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

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\%

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

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

-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

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

-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)

-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

-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

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

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

-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

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

-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

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

-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

1590 Zacharias Janssen invents the microscope

1674 Anton van Leeuwenhoek invents the compound
microscope

1932 Ernst Ruska builds the first electron
microscope

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

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

-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

-3000 Candles are invented

1815 Humphry Davy invents the miner's safety
lamp

1879 Thomas Edison patents the carbon-thread
incandescent lamp

-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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