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Climate and Latitude

Climate and Latitude. Sun’s rays spread over large area = cooler concentrate in small area = warmer Warmest where sun directly overhead (at noon). cooler. warmer. cooler. Seasons. What do we observe? Warm in Summer ; Cold in Winter Yearly cycle

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Climate and Latitude

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  1. Climate and Latitude • Sun’s rays • spread over large area = cooler • concentrate in small area = warmer • Warmest where sun directly overhead (at noon) cooler warmer cooler

  2. Seasons • What do we observe? • Warm in Summer; Cold in Winter • Yearly cycle • Linked to Sun’s location on ecliptic(Spring = Vernal Equinox, Summer = Summer Solstice; etc) • Sun is heat source • Seasons in N and S hemispheres opposite • N summer = S winter • Seasons near Equator less severe

  3. Cause of Seasons No! • Changing distance to Sun? • Orbit is ellipse; distance changes • Good idea, BUT • Orbit almost circular • Trivial change in distance • little change in heating • Closest to sun in January • Predicts summer in January • Both N and S hemispheres at same distance • Predicts seasons same in N and S hemispheres

  4. Zenith Zenith Horizon Horizon Cause of Seasons Yes • Tilt of Earth’s Axis? • Location where sun overhead (at noon) • Vernal & Autumnal Equinoxes (Mar 21, Sept 21) • Overhead at Equator • Summer Solstice (Jun 21) • Overhead on Tropic of Cancer (23.5º N) • Warmer in N hemisphere; cooler in S hemisphere • Winter Solstice (Dec 21) • Overhead on Tropic of Capricorn (23.5º S) • Warmer in S hemisphere; cooler in N hemisphere cooler warmer cooler

  5. Cause of Seasons - Part 2 Yes • Tilt of Earth’s Axis? • Path of Sun in sky • Summer Solstice (Jun 21) • Sun farthest north • Transits high at noon • Days are long • Winter Solstice (Dec 21) • Sun farthest south • Transits low at noon • Days are short Large amount of heating Small amount of heating

  6. For an observer in the continental U.S., which, if any, of the x’s (a – e) in the figure below correctly shows the position of the Sun’s shadow at noon? Note that the position of the Sun’s shadow at noon on the Winter and Summer Solstices are shown. a) a b) b c) c d) d e) e

  7. Motions and Phases of the Moon Composite Image Credit: T.A. Rector, I.P. Dell'Antonio, NOAO, AURA, NSF

  8. Motion of Moon • Daily Motion Like Stars • Rise in East; Transit in South; Set in West • Moon Orbits Earth • Moon slips on Celestial Sphere • 13 degrees per day = 1 lunar diameter per hour • Sidereal Period = Orbital Period • 27.3 days • Time from full moon to full moon • 29.5 days (similar to sidereal day vs. solar day) • Moon rises roughly 50 min later each day

  9. Rotation of Moon • Always see same side • Moon rotates once per month Non-rotating moon Rotating moon

  10. crescent Moon Phases Waxing 1st quarter • New = all black • Full = all white • Crescent < half white • Gibbous > half white • Quarter = half white • Waxing = growing • Waning = shrinking gibbous full gibbous 3rd quarter Waning D --> O --> C crescent

  11. Phases of Moon

  12. Phases of Moon • Not caused by Earth’s shadow! • Cause: • Changing view of illuminated side (as Moon orbits Earth) • “Back Side” sometimes called “Dark Side” • Back side not dark • Back side has night and day (just like front side)

  13. Workbook Exercise: Cause of Moon Phases (pages 23-25 in workbook)

  14. During the full moon phase, how much of the Moon’s surface is being illuminated by sunlight? • a) none • b) less than half • c) half • d) more than half • e) all

  15. Workbook Exercise: Predicting Moon Phases (pages 27-28 in workbook)

  16. Which phase of the Moon rises at noon? • a) Waning gibbous • b) Third quarter • c) First quarter • d) Waxing crescent • e) None of the above

  17. Solar & Lunar Eclipses

  18. Eclipses • Solar • Moon’s shadow falls on Earth • Lunar • Moon moves into Earth’s shadow

  19. Earth and Moon Shadows • Umbra • (and C) Penumbra • Umbral Extension

  20. Earth and Moon Shadows Appearance of Sun Observer location D A B C Type of Eclipse Total Partial Annular

  21. Solar Eclipse

  22. Lunar Eclipse

  23. When the Moon appears to completely cover the Sun (a solar eclipse), the Moon must be at which phase? • a) full • b) new • c) first quarter • d) last quarter

  24. When the Moon moves through the Earth’s shadow, causing it to appear to darken (a lunar eclipse), the Moon must be at which phase? • a) full • b) new • c) first quarter • d) last quarter

  25. Motion of the Planets • Diurnal motion like fixed stars • Rise in “east” • Transit “high/low in south” • Set in “west” • Position on celestial sphere slowly “slips” from day to day (similar to sun and moon)

  26. Planet Motion W E • Generally move from W to E • Retrograde motion - time when planet appears to move backwards from E to W

  27. Planets • Planet = Greek for “wanderer” • 5 visible planets (others too faint) • Mercury, Venus, Mars, Jupiter, Saturn • Total of 7 wandering objects (including Sun and Moon)

  28. Planet Location • Planets always found in Zodiac • 18º wide belt centered on ecliptic • Mercury and Venus always close to sun • Mars, Jupiter, Saturn seen everywhere (in Zodiac) • Sometimes near sun (conjunction) • Sometimes opposite to sun (opposition)

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