Timelines of Events in Science, Mathematics, and Technology
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Biology and Organic Chemistry
Medicine and Medical Technology
General Technology
Pure and Applied Mathematics
Geology
Geography, Meteorology, Paleontology, Science Philosophy and Publishing
Agriculture and Food Technology
Clothing and Textiles Technology
Motor and Engine Technology
Transportation Technology
Underwater Technology
Communication Technology
Photography Technology
Calculator and Computer Technology
Time Measurement Technology
Temperature and Pressure Measurement Technology
Microscope Technology
Low Temperature Technology
Rocket and Missile Technology
Materials Technology
Lighting Technology
Classical Mechanics
Electromagnetism and Classical Optics
Thermodynamics, Statistical Mechanics, and Random Processes
States of Matter and Phase Transitions
Quantum Mechanics, Molecular, Atomic, Nuclear, and Particle Physics
Particle Physics Technology
Gravitational Physics and Relativity
Black Hole Physics
Cosmology
Cosmic Microwave Background Astronomy
Other Background Radiation Fields
Galaxies, Clusters of Galaxies, and Large Scale Structures
The Interstellar Medium and Intergalactic Medium
White Dwarfs, Neutron Stars, and Supernovae
Stellar Astronomy
Solar Astronomy
Solar System Astronomy
Astronomical Maps, Catalogs, and Surveys
Telescopes, Observatories, and Observing Technology
Artificial Satellites and Space Probes

Classical Mechanics

-260  Archimedes mathematically works out the principle of the lever and discovers the principle of buoyancy
60    Hero of Alexandria writes {\sevenit Metrica}, {\sevenit Mechanics}, and {\sevenit Pneumatics}
1490  Leonardo da Vinci describes capillary action
1581  Galileo Galilei notices the timekeeping property of the pendulum
1589  Galileo Galilei uses balls rolling on inclined planes to show that different weights fall with the same acceleration
1638  Galileo Galilei publishes {\sevenit Dialogues Concerning Two New Sciences}
1658  Christian Huygens experimentally discovers that balls placed anywhere inside an inverted cycloid reach the lowest point of the
cycloid in the same time and thereby experimentally shows that the cycloid is the isochrone
1668  John Wallis suggests the law of conservation of momentum
1687  Isaac Newton publishes his {\sevenit Principia Mathematica}
1690  James Bernoulli shows that the cycloid is the solution to the isochrone problem
1691  Johann Bernoulli shows that a chain freely suspended from two points will form a catenary
1691  James Bernoulli shows that the catenary curve has the lowest center of gravity that any chain hung from two fixed points can have
1696  Johann Bernoulli shows that the cycloid is the solution to the brachistochrone problem
1714  Brook Taylor derives the fundamental frequency of a stretched vibrating string in terms of its tension and mass per unit length
by solving an ordinary differential equation
1733  Daniel Bernoulli derives the fundamental frequency and harmonics of a hanging chain by solving an ordinary differential equation
1734  Daniel Bernoulli solves the ordinary differental equation for the vibrations of an elastic bar clamped at one end
1738  Daniel Bernoulli examines fluid flow in {\sevenit Hydrodynamica}
1739  Leonhard Euler solves the ordinary differential equation for a forced harmonic oscillator and notices the resonance phenomenon
1742  Colin Maclaurin discovers his uniformly rotating self-gravitating spheroids
1747  Pierre-Louis Moreau de Maupertuis applies minimum principles to mechanics
1759  Leonhard Euler solves the partial differential equation for the vibration of a rectangular drum
1764  Leonhard Euler examines the partial differential equation for the vibration of a circular drum and finds one of the Bessel
function solutions
1788  Joseph Lagrange presents Lagrange's equations of motion in {\sevenit M\'ecanique Analytique}
1789  Antoine Lavoisier states the law of conservation of mass
1821  William Hamilton begins his analysis of Hamilton's characteristic function
1834  Carl Jacobi discovers his uniformly rotating self-gravitating ellipsoids
1834  John Russell observes a nondecaying solitary water wave in the Union Canal near Edinburgh and uses a water tank to study the dependence
of solitary water wave velocities on wave amplitude and water depth
1835  William Hamilton states Hamilton's canonical equations of motion
1835  Gaspard de Coriolis examines motion on a spinning surface deduces the Coriolis effect
1842  Christian Doppler examines the Doppler shift of sound
1847  Hermann Helmholtz formally states the law of conservation of energy
1851  Jean-Bernard Foucault shows the Earth's rotation with a huge pendulum
1902  James Jeans finds the length scale required for gravitational pertrubatations to grow in a static nearly homogeneous medium

Electromagnetism and Classical Optics

130   Claudius Ptolemaeus tabulates angles of refraction for several media
1269  P\elerin de Maricourt describes magnetic poles and remarks on the nonexistence of isolated magnetic poles
1305  Dietrich von Freiberg uses crystalline spheres and flasks filled with water to study the reflection and refraction in raindrops that
leads to primary and secondary rainbows
1604  Johannes Kepler describes how the eye focuses light
1611  Marko Dominis discusses the rainbow in {\sevenit De Radiis Visus et Lucis}
1611  Johannes Kepler discovers total internal reflection, a small angle refraction law, and thin lens optics
1621  Willebrord Snell states his law of refraction
1637  Ren\'e Descartes quantitatively derives the angles at which primary and secondary rainbows are seen with respect to the angle of the
Sun's elevation
1657  Pierre de Fermat introduces the principle of least time into optics
1678  Christian Huygens states his principle of wavefront sources
1704  Isaac Newton publishes {\sevenit Opticks}
1728  James Bradley discovers the aberration of starlight and uses it to determine that the speed of light is about 283,000 km/s
1752  Benjamin Franklin shows that lightning is electricity
1767  Joseph Priestly proposes an electrical inverse-square law
1785  Charles Coulomb introduces the inverse-square law of electrostatics
1786  Luigi Galvani discovers animal electricity'' and postulates that animal bodies are storehouses of electricity
1800  William Herschel discovers infrared radiation from the Sun
1801  Johann Ritter discovers ultraviolet radiation from the Sun
1801  Thomas Young demonstrates the wave nature of light and the principle of interference
1808  \'Etienne Malus discovers polarization by reflection
1809  \'Etienne Malus publishes the law of Malus which predicts the light intensity transmitted by two polarizing sheets
1811  Fran\c cois Arago discovers that some quartz crystals will continuously rotate the electric vector of light
1816  David Brewster discovers stress birefringence
1818  Sim\'eon Poisson predicts the Poisson bright spot at the center of the shadow of a circular opaque obstacle
1818  Fran\c cois Arago verifies the existence of the Poisson bright spot
1820  Hans Oersted notices that a current in a wire can deflect a compass needle
1825  Augustin Fresnel phenomenologically explains optical activity by introducing circular birefringence
1826  Simon Ohm states his law of electrical resistance
1831  Michael Faraday states his law of induction
1833  Heinrich Lenz states that an induced current in a closed conducting loop will appear in such a direction that it opposes the change that
produced it
1845  Michael Faraday discovers that light propagation in a material can be influenced by external magnetic fields
1849  Armand Fizeau and Jean-Bernard Foucault measure the speed of light to be about 298,000 km/s
1852  George Stokes defines the Stokes parameters of polarization
1864  James Clerk Maxwell publishes his papers on a dynamical theory of the electromagnetic field
1871  Lord Rayleigh discusses the blue sky law and sunsets
1873  James Clerk Maxwell states that light is an electromagnetic phenomenon
1875  John Kerr discovers the electrically induced birefringence of some liquids
1888  Heinrich Hertz discovers radio waves
1895  Wilhelm R\"ontgen discovers X-rays
1896  Arnold Sommerfeld solves the half-plane diffraction problem
1956  R. Hanbury-Brown and R.Q. Twiss complete the correlation interferometer

Thermodynamics, Statistical Mechanics, and Random Processes

1761  Joseph Black discovers that ice absorbs heat without changing temperature when melting
1798  Count Rumford has the idea that heat is a form of energy
1822  Joseph Fourier formally introduces the use of dimensions for physical quantities in his {\sevenit Theorie Analytique de la Chaleur}
1824  Sadi Carnot scientifically analyzes the efficiency of steam engines
1827  Robert Brown discovers the Brownian motion of pollen and dye particles in water
1834  Benoit-Pierre Clapeyron presents a formulation of the second law of thermodynamics
1843  James Joule experimentally finds the mechanical equivalent of heat
1848  Lord Kelvin discovers the absolute zero point of temperature
1852  James Joule and Lord Kelvin demonstrate that a rapidly expanding gas cools
1859  James Clerk Maxwell discovers the distribution law of molecular velocities
1870  Rudolph Clausius proves the scalar virial theorem
1872  Ludwig Boltzmann states the Boltzmann equation for the temporal development of distribution functions in phase space
1874  Lord Kelvin formally states the second law of thermodynamics
1876  Josiah Gibbs begins a two-year long series of papers which discusses phase equilibria, the free energy as the driving force behind chemical
reactions, and chemical thermodynamics in general
1879  Josef Stefan observes that the total radiant flux from a blackbody is proportional to the fourth power of its temperature
1884  Ludwig Boltzmann derives the Stefan-Boltzmann blackbody radiant flux law from thermodynamic considerations
1888  Henri-Louis Le Ch\^atelier states that the response of a chemical system perturbed from equilbrium will be to counteract the perturbation
1893  Wilhelm Wien discovers the displacement law for a blackbody's maximum specific intensity
1905  Albert Einstein mathematically analyzes the Brownian motion
1906  Walther Nernst presents a formulation of the third law of thermodynamics
1910  Albert Einstein and Marian Smoluchowski find the Einstein-Smoluchowski formula for the attenuation coefficient due to density
fluctuations in a gas
1916  Sydney Chapman and David Enskog systematically develop a kinetic theory of gases
1919  James Jeans discovers that the dynamical constants of motion determine the distribution function for a system of particles
1920  Meghnad Saha states his ionization equation
1923  Pieter Debye and Erich H\"uckel publish a statistical treatment of the dissociation of electrolytes
1928  J.B. Johnson discovers Johnson noise in a resistor
1928  Harry Nyquist derives the fluctuation-dissipation relationship for a resistor to explain Johnson noise
1942  J.L. Doob states his theorem on Gaussian-Markoff processes
1957  A.S. Kompaneets derives his Compton scattering Fokker-Planck equation

States of Matter and Phase Transitions

1895  Pierre Curie discovers that induced magnetization is proportional to magnetic field strength
1911  Heike Kammerlingh Onnes discovers superconductivity
1912  Pieter Debye derives the T-cubed law for the low temperature heat capacity of a nonmetallic solid
1925  Ernst Ising presents the solution to the one-dimensional Ising model and models ferromagnetism as a cooperative spin phenomenon
1933  Walter Meissner and R. Ochsenfeld discover perfect superconducting diamagnetism
1942  Hannes Alfv\'en predicts magnetohydrodynamic waves in plasmas
1944  Lars Onsager publishes the exact solution to the two-dimensional Ising model
1957  John Bardeen, Leon Cooper, and Robert Schrieffer develop the BCS theory of superconductivity
1958  Rudolf M\"ossbauer finds the M\"ossbauer crystal recoil effect
1972  Douglas Osheroff, Robert Richardson, and David Lee discover that helium-3 can become a superfluid
1974  Kenneth Wilson develops the renormalization group technique for treating phase transitions
1987  Alex M\"uller and Georg Bednorz discover high critical temperature ceramic superconductors

