The Moon

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The Moon
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The Moon Questions

• What is the size difference between the Earth and
  Moon?
• How long does it take for the Moon to orbit the
  Earth?
• What is the difference between a sidereal and a
  synodic (or lunar) month?
• Is the Moon visible during the day?
• What is the difference between the dark side and
  the far side of the Moon?
• What are the eight phases of the Moon?
• What is the difference between waxing and waning?
• What is the difference between a lunar eclipse
  and a solar eclipse?
• When do eclipses occur?
• What is the composition of the Moon?
• How did the Moon form?

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Size Comparison Activity
The average distance between Earth and Moon is
approximately 30 times Earth's diameter. The
Moon is 27 of the Earths diameter. Sun is 700
cm in diameter if Earth is 6.5 cm and Moon is 2
cm
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I know the Moon revolves around the Earthbut
does it rotate?
Yes!

• The moon makes one full rotation each time it
  revolves around the Earth. (Think of it as a
  quarter turn for every 90 degrees it travels
  around the Earth).
• The moon revolves and rotates 13.19 degrees per
  day (on average).
• This means that one day for the Moon is the same
  as one year for the Moon.

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Do we always see the same side of the Moon?
Yes!

• Because the rotation of the Moon matches its
  revolution (or orbital period), it is in
  synchronous motion with the Earth.
• Its tidal bulge is always pointing towards the
  Earth, so this side (the near side) is always
  facing the Earth.
• This also means that there is a far side of the
  Moon that we never see on Earth.

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During one full lunar cycle, is there any side of
the moon that does not see the Sun?
No!

• All sides of the Moon face the Sun at some part
  of the lunar cycle.
• One half of the Moon is always illuminated by the
  Sun.
• We see varying amounts of sunlight on the side
  that always faces the Earth.
• Thus, the dark side of the Moon is the side that
  is not currently reflecting the Suns light.

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Dark Side vs. Back Side vs. Near Side of the Moon

• Far side of the Moon The side of the moon that
  we never see.
• Dark side of the Moon The side that is not
  presently illuminated by the Sun.
• Near side of the Moon The side of the Moon that
  we see as its face.

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Seeing the Moon

• During the night the moon appears to move from
  east to west along with the stars.
• In actuality, the Moon moves from west to east.
• Suppose you see the moon rise at 900 pm on one
  night.
• Since the moon moves 13.19 degrees per day, and
  it takes the an extra 52 minutes to catch up, you
  will need to view the Moon at 952 pm the
  following night to see rise again.

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Sidereal vs. Synodic Month

• A sidereal month is the time it takes the Moon to
  make one full revolution around the Earth (360
  degrees). 27.3 days.
• A synodic or lunar month is the time it takes the
  moon to complete one full cycle of phases. 29.5
  days.

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A synodic or lunar month is the time it takes for
the Moon to orbit the Earth with respect to the
Sun and is 29.5 days long. A sidereal month is
the time it takes for the Moon to orbit the Earth
with respect to the stars and is 27.3 days long.
The two times are different because the Earth
moves in its orbit around the Sun as the Moon
moves in its orbit around the Earth.
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Another familiar cycle is the lunar cycle. When
the Moon orbits the Earth, the amount of the side
facing the Earth that is lit changes, creating
the Moons phases. This phase cycle is called
the synodic or lunar and is 29½ days long.
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Apogee vs. Perigee
faster
Moon
slower
http//www.hermit.org/eclipse/why_months.html
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One common misconception is that the Moon is only
visible at night. However, the time of day in
which the Moon is in our sky varies depending on
its phase. This picture clearly displays the
Moon, visible during the day.
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The Moons orbital path is tilted about 5 degrees
off the ecliptic (the Earths orbital path)
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Some Facts about the Moon

• The Moon revolves around the Earth approximately
  12 times per year or approximately once every 30
  days.
• This is a relatively rapid rate compared to the
  stars.
• The Moons orbit stays near the Suns apparent
  path along the ecliptic.
• ½ the lunar month the Moon is north of the
  ecliptic, the other ½ it is south.
• The Moon crosses the ecliptic at two points
  called nodes.
• Each quarter moon takes about 7 days.

