**Caution: It is not safe to look directly at the sun!**
FOCUS: As the Earth spins on its axis and travels around the sun, we experience day and night and the seasons. The sun’s rays give us energy in the form of light and heat. Solar energy warms the Earth, fuels the water cycle, and generates our weather systems. It provides the energy for plants to carry out photosynthesis, the basis of food chains and webs, and the conditions in which living things can exist. Through engineering we can also harness the sun’s energy for our own uses.
Objective: To begin to explore and ask questions about the sun.
Take children outside to do Eyes Closed and Tracing Shadows to begin with. You will revisit the shadow tracings later.
Materials: sidewalk chalk, one for every two students.
*Remind children that they must never look directly at the sun for it can harm their eyes.
Objective: To notice how we can sense the direction of the sun even with our eyes closed.
Bring children outside. Remind them that looking directly at the sun can be harmful to their eyes. Have everyone close their eyes and turn slowly in a circle two times, and then stop when they feel the sun shining on the back of their heads.
Where will their shadows be? (in front of them). Have the children open their eyes and look on the ground for their shadows to see if they correctly identified the position of the sun. How could we sense the sun with eyes shut? (We can feel the warmth on the back of our head. Our eyelids block some but not all of the light.)
NIGHTTIME – DAYTIME
Objective: To model the rotation of the Earth on its axis and see how light reaches only the part of the Earth facing the sun.
To see how we experience night and day, use a globe or a model of the Earth made with a ball of yarn (or an orange), a bamboo skewer for the Earth’s axis, and an elastic band around the middle for the equator. Mark the place where you live with a pushpin. Have one person shine a flashlight, representing the sun, at the Earth model while the leader slowly turns it on its axis (counterclockwise when looking down on the Earth). Have the children say when it is daytime in your location and when it is nighttime. It helps to turn off the lights for this activity.
Now have the children act out being the Earth. Form a circle with an adult in the middle, acting as the “sun.” Begin with everyone facing away from the sun. Have the children slowly turn counterclockwise (towards their left hand) keeping their heads facing straight ahead. Have them say “Daytime!” when they see the sun, keep turning and say, “Nighttime!” when they can’t see it anymore.
For older children, have them freeze when they catch their first glimpse of the “sun.” Ask what time of day it is. (Sunrise.) What part of their body is facing the sun? (Left arm.) Turn until they are facing straight at the sun, then freeze again. Time of day? (Noon.) Continue turning until they are about to lose sight of the sun, then freeze. Time of day? (Sunset.) What part of their body is facing the sun? (Right arm.) What time of day is it when they can’t see the sun? (Nighttime.) What time of day is it when they can? (Daytime.) Did the person representing the sun move? Is the sun really moving across the sky? (No. It is the Earth that is rotating.)
Materials: globe or model of Earth made with a ball of yarn or an orange, bamboo skewer, rubber band, pushpin, flashlight.
PUPPET SHOW “The Sun Is Falling”
Objective: To discover why the sun is important to living things on Earth.
Perform the puppet show, or have a group of children perform it for the class. Afterward, ask questions to review the key details and vocabulary in the story. Holding up each puppet in turn, ask what each one needed from the sun. (Warmth, light, energy, rain, food.) Why does the sun appear to rise in the morning and go down at night? (Since the Earth is turning on its axis, it looks to us like the sun is moving across the sky, but it’s really we who are turning.)
Materials: puppets, script, stage.
JUST PASSING THROUGH
Objective: To investigate whether different materials block light or allow light to pass through.
How we could find out if a material blocks light or lets light through? One way is to try to look through it with our eyes, or we could hold it in front of a flashlight to see if the light comes through. A material is transparent if we can see through it, opaque if it blocks light and we can’t see through it, and translucent if some light comes through but we cannot see objects through it.
