The MOON. General Stats: ¼ the size of Earth 1/6 the gravitational pull of Earth (180 lbs = 30 lbs) Gravitational pull too weak to hold atmosphere Extreme.

The MOON

General Stats:

•¼ the size of Earth

•1/6 the gravitational pull of Earth (180 lbs = 30 lbs)

•Gravitational pull too weak to hold atmosphere

•Extreme temperature changes (253°F to -387°F)

•Slightly elliptical orbit with 5 degree incline to Earth’s ecliptic

•240,000 miles from Earth

•Rotation & Revolution periods: 27 1/3 days

Scale Diagram

Surface Features:

•83% covered by impact craters and highlands of all sizes

•Crater: bowl shaped depression resulting from collisions with interplanetary debris

•Highlands: light areas on the moon that are elevated several kilometers

•Rays: bright streaks of shattered rock and dust that radiate from a number of craters

•Regolith: moon dust or soil that was created by impact of debris turning rock to dust or sand

Features Continued:

•Maria: (mare, singular) dark areas “seas” that are not rilled with water.

•Very smooth volcanic plains that filled with lava billions of years ago

•Cover 17% of surface

•When eruptions ended moon became dead

•Rill: ditch on the moon’s surface where molten lave flowed in the past

•Rilles: long deep clefts or cracks running through the moon’s maria bedrock

Origin:

1) Sister Theory: formed as a separate object near the earth in a similar way

• Problem: moon different in density & composition, difficult to have originated from same planetary blob

2) Capture Theory: formed far from earth and was later captured by it

• Problem: moon’s capture would be difficult & unreasonable

3) Daughter or Fission Theory: originated out of the earth itself

• Problem: computer simulations indicate ejection of moon into stable orbit would not occur

4) Impact Theory: collision by large, Mars-sized object with youthful molten earth – dislodged matter from earth and assembled into the moon

Lunar Phases:

•Depends on angle the sun’s rays his the moon, not shadow of Earth

•Apogee: position of the moon farthest from Earth

•Perigee: position of moon closest to Earth

•Rotation:

•Sidereal (relative to stars) 27.3217 days

•Full moon to full moon: 29.5306

•Rises and sets 50 minutes later each day

•Moves 12° along orbit each day

•Revolution 27 1/3 days…same side always faces us

Moon Misconceptions

“Dark Side” of the moon:

Should really be called the Far Side of the moon.

During our New Moon phase, the Far side of the moon is fully illuminated

Near Far

Lunar Lunacy:

Full moon causes crazy behavior, increased child births, and other folklore.

Scientific studies have been done and no correlation has been found

Tides

Daily rise and fall of the ocean waters caused by the gravitational pull of the moon and the sun

Why do they change?

•Earth turns on its axis (rotates) and moon revolves around Earth

•Movements above cause the tides to change every 6 hours, 12 minutes, 30 seconds

•Like the moon – tides rise (come in) 50 minutes later each day

Newton – gravity is stronger between 2 objects when they are closer together

• Water on the side of Earth nearest the moon is pulled by the moon more strongly causes a bulge direct high tide

• At same time, Earth is being pulled away from the water on the far side of the Earth, leaving a bulge of water behind indirect high tide

•Low tides: areas between the 2 high tides

Sun Effects on Waters:

Only ½ as much as the moon

Can strengthen or weaken the moons effect

Spring Tides: sun, moon, & earth all aligned sun’s effect is added to the moons

•Occurs at new and full moon phases

•Higher than normal tides

Neap Tides: sun is 90 degrees away from moon its effect is subtracted from moons

•Occurs at quarter phases

•Lower than normal tides

Tidal Range

•Greatly affected by shape of coastal contours

•Average differences between high and low tides is 3 – 6 feet

•Bay of Fundy, Canada – greatest difference = 56 feet; bay is “v” shaped so water funnels in

Hopewell Rocks in Bay of Fundy National Park…difference between high and low tide here is 45 feet!