Astronomy Assignment 2

The Rotating Earth

Try the following activity, which comes from page 61 of the second edition of KUHNís In Quest of the Universe.

Recommended props

Copy of December and March Star Maps from rear of KUHNís book; a few friends and beer or other refreshment.


The Assignment

On a clear dark night, find a good observing location and draw a quick sketch of some stars high over your head. Look for a pattern so that you can remember these stars later. If you can, mark your map so that it shows which stars are toward the north, east, south, and west.

Take about two hours off, and then go back to your observing location and find the stars you drew. How has their position changed? You probably know what this answer should be from the lectures. Your real job, however, is to stand under the stars and imagine that their motion is due to the rotation of the Earth. Try to "feel" the Earth turning under the stars. Which is easier to imagine, the stars on a sphere rotating around the Earth or the Earth spinning under the stars?

Finally, spend a half hour watching either at sunrise or at sunset. Or better yet, watch the Moon rise or set, particularly when it is full or nearly full. Now picture this phenomenon as explained by the heliocentric system. Try to think of the Earth turning instead of the Sun or Moon moving. Imagine yourself on a little ball that is turning so that the place where the Sunís light hits the ball changes.