timeline A timeline is a display of a list of events in chronological order. It is typically a graphic design showing a long bar labelled with dates paralleling it, and usually contemporaneous events. Timelines can use any suitable scale represen ...

subatomic In physical sciences, a subatomic particle is a particle that composes an atom. According to the Standard Model of particle physics, a subatomic particle can be either a composite particle, which is composed of other particles (for example, a pro ...

Kanada Kanada may refer to: *Kanada (philosopher), the Hindu sage who founded the philosophy of Vaisheshika *Kanada (family of ragas), a group of ragas in Hindustani music *Kanada (surname) *Kanada Station, train station in Fukuoka, Japan *Kannada, one of ...

Democritus Democritus (; el, Δημόκριτος, ''Dēmókritos'', meaning "chosen of the people"; – ) was an Ancient Greek pre-Socratic philosopher from Abdera, primarily remembered today for his formulation of an atomic theory of the universe. No ...

atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, ...

Henry Cavendish Henry Cavendish ( ; 10 October 1731 – 24 February 1810) was an English natural philosopher and scientist who was an important experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed "infl ...

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

Carl Scheele Carl Wilhelm Scheele (, ; 9 December 1742 – 21 May 1786) was a Swedish German pharmaceutical chemist. Scheele discovered oxygen (although Joseph Priestley published his findings first), and identified molybdenum, tungsten, barium, hydro ...

Antoine Lavoisier Antoine-Laurent de Lavoisier ( , ; ; 26 August 17438 May 1794),
CNRS (

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...

is composed mostly of

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

* 1781

Joseph Priestley Joseph Priestley (; 24 March 1733 – 6 February 1804) was an English chemist, natural philosopher, separatist theologian, grammarian, multi-subject educator, and liberal political theorist. He published over 150 works, and conducted exp ...

creates water by igniting hydrogen and oxygen * 1800 William Nicholson and

Anthony Carlisle Sir Anthony Carlisle FRCS, FRS (15 February 1768 in Stillington, County Durham, England – 2 November 1840 in London) was an English surgeon. Life He was born in Stillington, County Durham, the third son of Thomas Carlisle and his first wife, a ...

use electrolysis to separate water into hydrogen and oxygen * 1803 John Dalton introduces atomic ideas into chemistry and states that

matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic part ...

is composed of atoms of different weights * 1805 (approximate time) Thomas Young conducts the double-slit experiment with light * 1811

Amedeo Avogadro Lorenzo Romano Amedeo Carlo Avogadro, Count of Quaregna and Cerreto (, also , ; 9 August 17769 July 1856) was an Italian scientist, most noted for his contribution to molecular theory now known as Avogadro's law, which states that equal volume ...

claims that equal volumes of gases should contain equal numbers of molecules * 1832

Michael Faraday Michael Faraday (; 22 September 1791 – 25 August 1867) was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic inducti ...

states his laws of electrolysis * 1871

Dmitri Mendeleyev Dmitri Ivanovich Mendeleev (sometimes transliterated as Mendeleyev or Mendeleef) ( ; russian: links=no, Дмитрий Иванович Менделеев, tr. , ; 8 February Old_Style_and_New_Style_dates">O.S._27_January.html" ;"title="O ...

systematically examines the periodic table and predicts the existence of gallium,

scandium Scandium is a chemical element with the symbol Sc and atomic number 21. It is a silvery-white metallic d-block element. Historically, it has been classified as a rare-earth element, together with yttrium and the Lanthanides. It was discovered in ...

, and germanium * 1873

Johannes van der Waals Johannes Diderik van der Waals (; 23 November 1837 – 8 March 1923) was a Dutch theoretical physics, theoretical physicist and thermodynamicist famous for his pioneering work on the equation of state for gases and liquids. Van der Waals starte ...

introduces the idea of weak attractive forces between molecules * 1885

Johann Balmer Johann Jakob Balmer (1 May 1825 – 12 March 1898) was a Swiss mathematician best known for his work in physics, the Balmer series of hydrogen atom. Biography Balmer was born in Lausen, Switzerland, the son of a chief justice also named Johan ...

finds a mathematical expression for observed

hydrogen line The hydrogen line, 21 centimeter line, or H I line is the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation has a precise frequency of , w ...

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, t ...

s * 1887

Heinrich Hertz Heinrich Rudolf Hertz ( ; ; 22 February 1857 – 1 January 1894) was a German physicist who first conclusively proved the existence of the electromagnetic waves predicted by James Clerk Maxwell's equations of electromagnetism. The unit ...

discovers the

photoelectric effect The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid sta ...

