|-260||Greece||Archimedes discovers the principle of buoyance, leading to the concept of specific gravity.|
|1025||Arabia||Alhazen's Opticae Thesaurus discusses the properties of lenses, the nature of refraction and reflection, and correctly states that the object seen is the source of light rays.|
|1269||France||Peter Peregrinus' Epistola de Magnete identifies magnetic poles, also representing an early, unsophisticated use of the experimental method.|
|1583||Italy||Galileo discovers that a pendulum's period of oscillation is independent of its amplitude.|
|1583||Netherlands||Simon Stevin introduces the theory of static equilibrium, founding hydrostatics.|
|1586||Netherlands||Simon Stevin presents evidence that falling bodies fall at the same rate.|
|1589||Italy||Galileo's tests of falling bodies represent a landmark use of experimental data.|
|1592||Italy||Galileo invents the thermometer (precisely, barothermometer).|
|1600||England||William Gilbert's De Magnete, Magnetisque Corporibus, et de Magno Magnete Tellure describes the magnetic properties of the earth and founds the scientific study of electricity.|
|1604||Italy||Galileo discovers that a free-falling body increases its distance as the square of the time, a pioneering mathematization of a physical phenomenon.|
|1609||Netherlands||Zacharias Jansen and Hans Lippershey invent the compound microscope.|
|1621||Netherlands||Willebrord Snell discovers Snell's Law for computing the refraction of light, later discovered independently by Descartes.|
|1638||Italy||Galileo's Discoursi e Dimostrazioni Matematiche, Intorno à Due Nuove Scienze founds modern mechanics.
||1643||Italy||Evangelista Torricelli invents the barometer in the process of discovering air pressure, and creates the first (near) vacuum known to science.
||1645||Germany||Otto von Guericke discovers that, in a vacuum, sound does not travel, fire is extinguished, and animals stop breathing.
||1648||France||Blaise Pascal states Pascal's principle, that pressure on an enclosed fluid is transmitted without reduction throughout the fluid, founding hydraulics.
||1650||Germany||Otto von Guericke demonstrates the force of air pressure, using teams of horses to try to pull apart metal hemispheres held together by a partial vacuum.
||1665||England||Robert Hooke's Micrographia introduces the first major challenge to the concept of light as a stream of particles, arguing instead that light is a vibration.
||1665||Italy||Francesco Grimaldi gives the first major account of light diffraction and interference.
||1669||Denmark||Erasmus Bartholin describes double refraction, the apparent doubling of images when seen through a crystal.
||1670||Netherlands||Christiaan Huygens develops a wave theory of light, published in 1690
||1672||England||Isaac Newton describes the light spectrum, and discovers that white light is made from a mixture of colors.
||1675||France||Ole Rømer deduces that light has a speed and calculates an approximation of it (put at 141,000 miles per second).
||1687||England||Isaac Newton's Philosophiae Naturalis Principia Mathematica states the law of universial gravitation, and the laws of motion, and predicts that the shape of the earth is nonspherical, based on the finding that gravity at Cayenne is less than that a Paris.
||1701||France||Joseph Sauveur describes the production of tones by the vibration of strings and coins the word acoustic.
||1704||England||Isaac Newton's Opticks: A Treatise of the Reflections, Refractions, Inflections, and Colours of Light discusses optical phenomena, including the suggestion that light is particulate in nature.
||1714||Netherlands||Daniel Fahrenheit invents the Fahrenheit scale, and the mercury thermometer, the first accurate thermometer.
||1728||England||James Bradley discovers the aberration of starlight, leading to a better measure of the speed of light and providing evidence for a heliocentric solar system.
||1733||France||Charles DuFay discovers that there are two types of static electric charges and that like charges repel each other while unlike charges attract, linking electricity to magnetism.
||1738||Switzerland||Daniel Bernoulli's Hydrodynamica states Bernoulli's Principle and founds the mathematical study of fluid flow and the kinetic theory of gases.
||1742||Sweden||Anders Celsius invents the Celsius scale.
|Ewald von Kleist and Pieter van Musschenbroek independently invent a practical device for storing an electric charge, the Leyden jar.
||1748||France||Jean Nollet discovers osmosis, the passage of a solution through a semi-permeable membrane separating two solutions with different concentrations.
||1752||USA||Benjamin Franklin discovers that lightning is a form of electricity.
||1762||Scotland||Joseph Black develops the concept of latent heat, the quantity of heat absorbed or released when a substance changes its physical phase at constant temperature.
