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User:Guy vandegrift/Timeline of quantum (abridged)

• 1859 – Kirchhoff introduces the concept of a blackbody and proves that its emission spectrum de- pends only on its temperature.[1] • 1860–1900 – Ludwig Eduard Boltzmann, James Clerk Maxwell and others develop the theory of statistical mechanics. Boltzmann argues that is a measure of disorder.[1] Boltzmann sug- gests that the energy levels of a physical system could be discrete based on statistical mechanics and mathematical arguments; also produces a primitive diagram of a model of an iodine molecule that re- sembles the orbital diagram. • 18871888 – Heinrich Hertz discovers the photo- Refereed version electric effect, and also demonstrates experimen- tally that electromagnetic exist, as predicted by Maxwell.[1] This article is edited from a document extracted from • Wikipedia’s 'Timeline of at 13:07, 2 1888 – Johannes Rydberg modifies the Balmer for- September 2015 (oldid 679101670) mula to include all spectral series of lines for the hydrogen , producing the . This abridged “timeline of quantum mechancis” shows some of the key steps in the development of quantum me- • 1895 – Wilhelm Conrad Röntgen discovers X-rays chanics, quantum field theories and quantum in experiments with beams in plasma.[1] that occurred before the end of World War II [1][2] • 1896 – Antoine accidentally dis- covers radioactivity while investigating the work of Wilhelm Conrad Röntgen; he finds that 1 19th century salts emit radiation that resembled Röntgen’s X- rays in their penetrating power, and accidentally dis- covers that the phosphorescent substance potassium uranyl sulfate exposes photographic plates.[1][3] • 1896 – observes the Zeeman split- ting effect by passing the emitted by hydrogen through a magnetic field. • 1896–1897 investigates uranium salt samples using a very sensitive electrometer device that was invented 15 years before by her husband and his brother Jacques Curie to measure electrical charge. She discovers that the emitted rays make the surrounding air electrically conductive. Through a systematic search of substances, she finds that thorium compounds, like those of uranium, emit- ted “Becquerel rays”, thus preceding the work of Frederick Soddy and on the nu- Image of Becquerel’s photographic plate which has been fogged clear decay of thorium to radium by three years.[4] by exposure to radiation from a uranium salt. The shadow of a metal Maltese Cross placed between the plate and the uranium • 1897 – Ivan Borgman demonstrates that X-rays and salt is clearly visible. radioactive materials induce thermoluminescence.

1 2 2 20TH CENTURY

• 1899 to 1903 – Ernest Rutherford investigates ra- Curie share the 1903 in for their dioactivity and coins the terms alpha and beta rays work on spontaneous radioactivity. in 1899 to describe the two distinct types of radi- • ation emitted by thorium and uranium salts. With 1904 – Richard Abegg notes the pattern that the nu- Frederick Soddy he discovers merical difference between the maximum positive as radioactive thorium is convertd itself into radium valence, such as +6 for H2SO4, and the maximum through a process of nuclear decay and a gas (later negative valence, such as −2 for H2S, of an element found to be 4 tends to be eight (Abegg’s rule). [5] 2He). He also invents the nuclear atom model and • 1905 – explains the photoelectric ef- [6] becomes known as the “father of " fect. He postulates that light itself consists of indi- vidual quantum particles (). 2 20th century • 1905 – Einstein explains the effects of Brownian as caused by the kinetic energy (i.e., move- ment) of , which was subsequently, experi- 2.1 1900–1909 mentally verified by , thereby settling the century-long dispute about the validity of John 's . • 1905 – Einstein publishes his Special Theory of Rel- ativity. • 1905 – Einstein theoretically derives the equivalence of and energy. • 1907 to 1917 – To test his planetary model of 1904 [7] he sent a beam of positively charged alpha particles onto a gold foil and noticed that some bounced back, thus showing that an atom has a small-sized positively charged at its center. However, he received in 1908 the “for his investigations into the chemistry of radioactive substances”,[8] which fol- lowed on the work of Marie Curie, not for his plan- etary model of the atom; he is also widely cred- ited with first “splitting the atom” in 1917. In 1911 Ernest Rutherford explained the Geiger–Marsden experiment by invoking a nuclear atom model and derived the Rutherford . • 1909 – Geoffrey Ingram Taylor demonstrates that interference patterns of light were generated even when the light energy introduced consisted of only Einstein, in 1905, when he wrote the Annus Mirabilis papers one . This discovery of the –particle du- ality of matter and energy is fundamental to the later development of quantum field theory. • 1900 – To explain black-body radiation (1862), • suggests that electromagnetic energy is 1909 and 1916 – Einstein shows that, if Planck’s emitted in quantized form, in multiples of the ele- law of black-body radiation is accepted, the energy mentary unit E = hν, where h is Planck’s constant quanta must also carry momentum p = h / λ. and ν is frequency.

