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Sun-Earth-Moon System

Sun-Earth-Moon System. Section 27.2: Moon Surface. Albedo : amt of sunlight reflected off a surface Moon’s low albedo =7% Earth’s albedo is higher=31% Impact craters : objects that hit moon’s surface Highlands : light in color, mountainous Maria : dark, smooth, lava filled features

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Sun-Earth-Moon System

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  1. Sun-Earth-Moon System

  2. Section 27.2: Moon Surface • Albedo: amt of sunlight reflected off a surface • Moon’s low albedo=7% • Earth’s albedo is higher=31% • Impact craters: objects that hit moon’s surface • Highlands: light in color, mountainous • Maria: dark, smooth, lava filled features • Ejecta: stuff evacuated from impact, falls to surface • Rays: long trails of ejecta • Rilles: collapsed lava tubes [like a hose with no H2O flowing] • Regolith: loose, ground-up moon rock

  3. The Moon’s features…

  4. Principle of Cross-Cutting • Principle of Cross-cutting • relationships • -older cross is cut by younger; the one cutting is younger than the one being cut • Rock A (cutting) is younger than Rock B (being cut) • Cross-Cutting w/s

  5. Moon Structure • Seismometers measure annual moonquakes • Moon not tectonically active, no erosion • Crust thinner on Earth side • Solid upper mantle • Partially melted lower mantle • Solid iron core • Impact theory: supported by similarities btw E and M rocks (Made of silicates), age of rocks 3.8-4.6 billion years -Theories of Moon’s formation w/s

  6. Impact Theory

  7. Section 27.3: S-E-M system • Elliptical orbit: planets & moon revolve on a slightly squished circle • Ecliptic plane: path planets travel around Sun • Apogee=furthest (away) • Perigee=closest • Earth: • 24 hr rotation • 365 day revolution • tilt on axis 23.5° • Day/night =rotation of Earth on own axis • FOLLOW SOLAR DAY FOR TIMEKEEPING

  8. Time Measured Based on Sun • The day is measured using the Sun. • Local Solar Noon • Occurs when the Sun is on your meridian. • Mean Solar Day • The time between successive ‘Noons’. • When noon occurs depends on your longitude: • Person 15° east of you sees noon 1 hour earlier. • Person 15° west of you sees noon 1 hour later.

  9. Months, Weeks, & Days?? • The year is also divided into 12 months. Why 12? • There are 12.4 lunar synodic periods (cycles of phases) during a year. • The word for Month derives from the word for the Moon. • Months are divided into Weeks: • The week is traditionally divided into 7 days; Seven for the 7 planets/moving bodies visible to the naked eye (Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn)

  10. Tilt Causes Seasons • Spring & Fall Equinox: • Equal radiation in both hemispheres • Axis perp. to rays • Sun directly over equator • Winter Solstice: • N hemi tilted away Sun • less direct radiation • Summer Solstice: • N hemi tilted to Sun • more direct radiation

  11. Moon’s Phases • Waxing: light increasing • Waning(whiningbad): light decreasing • Crescent: less than half lit (crescent roll) • Gibbous: more than half lit • Quarter: half lit

  12. Moon Motions • Synchronous rotation: rate of orbit and rotation equal…see same side of moon • Sidereal month: 360° orbit of M around E, 27.3d • Lunar month: new moon to new moon, 29.5 d • Moonrise 50 min later each day b/c E has to turn an additional 13° • Moon’s orbit creates tides…GRAVITATIONAL PULL OF MOON ON EARTH • Modeling Moon’s Motions Activity

  13. Spring/Neap Tides: 2 each month Tides: Locally 2 high, 2 low per day Spring tides: (straight) higher highs & lower lows SunMoonEarth are aligned Full moon or new moon Neap tides: (ninety degree angle) Tides less dramatic-weaker Quarter moons Sun/Moon cancel out/< they’re @ Since the water is always moving, the Earth cannot hold onto it, and the moon is able to pull at it. The ocean is constantly moving from high tide to low tide, and then back to high tide. There is about 12 hours and 25 minutes between the two high tides. (Locally 2 high, 2 low per day)

  14. Solar Eclipse [SunMoonEarth]order • Moon blocks Sun from our view • Total: entirely blocked • Partial: portion blocked • Penumbra: shadowy region cast by moon • Umbra: darkest shadow cast by moon, cone-shaped • See pg. 783: moon’s ecliptic plane

  15. Lunar Eclipse [SunEarthMoon] • Moon passes through Earth’s shadow • Umbra: darkest shadow behind Earth…ultra dark • Penumbra: shadowy area cast behind Earth…partly • Total lunar eclipse: entire M in E’s shadow • Partial lunar eclipse: partial shadow of E on M

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