How Does the Earth Move?

Lesson Plan - Get It!

Audio:

When discussing the earth's movement, there are two important terms to know: rotation and revolution.

Rotation describes the way the earth moves on its axis, an imaginary line that goes through the center of the planet.

Revolution describes the circular motion the earth takes around the sun.

You can model these movements using a large ball such as a basketball, kickball, or soccer. Try to spin the ball on the tip of your pointer finger.

• Does this movement model a rotation or a revolution?

If you answered rotation, you are correct.

Next, hold the ball with both of your hands. Move the ball in a circular motion by moving your arms.

• Does this movement model a rotation or a revolution?

This movement is modeling a revolution.

The earth is constantly rotating on its axis and revolving around the sun. Our calendars and measurement of time were created with these movements in mind.

It takes the earth 24 hours to complete one rotation (spinning on its axis), thus equaling a day. It takes the earth about 365.25 days to complete one revolution (to move full circle) around the sun.

• Have you noticed that February has an extra day every four years?

February 29 is known as Leap Day. Leap Days were created to account for the remaining time left over when the earth makes a revolution. In other words, it takes four years for that remaining time to equal one day.

• What exactly causes the earth to revolve around the sun?

The sun is the heaviest object in our solar system. It is more than 300,000 times heavier than the earth.

Most objects in space exert a gravitational pull. Since the sun is the largest object in our solar system, its gravitational pull is the greatest.

Therefore, other objects in the solar system revolve around the sun.

Continue learning about the earth's rotation and revolution with the following video.

Keep it going in the Got It? section!