Dear Mr' Wyss

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Dear Mr. Wyss

• Thanks for having your class write
• me with pictures explaining the
• Seasons. First of all, I think Im more
• confused than before I asked your
• class for help. Maybe you could help me
  understand a little better.
• Sincerely,
• Johnny P.

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Reasons for the Seasons

• The amount of sunlight the earth receives is
  called insolation (incoming solar radiation).
• Two factors cause insolation to change
• Length of day (because more
  hours of daylight means more
  insolation),
• The angle that sunlight strikes
  the earth's surface.

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As the angle of the sun changes, less direct
radiation hits the surface to warm it.
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66.5º N
23.5º N
0º
23.5º S
66.5º S
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Since the Earth is a sphere, only certain places
on Earth receive direct rays from the sun.
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Spring (Vernal) Equinox Sun Vertical _at_ Equator
Winter Solstice Sun Vertical _at_ 23 ½º S
Summer Solstice Sun Vertical _at_ 23 ½º N
Autumn (Autumnal) Equinox Sun - Vertical _at_
Equator
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