Reason for Season

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Reason for Season
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Reason 1

• Earth orbiting around the sun
• REVOLUTION

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Season

• Due to Earths revolution,
• Every season, Earth is at different position
  around the sun

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Summer

• Earths axis is tilted toward the sun
• June 21 or 22 (summer solstice)

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Fall

• Autumnal Equinox
• Sept. 21 or 22
• Half side of the globe able to receive daylight

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Winter

• When Earth Axis is tilted away from the sun
• Winter solstice (Dec 21 or 22)
• (Video)

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Spring

• Vernal Equinox
• March 21 or 22
• Half of the globe able to receive daylight

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Position of the Earth during different season
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Daylight Hours
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Summer Solstice

• Northern Hemisphere is tilted toward the sun
• 24 hours of daylight at North Pole
• 24 hours of darkness at South Pole
• Here 14 hours of daylight

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Winter

• N. Hemisphere is tilted away from the sun
• 24 hours of darkness at North Pole
• 24 hours of daylight at South Pole
• Here 9 hours

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Autumnal Equinox

• Half of the Earth receives daylight
• 12 hours everywhere

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Vernal Equinox

• Half of the Earth is able to receive daylight
• 12 hours of daylight everywhere

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• Although the poles can receive 24 hours of
  daylight, the Poles are always so cold.
• WHY?

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Flash Light demonstration

• Angle 90 (more intense)
• Angle lower than 90--? (light spreads out more -?
  less INTENSE)

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Season

• The Flashlight represents the sunrays
• When sunray hits the Earth Surface at 90 ------?
  intense radiation ---? hot temperature

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Summer

• Because N. Hemisphere is tilted toward the sun,
  direct rays hit at
• 23.5 North (Tropic of Cancer) --? HOT!!!!!

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Winter

• Because the North Hemisphere is titled away from
  the sun, direct rays hit
• at 23.5 S (Tropic of Capricorn)---?HOT!!!!

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Fall

• Earth is still tilted but at a position where
  half of the earth all be able to receive sunrays
• The direct rays hit at the equator

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Spring

• Same as the fall diagram
• Half of the Earth receive sunrays
• Most direct rays are at equator

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Reason for Season

• Revolution around the sun
• Earth at different position therefore it is
  able to receive different amount of
• daylight
• Tilt on the axis
• provides sunray hitting at different angle

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REVIEW

• Why does tilt of the Earth gives us season?
• Curved surface of the Earth receive sunray at
  different angle, when the sun ray hits the
  surface at 90 degree ?most intense radiation.
• Different daylight hours at different latitudes
• During summer solstice for us, where is the
  direct sun ray hitting?
• Tropic of cancer 23.5 degree NORTH

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REVIEW

• Where on Earth could have 24 hours of darkness?
  What season?
• North Pole, during winter solstice for us
• South Pole, during summer solstice of us
• What latitude is arctic circle?
• 66.5 degree North
• What special about artic circle?
• Able to receive 24 hours of darkness and daylight

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REVIEW

• Where is the direct sun ray during the equinox?
• Equator
• If an observer is at 23.5 N latitude, where
  would the sun be during June 21
• 90 degrees (directly overhead)

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REVIEW

• What is aphelion?
• A point where the Earth the most far away from
  the sun
• See animation
• What is perihelion?
• A point where the Earth is closest to the sun

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• What if?

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What ifs about season

• What if Earth is not titled? Describe the season
• Warmer winter
• Cooler summer
• What if the Earth doesnt revolve around the sun?
• Only one season

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What ifs about season

• What if the orbit was circular?
• Doesnt affect season
• Only affects the apparent diameter of the sun

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Critical Thinking
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• Does the Earth rotate at the same speed within
  all layers?
• No b/c outer core is liquid
• Does the coriolis force work within all layers?
• No because of the different phases

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Suns path at during different season
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True for 42N

• The sun does not rise exactly from East and set
  exactly at West during Winter and Summer because
  of Earths tilt

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TRUE for 42

• The sun is never directly overhead
• at 90 degrees for 42N latitude.
• The highest point is 65.5 degrees

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TRUE for 0

• 12 hours of daylight during every season
• The sun is directly above at 90 during fall and
  spring

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Equinox, day and night equal in name
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Refraction

• The bending of light when it moves from one
  medium to another medium
• EX AIR TO WATER

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Why does light refract?

• Index of refraction
• Different material react with light differently,
  changes the light speed
• RESULT Material displace from their actual
  position

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Refraction

• How does it relate to season?