• 1902 – To explain the octet rule (1893), Gilbert N. 2.2 1910–1919 Lewis develops the "cubical atom" theory in which • in the form of dots are positioned at the 1911 – and perform an ex- corner of a cube. Predicts that single, double, or periment that shows that the energies of electrons triple "bonds" result when two atoms are held to- emitted by had a continuous rather than gether by multiple pairs of electrons between the discrete spectrum, in apparent contradiction to the atoms. law of conservation of energy. A second problem is that the of the -14 atom was 1, in con- • 1903 – Antoine Becquerel, and Marie tradiction to the Rutherford prediction of ½. These 2.3 1920–1929 3

• 1915 – Einstein presents what are now known as the Einstein field equations, associated with the General Theory of Relativity.

• 1916 – Paul Epstein[11] and Karl Schwarzschild,[12] working independently, derive equations for the lin- ear and quadratic Stark effect in hydrogen.

• 1916 – To account for the Zeeman effect, suggests electrons in an atom might be “elliptical orbits” in addition to “spherical orbits”.

• 1918 – Sir Ernest Rutherford notices that, when alpha particles are shot into nitrogen gas, his scintillation detectors shows the signatures of A schematic diagram of the apparatus for Millikan’s refined oil hydrogen nuclei. Rutherford determines that the drop experiment. only place this hydrogen could have come from was the nitrogen, and therefore nitrogen must contain hydrogen nuclei. He thus suggests that the hydro- anomalies are later explained by the discoveries of gen nucleus, which is known to have an atomic num- the neutrino and the . ber of 1, is an , which he decides • 1911 – Ștefan Procopiu performs experiments in must be the hypothesized by Eugen Gold- which he determines the correct value of electron’s stein. magnetic dipole moment. In 1913 he is also calcu- • 1919 – Building on the work of Lewis (1916), Irving lated a theoretical value of the Bohr magneton based Langmuir coins the term “covalence” and postulates on Planck’s quantum theory. that coordinate covalent bonds occur when two elec- • 1912 – Victor Hess discovers the existence of trons of a pair of atoms come from both atoms and cosmic radiation. are equally shared by them, thus explaining the fun- damental of chemical bonding and molecular • 1913 – Andrews Millikan publishes the re- chemistry. sults of his “oil drop” experiment that measures the charge of the electron. This makes it possible to cal- culate the and the atomic weight 2.3 1920–1929 of the atoms.

• 1913 – Ștefan Procopiu publishes a theoretical pa- per with the correct value of the electron’s magnetic dipole moment.B.[9]

• 1913 – theoretically obtains the value of the electron’s magnetic dipole moment.

• 1913 – and Antonino Lo Surdo in- dependently discover the shifting and splitting of the spectral lines of atoms and molecules due to an ex- ternal static electric field.

