I am curious as to why, as the moon goes through the different phases, do we see the visible part sometimes be crescent shaped, then as we get to the time that we 'see' only half the moon, it is no longer crescent shaped, but appears to be virtually bisected or straight across. I always thought that the earth was casting a shadow, which created the crescent that we see or said another way, the earth was blocking the light from the sun that was hitting the moon, which caused the crescent shape that we 'see'. If this is true, why is the visible part of the moon, as we approach being able to see half of it, no longer crescent shaped?