Time: 400
Noteworthy Events: Middle or Dark Ages begin; science dormant in the West.
Time: 455
Noteworthy Events: Vandals sack Rome.
Time: 963
Noteworthy Events: Al Sufi, in his Book of the Fixed Stars, mentions nebulae.
Time: 1001
Noteworthy Events: Leif Ericsson reaches New England.
Time: 1276–1292
Noteworthy Events: Marco Polo in Hangchow.
Time: 1400
Noteworthy Events: Renaissance of learning commences in Europe.
Time: 1492
Noteworthy Events: Columbus (re)discovers America.
Time: 1521
Noteworthy Events: Cortez takes Mexico.
Time: 1522
Noteworthy Events: Survivors of Magellan’s final expedition complete circumnavigation of the globe.
Time: 1523
Noteworthy Events: Pizarro takes Peru.
Time: 1543
Noteworthy Events: Copernicus’s On the Revolutions published.
Time: 1572
Noteworthy Events: Tycho sees a nova (or “new star”) in the sky, evidence against Aristotle’s theory that the realm of the stars is unchanging and therefore unlike that of the earth.
Time: 1576
Noteworthy Events: Thomas Digges in England publishes a defense of the Copernican cosmology in which he portrays the stars as distributed throughout infinite space.
Time: 1604
Noteworthy Events: Galileo proposes that bodies fall with a uniformly accelerated motion, thus enunciating the first of the laws of classical dynamics.
Noteworthy Events: Kepler and Galileo observe a supernova.
Time: 1609
Noteworthy Events: Galileo first observes the night sky through a telescope.
Noteworthy Events: Kepler demonstrates that the orbits of the planets are elliptical.
Time: 1611
Noteworthy Events: Edition of the King James Bible published containing an estimate by James Ussher, bishop of Armagh, that “the beginning of time … fell on the beginning of the night which preceded the 23 rd day of October, in the year … 4004 B.C.”
Time: 1616
Noteworthy Events: Roman Catholic Church bans all books that maintain that the earth moves.
Time: 1639
Noteworthy Events: Transit of Venus observed by two English amateur astronomers.
Time: 1662
Noteworthy Events: Royal Society chartered in London.
Time: 1665–1666
Noteworthy Events: Isaac Newton, age twenty-three, home from college, realizes that gravitational force obeying an inverse-square law would account alike for falling bodies on earth and the motion of the moon in its orbit.
Time: 1666
Noteworthy Events: Newton observes spectrum produced by sunlight when shown through a prism.
Time: 1672
Noteworthy Events: Opposition of Mars widely observed, by Richer at Cayenne and Cassini in Paris among others, leading to estimates of the distance from the earth to the sun of some eighty-one to eighty-seven million miles—90 percent of the correct value.
Time: 1675
Noteworthy Events: Olaus Römer determines, from studying the satellites of Jupiter, that light has a finite velocity.
Time: 1684
Noteworthy Events: Edmond Halley visits Isaac Newton at Trinity College, resurrects line of research that leads Newton to write the Principia.
Time: 1686
Noteworthy Events: Bernard de Fontenelle’s Entretiens sur la Plurality des Mondes popularizes the idea that the universe contains many inhabited worlds.
Time: 1687
Noteworthy Events: Newton’s Principia published.
Time: 1716
Noteworthy Events: Halley urges that future transit of Venus may be observed and timed in order to triangulate interplanetary distances.
Time: 1718
Noteworthy Events: Halley finds that the bright stars Sirius, Aldebaran, Betelgeuse, and Arcturus have changed their position in the sky since Ptolemy’s Almagest was compiled—first evidence of the “proper motion” of stars.
Time: 1719
Noteworthy Events: John Strachey in England publishes notes on strata in the coal-rich district of Somerset, an early step in the establishment of geological science.
Time: 1728
Noteworthy Events: James Bradley finds aberration in starlight produced by the motion of the earth.
