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big bang theory
The Big Bang theory is an effort to explain what happened at the very beginning of our universe. Discoveries in astronomy and physics have shown beyond a reasonable doubt that our universe did in fact have a beginning. Prior to that moment there was nothing; during and after that moment there was something: our universe. The big bang theory is an effort to explain what happened during and after that moment. -
1990
Hubble Space telescope launched. -
c140
Ptolemy "perfects" geocentric model of solar system. In Ptolemy's model the planets moved on circles (epicycles) that moved on other circles (deferents). The model could accurately predict the positions of the planets. Ptolemy also compiled a catalog of stellar brightnesses based partly on the earlier catalog of Hipparchus. -
1610
Galileo discovers four largest satellites of Jupiter. Galileo found that Jupiter is orbited by four large satellites, now called, collectively, the Galilean satellites. This proved that at least some celestial bodies didn't orbit the Earth. -
1686
Newton publishes "Principia". Newton's monumental work described his discoveries about gravity, motion and the orbits of the planets. -
1916
Albert Einstein's general theory of relativity. Einstein explained that matter curves space, causing bodies to move in ways we attribute to gravity. -
1972
Last Apollo mission to Moon. Apollo 17 concluded the series of lunar landings in which a dozen astronauts explored the Moon -
1995
Galileo probe enters Jupiter's atmosphere. An entry probe detached from the Galileo spacecraft and parachuted into Jupiter's atmosphere. The probe sent back data for about an hour before it was destroyed by high pressure and temperature -
1998
Lunar Prospector obtains evidence of possible water on the Moon.
