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 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

The Moon’s features…

Principle of Cross-Cutting

• Rock A (cutting) is younger than Rock B (being cut)

•Cross-Cutting w/s

• Principle of Cross-cutting relationships

-older cross is cut by younger; the one cutting is younger than the one being cut

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 bysimilarities btw E and M rocks (Made of silicates), age of rocks3.8-4.6 billion years-Theories of Moon’s formation w/s

Impact Theory

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

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.

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)

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

Moon’s Phases

Waxing: light increasing

Waning(whiningbad): light decreasing Crescent: less than

half lit (crescent roll) Gibbous: more than

half lit Quarter: half lit

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

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)

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

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