Quantum Mechanics, Molecular Physics, Atomic Physics, Nuclear Physics, and Particle Physics

-440  Democritus speculates about fundamental indivisible particles---calls them atoms''
1766  Henry Cavendish discovers and studies hydrogen
1778  Carl Scheele and Antoine Lavoisier discover that air is composed mostly of nitrogen and oxygen
1781  Joseph Priestly creates water by igniting hydrogen and oxygen
1800  William Nicholson and Anthony Carlisle use electrolysis to separate water into hydrogen and oxygen
1803  John Dalton introduces atomic ideas into chemistry and states that matter is composed of atoms of different weights
1811  Amedeo Avogadro claims that equal volumes of gases should contain equal numbers of molecules
1832  Michael Faraday states his laws of electrolysis
1871  Dmitri Mendeleyev systematically examines the periodic table and predicts the existence of gallium, scandium, and germanium
1873  Johannes van der Waals introduces the idea of weak attractive forces between molecules
1885  Johann Balmer finds a mathematical expression for observed hydrogen line wavelengths
1887  Heinrich Hertz discovers the photoelectric effect
1894  Lord Rayleigh and William Ramsay discover argon by spectroscopically analyzing the gas left over after nitrogen and oxygen are
removed from air
1895  William Ramsay discovers terrestrial helium by spectroscopically analyzing gas produced by decaying uranium
1896  Antoine Becquerel discovers the radioactivity of uranium
1896  Pieter Zeeman studies the splitting of sodium {\sevenit D} lines when sodium is held in a flame between strong magnetic poles
1897  Joseph Thomson discovers the electron
1898  William Ramsay and Morris Travers discover neon, krypton, and xenon
1898  Marie Curie and Pierre Curie isolate and study radium and polonium
1899  Ernest Rutherford discovers that uranium radiation is composed of positively charged alpha particles and negatively charged beta particles
1900  Paul Villard discovers gamma-rays while studying uranium decay
1900  Johannes Rydberg refines the expression for observed hydrogen line wavelengths
1900  Max Planck states his quantum hypothesis and blackbody radiation law
1902  Philipp Lenard observes that maximum photoelectron energies are independent of illuminating intensity but depend on frequency
1902  Theodor Svedberg suggests that fluctuations in molecular bombardment cause the Brownian motion
1905  Albert Einstein explains the photoelectric effect
1906  Charles Barkla discovers that each element has a characteristic X-ray and that the degree of penetration of these X-rays is related to
the atomic weight of the element
1909  Hans Geiger and Ernest Marsden discover large angle deflections of alpha particles by thin metal foils
1909  Ernest Rutherford and Thomas Royds demonstrate that alpha particles are doubly ionized helium atoms
1911  Ernest Rutherford explains the Geiger-Marsden experiment by invoking a nuclear atom model and derives the Rutherford cross section
1912  Max von Laue suggests using lattice solids to diffract X-rays
1912  Walter Friedrich and Paul Knipping diffract X-rays in zinc blende
1913  William Bragg and Lawrence Bragg work out the Bragg condition for strong X-ray reflection
1913  Henry Moseley shows that nuclear charge is the real basis for numbering the elements
1913  Niels Bohr presents his quantum model of the atom
1913  Robert Millikan measures the fundamental unit of electric charge
1913  Johannes Stark demonstrates that strong electric fields will split the Balmer spectral line series of hydrogen
1914  James Franck and Gustav Hertz observe atomic excitation
1914  Ernest Rutherford 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 Lewis and Irving Langmuir formulate an electron shell model of chemical bonding
1917  Albert Einstein introduces the idea of stimulated radiation emission
1921  Alfred Land\'e introduces the Lande g-factor
1922  Arthur Compton studies X-ray photon scattering by electrons
1922  Otto Stern and Walter Gerlach show space quantization''
1923  Louis de Broglie suggests that electrons may have wavelike properties
1924  Wolfgang Pauli states the quantum exclusion principle
1924  John Lennard-Jones proposes a semiempirical interatomic force law
1924  Satyendra Bose and Albert Einstein introduce Bose-Einstein statistics
1925  George Uhlenbeck and Samuel Goudsmit postulate electron spin
1925  Pierre Auger discovers the Auger autoionization process
1925  Werner Heisenberg, Max Born, and Pascual Jordan formulate quantum matrix mechanics
1926  Erwin Schr\"odinger states his nonrelativistic quantum wave equation and formulates quantum wave mechanics
1926  Erwin Schr\"odinger 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
1926  Enrico Fermi discovers the spin-statistics connection
1926  Paul Dirac introduces Fermi-Dirac statistics
1927  Clinton Davission, Lester Germer, and George Thomson confirm the wavelike nature of electrons
1927  Werner Heisenberg states the quantum uncertainty principle
1927  Max Born interprets the probabilistic nature of wavefunctions
1928  Chandrasekhara Raman studies optical photon scattering by electrons
1928  Paul Dirac states his relativistic electron quantum wave equation
1928  Charles G. Darwin and Walter Gordon solve the Dirac equation for a Coulomb potential
1929  Oskar Klein discovers the Klein paradox
1929  Oskar Klein and Y. Nishina derive the Klein-Nishina cross section for high energy photon scattering by electrons
1929  N.F. Mott derives the Mott cross section for the Coulomb scattering of relativistic electrons
1930  Paul Dirac introduces electron hole theory
1930  Erwin Schr\"odinger predicts the {\sevenit zitterbewegung} motion
1930  Fritz London explains van der Waals forces as due to the interacting fluctuating dipole moments between molecules
1931  John Lennard-Jones proposes the Lennard-Jones interatomic potential
1931  Ir\ene Joliot-Curie and Fr\'ed\'eric Joliot-Curie observe but misinterpret neutron scattering in parafin
1931  Wolfgang Pauli puts forth the neutrino 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 shows that charge conservation can be explained if magnetic monopoles exist
1931  Harold Urey discovers deuterium using evaporation concentration techniques and spectroscopy
1932  John Cockcroft and Thomas Walton split lithium and boron nuclei using proton bombardment
1932  James Chadwick discovers the neutron
1932  Werner Heisenberg presents the proton-neutron model of the nucleus and uses it to explain isotopes
1932  Carl Anderson discovers the positron
1933  Max Delbr\"uck suggests that quantum effects will cause photons to be scattered by an external electric field
1934  Ir\ene Joliot-Curie and Fr\'ed\'eric Joliot-Curie bombard aluminum atoms with alpha particles to create artificially radioactive
phosphorus-30
1934  Leo Szilard realizes that nuclear chain reactions may be possible
1934  Enrico Fermi formulates his theory of beta decay
1934  Lev Landau tells Edward Teller that nonlinear molecules may have vibrational modes which remove the degeneracy of an orbitally
degenerate state
1934  Enrico Fermi suggests bombarding uranium atoms with neutrons to make a 93 proton element
1934  Pavel \v Cerenkov reports that light is emitted by relativistic particles traveling in a nonscintillating liquid
1935  Hideki Yukawa presents a theory of strong interactions and predicts mesons
1935  Albert Einstein, Boris Podolsky, and Nathan Rosen put forth the EPR paradox
1935  Niels Bohr presents his analysis of the EPR paradox
1936  Eugene Wigner develops the theory of neutron absorption by atomic nuclei
1936  Hans Jahn and Edward Teller present their systematic study of the symmetry types for which the Jahn-Teller effect is expected
1937  H. Hellmann finds the Hellmann-Feynman theorem
1937  Seth Neddermeyer, 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 Strassman bombard uranium salts with thermal neutrons and discover barium among the reaction products
1939  Lise Meitner and Otto Frisch determine that nuclear fission is taking place in the Hahn-Strassman experiments
1942  Enrico Fermi makes the first controlled nuclear chain reaction
1942  Ernst St\"uckelberg introduces the propagator to positron theory and interprets positrons as negative energy electrons moving
backwards through spacetime
1943  Sin-Itiro Tomonaga publishes his paper on the basic physical principles of quantum electrodynamics
1947  Willis Lamb and Robert Retheford measure the Lamb-Retheford shift
1947  Cecil Powell, C.M.G. Lattes, and G.P.S. Occhialini discover the pi-meson by studying cosmic ray tracks
1947  Richard Feynman presents his propagator approach to quantum electrodynamics
1948  Hendrik Casimir predicts a rudimentary attractive Casimir force on a parallel plate capacitor
1951  Martin Deutsch discovers positronium
1953  R. Wilson observes Delbr\"uck scattering of 1.33 MeV gamma-rays by the electric fields of lead nuclei
1954  Chen Yang and Robert Mills investigate a theory of hadronic isospin by demanding local gauge invariance under isotopic spin space
rotations---first non-Abelian gauge theory
1955  Owen Chamberlain, Emilio Segr\e, Clyde Wiegand, and Thomas Ypsilantis discover the antiproton
1956  Frederick Reines and Clyde Cowan detect antineutrinos
1956  Chen Yang and Tsung Lee propose parity violation by the weak force
1956  Chien Shiung Wu discovers parity violation by the weak force in decaying cobalt
1957  Gerhart L\"uders proves the CPT theorem
1957  Richard Feynman, Murray Gell-Mann, Robert Marshak, and Ennackel Sudarshan propose a V-A Lagrangian for weak interactions
1958  Marcus Sparnaay experimentally confirms the Casimir effect
1959  Yakir Aharonov and David Bohm predict the Aharonov-Bohm effect
1960  R.G. Chambers experimentally confirms the Aharonov-Bohm effect
1961  Murray Gell-Mann and Yuval Ne'eman discover the Eightfold Way patterns---SU(3) group
1961  Jeffery Goldstone considers the breaking of global phase symmetry
1962  Leon Lederman shows that the electron neutrino is distinct from the muon neutrino
1963  Murray Gell-Mann and George Zweig propose the quark/aces model
1964  Peter Higgs considers the breaking of local phase symmetry
1964  J.S. 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 leptons
1969  J.C. Clauser, M. Horne, A. Shimony, and R. 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  S. Freedman and J.C. Clauser perform the first polarization correlation test of Bell's inequality
1973  David Politzer proposes the asymptotic freedom of quarks
1974  Burton Richter and Samuel Ting discover the {\sevenit J}/$\psi$ meson implying the existence of the charm quark
1975  Martin Perl discovers the tauon
1977  S.W. Herb finds the upsilon resonance implying the existence of the beauty quark
1982  A. 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$^\pm$ and Z$^0$ intermediate vector bosons
1989  The Z$^0$ intermediate vector boson resonance width indicates three quark-lepton generations

Particle Physics Technology

1896  Charles Wilson discovers that energetic particles produce droplet tracks in supersaturated gases
1908  Hans Geiger and Ernest Rutherford invent the Geiger counter
1911  Charles Wilson finishes a sophisticated cloud chamber
1934  Ernest Lawrence and Stan Livingston invent the cyclotron
1945  Edwin McMillan devises a synchrotron
1952  Donald Glaser develops the bubble chamber
1968  Georges Charpak and Roger Bouclier build the first multiwire proportional mode particle detection chamber

