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Cycles of the Sky

Cycles of the Sky. Sun, Moon & Seasons. EARTH IN MOTION. The Earth is not just “sitting” out in space, what is it doing? ROTATING spinning counterclockwise on it’s axis 23 hours, 56 minutes, 4 seconds REVOLVING orbiting the sun 365.256378 days. Day/Night.

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Cycles of the Sky

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  1. Cycles of the Sky Sun, Moon & Seasons

  2. EARTH IN MOTION • The Earth is not just “sitting” out in space, what is it doing? • ROTATING spinning counterclockwise on it’s axis 23 hours, 56 minutes, 4 seconds • REVOLVING orbiting the sun 365.256378 days

  3. Day/Night • Why does the Earth experience day and night? • Do other planets experience day and night? • Do other planets have 24 hour days like the Earth?

  4. Why don’t we always have 12 hours of daylight? • Look here!

  5. The annual motion of the sun • Due to the Earth’s revolution around the Sun, the Sun appears to move through the zodiacal constellations • The Sun’s apparent path on the sky is called the “ecliptic”

  6. The Motion of the Planets The planets are orbiting the sun almost exactly in the plane of the ecliptic. Jupiter Venus Mars Earth Mercury The moon is orbiting Earth in almost the same plane (ecliptic). Saturn

  7. Seasons • What causes the seasons?

  8. The reason for the seasons • REMEMBER– the different incidence angle of the sun’s rays is causing the seasons on the Earth

  9. Where is the sun in the sky in the summer?

  10. Where is the sun in the sky in the winter?

  11. Why does the sun’s path in the sky change? • Remember this?!

  12. Summer Solstice • Considered the 1st day of summer • North Pole is tilted more toward the Sun than any other day • Sun appears at its highest point in the sky • “longest day”= greatest amount of daylight hours • Why isn’t it the hottest day?

  13. Winter Solstice • Considered the 1st day of winter • North Pole is tilted farther away from the Sun than any other day • Sun appears at its lowestpoint in the sky • “shortest day”= leastamount of daylight hours • Why isn’t it the coldest day?

  14. Equinoxes • When Earth is neither tilted toward nor away from Sun • Sun appears at at its midpoint in the sky • Exactly 12 hours of daylight

  15. Brain Pop! Click here!

  16. The moon

  17. what is the moon doing out there? • REVOLVING around the Earth 27.321583 days • ROTATING? Yes it is!

  18. The same side of the moon is always facing the earth • The moon is rotating on its axis with the same period with which it is orbiting the Earth • The moon is “tidally locked” to the Earth

  19. Moon’s orbital period • Sidereal Month -the moon appears to move completely around the sky once in about 27.3 days as seen from Earth • Synodic Month -the moon takes 29.5 days to return to the same point in the sky as referenced by the Sun -this is because of the motion of the Earth around the Sun -lunar phases are correlated with the Synodic Month

  20. Phases of the moon • As the moon orbits around the Earth, we see different portions of the moon’s surface lit up by the Sun • This causes the phases of the moon

  21. Lunar Phases • Brain Pop!

  22. New Moon -> first quarter -> full moon • In the evening sky

  23. Full Moon -> third quarter -> new moon • In the morning sky

  24. Lunar Eclipse • When the Earth’s shadow passes over the full moon Earth’s shadow consists of an “umbra” and a “penumbra”

  25. Eclipses • Brain Pop!

  26. Lunar Eclipse • Penumbra • Zone of partial shadow • If the moon passes through the penumbra, it is a lunar eclipse • Umbra • Zone of full shadow • If the moon passes through the umbra, it is a total lunar eclipse

  27. Conditions for lunar eclipse • When the moon’s orbit crosses the ecliptic, we call this a “node” • A lunar eclipse can only occur if the moon passes a node near a full moon

  28. Total lunar eclipse • A total lunar eclipse can last up to 1hr 40min • Has a faint red glow, caused by the reflecting sunlight in Earth’s atmosphere

  29. Lunar eclipse • Typically 1 or 2 lunar eclipses per year • Total lunar eclipse on Dec. 10, 2011, best seen in Western US • Next total lunar eclipse not until 2014!

  30. Solar eclipse • Happens when the Moon covers up the Sun

  31. Conditions for a solar eclipse • A solar eclipse can only occur if the moon passes a node near a new moon • Approximately 1 solar eclipse per year

  32. Solar eclipse

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