Have children work in small groups. Give each group a flashlight, a variety of materials to test, and a data sheet. Have them test each material first with their eyes and then holding it in front of a flashlight to see if none, some, or all the light comes through. Have them keep track of their results on the Data Sheet. Encourage children to try other materials found in the classroom as well. Afterward, compare the results from the whole class. Be careful not to look directly at the flashlight, especially if it is an LED bulb. Which materials block the light? (Wood, metal, aluminum foil, some plastics.) Which let some light pass through? (Some colored plastics, paper, leaves.) Which materials let all the light through? (Clear plastic, glass, water.) What are some examples of each from the natural world? (Tree canopy, clouds, water in ponds, air, etc.)
Materials: for each group: a flashlight, block of wood, white and black paper, clear plastic, colored plastic, metal jar lid or piece of foil, a leaf, Data Sheet, pencil.
Objective: To investigate how shadows change with the angle and direction of the light beam.
Have children work in small groups. Give each team a Shadow Direction page, some plastic figures, and a short wooden dowel. Have the children place one of the figures on the paper and shine the flashlight at it. What do they see on the paper? (A shadow.) What shape is the shadow? (Similar to the shape of the object.) Where is it located? (Always on the side away from the light.) What makes a shadow? (Anything that light can’t go through.) Now have the children place the dowel upright in the center of the page. Lower and raise the flashlight to see how the shadow of the dowel changes when the sun is lower or higher in the sky. Have the children take turns moving the flashlight while watching the shadow of the dowel change length and direction. When is it long? When is it short?
Use the flashlight to model the pathway of the sun from east to west above the Shadow Direction page. Where are shadows in the morning? (On the west side of the dowel.) Where are shadows in the afternoon? (On the east side of the dowel.) Where is the sun at noon and what is the shadow like? (Overhead; small, near the dowel.) When is it longest? (Morning and evening.) Where will their shadows be when we go outside?
For older students: In the northern hemisphere, the sun makes an arc in the sky that is always a little to the south of us. It is never directly overhead for those living above the Tropic of Cancer. You may wish to look at a globe to see this latitude line and compare it to where you live. Repeat above procedure, moving the light from east to west, but hold the flashlight a little to the south of the dowel. What happens to the shadow now? (It moves in an arc from west to east but stays in the northern part of the compass rose.)
Materials: for each group: a flashlight, Shadow Direction page, wooden dowel (1” diameter x 3” long), small plastic figures (e.g. dinosaurs, farm animals).
DIRECT IS HOTTER (Grades 3-6)
Objective: To use a model to compare the intensity of angled and direct sunlight.
Have children work in small groups or teams of two. Give each team a flashlight, ruler and piece of white paper. Have them shine the flashlight on the paper and practice moving it from a vertical to a horizontal position, using the ruler to maintain the same distance from the paper. Now hold the flashlight pointing straight down at the paper, about four inches away. Use a pencil to trace around the circle of bright light (not the outer, dimmer circle) on the paper. Now tilt the flashlight to the side, keeping the four inch distance, and trace the lighted area again. What happens to the size and shape of the lighted area when the light is slanted? (It gets longer.) What do they notice about the brightness of the lighted area? (Slanted is dimmer.) How does light shining directly compare to light shining from an angle? (Direct light is brighter but lights a smaller area; slanted light is dimmer but covers a larger area.) Would direct rays be hotter or cooler than angled sunlight? (Hotter – the same amount of energy is concentrated in a smaller area; indirect rays are cooler because the same amount of energy is spread out over a larger area.)
- How does the angle of the sun differ at the equator compared to the North and South Poles? (Cooler at the poles where the rays hit at an angle – show Sun and Earth poster to help visualize this difference.)
- How could this explain colder weather in winter compared to summer? (The sun is lower in winter and so more angled, therefore cooler.)
Materials: Sun and Earth poster; for each small group: flashlight, ruler, white paper, pencil.
UPPER GRADES CHALLENGE: It’s The Tilt (Grades 5-6)
Objective: To model how the tilt of the Earth influences the seasons as we orbit around the sun.