Gravitational Physics and Relativity

1640  Ismael Bullialdus suggests an inverse-square gravitational force law
1665  Isaac Newton deduces the inverse-square gravitational force law from the falling'' of the Moon
1684  Isaac Newton proves that planets moving under an inverse-square force law will obey Kepler's laws
1686  Isaac Newton uses a fixed length pendulum with weights of varying composition to test the weak equivalence principle to 1 part in 1000
1798  Henry Cavendish measures the gravitational constant
1845  Urbain Leverrier observes a 35'' per century excess precession of Mercury's orbit
1876  William Clifford suggests that the motion of matter may be due to changes in the geometry of space
1882  Simon Newcomb observes a 43'' per century excess precession of Mercury's orbit
1887  Albert Michelson and Edward Morley do not detect the ether drift
1889  Roland von E\"otv\"os uses a torsion fiber balance to test the weak equivalence principle to 1 part in one billion
1893  Ernst Mach states Mach's principle---first constructive attack on the idea of Newtonian absolute space
1905  Albert Einstein completes his theory of special relativity and states the law of mass-energy conservation
1907  Albert Einstein introduces the principle of equivalence of gravitation and inertia and uses it to predict the gravitational redshift
1915  Albert Einstein completes his theory of general relativity
1916  Albert Einstein shows that the field equations of general relativity admit wavelike solutions
1918  J. Lense and Hans Thirring find the gravitomagnetic precession of gyroscopes in the equations of general relativity
1919  Arthur Eddington leads a solar eclipse expedition which claims to detect gravitational deflection of light by the Sun
1921  T. Kaluza demonstrates that a five-dimensional version of Einstein's equations unifies gravitation and electromagnetism
1937  Fritz Zwicky states that galaxies could act as gravitational lenses
1937  Albert Einstein, Leopold Infeld, and Banesh Hoffman show that the geodesic equations of general relativity can be deduced from
its field equations
1957  John Wheeler discusses the breakdown of classical general relativity near singularities and the need for quantum gravity
1960  Robert Pound and Glen Rebka test the gravitational redshift predicted by the equivalence principle to approximately 1\%
1962  Robert Dicke, Peter Roll, and R. Krotkov use a torsion fiber balance to test the weak equivalence principle to 2 parts in 100 billion
1964  Irwin Shapiro predicts a gravitational time delay of radiation travel as a test of general relativity
1965  Joseph Weber puts the first Weber bar gravitational wave detector into operation
1968  Irwin Shapiro presents the first detection of the Shapiro delay
1968  Kenneth Nordtvedt studies a possible violation of the weak equivalence principle for self-gravitating bodies and proposes a new test
of the weak equivalence principle based on observing the relative motion of the Earth and Moon in the Sun's gravitational field
1976  Robert Vessot and Martin Levine use a hydrogen maser clock on a Scout D rocket to test the gravitational redshift predicted by
the equivalence principle to approximately 0.007\%
1979  Dennis Walsh, Robert Carswell, and Ray Weymann discover the gravitationally lensed quasar Q0957+561
1982  Joseph Taylor and Joel Weisberg show that the rate of energy loss from the binary pulsar PSR1913+16 agrees with that predicted by
the general relativistic quadrupole formula to within 5\%

Black Hole Physics

1784  John Michell discusses classical bodies which have escape velocities greater than the speed of light
1795  Pierre Laplace discusses classical bodies which have escape velocities greater than the speed of light
1916  Karl Schwarzschild solves the Einstein vacuum field equations for uncharged spherically symmetric systems
1918  H. Reissner and G. Nordstr\o m solve the Einstein-Maxwell field equations for charged spherically symmetric systems
1923  George Birkhoff proves that the Schwarzschild spacetime geometry is the unique spherically symmetric solution of the Einstein
vacuum field equations
1939  Robert Oppenheimer and Hartland Snyder calculate the collapse of a pressure-free homogeneous fluid sphere and find that it cuts
itself off from communication with the rest of the universe
1963  Roy Kerr solves the Einstein vacuum field equations for uncharged rotating systems
1964  Roger Penrose proves that an imploding star will necessarily produce a singularity once it has formed an event horizon
1965  Ezra Newman, E. Couch, K. Chinnapared, A. Exton, A. Prakash, and Robert Torrence solve the Einstein-Maxwell field equations for
charged rotating systems
1968  Brandon Carter uses Hamilton-Jacobi theory to derive first-order equations of motion for a charged particle moving in the external
fields of a Kerr-Newman black hole
1969  Roger Penrose discusses the Penrose process for the extraction of the spin energy from a Kerr black hole
1969  Roger Penrose proposes the cosmic censorship hypothesis
1971  Identification of Cygnus X-1/HDE 226868 as a binary black hole candidate system
1972  Stephen Hawking proves that the area of a classical black hole's event horizon cannot decrease
1972  James Bardeen, Brandon Carter, and Stephen Hawking propose four laws of black hole mechanics in analogy with the
laws of thermodynamics
1972  Jacob Bekenstein suggests that black holes have an entropy proportional to their surface area due to information loss effects
1974  Stephen Hawking applies quantum field theory to black hole spacetimes and shows that black holes will radiate particles with
a blackbody spectrum which can cause black hole evaporation
1989  Identification of GS2023+338/V404 Cygni as a binary black hole candidate system

Cosmology

1576  Thomas Digges modifies the Copernican system by removing its outer edge and replacing the edge with a star filled unbounded space
1610  Johannes Kepler uses the dark night sky to argue for a finite universe
1720  Edmund Halley puts forth an early form of Olbers' paradox
1744  Jean-Phillipe de Cheseaux puts forth an early form of Olbers' paradox
1826  Heinrich Olbers puts forth Olbers' paradox
1917  Willem de Sitter derives an isotropic static cosmology with a cosmological constant as well as an empty expanding cosmology with a
cosmological constant
1922  Vesto Slipher summarizes his findings on the spiral nebulae's systematic redshifts
1922  Alexander Friedmann finds a solution to the Einstein field equations which suggests a general expansion of space
1927  Georges-Henri Lema\^\i tre discusses the creation event of an expanding universe governed by the Einstein field equations
1928  Harold Robertson briefly mentions that Vesto Slipher's redshift measurements combined with brightness measurements of the same
galaxies indicate a redshift-distance relation
1929  Edwin Hubble demonstrates the linear redshift-distance relation and thus shows the expansion of the universe
1933  Edward Milne names and formalizes the cosmological principle
1934  Georges-Henri Lema\^\i tre interprets the cosmological constant as due to a vacuum'' energy with an unusual perfect fluid equation of state
1938  Paul Dirac presents a cosmological theory where the gravitational constant decreases slowly so that the age of the universe divided by the
atomic light-crossing time always equals the ratio of the electric force to the gravitational force between a proton and electron
1948  Ralph Alpher, Hans Bethe, and George Gamow examine element synthesis in a rapidly expanding and cooling universe and suggest that
the elements were produced by rapid neutron capture
1948  Hermann Bondi, Thomas Gold, and Fred Hoyle propose steady state cosmologies based on the perfect cosmological principle
1951  William McCrea shows that the steady state C-field can be accommodated within general relativity by interpreting it as a
contribution to the energy-momentum tensor with an unusual equation of state
1961  Robert Dicke argues that carbon-based life can only arise when the Dirac large numbers hypothesis is true because this is when burning
stars exist---first use of the weak anthropic principle
1963  Fred Hoyle and Jayant Narlikar show that the steady state theory can explain the isotropy of the universe because deviations from
isotropy and homogeneity exponentially decay in time
1964  Fred Hoyle and Roger Tayler point out that the primordial helium abundance depends on the number of neutrinos
1965  Martin Rees and Dennis Sciama analyze quasar source count data and discover that the quasar density increases with redshift
1965  Edward Harrison resolves Olbers' paradox by noting the finite lifetime of stars
1966  Stephen Hawking and George Ellis show that any plausible general relativistic cosmology is singular
1966  Jim Peebles shows that the hot Big Bang predicts the correct helium abundance
1967  Andrey Sakharov presents the requirements for a baryon-antibaryon asymmetry in the universe
1967  John Bahcall, Wal Sargent, and Maarten Schmidt measure the fine-structure splitting of spectral lines in 3C191 and thereby show that
the fine-structure constant does not vary significantly with time
1968  Brandon Carter speculates that perhaps the fundamental constants of nature must lie within a restricted range to allow the emergence
of life---first use of the strong anthropic principle
1969  Charles Misner formally presents the Big Bang horizon problem
1969  Robert Dicke formally presents the Big Bang flatness problem
1973  Edward Tryon proposes that the universe may be a large scale quantum mechanical vacuum fluctuation where positive mass-energy
is balanced by negative gravitational potential energy
1974  Robert Wagoner, William Fowler, and Fred Hoyle show that the hot Big Bang predicts the correct deuterium and lithium abundances
1976  A.I. Shlyakhter uses samarium ratios from the prehistoric natural fission reactor in Gabon to show that some laws of physics have
remained unchanged for over two billion years
1977  Gary Steigman, David Schramm, and James Gunn examine the relation between the primordial helium abundance and number of neutrinos
and claim that at most five lepton families can exist
1980  Alan Guth proposes the inflationary Big Bang universe as a possible solution to the horizon and flatness problems

Cosmic Microwave Background Astronomy

1934  Richard Tolman shows that blackbody radiation in an expanding universe cools but remains thermal
1941  Andrew McKellar uses the excitation of CN doublet lines to measure that the effective temperature of space'' is about 2.3 K
1948  George Gamow, Ralph Alpher, and Robert Herman predict that a Big Bang universe will have a blackbody cosmic microwave
background with temperature about 5 K
1955  Tigran Shmaonov finds excess microwave emission with a temperature of roughly 3 K
1964  A.G. Doroshkevich and Igor Novikov write an unnoticed paper suggesting microwave searches for the blackbody radiation predicted
by Gamow, Alpher, and Herman
1965  Arno Penzias, Robert Wilson, Bernie Burke, Robert Dicke, and James Peebles discover the cosmic microwave background radiation
1966  Rainer Sachs and Arthur Wolfe theoretically predict microwave background fluctuation amplitudes created by gravitational
potential variations between observers and the last scattering surface
1968  Martin Rees and Dennis Sciama theoretically predict microwave background fluctuation amplitudes created by photons traversing
time-dependent potential wells
1969  R.A. Sunyaev and Yakov Zel'dovich study the inverse Compton scattering of microwave background photons by hot electrons
1990  The COBE satellite shows that the microwave background has a nearly perfect blackbody spectrum and thereby strongly constrains
the density of the intergalactic medium
1992  The COBE satellite discovers anisotropy in the cosmic microwave background

Other Background Radiation Fields

1912  Victor Hess discovers that the ionization of air increases with altitude indicating the existence of cosmic radiation
1956  Herbert Friedman detects evidence for extrasolar X-rays
1962  Riccardo Giacconi, Herbert Gursky, F. Paolini, and Bruno Rossi formally discover the X-ray background