||1787||France||Jacques Charles demonstrates that different gases expand by the same amount for a given rise in temperature, known both as Charles' law and Gay-Lussac's law (Joseph Gay-Lussac is the first to publish, in 1802. The relationship was first stated a century earlier by Guillaume Amontons, then forgotten).
||1798||England||Henry Cavendish and Nevil Maskelyne measure the gravitational constant, leading to an accurate estimate of the mass of the earth.
||1798||Germany||Benjamin Thompson (Count Rumford) demonstrates that heat is a form of motion (energy) rather than a substance.
||1800||England||William Herschel discovers infrared radiation, and that invisible light beyond the red produces the most heat.
||1801||England||Thomas Young uses diffraction and interference patterns to demonstrate that light has wavelike characteristics.
||1808||France||Étienne Malus discovers the polarization of light.
||1815||France||Jean Biot discovers that the plane of polarized light is twisted in different directions by different organic liquids.
||1818||France||Augustin Fresnel's Mémoire sur la Diffraction de la Lumière demonstrates the ability of a transverse wave theory of light to account for a variety of optical phenomena, converting many scientists to a wave theory.
||1820||Denmark||Hans Ørsted emonstrates that electricity and magnetism are related, jointly (with Ampère) founding the science of electrodynamics.
||1820||Germany||Johann Schweigger invents the needle galvanometer, later essential for the telegraph.
||1821||England||Michael Faraday's "On Some New Electromagnetic Motions" reports his discovery that electrical forces can produce motion and describes the principle of the electric motor.
||1822||France||Jean Fourier's Théorie Analytique de la Chaleur applies Fourier's theorem to the study of heat flow, an influential application of mathematics to physical phenomena.
||1822||Germany||Thomas Seebeck discovers that two different metals will generate electricity if their points of juncture are maintained at different temperatures, the Seebeck effect, and demonstrates thermoelectricity.
||1823||England||William Sturgeon invents the electromagnet.
||1824||France||Nicolas Carnot's Réflexions sur la Puissance Motrice du Feu is the first scientific analysis of steam engine efficiency, founding thermodynamics.
||1827||France||Andre Ampère publishes Ampere's Law, a mathematical expression of Ørsted's relationship between magnetism and electricity.
||1827||Germany||George Ohm publishes Ohm's Law, that an electrical current is equal to the ratio of the voltage to the resistance, a founding event in electrical engineering.
||1827||Scotland||Robert Brown discovers continuous random movement of microscopic solid particles when suspended in a fluid, later known as Brownian motion.
||1829||Scotland||William Nicol invents the Nicol prism for measuring the degree of twist in a plane of polarized lead, founding polarimetry.
||1829||USA||Joseph Henry uses insulated wire to create an electromagnet able to lift a ton of iron.
|Michael Faraday and Joseph Henry independently discover that a changing magnetic force can generate electricity, the phenomenon of electromagnetic induction.
||1832||England||Michael Faraday discovers the basic laws of electrolysis that govern the production of a chemical reaction by passing electric current through a liquid or solution.
||1834||France||Jean Peltier discovers the Peltier effect, that a current flowing across a junction of two dissimilar metals causes heat to be absorbed or freed, depending on the direction in which the current is flowing.
||1839||France||Alexandre Becquerel discovers the photovoltaic effect, whereby light can be used to induce chemical reactions that produce an electric current.
||1842||Germany||Christian Doppler discovers the Doppler effect, that the frequency of waves emitted by a moving source changes when the source moves relative to the observer.
||1842||Germany||Julius von Mayer and Carl Mohr develop early formulations of the concept of conservation of energy.
||1843||England||James Joule discovers Joule's first law, describing the heat produced hwen an electric current flows through resistance for a given time.
||1847||Germany||Hermann von Hemholtz states the law of conservation of energy, the first law of thermodynamics: in an isolated system, the total amount of energy does not change.
||1848||Scotland||William Thomson (Baron Kelvin) defines absolute zero and proposes the Kelvin scale.
||1849||France||Armand-Hippolyte-Louis Fizeau and Jean-Bernard-Léon Foucault determine the speed of light to within less than one percent error.
||1850||England||George Stokes discovers the terminal velocity of objects falling through viscous liquid.
||1850||Germany||Rudolf Clausius discovers the second law of thermodynamics, that the disorder of a closed system increases with time.
||1851||France||Jean-Bernard-Léon Foucault demonstrates the rotation of the earth with the Foucault pendulum.
||1852||England||James Joule and William Thomson discover the Joule-Thomson effect, which later permits liquefaction of some permanent gases.
