Chapter 28 Minor Bodies of the Solar System The Moon

The moon is a natural satellite A satellite is a natural or artificial body that revolves around a celestial object Sputnik, was launched by the Soviet Union the month I was born! It was the first artificial satellite

Apollo program 1969-1972 6 spacecraft to the moon

July 20, 1969 Neil Armstrong set foot on the moon. Do you know what he said? That’s one small step for man, one giant leap for mankind.

Moon gravity The moon has much less mass so has much less gravity A person weighs 1/6th the amount he weighs on Earth

Lunar surface Lunar comes from the Latin word luna moon Light and dark patches visible Light—anorthosites Dark—maria—seas of solidified lava formed from massive meteoroid bombardment

Regolith The surface of the moon is covered with a fine dust called regolith 2 causes: Meteor bombardment Thermal shock—expansion and contraction caused by lack of an atmosphere

One side of the moon always faces Earth The pull of the Earth’s gravity during formation caused the crust on the far side to become thicker Near side lunar crust is 60km thick Far side up to 100 km thick

One Side of the Moon There is no DARK SIDE We always see the same side because the Moon’s rotational rate matches the rate at which it revolves around the Earth. Rotates (and revolves) once every 27.3 days. Gravity lock between the Earth and the Moon There is no DARK SIDE

So why is a lunar cycle 29.5 days? While the moon is revolving around the Earth, Earth and the Moon are also revolving around the sun It takes time to catch up to Earth’s movement

Barycenter The Earth and the moon actually revolve around each other. Their common center of mass is called the barycenter It is located within the Earth

READ PGS 725 & 732

Layered Crust Mantle Maybe a small iron core (layered) No magnetic field

Tides Because of the pull from the moon’s gravity on Earth's water, the water forms a bulge on the moon-ward side. This is high tide.

The position of the moon determines the type of tide

Formation of the Moon The Giant Impact Hypothesis Formerly several main hypotheses Now . . . The Giant Impact Hypothesis A Mars-sized body hit the Earth while it was still quite hot The collision ejected chucks of mantle into orbit around Earth This came together to form the moon

Other Theories of the Moon’s formation Simultaneous creation Fission Capture Collision

Simultaneous creation Formed at the same time from same stuff Problem: Earth has 3 X's more iron

Fission George Darwin, son of Charles, hypothesized that the Moon and Earth were originally one body. As it revolved and rotated it cooled and began to rotate faster A giant bubble of still molten material pulled away and escaped

Capture Formed elsewhere in the solar system and was caught as it traveled by the Earth

Collision Young Earth was hit by an asteroid that knocked off a chunk and then the asteroid and chunk were caught in the gravitational field.

One Side of the Moon There is no DARK SIDE We always see the same side because the Moon’s rotational rate matches the rate at which it revolves around the Earth. Rotates (and revolves) once every 27 days. Gravity lock between the Earth and the Moon There is no DARK SIDE

Misc Factoids Diameter about the size from San Francisco to New York City 1996 discovered ice deposits at the poles

Phases of the Moon At any given moment rays of sunlight illuminate one half of the Moon's surface. Because the moon rotates and revolves around earth we see phases--changes in shape that occur every month.

Study this picture page730!!!!!!!

Imagine you are on Earth What do you see? Imagine you are on Earth

New moon-- occurs when the Sun, moon and Earth are lined up The new moon is the side we cannot see

Full moon-- we see the side that is lit up

Waxing-- getting bigger right side lit up

Waning-- getting smaller left side lit up

Crescent-- Crescent roll shape Crescent roll shape

Half moon—1st quarter

Gibbous-- More than half is lit up Funny name for a funny shape

We put these words together to describe the moon. Full moon New moon Waxing gibbous Waning crescent

Phase Game SUNLIGHT Dusk Midnight Noon Dawn Earth Full Moon 1st QTR Waxing Gibbous Waxing Crescent New Moon Waning Gibbous 3rd QTR Waning Crescent Earth Dusk Midnight Noon Dawn

Eclipses The Sun is 400 times larger than the Moon in diameter, it is also 400 times farther away. So, the sun and Moon appear the same size in the sky. This allows us to have eclipses.

Moon is between the sun and earth Solar Eclipse Only seen by a small area of Earth

Solar eclipse Moon's shadow falls on the Earth

Only a few people under the path Who gets to see them??? Only a few people under the path

The shadow has two parts, the umbra and penumbra Umbra--darker, inner shadow Penumbra– lighter, outer shadow

Lunar eclipse Earth's shadow falls on the moon

Why are eclipses so rare? 5.2 tilt of the moon orbital plane The Earth and Moon have different orbital planes