Galaxies, Clusters of Galaxies, and Large Scale Structure

1521  Ferdinand Magellan observes the Magellanic Clouds during his circumnavigating expedition
1750  Thomas Wright discusses galaxies and the shape of the Milky Way
1845  Lord Rosse discovers a nebula with a distinct spiral shape
1918  Harlow Shapley demonstrates that globular clusters surround our galaxy like a halo and are not centered on the Earth
1920  Harlow Shapely and Heber Curtis debate whether or not the spiral nebulae lie within the Milky Way
1923  Edwin Hubble resolves the Shapely-Curtis debate by finding Cepheids in Andromeda
1932  Karl Jansky discovers radio noise from the center of the Milky Way
1933  Fritz Zwicky applies the virial theorem to the Coma cluster and obtains evidence for unseen mass
1936  Edwin Hubble introduces the spiral, barred spiral, elliptical, and irregular galaxy classifications
1939  Grote Reber discovers the radio source Cygnus A
1943  Carl Seyfert identifies six spiral galaxies with unusually broad emission lines
1949  J.G. Bolton, G.J. Stanley, and O.B. Slee identify NGC 4486 (M87) and NGC 5128 as extragalactic radio sources
1953  G\'erard de Vaucouleurs discovers that the galaxies within approximately 200 million light years of the Virgo cluster are
confined to a giant supercluster disk
1954  Walter Baade and Rudolph Minkowski identify the extragalactic optical counterpart of the radio source Cygnus A
1960  Thomas Matthews determines the radio position of 3C48 to within 5''
1960  Allan Sandage optically studies 3C48 and observes an unusual blue quasi stellar object
1962  Cyril Hazard, M.B. Mackey, and A.J. Shimmins use lunar occultations to determine a precise position for 3C273 and deduce that
it is a double source
1963  Maarten Schmidt identifies the redshifted Balmer lines from the quasar 3C273
1973  Jeremiah Ostriker and James Peebles discover that the amount of visible matter in the disks of typical spiral galaxies is not
enough for Newtonian gravitation to keep the disks from flying apart or drastically changing shape
1974  B.L. Fanaroff and J.M. Riley distinguish between edge-darkened (FR I) and edge-brightened (FR II) radio sources
1976  Sandra Faber and Robert Jackson discover the Faber-Jackson relation between the luminosity of an elliptical galaxy and the
velocity dispersion in its center
1977  Brent Tully and Richard Fisher discover the Tully-Fisher relation between the luminosity of an isolated spiral galaxy and the
velocity of the flat part of its rotation curve
1978  Steve Gregory and Laird Thompson describe the Coma supercluster
1978  Vera Rubin, Kent Ford, N. Thonnard, and Albert Bosma measure the rotation curves of several spiral galaxies and find significant
deviations from what is predicted by the Newtonian gravitation of visible stars
1981  Robert Kirshner, August Oemler, Paul Schechter, and Stephen Shectman find evidence for a giant void in Bo\"otes with a diameter
of approximately 100 million light years
1985  Robert Antonucci and J. Miller discover that the Seyfert II galaxy NGC 1068 has broad lines which can only be seen in polarized
reflected light
1986  Amos Yahil, David Walker, and Michael Rowan-Robinson find that the direction of the IRAS galaxy density dipole agrees with the
direction of the cosmic microwave background temperature dipole
1987  David Burstein, Roger Davies, Alan Dressler, Sandra Faber, Donald Lynden-Bell, R.J. Terlevich, and Gary Wegner claim that a
large group of galaxies within about 200 million light years of the Milky Way are moving together towards The Great Attractor''
1990  Michael Rowan-Robinson and Tom Broadhurst discover that the IRAS galaxy F10214+4724 is the brightest known object in the universe

The Interstellar Medium and Intergalactic Medium

1848  Lord Rosse studies M1 and names it the Crab Nebula
1864  William Huggins studies the spectrum of the Orion Nebula and shows that it is a cloud of gas
1927  Ira Bowen explains unidentified spectral lines from space as forbidden transition lines
1930  Robert Trumpler discovers absorption by interstellar dust by comparing the angular sizes and brightnesses of globular clusters
1944  Hendrik van de Hulst predicts the 21 cm hyperfine line of neutral interstellar hydrogen
1951  H.I. Ewen and Edward Purcell observe the 21 cm hyperfine line of neutral interstellar hydrogen
1956  Lyman Spitzer predicts coronal gas around the Milky Way
1965  James Gunn and Bruce Peterson use observations of the relatively low absorption of the blue component of the Lyman-alpha line
from 3C9 to strongly constrain the density and ionization state of the intergalactic medium
1969  Lewis Snyder, David Buhl, Ben Zuckerman, and Patrick Palmer find interstellar formaldehyde
1970  Arno Penzias and Robert Wilson find interstellar carbon monoxide
1970  George Carruthers observes molecular hydrogen in space
1977  Christopher McKee and Jeremiah Ostriker propose a three component theory of the interstellar medium

White Dwarfs, Neutron Stars, and Supernovae

1054  Chinese and American Indian astronomers observe the Crab supernova explosion
1572  Tycho Brahe discovers his supernova in Cassiopeia
1604  Johannes Kepler's supernova in Serpens is observed
1862  Alvan Clark observes Sirius B
1866  William Huggins studies the spectrum of a nova and discovers that it is surrounded by a cloud of hydrogen
1914  Walter Adams determines an incredibly high density for Sirius B
1926  Ralph Fowler uses Fermi-Dirac statistics to explain white dwarf stars
1930  Subrahmanyan Chandrasekhar discovers the white dwarf maximum mass limit
1933  Fritz Zwicky and Walter Baade propose the neutron star idea and suggest that supernovae might be created by the collapse of
normal stars to neutron stars---they also point out that such events can explain the cosmic ray background
1939  Robert Oppenheimer and George Volkoff calculate the first neutron star models
1942  J.J.L. Duyvendak, Nicholas Mayall, and Jan Oort deduce that the Crab Nebula is a remnant of the 1054 supernova
observed by Chinese astronomers
1958  Evry Schatzman, Kent Harrison, Masami Wakano, and John Wheeler show that white dwarfs are unstable to inverse beta decay
1962  Riccardo Giacconi, Herbert Gursky, Frank Paolini, and Bruno Rossi discover Sco X-1
1967  Jocelyn Bell and Anthony Hewish discover radio pulses from a pulsar
1967  J.R. Harries, Ken McCracken, R.J. Francey, and A.G. Fenton discover the first X-ray transient (Cen X-2)
1968  Thomas Gold proposes that pulsars are rotating neutron stars
1969  David Staelin, E.C. Reifenstein, William Cocke, Mike Disney, and Donald Taylor discover the Crab Nebula pulsar thus connecting
supernovae, neutron stars, and pulsars
1971  Riccardo Giacconi, Herbert Gursky, Ed Kellogg, R. Levinson, E. Schreier, and H. Tananbaum discover 4.8 second X-ray pulsations
from Cen X-3
1974  Russell Hulse and Joseph Taylor discover the binary pulsar PSR1913+16
1977  Kip Thorne and Anna \.Zytkow present a detailed analysis of Thorne-\.Zytkow objects
1982  D.C. Backer, Shrinivas Kulkarni, Carl Heiles, M.M. Davis, and Miller Goss discover the millisecond pulsar PSR1937+214
1985  Michiel van der Klis discovers 30 Hz quasi-periodic oscillations in GX 5-1
1987  Ian Shelton discovers supernova 1987A in the Large Magellanic Cloud

Stellar Astronomy

-134  Hipparchus creates the magnitude scale of stellar apparent luminosities
1596  David Fabricus notices that Mira's brightness varies
1672  Geminiano Montanari notices that Algol's brightness varies
1686  Gottfried Kirch notices that Chi Cygni's brightness varies
1718  Edmund Halley discovers stellar proper motions by comparing his astrometric measurements with those of the Greeks
1782  John Goodricke notices that the brightness variations of Algol are periodic and proposes that it is partially eclipsed by a body
moving around it
1784  Edward Piggot discovers the first Cepheid variable star
1838  Thomas Henderson, Friedrich Struve, and Friedrich Bessel measure stellar parallaxes
1844  Friedrich Bessel explains the wobbling motions of Sirius and Procyon by suggesting that these stars have dark companions
1906  Arthur Eddington begins his statistical study of stellar motions
1908  Henrietta Leavitt discovers the Cepheid period-luminosity relation
1910  Ejnar Hertzsprung and Henry Russell study the relation between magnitudes and spectral types of stars
1924  Arthur Eddington develops the main-sequence mass-luminosity relationship
1929  George Gamow proposes hydrogen fusion as the energy source for stars
1938  Hans Bethe and Carl von Weizs\"acker detail the proton-proton chain and CNO cycle in stars
1939  Rupert Wildt realizes the importance of the negative hydrogen ion for stellar opacity
1952  Walter Baade distinguishes between Cepheid I and Cepheid II variable stars
1953  Fred Hoyle predicts a carbon-12 resonance to allow stellar triple alpha reactions at reasonable stellar interior temperatures
1961  Chushiro Hayashi publishes his work on the Hayashi track of fully convective stars
1963  Fred Hoyle and William Fowler conceive the idea of supermassive stars
1964  Subrahmanyan Chandrasekhar and Richard Feynman develop a general relativistic theory of stellar pulsations and show that
supermassive stars are subject to a general relativistic instability
1967  Gerry Neugebauer and Eric Becklin discover the Becklin-Neugebauer object at 10 microns

Solar Astronomy

1613  Galileo Galilei uses sunspot observations to demonstrate the rotation of the Sun
1619  Johannes Kepler postulates a solar wind to explain the direction of comet tails
1802  William Wollaston observes dark lines in the solar spectrum
1814  Joseph Fraunhofer systematically studies the dark lines in the solar spectrum
1834  Hermann Helmholtz proposes gravitational contraction as the energy source for the Sun
1843  Heinrich Schwabe announces his discovery of the sunspot cycle and estimates its period to be about ten years
1852  Edward Sabine shows that sunspot number is correlated with geomagnetic field variations
1859  Richard Carrington discovers solar flares
1860  Gustav Kirchoff and Robert Bunsen discover that each element has its own distinct set of spectral lines and use this fact to explain
the solar dark lines
1861  F.G.W. Sp\"orer discovers the variation of sunspot latitudes during a solar cycle
1863  Richard Carrington discovers the differential nature of solar rotation
1868  Pierre-Jules-C\'esar Janssen and Norman Lockyer discover an unidentified yellow line in solar prominence spectra and suggest it
comes from a new element which they name helium''
1893  Edward Maunder discovers the 1645--1715 Maunder sunspot minimum
1904  Edward Maunder plots the first sunspot butterfly diagram''
1906  Karl Schwarzschild explains solar limb darkening
1908  George Hale discovers the Zeeman splitting of spectral lines from sunspots
1942  J.S. Hey detects solar radio waves
1949  Herbert Friedman detects solar X-rays
1960  Robert Leighton, Robert Noyes, and George Simon discover solar five-minute oscillations by observing the Doppler shifts of solar
dark lines
1961  H. Babcock proposes the magnetic coiling sunspot theory
1970  Roger Ulrich, John Leibacher, and Robert Stein deduce from theoretical solar models that the interior of the Sun could act as a
resonant acoustic cavity
1975  Franz-Ludwig Deubner makes the first accurate measurements of the period and horizontal wavelength of the five-minute solar oscillations

