To explore how the amount of sunlight and heat change in areas that are shaded.
This lesson was developed by the Challenger Center as part of NASA's MESSENGER Mission, of which Science NetLinks is a partner.
In this lesson, students will make inferences about the cause of shadows by observing and making their own shadows in the sun. Many properties of shadows (such as heat and brightness of light) will also be identified firsthand as students conduct a number of simple experiments to observe changes that are comparable to those experienced by the MESSENGER spacecraft in its voyage to and around Mercury. Refer to the Science Overview of the lesson for a summary of the science content relevant to the activities in the lesson. Refer to the Lesson Overview for a more detailed explanation of what students will learn from the lesson.
While teaching, it is recommended that you do not introduce the scientific concept of energy or any in-depth explanations about heat energy, so as to limit student confusion and save teaching time. Overall, students should walk away from this lesson having made qualitative approximations and a basic understanding of the concepts surrounding the sun's heat energy. (Benchmarks for Science Literacy, p. 83.)
When observing the shadows around them, encourage students to look for what changes and what does not and question where things come from and where things go. Such activities can sharpen their observation and communication skills and instill in them a growing sense that many different kinds of change go on all the time. Students at this level should also be encouraged to take, record, and display counts and simple measurements of things over time. This activity can provide them with many opportunities to learn and use elementary mathematics. (Benchmarks for Science Literacy, p. 272.)
In addition, be aware that research shows that even after some years of instruction, students do not distinguish well between heat and temperature when they explain thermal phenomena. Their belief that temperature is the measure of heat is particularly resistant to change. Long-term teaching interventions are required for upper middle-school students to start differentiating between heat and temperature. (Science for All Americans, p. 337.)
The four activities presented in this lesson can be implemented one per day over a four-day period.
Note: Parts of this lesson were extracted from the unit, Staying Cool.
Bear Shadow by Frank Asch is required for this lesson.
On the first day, begin the lesson by conducting the Warm-Up and Pre-Assessment portion of Activity 1: Shadows. Ask students what they think or know about the nature and origin of shadows.
The generation of heat by sunlight is also why shadows are an important part of the MESSENGER mission to Mercury. Over the course of this four-day lesson plan, when appropriate, have students consider the essential question of this lesson: How does the amount of sunlight and heat change in areas that are shaded?
Continue with and complete the Activity 1: Shadows, where students are divided into two teams to explore and track shadows of different objects over the course of the day to discover patterns in the behavior of shadows, sunlight, and temperature.
On the second day, have students do Activity 2: Bear Shadow, where they learn more about shadows by reading Bear Shadow by Frank Asch, a story about a bear that attempts to escape a shadow that seems to be chasing him. As part of this activity, students will consider the size and shapes of their own shadows, and conditions that cause them to change.
On the third day, have students complete Activity 3: Making Scale Model Shadows of Bear's Neighborhood, where they will construct a model of the bear's neighborhood to measure sun shadows and to demonstrate their understanding of shadows in general.
On the fourth day, have students do Activity 4: Creating Shadows of a Model Earth , where they experiment with making shadows of a three-dimensional object, including a globe, to see how they can alter the size, shape, and position of their shadows.
Reread Bear Shadow and conduct the other discussion activities highlighted in the Assessment section from Activity 4: Creating Shadows of a Model Earth. Make sure to review and reinforce key ideas and concepts that students learned about shadows, sunlight, and temperature in the four activities. Remind students of how these concepts relate to the MESSENGER mission to Mercury.
Have students trace each other's shadows on the ground at different times of the day. Mark the footprints of a child so that he or she stands in exactly the same place at three or four different times. Have another student trace the shadow in a different color each time. Write the exact time in the same color chalk (or draw a clock with the hands pointing to that time). Discuss the movement of the shadows, time of day, and the placement of the sun. Have students speculate as to what will happen as the sun sets in the evening. Point out the importance of sunlight when artists decide to paint something outside, and how objects can look different when placed in different lights.