1. Sun-Earth System Investigation 3, Part 2
Seasons and Sun
Sun-Earth System
Investigation 3, Part 2
TG-P.97-98

2. Review
Review the following questions from “Wendy and Her Worldwide Weather Watchers”:
Which locations have the greatest number of hours of daylight on June 21? The fewest hours of daylight?
Which locations have the greatest number of hours of daylight on December 21? The fewest hours of daylight?
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3. Review
Alpena, Michigan is located 45 degrees north of the equator. How much daylight do you estimate they have on June 21? December 21?
Boulder, Colorado has a latitude of 40 degrees north. Wellington, New Zealand has a latitude of 41 degrees south. Which city has the longest amount of daylight on June 21?
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4. What ideas do you have to explain why daylight hours change over a year?
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5. Sun-Earth Model Represent the Earth and the Sun
How should I set up the model?
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6. Sun-Earth System
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7. Revolution The movement of one object around another
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*This takes 365 days (1 year)
*The Earth revolves around the Sun

8. Rotation The Earth turning on its axis
*One rotation on it axis takes 24 hours (1day)
Earth has a North and South Pole
Axis is the imaginary line that if you connect the North and South Pole
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*The axis is tipped over at an angle of 23.5˚

9. Rotation
How do we know where it is day and where it is night on this globe?
Day
Night
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How much of the globe is in daylight at any given time?
Always exactly half illuminated and half dark

10. North Star (called Polaris)
Always positioned directly over Earth’s North Pole
Used as a navigation aid to seafarers and explorers for centuries
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11. Summary
Is there a part of Earth that experiences only daylight or only darkness during the year?
Above the Arctic Circle
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Below the Antarctic Circle

12. Equinox Two days during the year that day and night hours are equal
Comes from Latin meaning “equal night”
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13. Fall Equinox Spring Equinox (Autumnal equinox)
occurs around September 21
Fall Equinox
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(Vernal equinox)
occurs around March 21
Spring Equinox

14. Longest Day in the Northern Hemisphere?
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Which way is the North Pole tilted?
Toward the Sun

15. Solstices Summer Solstice Winter Solstice Around June 21
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Winter Solstice
Around June 21
The longest day of the year
Solstice means “sun stands still”
Around December 21
The shortest day of the year

16. North Pole is tilted neither toward nor away from the Sun
At fall equinox
North Pole is tilted neither toward nor away from the Sun
Sun is directly over the equator
Half in daylight and half in darkness
At winter solstice
North Pole is now tilted away from the Sun
Shortest day of the year
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At summer solstice
North Pole is tilted toward the Sun
Northern Hemisphere receives more sunlight
At summer solstice
North Pole is tilted toward the Sun
Northern Hemisphere receives more sunlight
At summer solstice
North Pole is tilted toward the Sun
Northern Hemisphere receives more sunlight
At spring equinox
Sun is directly over the equator
Day and night are equal

17. Seasons At winter solstice Days are shortest At fall equinox
Less exposure to light, lower temperatures
Snow, ice, frost, etc
At fall equinox
Days are getting shorter
Less exposure to light, lower temperatures
At summer solstice
Days are longer
Longer exposure to light produces the effects of summer
Warmer temperatures, plant growth
Seasons
At spring equinox
Days are getting longer
Exposure to light is increasing, raising temperatures
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18. Reading
Read “Seasons” starting on page 17 of your green resource book.
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Student Resource Book P.17-19

19. Multimedia Turn to “Seasonal Changes”
You will use the Sun-Earth program on the CD-ROM to answer the questions on page 9 of your lab book.
The questions are difficult, so make careful observations and concentrate
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20. Response Sheet
After you finish the Multimedia, turn to pg 11 in your Lab Notebook – Seasons and Sun
Complete the assignment
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Student Lab Notebooks P.11
TG -Teacher Assessment Master p. 383/p. 426