Lunar and Planetary Institute






Day and Night

Activity: The Cycle of Light


Observe!
Children observe how Earth's rotation causes light and dark cycles.

Cycle of Light

The Activity
Invite the children to examine the materials provided. Explain that they will explore what causes day and night cycles on Earth.

  • What materials will represent Earth and its axes? (Styrofoam ball and toothpicks)
  • What does the Styrofoam ball represent?(Earth)
  • What is missing in order for them to be able to demonstrate the day and night cycle? (Sun)
  • What can be used to represent the Sun?(flashlight)

Have the children place the toothpicks in the ball to represent Earth's north and south poles. For older children, ask them to draw an approximate outline of their continent on the ball, and place a dot roughly where they live. Younger children may just place a dot — or draw an ant — on the ball as a point of reference.

Invite the children to experiment with the materials. Can they make day and night occur in their location on the Styrofoam Earth? Suggest that one child holds the Sun and one holds the Earth. Other group members assist with modeling the day and night cycle. Have them experiment with holding the flashlight at different distances and with dimming the lights to discover which produces the best effect.

If the children are creating day and night cycles by moving Earth around the Sun, ask how long it takes for Earth to go around the Sun. Our revolution around the Sun takes a full year, so this type of motion does not explain the typical 24-hour day and night cycle. To create a day and night cycle, Earth actually does not have to go around the Sun at all!

Use the globe and a flashlight to demonstrate the concept of sunrise and sunset for the location where the children live.

  • Why does the Sun rise earlier in Virginia than in California? Set later in Oregon than in Alabama?
  • In what direction does our Sun “rise” in the morning? (east)
  • Set in the evening? (west)
  • What does this tell us about the direction our Earth rotates? (counterclockwise if viewed from the north pole toothpick)

Have the children share their models and show that Earth rotates on its axis once each 24 hours to create daylight and darkness in their location. Be sure to have the children take turns holding the Earth and holding the Sun.

  • Can the children demonstrate this rotation with their model?
  • What do they observe about day and night from Earth's perspective? (Earth's surface experiences day and night) From the Sun? (Only the sunny side of Earth can be seen)
  • Approximately how long is our day cycle? Night cycle?
  • Does the Earth do anything to cause day and night? (Earth spins, or rotates, on its axis)
  • How often does this happen; how long does one rotation take? (24 hours)

More Activities

Who?
Ages 8–14

How Long?
45 minutes

What's Needed?

• 1 globe (optional; for reference)

For each group of 2 to 4 children

• 1 large Styrofoam ball (6–9 inches)
• 1 marking pen
• 2 toothpicks
• 1 flashlight

Connections to the National Science Standard(s)

Standards A&D (grades K–4):Ask questions about objects and events in the environment, for example, the apparent daily movement of the Sun across the sky. Answer those questions by making observations and investigations, and employing simple tools to gather data. Communicate investigations and explanations.

Standards A&D (grades 5–8): Understand and communicate the scientific explanation of how objects in the solar system have regular and predictable motion, such as the apparent daily movement of the Sun in the day/night cycle.