Robert Boyle was the first person to hail an experiment as
experimentum crucis when he referred to the
famous mercury barometer experiment on Puy-de-Dome in 1648. This experiment settled the question: Was there some natural resistance to the creation of an apparently empty space at the top of the tube, or was the height of the mercury determined solely by the weight of the air? In his
Philosophiæ Naturalis Principia Mathematica,
Isaac Newton (1687) presents a disproof of
Descartes' vortex theory of the motion of the planets. In his
Opticks, Newton describes an optical
experimentum crucis in the
First Book, Part I, Proposition II, Theorem II, Experiment 6, to prove that sunlight consists of rays that differ in their
index of refraction. bedroom. Acrylic painting by Sascha Grusche (17 Dec 2015) A 19th-century example was the prediction by
Poisson, based on
Fresnel's mathematical analysis, that the
wave theory of light predicted a bright spot in the center of the shadow of a perfectly circular object, a result that could not be explained by the (then current) particle theory of light. An experiment by
François Arago showed the existence of this effect, now called the
Arago spot, or "Poisson's bright spot", which led to the acceptance of the wave theory. A famous example in the 20th century of an
experimentum crucis was the expedition led by
Arthur Eddington to
Principe Island in
Africa in 1919 to record the positions of stars around the
Sun during a
solar eclipse (see
Eddington experiment). The observation of star positions confirmed predictions of
gravitational lensing made by
Albert Einstein in the
general theory of relativity published in 1915. Eddington's observations were considered to be the first solid evidence in favor of Einstein's theory. In some cases, a proposed theory can account for existing anomalous experimental results for which no other existing theory can furnish an explanation. An example would be the ability of the
quantum hypothesis, proposed by
Max Planck in 1900, to account for the observed
black-body spectrum, an experimental result that the existing
classical Rayleigh–Jeans law could not predict. Such cases are not considered strong enough to fully establish a new theory, however, and in the case of quantum mechanics, it took the confirmation of the theory through
new predictions for the theory to gain full acceptance.
DNA, experimentum crucis :
See §Context for crucial experiment in the discovery of the §structure of DNA, and §List of experiments in biology In
the discovery of the significance of the structure of DNA, the fact that DNA was a double helix enabled the discoverers, Francis Crick and James Watson, to suggest that one strand of the double helix could serve as the template for the second strand, as the second strand was being duplicated. This explained the
secret of life, how the structure of DNA could serve as the
mechanism for the
gene (the
genetic code), in which four
nucleotides serve to encode the sequence of
enzymes needed
to catalyze the production of macromolecules in the cell, and which led to its application in
synthetic biology, in
genetic engineering, in
forensics,
genetic testing,
genomics and
pharmaceuticals, among other industries.
Tanis fossil site In the 21st century, the discovery of the
Tanis fossil site, a killing field in the
Hell Creek formation of North Dakota, proved that the
K-T boundary (now known as the KPg, or the
Cretaceous–Paleogene extinction event) as cited in
Science Daily. Based on the dating of the Tanis, the event occurred 65.76 million years ago (± 0.15 My). An early indicator of a theory of Experimentum Crucis appears in
John Locke's
Doctrine of Abstraction. Lorne Falkenstein, reviewing Van Cleve expands the discussion of Experimentum crucis to the more general philosophical realm of
Property dualism. ==See also ==