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Seasons - Changing Day Length

Notice that earth's axis is tilted. When it appears on one side of the sun, the light is stronger in the northern hemisphere. Then when the earth rotates so that the opposite side faces the sun, the light is stronger in the southern hemisphere.

Your goal is to determine how earth's tilt is related to the difference in light strength.

Materials:

  • Globe
  • Masking tape
  • Pen or pencil
  • Bright flashlight or single bulb lamp

Procedure:

  1. Start by numbering the tape from one to twenty four. Leave space between each number so you can tear the tape apart.
  2. Place one piece of tape on each of the longitude lines (going from north to south) which intersect with the latitude line that goes through the United States near Utah.
  3. Have a friend hold the light back so it shines on most of the globe.
  4. The light represents the sun.
  5. Tilt the globe so the North Pole is facing the light. Each number represents a one-hour division on the earth. Slowly turn the globe and see how many of the numbers can be seen at the same time. 
  6. Record your observations in your science journal.
  7. Now tilt the globe so the North Pole is facing away from the light. Slowly turn the globe and see how many numbers can be seen at the same time.  Record your observations in your science journal.

Analysis:

  1. When are the most hours visible in the northern hemisphere:
    • When the North Pole faces the sun or when the South Pole faces the sun?
  2. Is there ever a time when the North Pole is always receiving sunlight?
  3. Choose a country in the northern hemisphere and another country in the southern hemisphere.  Make a graph or graphic organizer that compares the amount of daylight hours each of these countries experience during summer and winter seasons. 
utah state board of education This Sci-ber Text was developed by the Utah State Board of Education and Utah educators.
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