Causes of Lunar Eclipses

Show the causes of lunar eclipses with our lunar and solar eclipse worksheets.

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Lunar Eclipse Worksheet

Objective: Explain the location of the sun, earth and moon during a lunar eclipse.

MatchCard: Download below.

MatchCard Information Pieces compare location of the moon and earth in relationship to the sun to explain the causes of lunar eclipses. Students identify total and partial eclipses and the umbra and penumbra.

Use the Lunar Eclipse MatchCard

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This is MatchCard #5 of the Astronomy Unit Study. Find more information on MatchCard Science below.

What Is An Eclipse?

A lunar eclipse is the alignment of the sun, Earth, and moon so that the earth blocks the rays of the sun from reaching the moon. In other words, the moon is in the Earth's shadow.

Only during a full moon can a lunar eclipse occur. And while the moon has 12 or 13 full moons every year, it's orbit only causes lunar eclipses about every six months. The rest of the time, the moon is circling high enough above the Earth that even in a full moon the light of the sun reaches it.

But when the orbit of the moon gets in the Earth's shadow on the side away from the sun, something mysterious happens.

Types of Moon Eclipses

There are two types of lunar eclipses that can be seen with the naked eye.

Total Eclipse
The most exciting is a total eclipse. With a total eclipse the moon hides in the darkest shadow behind the Earth. If you look at the moon during a total eclipse, you will see that it is a bright red or orange color. It must have been very scary to people in ancient times to see the moon turn a blood red color.

Where does the red come from? The red light is actually coming from the sun and passing through the Earth. Most of the colors of the white light spectrum are filtered out. But the red light passes through the Earth's atmosphere and makes the moon look red. It looks as if the Earth were one large pair of red sun glasses.

Partial Eclipse
A partial eclipse is also very strange. It looks as if a giant Cookie Monster took a big bite out of the moon.

How does that happen? You will have to do the demonstration below to help this make sense. There is the darkest deepest shadow of the Earth (the umbra) and a lighter shadow (the penumbra.) When the moon is partly in the umbra and partly in the penumbra a partial eclipse occurs.

Penumbral Eclipse
FYI: There is third type of eclipse called a penumbra eclipse. In my opinion, it isn't too exciting, but of course all astronomers should know about them. They occur when the moon passes through the penumbra shadow but not the umbra shadow. If you are looking at the moon from the Earth it looks pretty much the same as it does the rest of the time.

Demonstrate A Lunar Eclipse

Total Eclipse Demonstration

Lunar Eclipse Demonstration #1

The best way for a student to understand the causes of a lunar eclipse is to see a demonstration. You will need:

• a light source
• a globe or ball to represent the Earth
• a tennis ball or other ball small enough to represent the moon

This is an easy demonstration. Shine the light on the Earth and watch as the moon passes into the shadow of the Earth on the other side. Explain how the white light is filtered by the Earth's atmosphere so only red light passes through. Then the moon looks red.

Umbra and Penumbra Demonstration

Lunar Eclipse Demonstration #2

The umbra and penumbra can be demonstrate with many cone shaped light fixtures that shine the light into the room at an angle. If you don't have such a light fixture, you can make a paper cone and place it around a flashlight so the beams spread out.

Hold your hand, or the ball, or some other object in the light. You will notice there is a distinct dark shadow in the middle. There is a fuzzier, lighter shadow around the edges. Ask if they can explain why there is a dark and light shadow. The lunar eclipse diagram on the MatchCard may help them to articulate the answer.

More Activities for Lunar Eclipses

Pictures, Please

Look for colored pictures and videos of a lunar eclipse. You can see these with:

• Books
• Internet Image Search
• Youtube Clips

Watch A Lunar Eclipse

Check to see when the next Lunar Eclipse will be available in your area. Even if the next date is after you have completed the Astronomy Unit Study, it is still worthwhile to watch. Mark your calendar. Then get up and check out the blood red moon.

Vocabulary Fun

Eclipse

The word eclipse apparently comes from an old French word for darkness. The most common use of the word refers to either a lunar or solar eclipse. It is a noun.

We sometimes use eclipse as a verb, meaning “to make less.” “My mom’s fear of spiders in the woods was eclipsed by the 80 foot python in the branches above her head.”

Lunar

Lunar is another word for moon. Have you heard of these words that come from the same root:

• Lunatic
• Lunacy

In previous centuries it was believed that mental illness was caused by the moon. Even today, many medical personnel will tell you that during a full moon there are more admissions to hospitals and mental health units, as well as visits to emergency rooms.

Solar Eclipse

Solar Eclipse
Compare Solar vs Lunar Eclipse with MatchCard #6.