* 1894

Lord Rayleigh John William Strutt, 3rd Baron Rayleigh, (; 12 November 1842 – 30 June 1919) was an English mathematician and physicist who made extensive contributions to science. He spent all of his academic career at the University of Cambridge. Am ...

and

William Ramsay Sir William Ramsay (; 2 October 1852 – 23 July 1916) was a Scottish chemist who discovered the noble gases and received the Nobel Prize in Chemistry in 1904 "in recognition of his services in the discovery of the inert gaseous element ...

discover

argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as ...

by spectroscopically analyzing the gas left over after nitrogen and oxygen are removed from air * 1895

William Ramsay Sir William Ramsay (; 2 October 1852 – 23 July 1916) was a Scottish chemist who discovered the noble gases and received the Nobel Prize in Chemistry in 1904 "in recognition of his services in the discovery of the inert gaseous element ...

discovers terrestrial

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

by spectroscopically analyzing gas produced by decaying

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

* 1896 Antoine Becquerel discovers the radioactivity of uranium * 1896

Pieter Zeeman Pieter Zeeman (; 25 May 1865 – 9 October 1943) was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Hendrik Lorentz for his discovery of the Zeeman effect. Childhood and youth Pieter Zeeman was born in Zonnemaire, a small town ...

studies the splitting of sodium D lines when sodium is held in a flame between strong magnetic poles * 1897

Emil Wiechert Emil Johann Wiechert (26 December 1861 – 19 March 1928) was a German physicist and geophysicist who made many contributions to both fields, including presenting the first verifiable model of a layered structure of the Earth and being among the ...

, Walter Kaufmann and

J.J. Thomson Sir Joseph John Thomson (18 December 1856 – 30 August 1940) was a British physicist and Nobel Laureate in Physics, credited with the discovery of the electron, the first subatomic particle to be discovered. In 1897, Thomson showed that ...

discover the

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...

* 1898

Marie Marie may refer to: People Name * Marie (given name) * Marie (Japanese given name) * Marie (murder victim), girl who was killed in Florida after being pushed in front of a moving vehicle in 1973 * Marie (died 1759), an enslaved Cree person in Tr ...

and

Pierre Curie Pierre Curie ( , ; 15 May 1859 – 19 April 1906) was a French physicist, a pioneer in crystallography, magnetism, piezoelectricity, and radioactivity. In 1903, he received the Nobel Prize in Physics with his wife, Marie Curie, and Henri Becq ...

discovered the existence of the radioactive elements

radium Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rathe ...

and

polonium Polonium is a chemical element with the symbol Po and atomic number 84. Polonium is a chalcogen. A rare and highly radioactive metal with no stable isotopes, polonium is chemically similar to selenium and tellurium, though its metallic character ...

in their research of

pitchblende Uraninite, formerly pitchblende, is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2 but because of oxidation typically contains variable proportions of U3O8. Radioactive decay of the uranium causes t ...

* 1898

William Ramsay Sir William Ramsay (; 2 October 1852 – 23 July 1916) was a Scottish chemist who discovered the noble gases and received the Nobel Prize in Chemistry in 1904 "in recognition of his services in the discovery of the inert gaseous element ...

and

Morris Travers Morris William Travers, FRS (24 January 1872 – 25 August 1961) was an English chemist who worked with Sir William Ramsay in the discovery of xenon, neon and krypton. His work on several of the rare gases earned him the name ''Rare gas T ...

discover neon, and negatively charged beta particles

The age of quantum mechanics

* 1887 Heinrich Rudolf Hertz discovers the

photoelectric effect The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid sta ...

that will play a very important role in the development of the

quantum theory Quantum theory may refer to: Science *Quantum mechanics, a major field of physics *Old quantum theory, predating modern quantum mechanics * Quantum field theory, an area of quantum mechanics that includes: ** Quantum electrodynamics ** Quantum ...

with Einstein's explanation of this effect in terms of '' quanta'' of light * 1896

Wilhelm Conrad Röntgen Wilhelm may refer to: People and fictional characters * William Charles John Pitcher, costume designer known professionally as "Wilhelm" * Wilhelm (name), a list of people and fictional characters with the given name or surname Other uses * Mount ...

discovers the

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

s while studying electrons in plasma; scattering X-rays—that were considered as 'waves' of high-energy

electromagnetic radiation In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) li ...

— Arthur Compton will be able to demonstrate in 1922 the 'particle' aspect of electromagnetic radiation. * 1900 Paul Villard discovers

gamma-ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically sh ...

s while studying uranium decay * 1900

Johannes Rydberg Johannes (Janne) Robert Rydberg (; 8 November 1854 – 28 December 1919) was a Swedish physicist mainly known for devising the Rydberg formula, in 1888, which is used to describe the wavelengths of photons (of visible light and other electrom ...

refines the expression for observed hydrogen line wavelengths * 1900

Max Planck Max Karl Ernst Ludwig Planck (, ; 23 April 1858 – 4 October 1947) was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial contributions to theoretical p ...

states his

quantum hypothesis Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, qua ...

and blackbody radiation law * 1902

Philipp Lenard Philipp Eduard Anton von Lenard (; hu, Lénárd Fülöp Eduárd Antal; 7 June 1862 – 20 May 1947) was a Hungarian-born German physicist and the winner of the Nobel Prize for Physics in 1905 for his work on cathode rays and the discovery of ...

observes that maximum

photoelectron The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid sta ...

energies are independent of illuminating intensity but depend on frequency * 1905 Albert Einstein explains the

photoelectric effect The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid sta ...

