History Of Astronomy (Thru Newton)

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History Of Astronomy (Thru Newton)

  1. 1. History of Astronomy<br />Ancient Cultures to Isaac Newton<br />
  2. 2. Early Civilizations<br />A practical approach<br />Predicting seasons<br />Navigation<br />
  3. 3. Aristotle and the Greek View: Geocentric Model<br />Geo- Earth<br />Centric- Centered<br />The earth is a motionless sphere at the center of the Universe. <br />Explained the apparent motion of the sun, moon and stars.<br />
  4. 4.
  5. 5. Planets<br />Greek astronomers observed that certain celestial objects do not follow a predictable path like the moon, sun, and stars.<br />Called these objects Planets (Greek word planetes means wanderer)<br />The observable motion of Planets is that they change speed and even loop back and forth relative to the stars. <br />
  6. 6. Retrograde Motion<br />Motion of planets in “backwards” or westward loops is known as Retrograde Motion.<br />
  7. 7. Ptolemy (140 A.D.)<br />A more complex model of the Universe/Solar System was needed to explain Retrograde Motion. <br />Ptolemy suggests that planets orbit the Earth in a large circular orbits but also follow a small circular orbit around an imaginary point. <br />These small orbits were known as Epicycles <br />
  8. 8. The Copernican Revolution: Heliocentric Model<br />Ptolemaic Model survived for 13 centuries<br />Copernicus suggested that the Earth is a planet and spins on its axis and orbits the Sun.<br />Heliocentric- Sun Centered<br />This accounts for the apparent motion of the sun and stars.<br />The realization that Earth is not at the center of the universe is now know as the Copernican Revolution.<br />What about Retrograde motion of the planets?<br />
  9. 9. Just like when you pass another car on the highway. <br />
  10. 10. Galileo Galilei<br />Used the telescope to view objects in the sky (1609). <br />Observations of celestial objects supported the Heliocentric Model of the solar system.<br />
  11. 11. Galileo’s Observations <br />The terrain of the Moon, Sunspots, the moons of Jupiter<br />Phases of Venus<br />
  12. 12. Johannes Kepler<br />A student of Tycho Brahe, Kepler used the precise data of his mentor to develop three simple laws that describe the motion of planets. <br />
  13. 13. Kepler’s Laws of Planetary Motion<br />The orbital paths of planets are elliptical with the Sun at one focus.<br />An imaginary line connecting the Sun to any planet sweeps out equal areas of the ellipse in equal intervals of time.<br />The square of a planet’s orbital period is proportional to the cube of its semi-major axis. <br />
  14. 14. Kepler’s Laws certainly describe the motion of planets around the Sun but they tell us nothing about WHY planets orbit the Sun. <br />What prevents the planets from flying off into space or from falling into the Sun? <br />
  15. 15. Isaac Newton<br />Described the basic laws of motion in what is now known as Newtonian mechanics. <br />Newton’s 3 Laws of Motion. <br />The Law of Universal Gravitation<br />
  16. 16. Newton’s Laws<br />Inertia: An object in motion stays in motion, an object at rest remains at rest, unless acted upon by a force. <br />F = ma<br />To every action there is an equal and opposite reaction.<br />
  17. 17. Universal Gravitation<br />Every particle of matter in the universe attracts every other particle with a a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them. <br />
  18. 18. Gravity: Why we orbit the Sun.<br />

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