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Astronomy, 1543-1992

  • Apr 18, 1543

    Heliocentric Theory

    Copernicus publishes his heliocentric theory of the Universe.
  • First Telescope

    Galileo uses telescope for astronomical purposes. He discovers 4 Jovian moons, the Moon's craters and the Milky Way galaxy.
  • Laws of Planetary Motion

    Kepler's First and Second Laws of Planetary Motions are announced.
  • Planetary Motion Laws

    the Third Law of Planetary Motion is announced by Kepler in his work Harmonice Mundi (Harmony of the World).
  • Rings of Saturn

    Christian Huygens discovers Saturn's rings and Titan, the fourth satellite of Saturn.
  • Reflecting Telescope

    The first reflecting telescope was built by Newton.
  • First Variable Star

    Geminiano Montanari discovers the star Algol is not steady in brightness, thus recognizing the first variable star.
  • Speed of Light

    While in Paris, Danish astronomer Ole Romer measures the speed of light.
  • The Cassini Division

    Cassini discovers that Saturn's rings are split into two parts, so that today the gap is called the "Cassini Division".
  • Universal Gravitation

    Newton publishes his theory of universal gravitation in the work Philosophiae Naturalis Principia Mathematica. This is seen to be the start of Modern Astronomy.
  • Halley's Comet Prediction

    Halley correctly predicts the return of a comet (Halley's comet) in 1758.
  • Return of Halley's Comet Observed

    Johann Palitzsch observes Halley's comet as predicted by Halley in 1705.
  • Uranus

    The discovery of Uranus by Herschel
  • Rocket pioneer Konstantin Tsiolkovskii is born

    Tsiolkovskii's work in early rocketry earned him the title of "Father of Astronautics". Many of his proposals concerning rocketry were later put into use including: use of liquid hydrogen and liquid oxygen as rocket fuel and multi-stage rocket design for achieving Earth orbit or interplanetary flight.
  • The Great Red Spot

    The Great Red Spot on Jupiter becomes prominent.
  • Rocketry

    Robert Goddard begins practical rocketry.
  • We're Not Alone

    Hubble shows that galaxies exist outside the Milky Way galaxy.
  • Sputnik

    Sputnik, first object to orbit the Earth, launched by the Russians.
  • Explorer 1

    Explorer 1 launched. This was the first U.S. satellite to orbit the Earth.
  • John Glenn

    John Glenn becomes first American man to orbit Earth.
  • Hubble Space Telescope

    Hubble Space Telescope put into orbit from space shuttle Discovery.
  • Pope John Paul II

    The Vatican under Pope John Paul II announces that the Catholic Church erred in condmening Galileo's work that proved that the work of Copernicus was valid, mainly that the planets circle the Sun and not the Earth.