Make a simplified model of the Earth orbiting around the sun. Use a large ball to represent the sun (e.g. ball of yellow yarn or polystyrene ball) and place it on a support such as an empty soup can. Insert four bamboo skewers around the ball’s equator to represent a few of the sun’s rays. Use the Earth model (from the Daytime Nighttime activity) to demonstrate how the Earth revolves around the sun. Looking down on the solar system, the Earth moves in a counterclockwise direction. Beginning with Earth at the winter solstice position, have the children call out the seasons as you move it to spring, summer, fall, and back to winter.
Explain that the Earth is about ninety-three million miles away from the sun, on average. However, it is a little closer to the sun at the winter solstice on one side of the sun and a little farther away at the summer solstice at the opposite end of its orbit. So distance from the sun cannot account for having seasons.
With the globe at the winter solstice position, hold it vertically on its axis so that the skewer (sun’s rays) point right at the Earth’s equator. Now show how the Earth is actually tilted about 23.5 degrees from the vertical. Where do the direct rays fall now? (Below the equator – farther from us.) The tilt stays the same as the Earth orbits around the sun. Move the globe around the sun stopping at each season to show the place where the direct rays shine on it. Show how the direct rays fall north of the equator when we (in the northern hemisphere) have our summer and south of the equator in our winter. In spring and fall, neither hemisphere is tilted towards or away from the sun.
Afterward, hold up the Sun and Earth poster. Have the children decide which side shows our winter and which shows our summer. Why do we have seasons? (Because of the Earth’s tilt – the sun’s rays are more slanted in winter and more direct in summer.)
Outdoor alternative: Have one person act as the sun and a second person hold a globe of the Earth. Put four gym cones on the ground, each one yard away from the sun, to mark the position of the Earth at the winter and summer solstices and spring and fall equinoxes. Have the children say the seasons as the person holding the globe walks counterclockwise around the sun, beginning with winter, moving to spring, summer, fall, and back to the winter solstice position. Have the “Sun” hold out a yardstick to represent the rays of light that reach the Earth. Demonstrate the Earth’s tilt and its effect on the seasons as described above.
Materials: large ball of yellow yarn or polystyrene ball, four bamboo skewers, empty soup can, globe or Earth model from Daytime Nighttime activity, Sun and Earth poster. For outdoor alternative, globe, yardstick, four gym cones marked “Summer,” “Winter,” “Spring,” “Fall.”
THE ICE TEST
Objective: To plan and carry out an investigation to compare how fast ice melts in the sun and the shade.
Ask the children what might be different about being in the shade (where the sun’s rays are being blocked by something like a tree or building) and being in the open. (Might be hotter!) How could we test this with ice cubes? (We could compare how quickly they melt in shady and sunny places.) Have children work with a partner. Give each team two plastic cups, one marked “sun” and one marked “shade.” Place two to three ice cubes in each cup (keeping the number uniform for the whole class.) Have each team place one cup in the full sun and one in a shaded place. Place thermometers in sun and shade as well. Ask the children if they think the ice will melt faster in the sun or in the shade. How will we know? (By how much water is in the cups afterwards.)
Wait ten minutes or until the ice cubes in the shade begin to melt but are not completely melted. Check the thermometers and record the temperature in sun and shade. How much of a difference was there between the sun and shade, if any?
Now have the children collect their cups, being careful not to spill them. Have them remove the ice cubes, carefully leaving just the water in the cups, and compare them. Provide two measuring cups, one marked “sun” and one marked “shade.” Now one by one, have children pour their water into the appropriate measuring cup. Hold up the two measuring cups to compare. Which melted more – ice in the sun or ice in the shade? How much of a difference was there? Did any of the water spill? How might this affect the results? What evidence do they have that sunlight provides heat? (The thermometers, the ice melting.) How might this be helpful for animals and plants? (They can find places to live where there is more or less shade, depending on their needs.)
Materials: plastic cups, two per team, marked “sun” and “shade”; ice cubes, four to six per team; two thermometers; notepad, pencil, two measuring cups, one labeled “sun” and one labeled “shade.”
