifiable theories which have been shown to be false. This 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.)

Obsolete biology theories

• Lamarckism - but revitalised in Neo-Lamarckism
• 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 a particular domain

• 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, still used in engineering and in physics at middling (human) scales
• Bohr model of the atom - allows for exact solution of the Hydrogen atom, but larger atoms are not well served
• 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.

See also

• Science - Philosophy of science - Scientific theory
• Falsifiability - Karl Popper
• Obsolete theory
• Quackery

Lists

• List of famous experiments
• List of famous discoveries
• List of alternative, speculative and disputed theories