Solar System Astronomy

-2136 Chinese astronomers record a solar eclipse
-586  Thales of Miletus predicts a solar eclipse
-350  Aristotle argues for a spherical Earth using lunar eclipses and other observations
-280  Aristarchus uses the size of the Earth's shadow on the Moon to estimate that the Moon's radius is one-third that of the Earth
-200  Eratosthenes uses shadows to determine that the radius of the Earth is roughly 6,400 km
-150  Hipparchus uses parallax to determine that the distance to the Moon is roughly 380,000 km
-134  Hipparchus discovers the precession of the equinoxes
1512  Nicholas Copernicus first states his heliocentric theory in {\sevenit Commentariolus}
1543  Nicholas Copernicus shows that his heliocentric theory simplifies planetary motion tables in {\sevenit De Revolutionibus de Orbium Coelestium}
1577  Tycho Brahe uses parallax to prove that comets are distant entities and not atmospheric phenomena
1609  Johannes Kepler states his first two empirical laws of planetary motion
1610  Galileo Galilei discovers Callisto, Europa, Ganymede, and Io
1610  Galileo Galilei sees Saturn's rings but does not recognize that they are rings
1619  Johannes Kepler states his third empirical law of planetary motion
1655  Giovanni Cassini discovers Jupiter's great red spot
1656  Christian Huygens identifies Saturn's rings as rings and discovers Titan and the Orion Nebula
1665  Giovanni Cassini determines the rotational speeds of Jupiter, Mars, and Venus
1672  Giovanni Cassini discovers Rhea
1672  Jean Richer and Giovanni Cassini measure the astronomical unit to be about 138,370,000 km
1675  Ole R\"omer uses the orbital mechanics of Jupiter's moons to estimate that the speed of light is about 227,000 km/s
1705  Edmund Halley publicly predicts the periodicity of Halley's comet and computes its expected path of return in 1758
1715  Edmund Halley calculates the shadow path of a solar eclipse
1716  Edmund Halley suggests a high-precision measurement of the Sun-Earth distance by timing the transit of Venus
1758  Johann Palitzsch observes the return of Halley's comet
1766  Johann Titius finds the Titius-Bode rule for planetary distances
1772  Johann Bode publicizes the Titius-Bode rule for planetary distances
1781  William Herschel discovers Uranus during a telescopic survey of the northern sky
1796  Pierre Laplace states his nebular hypothesis for the formation of the solar system from a spinning nebula of gas and dust
1801  Giuseppe Piazzi discovers the asteroid Ceres
1802  Heinrich Olbers discovers the asteroid Pallas
1821  Alexis Bouvard detects irregularities in the orbit of Uranus
1825  Pierre Laplace completes his study of gravitation, the stability of the solar system, tides, the precession of the equinoxes, the
libration of the Moon, and Saturn's rings in {\sevenit M\'ecanique C\'eleste}
1843  John Adams predicts the existence and location of Neptune from irregularities in the orbit of Uranus
1846  Urbain Leverrier predicts the existence and location of Neptune from irregularities in the orbit of Uranus
1846  Johann Galle discovers Neptune
1846  William Lassell discovers Triton
1849  Edouard Roche finds the limiting radius of tidal destruction and tidal creation for a body held together only by its self gravity
and uses it to explain why Saturn's rings do not condense into a satellite
1856  James Clerk Maxwell demonstrates that a solid ring around Saturn would be torn apart by gravitational forces and argues that
Saturn's rings consist of a multitude of tiny satellites
1866  Giovanni Schiaparelli realizes that meteor streams occur when the Earth passes through the orbit of a comet that has left debris
along its path
1906  Max Wolf discovers the Trojan asteroid Achilles
1930  Clyde Tombaugh discovers Pluto
1930  Seth Nicholson measures the surface temperature of the Moon
1950  Jan Oort suggests the presence of a cometary Oort cloud
1951  Gerard Kuiper argues for an annular reservoir of comets between 40--100 astronomical units from the Sun
1977  James Elliot discovers the rings of Uranus during a stellar occultation experiment on the Kuiper Airborne Observatory
1978  James Christy discovers Charon
1978  Peter Goldreich and Scott Tremaine present a Boltzmann equation model of planetary-ring dynamics for indestructible spherical ring
particles that do not self-gravitate and find a stability requirement relation between ring optical depth and particle normal
restitution coefficient
1988  Martin Duncan, Thomas Quinn, and Scott Tremaine demonstrate that short-period comets come primarily from the Kuiper Belt and not
the Oort cloud

Astronomical Maps, Catalogs, and Surveys

-134  Hipparchus makes a detailed star map
1678  Edmund Halley publishes a catalog of 341 southern stars---first systematic southern sky survey
1771  Charles Messier publishes his first list of nebulae
1864  John Herschel publishes the {\sevenit General Catalog} of nebulae and star clusters
1890  John Dreyer publishes the {\sevenit New General Catalog} of nebulae and star clusters
1956  Completion of the Palomar sky survey with the Palomar 48-inch Schmidt optical reflecting telescope
1962  A.S. Bennett publishes the {\sevenit Revised 3C Catalog} of 328 radio sources
1965  Gerry Neugebauer and Robert Leighton begin a 2.2 micron sky survey with a 1.6-meter telescope on Mount Wilson
1993  Start of the 20 cm VLA FIRST survey

Telescopes, Observatories, and Observing Technology

1608  Hans Lippershey tries to patent an optical refracting telescope
1609  Galileo Galilei builds his first optical refracting telescope
1641  William Gascoigne invents telescope cross hairs
1661  James Gregory proposes an optical reflecting telescope
1668  Isaac Newton constructs the first optical reflecting telescope
1733  Chester Moor Hall invents the achromatic lens refracting telescope
1758  John Dolland reinvents the achromatic lens
1789  William Herschel finishes a 49-inch optical reflecting telescope---located in Slough, England
1840  J.W. Draper invents astronomical photography and photographs the Moon
1845  Lord Rosse finishes the Birr Castle 72-inch optical reflecting telescope---located in Parsonstown, Ireland
1872  Henry Draper invents astronomical spectral photography and photographs the spectrum of Vega
1890  Albert Michelson proposes the stellar interferometer
1892  George Hale finishes a spectroheliograph---allows the Sun to be photographed in the light of one element only
1897  Alvan Clark finishes the Yerkes 40-inch optical refracting telescope---located in Williams Bay, Wisconsin
1917  Mount Wilson 100-inch optical reflecting telescope begins operation---located in Mount Wilson, California
1930  Bernard-Ferdinand Lyot invents the coronagraph
1930  Karl Jansky builds a 30-meter long rotating aerial radio telescope
1933  Bernard-Ferdinand Lyot invents the Lyot filter
1934  Bernhard Schmidt finishes the first 14-inch Schmidt optical reflecting telescope
1936  Palomar 18-inch Schmidt optical reflecting telescope begins operation---located in Palomar, California
1937  Grote Reber builds a 31-foot radio telescope
1947  Bernard Lovell and his group complete the Jodrell Bank 218-foot non-steerable radio telescope
1949  Palomar 48-inch Schmidt optical reflecting telescope begins operation---located in Palomar, California
1949  Palomar 200-inch optical reflecting telescope begins regular operation---located in Palomar, California
1957  Bernard Lovell and his group complete the Jodrell Bank 250-foot steerable radio telescope
1957  Peter Scheuer publishes his {\sevenit P(D)} method for obtaining source counts of spatially unresolved sources
1960  Martin Ryle tests Earth rotation aperature synthesis
1960  Owens Valley 27-meter radio telescopes begin operation---located in Big Pine, California
1963  Arecibo 300-meter radio telescope begins operation---located in Arecibo, Puerto Rico
1964  Ryle 1-mile radio interferometer begins operation---located in Cambridge, England
1965  Owens Valley 40-meter radio telescope begins operation---located in Big Pine, California
1967  First VLBI images---183 km baseline
1969  Observations start at Big Bear Solar Observatory---located in Big Bear, California
1970  Cerro Tololo 158-inch optical reflecting telescope begins operation---located in Cerro Tololo, Chile
1970  Kitt Peak National Observatory 158-inch optical reflecting telescope begins operation---located near Tucson, Arizona
1974  Anglo-Australian 153-inch optical reflecting telescope begins operation---located in Siding Springs, Australia
1975  Gerald Smith, Frederick Landauer, and James Janesick use a CCD to observe Uranus---first astronomical CCD observation
1978  Multiple Mirror 176-inch equivalent optical/infrared reflecting telescope begins operation---located in Amado, Arizona
1979  UKIRT 150-inch infrared reflecting telescope begins operation---located at Mauna Kea, Hawaii
1979  Canada-France-Hawaii 140-inch optical reflecting telescope begins operation---located at Mauna Kea, Hawaii
1980  Completion of construction of the VLA---located in Socorro, New Mexico
1993  Keck 10-meter optical/infrared reflecting telescope begins operation---located at Mauna Kea, Hawaii

Artificial Satellites and Space Probes

1957  {\sevenit Sputnik I} is launched---first orbiting satellite
1962  {\sevenit Mariner 2} is the first mission to Venus
1965  {\sevenit Mariner 4} sends the first clear pictures of Mars
1966  {\sevenit Luna 10} becomes the first spacecraft to orbit the Moon
1967  {\sevenit Venera 4} sends the first data from below the clouds of Venus
1967  The OSO-3 gamma-ray satellite discovers gamma-ray emission from the plane of the Milky Way
1970  Launch of {\sevenit Uhuru}---first dedicated X-ray satellite
1972  Launch of the {\sevenit Copernicus} ultraviolet satellite
1974  {\sevenit Mariner 10} passes by and photographs Mercury
1974  Launch of the {\sevenit Ariel V} X-ray satellite
1975  {\sevenit Venera 9} returns the first pictures of the surface of Venus
1976  {\sevenit Viking I} and {\sevenit Viking II} land on Mars
1976  The {\sevenit Vela} and ANS X-ray satellites discover X-ray bursts
1976  The OSO-8 X-ray satellite shows that X-ray bursts have blackbody spectra
1977  Launch of the HEAO-1 X-ray satellite
1978  Launch of the {\sevenit International Ultraviolet Explorer} satellite
1978  Launch of the {\sevenit Einstein} X-ray satellite (HEAO-2)---first X-ray photographs of astronomical objects
1979  Launch of the {\sevenit Hakucho} X-ray satellite (ASTRO-A)
1979  Launch of the {\sevenit Ariel VI} cosmic-ray and X-ray satellite
1979  {\sevenit Voyager 1} and {\sevenit Voyager 2} send back images of Jupiter and its system
1980  {\sevenit Voyager 1} sends back images of Saturn and its system
1980  Launch of the {\sevenit Solar Maximum Mission} satellite
1981  {\sevenit Voyager 2} sends back images of Saturn and its system
1983  Launch of the EXOSAT X-ray satellite
1983  Launch of the {\sevenit Tenma} X-ray satellite (ASTRO-B)
1983  Launch of the IRAS satellite
1986  {\sevenit Voyager 2} sends back images of Uranus and its system
1987  Launch of the {\sevenit Ginga} X-ray satellite (ASTRO-C)
1989  {\sevenit Voyager 2} sends back images of Neptune and its system
1989  Launch of the {\sevenit Granat} gamma-ray and X-ray satellite
1989  Launch of the {\sevenit Hipparcos} satellite
1989  Launch of the COBE satellite
1990  Launch of the {\sevenit Hubble Space Telescope}
1990  Launch of the ROSAT X-ray satellite---first imaging X-ray sky survey
1990  First observations made with {\sevenit Astro-1} (BBXRT, HUT, UIT, WUPPE)
1991  Launch of the {\sevenit Compton Gamma-Ray Observatory} satellite
1993  Launch of the {\sevenit Asca} X-ray satellite (ASTRO-D)

