Phases, Eclipses, and Tides

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Phases, Eclipses, and Tides

• Notes

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Lunar Motions

• Our moons name Luna
• The changing relative positions of the moon,
  Earth, and sun cause the phases of the moon,
  eclipses, and tides.
• Luna revolves around the Earth. It takes the moon
  about 27.3 days to revolve around Earth once.
• As Luna and Earth move, their positions change in
  relation to each other. Their positions also
  change in relation to the sun.

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Lunar Motion

• Our moon it tidally locked with Earth.
• This means that the moons day is the same as its
  year. It takes one month to rotate on its axis
  and one month to complete one revolution around
  Earth.
• Because of this, only one side of Luna faces
  Earth. The other side is ALWAYS facing away from
  Earth.
• There is no such thing as the dark side of the
  moon, but there is a far side.

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Lunar Phases

• The phase of the moon you see depends on how much
  of the sunlit side of the moon faces Earth.
• The moon does not give off its own light. The
  moon reflects light from the sun.
• Question How much of the moon is ALWAYS lit up
  by the light from the sun?
• Question 2 How much of every object in this
  solar system is ALWAYS lit up by the sun?

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Phases of the Moon

• The moon appears to have different shapes at
  different times. These different shapes of the
  moon that you see are called phases.

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Lunar Phases

• As the moon revolves around Earth, you see the
  moon from different angles. You cannot see all of
  the half of the moon that is lit by the sun.
• http//upload.wikimedia.org/wikipedia/commons/c/c0
  /Lunar_libration_with_phase2.gif

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Lunar Phases

• New Moon
• Waxing Crescent
• First Quarter
• Waxing Gibbous
• Full Moon
• Waning Gibbous
• Third Quarter
• Waning Crescent
• Waxing - Getting Bigger (wax on)
• Waning - Getting Smaller (wane off)
• Crescent - less than 1/4 visible
• Gibbous - more than 1/4 visible
• All 8 phases occur within about one months time.

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Eclipses

• Eclipse - to cover up
• When Lunas shadow hits Earth or Earths shadow
  hits Luna, an eclipse occurs. A solar eclipse
  occurs when the moon passes directly between
  Earth and Sol, blocking sunlight from Earth.
• An eclipse is when an object in space comes
  between the sun and another object.

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Eclipses

• Sometimes the moon moves between Earth and Sol.
  The moon blocks sunlight from reaching Earth
  (this means the moon is casting its shadow onto
  the surface of Earth). A solar eclipse occurs
  when an NEW MOON blocks your view of the sun.

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Eclipses

• A lunar eclipse occurs when Earth is between Luna
  and Sol.
• In a lunar eclipse, Earths shadow hits the moon.
• A lunar eclipse occurs when there is a FULL MOON.

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Eclipses

• So why is there not a solar and lunar eclipse
  each time we have a NEW MOON and FULL MOON?
• The moon does not lie in a straight line between
  Earth and Sol. It is tilted about 5 from the
  ecliptic. Because of this tilt, eclipses are much
  rarer than expected.
• http//eclipse.gsfc.nasa.gov/eclipse.html

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Tides

• Tides are caused mainly by differences in how
  much Lunas gravity pulls on different parts of
  Earth.
• Tides are the regular rise and fall of ocean
  water. The ocean waters rise for about 6 hours a
  day, and fall for about 6 hours a day. Therefore
  there are two high tides and two low tides every
  24 hours.
• Lunas gravity causes tides. The force of the
  moons gravity causes ocean water on Earth to
  move higher in some places and lower in other
  places.
• Sols gravity also pulls on Earths ocean waters.

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Tides

• During a NEW MOON, Sol, Earth, and Luna are lined
  up in a straight line. The combined forces of the
  sun and the moon cause spring tides. A spring
  tide is the highest possible high tide.
• Sometimes the sun, moon, and Earth form a right
  angle (90). This arrangement occur at the FIRST
  and THIRD QUARTER moons, and produces a neap
  tide. A neap tide is the lowest possible high
  tide.

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