Unit 10 Space 2

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Unit 10 Space 2

• EarthMoon System
• Moons Rotation and Revolution
• Phases of the Moon
• Solar Eclipses
• Lunar Eclipses
• Moon Origin Theory
• Ocean Tides and the Moon

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TAKS Practice Space 2

• About how long does it take the Moon to complete
  the cycle shown above?(a) 1 day (b) 1 month
  (c) 1 year
• Which phase of the Moon shown above does not
  reflect any sunlight towards Earth? (a) 1
  (b) 2 (c) 3 (d) 4
• At which phase could a solar eclipse occur?(a) 1
  (b) 2 (c) 3 (d) 4

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TAKS Practice Space 2

• About how long does it take the Moon to complete
  the cycle shown above?(a) 1 day (b) 1 month
  (c) 1 year
• Which phase of the Moon shown above does not
  reflect any sunlight towards Earth? (a) 1
  (b) 2 (c) 3 (d) 4
• At which phase could a solar eclipse occur?(a) 1
  (b) 2 (c) 3 (d) 4

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TAKS Practice Space 2

• About how long does it take the Moon to complete
  the cycle shown above?(a) 1 day (b) 1 month
  (c) 1 year
• Which phase of the Moon shown above does not
  reflect any sunlight towards Earth? (a) 1
  (b) 2 (c) 3 (d) 4
• At which phase could a solar eclipse occur?(a) 1
  (b) 2 (c) 3 (d) 4

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TAKS Practice Space 2

• About how long does it take the Moon to complete
  the cycle shown above?(a) 1 day (b) 1 month
  (c) 1 year
• Which phase of the Moon shown above does not
  reflect any sunlight towards Earth? (a) 1
  (b) 2 (c) 3 (d) 4
• At which phase could a solar eclipse occur?(a) 1
  (b) 2 (c) 3 (d) 4

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Guiding Questions Space 2

• What are the rotation and revolution periods of
  the Moon? (p.646)
• What causes the Moon to shine? (p.647)
• What are the phases of the Moon? (pp.647-48)
• What causes solar eclipses? Where and how often
  do they occur? (p.649)
• What causes lunar eclipses? (pp.650)
• What is the current theory explaining the origin
  of the Moon? (p.653)
• What causes the ocean tides on Earth? (p.533)

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1. What are the rotation and revolution periods
of the Moon?

• The Moon has exactly the same periods of rotation
  (one spin on its axis) and revolution (one orbit
  around Earth), 27.3 days. This means that the
  same side of the Moon is always facing Earth.
• It is not a coincidence that the two periods are
  the same. The Moon developed a bulge facing the
  Earth when it first formed, because of the
  Earths strong gravitational pull, and that
  stronger pull on the side with the bulge locks
  that side into always facing Earth.

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1. Moon Rotation / Revolution (cont.)
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2. What causes the Moon to shine?

• The moon does not actually give off any light of
  its own. It simply reflects the light of the Sun
  which shines on it back to Earth. This is why
  the moon has different phases. If the sun is
  behind the Moon, as seen from Earth, none of the
  Moons face pointing towards Earth it lit by the
  Sun, and the Moon appears dark.

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3. What are the phases of the Moon?

• Moon phases are the sequence of different shapes
  that the Moons lighted face takes as it orbits
  around the Earth, as seen from Earth. The phase
  at any time of the cycle depends on the relative
  positions of the Earth, Sun and Moon.
• It takes 29.5 days for the Moon to complete all
  of the phases and return to the same shape. The
  difference between the period of rotation, 27.3
  days, and the Moon phase cycle of 29.5 days is
  the result of the Earths motion around the sun.
  It takes the Moon another 2.2 days to catch up
  with the Earths movement around the Sun.

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3. Moon Phases (cont.)

• A New Moon occurs when the Moon is between the
  Earth and the Sun, so that the lighted face of
  the Moon is facing away from the Earth, and the
  dark unlighted side is facing earth. The New
  Moon rises and sets with the Sun, and cannot be
  seen because it is dark.
• After the New Moon, the phases begin waxing.
  Waxing means that more of the lighted half of the
  Moon is seen each night. After 3.7 days, a thin
  crescent shaped sliver of the lighted Moon is
  visible. This is the Waxing Crescent phase.

