- -3000 The abacus is invented in the Tigris-Euphrates valley

- -1700 Egyptian mathematicians employ fractions

- -586 Thales of Miletus predicts a solar eclipse in 585 B.C.

- -530 Pythagoras studies propositional geometry and vibrating lyre strings

- -380 Hippocrates begins the scientific study of medicine

- -370 Eudoxus states the method of exhaustion

- -300 Euclid studies geometry as a deductive system in Elements and states the law of reflection in Catoptrics

- -230 Archimedes writes The Sand-Reckoner and computes $\pi$ to two decimal places

- -200 Apollonius writes On Conic Sections and names the ellipse, parabola, and hyperbola

- -200 Eratosthenes roughly determines the radius of the Earth

- -130 Hipparchus creates the magnitude scale of stellar apparent
luminosities and discovers the precession of the equinoxes

- -46 Julius Caesar orders the development of the Julian calendar

- 50 Cleomedes studies refraction

- 60 Hero of Alexandria writes Metrica,
Mechanics, Catoptrics, and
Pneumatics

- 130 Claudius Ptolemy tabulates angles of refraction for several media

- 250 Diophantus writes 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 a numeral representation to zero

- 1054 Chinese and American Indian astronomers observe the Crab supernova explosion

- 1202 Leonardo Fibonacci demonstrates the utility of Arabic numerals in his Book of the Abacus

- 1248 Roger Bacon writes formulas for gunpowder in his Epistola

- 1303 First recorded use of spectacles

- 1420 Al-Kashi computes $\pi$ to sixteen decimal places

- 1451 Nicholas of Cusa invents concave lens spectacles to treat nearsightedness

- 1480 Leonardo da Vinci describes a workable parachute

- 1490 Leonardo da Vinci describes capillary action

- 1492 Leonardo da Vinci describes a flying machine

- 1502 Peter Heinlein builds the first pocketwatch

- 1512 Nicholas Copernicus first states his heliocentric theory in Commentariolus

- 1520 Scipione del Ferro has a method for solving certain types of cubic equations

- 1521 Ferdinand Magellan observes the Magellanic Clouds during his circumnavigating expedition

- 1535 Niccolo Fontana Tartaglia has a method for solving certain types of cubic equations

- 1540 Michael Servetus discovers pulmonary circulation

- 1540 Lodovico Ferrari solves the quartic equation

- 1543 Andreas Vesalius publishes De Fabrica Corporis Humani which corrects Greek medical errors and revolutionizes medicine

- 1543 Nicholas Copernicus shows that his heliocentric theory simplifies planetary motion tables in De Revolutionibus de Orbium Coelestium

- 1546 Gerolamo Fracastoro proposes that epidemic diseases are caused by transferable seedlike entities

- 1559 Realdo Colombo discusses the circulation of blood in detail

- 1569 Gerardus Mercator issues the first Mercator projection map

- 1572 Tycho Brahe discovers his supernova in Cassiopeia

- 1576 Thomas Digges modifies the Copernican system by removing its outer edge and replacing the edge with a

- star filled unbounded space

- 1577 Tycho Brahe uses parallax to prove that comets are distant entities and not atmospheric phenomena

- 1581 Galileo Galilei notices the timekeeping property of the pendulum

- 1582 Pope Gregory XIII introduces the Gregorian calendar

- 1589 Galileo Galilei uses balls rolling on inclined planes to show that different weights fall with the same acceleration

- 1590 Zacharias Janssen invents the microscope

- 1592 Galileo Galilei builds a crude thermometer using air in a tube

- 1596 Ludolf van Ceulen computes $\pi$ to twenty decimal places

- 1603 Johann Bayer develops his system of star nomenclature

- 1604 Johannes Kepler's supernova in Serpens is observed

- 1604 Johannes Kepler describes how the eye focuses light

- 1608 Hans Lippershey tries to patent his refracting telescope

- 1609 Johannes Kepler states his first two empirical laws of planetary motion

- 1609 Galileo Galilei builds his first telescope

- 1610 Galileo Galilei discovers Callisto, Europa, Ganymede, and Io

- 1610 Galileo Galilei sees Saturn's rings but does not recognize that they are rings

- 1610 Johannes Kepler uses the dark night sky to argue for a finite universe

- 1611 M. de Dominis explains the rainbow

- 1611 Johannes Kepler discovers total internal reflection, a small angle refraction law, and thin lens optics

- 1613 Galileo Galilei uses sunspots to demonstrate the rotation of the sun

- 1614 John Napier discusses Napierian logarithms in Mirifici Logarithmorum Canonis Descriptio

- 1617 John Napier discusses the Napier's bones calculating method in Rabdologia

- 1617 Henry Briggs discusses decimal logarithms in Logarithmorum Chilias Prima

- 1619 Johannes Kepler explains the direction of cometary tails by postulating a solar wind

- 1619 Johannes Kepler states his third empirical law of planetary motion

- 1620 Francis Bacon notices the jigsaw fit of the opposite shores of the Atlantic Ocean

- 1620 Francis Bacon analyzes the scientific method in his Great Instauration of Learning

- 1621 Willebrord Snell states his law of refraction

- 1622 William Oughtred invents the slide rule

- 1628 William Harvey further studies blood circulation and compares the heart to a pump

