Experimenting with rotation, revolution and identifying geographic locations.
FIRST GRADE - EXPLORING NIGHT AND DAY
The Solar System and all its planets are in constant motion. Each of the planets revolves around the Sun. The planets also rotate, or spin, around an internal axis. One manifestation of rotation is the cycle of night and day. Day after day, month after month, year after year, the alternation of night and day continues. Sometimes it is sunny outside, and other times it is dark. In addition to rotation, day and night occur because the Earth is spherical. When a portion of the Earth faces the Sun, it is daytime. When the same are rotates away from the Sun, it is nighttime. The cycle of light and dark is continuous except near the North and South Pole. During the Northern Hemisphere summer, the North Pole always faces the Sun, so daytime is continuous for several weeks. At the same time, the South Pole faces away from the Sun (Southern Hemisphere winter) and is in continuous night.
The origin of night and day is very difficult for children to understand. The idea that the dark side is really a shadow of the planet as it rotates away from the Sunís rays is difficult to imagine. The rotation of the Earth on its axis, is also not easy to understand, because we cannot feel this motion.
Light rays from the Sun touch only the side of the Earth that is facing the Sun. While the Earth is spinning on its axis, it is also revolving around the Sun. The Earth is always rotating, spinning eastward. We do not sense this motion, however, because everything else on the Earthís surface is moving as well. There is no independent frame of reference for observing rotation. Viewed from space, however, the Earth is clearly spinning. A point on Earth takes 24 hours to complete one rotation and come back to its starting point. The Earth spins completely once in 24 hours or in 1 day. The axis is the internal line around which the Earth rotates. The axis is tilted 23.5o from an imaginary vertical line drawn through the Earth.
Light rays from the Sun touch only the side of the Earth that is facing the Sun. While the Earth is spinning on its axis, it is also revolving around the Sun.
To illustrate rotation and revolution, draw the following pictures on the
board. Explain that the Earth rotates on its axis, but revolves around the
Sun at the same time. Explain that night and day is caused by rotation,
and that the seasons are caused by the tilt of the axis and the revolution
around the Sun . (see animation on top)
. (see animation on top)
2. Have the students stand up, and rotate or spin. Make sure they understand that this is rotation.
3. Have students work in pairs. Have one student revolve around the other. Explain that this is revolution.
4. Tell the students that the Earth rotates as it revolves around the Sun. Ask them to figure out what these motions will look like, using one pair of students. Donít let them do these activities for too long or else you will have many dizzy students!
5. Have the students look at the earth ball and have them show you rotation on an axis. Go over north and south balls.
6. Have students show you revolution around the Sun, if the Sun is the flashlight.
7. Explain why the Earth has night and day. Divide the students into groups of two. Give each group a flashlight. Instruct them to think about creating day and night. Have one student be the Sun by holding the flashlight. The other student is the Earth (Earth Ball).
8. Go through locations on the Earth Ball. Have them find United States, Africa, South America, and whatever it takes for them to locate themselves on the globe.
9. Ask the students to create day in the United States, then night. If one country is day, which country is in night? Go through as many locations as it takes for the students to understand the concept of day and night.
10. What causes day and night? The shadow from one side of the Earth.