c. 2725 B.C. - Imhotep in Egypt considered the first medical doctor

c. 2540 B.C. - Pyramids of Egypt constructed

c. 2000 B.C. - Chinese discovered magnetic attraction

c. 700 B.C. - Greeks discovered electric attraction produced by rubbing amber

c. 600 B.C. - Anaximander discovered the ecliptic (the angle between the plane of the earth's rotation and the plane of the solar system)

c. 600 B.C. - Thales proposed that nature should be understood by replacing myth with logic; that all matter is made of water

c. 585 B.C. - Thales correctly predicted solar eclipse

c. 530 B.C. - Pythagoras developed mathematical theory

c. 500 B.C. - Anaximenes introduced the ideas of condensation and rarefaction

c. 450 B.C. - Anaxagoras proposed the first clearly materialist philosophy - the universe is made entirely of matter in motion

c. 370 B.C. - Leucippus and Democritus proposed that matter is made of small, indestructible particles

335 B.C. - Aristotle established the Lyceum; studied philosophy, logic

c. 300 B.C. - Euclid wrote "Elements", a treatise on geometry

c. 300 B.C. - Aristarchus proposed that the earth revolves around the sun; calculated diameter of the earth

c. 300 B.C. - The number of volumes in the Library of Alexandria reached 500,000

c. 220 B.C. - Archimedes made discoveries in mathematics and mechanics

c. 150 A.D. - Ptolemy studied mathematics, science, geography; proposed that the earth is the center of the solar system

190 - Chinese mathematicians calculated pi to five decimal places

271 - Chinese mathematicians invented the magnetic compass

415 - A mob of rioters burned down the Library of Alexandria, and much of the recorded knowledge of the western world was lost

450-1000 - the "Dark Ages" in Europe

1232 - Rockets invented in China to defend city of Kaifeng against Mongol invaders

1252 - Pope Innocent IV approved the use of torture in witchcraft trials

1269 - Maricourt used compass to discover that a magnet is encircled by lines which terminate on two poles

1348 - The plague appeared in Europe

1390 - The first paper mill began operating in Germany

1455 - The Gutenberg Bible became the first book printed with movable metal type

1508-1510 Leonardo da Vinci compiled notebooks on mechanics, astronomy, anatomy, and his inventions

1543 - Copernicus formed the hypothesis that the planets revolve around the sun.

1543 - Vasalius published treatise on human anatomy

1570 - Brahe discovered supernova in constellation Cassiopeia

1600 - Gilbert discovered that electricity occurs in things other than amber; wrote a book on magnetism

1608 - Lippershey invented the telescope

1609 - Galileo built 20X telescope, discovered craters and mountains on the moon

1609 - Kepler announced his 1st and 2nd laws

1613 - Galileo discovered sunspots

1614 - Napier discovered logarithms

1616 - Galileo called to Rome and ordered to stop supporting the Copernican theory

1619 - Kepler announced his 3rd law

1619 - The first slaves transported to America

1620 - Bacon published "Novum Organum" (scientific method and inductive reasoning)

1621 - Snell discovered the law of refraction

1628 - Harvey published a book describing blood circulation

1633 - The Inquisition denounced Galileo

1637 - Descartes Published "Geometry"

1638 - Galileo published "Discourses Concerning Two New Sciences", summarizing the principles of mechanics

1642 - Pascal invented the mechanical adding machine

1650 - Archbishop Usher estimated by reading the Bible that the earth was created on October 23, 4004 BC at 9:00 AM

1652 - Pascal discovered laws of fluid pressure

1654 - Guericke invented the vacuum pump

1660 - Redi disproved theory of spontaneous generation with experiment on flies

1666 - Newton invented the calculus

1666 - Newton discovered glass prism separates white light into spectrum

1675 - Leibniz independently invented the calculus

1687 - Newton published "Principia", describing the laws of motion

1690 - Locke published "Essay Concerning Human Understanding" (empiricism, tabula rasa)

1692 - The first witchcraft trials in Salem, Massachusetts

1704 - Newton published "Opticks"

1738 - Bernoulli proposed laws of fluid mechanics

1758 - Linnaeus developed taxonomy of species, proposed binomial nomenclature

1764 - Hargreaves invented the spinning jenny

1769 - Watt invented the modern steam engine

1777 - Lavoisier proposed idea of chemical compounds made of elements

1781 - Herschel discovered Uranus

1783 - Michel and Montgolfier invented the hot air balloon; the first people to fly, altitude 1800 m