|Johann Geissler invents Geissler tubes, producing a better vacuum. As improved by William Crookes, the tubes produce cathode rays, leading to discovery of the electron.
||1865||Scotland||James Maxwell's "A Dynamical Theory of the Electromagnetic Field" presents Maxwell's equations describing the behavior of electric and magnetic fields and proposes that light is electromagnetic in character, constituting the first theoretical unification of physical phenomena.
||1873||Scotland||James Maxwell's A Treatise on Electricity and Magnetism elaborates the mathematical model of electromagnetic waves, predicting such phenomena as radio waves and pressure caused by light rays.
||1875||England||William Crookes invents the radiometer, thereby providing support for the kinetic theory of gases.
||1876||Germany||Eugen Goldstein discovers cathode rays, streams of fluorescence flowing from the negatively charged cathode in an evacuated tube.
||1876||USA||Josiah Gibbs publishes the first of a series of papers applying thermodynamics to chemical hange, defining the concepts of free energy, chemical potential, equilibrium between phases of matter, and the phase rule, thereby establishing general principles of physical chemistry.
||1879||Austria||Josef Stefan discovers Stefan's Law, that the radiation of a body is proportional to the fourth power of its absolute temperature.
||1880||France||Pierre and Jacques Curie discover that ultrasonic vibrations are produced by piezoelectricity.
||1883||USA||Thomas Edison discovers the Edison effect, later a major factor in the invention of the vacuum tube.
||1886||Germany||Heinrich Hertz produces radio waves in the laboratory, confirming Maxwell's electromagnetic theory and laying the basis for radio, television, and radar.
||1887||USA||Albert Michelson and Edward Morley fail to confirm the existance of ether and demonstrate that the speed of light is a constant, raising questions about the adequacy of classical physics.
||1888||Germany||Eugen Goldstein discovers canal rays, from cathode rays.
||1892||Ireland||George Fitzgerald hypothesizes the Fitzgerald contraction, that distance contracts with speed, accounting for the results of the Michelson-Morley experiment.
||1892||Russia||Konstantin Tsiolkovsky begins theoretical work on rocket propulsion and space flight.
||1892||Scotland||James Dewar invents the Dewar flask.
||1895||Germany||Wilhelm Röntgen discovers X-rays.
||1895||Netherlands||Hendrik Antoon Lorentz extends Fitzgerald's work, hypothesizing that mass also increases with velocity, leading to the conclusion that the speed of light is a universal maximum.
||1895||Scotland||Charles Wilson invents the cloud chamber, which later becomes an indispensable tool in the study of atomic particles.
||1896||France||Antoine Becquerel discovers spontaneous radioactivity.
||1896||Netherlands||Pieter Zeeman discovers the splitting of lines in a spectrum when the spectrum's source is exposed to a magnetic field, the Zeeman effect, later used to study the fine details of atomic structure.
||1897||England||J.J. Thomson discovers the first subatomic particle, the electron.
||1897||France||Marie and Pierre Curie demonstrate that uranium radiation is an atomic phenomenon, not a molecular phenomenon, and coin the word radioactivity.
||1899||England||Ernest Rutherford discovers two types of uranium radiation, alpha rays (massive and positively charged) and beta rays (lighter and negatively charged).
||1900||France||Antoine-Henri Becquerel demonstrates that the process of radioactivity consists partly of particles identical to the electron.
||1900||Germany||Max Planck discovers Planck's Law of black body radiation, introducing Planck's constant and the concept that energy is radiated in discrete packets called quanta, founding quantum physics.
||1902||England||Ernest Rutherford and Frederick Soddy demonstrates that uranium and thorium break down into a series of radioactive intermediate elements.
||1904||England||J.J. Thomson proposes the "plum-pudding" model of the atom in which electrons are embedded in a sphere of positive electricity.
||1905||Switzerland||Albert Einstein's "Zur Elektrodynamik bewegter Körpen" introduces the special theory of relativity, that the assumption that light is quantized can explain the photoelectric effect, deduces as a consequence of the special theory of relativity that the mass of a body is a measure of its energy content, expressed as E=mc2, and explains Brownian motion mathematically, the most convincing evidence to date for the existence of molecules and atoms, and proposes a method to deduce the size of molecules and atoms.
||1906||Germany||Hermann Nernst states the third law of thermodynamics, that all bodies at absolute zero would have the same entropy, though absolute zero cannot be perfectly attained.
||1908||England||Ernest Rutherford and Johannes Geiger invent an alpha-particle counter.
||1908||France||Jean Perrin calculates atomic size from Brownian motion.