* 1906

Charles Barkla Charles Glover Barkla FRS FRSE (7 June 1877 – 23 October 1944) was a British physicist, and the winner of the Nobel Prize in Physics in 1917 for his work in X-ray spectroscopy and related areas in the study of X-rays ( Roentgen rays). Lif ...

discovers that each element has a characteristic

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

and that the degree of penetration of these X-rays is related to the

atomic weight Relative atomic mass (symbol: ''A''; sometimes abbreviated RAM or r.a.m.), also known by the deprecated synonym atomic weight, is a dimensionless physical quantity defined as the ratio of the average mass of atoms of a chemical element in a giv ...

of the element * 1909

Hans Geiger Johannes Wilhelm "Hans" Geiger (; ; 30 September 1882 – 24 September 1945) was a German physicist. He is best known as the co-inventor of the detector component of the Geiger counter and for the Geiger–Marsden experiment which discover ...

and

Ernest Marsden Sir Ernest Marsden (19 February 1889 – 15 December 1970) was an English-New Zealand physicist. He is recognised internationally for his contributions to science while working under Ernest Rutherford, which led to the discovery of new theories ...

discover large angle deflections of alpha particles by thin metal foils * 1909

Ernest Rutherford Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand physicist who came to be known as the father of nuclear physics. ''Encyclopædia Britannica'' considers him to be the greatest ...

and

Thomas Royds Thomas Royds (April 11, 1884 – May 1, 1955) was a British solar physicist who worked with Ernest Rutherford on the identification of alpha radiation as the nucleus of the helium atom, and who was Director of the Kodaikanal Solar Observatory, I ...

demonstrate that alpha particles are doubly

ionized Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...

helium atoms * 1911

Ernest Rutherford Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand physicist who came to be known as the father of nuclear physics. ''Encyclopædia Britannica'' considers him to be the greatest ...

explains the Geiger–Marsden experiment by invoking a nuclear atom model and derives the Rutherford cross section * 1911 Jean Perrin proves the existence of atoms and molecules with experimental work to test Einstein's theoretical explanation of

Brownian motion Brownian motion, or pedesis (from grc, πήδησις "leaping"), is the random motion of particles suspended in a medium (a liquid or a gas). This pattern of motion typically consists of random fluctuations in a particle's position insi ...

* 1911 Ștefan Procopiu measures the magnetic dipole moment of the electron * 1912 Max von Laue suggests using crystal lattices to

diffract Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a s ...

X-rays * 1912 Walter Friedrich and Paul Knipping diffract X-rays in zinc blende * 1913

William Henry Bragg Sir William Henry Bragg (2 July 1862 – 12 March 1942) was an English physicist, chemist, mathematician, and active sportsman who uniquelyThis is still a unique accomplishment, because no other parent-child combination has yet shared a Nob ...

and

William Lawrence Bragg Sir William Lawrence Bragg, (31 March 1890 – 1 July 1971) was an Australian-born British physicist and X-ray crystallographer, discoverer (1912) of Bragg's law of X-ray diffraction, which is basic for the determination of crystal structu ...

work out the Bragg condition for strong X-ray reflection * 1913

Henry Moseley Henry Gwyn Jeffreys Moseley (; 23 November 1887 – 10 August 1915) was an English physicist, whose contribution to the science of physics was the justification from physical laws of the previous empirical and chemical concept of the atomic num ...

shows that nuclear charge is the real basis for numbering the elements * 1913

Niels Bohr Niels Henrik David Bohr (; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922 ...

presents his quantum model of the atom * 1913

Robert Millikan Robert Andrews Millikan (March 22, 1868 – December 19, 1953) was an American experimental physicist honored with the Nobel Prize for Physics in 1923 for the measurement of the elementary electric charge and for his work on the photoelectric ...

measures the fundamental unit of electric charge * 1913

Johannes Stark Johannes Stark (, 15 April 1874 – 21 June 1957) was a German physicist who was awarded the Nobel Prize in Physics in 1919 "for his discovery of the Doppler effect in canal rays and the splitting of spectral lines in electric fields". This phe ...

demonstrates that strong electric fields will split the Balmer spectral line series of hydrogen * 1914

James Franck James Franck (; 26 August 1882 – 21 May 1964) was a German physicist who won the 1925 Nobel Prize for Physics with Gustav Hertz "for their discovery of the laws governing the impact of an electron upon an atom". He completed his doctorate i ...

and

Gustav Hertz Gustav Ludwig Hertz (; 22 July 1887 – 30 October 1975) was a German experimental physicist and Nobel Prize winner for his work on inelastic electron collisions in gases, and a nephew of Heinrich Rudolf Hertz. Biography Hertz was born in Hamb ...

observe atomic excitation * 1914

Ernest Rutherford Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand physicist who came to be known as the father of nuclear physics. ''Encyclopædia Britannica'' considers him to be the greatest ...

suggests that the positively charged atomic nucleus contains protons * 1915 Arnold Sommerfeld develops a modified Bohr atomic model with elliptic orbits to explain relativistic fine structure * 1916 Gilbert N. Lewis and Irving Langmuir formulate an electron shell model of

chemical bond A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules and crystals. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing of ...

ing * 1917

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...

introduces the idea of stimulated radiation emission * 1918 Ernest Rutherford notices that, when

alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be pr ...

s were shot into

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

gas, his scintillation detectors showed the signatures of

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

nuclei. * 1921

Alfred Landé Alfred Landé (13 December 1888 – 30 October 1976) was a German-American physicist known for his contributions to quantum theory. He is responsible for the Landé g-factor and an explanation of the Zeeman effect. Life and achievements Alf ...

introduces the

Landé g-factor In physics, the Landé ''g''-factor is a particular example of a ''g''-factor, namely for an electron with both spin and orbital angular momenta. It is named after Alfred Landé, who first described it in 1921. In atomic physics, the Landé '' ...

