Some History

This timeline illustrates the changing rates of progress in our understanding of gravity and planetary motion.

(Click on the timeline to expand it.)

The annotations are roughly separated into "experimental" (above the line) and "theoretical" (below it). Newton is exceptional for appearing on both sides. The long "dry spell" between Ptolemy and Copernicus is noteworthy: Aristotle's emphasis on the circle as a "perfect" geometric figure seems to have blinded thinkers for a sizable part of recorded history.

(View Cosmos DVD 2, episode 3, Kepler's life.)
Some particularly interesting dates:
Here, and throughout the text, you can click on any of the images to see a larger version.
October 22, 2136 B.C. - first record of a solar eclipse.source
July 4, 1054 - The Crab Nebula Supernova occurred.source
January 7, 13, 1610 - Galileo discovers Callisto.source
January 7, 13, 1610 - Galileo discovers Europa.source
January 7, 13, 1610 - Galileo discovers Io.source
January 7, 13, 1610 - Galileo discovers Ganymede.source
March 25, 1655 - Christiaan Huygens discovers Titan.source
March 13, 1781 - William Herschel discovers Uranus.source
September 23, 1846 - G. J. Galle discovers Neptune.source
October 10, 1846 - William Lassell discovers Triton.source
August 18, 1868 - Norman Lockyer discovers Helium in the Sun.source
August 11, 1877 - Asaph Hall discovers Deimos.source
August 17, 1877 - Asaph Hall discovers Phobos.source
June 30, 1908 - The Tunguska Event occurred.source
May 29, 1919 - General Relativity is tested during solar eclipse.source
February 18, 1930 - Clyde Tombaugh discovers Pluto.source
February 16, 1948 - Gerard Kuiper discovers Miranda.source
October 4, 1957 - Sputnik 1 orbits Earth.source
January 2, 1959 - Luna 1 arrives at the Moon.source
December 14, 1962 - Mariner 2 arrives at Venus.source
July 14, 1965 - Mariner 4 arrives at Mars.source
January 31, 1966 - Luna 9 lands on the Moon.source
October 18, 1967 - Venera 4 enters Venus' atmosphere.source
February 24, 1968 - Jocelyn Bell discovers pulsar in the Crab Nebula.source
July 20, 1969 - Apollo 11 lands on the Moon.source
December 15, 1970 - Venera 7 lands on Venus.source
February 15, 1973 - Pioneer 10 passes through the asteroid belt.source
December 3, 1973 - Pioneer 10 arrives at Jupiter.source
March 29, 1974 - Mariner 10 arrives at Mercury.source
July 20, 1976 - Viking 1 lands on Mars.source
March 10, 1977 - Uranus' rings discovered.source
March 4, 1979 - Jupiter's ring discovered by Voyager 1.source
September 1, 1979 - Pioneer 11 arrives at Saturn.source
June 13, 1983 - Pioneer 10 becomes first spacecraft to leave the Solar System.source
September 11, 1985 - International Cometary Explorer arrives at Giacobini-Zinner.source
January 24, 1986 - Voyager 2 arrives at Uranus.source
August 25, 1989 - Voyager 2 arrives at Neptune.source
December 7, 1995 - Galileo enters Jupiter's atmosphere.source
February 22, 2000 - Stardust collects coma material from P/Wild 2.source
February 12, 2001 - NEAR lands on Eros.source
December 3, 2001 - Genesis collects solar wind particles.source
January 14, 2005 - Huygens probe lands on Titan.source
July 15, 2015 - New Horizons probe arrives at Plutosource

These dates represent first successes; for a more complete picture of the history of space exploration, see NASA's Chronology of Lunar and Planetary Exploration.



©2010, Kenneth R. Koehler. All Rights Reserved. This document may be freely reproduced provided that this copyright notice is included.

Please send comments or suggestions to the author.