Title: The Four Seasons

Purpose: To model the four seasons of the Earth.

Materials: A globe or round object representing the Earth, Strong, round light source, string (~4m long).

Procedure:

  1. Look on your globe and find the North and South Poles. Find the Equator.
  2. If your axis and your equator are not marked, mark them with a pen/pencil.
  3. Position a lamp in the center of a table or other flat surface. The lamp will represent the Sun.
  4. Using the string, mark an oval path around the lamp as shown in fig.1, the length of the oval should be about 1 meter to 1.5 meters.
  5. Turn on the lamp. Hold the Earth, at an angle at point A. Keep the middle of the globe at the same level as the lamp. Note where the light is shining on the globe and record your observations.
  6. Slowly move he globe around the lamp in a counterclockwise direction, using the string as a guide. Be sure to keep the angle of the globe constant as you move it. Keep the poles in the same direction as you move it around the circle.
  7. Note where the light is shining on the globe as you move it through points B, C, and D. Record your observations.
  8. Return the globe to point A. Hold the globe upright, as shown in Fig. 2. The middle of the globe should be at the same level as the lamp.
  9. Slowly move the globe around the lamp through points B, C, and D. Note where the light is shining on the globe at each point. Record your observations.

Fig. 1

Fig. 2

Data:

Observations:

  1. Where is the light shining on the globe when you hold it at an angle?

Point A ______

Point B ______

Point C ______

Point D ______

  1. Where is the light shining on the globe when you hold it upright?

Point A ______

Point B ______

Point C ______

Point D ______

Analysis and Conclusions:

  1. When you held the globe at an angle, at which point was the top half of the globe receiving the most light?
  1. At which point was the bottom half receiving the most light?
  1. When you held the globe at an angle, where there points at which the top and bottom halves were receiving equal amounts of light? If so, what were these points?
  1. Which point represents summer in the N. Hemisphere?
  1. At which point would the N. Hemisphere have spring? What season would the S. Hemisphere have at the same time?
  1. If the Earth were not tilted on its axis, would we still have four seasons? Explain.
  1. What causes the Earth’s four seasons?