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Eclipses
Lunar vs. Solar Eclipses
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Eclipses cause shadows The Moon may enter the
shadow of the Earth or the shadow of the Earth
may reach the Moon.
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Eclipse Defined

• The blocking of part or all of the light either
  directly from the Sun (Solar eclipse) or sunlight
  to be reflected off the Moon (Lunar eclipse).
• Eclipses occur when the line along which the
  plane of the Moons orbit intersects the plane of
  the ecliptic (called the line of nodes).
• Eclipses only occur at new moon (
  eclipse) or full moon ( eclipse).

solar
lunar
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Eclipses do not occur during every full or new
moon because the Moons orbit is tilted by 5?
with respect to the Earth-Sun (ecliptic) plane.
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THE THREE TYPES OF LUNAR ECLIPSES
PENUMBRAL the Moon appears dimmed. PARTIAL
part of the Moon enters the umbra of the Earths
shadow and is darkened. TOTAL all of the Moon
enters the Earths shadow and becomes a reddish
color, only lit from light bending around the
Earths atmosphere.
Penumbra part of the shadow where Earth block
only part of the sunlignt
Umbra part of the shadow where Earth blocks all
sunlight.
During a total lunar eclipse, the Moon moves in
and out of the umbra of the Earths shadow.
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The Moons surface also has large, dark gray
plains called maria. Since these regions have
few impact craters, the lunar surface here is
relatively young compared with the lighter
surrounding terrain.
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Composition of the Moon

• Surface igneous rocks and thin blanket of
  pulverized, powdered rock fragments called
  regolith.
• Igneous rocks
• Moon Dust (regolith)
• Basalt (maria)
• Anorthosite (highlands)
• impact breccias (meteorite impacts)

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SOLAR ECLIPSES occur when the moons shadow
reaches the earth.
Unlike lunar eclipses, solar eclipses occur at
specific places on the Earth, indicated by the
arrow.
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Lunar Rocks from Different Regions
MARE BASALT contains many holes, suggesting that
gas was dissolved in the lava and solidified to
create this rock.
ANORTHOSITE from the highlands is an ancient rock
believed to be part of the Moons original crust.
IMPACT BRECCIAS are created from debris fused
together under high temperature and pressure
created by impacts of space debris with the lunar
surface.
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Missions to the Moon have revealed much about its
history.
The Moons surface is covered with a layer of
powdered rock called regolith.
An enormous boulder fractured while sliding down
a mountain
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Seismic experiments revealed that the main
regions of the Moons interior mimic those of the
Earth, but in different proportions.
Water ice may exist in the polar craters, where
the energy received from the Sun is insufficient
to melt it.
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The Moons Highlands
Oldest feature on the Moon
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• If you are located where the umbra of the Moons
  shadow reaches, you will see a total solar
  eclipse, during which the entire disk of the Sun
  is covered by the Moon, revealing the faint solar
  corona surrounding the Sun.
• Those just outside of this region where the
  penumbra of the Moons shadow reaches will only
  see a partial solar eclipse, during which only
  part of the disk of the Sun is covered by the
  Moon.
• Sometimes eclipses occur when the Moon is too far
  away from the Earth to completely cover the Sun
  in our sky. When this occurs, the Moon appears
  in the center and a thin ring, or annulus, of
  light surrounds it. These are called annular
  eclipses.

TOTAL ECLIPSE
ANNULAR ECLIPSE
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Close examination of moon rocks reveal tiny
microcraters less than one millimeter in
diameter.
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The most obvious feature on the Moons surface
are its many craters. Most of the Moons craters
are round, implying that they were formed from
impacts by high-speed meteoroids. Craters
include features such as central peaks, collapsed
terrace walls, and ejecta blankets.
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The three main surface features of the Moon
highlands
maria
Terminator
crater
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