Topic Pioneers In Astronomy (2008)

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Topic Pioneers In Astronomy (2008)

  1. 1. Pioneers in Astronomy <ul><li>Ptolemy </li></ul><ul><li>Copernicus </li></ul><ul><li>Tycho Brahe </li></ul><ul><li>Kepler </li></ul><ul><li>Galileo </li></ul><ul><li>Newton </li></ul><ul><li>Halley </li></ul><ul><li>Le Verrier & Adams </li></ul>Uraniborg, Tycho Brahe’s Observatory
  2. 2. Ptolemy <ul><li>Almagest (150 AD), Ptolemy described the Greek geocentric (earth-centered) model of the universe </li></ul><ul><li>Order outward from the earth based on their apparent speeds of motion </li></ul><ul><li>Orbits were considered circles </li></ul>
  3. 3. Ptolemaic System http://www.thebigview.com/spacetime
  4. 4. Retrograde Mars, 1995
  5. 5. Retrograde Mars (2003) http://zuserver2.star.ucl.ac.uk/~apod/apod/ap031216.html
  6. 6. Ptolemy’s Epicycle
  7. 7. Retrograde Planetary Motion <ul><li>Animation 2.1: Retrograde Motion </li></ul><ul><li>Animation 2.2: The Path of Mars </li></ul><ul><li>“It is most retrograde to our desire…” </li></ul><ul><li>— Hamlet </li></ul>
  8. 8. Nicholas Copernicus <ul><li>Copernicus (1473-1543) developed heliocentric (sun-centered) model of the solar system </li></ul><ul><li>His book, De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres, 1543), is considered the starting point of modern astronomy </li></ul>
  9. 9. Copernican System
  10. 10. Copernican Revolution <ul><li>In the Copernican solar system, the retrograde motion of Mars is seen when the Earth passes Mars in its orbit around the Sun </li></ul>
  11. 11. Retrograde Mars (June 2007)
  12. 12. Heliocentric Explanation <ul><li>Animation 2.3: A Heliocentric Explanation of Retrograde Motion </li></ul>
  13. 13. Tycho Brahe <ul><li>Tycho Brahe (1546-1601) recorded precise observations of the positions of the planets and stars </li></ul><ul><li>Tycho’s data was used by Kepler to formulate the laws of planetary motion </li></ul>
  14. 14. Tycho’s System <ul><li>Tycho created a compromise between the universes of Ptolemy and Copernicus </li></ul><ul><li>Planets orbit sun, sun orbits earth </li></ul>http://media4.obspm.fr/public/IUFM/images/13Kepler/images/ticho_brahe.png
  15. 15. Johannes Kepler <ul><li>Using Tycho’s observations, Johannes Kepler (1571-1630) deduced three laws of planetary motion </li></ul>
  16. 16. Kepler’s First Law <ul><li>K1: The orbit of a planet around the Sun is an ellipse with the Sun at one focus </li></ul>
  17. 17. Elliptical Orbits
  18. 18. Close and Far <ul><li>Perihelion: The point in a planet’s orbit closest to the Sun </li></ul><ul><li>Aphelion: Point farthest from sun </li></ul><ul><li>Earth, 2007 </li></ul><ul><li>Perihelion: Jan 03 </li></ul><ul><li>Aphelion: July 07 </li></ul>
  19. 19. Kepler’s Second Law <ul><li>K2: A line joining the planet and the Sun sweeps out equal areas in equal intervals of time </li></ul><ul><li>Planets speed up as they approach the sun, slow down when the move away from the sun </li></ul><ul><li>K1, K2 published in 1609, Astronomia Nova </li></ul>
  20. 20. Equal Areas Planet moves faster in its orbit when closer to the Sun. Planet moves slower in its orbit when farther away from the Sun.
  21. 21. Kepler’s First & Second Laws <ul><li>Animation 2.4: Kepler’s First and Second Laws </li></ul>
  22. 22. Kepler’s Third Law (Harmonic, 1619) <ul><li>K3: The square of a planet’s sidereal period (P) around the Sun is directly proportional to the cube of its semi-major axis (a) </li></ul><ul><li>P 2 = a 3 </li></ul><ul><li>The results are in astronomical units (AU) with earth = 1 </li></ul><ul><li>1 AU = 93,000,000 miles </li></ul><ul><li>Demo: Click </li></ul>