1785 - Coulomb confirmed the inverse square law for electric force

1785 - Hutton proposed the idea of uniformitatianism in the geological history of the earth

1785 - Cartwright invented the power loom for producing cloth

1787 - Berthollet proposed system of chemical nomenclature

1792 - Rousseau wrote "Social Contract"

1793 - Whitney invented the cotton gin

1796 - Jenner discovered smallpox vaccination

1799 - Discovery of the Rosetta Stone

1800 - Volta invented the battery

1800 - Ampere discovered properties of magnetic field produced by electric current

1803 - Dalton composed the law of definite proportions in chemistry

1804 - Rockets developed by the British Army Corp reached height of 1830 m

1807 - Fulton invented the steamboat

1808 - Dalton published a periodic table based on atomic weights

1811 - Avogadro introduced the concept of the mole

1814 - Stephenson invented the locomotive engine

1820 - Oersted discovered that an electric current causes the deflection of compass needle

1822 - Champollion translated the Rosetta Stone

1825 - discovery of Ampere's Force Law

1827 - Brown discovered Brownian motion

1830 - The first railroad (between Liverpool and Manchester, England)

1831 - Faraday (England) and Henry (U.S.) independently discovered that a current is produced in a wire when it is moved near a magnet

1833 - Charles Lyell published "Principles of Geology", based on uniformitarianism

1839 - Goodyear invented vulcanized rubber

1844 - Morse sent the first telegraph message

1846 - Galle discovered Neptune, accounting for observed perturbations in the motion of Uranus

1849 - Fizeau measured the velocity of light

1853 - Bessemer in Britain and Kelly in U.S. invented the Bessemer steel process

1854 - Boole invented Boolean algebra

1856 - Neanderthal fossil found in Germany

1859 - Darwin published "On The Origin of Species"

1866 - Mendel wrote a paper on his findings about heredity in plants

1868 - Cro-Magnon fossil found in France

1869 - Mendeleyev used a periodic table of known elements to correctly predict the properties then undiscovered elements

1873 - Maxwell published "Treatise on Electricity and Magnetism"

1874 - Cantor established principles of mathematical set theory

1877 - Edison invented the phonograph

1877 - Hall discovered the two moons of Mars

1879 - Wundt established the first laboratory for psychology experiments

1879 - Edison invented the electric light bulb

1882 - Lindemann proved that pi is transcendental

1882 - Edison created the first large power station in NYC

1883 - Wroblewski and Olszewski first produced liquid oxygen.

1885 - Benz invented the gasoline-powered automobile

1885 - Eastman invented the box camera

1885 - Hertz discovered the photoelectric effect

1885 - Balmer discovered spectral lines of hydrogen

1887 - Mendelson and Morley conduct experiment showing no evidence for the existence of an "ether"

1888 - Hertz discovered radio waves, verifying Maxwell's prediction of electromagnetic waves

1888 - Edison invented the kinetoscope

1889 - Hollerith invented the first calculating machine, used punch cards

1891 - "Java Man" discovered in Indonesia

1892 - Dewar discovered that a double-walled bottle with a vacuum layer insulates the contents from heat flow

1895 - Roentgen discovered x-rays

1895 - Marconi invented antenna and wireless telegraph (short distance)

1896 - Becquerel discovered radioactivity

1896 - Marconi increased range of wireless telegraph to 1.6 km

1897 - Marconi increased range of wireless telegraph to 29 km; first ship-to-shore message

1898 - Curie and Curie announced their discovery of radium and polonium

1899 - Marconi established wireless telegraph service between England and France

1900 - First public awareness of Mendel's findings in genetics, when his 1865-1866 papers were found

1900 - Freud published "The Interpretation of Dreams"

1900 - Finlay discovered that yellow fever is spread by mosquitos

1900 - Planck proposed that energy can only be absorbed or emitted by matter in discrete amounts (quanta)

1901 - First transatlantic wireless telegraph

1902 - Discovery of Tyrannosaurus Rex

1902 - Kennelly (U.S.) and Heaviside (England) independently discovered the ionosphere

1903 - The botanist De Vries discovered mutations in plants

1903 - Wright brothers' airplane remained in flight for 12 seconds

1904 - Fleming invented vacuum tube diode

1904 - Genetics experiments by Thomas Morgan, discovery of sex-linked mutations (among a group of fruit flies with normal red or unusual white eyes, all of the white-eyed offspring were male).