- 1629 Pierre de Fermat develops a rudimentary differential calculus

- 1637 Ren\'e Descartes further develops and tests the theory of rainbows

- 1637 Pierre de Fermat claims to have proven Fermat's Last Theorem

- 1638 Galileo Galilei publishes Dialogues Concerning Two New Sciences

- 1640 Ismael Bullialdus suggests an inverse-square gravitational force law

- 1642 Blaise Pascal makes an adding machine

- 1643 Evangelista Torricelli invents the mercury barometer

- 1645 Otto von Guericke builds the first vacuum pump

- 1654 Blaise Pascal and Pierre de Fermat develop the theory of probability

- 1655 John Wallis writes Arithmetica Infinitorum

- 1655 Giovanni Cassini discovers Jupiter's great red spot

- 1656 Christian Huygens identifies Saturn's rings as rings and discovers Titan

- 1656 Christian Huygens builds the first highly accurate pendulum clock

- 1657 Pierre de Fermat introduces the principle of least time into optics

- 1658 Jan Swammerdam observes red blood cells under a microscope

- 1661 James Gregory proposes a reflecting telescope

- 1665 Giovanni Cassini determines the rotational speeds of Jupiter, Mars, and Venus

- 1665 Robert Hooke identifies cells

- 1665 Isaac Newton deduces the inverse-square gravitational force law from the ``falling'' of the moon

- 1665 Isaac Newton invents his calculus

- 1668 Isaac Newton constructs the first reflecting telescope

- 1668 Francesco Redi disproves theories of the spontaneous generation of living organisms

- 1668 John Wallis suggests the law of conservation of momentum

- 1672 Jean Richer and Giovanni Cassini measure the astronomical unit to within 7\%

- 1672 Giovanni Cassini discovers Rhea

- 1673 Gottfried Leibnitz invents his calculus

- 1674 Anton van Leuwenhoek invents the compound microscope

- 1675 Ole R\"omer uses the orbital mechanics of Jupiter's moons to estimate the speed of light

- 1675 Isaac Newton invents an algorithm for the computation of functional roots

- 1676 Anton van Leuwenhoek observes protozoa

- 1678 Christian Huygens states his principle of wavefront sources

- 1683 Anton van Leuwenhoek observes bacteria

- 1684 Isaac Newton proves that planets moving under an inverse-square force law will obey Kepler's laws

- 1687 Isaac Newton publishes his Principia Mathematica

- 1690 Jacques Bernoulli solves the isochrone problem

- 1691 Jean Bernoulli solves the catenary problem

- 1696 Guillaume de L'H\^opital states his rule for the examination of indeterminate forms

- 1697 Jean Bernoulli solves the brachistochrone problem

- 1698 Thomas Savery builds a steam-powered water pump for pumping water out of mines

- 1701 Giacomo Pylarini gives the first smallpox inoculations

- 1704 Isaac Newton publishes Opticks

- 1705 Edmond Halley predicts the periodicity of Halley's comet

- 1712 Thomas Newcomen builds a piston-and-cylinder steam-powered water pump for pumping water out of mines

- 1712 Brook Taylor develops Taylor's series'

- 1714 Gabriel Fahrenheit invents the mercury in glass thermometer

- 1716 Edmond Halley builds a diving bell

- 1718 Edmond Halley discovers stellar proper motions

- 1720 Edmond Halley puts forth an early form of Olbers' paradox

- 1728 James Bradley discovers the aberration of starlight and uses it to determine the speed of light to within 5\%

- 1733 Chester Moor Hall invents the achromatic lens refracting telescope

- 1733 Geralamo Saccheri studies what geometry would be like if Euclid's fifth postulate were false

- 1733 John Kay patents the flying shuttle loom

- 1737 John Harrison presents the first stable nautical chronometer, thereby allowing for precise longitude determination while at sea

- 1738 Daniel Bernoulli examines fluid flow in Hydrodynamica

- 1740 Jacques de Vaucanson demonstrates his clockwork powered carriage

- 1742 Colin Maclaurin discovers his spheroids

- 1744 Jean-Phillipe de Cheseaux puts forth an early form of Olbers' paradox

- 1747 Pierre-Louis Moreau de Maupertuis applies minimum principles to mechanics

- 1748 Maria Agnesi discusses analysis in Instituzioni Analitiche ad Uso della Gioventu Italiana

- 1750 Thomas Wright discusses galaxies and the shape of the Milky Way

- 1752 Benjamin Franklin shows that lightning is electricity

- 1758 John Dolland reinvents the achromatic lens

- 1761 Joseph Black discovers that ice absorbs heat without changing temperature when melting

- 1763 Claudius Aymand performs the first successful appendectomy

- 1766 Titius of Wittenberg finds the Titius-Bode rule

- 1766 Henry Cavendish discovers and studies hydrogen

- 1767 Joseph Priestly proposes an electrical inverse-square law

- 1769 James Watt patents his first improved steam engine

- 1771 Joseph Priestly discovers that plants convert carbon dioxide into oxygen

- 1772 Johann Bode publicizes the Titius-Bode rule

- 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

- 1781 William Herschel discovers Uranus

- 1783 Joseph Montgolfier and \'Etienne Montgolfier launch the first hot air balloons

- 1784 Charles Messier publishes his catalog of nebulae

- 1784 Edward Piggot discovers the first Cepheid variable star

- 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

- 1788 Joseph Lagrange presents his equations of motion in Mechanique Analytique

- 1793 Claude Chappe establishes the first long-distance semaphore telegraph line

