Physics · Curated list
Schrödinger's cat, Twin paradox, Michelson–Morley experiment and 27 more, ranked by how much of the world has written about each one.
Most written-about first. Each description summarises the experiment's Wikipedia article, which its name links to.
1
Thought experiment in quantum mechanics
A thought experiment of quantum mechanics about quantum superposition. A hypothetical cat is shut in a box, its fate tied to a random subatomic event that might happen or might not; for as long as nobody looks, the cat can be regarded as alive and dead at once.
2
Thought experiment in special relativity
A thought experiment of special relativity about twins: one makes a space journey at relativistic speeds and comes home to find the twin who stayed on Earth has aged more. That seems puzzling, because each twin sees the other as the one moving, so a naive and mistaken use of the relativity principle and of time dilation suggests each should find the other has aged less, a paradox.
Wikidata · Photo: Kilian Kluge, CC BY-SA 3.0
3
1887 investigation of the speed of light
An attempt to measure how the Earth moves relative to the luminiferous aether, a medium once supposed to fill space and carry light waves. Albert A. Michelson and Edward W. Morley, both American physicists, carried it out between April and July 1887, in Cleveland, Ohio, at what is today Case Western Reserve University, and published it that November.
Wikidata · Photo: Case Western Reserve University, Public domain
4
Historical critique of quantum mechanics
Often shortened to EPR, a thought experiment arguing that quantum mechanics gives an incomplete description of physical reality, proposed by Albert Einstein with his fellow physicists Boris Podolsky and Nathan Rosen. Their 1935 paper, "Can Quantum-Mechanical Description of Physical Reality be Considered Complete?", argued that "elements of reality" exist outside quantum theory, and suggested that a theory containing these hidden variables could be built.
Wikidata · Photo: New York Times, Public domain
5
Thought experiment of 1867
A thought experiment that seems to violate the second law of thermodynamics. Its author was the physicist James Clerk Maxwell, who proposed it in 1867.
6
1922 physical experiment demonstrating that atomic spin is quantized
The quantum physics experiment that showed the spatial orientation of angular momentum to be quantised, and so demonstrated that a system on the atomic scale has properties that are quantum by nature.
Wikidata · Photo: BW8EJXH1nq, CC BY-SA 4.0
7
Physics experiment
A modern physics experiment showing that light and matter can behave in ways associated both with classical waves and with classical particles. Thomas Young first described an experiment of this kind in 1801, arguing that visible light behaves as a wave.
8
Experiment to measure elementary electric charge
An experiment to measure the elementary electric charge, carried out in 1909 by Harvey Fletcher and Robert A. Millikan in the Ryerson Physical Laboratory of the University of Chicago.
Wikidata · Photo: Unknown author, Public domain
9
Experiments proving existence of atomic nuclei
A landmark series of experiments showing that every atom has a nucleus, where most of its mass and all of its positive charge are concentrated. Scientists reached this conclusion by measuring how a beam of alpha particles scatters on striking a thin metal foil.
1914 confirmation of the atom's quantum nature
The first electrical measurement to show plainly that atoms are quantum in nature. James Franck and Gustav Hertz presented it in a paper to the German Physical Society on 24 April 1914.
11
CERN LHC experiment
Of all the general-purpose particle detector experiments at CERN's Large Hadron Collider (LHC), in Switzerland, the largest. It is built to exploit the LHC's unprecedented energy and to see phenomena involving very massive particles that older, lower-energy accelerators could not observe.
12
Experiment measuring the force of gravity (1797–1798)
An experiment by the English scientist Henry Cavendish in 1797–1798, the first to measure in a laboratory the force of gravity between masses and the first to give the gravitational constant accurately. The constant itself does not appear explicitly in his work, because of the unit conventions of his time.
Wikidata · Photo: GOKLuLe 盧樂, CC BY-SA 3.0
13
General-purposes experiment at the Large Hadron Collider
Usually shortened to CMS, one of the two big general-purpose detectors for particle physics on CERN's Large Hadron Collider (LHC), which lies in France and Switzerland. Its aim is to investigate physics broadly: it searches for the Higgs boson, for extra dimensions and for particles that might make up dark matter.
Wikidata · Photo: Julian Williams, Copyrighted free use
14
Detector experiment at CERN
A Large Ion Collider Experiment, known as ALICE, one of nine experiments with detectors on CERN's Large Hadron Collider (LHC). By measuring the properties of quark–gluon plasma, it studies the conditions believed to have existed in the moments right after the Big Bang.
15
Experiment measuring the speed of light in moving water
An experiment by Hippolyte Fizeau in 1851 measuring the relative speeds of light in water that is moving. Fizeau used an interferometer in a special arrangement to measure how a moving medium affects the speed of light.