1905 - Einstein published papers on Brownian motion, the photoelectric effect, and the special theory of relativity

1906 - De Forest invented the triode vacuum tube

1906 - Thomson discovered the electron

1908 - the "Tunguska event" - major damage to a forest region in Siberia caused by a comet or meteorite

1908 - Ford produced the Model T automobile

1908 - Wegener proposed theory of continental drift

1909 - The "Piltdown Man" hoax -- a fake archeological discovery announced by dishonest scientists who wanted to "prove" that human beings had evolved in Europe

1911 - Rutherford discovered that the positive charge in an atom is concentrated in a small nucleus; proposed a planetary model of the atom

1912 - Pickard invented the crystal diode and crystal detector

1913 - Edison invented motion pictures with sound

1913 - Ford added the assembly line to his automobile plant

1913 - Bohr published his model of the atom, based on energy states described by one quantum number

1916 - Lewis proposed the idea of covalent bonds

1916 - Einstein published the general theory of relativity

1917 - Germany - the first major military use of airplanes to drop bombs on cities

1919 - Eddington recorded data on the sun's gravitational deflection of starlight during a solar eclipse, confirming Einstein's general theory of relativity

1923 - Freud published "The Ego and the Id"

1923 - Development of the diptheria vaccine

1923 - Production of insulin to treat diabetes

1923 - Hubble estimated the distance from the Milky Way Galaxy to the Andromeda Galaxy

1924 - Discovery of Australopithecus Africanus, its human-sized brain too large to be that of an ape, but having the canine teeth of a gorilla

1924 - De Broglie proposed that all matter has wave properties

1925 - Pauli proposed the Exclusion Principle (no two electrons in an atom can have the same set of quantum numbers)

1925 - Scopes fired from biology teaching position for teaching evolution

1926 - Schrodinger developed the wave equation

1926 - Born proposed the statistical interpretation of the wave equation

1926 - Goddard launched the first liquid-fueled rocket

1927 - Heisenberg proposed the Uncertainty Principle (we cannot simultaneously determine the position and momentum of a subatomic particle)

1927 - Experiment by Davisson and Germer, and simultaneous experiment by G. P. Thompson, proved the wave behavior of electrons

1927 - the first television transmission (England)

1928 - Dirac developed the relativistic quantum theory

1927 - Big bang theory introduced

1929 - Hubble discovered that the galaxies are moving away from each other, causing an expansion of the universe

1930 - Tombaugh discovered Pluto

1931 - Lawrence invented the cyclotron

1931 - Anderson discovered the positron

1932 - Chadwick discovered the neutron

1936 - the first regular television broadcast (England)

1937 - Discovery of the muon

1938 - Hahn, Strassmann, Meitner and Frisch discovered nuclear fission

1938 - Bethe hypothesized that nuclear fusion is the source of energy in stars

1939 - The first regular TV broadcast in the U.S.

1939 - Discovery of Kirlian photography -- electrical "auras" surrounding living specimens

1942 - Fermi produced the first nuclear chain reaction in an experiment

1942 - Establishment of the Manhattan Project to develop an atomic bomb

1945 - The first atomic bomb was detonated at Hiroshima, Japan -- about 70,000 people were killed instantly; about 30,000 more people died within several weeks

1946 - Gamow proposed the Big Bang hypothesis.

1946 - The University of Pennsylvania developed the ENIAC computer, containing 18,000 vacuum tubes

1947 - W. F. Libby invented radiocarbon dating

1947 - Researchers at Bell Labs invented the transistor

1947 - Discovery of the pion (predicted by Yukawa in 1935)

1948 - Kinsey published "Sexual Behavior in the Human Male"

1951 - Franklin discovered nucleic acids (RNA and DNA), helical shape

1952 - The first sex-change surgery, transforming George Jorgensen into Christine Jorgensen

1953 - Kinsey published "Sexual Behavior in the Human Female"

1953 - Watson and Crick discovered DNA has double helix, composed of ATCG bases occuring in pairs (A with T, and C with G)

1953 - Miller produced amino acids from inorganic compounds and sparks

1953 - Radioactive fluorine dating proved that the "Piltdown Man" artifact was a hoax

