31 The Earth in Space

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3-1 The Earth in Space
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EARTH

• The third planet from the sun.
• Rotates on its axis (like all of the other
  planets).
• Revolves around the sun in an elliptical orbit.
• Day and night are caused by rotation.
• The seasons are caused by the tilt of the Earths
  axis and its revolution around the sun.

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Day and Night

• At the equator, the Earth rotates at about 1600
  km/hr.
• It takes the Earth 24 hours to rotate once on its
  axis.
• The amount of time it takes to complete one
  rotation is called a day.
• The part of the Earth that faces the sun is
  bathed in sunlight (DAY).
• The part of the Earth that does not face the sun
  is in darkness (NIGHT).

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The Earths axis is tilted 23.5.

• In regards to the length of daylight and
  darkness, what affect does tilt have on the
• Northern Hemisphere?
• Southern Hemisphere?
• North Pole?
• South Pole?
• Equator?

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http//www.ameritech.net/users/paulcarlisle/earthv
iewer.html
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A Year on Earth

• The Earth takes 365.26 days to complete one
  revolution, or entire trip, around the sun.
• The time is takes Earth to make one revolution
  around the sun is called a year.
• During most years, the calendar only has 365
  days what happens to the extra 0.26 days every
  year?

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Something to consider . . .

• An extra day is added to the calendar every four
  years to account for the 1.04 days (0.26 x 4)
  that the Earth accumulates through its
  revolution however, that still leaves an extra
  0.04 days. After 100 years, that adds up to
  another day. Should we add two days to February
  every one hundred years to account for this
  problem?

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SEASONS ON EARTH

• Most people live in a part of the Earth that has
  four distinct seasons winter, spring, summer,
  and fall.
• Of the other eight planets in the solar system,
  five of them also have seasons (Mars, Saturn,
  Uranus, Neptune, Pluto?).
• Why do you think that these planets have seasons?

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Planets that experience different seasons have a
tilted axis.

• As the Earth revolves around the sun, the axis is
  tilted away from the sun for part of the year and
  toward the sun for part of the year. In other
  words, the North Pole (and South Pole) tilts
  toward or away from the sun depending on the time
  of year.
• Winter solstice (December 21 or 22).
• Summer solstice (June 20 or 21).

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Does tilt always have an affect?

• Twice a year, in spring and in autumn, neither
  the North Pole nor the South Pole is tilted
  toward the sun.
• Vernal equinox (March 20 or 21).
• Autumnal equinox (September 22 or 23).

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MAGNETOSPHERE

• The Earths magnetic field is called the
  magnetosphere.
• The Earths magnetism forms a magnetic field
  around the Earth similar to the magnetic field
  around a bar magnet.
• What do you know about magnets?

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Likes repel opposites attract!

• The geographic north pole is actually the
  magnetic south pole.
• The geographic south pole is actually the
  magnetic north pole.
• Now, remembering the main property of magnets,
  let look at a compass.

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Effects of the MAGNETOSPHERE

• Van Allen radiation belts
• Two doughnut-shaped regions of charged particles
  that are formed as the magnetosphere traps some
  of the particles in the solar wind.
• Outer belt electrons
• Inner belt protons

• Aurora
• Charged particles trapped by the Van Allen
  radiation belts may travel along magnetic lines
  of force to the Earths poles and collide with
  particles in the upper atmosphere.
• Bands or curtains of shimmering colored lights.

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Ever hear of the

• Aurora borealis?
• Aurora australis?