Eclipses And Tides


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  • Moon appears reddish due to light bent by Earth’s atmosphere Aristotle argues earth is round based on shape of its shadow on the moon
  • Eclipses And Tides

    1. 1. Eclipses <ul><li>One celestial object hidden by other or in the shadow of another </li></ul><ul><li>Solar eclipse: sun hidden by the moon </li></ul><ul><li>Lunar eclipse: moon in earth’s shadow (sun hidden from moon by earth) </li></ul><ul><li>Spectacular because moon and sun appear to be the same size from earth </li></ul>
    2. 2. Solar Eclipses The Sun is vanishing! The Sun is going out! The daylight is retreating!
    3. 3. The Modern View The answer lies hidden among the shadows. Earth Moon
    4. 4. Shadow Structure Umbra Penumbra Penumbra
    5. 5. Solar Eclipses <ul><li>Umbra – region of total shadow </li></ul><ul><li>Penumbra – region of partial shadow </li></ul><ul><li>Totality lasts only a few minutes! </li></ul><ul><li>Why isn’t there a solar eclipse every month? </li></ul>
    6. 6. Inside the Umbra <ul><li>It gets dark </li></ul><ul><li>Temperatures drop </li></ul><ul><li>Birds stop singing </li></ul><ul><li>Nature slows down </li></ul>
    7. 7. Solar Eclipse Details Moon What is the phase of the moon? New Moon! South Pole North Pole Sun
    8. 8. Solar Eclipse Images
    9. 12. Total Solar Eclipse
    10. 13. Solar Eclipse
    11. 15. A Total Solar Eclipse from beginning to end
    12. 18. Interesting Features
    13. 20. The Diamond Ring
    14. 21. Why not a solar eclipse every month then? Sun Ecliptic Moon Moon’s Orbit Earth 5 o Moon's orbit is tilted about 5 o with respect to the Earth's orbit (ecliptic), so the shadows usually miss!
    15. 22.    But, the Moon passes through the ecliptic twice a month.  *IF* at new moon - SOLAR ECLIPSE probability.
    16. 23. Annular Solar Eclipse
    17. 24. Partial Solar Eclipse During a total solar eclipse, depending on your location during the event, you might only see part of the Sun’s face blocked because of your observing vantage point.
    18. 25. Lunar Eclipses <ul><li>Moon moves into earth’s shadow… </li></ul>… and out of it (takes hours!)
    19. 26. A Lunar Eclipse Moon A lunar eclipse occurs when the Earth lies between the Sun and Moon, so that Earth's shadow darkens the Moon. Sun Earth Moon’s Path
    20. 27. This image shows a complete transition during a lunar eclipse. Notice that the phase of the moon is “full.”
    21. 29. The moon becomes a blood red color during a total lunar eclipse. No wonder that ancient cultures feared the appearance of the moon during a lunar eclipse.
    22. 30. Totality Totality Q: Why does the Moon look orange in total lunar eclipses
    23. 31. Totality Totality A: Because the sky on Earth is blue. The Earth’s atmosphere’s air molecules filter out red & orange frequencies by scattering them into Earth’s night side. This “ rest light” illuminates the Moon (weakly).
    24. 32. The Blood Moon The moon often does not totally disappear during a total lunar eclipse. Instead it can be seen as a very dark red color because of the refraction of sunlight through the Earth's atmosphere. Earth’s Atmosphere Sunlight Moon Earth
    25. 34. Lunar Eclipse Types Total Penumbral Eclipse Total Lunar Eclipse Partial Lunar Eclipse Partial Penumbral Eclipse
    26. 35. Tides <ul><li>Daily fluctuations in the ocean levels </li></ul><ul><li>Two high and two low tides per day </li></ul><ul><li>A result of the difference in gravitational pull from one side of the Earth to the other </li></ul>
    27. 36. The idea behind Tides <ul><li>There are two tidal bulges, i.e. two high tides per day, because: </li></ul><ul><ul><li>Moon pulls water towards it on one side </li></ul></ul><ul><ul><li>Earth is pulled towards the Moon, away from the water on the other side </li></ul></ul>Force of Moon on water (strong) Force of Moon on Earth (weaker) Force of Moon on “back-water” (much weaker)
    28. 37. Spring and Neap Tides <ul><li>Tides especially pronounced when Sun and Moon “work together” </li></ul><ul><li>Same direction  Spring tide </li></ul><ul><li>Other direction  Neap tide </li></ul>
    29. 38.