1956 - Discovery of the neutrino (predicted by Pauli in 1930)

1957 - The first artificial satellite, Sputnik, put into earth orbit

1958 - U.S. Congress established NASA

1959 - First unmanned spacecraft hit the moon (Soviet Union)

1960 - Maiman invented the ruby laser

1960 - Javan invented the helium-neon laser

1960 - Goodall studied chimpanzees in Tanzania

1960 - Development and approval of the birth control pill

1961 - A person orbited the earth for the first time (Yuri Gagarin)

1963 - Vine and Matthews discovered that rock layers with particular magnetic orientations, indicating reversals of the earth's magnetic field, are symmetrical about the mid-oceanic ridge, indicating that new crust is created at the ridge.

1963 - Gell-Mann proposed protons and neutrons are made of smaller particles (quarks)

1964 - Discovery of a quasar

1964 - Unmanned U.S. spacecraft transmitted television pictures of the moon before hitting the surface

1964 - Wilson and Penzias discovered the background microwave radiation of the universe

1965 - The first "space walk" (Soviet Union)

1966 - The first unmanned soft landing on the moon (Soviet Union)

1967 - Salam and Weinberg developed a model to unite electromagnetism and the weak nuclear force.

1967 - Bell and Hewish discover pulsars

1967 - U.S. astronauts Grissom, White and Chaffee killed during ground test; Apollo program delayed

1968 - Human beings orbited the moon for the first time (Apollo 8)

1969 - People walked on the moon for the first time (Apollo 11)

1969 - Meteorite in Australia found to contain amino acids

1970 - Apollo 13 moon landing canceled due to severe malfunctions

1971 - First unmanned spacecraft hit Mars (Soviet Union)

1971 - Apollo 15 used the lunar rover

1971 - First space station, Salyut 1, and first space docking (Soviet Union)

1972 - Discovery of a 2 million year old humanlike fossil, Homo habilis, in Africa

1973 - U.S. launched Skylab space station

1974 - Discovery of "Lucy" in Africa, an almost complete homonid skelton over 3 million years old, only 3 and a half feet tall but having adult teeth, a small brain, walked upright

1975 - First unmanned soft landing on Venus (Soviet Union)

1975 - The first U.S.-Soviet space docking (Apollo and Soyuz)

1975 - Invention of the CAT scanner (computerized axial tomography)

1976 - Cosmic string theory was introduced

1977 - Voyager spacecraft launched; contained recording of earth sounds, including music and greetings in 55 Earth languages

1977 - Submarine "Alvin" explored midoceanic ridge, discovered chemosynthetic life

1979 - First "test tube baby" from artificial insemination

1979 - Voyager 1 and 2 photographed Jupiter

1980 - Voyager 2 photographed Saturn

1980 - Introduction of the communication protocol that led to the Internet

1981 - Binnig and Rohrer invented the scanning tunneling microscope

1981 - U.S. launched the first space shuttle, Columbia

1982 - First launch of communications satellites into orbit by space shuttle

1984 - First retrieval of malfunctioning satellites, repair and relaunch by space shuttle

1984 - Discovery of ozone hole over Antarctica

1986 - Voyager 2 photographed Uranus; discovered moons

1986 - Development of the first high temperature superconductors

1986 - Soviet Union launched Mir space station

1986 - U.S. space shuttle Challenger exploded on launch, killing 7 astronauts

1989 - Voyager 2 photographed Neptune; discovered moons

1989 - An asteroid came relatively close to colliding with the earth

1990 - Hubble Space Telescope launched; optical defect discovered

1991 - Discovery of the buried crater near the Yucatan Peninsula, dated at 65 million years old

1992 - Pope John Paul II acknowledged the Vatican's error in the condemnation of Galileo

1993 - Wiles proved Fermat's Last Theorem, which had been first proposed in 1637

1993 - Hubble Space Telescope repaired

1994 - Hubble Space Telescope confirmed existence of a black hole

1994 - Astronomers observed comet Shoemaker-Levy 9 (S-L 9) colliding with Jupiter

1995 - the second U.S./Russian space docking (Atlantis and Mir)

1995 - Discovery of the top quark at Fermilab

1996 - Pope John Paul II affirmed evolution by natural selection

1997 - Microscopic analysis of meteorite led to belief in ancient life on Mars

1997 - Pathfinder vehicle studied and photographed Mars