* 1922 Arthur Compton studies X-ray photon scattering by electrons demonstrating the 'particle' aspect of electromagnetic radiation. * 1922

Otto Stern :''Otto Stern was also the pen name of German women's rights activist Louise Otto-Peters (1819–1895)''. Otto Stern (; 17 February 1888 – 17 August 1969) was a German-American physicist and Nobel laureate in physics. He was the second most n ...

and

Walther Gerlach Walther Gerlach (1 August 1889 – 10 August 1979) was a German physicist who co-discovered, through laboratory experiment, spin quantization in a magnetic field, the Stern–Gerlach effect. The experiment was conceived by Otto Stern in 1921 an ...

show " spin quantization" * 1923 Lise Meitner discovers what is now referred to as the

Auger process Auger may refer to: Engineering * Wood auger, a drill for making holes in wood (or in the ground) ** Auger bit, a drill bit * Auger conveyor, a device for moving material by means of a rotating helical flighting * Auger (platform), the world' ...

* 1924

Louis de Broglie Louis Victor Pierre Raymond, 7th Duc de Broglie (, also , or ; 15 August 1892 – 19 March 1987) was a French physicist and aristocrat who made groundbreaking contributions to Old quantum theory, quantum theory. In his 1924 PhD thesis, he pos ...

suggests that electrons may have wavelike properties in addition to their 'particle' properties; the ''

wave–particle duality Wave–particle duality is the concept in quantum mechanics that every particle or quantum entity may be described as either a particle or a wave. It expresses the inability of the classical concepts "particle" or "wave" to fully describe the b ...

'' has been later extended to all fermions and bosons. * 1924

John Lennard-Jones Sir John Edward Lennard-Jones (27 October 1894 – 1 November 1954) was a British mathematician and professor of theoretical physics at the University of Bristol, and then of theoretical science at the University of Cambridge. He was an im ...

proposes a semiempirical interatomic force law * 1924 Santiago Antúnez de Mayolo proposes a neutron. * 1924 Satyendra Bose and Albert Einstein introduce

Bose–Einstein statistics In quantum statistics, Bose–Einstein statistics (B–E statistics) describes one of two possible ways in which a collection of non-interacting, indistinguishable particles may occupy a set of available discrete energy states at thermodynamic ...

* 1925

Wolfgang Pauli Wolfgang Ernst Pauli (; ; 25 April 1900 – 15 December 1958) was an Austrian theoretical physicist and one of the pioneers of quantum physics. In 1945, after having been nominated by Albert Einstein, Pauli received the Nobel Prize in Physics ...

states the quantum exclusion principle for electrons * 1925

George Uhlenbeck George Eugene Uhlenbeck (December 6, 1900 – October 31, 1988) was a Dutch-American theoretical physicist. Background and education George Uhlenbeck was the son of Eugenius and Anne Beeger Uhlenbeck. He attended the Hogere Burgerschool (High S ...

and

Samuel Goudsmit Samuel Abraham Goudsmit (July 11, 1902 – December 4, 1978) was a Dutch-American physicist famous for jointly proposing the concept of electron spin with George Eugene Uhlenbeck in 1925. Life and career Goudsmit was born in The Hague, Nethe ...

postulate electron spin * 1925 Pierre Auger discovers the

Auger process Auger may refer to: Engineering * Wood auger, a drill for making holes in wood (or in the ground) ** Auger bit, a drill bit * Auger conveyor, a device for moving material by means of a rotating helical flighting * Auger (platform), the world' ...

(2 years after Lise Meitner) * 1925

Werner Heisenberg Werner Karl Heisenberg () (5 December 1901 – 1 February 1976) was a German theoretical physicist and one of the main pioneers of the theory of quantum mechanics. He published his work in 1925 in a breakthrough paper. In the subsequent serie ...

, Max Born, and

Pascual Jordan Ernst Pascual Jordan (; 18 October 1902 – 31 July 1980) was a German theoretical and mathematical physicist who made significant contributions to quantum mechanics and quantum field theory. He contributed much to the mathematical form of matri ...

formulate quantum

matrix mechanics Matrix mechanics is a formulation of quantum mechanics created by Werner Heisenberg, Max Born, and Pascual Jordan in 1925. It was the first conceptually autonomous and logically consistent formulation of quantum mechanics. Its account of quantum j ...

* 1926

Erwin Schrödinger Erwin Rudolf Josef Alexander Schrödinger (, ; ; 12 August 1887 – 4 January 1961), sometimes written as or , was a Nobel Prize-winning Austrian physicist with Irish citizenship who developed a number of fundamental results in quantum theo ...

states his nonrelativistic quantum wave equation and formulates quantum wave mechanics * 1926

Erwin Schrödinger Erwin Rudolf Josef Alexander Schrödinger (, ; ; 12 August 1887 – 4 January 1961), sometimes written as or , was a Nobel Prize-winning Austrian physicist with Irish citizenship who developed a number of fundamental results in quantum theo ...

proves that the wave and matrix formulations of quantum theory are mathematically equivalent * 1926 Oskar Klein and Walter Gordon state their relativistic quantum wave equation, now the

Klein–Gordon equation The Klein–Gordon equation (Klein–Fock–Gordon equation or sometimes Klein–Gordon–Fock equation) is a relativistic wave equation, related to the Schrödinger equation. It is second-order in space and time and manifestly Lorentz-covariant ...

