re: "Really, as a matter of fact, it's all dark..."
It doesn't take a rocket scientist to know that when we see a full moon, it's dark side is exposed to the darkness of space, while what we see is exposed to sunlight.
Obviously during a 'new moon', the dark side is exposed to sunlight and we see nearly nothing of our moon because there's no sunlight shining on it due to that entire face of our moon pointing at our direction, as in away from our sun.