Biology and Organic Chemistry

-320  Theophrastus begins the systematic study of botany
1658  Jan Swammerdam observes red blood cells under a microscope
1663  Robert Hooke sees cells in cork using a microscope
1668  Francesco Redi disproves theories of the spontaneous generation of maggots in putrefying matter
1676  Anton van Leeuwenhoek observes protozoa and calls them animalcules''
1677  Anton van Leeuwenhoek observes spermatazoa
1683  Anton van Leeuwenhoek observes bacteria
1765  Lazzaro Spallanzani disproves many theories of the spontaneous generation of cellular life
1771  Joseph Priestly discovers that plants convert carbon dioxide into oxygen
1798  Thomas Malthus discusses human population growth and food production in {\sevenit An Essay on the Principle of Population}
1801  Jean Lamarck begins the detailed study of invertebrate taxonomy
1809  Jean Lamarck proposes an inheritance of acquired characteristics theory of evolution
1817  Pierre-Joseph Pelletier and Joseph-Bienaim\'e Caventou isolate chlorophyll
1828  Karl von Baer discovers the eggs of mammals
1828  Friedrich W\"ohler synthesizes urea---first synthesis of an organic compound
1836  Theodor Schwann discovers pepsin in extracts from the stomach lining---first isolation of an animal enzyme
1837  Theodor Schwann shows that heating air will prevent it from causing putrefaction
1838  Matthias Schleiden discovers that all living plant tissue is composed of cells
1839  Theodor Schwann discovers that all living animal tissue is composed of cells
1856  Louis Pasteur states that microorganisms produce fermentation
1858  Charles R. Darwin and Alfred Wallace independently propose natural selection theories of evolution
1858  Rudolf Virchow proposes that cells can only arise from pre-existing cells
1862  Louis Pasteur convincingly disproves the spontaneous generation of cellular life
1865  Gregor Mendel presents his experiments on the crossbreeding of pea plants and postulates dominant and recessive factors
1865  August Kekul\'e realizes that benzene is composed of carbon and hydrogen atoms in a hexagonal ring
1869  Friedrich Miescher discovers nucleic acids in the nuclei of cells
1874  Jacobus van't Hoff and Joseph-Achille Le Bel advance a three-dimensional stereochemical representation of organic molecules and
propose a tetrahedral carbon atom
1876  Oskar Hertwig and Hermann Fol show that fertilized eggs possess both male and female nuclei
1884  Emil Fischer begins his detailed analysis of the compositions and structures of sugars
1898  Martinus Beijerinck uses filtering experiments to show that tobacco mosaic disease is caused by something smaller than a bacteria
which he names a virus
1906  Mikhail Tsvett discovers the chromatography technique for organic compound separation
1907  Ivan Pavlov demonstrates conditioned responses with salivating dogs
1907  Emil Fischer artificially synthesizes peptide amino acid chains and thereby shows that amino acids in proteins are connected by
amino group-acid group bonds
1911  Thomas Morgan proposes that Mendelian factors are arranged in a line on chromosomes
1926  James Sumner shows that the urease enzyme is a protein
1928  Otto Diels and Kurt Alder discover the Diels-Alder cycloaddition reaction for forming ring molecules
1929  Phoebus Levene discovers the sugar deoxyribose in nucleic acids
1929  Edward Doisy and Adolf Butenandt independently discover estrone
1930  John Northrop shows that the pepsin enzyme is a protein
1931  Adolf Butenandt discovers androsterone
1932  Hans Krebs discovers the urea cycle
1933  Tadeus Reichstein artificially synthesizes vitamin C---first vitamin synthesis
1935  Rudolf Schoenheimer uses hydrogen-2 as a tracer to examine the fat storage system of rats
1935  Wendell Stanley crystallizes the tobacco mosaic virus
1935  Konrad Lorenz describes the imprinting behavior of young birds
1937  Theodosius Dobzhansky links evolution and genetic mutation in {\sevenit Genetics and the Origin of Species}
1938  A living coelacanth is found off the coast of southern Africa
1940  Donald Griffin and Robert Galambos announce their discovery of sonar echolocation by bats
1942  Max Delbr\"uck and Salvador Luria demonstrate that bacterial resistance to virus infection is caused by random mutation and not
adaptive change
1944  Oswald Avery shows that DNA carries the genetic code in pneumococci bacteria
1944  Robert Woodward and William von Eggers Doering synthesize quinine
1948  Erwin Chargaff shows that in DNA the number of guanine units equals the number of cytosine units and the number of adenine units
equals the number of thymine units
1951  Robert Woodward synthesizes cholesterol and cortisone
1952  Alfred Hershey and Martha Chase use radioactive tracers to show that DNA is the genetic material in bacteriophage viruses
1952  Fred Sanger, Hans Tuppy, and Ted Thompson complete their chromatographic analysis of the insulin amino acid sequence
1952  Rosalind Franklin uses X-ray diffraction to study the structure of DNA and suggests that its sugar-phosphate backbone is on
its outside
1953  James Watson and Francis Crick propose a double helix structure for DNA
1953  Max Perutz and John Kendrew determine the structure of hemoglobin using X-ray diffraction studies
1953  Stanley Miller shows that amino acids can be formed when simulated lightning is passed through vessels containing water, methane,
ammonia, and hydrogen
1955  Severo Ochoa discovers RNA polymerase enzymes
1955  Arthur Kornberg discovers DNA polymerase enzymes
1960  Juan Or\'o finds that concentrated solutions of ammonium cyanide in water can produce the nucleotide organic base adenine
1960  Robert Woodward synthesizes chlorophyll
1967  John Gurden uses nuclear transplantation to clone a clawed frog---first cloning of a vertebrate
1968  Fred Sanger uses radioactive phosphorous as a tracer to chromatographically decipher a 120 base long RNA sequence
1970  Hamilton Smith and Daniel Nathans discover DNA restriction enzymes
1970  Howard Temin and David Baltimore independently discover reverse transcriptase enzymes
1972  Robert Woodward synthesizes vitamin B-12
1972  Stephen Jay Gould and Niles Eldredge propose punctuated equilibrium effects in evolution
1974  Manfred Eigen and Manfred Sumper show that mixtures of nucleotide monomers and RNA-replicase will give rise to RNA molecules which
replicate, mutate, and evolve
1974  Leslie Orgel shows that RNA can replicate without RNA-replicase and that zinc aids this replication
1977  John Corliss, Jack Dymond, Louis Gordon, John Edmond, Richard von Herzen, Robert Ballard, Kenneth Green, David Williams, Arnold
Bainbridge, Kathy Crane, and Tjeerd van Andel discover chemosynthetically based animal communities located around submarine
thermal springs on the Gal\'apagos Rift
1977  Walter Gilbert and Allan Maxam present a rapid gene sequencing technique which uses cloning, base destroying chemicals, and
gel electrophoresis
1977  Fred Sanger and Alan Coulson present a rapid gene sequencing technique which uses dideoxynucleotides and gel electrophoresis
1978  Fred Sanger presents the 5,386 base sequence for the virus $\phi$X174 --- first sequencing of an entire genome
1983  Kary Mullis invents the polymerase chain reaction
1984  Alec Jeffreys devises a DNA fingerprinting method
1985  Harry Kroto, J.R. Heath, S.C. O'Brien, R.F. Curl, and Richard Smalley discover the unusual stability of the carbon-60
Buckminsterfullerine molecule and deduce its structure
1990  Wolfgang Kr\"atschmer, Lowell Lamb, Konstantinos Fostiropoulos, and Donald Huffman discover that Buckminsterfullerine can be
separated from soot because it is soluble in benzene

Medicine and Medical Technology

-420  Hippocrates begins the scientific study of medicine by maintaining that diseases have natural causes
-280  Herophilus studies the nervous system and distinguishes between sensory nerves and motor nerves
-250  Erasistratus studies the brain and distinguishes between the cerebrum and cerebellum
50    Pedanius Dioscorides describes the medical applications of plants in {\sevenit De Materia Medica}
180   Galen studies the connection between paralysis and severance of the spinal cord
1242  Ibn an-Naf\=\i s suggests that the right and left ventricles of the heart are separate and describes the lesser circulation of blood
1249  Roger Bacon writes about convex lens eyeglasses for treating farsightedness
1403  Venice implements a quarantine against the Black Death
1451  Nicholas of Cusa invents concave lens spectacles to treat nearsightedness
1543  Andreas Vesalius publishes {\sevenit De Fabrica Corporis Humani} which corrects Greek medical errors and revolutionizes medicine
1546  Gerolamo Fracastoro proposes that epidemic diseases are caused by transferable seedlike entities
1553  Miguel Serveto describes the lesser circulation of blood through the lungs
1559  Realdo Colombo describes the lesser circulation of blood through the lungs in detail
1603  Girolamo Fabrici studies leg veins and notices that they have valves which only allow blood to flow toward the heart
1628  William Harvey explains the vein-artery system and structure of the heart in {\sevenit De Motu Cordis et Sanguinis}
1701  Giacomo Pylarini gives the first smallpox inoculations
1747  James Lind discovers that citrus fruits prevent scurvy
1763  Claudius Aymand performs the first successful appendectomy
1796  Edward Jenner develops a smallpox vaccination method
1800  Humphry Davy announces the anaesthetic properties of nitrous oxide
1816  Rene Laennec invents the stethoscope
1842  Crawford Long performs the first surgical operation using anasthesia
1847  Ignaz Semmelweis studies and prevents the transmission of puerperal fever
1870  Louis Pasteur and Robert Koch establish the germ theory of disease
1881  Louis Pasteur develops an anthrax vaccine
1882  Louis Pasteur develops a rabies vaccine
1890  Emil von Behring discovers antitoxins and uses them to develop tetanus and diptheria vaccines
1906  Frederick Hopkins suggests the existence of vitamins and suggests that a lack of vitamins causes scurvy and rickets
1907  Paul Ehrlich develops a chemotheraputic cure for sleeping sickness
1921  Edward Mellanby discovers vitamin D and shows that its absence causes rickets
1928  Alexander Fleming discovers penicillin
1932  Gerhard Domagk develops a chemotheraputic cure for streptococcus
1952  Jonas Salk develops the first polio vaccine