- 1794 Eli Whitney patents the cotton gin

- 1795 Pierre Laplace discusses Newtonian black holes

- 1796 Edward Jenner develops a smallpox vaccination

- 1796 Pierre Laplace states his nebular hypothesis for the formation of the solar system from a nebula of gas and dust

- 1798 Henry Cavendish measures the gravitational constant and determines the mass of the Earth

- 1798 Count Rumford has the idea that heat is a form of energy

- 1799 Karl Gauss proves that every polynomial equation has a solution among the complex numbers

- 1800 Alessandro Volta announces his invention of the electric battery

- 1800 William Nicholson and Anthony Carlisle use electrolysis to separate water into hydrogen and oxygen

- 1800 William Herschel discovers infrared radiation

- 1801 Johann Ritter discovers ultraviolet radiation

- 1801 Robert Fulton builds the first submarine

- 1801 Thomas Young demonstrates the wave nature of light and the principle of interference

- 1801 Guiseppe Piazzi discovers the asteroid Ceres

- 1802 William Wollaston observes dark lines in the stellar spectrum

- 1803 John Dalton introduces atomic ideas into chemistry and states that matter is composed of atoms of different weights

- 1803 Thomas Young explains supernumerary rainbows

- 1807 Joseph Fourier first announces his discoveries about the trigonometric decomposition of functions

- 1807 Isaac de Rivas makes a hydrogen gas powered vehicle

- 1808 \'Etienne Malus discovers polarization by reflection

- 1809 \'Etienne Malus publishes the law of Malus

- 1809 Jean Lamarck revives the idea that acquired characteristics can be inherited in Philosophie Zoologique

- 1811 Amedeo Avogadro claims that equal volumes of gases should contain equal numbers of molecules

- 1811 Dominique Arago discovers the optical activity of quartz

- 1814 Joseph Fraunhofer studies the spectral lines of the sun

- 1814 George Stephenson builds the first practical steam locomotive

- 1816 Rene Laennec invents the stethoscope

- 1816 David Brewster discovers stress birefringence

- 1819 Augustus Siebe invents a diving suit which receives air pumped down from the surface

- 1820 Hans Oersted notices that a current in a wire can deflect a compass needle

- 1821 Michael Faraday builds an electricity-powered motor

- 1822 Joseph Fourier formally introduces the use of dimensions for physical quantities in his Theorie Analytique de la Chaleur

- 1823 William Sturgeon invents the electromagnet

- 1824 Sadi Carnot analyzes heat engines

- 1824 Niels Abel partially proves that the general quintic or higher equations do not have algebraic solutions

- 1825 Augustin Fresnel phenomenologically explains optical activity by introducing circular birefringence

- 1826 Joseph Ni\'epce takes the first permanent photograph

- 1826 Heinrich Olbers puts forth Olbers' paradox

- 1826 Simon Ohm states his law of electrical resistance

- 1827 Robert Brown discovers the Brownian motion

- 1828 George Green proves Green's theorem

- 1829 Nikolai Lobachevski publishes his work on hyperbolic non-Euclidean geometry

- 1831 Michael Faraday states his law of induction

- 1831 Michael Faraday begins his work on electrolysis

- 1831 Joseph Henry proposes an electromagnetic telegraph

- 1832 \'Evariste Galois presents a general condition for the solvability of algebraic equations

- 1834 William Hamilton states his dynamical principle

- 1834 Carl Jacobi discovers his ellipsoids

- 1834 Benoit-Pierre Clapeyron presents a formulation of the second law of thermodynamics

- 1834 Charles Babbage proposes an analytical engine calculating machine

- 1835 Gaspard de Coriolis deduces the Coriolis force

- 1838 Friedrich Bessel, T. Henderson, Friedrich Struve measure the parallax of stars

- 1839 Charles Goodyear invents vulcanized rubber

- 1840 Justus von Leibig invents artificial fertilizer

- 1842 Christian D\"oppler states the D\"oppler shift formula

- 1842 Crawford Long performs the first surgical operation using anasthesia

- 1843 Samuel Morse builds the first long distance electric telegraph line

- 1843 James Joule experimentally demonstrates that heat is a form of energy

- 1845 Michael Faraday discovers that light propagation in a material can be influenced by external magnetic fields

- 1845 Urbain LeVerrier observes a 35'' per century excess precession of Mercury's orbit

- 1845 Lord Rosse builds the Parsontown 72-inch optical reflecting telescope

- 1846 John Adams and Urbain LeVerrier predict the existence and location of Neptune from irregularities in the orbit of Uranus

- 1846 Johann Galle discovers Neptune

- 1847 Hermann Helmholtz presents a formulation of the first law of thermodynamics

- 1847 Ignaz Semmelweis studies and prevents the transmission of puerperal fever

- 1848 Louis Pasteur discovers stereoisomers

- 1848 Lord Kelvin discovers the absolute zero point of temperature

- 1849 Armand Fizeau measures the speed of light to within 5\%

- 1850 George Stokes proves Stokes' theorem

- 1850 Edouard Roche finds the limit of tidal destruction for a body held together only by its self gravity

- 1850 Lord Rosse discovers that some of the nebulous objects show spiral structure

