PH Earth Science

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PH Earth Science

• The Earth-Moon System

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Planet Earth

• Earth is the third planet from the Sun.
• Earth rotates (spins) on its imaginary axis and
  revolves (circles) around the sun.
• Water occurs as a solid (ice), a liquid, or a gas
  (water vapor)
• Earth has one natural satellite, the moon.
• - Satellite Any object that revolves around
  another object

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• Earths rotation
• Causes day and night
• 50 of the earth is always lit by the sun.
• One rotation takes 24 hours (1 day)
• Earths revolution
• Earth revolves around, or orbits, the sun.
• One revolution takes 365 days (1 year)
• - Orbit the curved path followed by a satellite
  (Earth is a satellite of the sun.)
• Why do things orbit other things?
• GRAVITY!

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• Earths revolution and seasons
• Earth is tilted on its axis 23.5 degrees
• This tilt combined with its revolution causes the
  seasons.
• Animation of revolution and seasons

• Summer occurs when a hemisphere is tilted towards
  the sun winter occurs when tilted away
• During summer, direct rays from the sun are more
  concentrated, thus creating more heat energy

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• Summer Solstice day that the North Pole points
  towards the sun occurs June 21 North Pole
  experiences 24 hours of daylight
• Winter Solstice day that the North Pole points
  away from the sun occurs Dec. 21 North Pole
  experiences 24 hours of darkness
• Vernal and Autumnal Equinox days when the North
  Pole is pointed neither towards or away from the
  sun
• - most direct rays of the sun are focused at the
  equator
• -Spring March 21, Fall September 21

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The four seasons, solstices and equinoxes
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Earths Natural Satellite The Moon
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The Moon

• Orbits Earth once every 29.5 days and also
  rotates on its axis once every 29.5 days. This
  means the same side of the moon always faces
  Earth.
• Has no atmosphere, no water, and no life.
• Is ¼ the diameter of Earth and has ¼ the
  gravity of Earth.
• Drastic temperature changes between the light
  (hot) and dark (cold) side - due to the lack of
  an atmosphere.

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The Moon

• 50 of the moon is always lit by the sun it does
  NOT give off its own light.
• The portion of the lit side facing the earth
  causes the phases of the moon.
• The gravity of the moon and sun cause the Earths
  tides - the daily, periodic rise and fall of
  water level.

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One Small Step

• 12 Americans have walked on the moon.
• Apollo 11 was the first manned mission to land on
  the moon.
• Neil Armstrong and Buzz Aldrin were the first men
  to walk on the moon.

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Q If ½ of the moon is always lit by the sun, why
do we not always see it? A Because the lit side
does not always face us! click for animation
Phases of the Moon
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Phases of the moon

• New moon
• Waxing Crescent
• First quarter
• Waxing Gibbous
• Full moon

• Waning Gibbous
• Third Quarter
• Waning Crescent
• New moon

It is more important to know what causes the
phases than it is to remember all the names!
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New Moon
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Waxing Crescent
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Waxing Quarter (1st)
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Waxing Gibbous
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Full Moon
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Waning Gibbous
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Waning Quarter (last)
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Waning Crescent
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New Moon
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• Solar eclipses occur when the moon blocks
  sunlight from Earths surface. (S m E)
• animation
• Lunar eclipses occur when Earth blocks sunlight
  from reaching the moons surface. (S E m)
• animation

Solar Eclipse August 11, 1999 Soissons, France
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One of Jupiters moons causing a solar eclipse on
Jupiter (notice the shadow).