To investigate shadows, using literature-based discussion as well as experiences with manipulating shadows.
This lesson is part of a four-lesson series in which students observe the daytime and nighttime sky regularly to identify sequences of changes and to look for patterns in these changes. At the K-2 level, learning about objects in the sky should be entirely observational and qualitative. The priority is to get students noticing and describing what objects in the sky look like at different times. (Benchmarks for Science Literacy, p. 62.)
The sun, moon, stars, clouds, birds, and airplanes all have properties, locations, and movements that can be observed and described. Ideally, students should engage in direct observation of both the daytime and nighttime sky throughout this lesson series. However, the recommended Internet resources can be helpful to enhance student experiences, or if opportunities for direct observation are limited. This investigation requires that observations be ongoing, so that students can look for patterns over time. As children become more familiar with objects in the sky, they can be guided to observe changes, such as nigh and day and the seasons.
In Sky 1: Objects in the Sky, students investigated objects in the daytime and nighttime sky.
In this lesson, students will explore making shadows and tracking the movement of an object over the course of a day to look for patterns. It is best to couple this shadow activity with reading the book, Bear Shadow, and making a map of Bear's neighborhood when the sun is relatively high in the sky, either near the beginning or the end of the school year. You'll want to measure sun shadows at least twice and perhaps three or four times during the year to see how they vary with the time of year.
In Sky 3: Modeling Shadows, students construct models to demonstrate their understanding of shadows.
Sky 4: The Moon has students drawing the moon's shape for each evening on a calendar and then determining the pattern in the shapes over several weeks.
This lesson uses the book Bear Shadow by Frank Asch.
Either individually or as a participatory exercise, you and the students should read Bear Shadow by Frank Asch and discuss. In this story, a bear attempts to escape a shadow that seems to be chasing him. If this will be the introduction to a study of shadows, with particular emphasis on those caused by the sun, spend time finding out what students already know about shadows. You might guide this discussion by asking questions such as:
- What do you know about shadows that makes the book funny?
- Why did Bear's shadow disappear when he hid behind a tree?
- Why did the shadow disappear when he buried it?
- What makes a sun shadow fall one direction at one time and another direction earlier or later in the day?
- What other questions do you have about shadows?
Use the responses to help the children shape activities through which they will discover the answers to their questions.
If you have already begun the study of shadows and have measured sun shadows at least once, your discussion of Bear Shadow can be more pointed. In addition to the kinds of questions above, you can, for example, discuss the time of day when the various events occur and the direction Bear's shadow will fall at these times.
Eyes on the Sky, Feet on the Ground: Hands on Astronomy Activities for Kids, offers various astronomy topics and activities. Under The Earth's Rotation, read Activity 1-1: Making Shadows, and complete the suggested activities with students. Here, students use different objects and angles to create, trace, and manipulate shadows. This activity includes a thorough list of discussion questions, as well as ideas for extending a study of shadows. In addition to the questions included in the lesson, ask students:
- How can you "make" a shadow?
- What is the light source?
- How is the shadow similar to the object you used to make it? How is it different?
- How can you change the size of your shadow?
- How can you change the shape of your shadow?
- How can you change the position of your shadow?
In Activity 1-2: Tracking Sun Shadows, also found on The Earth's Rotation page, students use a yardstick and coffee can full of stones to create a shadowstick. Students visit the shadowstick throughout the day, taking periodic measurements by tracing the line of the shadow and marking the time of day. Encourage students to begin making predictions about where the shadow might fall next. This activity can also be conducted as an indoor activity for small groups, using a drinking straw and clay. Full instructions and list of materials for both activities can be found at the site.
Follow the activities given at the site, but instead of just marking a point at the end of each shadow, draw the full line from the center of the posterboard to the end of the shadow. (These lines will be helpful when students are later asked to measure the shadows.) Each time students visit the shadowstick in the course of the day, ask them to compare the new shadow line to those drawn previously: Has it changed? How has it changed?
At the end of the day, bring the posterboard inside. Have student volunteers measure the distance from the center of the board (where the lines cross) to the end of each shadow line using cubes. Use the cubes to create a bar graph that represents the length of the shadows at the various times observed.
- What does the graph look like?
- When is the shadow shortest?
- When is it longest?
- What do you notice about the lines? Does the pattern of the lines remind you of anything?
Reread Bear Shadow. As a class, identify those aspects of the story that are purely fictional and those that “could happen,” paying particular attention to how shadows change during the day. Compare the shadows in Bear Shadow to those students made and tracked in the Development activities. You could revisit the discussion questions listed in the Motivation, especially focusing on the last one, "What other questions do you have about shadows?" You could spend time answering the students' questions, as well as generating ones to be answered in the other lessons of this series.
As a class, create a nonfiction version of the story in Frank Asch's Bear Shadow.