• 1913 – To explain the Rydberg formula (1888), which calculates the emission spectra of atomic hy- drogen, Bohr hypothesizes that electrons revolve around a positively charged nucleus at certain fixed A plaque at the University of commemorating the “quantum” distances, with specific energies such Stern–Gerlach experiment. that transition between orbits requires “quantum” emissions or absorptions of energy. • 1922 – finds that X-ray wave- • 1914 – and Gustav Hertz conduct lengths increase due to scattering of the radiant en- an experiment on electron collisions with mercury ergy by free electrons. This discovery, known as the atoms, that provides new verification of Bohr’s Compton effect, demonstrates the particle concept model of quantized atomic energy levels.[10] of electromagnetic radiation. 4 2 20TH CENTURY

• 1922 – and perform • 1926 – discovers the spin-statistics the Stern–Gerlach experiment, which detects dis- theorem connection. crete values of for atoms in • the ground state passing through an inhomogeneous 1926 – introduces Fermi–Dirac statistics. magnetic field leading to the discovery of the spin of • 1926 – Erwin Schrödinger uses De Broglie’s elec- the electron. tron wave postulate (1924) to develop a "wave equa- tion" that represents mathematically the distribution • 1922 – Bohr updates his model of the atom to bet- of electron charge density throughout space, and ter explain the properties of the periodic table by also introduces the Hamiltonian operator in quan- assuming that certain numbers of electrons (for ex- tum mechanics. ample 2, 8 and 18) corresponded to stable “closed shells”, presaging orbital theory. • 1926 – Paul Epstein reconsiders the linear and quadratic Stark effect using Schrödinger’s equation. • 1923 – Pierre Auger discovers the Auger effect, The derived equations for the line intensities are a where filling the inner-shell vacancy of an atom is decided improvement over previous results obtained accompanied by the emission of an electron from by .[13] the same atom. • 1927 – formulates the quantum • 1923 – extends wave–particle du- .[1] ality to particles, postulating that electrons in mo- tion are associated with waves. He predicts that the • 1927 – develops the inter- wavelength, λ = h / p , where p is momentum and h pretation of the probabilistic nature of wavefunc- is Planck’s constant.[1] tions.

• 1923 – Gilbert N. Lewis creates the theory of Lewis • 1927 – Born and J. Robert Oppenheimer introduce acids and bases based on the properties of electrons the Born–Oppenheimer approximation, which al- in molecules, defining an acid as accepting an elec- lows the quick approximation of the energy and tron lone pair from a base. wavefunctions of smaller molecules.

• 1924 – explains Planck’s law • 1927 – and Fritz London introduce using a new statistical law that governs bosons, and the concepts of valence bond theory and apply it to Einstein generalizes it to predict Bose–Einstein con- the hydrogen molecule. densate. The theory is now known as Bose–Einstein • 1927 – Thomas and Fermi develop the Thomas– statistics.[1] Fermi model for a Gas in a box. • 1924 – outlines the "Pauli exclu- • 1927 – Chandrasekhara Venkata Raman studies op- sion principle" which states that no two identical tical photon scattering by electrons. fermions may occupy the same simul- taneously, a fact that explains many features of the • 1927 – Dirac states his relativistic electron quantum periodic table.[1] wave equation, the , in the same year Charles G. Darwin and Walter Gordon solve it for a • 1925 – and Coulomb potential. postulate the existence of electron spin.[1] • 1927 – Charles Drummond Ellis (along with James • 1925 – Friedrich Hund outlines Hund’s rule of Max- Chadwick and colleagues) finally establish clearly imum Multiplicity which states that when electrons that the beta decay spectrum is in fact continuous are added successively to an atom as many lev- and not discrete, posing a problem that will later be els or orbits are singly occupied as possible before solved by theorizing (and later discovering) the ex- any pairing of electrons with opposite spin occurs istence of the neutrino. and made the distinction that the inner electrons in molecules remained in atomic orbitals and only the • 1927 – Walter Heitler uses Schrödinger’s wave valence electrons needed to be in molecular orbitals equation to show how two hydrogen atom involving both nuclei. wavefunctions join together, with plus, minus, and exchange terms, to form a covalent bond. • 1925 – Werner Heisenberg, Max Born, and Pascual Jordan develops the formulation • 1927 – Robert Mulliken works, in coordination with of Quantum Mechanics.[1] Hund, to develop a molecular orbital theory where electrons are assigned to states that extend over an • 1926 – and Walter Gordon put forth a entire molecule and, in 1932, introduces many new relativistic quantum wave equation now called the molecular orbital terminologies, such as σ bond, π Klein–Gordon equation. bond, and δ bond. 2.4 1930–1939 5

