Below is a diagram of the earth-moon system. You can drag the moon in its orbit around the earth. The moon and earth are illuminated by the sun shining from the lit side of the moon.
Each time you press "NEW SUN ANGLE" the sun is given a new random direction (different time of year) and the moon phase in lower right is given a new random phase (different time of the month).
Your job is to orient the moon in its orbit around the earth so that an observer on the earth will see the moon phase of the lower left.
Press "TEST YOUR POSITION" to see if you get the phase correct. The phase according to your moon's position will be displayed in lower right.
Repeat the “NEW SUN ANGLE” until you consistently get the correct answer.
Animator Physlet developed by Wolfgang Christian and Mario Belloni of Davidson College.
Script written by Donald Collins of Warren Wilson College. Funded in part by the Appalachian College Associan, Teaching and Technology: Stage II, Andrew W. Mellon Foundation.