What causes the phases of the moon?

Question

I've always wondered about this, and nobody's been able to explain it to me so that I can understand it. I'm really confused, and I really just want to understand it. Thanks in advance!

Answer 1

Make an experiment, to understand better: in a dark room, point a flashlight at a sphere (e.g., Earth globe). Keep the flashlight fixed, and move around the globe. You can see only the illuminated part of the globe; as you move around the globe, you will see a larger or smaller portion of the globe being illuminated, you see the most when you are almost between the flashlight and the globe, and the least when the globe is between you and the flashlight.

Now imagine that you are the Earth, the flashlight is the Sun, and the globe is the Moon...

Answer 2

All have been good answers for the most part, but they still sound a bit too scientific, which is a sticking point for most people, just like understanding what your tax instructions say.

I'll put it as simple as possible(no offense meant by that at all), when you look at the moon, the dark part you see is the moon's shadow. A lot of people think it's the Earth's, but it's not, otherwise it would be an eclipse.

So as the moon orbits the Earth, more light is seen because it is moving to the dark side of the Earth. The reason it's not always an eclipse at the point of a full moon is because the moon's orbit wobbles up and down across the Earth, so typically it is just higher or lower then the Earth, so the Sun's light is illuminating it completely.

Then, as it orbits more, you begin to see it's shadow again, because it is moving between the Earth and Sun for a "New Moon." Again, it's orbit is higher or lower then the Earth, so we don't always get an eclipse at that point.

On another interesting note, the reason we always see the same side of the moon, is because it rotates on its axis at the same speed as it orbits the Earth.

Answer 3

have your friend stand on one side of the room with a flashlight. you (the earth) hold a basketball in your hand and hold it out straight. as the moon revolves around the earth (21 days i think) it's just like you spinning around in a circle and watch how the light from the flashlight appears on the ball as you spin. IMPORTANT CONCEPT is the you spinning does NOT represent the rotation of the earth (24 hours) but the orbit of the moon. the rotation of the earth does not effect the phase of the moon. that's why the phase of the moon doesn't change as you watch the moon go across the sky. but as the moon orbits the earth, the light from the sun still hits the moon from the direction of the sun, and depending on where the moon is, determines how much of that light we see.
if your friend with the flashlight is on the north side of the room and you are on the south side and the moon is to the east, then you only get to see half of the light hittin the ball

Answer 4

To all intents and purposes the sun is a fixed point, and the moon moves. When we are between the sun and moon, it is full. When it is between us and the sun it is a new moon. (Not the same as an eclipse, by the way) Half way in between, we have half moons.

So, put simply, it is all about shadows.

Answer 5

This question is best answered visually. CHeck this link out for a better undertsanding.

Answer 6

Here is a good explanation of what happens.