Time: 1750–1784
Noteworthy Events: French amateur astronomer Charles Messier catalogs scores of indistinct celestial objects that might be mistaken for comets; many will prove to be star clusters and interstellar gas clouds, others external galaxies.
Time: 1755
Noteworthy Events: Kant proposes that spiral nebulae are galaxies of stars.
Time: 1761, 1769
Noteworthy Events: Transits of Venus observed by widely scattered scientific expeditions, permitting new determinations of the distance from the earth to the sun—the “astronomical unit.”
Time: 1765
Noteworthy Events: John Harrison is acknowledged by the English Board of Longitude to have developed the marine chronometer, making possible accurate timekeeping and the determination of longitude at sea.
Time: 1766
Noteworthy Events: Henry Cavendish identifies hydrogen, the most abundant element in the universe.
Time: 1781
Noteworthy Events: William Herschel discovers the planet Uranus.
Time: 1783
Noteworthy Events: Herschel derives the general direction of the solar system’s motion through space, by studying the proper motion of thirteen bright stars.
Time: 1793
Noteworthy Events: William Smith, a canal surveyor and consulting engineer excavating the Somersetshire Coal Canal, finds evidence for a consistent sequence of geological strata throughout England.
Time: 1795
Noteworthy Events: James Hutton’s Theory of the Earth advances a uniformitarian hypothesis of geological change having taken place in the course of a lengthy past.
Time: 1800
Noteworthy Events: William Herschel detects infrared light.
Time: 1801
Noteworthy Events: Johann Ritter detects ultraviolet light.
Noteworthy Events: Georges Cuvier identifies twenty-three species of extinct animals in the fossil record, confounding the doctrine that all species were created simultaneously and are imperishable.
Time: 1802
Noteworthy Events: William Wollaston discovers spectral lines in the spectrum of the sun.
Time: 1814
Noteworthy Events: Joseph Fraunhofer, using the first grating spectroscope, rediscovers solar spectral lines and charts them, laying the basis for astrophysical spectroscopy.
Time: 1820
Noteworthy Events: Hans Christian Örsted discovers that electric current produces a magnetic field, ushering in the study of electromagnetic force.
Time: 1823
Noteworthy Events: John Herschel proposes that Fraunhofer lines may indicate the presence of metals in the sun.
Time: 1830
Noteworthy Events: Charles Lyell publishes the first volume of his Principles of Geology, presenting evidence for the uniformitarian theory that the geological record can be explained in terms of the slow action, over aeons of time, of processes that continue in the world today.
Time: 1831
Noteworthy Events: Charles Darwin, a copy of Lyell’s book in hand, departs aboard the Beagle on a five-year voyage around the world.
Time: 1832
Noteworthy Events: Darwin adduces the essential elements of his theory of evolution by natural selection, but does not publish the theory for another twenty-two years.
Time: 1833
Noteworthy Events: First precise measurement, by means of parallax, of the distance to a star.
Time: 1842
Noteworthy
Events: Christian Johann Doppler points out that the wavelength of sound or other emissions from a moving source will appear to a stationary observer to be higher in frequency if the object is approaching, lower if it is receding—the “Doppler shift.”
Time: 1847
Noteworthy Events: Hermann von Helmholtz proposes the law of conservation of energy.
Time: 1849
Noteworthy Events: Jean-Léon Foucault detects spectral emission lines.
Time: 1850
Noteworthy Events: First astronomical photograph—a daguerreotype of the moon—is made, by W. C. Bond at Harvard.
Time: 1855–1863
Noteworthy Events: Robert Bunsen and Gustav Kirchhoff workout the basics of spectral analysis, by which the spectra of laboratory materials can be compared with those of the sun and stars.
Time: 1859
Noteworthy Events: Darwin’s Origin of Species published.
Time: 1862
Noteworthy Events: Foucault refines estimates of the velocity of light.
