Astronomy and Space Timeline

galileo and telescope
Galileo offering his telescope to three young women seated on a throne. Painting by unknown artist. Library of Congress.

Humanity Begins to Wonder about the Sky

As civilizations formed and spread across the continents, their interest in the sky (and what it meant) grew as observers kept records of what they saw. Not every "record" was in writing; some monuments and buildings were created with an eye toward a link with the sky. People were moving from a simple "awe" of the sky to an understanding of the motions of celestial objects, a connection between the sky and the seasons, and ways to "use" the sky to create calendars.


Nearly every culture had a connection to the sky, often as a calendrical tool. Nearly all also saw their gods, goddesses, and other heroes and heroines reflected in the constellations, or in the motions of the
Sun, Moon, and stars. Many tales invented during the ancient epochs are still told today. 

  • 2680 BC: The Great Pyramid at Giza completed. It is thought that the pyramids may reflect the three stars in Orion's Belt.
  • 2300BC: Chinese astronomers start to observe the sky and create charts of the constellations
  • 2296BC: A comet is observed for the first time by the Chinesen and noted as a possible omen.
  • 1860 BC: The construction of Stonehenge in what is now England. Researchers think there is some connection to the sky and the standing stones.
  • 1800BC: Babylonians begin to keep observational records.
  • 1600BC: Chaldean astronomers identify the zodiac, the zone of constellations against which the Sun, Moon, and planets appear to move.
  • 763BC: Solar eclipse observed and recorded .by Babylonians.
  • 624BC: Thales of Miletus was born.
  • 585BC: Thales of Miletus predicted a solar eclipse.
  • 547BC: Thales of Miletus died.
  • 500BC: Pythagoras suggests that the Earth is a sphere and not flat, as had been previously assumed
  • 440 BC: Greek philosopher Leucippus, his student Democritus present the concept that all matter consists of fundamental particles called atoms. ("Atom" comes from the Greek word meaning "indivisible.")
  • 365BC: Chinese apparently first spot the moons of Jupiter with the naked eye.
  • 350 BC: Aristotle writes Meteorologica, the first book on weather.
  • 300 BC: Euclid, a Greek from Alexandria, writes Elements, introducing geometry (which means "land measurement").
  • 270BC: Aristarchus says that the Sun is at the center of the solar system; this is generally dismissed as folly. 
  • 240BC: An object later known as Comet Halley is observed by the Chinese.
  • 212 BC: Archimedes calculates the area of circle, defines the principles of the lever, the screw, and buoyancy.
  • 194 BC: Eratosthenes calculates the size of Earth.
  • 120 BC: Hipparchus of Rhodes (161 BC-122 BC) Defines the cosmos by latitude and longitude; and makes triangular measurement of celestial navigation.
  • 127: Alexandrian astronomer and mathematician Ptolemy (Claudius Ptolemaeus) publishes Almagest, in which he cataloged 1,022 stars - the previous known number of stars being 850. This was the primary astronomy text for 14 centuries.
  • 1473: Nicolaus Copernicus born in Poland.
  • 1514: Astronomer Nicolas Copernicus suggests that Earth moves around the Sun.
  • 1543: Copernicus publishes De Revolutionibus Orbium Caoelestium (The Revolutions of the Heavenly Spheres), the theory that Earth revolves around the Sun, while on his deathbed.
  • 1546: Tycho Brahe born in Denmark.
  • 1552: Books on geography and astronomy are burned in England because people thought they contained magic.
  • 1564: Galileo Galilei born in Italy.
  • 1572: Tycho Brahe observes a supernova in the constellation Cassiopeia.
  • 1583: Galileo Galilei demonstrates that successive beats of a pendulum always take place in the same length of time, regardless of the distance through which it swings.
  • 1590: Microscope invented by Dutch spectacle maker Zacharias Janssen. Galileo Galileiexperiments with falling objects.
  • 1593: Galileo Galilei invents a water thermometer.
  • 1596: Johannes Kepler publishes Mysterium cosmographicum.
  • 1598: Tycho Brahe describes his experiments in astronomy.
  • 1608: Hans Lippershey is thought to have invented the telescope
  • 1609: Galileo Galilei adopts the telescope for sky viewing and makes improvements to its design. 

    Edited and updated by Carolyn Collins Petersen.