The Discovery of the Galilean Satellites . ... Probably the most significent contribution that Galileo Galilei made to science was the discovery of the four satellites around Jupiter that are now named in his honor. Galileo first observed the moons of Jupiter on January 7, 1610 through a homemade telescope. He originally thought he saw three stars near Jupiter, strung out in a line through the planet. ... Galileo's Observations of Jupiter's Moons . ... Jupiter . ...
Aristarchus of Samos, around 200 BC, proposed that the Earth revolved around the Sun, but found few supporters. ... For a discussion of the discovery of the solar system which includes a "moving picture" illustrating retrogrademotion, click here . ... The Sun and Moon, he claimed, obviously moved around Earth. ... The full story of the discovery of the solar system--of Copernicus, Galileo, Tycho and Kepler--is long and would take this discussion too far afield. ... Nicolaus Copernicus . ...
... A discussion of retrogrademotion of planets helps the students understand the logic underlying the ideas of both Ptolemy and Copernicus. ... This lesson plan supplements: "The Discovery of the Solar System," section #9c: on disk Ssolsys.htm , on the web . ... Learn about the system proposed by Copernicus, and the way it explained retrogrademotion: all planets moved in circles around the Sun, but the ones closer to the Sun always moved faster. ... Did this predict correct planetary motions? ...