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Seasons - Earth's Tilt and Day Length

Look closely at the globe picture at the right. Have you ever wondered why all globes are tilted? Perhaps someone told you it is because Earth is tilted. But why does that matter? This activity is to help you figure out what happens because the Earth is tilted.

You will need to work closely with a teacher or parent to make sure that you are safe as you use these materials. Most of the materials are probably available in a classroom.

Materials:

  • Thermometer
  • Black paper
  • Overhead projector

Purpose:
You will show that the amount of heat energy absorbed is related to the angle of the light source.

Background:
Light is a form of energy that can cause object to increase in temperature. Have you ever noticed it is easier to get warmed by the sun's rays when the sun is directly overhead than when it is setting?

Procedure 1:

  1. Take a piece of black paper and fold it in half.
  2. Place a thermometer inside the folded paper.
  3. Place your folded paper directly in front of projector lens in a vertical position as shown in the left photograph.
  4. Record the temperature as you begin.
  5. Record the temperature again after the light has been shining on the paper for two minutes.
  6. Let the paper and thermometer cool to room temperature (about five minutes).
  7. Repeat the same procedure holding the paper at a 45-degree angle or greater as shown in the right photograph.

Vertical Example
45-Degree Example

Procedure 2:

  1. Take a piece of black paper large enough to cover the overhead projector.
  2. Cut a hole that is about 1/2-inch square in the middle of the paper as shown at the right.
  3. Place the projector about one meter (about 36 inches) from wall. The projector should be facing directly at the wall as shown in Example 1.
  4. Measure the area of the light square projected on the wall.
  5. Move the projector so it is at an angle of at least 45 degrees to the wall. The projector will be at an angle to the wall as shown in Example 2 below.
  6. Move projector so it is one meter (or 36 inches) from the wall.
  7. Measure the area of this square.
  8. Optional:  Tape black paper on a board.  Shine a flashlight, directly on the paper.  Outline the lighted area with chalk or white crayon.
  9. Angle the flashlight at 45 degrees and outline the lighted area with chalk or a white crayon.
Example 1
Example 2

Analysis:

  1. In Procedure 1, what difference exists between the temperatures after two minutes with the two angles?  Which example represents winter in Utah?  Why?
  2. In Procedure 2, how does the angle of the light affect the size of the area measured?  Which example represents winter in Utah?  Why?
Utah State Office of Education This Sci-ber Text was developed by the Utah State Office of Education and Glen Westbroek.