Why does the moon chage its shape?

Answer 1

Contrary to popular belief, the phases of the moon throughout a typical month have nothing at all to do with earth's shadow. The earth's shadow passes over the moon only at the time of full moon, and only rarely does it do that. The various phases of the moon that we observe come about because we are actually seeing the long lunar day (it is equal in length to the moon's phase cycle-- one synodic month) pass over the face of the moon that we can see from earth. It's odd to think of the moon going through a day, but as the moon orbits around earth it stands to reason that we will see the moon changing its relationship with the sun. Sometimes we will see the sun shining more on the face we can see, and sometimes we will see the sun shining on the moon at different angles.