* 1926 Enrico Fermi discovers the spin–statistics connection, for particles that are now called 'fermions', such as the electron (of

spin-1/2 In quantum mechanics, spin is an intrinsic property of all elementary particles. All known fermions, the particles that constitute ordinary matter, have a spin of . The spin number describes how many symmetrical facets a particle has in one full ...

). * 1926

Paul Dirac Paul Adrien Maurice Dirac (; 8 August 1902 – 20 October 1984) was an English theoretical physicist who is regarded as one of the most significant physicists of the 20th century. He was the Lucasian Professor of Mathematics at the Univer ...

introduces Fermi–Dirac statistics * 1926 Gilbert N. Lewis introduces the term "''photon''", thought by him to be "''the carrier of

radiant energy Radiant may refer to: Computers, software, and video games * Radiant (software), a content management system * GtkRadiant, a level editor created by id Software for their games * Radiant AI, a technology developed by Bethesda Softworks for '' ...

.''" * 1927

Clinton Davisson Clinton Joseph Davisson (October 22, 1881 – February 1, 1958) was an American physicist who won the 1937 Nobel Prize in Physics for his discovery of electron diffraction in the famous Davisson–Germer experiment. Davisson shared the Nobel Priz ...

,

Lester Germer Lester Halbert Germer (October 10, 1896 – October 3, 1971) was an American physicist. With Clinton Davisson, he proved the wave-particle duality of matter in the Davisson–Germer experiment, which was important to the development of the elect ...

, and

George Paget Thomson Sir George Paget Thomson, FRS (; 3 May 189210 September 1975) was a British physicist and Nobel laureate in physics recognized for his discovery of the wave properties of the electron by electron diffraction. Education and early life Thomso ...

confirm the wavelike nature of electrons * 1927

Werner Heisenberg Werner Karl Heisenberg () (5 December 1901 – 1 February 1976) was a German theoretical physicist and one of the main pioneers of the theory of quantum mechanics. He published his work in 1925 in a breakthrough paper. In the subsequent serie ...

states the quantum

uncertainty principle In quantum mechanics, the uncertainty principle (also known as Heisenberg's uncertainty principle) is any of a variety of mathematical inequalities asserting a fundamental limit to the accuracy with which the values for certain pairs of physic ...

* 1927 Max Born interprets the probabilistic nature of wavefunctions * 1927

Walter Heitler Walter Heinrich Heitler (; 2 January 1904 – 15 November 1981) was a German physicist who made contributions to quantum electrodynamics and quantum field theory. He brought chemistry under quantum mechanics through his theory of valence bond ...

and

Fritz London Fritz Wolfgang London (March 7, 1900 – March 30, 1954) was a German physicist and professor at Duke University. His fundamental contributions to the theories of chemical bonding and of intermolecular forces ( London dispersion forces) are today ...

introduce the concepts of valence bond theory and apply it to the

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

molecule. * 1927

Thomas Thomas may refer to: People * List of people with given name Thomas * Thomas (name) * Thomas (surname) * Saint Thomas (disambiguation) * Thomas Aquinas (1225–1274) Italian Dominican friar, philosopher, and Doctor of the Church * Thomas the A ...

and Fermi develop the Thomas–Fermi model * 1927 Max Born and

Robert Oppenheimer J. Robert Oppenheimer (; April 22, 1904 – February 18, 1967) was an American theoretical physicist. A professor of physics at the University of California, Berkeley, Oppenheimer was the wartime head of the Los Alamos Laboratory and is often ...

introduce the

Born–Oppenheimer approximation In quantum chemistry and molecular physics, the Born–Oppenheimer (BO) approximation is the best-known mathematical approximation in molecular dynamics. Specifically, it is the assumption that the wave functions of atomic nuclei and elect ...

* 1928 Chandrasekhara Raman studies optical photon scattering by electrons * 1928

Paul Dirac Paul Adrien Maurice Dirac (; 8 August 1902 – 20 October 1984) was an English theoretical physicist who is regarded as one of the most significant physicists of the 20th century. He was the Lucasian Professor of Mathematics at the Univer ...

states his relativistic electron quantum wave equation * 1928 Charles G. Darwin and Walter Gordon solve the

Dirac equation In particle physics, the Dirac equation is a relativistic wave equation derived by British physicist Paul Dirac in 1928. In its free form, or including electromagnetic interactions, it describes all spin- massive particles, called "Dirac par ...

for a Coulomb potential * 1928

Friedrich Hund Friedrich Hermann Hund (4 February 1896 – 31 March 1997) was a German physicist from Karlsruhe known for his work on atoms and molecules. Scientific career Hund worked at the Universities of Rostock, Leipzig, Jena, Frankfurt am Main, and Göt ...

and

Robert S. Mulliken Robert Sanderson Mulliken Note Longuet-Higgins' amusing title for reference B238 1965 on page 354 of this Biographical Memoir. The title should be "Selected papers of Robert S Mulliken." (June 7, 1896 – October 31, 1986) was an American ph ...

introduce the concept of

molecular orbital In chemistry, a molecular orbital is a mathematical function describing the location and wave-like behavior of an electron in a molecule. This function can be used to calculate chemical and physical properties such as the probability of findin ...