• 1927 – relates degeneracies of quan- tum states to irreducible representations of symme- try groups.

• 1928 – outlines the nature of the chemical bond: uses Heitler’s quantum mechanical covalent bond model to outline the quantum me- chanical basis for all types of molecular structure and bonding and suggests that different types of bonds in molecules can become equalized by rapid shifting of electrons, a process called "resonance" (1931), such that resonance hybrids contain contri- butions from the different possible electronic con- figurations.

• 1928 – Friedrich Hund and Robert S. Mulliken in- troduce the concept of molecular orbitals.

• 1928 – Born and Vladimir Fock formulate and prove the adiabatic theorem, which states that a physical system shall remain in its instantaneous eigenstate if a given perturbation is acting on it slowly enough and if there is a gap between the eigenvalue and the rest of the Hamiltonian's spectrum.

• 1929 – Fritz Houtermans and Robert d'Escourt Atkinson propose that stars release energy by nu- clear fusion.[1]

2.4 1930–1939

• 1930 – Dirac hypothesizes the existence of the Electron microscope constructed by in 1933. positron.[1] • 1931 – creates the first • 1930 – Fritz London explains van der Waals forces and founds the Radiation Laboratory, later the as due to the interacting fluctuating dipole moments Lawrence Berkeley National Laboratory; in 1939 he between molecules awarded the for his work on the cyclotron. • 1930 – Pauli suggests that, in addition to electrons and protons, atoms also contain an extremely light • 1932 – establishes that the radi- neutral particle which is later called the neutrino.[1] ation emitted when Beryllium is bombarded by al- pha particles the resulting radiation consists of the • 1931 – John Lennard-Jones proposes the Lennard- that were hypothesized by Fermi.[1] Jones interatomic potential • 1932 – : Building upon the nu- • 1931 – and Herbert Becker find that clear transmutation experiments of Ernest Ruther- if the very energetic alpha particles emitted from ford done a few years earlier, observes fusion of light fall on certain light elements, specifically nuclei (hydrogen ). The steps of the main beryllium, boron, or , an unusually penetrat- cycle of in stars are subsequently ing radiation is produced. At first this radiation is worked out by over the next decade. thought to be gamma radiation, although it is more • penetrating than any gamma rays known, and the 1932 – Carl D. Anderson experimentally proves the [1] details of experimental results are very difficult to existence of the positron. interpret on this basis. Some scientists begin to hy- • 1933 – Leó Szilárd first theorizes the concept of a pothesize the possible existence of another funda- nuclear chain reaction. He files a patent for his idea mental particle. of a simple the following year. • 1931 – Ernst Ruska creates the first electron micro- • 1934 – Fermi studies the effects of bombarding scope.[1] uranium isotopes with neutrons. 6 2 20TH CENTURY

• 1935 – Einstein, , and • 1942 to 1946 – J. Robert Oppenheimer successfully describe the EPR paradox which challenges the the , predicts quantum tun- completeness of quantum mechanics as it was theo- neling and proposes the Oppenheimer–Phillips pro- rized up to that time. Assuming that local realism cess in nuclear fusion The first nuclear fission explo- is valid, they demonstrated that there would need sion was produced on July 16, 1945 in the to be hidden parameters to explain how measuring test in . the quantum state of one particle could influence the • quantum state of another particle without apparent 1946 – Theodor V. Ionescu and Vasile Mihu re- contact between them.[14] port the construction of the first hydrogen maser by stimulated emission of radiation in molecular hydro- • 1935 - Schrödinger develops the Schrödinger’s cat gen. . It illustrates what he saw as the • 1947 – and measure problems of the Copenhagen interpretation of quan- a small difference in energy between the energy lev- tum mechanics if subatomic particles can be in two els 2S₁/₂ and 2P₁/₂ of the hydrogen atom, known as contradictory quantum states at once. the .