Time: 1864
Noteworthy Events: William Huggins obtains the first spectrum of a nebula, finds that it is composed of gas.
Noteworthy Events: James Clerk Maxwell publishes a unified theory of electricity and magnetism, portraying both as aspects of electromagnetic force.
Time: 1865
Noteworthy Events: Gregor Mendel announces results of his research in genetics, revealing key to persistence of unchanging traits in living things, a critical missing element in Darwinism.
Time: 1874, 1882
Noteworthy Events: Transits of Venus observed with new, more precise instruments, improving estimates of the astronomical unit.
Time: 1877
Noteworthy Events: David Gill measures parallax of Mars during its opposition, deduces distance to the sun of ninety-three million miles.
Time: 1879
Noteworthy Events: Albert Michelson, employing Foucault’s principle, determines velocity of light.
Time: 1883
Noteworthy Events: Henry Rowland’s diffraction grating greatly improves the resolution of spectrographs.
Time: 1884
Noteworthy Events: Johann Balmer determines harmonic sequence of hydrogen lines, initiating line of inquiry that will lead to investigation of the electron shells of atoms.
Time: 1887
Noteworthy Events: Albert Michelson and Edward Morley perform the final and most precise in a series of experiments showing that space cannot be filled with the aether that had been thought to be responsible for transmitting light. Their work clears the ground for the ascent of the Lorentz contractions.
Time: 1892
Noteworthy Events: Hendrik Lorentz and George FitzGerald independently propose that contraction of length of measuring rods with velocity explains the Michelson-Morley experimental results, a concept essential to the special theory of relativity.
Time: 1895
Noteworthy Events: E. E. Barnard photographs the Milky Way, notes that dark patches are too numerous to be empty space but must represent dark clouds of interstellar matter.
Time: 1897
Noteworthy Events: J. J. Thomson discovers the electron.
Time: 1898
Noteworthy Events: Marie and Pierre Curie isolate the radioactive elements radium and polonium.
Time: 1900
Noteworthy Events: Max Planck proposes the quantum theory of radiation, the basis of quantum physics.
Time: 1904
Noteworthy Events: Ernest Rutherford suggests that the amount of helium produced by the radioactive decay of minerals in rocks could be employed to measure the age of the earth.
Time: 1905
Noteworthy Events: Albert Einstein publishes special theory of relativity, indicating that measurements of space and time are distorted at high velocity and implying that mass and energy are equivalent; in another paper he shows that light is composed of quanta.
Noteworthy Events: Jacobus Kapteyn, studying the proper motions of twenty-four hundred stars, finds evidence of what he calls “star streaming”—that stars in our neighborhood move in a preferred direction—an early clue to the rotation of our galaxy.
Time: 1911
Noteworthy Events: Ernest Rutherford determines that most of the mass of atoms is contained in their tiny nuclei.
Time: 1912
Noteworthy Events: Henrietta Swan Leavitt discovers a correlation between the absolute magnitude and the period of variability of Cepheid variable stars, opening the door to their use as intergalactic distance indicators.
Time: 1913
Noteworthy Events: Niels Bohr develops theory of atomic structure, in which electrons are said to orbit the nucleus in a manner somewhat akin to that of planets orbiting the sun.
Noteworthy Events: Henry Norris Russell presents a plot of the luminosities and colors of stars, extending work done in 1911 by Ejnar Hertzsprung. The resulting Hertzsprung-Russell diagram will be fundamental to the understanding of the evolution of stars.
Time: 1914
Noteworthy Events: Walter Adams and Arnold Kohlschutter determine the absolute luminosity of stars from their spectra alone, making it possible to estimate the distances of millions of distant stars.
Time: 1915
Noteworthy Events: Annie Jump Cannon classifies stars into categories according to their spectral type, a major step in discerning order underlying the diversity of the stars.
Time: Arnold Sommerfeld refines Bohr model of the atom.