* 1929 Oskar Klein discovers the Klein paradox * 1929 Oskar Klein and

Yoshio Nishina was a Japanese physicist who was called "the founding father of modern physics research in Japan". He led the efforts of Japan to develop an atomic bomb during World War II. Early life and career Nishina was born in Satoshō, Okayama. He rece ...

derive the Klein–Nishina cross section for high energy photon scattering by electrons * 1929

Nevill Mott Sir Nevill Francis Mott (30 September 1905 – 8 August 1996) was a British physicist who won the Nobel Prize for Physics in 1977 for his work on the electronic structure of magnetic and disordered systems, especially amorphous semiconductors. ...

derives the Mott cross section for the Coulomb scattering of relativistic electrons * 1930

Paul Dirac Paul Adrien Maurice Dirac (; 8 August 1902 – 20 October 1984) was an English theoretical physicist who is regarded as one of the most significant physicists of the 20th century. He was the Lucasian Professor of Mathematics at the Univer ...

introduces electron hole theory * 1930

Erwin Schrödinger Erwin Rudolf Josef Alexander Schrödinger (, ; ; 12 August 1887 – 4 January 1961), sometimes written as or , was a Nobel Prize-winning Austrian physicist with Irish citizenship who developed a number of fundamental results in quantum theo ...

predicts the

zitterbewegung In physics, the zitterbewegung ("jittery motion" in German, ) is the predicted rapid oscillatory motion of elementary particles that obey relativistic wave equations. The existence of such motion was first discussed by Gregory Breit in 1928 and la ...

motion * 1930

Fritz London Fritz Wolfgang London (March 7, 1900 – March 30, 1954) was a German physicist and professor at Duke University. His fundamental contributions to the theories of chemical bonding and of intermolecular forces ( London dispersion forces) are today ...

explains

van der Waals force In molecular physics, the van der Waals force is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and th ...

s as due to the interacting fluctuating dipole moments between molecules * 1931

John Lennard-Jones Sir John Edward Lennard-Jones (27 October 1894 – 1 November 1954) was a British mathematician and professor of theoretical physics at the University of Bristol, and then of theoretical science at the University of Cambridge. He was an im ...

proposes the Lennard-Jones interatomic potential * 1931

Irène Joliot-Curie Irène Joliot-Curie (; ; 12 September 1897 – 17 March 1956) was a French chemist, physicist and politician, the elder daughter of Pierre and Marie Curie, and the wife of Frédéric Joliot-Curie. Jointly with her husband, Joliot-Curie was awar ...

and Frédéric Joliot observe but misinterpret neutron scattering in paraffin * 1931

Wolfgang Pauli Wolfgang Ernst Pauli (; ; 25 April 1900 – 15 December 1958) was an Austrian theoretical physicist and one of the pioneers of quantum physics. In 1945, after having been nominated by Albert Einstein, Pauli received the Nobel Prize in Physics ...

puts forth the

neutrino A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...

hypothesis to explain the apparent violation of energy conservation in beta decay * 1931 Linus Pauling discovers resonance bonding and uses it to explain the high stability of symmetric planar molecules * 1931

Paul Dirac Paul Adrien Maurice Dirac (; 8 August 1902 – 20 October 1984) was an English theoretical physicist who is regarded as one of the most significant physicists of the 20th century. He was the Lucasian Professor of Mathematics at the Univer ...

shows that

charge quantization The elementary charge, usually denoted by is the electric charge carried by a single proton or, equivalently, the magnitude of the negative electric charge carried by a single electron, which has charge −1 . This elementary charge is a fundame ...

can be explained if

magnetic monopole In particle physics, a magnetic monopole is a hypothetical elementary particle that is an isolated magnet with only one magnetic pole (a north pole without a south pole or vice versa). A magnetic monopole would have a net north or south "magneti ...

s exist * 1931 Harold Urey discovers deuterium using evaporation concentration techniques and spectroscopy * 1932 John Cockcroft and Ernest Walton split lithium and boron nuclei using proton bombardment * 1932 James Chadwick discovers the neutron * 1932

Werner Heisenberg Werner Karl Heisenberg () (5 December 1901 – 1 February 1976) was a German theoretical physicist and one of the main pioneers of the theory of quantum mechanics. He published his work in 1925 in a breakthrough paper. In the subsequent serie ...

presents the proton–neutron model of the nucleus and uses it to explain isotopes * 1932 Carl D. Anderson discovers the positron * 1933 Ernst Stueckelberg (1932), Lev Landau (1932), and Clarence Zener discover the Landau–Zener transition * 1933 Max Delbrück suggests that quantum effects will cause photons to be scattered by an external electric field * 1934

Irène Joliot-Curie Irène Joliot-Curie (; ; 12 September 1897 – 17 March 1956) was a French chemist, physicist and politician, the elder daughter of Pierre and Marie Curie, and the wife of Frédéric Joliot-Curie. Jointly with her husband, Joliot-Curie was awar ...

and Frédéric Joliot bombard aluminium atoms with alpha particles to create artificially radioactive phosphorus-30 * 1934 Leó Szilárd realizes that nuclear chain reactions may be possible * 1934 Enrico Fermi publishes a very successful model of beta decay in which neutrinos were produced. * 1934 Lev Landau tells Edward Teller that non-linear molecules may have vibrational modes which remove the degenerate energy level, degeneracy of an orbitally degenerate state (Jahn–Teller effect) * 1934 Enrico Fermi suggests bombarding uranium atoms with neutrons to make a 93 proton element * 1934 Pavel Cherenkov reports that Cherenkov effect, light is emitted by relativistic particles traveling in a nonscintillating liquid * 1935 Hideki Yukawa presents a theory of the nuclear force and predicts the scalar meson * 1935

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...

