Galileo Galilei

• Galileo Galilei taught geometry, mechanics and astronomy at the University of Padua from 1592 to 1610.
• Galileo built his first telescope in 1609, which featured three times magnification. Later, he developed models that could see up to 30 times magnification.
• He published his first astronomical observations in 1610. The collection was called “Starry Messenger.”
• In January of 1610, Galileo discovered four satellites in orbit around Jupiter: Io,Europa, Callisto and Ganymede. Initially, he named these Medicean stars after one of his patrons.
• In September of that same year, he made a number of observations about Venus. He was able to develop a full set of phases of the planet. This helped prove the heliocentric concept of the solar system first developed by Copernicus.
• While observing Saturn, he identified the rings as planets in their own right. Thinking it was a triple-planetary system, he noticed that the rings would appear and disappear depending on the time in which he was observing them.
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• Galileo also was one of the first people to observe sunspots, which helped develop the predictions that would help identify the annual patterns.
• Using his telescopes, he was able to identify that the Moon had mountains and craters, dispelling the belief that it was a perfect sphere.
• Galileo also found that the Milky Way was actually close-packed stars rather than some sort of nebula. He was able to locate a number of stars previously unseen with the naked eye.
• According to his notes, he observed the planet Neptune in 1612, but did not recognize it as a planet. He thought it was simply another dim star.
• As one of his final works, he published a manuscript entitled “Two New Sciences,” in which he examined the movement of objects called kinetics and the strength of materials to certain stresses.