1. Revolution and Rotation
Our Moving Planet
Revolution and Rotation

2. All of the planets in our solar system orbit, or revolve, around the Sun. Scientists pretend that planets and stars have a line drawn through their middles. This line is called an axis. Our sun spins around its axis just like each planet does. Spinning on an axis is called rotation.

3. Earth rotates on an imaginary line called an axis
Earth rotates on an imaginary line called an axis. The North Pole is at one end of the axis. The South Pole is at the other end. Earth’s axis is tilted, not straight up and down.

4. Night
Day
Sun
This is a globe. The stick through its middle is its axis. The globe spins around its axis. Planets don't have sticks through their middles. A planet's axis is an imaginary, or made-up line through its middle.

5. Earth rotates, or turns one complete time around the axis, once each 24 hours. We call this rotation day and night.

6. Every day, the Sun appears to come up and go down
Every day, the Sun appears to come up and go down. However, the Sun does not move past Earth. Instead, Earth turns, or rotates. As Earth rotates, different parts of Earth move through the Sun’s light and then out of the light. This causes day and night. One complete rotation takes 24 hours.

7. This is a model of the sun’s light as it strikes the earth.

8. Earth also revolves, or moves in a circular path around the Sun
Earth also revolves, or moves in a circular path around the Sun. The path that Earth follows around the Sun is its orbit. It takes 365 ¼ days for Earth to travel around the Sun.
One complete revolution is 365 ¼ days.

9. The Earth revolves around the Sun once a year
The Earth revolves around the Sun once a year. To revolve means to move its position around the Sun. Rotating is turning on an axis, revolving is moving around the Sun. The Earth makes one complete rotation every 24 hours. The Earth is both rotating and revolving all the time.

11. Because Earth’s axis is tilted, the North Pole and South Pole usually
do not receive the same amount of sunlight at the same time. This
causes the seasons. When the North Pole is tilted toward the Sun,
the Sun’s rays strike that part of Earth directly. When this happens, it
is summer in the northern part of Earth. When the North Pole is tilted
away from the Sun, the Sun’s rays do not strike that part of Earth as
directly. When this happens, it is winter in the northern part of Earth.
In summer, your part of Earth is tilted toward the Sun. This makes
the Sun appear high in the sky. In winter, the Sun appears lower in the sky.
North American Summer
North American Winter

12. Revolution and Rotation
Earth revolves once a year around the Sun.
Earth rotates once every 24 hours on its axis.
rotation
revolution
Earth is both rotating and revolving all the time.

13. Shadows show us that the Earth is changing positions.