- 1851 Jean Bernard Foucalt shows the Earth's rotation with a huge pendulum

- 1852 George Stokes defines the Stokes parameters of polarization

- 1852 James Joule and Lord Kelvin demonstrate that a rapidly expanding gas cools

- 1854 Georg Riemann introduces Riemannian geometry

- 1856 Louis Pasteur states that microorganisms produce fermentation

- 1858 Charles Darwin and Alfred Wallace independently propose natural selection theories of evolution

- 1859 James Maxwell discovers the distribution law of molecular velocities

- 1860 Gustav Kirchoff and Robert Bunsen discover that each element has its own distinct set of spectral lines

- 1862 Louis Pasteur conclusively disproves the spontaneous generation of living organisms

- 1862 Jean Lenoir makes a gasoline-engine automobile

- 1864 James Maxwell publishes his papers on a dynamical theory of the electromagnetic field

- 1864 John Herschel publishes the General Catalog

- 1864 Antoine Becquerel suggests an optical pyrometer

- 1865 August Kekul\'e realizes that benzene is composed of carbon and hydrogen atoms in a hexagonal ring

- 1865 Gregor Mendel presents his experiments on the crossbreeding of pea plants

- 1867 Alfred Nobel patents dynamite

- 1870 Rudolph Clausius proves the scalar virial theorem

- 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

- 1870 Louis Pasteur and Robert Koch establish the germ theory of disease

- 1871 John Rayleigh discusses the blue sky law and sunsets

- 1871 Dmitri Mendel\'eyev systematically examines the periodic table and predicts the existence of gallium, scandium, and germanium

- 1872 Ludwig Boltzman states the Boltzman equation

- 1873 James Maxwell states that light is an electromagnetic phenomenon

- 1873 Johannes van der Waals introduces the idea of weak attractive forces between molecules

- 1873 Charles Hermite proves that
`e`is transcendental

- 1874 Lord Kelvin formally states the second law of thermodynamics

- 1875 John Kerr discovers the electrically induced birefringence of some liquids

- 1876 Nikolaus Otto designs a four-cycle engine

- 1876 Alexander Bell and Thomas Watson exhibit an electric telephone

- 1877 Thomas Edison patents the phonograph

- 1878 Josiah Gibbs further develops thermodynamics

- 1878 Charles Hermite solves the general quintic equation by means of elliptic and modular functions

- 1879 Thomas Edison patents the carbon-thread incandescent lamp

- 1879 Josef Stefan observes that the total radiant flux from a black-body is proportional to the fourth power of its temperature

- 1880 John Milne invents the seismograph

- 1881 Louis Pasteur develops an anthrax vaccine

- 1882 Simon Newcomb observes a 43'' per century excess precession of Mercury's orbit

- 1882 Ferdinand Lindeman proves that $\pi$ is transcendental and that the circle cannot be squared with a straightedge and compass

- 1885 Louis Pasteur develops a rabies vaccine

- 1885 Henri Poincar\'e introduces catastrophe theory

- 1885 Johann Balmer finds a mathematical expression for observed hydrogen line wavelengths

- 1885 William Stanley invents the alternating current transformer

- 1887 Albert Michelson and Edward Morley do not detect the ether drift

- 1887 Heinrich Hertz discovers the photoelectric effect

- 1888 Heinrich Hertz discovers radio waves

- 1888 John Dreyer publishes the New General Catalog

- 1888 Nikola Tesla patents the induction motor

- 1888 Henry Le Ch\^atelier states Le Ch\^atelier's Principle

- 1889 Roland von E\"otv\"os shows that gravitational mass and inertial mass are the same to within one part in one billion

- 1890 Emil von Behring discovers antitoxins and uses them to develop tetanus and diptheria vaccines

- 1890 Albert Michelson proposes the stellar interferometer

- 1891 Thomas Edison patents the ``kinetescopic camera''

- 1892 Henry Le Ch\^atelier builds the first optical pyrometer

- 1893 Ernst Mach states Mach's principle---first constructive attack on the idea of Newtonian absolute space

- 1893 Wilhelm Wien discovers the displacement law for a black-body's maximum specific intensity

- 1893 Edward Maunder discovers long-term variations in solar activity

- 1895 Wilhelm R\"ontgen discovers X-rays

- 1895 Pierre Curie discovers that magnetization is proportional to magnetic field strength

- 1896 Antoine Becquerel discovers the radioactivity of uranium

- 1896 Arnold Sommerfield solves the half-plane diffraction problem

- 1896 Pieter Zeeman studies the splitting of spectral lines in magnetic fields

- 1897 Joseph Thomson discovers the electron

- 1897 Alvan Clark builds the Yerkes 40-inch optical refracting telescope

- 1897 Martinus Beijerinck discovers viruses

- 1898 Marie Curie and Pierre Curie isolate and study radium and polonium

- 1899 Ernest Rutheford discovers that uranium radiation is composed of positively charged alpha particles and

- negatively charged beta particles

- 1900 Paul Villard observes gamma rays

- 1900 Ferdinand von Zeppelin builds the first successful dirigible

- 1900 Johannes Rydberg refines the expression for observed hydrogen line wavelengths

- 1900 Max Planck states his radiation law and Planck's constant

- 1901 Guglielmo Marconi transmits radio signals from Cornwall to Newfoundland

- 1902 James Jeans finds the gravitational collapse length scale

- 1902 Phillip Lenard observes that maximum photoelectron energy is independent of illuminating intensity

