Journal questions for week 7.

Due Tues. March 9.  Please answer in complete sentences and include a discussion of the questions' contents.

1. How do we know that there are two types of electric charges?  Describe an experiment/demo.
2. Describe what causes the crescent moon that is sometimes seen soon after sunset in the western sky.
3. How do we know that the crescent moon is not caused by the earth's shadow?  Hint: consider the moon's position relative to the sun and the earth for the moon to enter the earth's shadow.
4. What causes the sun's daily motion in the sky to be tilted relative to the horizon?  Hint: it is not caused by the tilt of the earth's axis.