FOUNDATIONS OF ASTRONOMY Casey Trout

ANCIENT BELIEFS Ancient cultures learned how to predict the weather, the seasons, time of day, & eclipses In Central Africa, people found that the orientation of crescent moon revealed rainfall patterns The origin of our modern clock is traced to Egypt Stonehenge kept track of the seasons Many ancient structures indicated when the solstices would occur Sun Dagger in Chaco Canyon, New Mexico Templo Mayor in Tenochtitlán The Babylonians successfully predicted eclipses Stonehenge

GREEK SCIENCE Emphasis on mathematics, rationality, and observations led to astronomical discoveries Geocentric model: Earth at center of universe Heavenly bodies move in circles, are perfectly smooth & round Ptolemaic model accounted for apparent retrograde motion Each planet moves around a small circle whose center moves around Earth Geocentric Model

ISLAMIC SCIENCE Muslim scientists preserved astronomical findings throughout the European Middle Ages “House of Wisdom” established in 800 ce by Al- Mamun Most constellations & stars were named by Arab scholars House of Wisdom

SCIENTIFIC REVOLUTION: COPERNICUS Influenced by Aristarchus’s heliocentric ideas Discovered simple geometric relationships that were used to calculate each planet’s orbital period around the Sun & relative distance from the Sun Published “Concerning the Revolutions of the Heavenly Spheres” on May 24, 1543 Heavenly motion occurred in perfect circles, leading to a complex & inaccurate model Copernicus

SCIENTIFIC REVOLUTION: TYCHO BRAHE Tediously observed & recorded the stellar & planetary cycles Observed a nova, proved that it was much farther away than our Moon Believed planets orbited the Sun, but inability to detect stellar parallax led him to believe that the Earth must remain stationary

SCIENTIFIC REVOLUTION: JOHANNES KEPLER Hired by Tycho in 1600 Developed a model that accounted for Tycho’s observations Initially believed that the heavenly bodies moved in circular orbits, but later argued that they move in ellipses Developed a model that predicted planetary motions with far greater accuracy than Ptomely & Copernicus Suggested that a force of the Sun may be the reason for planetary motion Kepler

KEPLER’S THREE LAWS OF PLANETARY MOTION Kepler’s Second Law

SCIENTIFIC REVOLUTION: GALILEO Proved that a moving object remains in motion unless a force acts to stop it Observed sunspots & craters on the Moon, disproving the notion that heavenly bodies were perfectly smooth Argued that the stars were too distant to predict stellar parallax Discovered that the Milky Way was composed of many more stars than previously believed Observed four moons orbiting Jupiter & the phases of Venus, demonstrating that they must orbit the Sun Galileo Milky Way

SCIENTIFIC REVOLUTION: NEWTON’S THREE LAWS OF MOTION Believed that the force that makes an apple fall also causes the Moon to stay in orbit around the Earth 1. An object moves at constant velocity if there is no net force acting upon it Objects at rest tend to remain at rest, objects in motion tend to remain in motion Friction & air resistance cause objects to slow down & stop on Earth 2. Force = mass x acceleration Explains why larger bodies have a greater effect on smaller bodies (more mass) 3. For any force, there is always and equal and opposite reaction force Objects attract each other through gravity Newton

THUS, THE FOUNDATION OF MODERN ASTRONOMY WAS FORMED

WORKS CITED Bennett, Jeffrey, Megan Donahue, Nicholas Schneider, and Mark Voit. The Essential Cosmic Perspective. 5 th ed. San Francisco: Pearson Education, Inc., Print.