Pure and Applied Mathematics

-1700 Egyptian mathematicians employ primitive fractions
-530  Pythagoras studies propositional geometry and vibrating lyre strings
-370  Eudoxus states the method of exhaustion for area determination
-350  Aristotle discusses logical reasoning in {\sevenit Organon}
-300  Euclid studies geometry as an axiomatic system in {\sevenit Elements} and states the law of reflection in {\sevenit Catoptrics}
-260  Archimedes computes $\pi$ to two decimal places using inscribed and cirumscribed polygons and computes the area under a parabolic segment
-200  Apollonius writes {\sevenit On Conic Sections} and names the ellipse, parabola, and hyperbola
250   Diophantus writes {\sevenit Arithmetica}, the first systematic treatise on algebra
450   Tsu Ch'ung-Chih and Tsu K\^eng-Chih compute $\pi$ to six decimal places
550   Hindu mathematicians give zero a numeral representation in a positional notation system
1202  Leonardo Fibonacci demonstrates the utility of Arabic numerals in his {\sevenit Book of the Abacus}
1424  Ghiy\=ath al-K\=ash\=\i\ computes $\pi$ to sixteen decimal places using inscribed and cirumscribed polygons
1520  Scipione Ferro develops a method for solving cubic equations
1535  Niccol\o Tartaglia develops a method for solving cubic equations
1540  Lodovico Ferrari solves the quartic equation
1596  Ludolf van Ceulen computes $\pi$ to twenty decimal places using inscribed and cirumscribed polygons
1614  John Napier discusses Napierian logarithms in {\sevenit Mirifici Logarithmorum Canonis Descriptio}
1617  Henry Briggs discusses decimal logarithms in {\sevenit Logarithmorum Chilias Prima}
1619  Ren\'e Descartes discovers analytical geometry
1629  Pierre de Fermat develops a rudimentary differential calculus
1634  G.P. de Roberval shows that the area under a cycloid is three times the area of its generating circle
1637  Pierre de Fermat claims to have proven Fermat's Last Theorem in his copy of Diophantus' {\sevenit Arithmetica}
1654  Blaise Pascal and Pierre de Fermat create the theory of probability
1655  John Wallis writes {\sevenit Arithmetica Infinitorum}
1658  Christopher Wren shows that the length of a cycloid is four times the diameter of its generating circle
1665  Isaac Newton invents his calculus
1668  Nicholas Mercator and William Brouncker discover an infinite series for the logarithm while attempting to calculate the area under a
hyperbolic segment
1671  James Gregory discovers the series expansion for the inverse-tangent function
1673  Gottfried Leibniz invents his calculus
1675  Isaac Newton invents an algorithm for the computation of functional roots
1691  Gottfried Leibniz discovers the technique of separation of variables for ordinary differential equations
1693  Edmund Halley prepares the first mortality tables statistically relating death rate to age
1696  Guillaume de L'H\^opital states his rule for the examination of indeterminate forms
1706  John Machin develops a quickly converging inverse-tangent series for $\pi$ and computes $\pi$ to 100 decimal places
1712  Brook Taylor develops Taylor series'
1722  Abraham De Moivre states De Moivre's theorem
1724  Abraham De Moivre studies mortality statistics and the foundation of the theory of annuities in {\sevenit Annuities on Lives}
1730  James Stirling publishes {\sevenit The Differential Method}
1733  Geralamo Saccheri studies what geometry would be like if Euclid's fifth postulate were false
1734  Leonhard Euler introduces the integrating factor technique for solving first order ordinary differential equations
1736  Leonhard Euler solves the Koenigsberg bridge problem
1739  Leonhard Euler solves the general homogeneous linear ordinary differential equation with constant coefficients
1742  Christian Goldbach conjectures that every even number greater than two can be expressed as the sum of two primes
1744  Leonhard Euler shows the existence of transcendental numbers
1748  Maria Agnesi discusses analysis in {\sevenit Instituzioni Analitiche ad Uso della Gioventu Italiana}
1761  Thomas Bayes proves Bayes' theorem
1796  Karl Gauss presents a method for constructing a heptadecagon using only a compass and straightedge and also shows that only
polygons with certain numbers of sides can be constructed
1797  Caspar Wessel associates vectors with complex numbers and studies complex number operations in geometrical terms
1799  Karl Gauss proves that every polynomial equation has a solution among the complex numbers
1806  Jean-Robert Argand associates vectors with complex numbers and studies complex number operations in geometrical terms
1807  Joseph Fourier first announces his discoveries about the trigonometric decomposition of functions
1811  Karl Gauss discusses the meaning of integrals with complex limits and briefly examines the dependence of such integrals on
the chosen path of integration
1815  Sim\'eon Poisson carries out integrations along paths in the complex plane
1817  Bernard Bolzano presents Bolzano's theorem---a continuous function which is negative at one point and positive at another
point must be zero for at least one point in between
1824  Niels Abel partially proves that the general quintic or higher equations do not have algebraic solutions
1822  Augustin-Louis Cauchy presents the Cauchy integral theorem for integration around the boundary of a rectangle
1825  Augustin-Louis Cauchy presents the Cauchy integral theorem for general integration paths---he assumes the function being
integrated has a continuous derivative
1825  Augustin-Louis Cauchy introduces the theory of residues
1825  Peter Dirichlet and Adrien Legendre prove Fermat's Last Theorem for n=5
1828  George Green proves Green's theorem
1829  Nikolai Lobachevski publishes his work on hyperbolic non-Euclidean geometry
1832  \'Evariste Galois presents a general condition for the solvability of algebraic equations
1832  Peter Dirichlet proves Fermat's Last Theorem for n=14
1837  Pierre Wantsel proves that doubling the cube and trisecting the angle are impossible with only a compass and straightedge
1841  Karl Weierstrass discovers but does not publish the Laurent expansion theorem
1843  Pierre-Alphonse Laurent discovers and presents the Laurent expansion theorem
1843  William Hamilton discovers the calculus of quaternions and deduces that they are non-commutative
1847  George Boole formalizes symbolic logic in {\sevenit The Mathematical Analysis of Logic}
1849  George Stokes shows that solitary waves can arise from a combination of periodic waves
1850  Alexandre Puiseux distinguishes between poles and branch points and introduces the concept of essential singular points
1850  George Stokes proves Stokes' theorem
1854  Bernhard Riemann introduces Riemannian geometry
1854  Arthur Cayley shows that quaternions can be used to represent rotations in four-dimensional space
1858  August M\"obius invents the M\"obius strip
1870  Felix Klein constructs an analytic geometry for Lobachevski's geometry thereby establishing its self-consistency and the logical
independence of Euclid's fifth postulate
1873  Charles Hermite proves that {\sevenit e} is transcendental
1878  Charles Hermite solves the general quintic equation by means of elliptic and modular functions
1873  Georg Frobenius presents his method for finding series solutions to linear differential equations with regular singular points
1882  Ferdinand Lindeman proves that $\pi$ is transcendental and that the circle cannot be squared with a compass and straightedge
1882  Felix Klein invents the Klein bottle
1895  Diederik Korteweg and Gustav de Vries derive the KdV equation to describe the development of long solitary water waves in a
canal of rectangular cross section
1896  Jacques Hadamard and Charles de La Vall\'ee-Poussin independently prove the prime number theorem
1899  David Hilbert presents a set of self-consistent geometric axioms in {\sevenit Foundations of Geometry}
1900  David Hilbert states his list of 23 problems which show where further mathematical work is needed
1901  \'Elie Cartan develops the exterior derivative
1903  C. Runge presents a fast Fourier transform algorithm
1908  Ernst Zermelo axiomatizes set theory
1912  L.E.J. Brouwer presents the Brouwer fixed-point theorem
1914  Srinivasa Ramanujan publishes {\sevenit Modular Equations and Approximations to $\pi$}
1928  John von Neumann begins devising the principles of game theory and proves the minimax theorem
1930  Casimir Kuratowski shows that the three cottage problem has no solution
1931  Kurt G\"odel shows that mathematical systems are not fully self-contained
1933  Karol Borsuk and Stanislaw Ulam present the Borsuk-Ulam antipodal-point theorem
1942  G.C. Danielson and Cornelius Lanczos develop a fast Fourier transform algorithm
1943  Kenneth Levenberg proposes a method for nonlinear least squares fitting
1948  John von Neumann mathematically studies self-reproducing machines
1949  John von Neumann computes $\pi$ to 2,037 decimal places using ENIAC
1950  Stanislaw Ulam and John von Neumann present cellular automata dynamical systems
1953  Nicholas Metropolis introduces the idea of thermodynamic simulated annealing algorithms
1955  Enrico Fermi, John Pasta, and Stanislaw Ulam numerically study a nonlinear spring model of heat conduction and discover solitary wave
type behavior
1960  C.A.R. Hoare invents the quicksort algorithm
1960  Irving Reed and Gustave Solomon present the Reed-Solomon error-correcting code
1961  Daniel Shanks and John Wrench compute $\pi$ to 100,000 decimal places using an inverse-tangent identity and an IBM-7090 computer
1962  Donald Marquardt proposes the Levenberg-Marquardt nonlinear least squares fitting algorithm
1963  Martin Kruskal and Norman Zabusky analytically study the Fermi-Pasta-Ulam heat conduction problem in the continuum limit and find
that the KdV equation governs this system
1965  Martin Kruskal and Norman Zabusky numerically study colliding solitary waves in plasmas and find that they do not disperse after collisions
1965  James Cooley and John Tukey present an influential fast Fourier transform algorithm
1966  E.J. Putzer presents two methods for computing the exponential of a matrix in terms of a polynomial in that matrix
1976  Kenneth Appel and Wolfgang Haken use a computer to solve the four-color problem
1983  Gerd Faltings proves the Mordell Conjecture and thereby shows that there are only finitely many whole number solutions for each
exponent of Fermat's Last Theorem
1985  Louis de Branges proves the Bieberbach Conjecture
1987  Yasumasa Kanada, David Bailey, Jonathan Borwein, and Peter Borwein use iterative modular equation approximations to elliptic
integrals and a NEC SX-2 supercomputer to compute $\pi$ to 134 million decimal places
1993  Andrew Wiles proves part of the Taniyama-Shimura Conjecture and thereby proves Fermat's Last Theorem

Geology

1620  Francis Bacon notices the jigsaw fit of the opposite shores of the Atlantic Ocean
1701  Edmund Halley suggests using the salinity and evaporation of the Mediterranean to determine the age of the Earth
1837  Louis Agassiz begins his glaciation studies which eventually demonstrate that the Earth has had at least one Ice Age
1862  Lord Kelvin attempts to find the age of the Earth by examining its cooling time and estimates that the Earth is
between 20--400 million years old
1903  George Darwin and John Joly claim that radioactivity is partially responsible for the Earth's heat
1907  Bertram Boltwood proposes that the amount of lead in uranium and thorium ores might be used to determine the Earth's
age and crudely dates some rocks to have ages between 410--2200 million years
1912  Alfred Wegener proposes that all the continents once formed a single landmass called Pangaea that broke apart via
continental drift
1913  Albert Michelson measures tides in the solid body of the Earth
1935  Charles Richter invents a logarithmic scale to measure the intensity of earthquakes
1953  Maurice Ewing and Bruce Heezen discover the Great Global Rift running along the Mid-Oceanic Ridge
1960  Harry Hess proposes that new sea floor might be created at mid-ocean rifts and destroyed at deep sea trenches
1963  F.J. Vine and D.H. Matthews explain the stripes of magnetized rocks with alternating magnetic polarities running
parallel to mid-ocean ridges as due to sea floor spreading and the periodic geomagnetic field reversals