- 1903 Orville Wright and Wilbur Wright fly the first motor-driven airplane

- 1904 John Poynting shows that radiation has momentum and exerts pressure

- 1905 Albert Einstein completes his theory of special relativity

- 1905 Albert Einstein explains the photoelectric effect

- 1905 Albert Einstein explains the Brownian motion as due to molecular collisions

- 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

- 1906 Walther Nernst presents a formulation of the third law of thermodynamics

- 1906 Frederick Hopkins suggests the existence of vitamins

- 1906 Arthur Eddington begins his statistical study of stellar motions

- 1907 Albert Einstein introduces Principle of Equivalence of Gravitation and Inertia

- 1907 Ivan Pavlov demonstrates conditioned responses with salivating dogs

- 1908 George Hale discovers the magnetic nature of sunspots

- 1908 Henrietta Leavitt discovers the Cepheid period-luminosity relation

- 1908 Heike Kammerlingh Onnes liquifies helium

- 1908 Hans Geiger and Ernest Rutheford invent the Geiger counter

- 1909 Hans Geiger and E. Marsden discover large angle deflections of alpha particles by thin metal foils

- 1909 Ernest Rutheford and Thomas Royds demonstrate that alpha particles are doubly ionized helium atoms

- 1910 Ejnar Hertzsprung and Henry Russell study the relation between magnitudes and spectral types of stars

- 1910 Albert Einstein finds the Einstein-Smoluchowski formula for the attenuation coefficient due to density fluctuations in a gas

- 1911 Ernest Rutheford explains the Geiger-Marsden experiment by invoking the nuclear atom

- 1911 Heike Kammerlingh Onnes discovers superconductivity

- 1912 Victor Hess discovers that the ionization of air increases with altitude indicating the existence of cosmic radiation

- 1912 Pieter Debye discovers the T-cubed law for the low temperature heat capacity of a nonmetallic solid

- 1912 Max von Laue suggests using lattice solids to diffract X-rays

- 1912 W. Friedrich and P. Knipping diffract X-rays in zinc blende

- 1913 William Lawrence Bragg and William Henry 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 first quantum model of the atom

- 1913 Robert Millikan measures the fundamental unit of charge

- 1913 Albert Michelson measures tides in the solid body of the Earth

- 1914 Srinivasa Ramanujan begins work with Godfrey Hardy in Cambridge, England

- 1914 W. Adams determines an incredibly high density for Sirius B

- 1914 James Franck and Gustav Hertz observe atomic excitation

- 1914 Ernest Rutheford suggests that the positively charged atomic nucleus contains protons

- 1915 Albert Einstein completes his theory of general relativity

- 1915 Karl Schwarzschild solves Einstein's field equations for spherically symmetric systems

- 1916 Sydney Chapman and D. Enskog systematically develop a kinetic theory of gases

- 1916 Gilbert Lewis and Irving Langmuir formulate an electron shell model of chemical bonding

- 1916 Arnold Sommerfield makes a modified Bohr atom model with elliptic orbits to explain relativity fine structure

- 1917 Albert Einstein introduces the idea of stimulated radiation emission

- 1917 Willem de Sitter derives an isotropic static cosmological model with a cosmological constant and

- predicts the cosmological redshift

- 1917 Mount Wilson 100-inch optical reflecting telescope begins operation

- 1918 Harlow Shapley demonstrates that globular clusters surround our galaxy like a halo and are not centered on the Earth

- 1918 J. Lense and Hans Thirring find Lense-Thirring precession

- 1919 James Jeans discovers that the dynamical constants of motion determine the distribution function for a system of particles

- 1919 Arthur Eddington leads a solar eclipse expedition which claims to detect gravitational deflection of light by the sun

- 1920 Harlow Shapely and Heber Curtis debate whether or not the spiral nebulae lie within the Milky Way

- 1920 Meghnad Saha states his ionization equation

- 1921 A. Lande introduces the Lande g-factor

- 1922 Arthur Compton studies electron photon scattering

- 1922 Vesto Slipher summarizes his findings of systematic redshifts of the spiral nebulae

- 1922 Otto Stern and Walter Gerlach show ``space quantization''

- 1923 Pieter Debye publishes a statistical treatment of electrolytes

- 1923 Edwin Hubble resolves the Shapely-Curtis debate by finding Cepheids in Andromeda

- 1923 Louis de Broglie suggests that electrons may have undulatory properties

- 1924 Wolfgang Pauli states his exclusion principle

- 1924 Jagadis Bose and Albert Einstein introduce Bose-Einstein statistics

- 1924 Arthur Eddington develops the main-sequence mass-luminosity relationship

- 1925 George Uhlenbeck and Samuel Goudsmit postulate electron spin

- 1925 E. Ising introduces his model of ferromagnetism as a cooperative spin phenomenon

- 1925 John Baird transmits the first television signal

- 1925 Pierre Auger discovers the Auger autoionization process

- 1926 Enrico Fermi discovers the spin-statistics connection

- 1926 Paul Dirac introduces Fermi-Dirac statistics

- 1926 R. Fowler uses Fermi-Dirac statistics to explain white dwarf stars

- 1926 Erwin Schr\"odinger states his nonrelativistic quantum wave equation

- 1926 Robert Goddard launches the first liquid fuel rocket

- 1927 George Lema\^itre proposes a rudimentary Big Bang universe

- 1927 Jan Oort proves the Milky Way is rotating and deduces rotational speeds

- 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

- 1927 Ira Bowen explains unidentified spectral lines from space as forbidden transition lines