• 1935 – formulates his hypothesis of • 1947 – George Rochester and Clifford Charles But- the Yukawa potential and predicts the existence of ler publishes two photographs of cos- the , stating that such a potential arises from the mic ray-induced events, one showing what appears exchange of a massive scalar field, as it would be to be a neutral particle decaying into two charged found in the field of the pion. Prior to Yukawa’s , and one that appears to be a charged parti- paper, it was believed that the scalar fields of the cle decaying into a charged pion and something neu- fundamental forces necessitated massless particles. tral. The estimated mass of the new particles is very rough, about half a ’s mass. More examples • 1936 – publishes prior to Hideki of these “V-particles” were slow in coming, and they Yukawa his relativistic quantum field equations for are soon given the name kaons. a massive vector of spin−1 as a basis for nuclear forces. • 1948 – Sin-Itiro Tomonaga and In- dependently introduce perturbative • 1937 – Carl Anderson experimentally proves the ex- as a method of correcting the original Lagrangian of istence of the pion. a quantum field theory so as to eliminate a series of infinite terms that would otherwise result. • 1938 – Charles Coulson makes the first accurate cal- culation of a molecular orbital wavefunction with the • 1948 – states the path integral for- hydrogen molecule. mulation of quantum mechanics. • • 1938 – Otto Hahn and his assistant Fritz Strassmann 1949 – determines the equiva- send a manuscript to Naturwissenschaften reporting lence of two formulations of quantum electrody- they have detected the element barium after bom- namics: Feynman’s diagrammatic path integral for- barding uranium with neutrons. Hahn calls this new mulation and the operator method developed by phenomenon a 'bursting' of the uranium nucleus. Si- Julian Schwinger and Tomonaga. A by-product of multaneously, Hahn communicate these results to that demonstration is the invention of the Dyson se- [15] Lise Meitner. Meitner, and her nephew Otto Robert ries. Frisch, correctly interpret these results as being a nuclear fission. Frisch confirms this experimentally 2.6 1950–1959 on 13 January 1939. • 1951 – Clemens C. J. Roothaan and George G. Hall • 1939 – Leó Szilárd and Fermi discover neutron mul- derive the Roothaan-Hall equations, putting rigor- tiplication in uranium, proving that a chain reaction ous molecular orbital methods on a firm basis. is indeed possible. • 1951 – 1952 , and “father of the hydrogen bomb”, and , math- 2.5 1940–1949 ematician, are reported to have written jointly in March 1951 a classified report on “Hydrodynamic • 1942 – A team led by Enrico Fermi creates the Lenses and Radiation Mirrors” that results in the first artificial self-sustaining nuclear chain reaction, next step in the Manhattan Project.[16] The first called Chicago Pile-1, in a racquets court below the planned fusion thermonuclear reaction experiment bleachers of Stagg Field at the is carried out successfully in the Spring of 1951 on December 2, 1942. based on the work Hans A. Bethe and others.[17] 2.7 1960–1969 7

