Ch 23


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Ch 23

  1. 1. Ch 23 Section I The Earth
  2. 2. Properties of the Earth <ul><li>people used to think that Earth was flat and at the centre of the universe </li></ul>
  3. 4. Earth is a round 3-dimensional sphere
  4. 5. Proof the Earth is round <ul><li>Aristotle saw a curved shadow on moon during an eclipse </li></ul><ul><li>See top of ship sails first </li></ul><ul><li>Sailors noticed different stars in the night sky </li></ul>
  5. 6. Axis – imaginary vertical line around which earth spins
  6. 7. Rotation – the spinning of Earth around its axis that causes day and night Takes 24 hrs. or 1 day
  7. 8. Earth has a magnetic field with north and south poles
  8. 9. Caused by: <ul><li>1- the movement of material in core </li></ul><ul><li>2- Earth’s rotation </li></ul><ul><li>Protects us from harmful solar radiation by trapping charged particles </li></ul>
  9. 10. Magnetic north vs. geographic north
  10. 11. Revolution – Earth’s yearly orbit around the sun
  11. 12. Revolution vs. rotation <ul><li>Revolution – trip around Sun </li></ul><ul><li>Earth orbits around the Sun </li></ul><ul><li>Earth is a satellite of the Sun </li></ul><ul><li>Rotation – spinning on axis </li></ul><ul><li>Cause of night/day </li></ul>
  12. 13. Earth’s orbit is an ellipse or elongated, closed curve
  13. 14. <ul><li>The Sun is not centered in the ellipse </li></ul><ul><li>Perihelion : closest point (winter) </li></ul><ul><li>Aphelion : furthest point (summer) </li></ul>
  14. 15. Distance from Sun <ul><li>Earth closest Jan. 3: </li></ul><ul><ul><ul><li>147 million kilometers </li></ul></ul></ul><ul><li>Earth furthest July 4: </li></ul><ul><ul><ul><li>152 million kilometers </li></ul></ul></ul><ul><li>Small difference 5 million kilometers so… </li></ul><ul><ul><li>Earth is exposed to almost the same amount of Sun year round </li></ul></ul>
  15. 16. Earth’s tilt causes the seasons
  16. 17. <ul><li>Tilt causes radiation to strike at different angles </li></ul><ul><li>The more direct the angles receive more radiation </li></ul>
  17. 18. Seasons on Earth <ul><li>The height of the sun above the horizon varies with the season. </li></ul>
  18. 19. Solstice <ul><li>the day when the sun reaches its greatest distance north or south of the equator </li></ul><ul><li>Summer solstice: June 21 or 22 in northern hemisphere </li></ul><ul><ul><li>Sun directly over Tropic of Cancer </li></ul></ul><ul><li>Winter solstice: December 21 or 22 in northern hemisphere </li></ul><ul><ul><li>Sun directly over Tropic of Capricorn </li></ul></ul>
  19. 20. Equinox <ul><li>the day when the sun is directly over Earth’s equator </li></ul><ul><li>Daytime and nighttime hours are equal all over the world </li></ul>
  20. 21. <ul><li>Vernal (Spring) equinox: March 20 or 21 in northern hemisphere </li></ul><ul><li>Autumnal (Fall) equinox: September 22 or 23 in northern hemisphere </li></ul>
  21. 23. Geocentric – everything revolves around earth
  22. 24. Heliocentric – everything revolves around the sun
  23. 25. Moon
  24. 26. Motions of the moon <ul><li>rotates on its axis </li></ul><ul><li>takes 27.3 days for one revolution </li></ul><ul><li>Always the same side facing earth b/c moon rotates and revolves at the same speed </li></ul>
  25. 27. The moon seems to shine because it reflects sunlight
  26. 28. Games/activities <ul><li> </li></ul><ul><li>http:// </li></ul><ul><li> </li></ul>
  27. 29. Moon Phases – the different forms the Moon takes in its appearance from Earth
  28. 30. New Moon – when the moon is between earth and the sun and cannot be seen
  29. 31. Waxing phases <ul><li>more of the illuminated half of the moon that can be seen each night after the new moon </li></ul>
  30. 32. First visible thin slice of the moon is a waxing crescent
  31. 33. <ul><li>First quarter phase – half the lit side of the moon is visible </li></ul><ul><li>Waxing gibbous – more than one quarter is visible </li></ul>
  32. 34. All of the Moon’s lit side is visible during a full moon
  33. 35. Waning phases – less of the illuminated half of the Moon is visible after the full moon.