- 1928 J. Johnson discovers Johnson noise in a resistor

- 1928 H. Nyquist derives the fluctuation-dissipation relationship for a resistor to explain Johnson noise

- 1928 Paul Dirac states his relativistic electron quantum wave equation

- 1928 C. Darwin and W. Gordon solve the Dirac equation for a Coulomb potential

- 1928 Alexander Fleming discovers penicillin

- 1929 Edwin Hubble discovers the expansion of the universe

- 1929 Phoebus Levene discovers DNA

- 1929 O. Klein discovers the Klein paradox

- 1930 Robert Trumpler discovers absorption by interstellar dust

- 1930 Paul Dirac introduces electron hole theory

- 1930 Erwin Schr\"odinger predicts the zitterbewegung motion

- 1930 Clyde Tombaugh discovers Pluto

- 1930 Fritz London explains van der Waals forces as due to the interacting fluctuating dipole moments between molecules

- 1930 Subrehmanyan Chandrasekhar discovers the white dwarf maximum mass limit

- 1931 Kurt G\"odel shows that mathematical systems are not fully self-contained

- 1931 Ir\`ene Curie and Fr\'ed\'eric Joliot Curie observe but misinterpret neutron scattering in parafin

- 1932 John Cockcroft and Thomas Walton split lithium and boron nuclei using proton bombardment

- 1932 James Chadwick discovers the neutron

- 1932 Carl Anderson discovers the positron

- 1932 Ernst Ruska builds the first electron microscope

- 1932 Karl Jansky discovers radio noise from the Milky Way

- 1933 Wolfgang Pauli puts forth his neutrino hypothesis

- 1933 Fritz Zwicky applies the virial theorem to the Coma cluster and obtains evidence for unseen mass

- 1934 Walter Baade and Fritz Zwicky propose the idea of neutron stars and suggest that supernovae

- might be created by the collapse of a normal star to a neutron star

- 1934 Grote Reber discovers the radio source Cygnus A

- 1934 Ernest Lawrence and M. Livingston invent the cyclotron

- 1934 Leo Szilard realizes that nuclear chain reactions may be possible

- 1934 Enrico Fermi formulates his theory of beta decay

- 1935 Hideki Yukawa presents a theory of strong interactions and predicts mesons

- 1935 Albert Einstein, B. Podolsky, and Nathan Rosen put forth the EPR paradox

- 1935 Niels Bohr resolves the EPR paradox

- 1935 Charles Richter invents a scale to measure the strength of earthquakes

- 1935 Robert Watson-Watt devises a microwave radar

- 1936 Edwin Hubble introduces the spiral, barred spiral, elliptical, and irregular galaxy classifications

- 1937 Paul Dirac states his large dimensionless number cosmological hypothesis

- 1937 H. Hellmann finds the Hellmann-Feynman theorem

- 1937 Carl Anderson, J. Street, and E. Stevenson discover the muon

- 1937 Fritz Zwicky states that galaxies could act as gravitational lenses

- 1937 Theodor Dobzhansky links evolution and genetic mutation in Genetics and the Origin of the Species

- 1938 A coelacanth is found off the coast of southern Africa

- 1939 Richard Feynman finds the Hellmann-Feynman theorem

- 1939 Hans Bethe and Carl von Weizsacker propose the proton-proton chain as the thermonuclear energy source for the sun

- 1939 Robert Oppenheimer and G. Volkoff calculate the first neutron star models

- 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

- 1939 Rupert Wildt realizes the importance of the negative hydrogen ion for solar opacity

- 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

- 1941 A. McKellar observes the cosmic microwave background radiation in the excitation of CN doublet lines

- 1942 J. Doob states his theorem on Gaussian-Markoff processes

- 1942 J. Duyvendak, N. Mayall, and Jan Oort deduce that the Crab nebula is a remnant of the 1054 supernova

- observed by Chinese astronomers

- 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 running backwards in space-time

- 1942 Hannes Alfv\'en predicts magnetohydrodynamic waves in plasmas

- 1942 Danielson and C. Lanczos implement the fast Fourier transform algorithm

- 1943 Jacques-Yves Cousteau makes the first dive with a compressed-air aqualung

- 1943 Kenneth Levenberg proposes a method for nonlinear least squares fitting

- 1943 Carl Seyfert identifies six spiral galaxies with unusually broad emission lines

- 1944 Hendrick van de Hulst predicts the 21 cm line of hydrogen

- 1944 Werner von Braun and Walter Dornberger launch the first V2 rocket

- 1944 Oswald Avery finds evidence indicating that DNA carries genetic properties

- 1945 First thermonuclear fission bomb exploded at Alamogordo in the New Mexico desert

- 1946 John Eckert and John Mauchley finish ENIAC, the first electronic computer

- 1947 First supersonic flight

- 1947 Willis Lamb and Robert Retheford measure the Lamb-Retheford shift

- 1947 Cecil Powell discovers the pi-meson

- 1947 Richard Feynman presents his propagator approach to quantum electrodynamics

