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Ch 23

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Transcript

  • 1. Ch 23 Section I The Earth
  • 2. Properties of the Earth
    • people used to think that Earth was flat and at the centre of the universe
  • 3.  
  • 4. Earth is a round 3-dimensional sphere
  • 5. Proof the Earth is round
    • Aristotle saw a curved shadow on moon during an eclipse
    • See top of ship sails first
    • Sailors noticed different stars in the night sky
  • 6. Axis – imaginary vertical line around which earth spins
  • 7. Rotation – the spinning of Earth around its axis that causes day and night Takes 24 hrs. or 1 day
  • 8. Earth has a magnetic field with north and south poles
  • 9. Caused by:
    • 1- the movement of material in core
    • 2- Earth’s rotation
    • Protects us from harmful solar radiation by trapping charged particles
  • 10. Magnetic north vs. geographic north
  • 11. Revolution – Earth’s yearly orbit around the sun
  • 12. Revolution vs. rotation
    • Revolution – trip around Sun
    • Earth orbits around the Sun
    • Earth is a satellite of the Sun
    • Rotation – spinning on axis
    • Cause of night/day
  • 13. Earth’s orbit is an ellipse or elongated, closed curve
  • 14.
    • The Sun is not centered in the ellipse
    • Perihelion : closest point (winter)
    • Aphelion : furthest point (summer)
  • 15. Distance from Sun
    • Earth closest Jan. 3:
        • 147 million kilometers
    • Earth furthest July 4:
        • 152 million kilometers
    • Small difference 5 million kilometers so…
      • Earth is exposed to almost the same amount of Sun year round
  • 16. Earth’s tilt causes the seasons
  • 17.
    • Tilt causes radiation to strike at different angles
    • The more direct the angles receive more radiation
  • 18. Seasons on Earth
    • The height of the sun above the horizon varies with the season.
  • 19. Solstice
    • the day when the sun reaches its greatest distance north or south of the equator
    • Summer solstice: June 21 or 22 in northern hemisphere
      • Sun directly over Tropic of Cancer
    • Winter solstice: December 21 or 22 in northern hemisphere
      • Sun directly over Tropic of Capricorn
  • 20. Equinox
    • the day when the sun is directly over Earth’s equator
    • Daytime and nighttime hours are equal all over the world
  • 21.
    • Vernal (Spring) equinox: March 20 or 21 in northern hemisphere
    • Autumnal (Fall) equinox: September 22 or 23 in northern hemisphere
  • 22.  
  • 23. Geocentric – everything revolves around earth
  • 24. Heliocentric – everything revolves around the sun
  • 25. Moon
  • 26. Motions of the moon
    • rotates on its axis
    • takes 27.3 days for one revolution
    • Always the same side facing earth b/c moon rotates and revolves at the same speed
  • 27. The moon seems to shine because it reflects sunlight
  • 28. Games/activities
    • http://www.sciencenetlinks.com/interactives/moon/moon_challenge/moon_challenge.html
    • http:// www.engagingscience.org/games/onlinegames/games.html
    • http://aspire.cosmic-ray.org/labs/moon/lunar_phases_main.html
  • 29. Moon Phases – the different forms the Moon takes in its appearance from Earth
  • 30. New Moon – when the moon is between earth and the sun and cannot be seen
  • 31. Waxing phases
    • more of the illuminated half of the moon that can be seen each night after the new moon
  • 32. First visible thin slice of the moon is a waxing crescent
  • 33.
    • First quarter phase – half the lit side of the moon is visible
    • Waxing gibbous – more than one quarter is visible
  • 34. All of the Moon’s lit side is visible during a full moon
  • 35. Waning phases – less of the illuminated half of the Moon is visible after the full moon.
  • 36.
    • Waning gibbous – starts after a full moon where more than half of the lit side is still visible.
    • Third quarter - half the Moon’s lit side is visible
  • 37. The last visible slice before a new moon is called the waning crescent
  • 38.
    • Phases of the Moon
  • 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
  • 40. The moon’s orbit is tilted about 5 degrees relative to Earth’s orbit around the sun.
  • 41. visuals
    • http://www.ioncmaste.ca/homepage/resources/web_resources/CSA_Astro9/files/multimedia/unit3/phases_moon/phases_moon.html
  • 42. Eclipses – when the Earth or the moon casts a shadow on the other
  • 43. Solar Eclipse
    • the moon moves directly between the Earth and the Sun, shadowing part of the Earth
  • 44. Penumbra – experiences a partial eclipse Umbra – experiences a total eclipse
  • 45. A total solar eclipse is visible only on a small area of Earth The corona is the silvery part
  • 46.  
  • 47.  
  • 48. Lunar Eclipse – when Earth’s shadow falls on the moon What color does the moon turn during as eclipse?
  • 49. Does not occur every month because the moon’s orbit is tilted to earth’s orbit.
  • 50.
    • NASA - Total Lunar Eclipse: February 20, 2008
  • 51. The moon is 3,476 km in diameter, a little less than the distance across the contiguous United States.
  • 52. Moon’s gravity is 1/6 of Earth’s gravity because it is less massive
  • 53. The Moon’s surface has many depressions, or craters. formed from meteorites, asteroids, and comets
  • 54. What could destroy the footprint?
  • 55. Cracks in the Moon’s crust caused lava to fill large craters, forming maria, or dark, flat areas Mountainous area called highlands
  • 56.
    • http:// stardate.org/pdfs/teachers/ObservingTheMoon.pdf
    • Shows marias
  • 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.
  • 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.
  • 59. Impact Theory of Moon Origin
    • the Moon formed 4.6 billion years ago from Earth material thrown off when a large object collided with Earth
  • 60. Impact Basins
    • or craters, are depressions left by objects striking the Moon (or anything else!!!!!)
  • 61. Arizona Crater
    • 20,000-50,000 years ago
    • Asteroid 80 feet in diameter
    • 1.2 kilometers in diameter
  • 62. Chicxulub, Mexico
    • Now covered by the Yucatan Penninsula
    • Asteroid 6 mi (10 km)
    • Crater diameter 110 miles (180 km)
    • 65 million years ago
    • Cretaceous period
  • 63. Albedo reflectance
  • 64. Albedo of 0
  • 65. Albedo of 1
  • 66. Clementine
    • January 25, 1994
    • Objective to test lightweight sensors
    • Task was to map the surface of the moon
    • Cost 80 million
    • Bet. 2/26 – 4/22 1.8 million images
    • Carried cameras – infrared to ultraviolet
  • 67. Clementine Northside Farside Nearside Southside
  • 68. Clementine
    • 3 billion metric tons at poles
  • 69. Lunar Prospector
    • Desk sized
    • 1998
    • Confirmed impact theory
  • 70. Graphic Organizer rotates revolves causing causing Earth
  • 71. Graphic Organizer rotates revolves causing causing Earth On its axis Night and day Around the Sun years

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