We all know that the Moon has different phases, but if you thought these phases had something to do with the shadow of the Earth (like many people think), you'd be wrong. Try this activity to see how the Moon's phases really work:
What You Do:
- Place a dot on the ball with the marker. This ball represents the Moon, and since the same side of the Moon always faces the Earth, keep the dot facing you (your head represents Earth).
- Place the lamp on a table in the middle of the room. Turn it on, and turn off any other lights in the room. The lamp represents (you guessed it) the Sun.
- Stand several feet away from the light and face it. Hold the ball at arm's length in front of you. If you place the ball directly in front of you, you just created a solar eclipse. But notice what happens when you place the ball above or below the light. The light strikes the back of the ball and you don't see any light on the side that's facing you. This represents the new Moon phase, which you might as well call the "no Moon" phase since you don't see the Moon at all.
- Turn a little bit to your left with the ball still at arm's length. You'll notice a small crescent of light on the right side of the ball. This is called the new crescent.
- Turn until the ball is half lit up. This is called the first quarter Moon. Even though the Moon is half lit, it's called the first quarter since the Moon has traveled one-quarter of the way around the Earth.
- Continue turning around the circle until you come 180 degrees (halfway around). At this point the whole ball should be lit. It's a full Moon. If your head's in the way, you just created a lunar eclipse. Raise the ball up some to see a full Moon.
- Continue slowly around the circle until you come back to where you started. Notice along the way the different phases shown on the following page.
What Just Happened?
When the Moon is one the opposite side of Earth from the Sun, the Moon appears fully lit. When the Moon is between the Sun and Earth, it blocks the sunlight and appears dark. During the 29 1/2 days it takes the Moon to revolve around the Earth, it will have different amounts of sunlight striking its surface every day. The amount of sunlight that we see reflected from the Moon's surface during any month is classified into the eight phases.
Excerpted with permission from Out-of-This-World Astronomy by Joe Rhatigan and Rain Newcomb (Lark Books, 2003)