- 1947 Palomar 200-inch optical reflecting telescope begins operation

- 1947 Willard Libby introduces carbon-14 dating

- 1948 George Gamow, Ralph Alpher, and Robert Herman formulate the Big Bang theory and predict the cosmic microwave background

- 1948 Hermann Bondi, Thomas Gold, and Fred Hoyle propose steady state cosmologies

- 1948 William Shockley, Walter Brattain, and John Bardeen invent the transistor

- 1948 Hendrik Casimir predicts a rudimentary attractive Casimir force on a parallel plate capacitor

- 1948 John von Neumann mathematically studies self-reproducing machines

- 1949 Herbert Friedman detects solar X-rays

- 1950 Alfred Hershey and Martha Chase prove that DNA is the genetic material in bacteriophages

- 1950 Jan Oort suggests the presence of a cometary Oort cloud

- 1950 Alan Turing proposes the ``Turing test'' criterion for an intelligent machine

- 1951 Harold Ewen and Edward Purcell observe the 21 cm line of hydrogen

- 1951 John Eckert and John Mauchley finish UNIVAC I, the first mass-produced electronic computer

- 1952 Walter Baade distinguishes between Cepheid I and Cepheid II variable stars

- 1952 Jonas Salk develops the first polio vaccine

- 1952 First thermonuclear fusion bomb exploded

- 1952 Hermann Bondi publishes his hydrodynamic spherical accretion model

- 1953 Frederick Reines and Clyde Cowan detect neutrinos

- 1953 Fred Hoyle predicts a carbon-12 reasonance to allow stellar triple alpha reactions at reasonable stellar interior temperatures

- 1953 James Watson, Francis Crick, Maurice Wilkins, and Rosalind Franklin elucidate the structure of DNA using X-ray

- diffraction studies

- 1953 Nicholas Metropolis introduces the idea of thermodynamic simulated annealing algorithms

- 1953 Max Perutz and John Kendrew determine the structure of hemoglobin using X-ray diffraction studies

- 1953 Charles Townes makes the first maser

- 1954 Construction of the first nuclear power reactor

- 1954 Walter Baade and R. Minkowski identify the extragalactic optical counterpart of the radio source Cygnus A

- 1954 R. Luders derives the PCT theorem

- 1954 Chen Yang and R. Mills investigate a theory of hadronic isospin by demanding local gauge invariance under

- isotopic spin space rotations---first non-Abelian gauge theory

- 1956 Lyman Spitzer predicts coronal gas around the Milky Way

- 1956 Herbert Friedman detects hints of the X-ray background

- 1956 R. Hanbury-Brown and R. Twiss complete the correlation interferometer

- 1956 Chen Yang and Tsung Lee propose weak force violation of parity

- 1956 Chien Wu discovers weak force violation of parity in decaying cobalt

- 1957 A.S. Kompaneets derives his Compton scattering Fokker-Planck equation

- 1957 Sputnik I is launched---first orbiting satellite

- 1957 Peter Scheuer publishes his P(D) method for obtaining source counts of spatially unresolved sources

- 1957 John Bardeen, Leon Cooper and Robert Schrieffer develop a theory of superconductivity

- 1957 Richard Feynman, Murray Gell-Mann, Robert Marshak, and E. Sudarshan propose a V-A Lagrangian for weak interactions

- 1957 John Wheeler discusses the breakdown of classical general relativity near singularities and the need for quantum gravity

- 1958 Launch of the first ICBM missile

- 1958 Rudolf M\"ossbauer finds the M\"ossbauer crystal recoil effect

- 1958 E. Schatzman, B. Harrison, M. Wakano, and J. Wheeler show that white dwarfs are unstable to inverse beta decay

- 1958 M. Spaarnay verifies the Casimir effect

- 1959 Y. Aharonov and D. Bohm predict the Aharonov-Bohm effect

- 1960 R. Chambers experimentally confirms the Aharonov-Bohm effect

- 1960 R. Pound and G. Rebka test the gravitational redshift predicted by the general relativity equivalence principle

- 1960 Theodore Maiman makes the first laser

- 1960 Owens Valley 27-meter radio telescopes begin operation

- 1960 Martin Ryle tests Earth rotation aperature synthesis

- 1960 C. Hoare invents the quicksort algorithm

- 1961 Yuri Gagarin becomes the first human in space

- 1961 Murray Gell-Mann and Yuval Ne'eman discover the Eightfold Way patterns---SU(3) group

- 1961 C. Hayashi publishes his work on the Hayashi track

- 1961 Jeffery Goldstone considers the breaking of global phase symmetry

- 1962 Donald Marquardt proposes the Levenberg-Marquardt nonlinear least squares fitting algorithm

- 1962 R. Giacconi, H. Gursky, F. Paolini, and B. Rossi formally discover the X-ray background and Sco X-1

- 1962 Mariner 2 is the first mission to Venus

- 1962 A. Bennett publishes the revised 3C catalog of radio sources

- 1963 Maarten Schmidt identifies the first ``quasi-stellar object''

- 1963 Roy Kerr solves Einstein's field equations for uncharged rotating black holes

- 1963 Fred Hoyle and William Fowler conceive the idea of supermassive stars and suggest they may be associated with active galaxies

- 1963 Murray Gell-Mann and George Zweig propose the quark/aces model

- 1963 Publication of The Feynman Lectures on Physics

- 1964 Subrehmanyan Chandrasekhar and Richard Feynman develop a general relativistic theory of stellar pulsations and show