  23. 23. Galileo <ul><li>Galileo (1564-1642), first scientist to use a telescope to examine the night sky </li></ul><ul><li>Discoveries supported the Copernican system </li></ul>
  24. 24. Phases of Venus
  25. 25. Moons of Jupiter (Galileo, 1610)
  26. 26. Isaac Newton <ul><li>Isaac Newton (1643-1727) </li></ul><ul><li>Laws of motion </li></ul><ul><li>Law of gravity </li></ul><ul><li>Invented calculus </li></ul><ul><li>Newton’s laws were first published in the Philosophiae Naturalis Principia Mathematica , or Principia , 1687 </li></ul>
  27. 27. Newton’s First Law <ul><li>N1: A body remains at rest or moves in a straight line at constant speed unless acted upon by a net outside force </li></ul><ul><li>Spaceship moving in space </li></ul>
  28. 28. Newton’s Second Law <ul><li>N2: The acceleration (a) of an object is proportional to the force (F) acting on it </li></ul><ul><li>F = ma </li></ul><ul><li>m = mass of object </li></ul><ul><li>Spin ball on a string </li></ul>
  29. 29. Newton’s Third Law <ul><li>Whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body </li></ul><ul><li>Or, every action has an equal and opposite reaction </li></ul><ul><li>Rocket liftoff </li></ul>
  30. 30. Law of Gravity <ul><li>Law of Universal Gravitation </li></ul><ul><li>Two objects attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. </li></ul>
  31. 31. Newtonian Orbits
  32. 32. Conic Sections <ul><li>Slice a cone at various angles </li></ul><ul><li>Resulting shapes same as planetary orbits </li></ul><ul><li>Practical math, Greece, 200 BC </li></ul>
  33. 33. Comet & Planetary Orbits <ul><li>Animation 2.5: Planetary Orbits </li></ul><ul><li>Animation 2.6: Orbit & Tail of a Comet </li></ul>
  34. 34. Newton’s Cannon
  35. 35. “Cannon” Orbits
  36. 36. Edmond Halley <ul><li>Edmond Halley (1656-1742) used Newton’s methods to describe a comet’s orbit and predict its return </li></ul><ul><li>Halley explained comet sightings of 1456, 1531, 1607, and 1682 to be the same comet </li></ul><ul><li>Predicted return in 1758 </li></ul><ul><li>Comet Halley was last visible in 1986 and will return in 2061 </li></ul>
  37. 37. Comet Halley Portion of Bayeux Tapestry, 1066 Comet Halley in 1986, Milky Way in upper right
  38. 38. Le Verrier and Adams <ul><li>English astronomer John Couch Adams (1819-1892) and French astronomer Urbain Jean Joseph Le Verrier (1811-1877) independently predicted the existence of Neptune </li></ul><ul><li>Predictions based upon Neptune’s gravitational effect upon Uranus </li></ul><ul><li>Neptune was discovered at the Berlin Observatory on Sept 23, 1846 </li></ul>Le Verrier (left) & Adams
  39. 39. Neptune’s Positions 1-degree equals the width of an oustretched fingertip
  40. 40. Inferior & Superior <ul><li>Planet positions compared to earth </li></ul><ul><li>Inferior Planets : Between sun and earth </li></ul><ul><ul><li>Mercury, Venus </li></ul></ul><ul><li>Superior Planets : Farther from the sun than earth </li></ul><ul><ul><li>Mars, Jupiter, Saturn, Uranus, Neptune, (Pluto) </li></ul></ul>
  41. 41. Inferior Planets <ul><li>Eastern and western elongation </li></ul><ul><li>Inferior conjunction </li></ul><ul><li>Superior conjunction </li></ul>
  42. 42. Superior Planets <ul><li>Opposition </li></ul><ul><li>Conjunction </li></ul>
  43. 43. Close & Far
  44. 44. Summary

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