Grade 3 Science
Core Unit : The Solar System

Part 1.
Ask the students to close their eyes and imagine that it is very early in the morning, before sunrise. They are outside standing in an snowy field. Christmas will be here soon and the air is crisp and clean. They are facing south and looking straight ahead. After a minute or so, streaks of reddish light flood across the meadow. From what direction are the sunbeams coming? How would they have to move their head or their eyes to see the rising sun?

Now it is noon. They are back standing in the snowy field, facing south again. How would they have to move their eyes or head to see the sun?

Finally it is almost supper time. They have come back to the field one more time. The sun is setting. If they once more stand facing south,how will they have to move their eyes or turn their head to see the setting sun? How does that direction compare with the morning, and at noon?

Ask the students to check this out at morning, noon, and evening tomorrow.

Part 2.
On a piece of heavy corrugated cardboard at least 1 m by 1m, make an arrow from masking tape, or with a felt-tip marker. Label the arrow as pointing south. The other directions can be marked, too. Place the cardboard on the floor near the centre of the back wall of the classroom, and orient it so that the south arrow points toward the right hand wall of the classroom as one looks toward the front. (A student might sit in a rotating chair rather than stand on the cardboard. In this case put the arrow on the seat or arm of the chair so that it faces the front edge.)

Have one student stand on the cardboard facing the direction of the south arrow and another student stand at the midpoint of the left hand wall of the classroom holding a flashlight shining toward the student on the cardboard. Turn off the lights in the room and close the curtains, if possible.

Imagine that the cardboard (or chair) represents the Earth, the arrow of tape points south, and the flashlight reflector represents the Sun. Ask the student on the cardboard to stand with legs straddling the tape, looking straight ahead in the direction the tape points, south. Daytime is when the sun shines on the student's face. It is early in the morning and the sun is not up yet. Slowly start to rotate the cardboard counterclockwise on the floor. Have the student on the cardboard indicate as soon as the flashlight reflector becomes visible using peripheral vision. The student's head should not turn from looking the same direction as the arrow. Use the reference tape on the rug to determine in what direction the Sun would first become visible.

Continue to rotate the cardboard and stop when the tape is pointing towards the front wall of the classroom. From which direction is the Sun visible now? Has the Sun moved? Has the Earth rotated? Continue rotating the cardboard until the tape is pointing at the flashlight. At what time of day is the Sun in the south? Continue rotating the cardboard until the flashlight has almost disappeared from the field of view of the student on the cardboard. In what direction is the flashlight from the cardboard? What does this represent? What fraction of a full rotation has the cardboard gone through since the beginning? Continue turning the cardboard for another quarter turn. What time is represented now?

Turn back to the beginning direction. This represents the rotation of the Earth for one complete day. Stress that the Earth has rotated but the Sun did not move. The Sun appeared to move from east to west through the field of view of the observer who was always facing south. Discuss the ancient belief that it was the Sun which moved across the sky. Does it still seem like the Sun moves? You might want to mention the legend of Apollo. Apollo was the Greek god whose job it was to drive the chariot of the Sun across the sky each day.

When the person in the middle calls out "rotate" the people in the circle must spin slowly on the ball of one foot in a counterclockwise direction. When the centre calls out "revolve" the people in the circle walk slowly in a counterclockwise direction. If "revolve and rotate" are called out, the circlers must both spin on the their feet and move slowly in a counterclockwise direction. When "stop" is called, the circlers stop in exactly the direction they were facing when the call went out. The centre will then call either "time" or "season."

If "time" is called, each circler must determine the time of day, based on the direction each is facing. If stop is called when one is facing directly away from the Sun, the time is midnight. If facing toward the Sun, the time is noon. Intermediate directions produce times between those. The 24 hour clock could be introduced to allow estimation of these times, or the A.M. and P.M. designation could be used.

If "season" is called, each person must turn to see where the midsummer marker is, and figure out the season from there.

After a suitable pause for reflection on the answer to the call for time or season, the centre person should call the name of one person in the circle, who will give the answer. The rest of the circlers and the person in the centre can evaluate that answer.

The moonrise is a phenomenon similar to sunrise. When the Earth rotates so that the Moon comes into view, the Moon appears to rise. (Use the rug activity (#2) to illustrate this. Hold a tennis ball in the back corner of the room opposite the flashlight, or any other position along the walls for the phases. This can also be illustrated with a globe and a tennis ball for the Moon and a flashlight for the Sun. At the grade three level, students are expected to understand only the concepts of new moon and full moon.

A full moon occurs when the Moon is on the opposite side of the Earth from the Sun. At full moon, the Moon appears to rise (comes into view) when the Sun sets. New moon occurs when the Moon is on the same side of the Earth as the sun. Since it is on the same side of the Earth as the Sun, the new moon rises when the sun rises and is visible all day long, setting in the evening. Between new moon and full moon is called the waxing crescent moon. After full moon comes the waning crescent moon, which lasts until new moon.

Planet	Mercury	Venus	Earth	Mars	Jupiter	Saturn	Uranus	Neptune	Pluto
Distance	6 cm	10 cm	14 cm	22 cm	74 cm	136 cm	280 cm	428 cm	562 cm

Using the information they have obtained for each planet, the students could produce television or radio ads promoting tourist travel to one of the planets, and present them to the class or to other classes. A science fair project could be to 'simulate' a planet's environment, and then invite 'tourists' to visit.

This is an excellent opportunity to work on resource retrieval, including the use of periodical indexes. The unit can be planned with the help of the teacher-librarian.

Discuss with the students where the various constellations are in the sky, and how to recognize them. Schedule one night when they can come with their parents to a good viewing site, and together learn to identify planets and stars. Possibly some parents or other resource persons will have some expertise in this area. An astronomer or an astronomy teacher could be invited to talk to the group. Hot chocolate or some other refreshments will help make this night class more attractive.

If feasible, plan a field trip to an observatory in conjunction with this activity.