The Earth And The Moon


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My lecture on the earth and the moon give as part of a series I was giving in our college.

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The Earth And The Moon

  1. 1. Earth and The Moon The Home Planet
  2. 2. Earth Evolution <ul><li>First hot and molten </li></ul><ul><li>Heavy material sank toward center </li></ul><ul><ul><li>Differentiation </li></ul></ul><ul><ul><ul><li>Heavy material sinks over time toward the center of the Earth while lighter material rises to the surface. </li></ul></ul></ul><ul><li>Earth cooled from outside in </li></ul><ul><li>Radioactivity continues today to heat interior </li></ul><ul><li>Oldest Earth rocks found on the surface today are about 3.9 billion years old </li></ul><ul><ul><li>this is known from radioactive dating </li></ul></ul><ul><ul><li>therefore, Earth formed at least 3.9 billion years ago </li></ul></ul><ul><ul><ul><li>it actually formed 4.6 billion years ago with the rest of the Solar System </li></ul></ul></ul>
  3. 3. Internal Structure
  4. 5. Revolution
  5. 6. Long Summer Days
  6. 7. Precession <ul><li>There are 2 types of precession </li></ul><ul><li>Earth is obligated 43km larger in equator </li></ul><ul><li>Tidal forces of the sun and the moon </li></ul><ul><li>25700 years period </li></ul>
  7. 9. <ul><li>The force that cause an spinning top to wobble is parallel to its rotation axis at first </li></ul><ul><li>Solar gravity is perpendicular to the Earth’s axis </li></ul><ul><li>The torque is applied to the equatorial bulge </li></ul><ul><li>The torque is always in the same direction, perpendicular the direction of equatorial poles, so it does not change the axial tilt itself. </li></ul>
  8. 11. Precession of Planetary Orbits
  9. 12. Nutation <ul><li>The period of the largest component of the Earth’s nutation is 18.6 years, the same as of the precession of the moons orbital nodes. </li></ul>
  10. 13. Magnetosphere
  11. 14. Aurora
  12. 16. Earth and The Moon Lunar Phases
  13. 19. Calculation: phase=fraction(0.20439731+t*0.03386319269) t = [UT] - [12AM, January 1, 2001], in days
  14. 22. Earth and The Moon Tidal Force
  15. 23. Tidal Force <ul><li>An effect of gravity </li></ul>
  16. 24. Angular Momentum Kepler’s law of equal areas b
  17. 25. h d v |_ v For L to be constant, then the area (a) swept by the planet in a certain length of time ( Δ t) must be always the same.
  18. 26. The high tide is not directly underneath of the moon <ul><li>Friction </li></ul><ul><li>Earth slows down 2X10-9 seconds daily </li></ul><ul><li>Angular momentum’s being transferring to the moon </li></ul><ul><li>The Moon goes farther 38mm each year </li></ul><ul><li>Tidal Acceleration </li></ul>
  19. 27. The Fate of Tidal Effects <ul><li>Earth has already slowed down the moon. </li></ul><ul><li>The period of rotation of the moon = the period of its revolution around the earth. </li></ul><ul><li>The Earth and the moon will finally lock. </li></ul><ul><li>Then the tidal effect of the sun pull the moon closer to the earth (causes the moon reach Roche limit, but 10 milliard years!) </li></ul>
  20. 28. Leap Seconds <ul><li>UT: Based on Earth’s rotation (irregular, tidal effects and melting ice sheets) </li></ul><ul><li>TT: Based on Atomic clocks. </li></ul><ul><li>Δ T = TT-UT </li></ul><ul><li>Leap seconds are being added to Atomic clocks to adjust standard time of day (UTC) close to mean solar time (UT=GMT) (noon @ noon). </li></ul><ul><li>The last leap second added in Dec. 31 2005. </li></ul>
  21. 29. Universal Time – Coordinated Universal Time
  22. 30. <ul><li>Moon Revolution < Earth Rotation so: Tidal acceleration </li></ul><ul><li>What happens for a moon if it orbit faster than the parent body’s rotation? </li></ul>
  23. 31. Earth and The Moon Lunar Impacts
  24. 32. <ul><li>Tycho crater (85km wide, 4.8km deep) </li></ul><ul><li>Central peak </li></ul><ul><li>Craters are named after astronomers </li></ul>
  25. 37. Earth and The Moon Faces of the moon
  26. 38. Near Side (0 degree)
  27. 39. Surface Features <ul><li>Maria - large flat areas resulting from lava flows </li></ul><ul><li>Fourteen (14) named maria, the largest being Mare Imbrium (1100 km diameter) </li></ul><ul><li>Highlands - lighter appearing, elevated areas </li></ul><ul><li>Craters - very old => mostly from meteoritic impact - very old </li></ul><ul><li>Far side surprise </li></ul><ul><li>no major maria => due to asymmetric crust </li></ul><ul><li>almost entirely highlands </li></ul><ul><li>Moon's surface is frozen in time: very little surface erosion </li></ul><ul><li>no wind or running water, to cause erosion </li></ul><ul><li>no plates on surface to cause volcanism or seismic activity </li></ul><ul><li>some erosion from micrometeroids </li></ul><ul><ul><li>cumulative effect of micrometeroids => dust </li></ul></ul>
  28. 40. Far Side (180 degrees)
  29. 41. The Far Side <ul><li>Is shielded form the Earth’s radiation </li></ul><ul><li>Only 2.5% of its surface is Maria </li></ul><ul><li>The crust is 40km thicker on the far side </li></ul><ul><li>Maria are denser than surface mat. </li></ul><ul><li>Moon is oriented in lowest energy configuration (by Earth’s tidal force). </li></ul>
  30. 42. Earth and The Moon Lunar Eclipses
  31. 43. The Red Moon
  32. 44. How?
  33. 45. Compare Distances
  34. 48. <ul><li>Starts: 16 Shahrivar 20:12 </li></ul><ul><li>Ends 17 Shahrivar 00:30 (Tehran Time) </li></ul>
  35. 49. Earth and The Moon Libration
  36. 51. Types of Librations <ul><li>In Latitude: Moon axis is inclined </li></ul><ul><li>In Longitude: The velocity of the moon in its elliptical orbit varies </li></ul><ul><li>Diurnal (daily) </li></ul><ul><li>We can see 59% of the moon due libration </li></ul>
  37. 53. Earth and The Moon Formation
  38. 54. Giant Impact <ul><li>A Mars-size object firstly located in Lagrangian Point L4 or L5 hit the early Earth, just in the best situation </li></ul>
  39. 56. Roche Limit