Besides rising and setting, casual observation of the moon shows that it is invo

Question

Besides rising and setting, casual observation of the moon shows that it is involved in another motion in the sky. Describe how you* would detect this motion in nature. Your answer should discuss an experimental design (words/drawing) that would quantify the observed motion. Express your answer as an angular velocity statement. *Note: Do not consult a book answer.

A finger held at arm's length is about four times the apparent width of the moon or sun. Since both of these objects cover about half a degree of sky, one finger corresponds to an angle of about 2o. A fist (with the thumb held outside) will cover an angle of 100. We'll call this angle a fist. A spread hand--from the tip of the thumb to the tip of the little finger, again at arm's length, covers about twice the angle of a "fist", or about 20o. Let's call this angle a span. With the help of fingers, fists and spans, it is relatively easy to estimate angular distances in the sky. More information about this can be found at:

http://oneminuteastronomer.com/860/measuring-sky/

Solution Description:

1) Moon’s velocity =_______________ degrees/day

2) How long will it take for the moon to orbit the earth? ________________

(Show work)

3) Why do you have to report this observation as an angular measurement?

Explanation / Answer

The moon is moving around the Earth in appproximately in a circular orbit, going once around us in a 27.3 days.

One circle is 360 degrees.

So the moon moves, 360/27.3 or 13.2 degrees per day

It is about 27.3 days to complete 1 orbital movement for the moon around EArth. It also takes approximately 27 days for the moon to rotate in its own axis. As a result for the observers from Earth looks like moon is still. Scientists call it as synchronous rotation.

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