Time: 1916
Noteworthy Events: Albert Einstein publishes the general theory of relativity, portraying gravitation as an effect of curved space and delivering cosmology from the ancient dilemma of a finite versus an infinite universe.
Time: 1916–1917
Noteworthy Events: Arthur Stanley Eddington demonstrates theoretically that stars are gaseous spheres; his work lays the foundation for his later assertion that gravitational contraction cannot be the mechanism that powers the stars.
Time: 1917
Noteworthy Events: Heber Curtis and George Ritchey announce that they have found novae (stars that have suddenly increased tremendously in brightness) in the Andromeda spiral. Opinions differ on whether this means Andromeda is a galaxy of stars, or a gaseous nebula from which new stars are condensing.
Noteworthy Events: Vesto Slipher measures large Doppler shifts in the spectra of spirals, later found to be due to the motion of the spiral galaxies in the expanding universe.
Time: 1918
Noteworthy Events: Harlow Shapley determines, by studying the distances of globular clusters, that the sun lies toward one edge of a galaxy of stars.
Noteworthy Events: The 100-inch telescope at Mount Wilson, then the world’s largest, begins operation.
Time: 1919
Noteworthy Events: English expedition to observe a solar eclipse confirms Einstein’s prediction that space, in a gravitational field, is strongly curved.
Time: 1920
Noteworthy Events: The controversy over whether spiral nebulae are gaseous clouds or “island universes”—i.e., galaxies—comes to a head in a debate between Heber Curtis and Harlow Shapley.
Time: 1922
Noteworthy Events: Ernst Öpik deduces, from rotation velocities and the mass to luminosity ratio of the Andromeda spiral, that it is a galaxy in its own right.
Noteworthy Events: Aleksandr Friedmann shows that general relativity is consistent with an expanding-universe cosmology.
Time: 1923
Noteworthy Events: Cecilia Payne demonstrates, from solar spectra, that the relative abundance of elements in the sun approximates that in the crust of the earth.
Time: 1924
Noteworthy Events: Louis de Broglie develops wave theory of matter.
Time: 1925
Noteworthy Events: Max Born, Pascual Jordan, and Werner Heisenberg develop quantum mechanics.
Noteworthy Events: Wolfgang Pauli announces the exclusion principle, essential to under
standing spectral lines of stars and nebulae.
Noteworthy Events: Bertil Lindblad demonstrates that the motion of stars called “star streaming” by Kapteyn in 1905 can be explained as being due to the rotation of the Milky Way galaxy.
Noteworthy Events: Edwin Hubble announces that he has identified Cepheid variable stars in the Andromeda galaxy, confirming that it is a galaxy of stars rather than a gaseous nebula and making it possible to measure its distance.
Time: 1926
Noteworthy Events: Erwin Schrödinger proposes wave-mechanical theory of the atom.
Noteworthy Events: Lindblad produces theory of rotation of the Milky Way galaxy.
Time: 1927
Noteworthy Events: Jan Oort detects evidence of the rotation of the Milky Way galaxy, by examining the radial velocities of stars.
Noteworthy Events: Georges Lemaître publishes an expanding-universe cosmology.
Noteworthy Events: Werner Heisenberg discovers the quantum indeterminacy principle.
Time: 1927–1929
Noteworthy Events: Relativistic quantum electrodynamics theory developed.
Time: 1928
Noteworthy Events: George Gamow applies the uncertainty principle to the problem of how protons combine to build nuclei in stellar interiors, a signal step in establishing that nuclear fusion provides the energy that powers stars.
Noteworthy Events: Ira Bowen determines that the spectra of nebulae are produced by doubly ionized oxygen and not by an unknown element called “nebulium,” as had been thought. This strengthens the hopes of astrophysicists that the rest of the universe is made of the same elements and obeys the same natural laws as here on Earth.
Noteworthy Events: Dirac publishes the “Dirac equation,” a relativistic quantum theory of electromagnetism.
Time: 1929
Coming of Age in the Milky Way Page 46
