Earth

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Earth
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shape

• Oblique Spheroid (bulges at the equator)
• Composed of mostly rock
• Surrounded by an atmosphere of gases
• 70 Nitrogen 21 Oxygen
• 70 of solid surface is covered with water.
• Diameter at equator 12,756 km
• Diameter between poles 12,714km

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atmosphere
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Earths rotation

• Earth rotates from west to east
• Counterclockwise direction
• Spins on its axis of rotation
• 24 hour period
• Causes daily change from day to night
• Daily motions of the sun, moon, planets, and
  stars across the sky are caused by Earths
  rotation. Objects appear to rise in the east and
  set in the west.

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Earths revolution

• Earth travels around the sun in an elliptical
  orbit.
• Time it takes Earth to revolve around the sun
  defines a year.
• 365 ¼ days to revolve around the sun.
• Extra day added every four years (Leap year) to
  make up with ¼ leftover day

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seasons

• Earths revolution around the sun combined with
  the tilt of Earths axis (23.5 degrees) causes
  the changing seasons on Earth.
• Earths axis is always tilted toward the North
  Star.
• Other stars move across the night sky except for
  the North Star because the axis points to it.

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seasons

• In the summer, the Northern Hemisphere is tilted
  toward the sun. Suns rays strike the Earth more
  directly and daylight lasts longer.
• In the winter, the Northern Hemisphere is tilted
  away from the sun. Suns rays come in at a low
  angle and the days are shorter.

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Shadows

• Sun is highest in the sky each day at noon.
• Shadows at noon always point in a northerly
  direction.

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constellations

• Stars in the night sky form patterns.
• Different constellations become visible at night
  due to Earths revolution.

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January Caelum Dorado Mensa Orion Reticulum
Taurus
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Moon

• Ball of rock that revolves around Earth as Earth
  revolves around the sun.
• Earths only natural satellite
• Contains no water or air Cant support life.
• Moons gravity is too weak to hold moisture or an
  atmosphere at its surface.

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Motions and Phases of the Moon

• 29 ½ days to revolve around Earth (about one
  month)
• Rotates on its axis while it orbits Earth
• Completes one rotation in the same amount of time
  it takes to orbit Earth
• Same side of the moon always faces Earth
• Reflects light from the sun

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• Sun lights half of the moons surface at all
  times.
• As the moon revolves around Earth, we see varying
  amounts of its lighted side so the shape of the
  moon appears to change. The moon takes 3 ½ days
  to move between each phase.
• New Moon- the moon is between Earth and the sun.
  The side facing Earth is dark so the moon cannot
  be seen.
• Full Moon- the moon is on the opposite side of
  Earth from the sun. The side facing Earth is
  completely illuminated.

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eclipses

• Occur when the sun, Earth, and moon are lined up.
• Lunar Eclipse occurs when the moon passes through
  Earths shadow, which can only occur when the
  moon is full.
• Solar Eclipse takes place when the moons shadow
  is cast on Earth, which can occur only during new
  moon phase.

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Solar Eclipse
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tides

• Rise and fall in the level of ocean waters that
  take place twice each day.
• Caused by the gravitational pull of the moon and
  the sun.
• Moons gravity affects Earths tides.
• Pull of the moons gravity draws the ocean waters
  into two large bulges. One on the side of Earth
  facing the moon and one on Earths opposite side.

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• Causes high tides at those positions.
• Halfway between tidal bulges the ocean level
  falls, producing low tides.
• As Earth rotates, locations on Earth experience
  changing tides.