第14章 Lesson 14: Moon Mystery

On a clear night, go outside and look for the Moon. Do the same thing a week later, and the moon will look different. It is the same, rocky sphere that has been circling the Earth for millions of years, so why does it always seem to change shape?

Sometimes, the Moon illuminates the night sky. Other times it is just a sliver of white. Sometimes the Moon is visible during the day. Other times it is not visible at all. These are called the phases of the Moon. They happen because the Sun, the Moon, and the Earth are always moving.

One thing that almost never changes is that the Sun shines on one side of the Moon. Because we live on the Earth, the Moon's appearance changes depending on much of the illumination we can see. For example, a full moon occurs when the Moon and the Sun are on opposite sides of the Earth and we are able to look directly at the lighted side of the Moon.

A new, or dark moon happens when the Moon and the Sun are on the same side as the Earth. In this case, we are looking directly at the dark side of the Moon that is facing away from the Sun and in shadow. The other phases occur as the Moon orbits Earth and we see more or less of the illuminated half. A half-moon is when the Moon is to the side of the Earth, and you can see equal amounts of the lit and unlit halves.

A lunar eclipse is the only time when the Sun's light is prevented from reaching the Moon. This occurs when the Sun, the Moon, and the Earth are in a straight line with Earth in the middle. As the Moon travels into the darkness of Earth's shadow, it looks like all or part of it disappears.

A solar eclipse is a little different. It happens when the Sun, the Moon, and the Earth are lined up, but the Moon is in the middle. The Sun is much larger than the Moon, but it is also much farther away. This makes the Sun and the Moon appear to be the same size. When the Moon's path goes in front of the Sun, it temporarily blocks the Sun and causes a solar eclipse. A solar eclipse is much more rare than a lunar eclipse.

Many scientists believe that the Moon was once part of the Earth. Millions of years ago, something crashed into Earth and broke off a large section of the planet. This may be true, because the Moon is made of the same material as Earth.

I. Word List

sphere: shaped like a circle

illuminate: to make something bright

unlit: dark

lunar: moon

solar: sun

II. Vocabulary skills—Find the correct words in the reading.

1. different stages: p _ _ _ _ _

2. stopped from happening: p _ _ _ _ _ _ _ _

3. a short time: t _ _ _ _ _ _ _ _ _ _

4. a little different: s _ _ _ _ _ _ _

5. hit very hard: c _ _ _ _ _ _

III. Reading skills—Answer the following questions.

1. How are lunar and solar eclipses similar?

___________________________________________________________.

2. How are lunar and solar eclipses different?

___________________________________________________________.

3. Why are there different phases of the Moon?

___________________________________________________________.

4. Which is bigger, the Sun or the Moon?

___________________________________________________________.

5. Why do many scientists think the Moon used to be part of the Earth?

___________________________________________________________.

IV. What are the missing letters? Fill in the blanks for each word.

1. ec _ _ _ se 4. l _ _ ar

2. s _ _ ere 5. s _ _ ar

3. illu _ _ _ ation 6. s _ _ _ _ tists