HARNESS THAT ENERGY (Grades 3-6)
Objective: To investigate how the sun’s energy can be stored as heat or converted to electricity.
Greenhouses (Passive Solar)
Set up two similar-sized clear plastic containers with lids (such as those used to sell lettuce) in a sunny location. Place a sheet of black paper in the bottom of one container and a sheet of white paper in the other. Place a thermometer in each. Place a third thermometer near the boxes. Record starting temperatures of each (they should be about the same). Check again after ten minutes. How does the temperature inside the boxes compare to the outside temperature? Was there a difference between the two boxes? Why might this be? (Dark-colored materials absorb more light energy than light-colored materials.) Can we trap heat energy from the sun? How might we use this heat? (As in a greenhouse – to grow plants in cold climates; to heat water, etc.) What else might let in sunlight and then trap the heat? (Houses, cars, also the atmosphere – which is why scientists refer to the “greenhouse effect.”)
Materials: two large (e.g. 5”x6”x12”) clear plastic boxes with lid such as that used to sell washed lettuce, three thermometers, black paper, white paper, notepad, pencil.
Show the group a battery-operated mini-fan. Ask them what is providing the energy to run the fan. What will happen if they remove the batteries and try turning it on? (It doesn’t work.) Now, working in small groups with a leader, have the children take turns using a solar-powered mini-fan. What happens when it is in the sun? What is supplying the energy to power the fan? Is it dependent on certain conditions? Have the children test it in different places: in the sun, shade, on an overcast day, inside under a light/lamp.
Materials: battery-operated mini-fan with battery; for each small group: a solar panel-powered mini-fan.
Objective: To observe and measure shadows outside, predicting changes in position and size over time.
Have children work in pairs and provide each team with a piece of sidewalk chalk. Bring children to a paved area on which they can see their shadows and draw around them easily. To begin, have one child from each pair stand along an approximately north-south line. Have partners draw around the outline of the shadows, including a circle around each foot (so they can stand in the same position later) or just around the head and feet to save time. Now have partners change places and repeat. Provide older children with measuring tapes so they can measure and note the length of each shadow. Be sure to have children mark their initials in their shadow outlines. Once shadows are drawn, have children make predictions about whether the shadows will get longer or shorter and what direction they will move in, based on their observations from the Telephone Pole activity inside.
After at least twenty minutes, have children return and stand in their shadow outlines. Did the length or direction change? How did the change compare to their predictions? For older students, have them measure the shadows again. What was the average change in length for the class?
Materials: sidewalk chalk, one for every two students; for older students: measuring tapes.
Objective: To reflect on favorite activities in the sun.
Have the children sit outside and write about or draw their favorite activity on a sunny day. Afterward, have them share their journal entries in small groups.
Materials: science journals or clipboard and paper, pencils; optional: colored pencils.
Objective: To think about ways the sun is important to us and to plants and other animals.
Give children a strip of yellow paper on which to write one thought about why the sun is important to them, or to plants or other animals. Or draw a sun on a whiteboard and then add the children’s ideas to it, like rays of the sun.
Materials: strips of yellow paper, tape or thumbtacks, bulletin board or poster, or whiteboard and markers.
A STEP BEYOND
Shadows and Shapes: As a rainy day option, show pictures of shadows and have students guess the object making them! Take your own photos or use Guess Whose Shadow? by Stephen R. Swinburne, Boyds Mill Press, 1999.
Group rotate and revolve:* Have children form a circle with one person in the middle to be the sun. The children will model being the Earth as it rotates and revolves around the sun. Have children rotate (turn towards their left hands) like the Earth on its axis. Then have them take baby steps forward, moving counterclockwise in a circle around the sun, while continuing to rotate (also counterclockwise) on their own axes. *This is best done outside on a soft surface. Keep it slow and controlled and only do for a limited time, since children can get dizzy.
Solar Ovens: Have children work together in small groups to design and build a solar oven, considering what they learned from the greenhouse and ice cube experiments. Test their designs with thermometers, or use the ovens to melt cheese or make a heated snack of their choice.