In November 1952 full-scale test of the Hydrogen 2.7 1960–1969 bomb is apparently carried out. • 1951 – and re- ceive a shared Nobel Prize in Physics for their first observations of the quantum phenomenon of nuclear magnetic resonance previously reported in 1949.[18][19][20] Purcell reports his contribution as Research in Nuclear , and gives credit to his coworkers such as Herbert S. Gutowsky for their NMR contributions,[21][22] as well as theoretical re- searchers of nuclear magnetism such as John Has- brouck Van Vleck. • 1952 – Donald A. Glaser creates the bubble cham- ber, which allows detection of electrically charged particles by surrounding them by a bubble. Proper- ties of the particles such as momentum can be de- The baryon decuplet of the Eightfold Way proposed by Murray termined by studying of their helical paths. Glaser Gell-Mann in 1962. The Ω− particle at the bottom had not yet receives a Nobel prize in 1960 for his invention. been observed at the time, but a particle closely matching these predictions was discovered[23] by a group at • 1953 – Charles H. Townes, collaborating with James Brookhaven, proving Gell-Mann’s theory. P. Gordon, and H. J. Zeiger, builds the first ammonia maser; receives a Nobel prize in 1964 for his exper- imental success in producing coherent radiation by • 1961 – Clauss Jönsson performs Young’s double-slit atoms and molecules. experiment (1909) for the first time with particles other than photons by using electrons and with simi- • 1954 – Chen Ning Yang and Robert Mills derive a lar results, confirming that massive particles also be- for nonabelian groups, leading to the haved according to the wave–particle duality that is successful formulation of both electroweak unifica- a fundamental principle of quantum field theory. tion and quantum chromodynamics. • 1961 – extends the • 1955 and 1956 – Murray Gell-Mann and Kazuhiko electroweak interaction modelss developed by Nishijima independently derive the Gell-Mann– Julian Schwinger by including a short range neutral Nishijima formula, which relates the baryon num- current, the Z_o. The resulting symmetry structure ber, the strangeness, and the isospin of hadrons to that Glashow proposes, SU(2) X U(1), forms the the charge, eventually leading to the systematic cat- basis of the accepted theory of the electroweak egorization of hadrons and, ultimately, the interactions. Model of hadron composition. • • 1956 – Chien-Shiung Wu carries out the Wu Exper- 1962 – Leon M. Lederman, and iment, which observes violation in cobalt-60 show that more than one type of decay, showing that parity violation is present in the neutrino exists by detecting interactions of the muon weak interaction. neutrino (already hypothesised with the name “neu- tretto”) • 1956 – Clyde L. Cowan and ex- • perimentally prove the existence of the neutrino. 1962 – Murray Gell-Mann and Yuval Ne'eman inde- pendently classify the hadrons according to a system • 1957 – , and John Robert that Gell-Mann called the Eightfold Way, and which Schrieffer propose their quantum BCS theory of low ultimately led to the quark model (1964) of hadron temperature superconductivity, for which their re- composition. ceive a Nobel prize in 1972. The theory represents superconductivity as a macroscopic quantum coher- • 1963 – Nicola Cabibbo develops the mathematical ence phenomenon involving phonon coupled elec- matrix by which the first two (and ultimately three) tron pairs with opposite spin generations of can be predicted. • 1957 – William , , • 1964 – Murray Gell-Mann and George Zweig inde- Geoffrey Burbidge, and , in their 1957 pendently propose the quark model of hadrons, pre- paper Synthesis of the Elements in Stars, show that dicting the arbitrarily named up, down, and strange the abundances of essentially all but the lightest quarks. Gell-Mann is credited with coining the chemical elements can be explained by the process term quark, which he found in James Joyce's book of in stars. Finnegans Wake. 8 3 21ST CENTURY

• 1964 – François Englert, , , Gerald Guralnik, C. R. Hagen, and Tom Kibble postulate that a fundamental quantum field, now called the Higgs field, permeates space and, by way of the , provides mass to all the elementary subatomic particles that interact with it. While the Higgs field is postulated to confer mass on quarks and leptons, it represents only a tiny portion of the masses of other subatomic parti- cles, such as protons and neutrons. In these, gluons that bind quarks together confer most of the parti- cle mass. The result is obtained independently by three groups: François Englert and Robert Brout; Peter Higgs, working from the ideas of Philip An- A 1974 photograph of an event in a bubble chamber at Brookhaven National Laboratory. Each track is left by a derson; and Gerald Guralnik, C. R. Hagen, and Tom [24][25][26][27][28][29][30] charged particle, one of which is a baryon containing the charm Kibble. quark.[31]