Geography, Meteorology, Paleontology, Science Philosophy, and Science Publishing

25    Pomponius Mela formalizes the climatic zone system
1569  Gerardus Mercator issues the first Mercator projection map
1620  Francis Bacon analyzes the scientific method in his {\sevenit Great Instauration of Learning}
1686  Edmund Halley presents a systematic study of the trade winds and monsoons and identifies solar heating as the cause of
atmospheric motions
1686  Edmund Halley establishes the relationship between barometric pressure and height above sea level
1716  Edmund Halley suggests that aurorae are caused by magnetic effluvia'' moving along the Earth's magnetic field lines
1822  Gideon Mantell discovers the fossilized skeleton of an iguanodon dinosaur
1869  Joseph Lockyer starts the scientific journal {\sevenit Nature}
1909  Discovery of the Burgess Shale Cambrian fossil site
1920  Andrew Douglass proposes dendrochronology dating
1920  Milutin Milankovich proposes that long term climatic cycles may be due to changes in the eccentricity of the Earth's orbit and
changes in the Earth's obliquity
1947  Willard Libby introduces carbon-14 dating
1949  Edward Murphy states his law
1974  Donald Johanson and Tom Gray discover a 3.5 million-year-old female hominid fossil that is 40\% complete and name it Lucy''
1980  Luis Alvarez, Walter Alvarez, Frank Asaro, and Helen Michel propose that a giant comet or asteroid may have struck the Earth
approximately 65 million years ago thereby causing massive extinctions and enriching the iridium in the K-T layer
1984  Hou Xianguang discovers the Chengjiang Cambrian fossil site

Agriculture and Food Technology

-1800 Fermentation of dough, grain, and fruit juices is discovered
600   The moldboard plow is invented in eastern Europe
850   Coffee is invented in Arabia
1300  Arnau de Villanova develops alcohol distillation

Clothing and Textiles Technology

1733  John Kay patents the flying shuttle loom
1764  James Hargreaves invents the spinning jenny
1794  Eli Whitney patents the cotton gin
1801  Joseph-Marie Jacquard invents the Jacquard punched card loom
1856  William Perkin invents the first synthetic dye

Motor and Engine Technology

1698  Thomas Savery builds a steam-powered water pump for pumping water out of mines
1712  Thomas Newcomen builds a piston-and-cylinder steam-powered water pump for pumping water out of mines
1769  James Watt patents his first improved steam engine
1821  Michael Faraday builds an electricity-powered motor
1876  Nikolaus Otto designs a four-stroke internal-combustion engine
1888  Nikola Tesla patents the induction motor

Transportation Technology

-3500 Wheeled carts are invented
-3500 River boats are invented
-2000 Horses are tamed and used for transport
770   Iron horseshoes come into common use
1492  Leonardo da Vinci describes a flying machine
1662  Blaise Pascal invents a horse-drawn public bus which has a regular route, schedule, and fare system
1740  Jacques de Vaucanson demonstrates his clockwork powered carriage
1783  Joseph Montgolfier and \'Etienne Montgolfier launch the first hot air balloons
1801  Richard Trevithick builds a prototype steam powered railroad locomotive
1807  Isaac de Rivas makes a hydrogen gas powered vehicle
1814  George Stephenson builds the first practical steam powered railroad locomotive
1862  Jean Lenoir makes a gasoline-engine automobile
1868  George Westinghouse invents the compressed air locomotive brake
1900  Ferdinand von Zeppelin builds the first successful dirigible
1903  Orville Wright and Wilbur Wright fly the first motor-driven airplane
1908  Henry Ford develops the assembly line method of automobile manufacturing
1947  First supersonic flight
1969  First manned mission to the Moon
1981  First flight of the space shuttle

Underwater Technology

1716  Edmund Halley builds a diving bell
1801  Robert Fulton builds the first submarine
1819  Augustus Siebe invents a diving suit which receives air pumped down from the surface
1934  Charles Beebe dives to 3,028 feet using a bathysphere
1943  Jacques-Yves Cousteau makes the first dive with a compressed-air aqualung

Communication Technology

-3500 The Sumerians develop cuneiform writing and the Egyptians develop hieroglyphic writing
-1500 The Phoenicians develop an alphabet
-170  Parchment is discovered in Pergamum
105   Tsai Lun invents paper
350   The Chinese develop a method for printing pages using symbols carved on a wooden block
1450  The Chinese develop wooden block movable type printing
1454  Johannes Gutenberg finishes a printing press with metal movable type
1793  Claude Chappe establishes the first long-distance semaphore telegraph line
1831  Joseph Henry proposes and builds an electric telegraph
1835  Samuel Morse develops the Morse code
1843  Samuel Morse builds the first long distance electric telegraph line
1876  Alexander Graham Bell and Thomas Watson exhibit an electric telephone
1877  Thomas Edison patents the phonograph
1889  Almon Strowger patents the direct dial telephone
1901  Guglielmo Marconi transmits radio signals from Cornwall to Newfoundland
1925  John Baird transmits the first television signal
1958  Chester Carlson presents the first photocopier suitable for office use
1966  Charles Kao realizes that silica-based waveguides offer a practical way to transmit light via total internal reflection
1973  Akira Hasegawa and Fred Tappert propose the use of solitary waves to carry information in optical fibers
1977  Donald Knuth begins work on \TeX
1980  Linn Mollenauer, Rogers Stollen, and James Gordon demonstrate that solitary waves can be propagated through optical fibers
1991  Anders Olsson transmits solitary waves through an optical fiber with a data rate of 32 billion bits per second

Photography Technology

1826  Joseph Ni\'epce takes the first permanent photograph
1891  Thomas Edison patents the kinetoscopic camera''
1973  Fairchild Semiconductor releases the first large image forming CCD chip---100 rows and 100 columns

Calculator and Computer Technology

1617  John Napier discusses the Napier's bones calculating method in {\sevenit Rabdologia}
1622  William Oughtred invents the slide rule
1623  Wilhelm Schickard builds his 6-digit Calculating Clock'' that can add and subtract
1645  Blaise Pascal completes his 5-digit Pascaline'' that can add
1930  Vannevar Bush builds a partly electronic computer capable of solving differential equations
1946  Presper Eckert and John Mauchly announce ENIAC, the first practical entirely electronic computer
1948  William Shockley, Walter Brattain, and John Bardeen invent the transistor
1950  Alan Turing proposes the `Turing test'' criterion for an intelligent machine
1951  Presper Eckert and John Mauchly finish UNIVAC I, the first mass-produced electronic computer
1971  Texas Instruments releases the first easily portable electronic calculator
1977  Apple Computer releases the Apple II personal computer

Time Measurement Technology

-270  Ctesibius builds a popular water clock
-46   Julius Caesar and Sosigenes develop a solar calendar with leap years
1502  Peter Henlein builds the first pocketwatch
1582  Pope Gregory XIII, Aloysius Lilius, and Christopher Clavius introduce a Gregorian calendar with an improved leap year system
1656  Christian Huygens builds the first accurate pendulum clock
1737  John Harrison presents the first stable nautical chronometer, thereby allowing for precise longitude determination while at sea
1928  Joseph Horton and Warren Morrison build the first quartz crystal oscillator clock
1946  Felix Bloch and Edward Purcell develop nuclear magnetic resonance
1949  Harold Lyons develops an atomic clock based on the quantum mechanical vibrations of the ammonia molecule

Temperature and Pressure Measurement Technology

1592  Galileo Galilei builds a crude thermometer using the contraction of air to draw water up a tube
1643  Evangelista Torricelli invents the mercury barometer
1714  Gabriel Fahrenheit invents the mercury in glass thermometer
1864  Antoine Becquerel suggests an optical pyrometer
1892  Henri-Louis Le Ch\^atelier builds the first optical pyrometer

Microscope Technology

1590  Zacharias Janssen invents the microscope
1674  Anton van Leeuwenhoek invents the compound microscope
1932  Ernst Ruska builds the first electron microscope

Low Temperature Technology

1891  Z.F. Wroblewski condenses experimentally useful quantities of liquid air
1892  James Dewar invents the vacuum-insulated, silver-plated glass Dewar
1908  Heike Kammerlingh Onnes liquifies helium

Rocket and Missile Technology

1926  Robert Goddard launches the first liquid fuel rocket
1944  Wernher von Braun and Walter Dornberger launch the first V2 rocket
1958  Launch of the first ICBM

Materials Technology

-4000 Copper metallurgy is invented and copper is used for ornamentation
-3000 Bronze is used for weapons and armor
-1500 The Hittites develop crude iron metallurgy
-1200 Invention of steel when iron and charcoal are combined properly
700   Porcelain is invented in China
1839  Charles Goodyear invents vulcanized rubber
1909  Leo Baekeland presents the Bakelite hard thermosetting plastic
1931  Julius Nieuwland develops the synthetic rubber neoprene
1931  Wallace Carothers develops nylon
1953  Karl Ziegler discovers metallic catalysts which greatly improve the strength of polyethylene polymers

Lighting Technology

-3000 Candles are invented
1815  Humphry Davy invents the miner's safety lamp
1879  Thomas Edison patents the carbon-thread incandescent lamp

General Technology

-7000 Pottery is invented
-700  Invention of aqueducts
-640  Invention of coins
-400  Catapults are invented in Syracuse
-150  Hipparchus invents the astrolabe
-100  Glass-blowing is discovered in Syria
700   Windmills are invented in Persia
1050  Crossbows are invented in France
1249  Roger Bacon states formulas for gunpowder
1346  Cannon come into wide use
1480  Martin Behaim introduces the nautical astrolabe
1480  Leonardo da Vinci describes a workable parachute
1645  Otto von Guericke builds the first vacuum pump
1731  John Hadley invents the sextant
1800  Alessandro Volta announces his invention of the electric battery
1823  William Sturgeon invents the electromagnet
1840  Justus von Liebig invents artificial fertilizer
1867  Alfred Nobel patents dynamite
1880  John Milne invents the seismograph
1885  William Stanley invents the alternating current transformer
1903  Konstantin Tsiolkovsky begins a series of papers discussing the use of rocketry to reach outer space, space suits, and
colonization of the solar system
1917  Paul Langevin develops a sonar echolocation system
1925  Theodor Svedberg develops the ultra-centrifuge, thereby revolutionizing the determination of molecular weights
1935  Robert Watson-Watt devises a microwave radar
1945  First nuclear fission bomb exploded at the Trinity test site, about sixty miles northwest of Alamogordo, New Mexico
1952  First thermonuclear fusion bomb exploded
1952  Wernher von Braun discusses the technical details of a manned exploration of Mars in {\sevenit The Mars Project}
1953  Charles Townes makes the first maser
1954  Construction of the first nuclear power reactor
1960  Theodore Maiman makes the first laser

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