  34. 36. <ul><li>Waning gibbous – starts after a full moon where more than half of the lit side is still visible. </li></ul><ul><li>Third quarter - half the Moon’s lit side is visible </li></ul>
  35. 37. The last visible slice before a new moon is called the waning crescent
  36. 38. <ul><li>Phases of the Moon </li></ul>
  37. 39. What time period did we get from studying the moon? Completes its moon cycle in 29.5 days Completes revolution in 27.3 days
  38. 40. The moon’s orbit is tilted about 5 degrees relative to Earth’s orbit around the sun.
  39. 41. visuals <ul><li> </li></ul>
  40. 42. Eclipses – when the Earth or the moon casts a shadow on the other
  41. 43. Solar Eclipse <ul><li>the moon moves directly between the Earth and the Sun, shadowing part of the Earth </li></ul>
  42. 44. Penumbra – experiences a partial eclipse Umbra – experiences a total eclipse
  43. 45. A total solar eclipse is visible only on a small area of Earth The corona is the silvery part
  44. 48. Lunar Eclipse – when Earth’s shadow falls on the moon What color does the moon turn during as eclipse?
  45. 49. Does not occur every month because the moon’s orbit is tilted to earth’s orbit.
  46. 50. <ul><li>NASA - Total Lunar Eclipse: February 20, 2008 </li></ul>
  47. 51. The moon is 3,476 km in diameter, a little less than the distance across the contiguous United States.
  48. 52. Moon’s gravity is 1/6 of Earth’s gravity because it is less massive
  49. 53. The Moon’s surface has many depressions, or craters. formed from meteorites, asteroids, and comets
  50. 54. What could destroy the footprint?
  51. 55. Cracks in the Moon’s crust caused lava to fill large craters, forming maria, or dark, flat areas Mountainous area called highlands
  52. 56. <ul><li>http:// </li></ul><ul><li>Shows marias </li></ul>
  53. 57. Regolith is the broken rock material on the moon’s surface. Moon rocks are similar to ours and have tiny crystals of pure iron.
  54. 58. Data from moonquakes suggest that under the Moon’s crust might lie a solid mantle, then a partly molten mantle and a solid, iron rich, core.
  55. 59. Impact Theory of Moon Origin <ul><li>the Moon formed 4.6 billion years ago from Earth material thrown off when a large object collided with Earth </li></ul>
  56. 60. Impact Basins <ul><li>or craters, are depressions left by objects striking the Moon (or anything else!!!!!) </li></ul>
  57. 61. Arizona Crater <ul><li>20,000-50,000 years ago </li></ul><ul><li>Asteroid 80 feet in diameter </li></ul><ul><li>1.2 kilometers in diameter </li></ul>
  58. 62. Chicxulub, Mexico <ul><li>Now covered by the Yucatan Penninsula </li></ul><ul><li>Asteroid 6 mi (10 km) </li></ul><ul><li>Crater diameter 110 miles (180 km) </li></ul><ul><li>65 million years ago </li></ul><ul><li>Cretaceous period </li></ul>
  59. 63. Albedo reflectance
  60. 64. Albedo of 0
  61. 65. Albedo of 1
  62. 66. Clementine <ul><li>January 25, 1994 </li></ul><ul><li>Objective to test lightweight sensors </li></ul><ul><li>Task was to map the surface of the moon </li></ul><ul><li>Cost 80 million </li></ul><ul><li>Bet. 2/26 – 4/22 1.8 million images </li></ul><ul><li>Carried cameras – infrared to ultraviolet </li></ul>
  63. 67. Clementine Northside Farside Nearside Southside
  64. 68. Clementine <ul><li>3 billion metric tons at poles </li></ul>
  65. 69. Lunar Prospector <ul><li>Desk sized </li></ul><ul><li>1998 </li></ul><ul><li>Confirmed impact theory </li></ul>
  66. 70. Graphic Organizer rotates revolves causing causing Earth
  67. 71. Graphic Organizer rotates revolves causing causing Earth On its axis Night and day Around the Sun years