• 1964 – Sheldon Lee Glashow and 2.8 1971–1999 predict the existence of the . The addition is proposed because it allows for a bet- • 1973 – Peter Mansfield formulates the physical ter description of the weak interaction (the mech- theory of Nuclear magnetic resonance imaging anism that allows quarks and other particles to de- (NMRI)[32][33][34][35] cay), equalizes the number of known quarks with • 1974 – Pier Giorgio Merli performs Young’s double- the number of known leptons, and implies a mass slit experiment (1909) using a single electron with formula that correctly reproduced the masses of the similar results, confirming the existence of quantum known . fields for massive particles.

• • 1964 – puts forth Bell’s theorem, 1980 to 1982 – verify experimentally which used testable inequality relations to show the the hypothesis; his flaws in the earlier Einstein–Podolsky–Rosen para- experiments provide strong evidence that a quantum dox and prove that no physical theory of local hidden event at one location can affect an event at another location without any obvious mechanism for com- variables can ever reproduce all of the predictions of [36][37] quantum mechanics. This inaugurated the study of munication between the two locations. quantum entanglement, the phenomenon in which • 1986 – Johannes and Karl Alexan- separate particles share the same quantum state de- der Müller produce unambiguous experimental spite being at a distance from each other. proof of high temperature superconductivity involv- ing Jahn-Teller polarons in orthorhombic La2CuO4, YBCO and other perovskite-type oxides; promptly • 1968 – : Deep inelastic scatter- receive a Nobel prize in 1987 and deliver their No- ing experiments at the Stanford Linear Accelera- bel lecture on December 8, 1987.[38] tor Center (SLAC) show that the proton contains much smaller, point-like objects and is therefore • 1977 to 1995 – The top quark is finally observed not an elementary particle. at the time by a team at Fermilab after an 18-year search. It are reluctant to identify these objects with quarks, has a mass much greater than had been previously instead calling them partons — a term coined by expected — almost as great as a gold atom. Richard Feynman. The objects that are observed • 1998 – The Super-Kamiokande (Japan) detector fa- at SLAC will later be identified as up and down cility reports experimental evidence for neutrino os- quarks. Nevertheless, “parton” remains in use as cillations, implying that at least one neutrino has a collective term for the constituents of hadrons mass. (quarks, antiquarks, and gluons). The existence of the strange quark is indirectly validated by the SLAC’s scattering experiments: not only is it a nec- essary component of Gell-Mann and Zweig’s three- 3 21st century quark model, but it provides an explanation for the kaon (K) and pion (π) hadrons discovered in cosmic • 2001 – the Sudbury Neutrino Observatory (Canada) rays in 1947. confirm the existence of neutrino oscillations. Lene 9

[10] Pais, Abraham (1995). “Introducing Atoms and Their Nuclei”. In Brown, Laurie M.; Pais, Abraham; Pippard, Brian. Twentieth Century Physics 1. American Institute of Physics Press. p. 89. ISBN 9780750303101. Now the beauty of Franck and Hertz’s work lies not only in the measurement of the energy loss E2-E1 of the impinging electron, but they also observed that, when the energy of that electron exceeds 4.9 eV, mercury begins to emit ul- traviolet light of a definite frequency ν as defined in the above formula. Thereby they gave (unwittingly at first) the first direct experimental proof of the Bohr relation!

