Sundials

• Describe what you see.
• Describe what is making the shadow.
• Make a prediction about what might happen to the shadow when we come back later.
• Describe what happened to the shadow since the first time we traced it.
• Explain what is making the shadow change.

• You could use a camera (instead of butcher paper) to document the shadows.
• You can do this activity several times throughout a month or a season, or do it seasonally. The children will be able to see the changes in the shadows if the shadows are documented using the same position for the sundial (or broomstick) and if the children are standing in the same spot every time they document this.
• Keep the butcher paper, labeled with the date and time of day from one season to the next, to compare the shadows. Discuss why the shadows are longer or shorter depending on the season.
• Make a gnomon out of clay and a pencil. Use flashlights to create shadows.

• Could children explain what created the shadow?
• Could children explain why shadows changed during the day?
• Could children explain that the Sun or another light source is needed to make shadows?

Shadows are created by the Sun or another light source shining on an object. Any object that can block light will create a shadow. A good example is your body. Since light cannot pass through your body, your body creates a dark area where it blocks the sunlight. The patch where the light cannot reach is called a “shadow.” Shadows change in length over the course of the day. Longer shadows are cast early in the morning and late in the afternoon. The shortest shadow is at noon when the Sun is directly overhead. Because the Earth is moving, the Sun, which is the source of light, is in a continually changing position in the sky, creating the change in shadows.

A long time ago, people began to notice how much of the day was over by looking at their shadows. Eventually, this led to the invention of the sundial. A simple sundial is a stick, or “gnomon,” set in the center of a round, flat surface that stays in the same place during the course of the day. The sundial works by casting a shadow from the gnomon in different positions at different times of the day.

• Sun – the star that is nearest to the Earth; the Earth receives heat and light from the Sun and travels around it.
• light – the form of energy that makes it possible for the eye to see. The Sun produces light.
• shadow – the dark image on a surface caused by something that blocks light from the Sun.
• change – to become different.
• sundial – a device that stands in a garden or on a lawn to show the time of day. A sundial has a flat, round disk with numbers and a pointer that casts a shadow. As the shadow moves across the numbers, the sundial shows what time it is.
• gnomon – the column on a sundial that casts a shadow and thus indicates the time of day.

• Be sure to do this activity on a sunny day.
• Be certain that the sundial/broom in a bucket and you are in exactly the same spot each time you trace the shadow of the sundial.
• Some children might be tempted to look at the Sun once they realize the Sun is creating the shadows. Explain to them that it is very important not to look directly at the Sun because it will damage their eyes.
• If a sundial is not available, you can use a flagpole or a stationary pole from the playground equipment as a substitute. Make sure that the pole is stationary and will not move over time.

• Moonbear’s Shadow by Frank Asch
• Shadow by Suzy Lee
• Guess Whose Shadow? by Stephen R. Swinburne
• What Makes a Shadow? by Clyde Robert Bulla