- that supermassive stars are subject to a general relativistic instability

- 1964 Martin Ryle's 1-mile radio interferometer begins operation

- 1964 P. Higgs considers the breaking of local phase symmetry

- 1964 Irwin Shapiro predicts a gravitational time delay of radiation travel as fourth test of general relativity

- 1964 Val Fitch and James Cronin see CP violation in the decay of K mesons

- 1964 Roger Penrose proves that an imploding star will necessarily produce a singularity once it has formed an event horizon

- 1965 Edward Harrison solves Olbers' paradox

- 1965 Owens Valley 40-meter radio telescope begins operation

- 1965 Arno Penzias and Robert Wilson discover the cosmic microwave background radiation

- 1965 Mariner 4 sends the first clear pictures of Mars

- 1965 E. Newman solves Einstein's field equations for charged rotating black holes

- 1966 Stephen Hawking and George Ellis show that any plausible general relativistic cosmology is singular

- 1966 R. Sachs and A. Wolfe theoretically predict microwave background fluctuation amplitudes

- 1967 Steven Weinberg puts forth his electroweak gauge theory

- 1967 First VLBI images---183 km baseline

- 1967 Venera 4 sends the first data from below clouds of Venus

- 1967 Pulsars discovered by Anthony Hewish and Jocelyn Bell

- 1968 Thomas Gold proposes that pulsars are rotating neutron stars

- 1968 Georges Charpak and Roger Bouclier build the first multiwire proportional mode particle detection chamber

- 1969 First manned mission to the moon

- 1969 Observations start at Big Bear Solar Observatory

- 1969 W. Cocke, H. Disney, and D. Taylor discover the Crab nebula pulsar thus connecting supernovae, neutron stars, and pulsars

- 1969 Lewis Snyder, David Buhl, B. Zuckerman, and Patrick Palmer find interstellar formaldehyde

- 1970 Hamilton Smith and Daniel Nathans discover a DNA cutting enzyme

- 1970 George Carruthers observes molecular hydrogen in space

- 1970 Sheldon Glashow, J. Iliopoulos, and L. Maiani propose the charm quark

- 1970 Launch of Uhuru---first dedicated X-ray satellite

- 1971 Identification of Cygnus X-1/HDE 226868 as a binary black hole candidate system

- 1971 Gerard 't Hooft shows that the Glashow-Salam-Weinberg electroweak model can be renormalized

- 1973 David Politzer proposes the asymptotic freedom of quarks

- 1974 Mariner 10 passes by and photographs Mercury

- 1974 Launch of the Ariel V X-ray satellite

- 1974 Burton Richter and Samuel Ting discover the J/$\psi$ meson implying the existence of the charm quark

- 1974 Kenneth Wilson develops the renormalization group technique for treating phase transitions

- 1974 Donald Johanson and Tom Gray discover a 3.5 million-year-old female hominid fossil that is 40\% complete and name it ``Lucy''

- 1974 Stephen Hawking discusses blackbody radiation and particle emission from black holes

- 1975 Russell Hulse and Joseph Taylor identify PSR 1913+16 as a binary pulsar

- 1975 M. Perl discovers the tauon

- 1975 The Altair 8800 personal computer is released

- 1976 Viking I and II land on Mars

- 1976 The Vela and ANS X-ray satellites discover X-ray bursts

- 1976 K. Appel and W. Haken use a computer to prove the Four-Color Theorem

- 1976 A. 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 Donald Knuth begins work on \TeX

- 1977 Christopher McKee and Jeremiah Ostriker propose a three component theory of the interstellar medium

- 1977 S. Herb finds the upsilon reasonance implying the existence of the beauty quark

- 1978 Launch of the Einstein X-ray satellite (HEAO-2)---first X-ray photographs of astronomical objects

- 1979 Launch of the Hakucho X-ray satellite (ASTRO-A)

- 1979 D. Walsh, Robert Carswell, and R. Weymann discover the first gravitational lens

- 1980 Completion of construction of the VLA

- 1980 Alan Guth proposes the inflationary universe as a possible solution to the horizon and flatness problems

- 1981 Chinese scientists clone a golden carp

- 1983 Launch of the EXOSAT X-ray satellite

- 1983 Launch of the Tenma X-ray satellite (ASTRO-B)

- 1983 Carlo Rubbia and Simon van der Meer find the W$^\pm$ and Z$^0$ intermediate vector bosons

- 1983 Launch of the IRAS satellite

- 1984 Alec Jeffreys devises a DNA fingerprinting method

- 1985 Louis de Branges proves the Bierbach Conjecture

- 1987 Observation of supernova 1987A in the Large Magellanic Cloud

- 1987 Alex Muller and Georg Bednorz discover high temperature ceramic superconductors

- 1987 Launch of the Ginga X-ray satellite (ASTRO-C)

- 1989 The Z$^0$ intermediate vector boson reasonance width indicates three quark-lepton generations

- 1989 Identification of GS2023+338/V404 Cygni as a binary black hole candidate system

- 1989 Launch of the COBE satellite

- 1990 Launch of the ROSAT X-ray satellite---first imaging X-ray sky survey

- 1992 The COBE satellite indicates anisotropy in the cosmic microwave background

- 1993 Launch of the Asca X-ray satellite (ASTRO-D)

Please note that this page is still under construction. Thank you for your patience.