[11] P. S. Epstein, Zur Theorie des Starkeffektes, Annalen der Physik, vol. 50, pp. 489-520 (1916)

[12] K. Schwarzschild, Sitzungsberichten der Kgl. Preuss. Graphene is a planar atomic-scale honeycomb lattice made of Akad. d. Wiss. April 1916, p. 548 carbon atoms which exhibits unusual and interesting quantum properties. [13] P. S. Epstein, The Stark Effect from the Point of View of Schroedinger’s Quantum Theory, , vol 28, pp. 695-710 (1926) Hau stops a beam of light completely in a Bose– Einstein condensate.[39] [14] Einstein A, Podolsky B, Rosen N; Podolsky; Rosen (1935). “Can Quantum-Mechanical Description of Phys- • 2009 - Aaron D. O'Connell invents the first quantum ical Reality Be Considered Complete?". Phys. Rev. machine, applying quantum mechanics to a macro- 47 (10): 777–780. Bibcode:1935PhRv...47..777E. scopic object just large enough to be seen by the doi:10.1103/PhysRev.47.777. naked eye, which is able to vibrate a small amount and large amount simultaneously. [15] Dyson, F. (1949). “The S Matrix in Quan- tum Electrodynamics”. Phys. Rev. 75 • 2014 – Scientists transfer data by quantum tele- (11): 1736. Bibcode:1949PhRv...75.1736D. portation over a distance of 10 feet with zero per- doi:10.1103/PhysRev.75.1736. cent error rate, a vital step towards a quantum internet.[40][41] [16] Stix, Gary (October 1999). “Infamy and honor at the Atomic Café: Edward Teller has no regrets about his con- tentious career”. Scientific American: 42–43. Retrieved 4 References April 2012. [17] Hans A. Bethe (May 28, 1952). MEMORANDUM [1] Peacock 2008, pp. 175–183 ON THE HISTORY OF THERMONUCLEAR PRO- GRAM (Report). Reconstructed version from only par- [2] Ben-Menahem 2009 tially declassified documents, with certain words deliber- [3] Becquerel, Henri (1896). “Sur les radiations émises par ately deleted. phosphorescence”. Comptes Rendus 122: 420–421. [18] Bloch, F.; Hansen, W.; Packard, Martin [4] Marie Curie and the Science of Radioactivity: Research (1946). “Nuclear Induction”. Physical Review Breakthroughs (1897–1904). Aip.org. Retrieved on 69 (3–4): 127. Bibcode:1946PhRv...69..127B. 2012-05-17. doi:10.1103/PhysRev.69.127. [5] Frederick Soddy (December 12, 1922). “The origins [19] Bloch, F.; Jeffries, C. (1950). “A Direct Deter- of the conceptions of isotopes” (PDF). Nobel Lecture in mination of the Magnetic Moment of the Pro- Chemistry. Retrieved April 2012. ton in Nuclear Magnetons”. Physical Review [6] Ernest Rutherford, Baron Rutherford of Nelson, of Cam- 80 (2): 305. Bibcode:1950PhRv...80..305B. bridge. Encyclopædia Britannica on-line. Retrieved on doi:10.1103/PhysRev.80.305. 2012-05-17. [20] Bloch, F. (1946). “Nuclear Induction”. Physical Re- [7] later known as the view 70 (7–8): 460. Bibcode:1946PhRv...70..460B. [8] The Nobel Prize in Chemistry 1908: Ernest Rutherford. doi:10.1103/PhysRev.70.460. nobelprize.org [21] Gutowsky, H. S.; Kistiakowsky, G. B.; Pake, G. E.; [9] Ştefan Procopiu. 1913. “Determining the Molecular Purcell, E. M. (1949). “Structural Investigations by Magnetic Moment by M. Planck’s Quantum Theory”. Means of Nuclear Magnetism. I. Rigid Crystal Lat- Bulletin scientifique de l'Académie Roumaine de sciences., tices”. The Journal of Chemical Physics 17 (10): 972. 1:151. Bibcode:1949JChPh..17..972G. doi:10.1063/1.1747097. 10 4 REFERENCES

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