, Boris Podolsky, and Nathan Rosen put forth the EPR paradox * 1935 Henry Eyring (chemist), Henry Eyring develops the transition state theory * 1935

Niels Bohr Niels Henrik David Bohr (; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922 ...

presents his analysis of the EPR paradox * 1936 Alexandru Proca formulates the relativistic quantum field equations for a massive vector meson of spin-1 as a basis for nuclear forces * 1936 Eugene Wigner develops the theory of neutron absorption by atomic nuclei * 1936 Hermann Arthur Jahn and Edward Teller present their systematic study of the symmetry types for which the Jahn–Teller effect is expected * 1937 Carl Anderson proves experimentally the existence of the pion predicted by Yukawa's theory. * 1937 Hans Hellmann finds the Hellmann–Feynman theorem * 1937 Seth Neddermeyer, Carl David Anderson, Carl Anderson, J.C. Street, and E.C. Stevenson discover muons using cloud chamber measurements of cosmic rays * 1939 Richard Feynman finds the Hellmann–Feynman theorem * 1939 Otto Hahn and Fritz Strassmann bombard uranium salts with thermal neutrons and discover barium among the reaction products * 1939 Lise Meitner and Otto Robert Frisch determine that nuclear fission is taking place in the Hahn–Strassmann experiments * 1942 Enrico Fermi makes the first controlled nuclear chain reaction * 1942 Ernst Stueckelberg introduces the propagator to positron theory and interprets positrons as negative energy electrons moving backwards through spacetime * 1947 Willis Lamb and Robert Retherford measure the Lamb–Retherford shift * 1947 Cecil Powell, César Lattes, and Giuseppe Occhialini discover the pion, pi meson by studying cosmic ray tracks * 1947 Richard Feynman presents path integral formulation of quantum mechanics, his propagator approach to quantum electrodynamics * 1948 Hendrik Casimir predicts a rudimentary attractive Casimir effect, Casimir force on a parallel plate capacitor * 1951 Martin Deutsch discovers positronium * 1952 David Bohm propose Bohm interpretation, his interpretation of quantum mechanics * 1953 Robert R. Wilson, Robert Wilson observes Delbruck scattering of 1.33 MeV gamma-rays by the electric fields of lead nuclei * 1953 Charles H. Townes, collaborating with J. P. Gordon, and H. J. Zeiger, builds the first ammonia maser * 1954 Chen Ning Yang and Robert Mills (physicist), Robert Mills investigate a Yang–Mills theory, theory of hadronic isospin by demanding local gauge invariance under isotopic spin space rotations, the first non-Abelian gauge theory * 1955 Owen Chamberlain, Emilio Segrè, Clyde Wiegand, and Thomas Ypsilantis discover the antiproton * 1956 Frederick Reines and Clyde Cowan detect antineutrino * 1956 Chen Ning Yang and Tsung Lee propose parity violation by the weak nuclear force * 1956 Chien Shiung Wu discovers parity violation by the weak force in decaying cobalt * 1957 Gerhart Luders proves the CPT theorem * 1957 Richard Feynman, Murray Gell-Mann, Robert Marshak, and E.C.G. Sudarshan propose a vector/axial vector (VA) Lagrangian (field theory), Lagrangian for weak interactions. * 1958 Marcus Sparnaay experimentally confirms the Casimir effect * 1959 Yakir Aharonov and David Bohm predict the Aharonov–Bohm effect * 1960 Robert G. Chambers, R.G. Chambers experimentally confirms the Aharonov–Bohm effect * 1961 Murray Gell-Mann and Yuval Ne'eman discover the Eightfold way (physics), Eightfold Way patterns, the special unitary group, SU(3) group * 1961 Jeffrey Goldstone considers the breaking of global phase symmetry * 1962 Leon Lederman shows that the electron neutrino is distinct from the muon neutrino * 1963 Eugene Wigner discovers the fundamental roles played by quantum symmetries in atoms and molecules