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3. Moon Phases (cont.)

• About 7.3 days after the New Moon began the Moon
  phase cycle, about half of the Moon facing Earth
  is lit. This is the First Quarter Phase. This
  phase rises about noon and sets about midnight.
• About 11 days after the New Moon, about ¾ of the
  Moons face is lit (as seen from Earth). This is
  called the Waxing Gibbous phase.

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3. Moon Phases (cont.)

• About 14.75 days after the cycle began, the
  entire face of the Moon is lighted. This is the
  Full Moon phase. A Full Moon rises at about 6pm
  and sets around 6am, the opposite of the Sun.
• About 18.4 days after the cycle began, the Moon
  has entered the waning phases, becoming darker
  each day. The ¾ lit moon is called the Waning
  Gibbous phase.

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3. Moon Phases (cont.)

• About 22 days after the cycle began, about half
  of the Moon is lighted. This is the Third
  Quarter phase. A Third Quarter Moon rises at
  about midnight and sets around noon.
• About 25.7 days after the cycle began, a thin
  sliver of the lighted face is visible. This is
  called the Waning Crescent phase.
• At 29.5 days after the cycle began, another New
  Moon starts a new cycle.

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3. Moon Phases (cont.)
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4. What causes solar eclipses? Where and how
often do they occur?

• A Solar Eclipse occurs when the Moon moves
  directly between the Earth and the Sun, and casts
  its shadow over part of the Earth. Solar
  eclipses can either be total (the entire sun is
  blocked), partial (only part of the Sun blocked)
  or annular (the middle is blocked, leaving a ring
  of light).

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4. Solar Eclipses (cont.)

• As seen from this location, the entire event
  takes about 2 hours. The Sun is only completely
  eclipsed for about 1 minute, and then slowly
  uncovered over an hour. This is a time lapse
  multiple exposure photo showing the entire 2002
  solar eclipse in Africa.

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4. Solar Eclipses (cont.)

• Only a narrow band of Earth experiences a total
  eclipse at any one event (in the Umbra), but a
  large area on either side of the total eclipse
  band sees a partial solar eclipse (in the
  Penumbra), where only part of the Sun is
  blocked.

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4. Solar Eclipses (cont.)

• The darkest shadow, where the total eclipse
  occurs, is called the umbra. The lighter shadow,
  where only a partial eclipse occurs, is called
  the penumbra.

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4. Solar Eclipses (cont.)

• Eclipses follow a 18 year, 11.3 day cycle called
  the Saros Cycle. This map shows the current
  cycle.

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5. What causes lunar eclipses?

• When the Earths shadow falls on the Moon, a
  lunar eclipse occurs. Lunar eclipses can be total
  or partial. During a total lunar eclipse, light
  reflected off of Earth makes the Moon turn red
  when direct sunlight to the Moon is blocked.

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5. Lunar Eclipses (cont.)

• The much larger umbra cast by Earth allows the
  entire night hemisphere of Earth to see a total
  lunar eclipse, provided the sky is clear.

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6. What is the current theory explaining the
origin of the Moon?

• Prior to the Apollo space missions, there had
  been three different theories about the Moons
  origin the capture theory, the condensing
  theory, and the ejection theory. The Apollo
  missions uncovered evidence of a fourth theory,
  now most widely accepted, called the Impact
  Theory. Under this theory, a Mars-sized object
  collided with Earth, and caused a large part of
  Earth to be ejected into orbit around Earth,
  where it reformed into the Moon.

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6. Lunar Origin Theory (cont.)
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7. What causes the ocean tides on Earth?

• Tides are caused by gravitational attraction
  between the Earth, Moon, and Sun. The Moon
  exerts a stronger pull on Earth than does the
  Sun. Water in the oceans bulges toward the Moon,
  and thus causes a high tide on the sides of Earth
  facing towards and away from the Moon.
• When the Moon and Sun are on opposite sides of
  Earth from one another, the tides are highest.
  These are called Spring Tides.
• Neap Tides occur when the Sun and Moon are at
  right angles to one another. They are lower.

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7. Ocean Tides (cont.)