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The Early Astronomers Astronomy Astronomy: the study of the universe Earth = 1 of 8 planets & many smaller bodies orbiting the sun Sun = 1 of billions of stars in our galaxy - Milky Way Galaxy Milky Way = 1 of billions of galaxies making up the Universe Claudius Ptolemy Geocentric Model (Geo= Earth, Centic=Center) Earth is at the center of the universe • The sun and planets revolved around Earth • Evidence: All objects seem to fall towards the center of Earth. • Observation of the sun and planets from Earth Geocentric Model Eventually Proven Incorrect Review Questions 1. List two types of evidence that Ptolemy used to create the geocentric model. 2. What is the main difference between the geocentric and heliocentric models? 3. Kepler discovered that the planets orbit in an ________ around the sun. Nicolas Copernicus Heliocentric Model(Helio: Sun, Centric: center) All the spheres revolve about the sun as their mid-point, and therefore the sun is the center of the universe. Earth is a planet http://science.howstuffworks.com/29276-100-greatestdiscoveries-elliptical-orbits-video.htm Johannes Kepler Born 1571-1630 Started working on lenses for magnification 3 Laws of Planetary Motion (we only need the 1st one) 1. every planet orbits in an ellipse around the sun I. The orbits of the planets are ellipses, with the Sun at one focus of the ellipse. http://science.howstuffworks.com/29276-100-greatestdiscoveries-elliptical-orbits-video.htm Kepler's Third Law • implies that the period for a planet to orbit the Sun increases rapidly with the radius of its orbit. • Thus, we find that Mercury, the innermost planet, takes only 88 days to orbit the Sun but the outermost planet (Pluto) requires 248 years to do the same. AU= 1 astronomical unit. 1AU= 150,000,000km from sun to earth. Galileo Galilei 1564 - 1642 "father of modern observational astronomy", Galileo di Vincenzo Bonaiuti de' Galilei Discoveries Invented and used the Telescope. Used the lens that Tycho had invented. Discovered that planets are round balls. Galileo Sun-Centered System PBS LearningMedia.mp4 Early Telescope like Galilei’s Phases of Venus Galileo Galilei Discovered Moon’s surface is not smooth, He saw • Mountains, • Craters • Plains Galileo Galilei Discovered the sun has “sun Spots” that change Discovered that the sun rotates also. Sir Isaac Newton 1642-1727 Newton was the first to formulate and test the law of universal gravitation. He believed that everybody in the universe attracts every other body with a force between their centers of mass. Gravity… Newton proved that without the influence of gravity, planets would move in a straight line out into space. ..\Gravity at Earth's Center Science Classroom Resources PBS Learning Media.mp4