Phases, Eclipses, and Tides

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Phases, Eclipses, and Tides

• Chapter One, Section Three

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Essential Question

• What effects are caused by the motions of Earth
  and the moon?

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Objectives

• 1. Explain what causes the phases of the moon.
• 2. Compare and contrast solar and lunar eclipses.
• 3. Explain what causes the tides to occur.

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• Motions of the Moon
• A. Moon revolves around Earth and
• rotates on its axis
• B. Changing positions of moon, Earth,
• and sun cause phases of moon,
• eclipses, and tides

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• C. Moon rotates once on its axis in the
• same amount of time as it revolves
• around Earth. A day and a year
• on moon are the same length
• D. Same side of moon always faces
• Earth

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• E. Moons day is shorter than 29.5 Earth days
  because as Earth revolves around sun, moon
  revolves around Earth

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• II. Phases of the Moon
• A. The moon does not produce its own
• light, it reflects the suns light
• B. phases- different shapes of the moon
• you see from Earth
• 1. Moon goes through its whole set of
  phases each time it makes a
• revolution around Earth

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• 2. Phases caused by changes in
• position of Earth, moon, and sun
• 3. Phase of moon you see depends
• on how much of the sunlit side of
• moon faces Earth

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• III. Eclipses
• A. When the moons shadow hits
• Earth or Earths shadow hits the
• moon, an eclipse occurs
• B. eclipse- when an object comes
• between the sun and a 3rd object,
• it casts a shadow
• C. Two types of eclipses solar and
• lunar

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• D. When Do Solar Eclipses Occur?
• 1. when moon passes between
• Earth and sun, blocking sunlight
• from Earth
• 2. solar eclipse- occurs when new
• moon blocks your view of sun
• E. Total Solar Eclipse
• 1. umbra- very darkest part of moons
• shadow
• 2. During a total solar eclipse sky is
• dark, air gets cool, you can see
• stars and solar corona

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• F. Partial Solar Eclipses
• 1. penumbra- larger part of shadow
• 2. During a solar eclipse, people in
• penumbra see only a partial
• eclipse
• G. When do lunar eclipses occur?
• 1. lunar eclipse- occurs at a full moon
• when Earth is directly between
• moon and sun

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• 2. During a lunar eclipse, Earth blocks
• sunlight from reaching moon
• H. Total Lunar Eclipses
• 1. When moon is in Earths umbra, you see
• a total lunar eclipse
• 2. total lunar eclipse can be seen anywhere
• on Earth that moon is visible
• I. Partial Lunar Eclipses
• 1. Occurs when moon passes partly
• into umbra of Earths shadow.

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• IV. Tides
• A. Tides- rise and fall of ocean water,
• occurs every 12.5 hrs Water
• rises for about 6 hrs then falls for
  
• about 6 hrs.
• B. Tides are caused mainly by differences
• in how much moons gravity pulls on
  
• different parts of Earth

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• C. Tide Cycle
• 1. At any one point in time, there are 2
• places with high tides and 2 places with
• low tides
• 2. As Earth rotates, 1 high tide stays on
• the side of Earth facing the moon. The
• 2nd high tide stays on the opposite
  side
• of Earth

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• D. Spring Tides
• 1. Occur when Earth moon and
• sun are nearly lined up
• 2. Occur 2xs/month at new and
• full moons
• 3. Spring tide- combined forces
• produce a tide with greatest
• difference between low and
• high tides highest high tides

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• E. Neap Tides
• 1. Occur 2 xs/month at 1st and 3rd
• quarter moons
• 2. Happen when Earth and sun are
• at right angles with moon
• 3. Neap tides- a tide with the least
• difference between low and high
• tides lowest high tides