The formation and successes of the Standard Model

* 1964 Murray Gell-Mann and George Zweig propose the quark model, quark/aces modelFrank Wilczek (1999)
Quantum field theory
, ''Reviews of Modern Physics'' 71: S83–S95. Also doi=10.1103/Rev. Mod. Phys. 71. * 1964 Peter Higgs considers the breaking of local phase symmetry * 1964 John Stewart Bell shows that all local hidden variable theories must satisfy Bell's inequality * 1964 Val Fitch and James Cronin observe CP violation by the weak force in the decay of K mesons * 1967 Steven Weinberg puts forth his electroweak model of leptonsWeinberg, Steven; The Quantum Theory of Fields: Modern Applications (vol. II), Cambridge University Press:Cambridge, U.K. (1996) , pp. 489. * 1969 John Clauser, Michael Horne, Abner Shimony and Richard Holt (physicist), Richard Holt propose a polarization correlation test of Bell's inequality * 1970 Sheldon Glashow, John Iliopoulos, and Luciano Maiani propose the charm quark * 1971 Gerard 't Hooft shows that the Glashow-Salam-Weinberg electroweak model can be renormalized * 1972 Stuart Freedman and John Clauser perform the first polarization correlation test of Bell's inequality * 1973 David Politzer and Frank Wilczek, Frank Anthony Wilczek propose the asymptotic freedom of quarks * 1974 Burton Richter and Samuel Ting discover the J/ψ particle implying the existence of the charm quark * 1974 Robert J. Buenker and Sigrid D. Peyerimhoff introduce the multireference configuration interaction method. * 1975 Martin Perl discovers the tau lepton * 1977 Steve Herb finds the upsilon particle, upsilon resonance implying the existence of the bottom quark, beauty/bottom quark * 1982 Alain Aspect, J. Dalibard, and G. Roger perform a polarization correlation test of Bell's inequality that rules out conspiratorial polarizer communication * 1983 Carlo Rubbia, Simon van der Meer, and the CERN UA-1 collaboration find the W and Z bosons, W and Z intermediate vector bosons * 1989 The Z intermediate vector boson resonance#Theory, resonance width indicates three generation (particle physics), quark-lepton generations * 1994 The CERN LEAR Crystal Barrel Experiment justifies the existence of glueballs (exotic meson). * 1995 The D0 experiment, D0 and Collider Detector at Fermilab, CDF experiments at the Fermilab Tevatron discover the top quark. * 1998 Super-Kamiokande (Japan) observes evidence for neutrino oscillations, implying that at least one neutrino has mass. * 1999 Ahmed Zewail wins the Nobel prize in chemistry for his work on femtochemistry for atoms and molecules. * 2001 The Sudbury Neutrino Observatory (Canada) confirms the existence of neutrino oscillations. * 2005 At the RHIC accelerator of Brookhaven National Laboratory they have created a quark–gluon liquid of very low viscosity, perhaps the quark–gluon plasma * 2010 The Large Hadron Collider at CERN begins operation with the primary goal of searching for the Higgs boson. * 2012 CERN announces the discovery of a new particle with properties consistent with the Higgs boson of the Standard Model after experiments at the Large Hadron Collider.

Quantum field theories beyond the Standard Model

* 2000 Steven Weinberg. Supersymmetry and Quantum Gravity. *2003 Leonid Vainerman. Quantum groups, Hopf algebras and quantum field applications.Leonid Vainerman, editor. 2003. ''Locally Compact Quantum Groups and Groupoids''. ''Proceed. Theor. Phys. Strassbourg in 2002'', Walter de Gruyter: Berlin and New York *Noncommutative quantum field theory * M.R. Douglas and N. A. Nekrasov (2001)
Noncommutative field theory
" Rev. Mod. Phys. 73: 977–1029. * Szabo, R. J. (2003)
Quantum Field Theory on Noncommutative Spaces
" ''Physics Reports'' 378: 207–99. An expository article on noncommutative quantum field theories.
Noncommutative quantum field theory, see statistics
on arxiv.org * Seiberg, N. and E. Witten (1999)
String Theory and Noncommutative Geometry
" ''Journal of High Energy Physics'' * Sergio Doplicher, Klaus Fredenhagen and John Roberts, Sergio Doplicher, Klaus Fredenhagen, John E. Roberts (1995
The quantum structure of spacetime at the Planck scale and quantum fields
" ''Commun. Math. Phys''. 172: 187–220. * Alain Connes (1994)
Noncommutative geometry.
' Academic Press. . * -------- (1995) "Noncommutative geometry and reality", ''J. Math. Phys.'' 36: 6194. * -------- (1996)
Gravity coupled with matter and the foundation of noncommutative geometry
" ''Comm. Math. Phys.'' 155: 109. * -------- (2006)
Noncommutative geometry and physics
" * -------- and Matilde Marcolli, M. Marcolli,
Noncommutative Geometry: Quantum Fields and Motives.
' American Mathematical Society (2007). * Chamseddine, A., A. Connes (1996)
The spectral action principle
" ''Comm. Math. Phys.'' 182: 155. * Chamseddine, A., A. Connes, Matilde Marcolli, M. Marcolli (2007)
Gravity and the Standard Model with neutrino mixing
" ''Adv. Theor. Math. Phys.'' 11: 991. * Jureit, Jan-H., Thomas Krajewski, Thomas Schücker, and Christoph A. Stephan (2007)
On the noncommutative standard model
" ''Acta Phys. Polon.'' B38: 3181–3202. *Schücker, Thomas (2005)
Forces from Connes's geometry.
' Lecture Notes in Physics 659, Springer. *Noncommutative standard model *Noncommutative geometry

References

External links

Alain Connes official website
wit
downloadable papers.

{{DEFAULTSORT:Timeline Of Atomic And Subatomic Physics Particle physics Nuclear physics Atomic physics Physics timelines, Atomic

Early beginnings

The beginning of chemistry

The age of quantum mechanics

The formation and successes of the Standard Model

Quantum field theories beyond the Standard Model

See also

References

External links