The Phases of the Moon

By Noreen Grice. Moon images taken by Vivian Hoette at Yerkes Observatory.

The Moon is one of the most recognizable objects in the sky. It is our nearest neighbor in space and about a quarter million miles away from Earth.

The Moon travels about the Earth, completing one trip in about a monthís time. During the month, we see the Moon appear to change shape; at times growing (or waxing) and other times shrinking (or waning). The different shapes of the Moon are called the Moonís Phases.

In this activity, you will learn to identify each phase and explore why the phases occur.

Procedure:

1. Locate the page that has the Moonís phases divided into eight boxes. Use scissors to cut along the broken lines so that you have eight little squares. One square will have no Moon. [You might want to glue these eight pictures to index cards to make them more sturdy.]

2. Mix up the pictures and try to arrange them in some kind of logical order. A small square in the upper right corner is a guide for the correct orientation.

3. Locate the page that has similar pictures of the Moon phases, as seen from Earth (Braille / print). Labels identify the names of the phases. Now letís compare your arrangement with a labeled version of the Moonís phases. How did you do?

4. Review the shapes of the Moon phases with their names. Notice that a Crescent Moon is shaped like a banana or a print letter ďCĒ. A Quarter Moon is shaped like a half Moon (but weíll learn in a moment, why itís called a quarter Moon). A Full Moon is a round Moon. A Gibbous Moon is bigger than a Quarter Moon but smaller than a Full Moon. A New Moon is not visible at all.

5. Next, locate the Moon Phase (orbit) diagram page (Braille / print). Here you will see an illustration of the moon, as it travels about the Earth during the month. Sunlight appears to come from the right side, as denoted by arrows. The large hollow near the center of the page is the Earth. The smaller solid circles represent the Moon.

6. Locate the New Moon. Notice that the New Moon is lined up between the Earth and the Sun. (The Sun is actually 93 million miles from Earth.) The Sunís light illuminates half of the Moon, but that half faces away from Earth so the Moon cannot be seen during New Moon phase.

Track counterclockwise to the Waxing Crescent Moon. Notice that there is now a slight angle between the Moon, Earth and Sun. Compare this diagram with the picture of the Waxing Crescent Moon, as seen from Earth. The sliver of visible Moon is illuminated by the Sun.

Continue counter clockwise to the First Quarter Moon. Using the New Moon as your starting reference, how far as the Moon traveled about the Earth? One quarter of its journey! Thatís why it is called the First Quarter Moon.

The next phase is the Waxing Gibbous Moon. More of the Moon is illuminated by sunlight as the angle between the Earth, Moon and Sun has increased.

When the Moon is in its Full Moon stage, the Earth is now located between the Moon and Sun. Observers on Earth see a round Moon. The full Moon rises when the sun sets so it can be seen all night long.

The Moon now begins waning and we come to the Waning Gibbous Moon.

Next is the last quarter Moon. If you track from New Moon counter clockwise to Last Quarter Moon, you will discover how much of the orbit the Moon has traveled. Some people also call this the Third Quarter Moon. The Last Quarter Moon rises at midnight and sets at noon, so itís a Moon that can be seen during the daytime.

The Moon continues waning and several days later we see the Waning Crescent Moon. This crescent Moon rises before dawn.

Finally, the Moon returns to the New Moon phase and the cycle begins all over again!

Compare the Moon Phase (orbit) Diagram with the Moon Phase Chart to help you remember what the Moon looks like and where it is, during each phase!