Wikidata · Photo: Éleuthère Mascart, Public domain
Experiment verifying the wave-particle duality of matter
An experiment carried out at Western Electric by Clinton Davisson and Lester Germer between 1923 and 1927, in which electrons scattered off the surface of a nickel crystal produced a diffraction pattern.
17
Test of gravitational redshift
An experiment that tracked how the frequency of gamma rays shifted as they climbed and fell in Earth's gravitational field. It tested Albert Einstein's predictions of 1907 and 1911, based on the equivalence principle, that photons gain energy on the way down a gravitational potential and lose it on the way up.
Wikidata · Photo: Bostonian13, CC BY-SA 3.0
18
International cosmic ray observatory in Argentina
An international observatory in Argentina built to detect ultra-high-energy cosmic rays: subatomic particles moving at nearly the speed of light, each carrying more than 10¹⁸ eV. In Earth's atmosphere they collide with nuclei in the air and produce a variety of other particles.
Wikidata · Photo: Lorenzo Caccianiga, CC BY-SA 3.0
19
Underground laboratory in Ontario, Canada
Usually shortened to SNO, a neutrino observatory 2100 m below ground in the Creighton Mine, owned by Vale, at Sudbury in Ontario, Canada. Its detector was designed to pick up solar neutrinos as they interacted with a big tank of heavy water.
Wikidata · Photo: User:Boardhead, CC0
20
1644 physics experiment
An experiment devised in 1644, in Pisa, by the Italian scientist Evangelista Torricelli (1608-1647). It set out to show that what was called nature's "horror of the vacuum" in fact comes from atmospheric pressure.
1774 attempt to measure the Earth's average density
An 18th-century experiment to find the Earth's mean density. Paid for by a Royal Society grant, it took place in the summer of 1774 around Schiehallion, a Scottish mountain in Perthshire.
Physics experiment
A physics experiment measuring how inertial mass relates to gravitational mass, showing that the two are the same: long suspected, but never shown to the same accuracy. The first experiments of the kind were done by Isaac Newton (1642–1727), and Friedrich Wilhelm Bessel (1784–1846) improved on them.
Institute of Technology Experimental confirmation of neutrinos
The experiment that confirmed neutrinos exist, carried out in 1956 by two physicists, Frederick Reines and Clyde Cowan.
1999-2010 Japanese particle physics experiment
A particle physics experiment, running from 1999 to 2010, at KEK, the High Energy Accelerator Research Organisation, in Tsukuba, in Japan's Ibaraki Prefecture. It was run by the Belle Collaboration, an international group of more than 400 physicists and engineers.
26
Neutrino physics experiment in Italy
A particle physics experiment deep underground that studies solar neutrinos of low energy (sub-MeV). Its detector, the most radio-pure liquid scintillator calorimeter in the world, is shielded by the equivalent of 3,800 metres of water.
Wikidata · Photo: Borexino Collaboration, Public domain
1938 experiment confirming relativistic time dilation
A physics experiment testing how much relativistic time dilation contributes to the Doppler shift of light. Its result agreed with the transverse Doppler effect formula, and it was the first to confirm the time dilation factor directly and quantitatively.
1901–1903 physics experiment
An attempt to detect Earth's motion through the luminiferous aether, made in 1901–1903 by H. R. Noble and Frederick Thomas Trouton. It rested on George FitzGerald's suggestion that a charged parallel-plate capacitor travelling through the aether should turn to lie perpendicular to its motion.
A modified form (1925) of the Michelson–Morley experiment and of the Sagnac interferometer. By measuring the Sagnac effect caused by the Earth's rotation, it tests the theories of special relativity and of the luminiferous ether in Earth's rotating frame.
Long-baseline neutrino experiment in Japan
A particle physics experiment in Japan studying how accelerator neutrinos oscillate. It is run by an international collaboration of about 500 physicists and engineers from over 60 research institutions in several countries of Europe, Asia and North America, and is a recognised CERN experiment (RE13).
Every Wikidata item that is a physics experiment, and that has its own English Wikipedia article, ranked by the number of Wikimedia sites with a page about it — Wikipedia's language editions, mostly, and sister projects such as Wikiquote. That counts how many communities independently thought it worth describing, and nobody can buy a place on it. The top 30 are shown.
Wikidata files these under this list's query, but they are not what the list is about:
These belong on the list but Wikidata does not file them where the query looks:
Fetched from Wikidata on 2026-09-25. Each description is this site's summary of the entry's Wikipedia article, which its name links to: the wording is ours, the facts are Wikipedia's, licensed CC BY-SA 4.0. To correct an entry, correct it there; the next refresh carries the change.
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