The following is a list of historically important scientific
experiments and observations demonstrating something of great scientific interest, typically in an elegant or clever manner.
James Lind, publishes 'A Treatise of the Scurvy' which describes a controlled shipboard experiment using two identical populations but with only one variable, the consumption of citrus fruit (1753).
Edward Jenner tests his hypothesis for the protective action of mild cowpox infection for
smallpox, the first
vaccine (1796).
Charles Darwin and his son
Francis, using dark-grown oat seedlings, discover the stimulus for
phototropism is detected at the tip of the shoot (the
coleoptile tip), but the bending takes place in the region below the tip (1880).
Alexander Fleming demonstrates that the zone of inhibition around a growth of
penicillin mould on a culture dish of bacteria is caused by a diffusible substance secreted by the mould (1928).
Luria–Delbrück experiment demonstrates that in bacteria, beneficial mutations arise in the absence of selection, rather than being a response to selection (1943).
Herbert Boyer and
Stanley Cohen selectively clone genes in bacteria, using bacterial plasmids cut by specific endonucleases (1975).
Mary-Dell Chilton shows that crown gall tumors of plants are caused by the transfer of a small piece of DNA from the bacterium Agrobacterium tumefaciens into the host plant, where it becomes part of its genome (1977).
Napoli, Lemieux and Jorgensen discover the principle of
RNA interference (1990).
Chemistry
Blaise Pascal carries a
barometer up a church tower and a mountain to determine that atmospheric pressure is due to a column of air (1648).
Erwin Chargaff disproves the "tetranucleoide theory" of
DNA structure and determines that the composition of double-stranded DNA follows the rule, %A = %T and %G = %C (
Chargaff's rule). This discovery was critical to the formulation of the Watson-Crick Model of DNA structure.
Charles Mason conducts an experiment near the Scottish mountain of
Schiehallion that attempts to measure the mean density of the Earth for the first time. Known as the
Schiehallion experiment (1774)
Discovery of electromagnetic induction (1831):
Michael Faraday discovers
magnetic induction in an experiment with a closed ring of soft iron, with two windings of wire.
Doppler experiment (1845):
Christian Doppler arranges to have trumpets played from a passing
train. The ground-observed pitch was higher than that played when the train was approaching then lower than that played as the train passed and moved away, demonstrating the
Doppler effect.
Thomson's experiments with
cathode rays (1897):
J. J. Thomson's cathode ray tube experiments (discovers the
electron and its negative charge).
Eötvös experiment (1909):
Loránd Eötvös publishes the result of the second series of experiments, clearly demonstrating that inertial and gravitational mass are one and the same.
Rosenhan experiment (1972). It involved the use of healthy associates or "pseudopatients", who briefly simulated auditory hallucinations in an attempt to gain admission to 12 different psychiatric hospitals. The hospital staff failed to detect a single pseudopatient. The study is considered an important and influential criticism of psychiatric diagnosis.
Kansas City preventive patrol experiment (1972–1973) It was designed to test the assumption that the presence (or potential presence) of police officers in marked cars reduced the likelihood of a crime being committed. No relationship was found.
Benjamin Libet's experiment on free will shows that a readiness potential appears before the notion of doing the task enters conscious experience, sparking debate about the illusory nature of free will yet again. (1983)
Vilayanur S. Ramachandran's experiment on phantom limbs with the Mirror Box throw light on the nature of 'learned paralysis' (1998)