How can we predict how the Moon will change appearance from day to day? (why does the moon phase get brighter in each position?)
Student 1: "The Moon appears to get brighter from picture 1-4 because the moon is orbiting into certain positions and the sun illuminates half of the moon and we see as much as the half is illuminated from earth. We can predict how the Moon will change appearance by knowing when the moon's orbit finishes and starts again."
Student 2: "We can predict how the Moon will change appearance by knowing where it is in orbit."