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Chapter 30
Moon and Rings
Section 30.1 The Earth’s Moon

A body that orbits another larger body is
called a satellite.

There are man made and artificial
satellites.

Sputnik is the first man made satellite.

What is an example of a natural satellite?
Section 30.1 The Earth’s Moon

Which is bigger the Earth or the moon?

So, which will have a greater gravity?
Section 30.1 The Earth’s Moon

The moon actually has 1/6th the gravity of
the earth.

So if you weighed 200 pounds on Earth
you would only weigh ~33 pounds on the
moon.

Video in the News: Apollo 11 Anniversary - 1st Moonwalk
Section 30.1 The Earth’s Moon

The lower gravity does NOT allow gases
to be held in as an atmosphere.

Therefore life can NOT exist.
Section 30.1 The Earth’s Moon

How often does the Earth make one
rotation on its axis?

The moon revolves on its axis once
every 29.5 days.

This causes huge temperature
variations.
Section 30.1 The Earth’s Moon

The closest natural object to the Earth is the
moon.

The surface of the moon is easily visible.

It can be seen that there are light and dark
spots.

What do you think these light and dark spots are?
Section 30.1 The Earth’s Moon

The light spots are rough highlands
composed of lighter colored rock.

The dark spots are called maria which
are smooth areas of dark solidified lava.

There are long deep channels that the lava
flowed through called rilles running
throughout the maria.
Section 30.1 The Earth’s Moon

The moon is covered with bowl shaped
depressions called craters.

What caused these craters to form?
Section 30.1 The Earth’s Moon

The debris that was blown out of the
crater settled in streaks called rays.
Section 30.1 The Earth’s Moon

The surface of the moon is covered with
dust and small fragments of rock that were
pulverized by collisions.

This material is called regolith
Section 30.1 The Earth’s Moon

The lunar surface has rocks in the
highlands that are light colored are called
anorthosites.
Section 30.1 The Earth’s Moon

Information on the interior of the moon
is collected by seismographs placed by
the Apollo astronauts.

What is a seismograph?
Section 30.1 The Earth’s Moon

The moon is made up of
three layers.
1. The core
2. The lower mantle
3. The upper mantle
4. The crust
Section 30.1 The Earth’s Moon

How do you think the earth formed?
Section 30.1 The Earth’s Moon

It is theorized that the moon formed in stages:
Stage 1: A cosmic collision caused by a Mars sized
planet colliding with the Earth.
Stage 2: The moon was covered by an ocean of molten
rock of which the denser material settled to the
center (the core).
Stage 3: The moon began to cool.
Section 30.2 Movements of the
Moon

An observer on Earth would see the
moon as orbiting the Earth.

An observer in outer space would see
the Earth and moon orbiting each other.

Which do you think is true?
Section 30.2 Movements of the
Moon

The latter is true, the center of the
“Earths” orbit (the Sun) is actually the
center of the Earth/moon orbit.

The moon is only 1/80 the mass of the
Earth.

The balance point of this co-revolution is
some where in the Earth’s interior.
Section 30.2 Movements of the
Moon

The moon and Earth form an ellipse
(just like the planets around the Sun).

When the moon is farthest from the Sun
it is at apogee, and when it is closest it
is at perigee.
Section 30.2 Movements of the
Moon

The moon also spins very slowly on its
own axis, one revolution is 27.3 days
which is the same amount of time it takes
the moon to revolve around the Earth.
Section 30.2 Movements of the
Moon

An eclipse is the point when one
planetary body passes through the
shadow of another.
Section 30.2 Movements of the
Moon
The shadow of the Earth has two parts:


The umbra is the inner cone shaped portion
where all of the sun’s light is blocked

The penumbra is the outer portion where
sunlight is partially blocked.
Section 30.2 Movements of the
Moon

When the moon passes between the
Earth and the Sun the moon may fall
upon the Earth causing a solar eclipse.

People within the umbra witness a full
solar eclipse.

People within the penumbra witness a
partial solar eclipse.
Section 30.2 Movements of the
Moon

A lunar eclipse occurs when the moon
is positioned between the earth and the
sun.

For a full lunar eclipse to occur the
moon must pass completely into the
Earths umbra.
Section 30.2 Movements of the
Moon

How an Eclipse Works

Solar Eclipse

Lunar Eclipse
Section 30.3 The Lunar Cycle

The moon is seen as different shapes at
different times of the month, these
varying shapes are called phases.

Moon Phases
Section 30.3 The Lunar Cycle

The phase when there is no visible moon is called the
new moon.

When the size of the moon is increasing it is called the
waxing moon.

When the moon reaches its apex it is known as the full
moon.

When the size of the moon is decreasing it is called
the waning moon
Section 30.3 The Lunar Cycle

In both waxing and waning stages the
moon has many different shapes
including:

crescent or the sliver shaped moon

quarter or when the moon is quarter full

gibbous or when the moon is larger then a
quarter.
Section 30.3 The Lunar Cycle

During the crescent phase there is only a
small portion of the moon shining brightly
and the rest has a dim shine do to light
reflecting off the Earth, earthshine.
Section 30.3 The Lunar Cycle

Systems used to measure the passage
of time are called calendars, with basic
units being days, months and years.

There are two main types of calendars:


Julian
Gregorian
Section 30.3 The Lunar Cycle
The Julian calendar developed by the
astronomers of Julius Caesar, it
consisted of twelve months with eleven
having 30 to 31 days and February had
29.


Every four years there was a leap year but
this calendar came out to be 11 minutes
longer than the solar year.
Section 30.3 The Lunar Cycle

The Gregorian calendar is the calendar
currently used by most of the world.

The major difference is there are three less
days every 400 years, this makes the
calendar only 29 seconds off from the solar
year.
Section 30.4 Satellites of Other
Planets

Until the 1600’s
astronomers
thought that the
Earth was the only
planet with a
moon.
Section 30.4 Satellites of Other
Planets
The Moons of Other Planets

Mars has two moons: Deimos and
Phobos.


They differ from Earths moon in that they
are extremely small and have an irregular
shape.
Section 30.4 Satellites of Other
Planets
Jupiter has 67 moons and a ring of gas
and dust which are all considered
satellites.


All but four of Jupiter’s moons are 400 km
or smaller.

The four larger moons are called Gallilean
moons because they were discovered by
Gallileo.
Section 30.4 Satellites of Other
Planets
Saturn has thick bright rings of gas and dust
that are its most noticeable feature as well as
20 moons.


Most of Saturn’s moons are small chunks of icy
rock but four of its moons are extremely large.

The largest is called Titan, it has a thick nitrogen
atmosphere which is so thick the surface of the
moon is obscured from view.
Section 30.4 Satellites of Other
Planets

Uranus and Neptune both have a
number of moons each but the planets
are so distant into the solar system that
little is known about them and it is not
even known if that is all there are.