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Calculate how fast the earth rotates in this simple science experiment

Suitable For

Grade 7



Time Required

 <12 Hours



What’s it about?

You’ve lived on Planet Earth all your life, but how much do you really know about the ground underneath your feet? Various forces exist in nature that we are unable to see or feel. One such force is the force of the earth spinning at a tremendous speed around its own axis. The speed of the earth is the greatest at the equator where the circumference is the most and moves the slowest at the poles. How fast does the earth rotate? Find out in the following science experiment:

Topics covered

Sidereal day

What will I need?

  • 3x PENCILS

Procedure (Method)

Unfortunately, this section is only available in the e-book version of the project.

How does it work?

Unfortunately, this section is only available in the e-book version of the project.

This science experiment works because the Earth rotates in a counter clockwise direction at a constant speed, making a full rotation every 24 hours. When located at the north pole the earth rotates towards the east. As the earth turns, the light from the sun hits the pencil from a different direction. The angle between the initial shadow line position and the shadow line position after two hours, indicates the angular distance the earth turns in two hours which is about 30 degrees (the angle may vary slightly depending on your position on the earth). Because the Earth turns about 30 degrees in two hours, we can deduct that it makes one full rotation of 360 degrees in 24 hours (24 hours in a day, divided by 2 = 12 and 12 X 30 degrees = 360 degrees).

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