||1911||England||Ernest Rutherford, using using experimental results from Ernst Marsden and Johannes Geiger, proposes the concept of the atomic nucleus, leading to the deduction of the true nature of the atom.
||1911||Netherlands||Heike Kamerlingh-Onnes discovers superconductivity, the disappearance of electrical resistance in certain substances as they approach absolute zero.
||1911||USA||Victor Hess discovers the phenomenon later called cosmic rays.
||1912||Germany||Max von Laue develops X-ray diffraction using crystals, founding X-ray crystallography.
||1913||Denmark||Niels Bohr applies quantum theory to the structure of the atom, describing electron orbits and electron excitation and de-excitation.
||1913||England||Frederick Soddy and Kasimir Fajans discover isotopes, leading to the radioactive displacement law.
||1913||USA||Robert Millikan completes experiments determining the charge of an electron, leading to the conclusion that the electron is the fundamental unit of electricity.
||1914||England||Henry Moseley introduces the concept of atomic number, the amount of positive charge, on the nucleus, for classifying atoms.
||1914||England||Ernest Rutherford discovers the proton.
||1916||Germany||Albert Einstein's general theory of relativity describes space as a curved field modified locally by the existence of mass, replacing Newtonian ideas which invoke a force of gravity, and derives the basic equations for the exchange of energy between matter and radiation.
||1919||England||Francis Aston invents the mass spectrograph to measure the mass of atoms, and discovers isotopes in non-radioactive elements and states the whole-number rule.
||1919||England||Ernest Rutherford uses atomic bombardment to alter atomic nuclei, transforming one element into another and constituting the first nuclear reaction.
||1923||France||Louis de Broglie states that every particle should have an associated matter wave whose wavelength is inversely related to the particle's momentum, providing an explanation for the wave-particle duality of light.
||1923||USA||Arthur Compton discovers the Compton effect, whereby the wavelength of X-rays and gamma rays increases following collisions with electrons.
||1925||Germany||Wolfgang Pauli develops the exclusion principle stating that in a given atom no two electrons can have the identical set of four quantum numbers.
||1926||Austria||Erwin Schrödinger develops the mathematics of wave mechanics, including the Schrödinger wave equation.
||1927||England||Paul Dirac's relativistically invariant form of the wave equation of the electron unifies aspects of quantum mechanics and relativity theory.
||1927||Germany||Werner Heisenberg's "On the Intuitive Content of Quantum Kinematics and Mechanics" introduces the uncertainty principle.
||1928||Denmark||Niels Bohr's "The Philosophical Foundations of Quantum Theory" introduces the principle of complementarity, arguing that different but complementary models may be needed to explain the full range of atomic and subatomic phenomena.
||1930||England||Paul Dirac predicts the existence of antimatter.
||1930||USA||Nils Edlefsen and Ernest Lawrence invent the cyclotron, an instrument used to produce directed beams of charged particles that transforms research into fine nuclear structure.
||1931||Switzerland||Wolfgang Pauli predicts the existence of the particle later named the neutrino.
||1932||England||James Chadwick discovers the neutron.
||1932||England||John Cockroft achieves a nuclear reaction by splitting the atomic nucleus.
||1932||USA||Robert Millikan and Carl Anderson discover the positron, the first antiparticle.
||1933||Germany||Ernst Ruska and Reinhold Ruedenberg invent an electron microscope that is more powerful than a conventional light microscope.
||1934||Russia||Pavel Cherenkov, Ilya Frank, and Igor Tamm discover and interpret the Cherenkov effect, the wave of light produced by particles apparently moving faster than the speed of light in a medium other than a vacuum.
||1934||USA||Enrico Fermi achieves the first nuclear fission reaction.
||1935||Japan||Hideki Yukawa predicts the exitence of mesons as fundamental carriers of the nuclear force field.
||1938||Germany||Otto Hahn and Friedrich Strassman split an atomic nucleus into two parts by bombarding uranium-235 with neutrons.
||1940||USA||Martin Kamen discovers carbon-14, the most useful of all the radioactive tracers.
||1942||USA||Enrico Fermi, Walter Zinn, and Herbert Anderson achieve the first sustained nuclear reaction.
|Richard Feynman, Julian Schwinger, and Sin-Itiro Tomonaga independently work out the equations of quantum electrodynamics governing the behavior of electrons and electromagnetic reactions generally.
|Edwin McMillian and Vladimir Veksler independently invent the synchrotron.
||1947||England||Dennis Gabor develops the basic concept of holography, which must wait on the laser for implementation.
||1948||USA||John Bardeen, Walter Brattain, and William Shockley discover the transistor effect.