Eclipses of All Kinds

Introduction

How does the alignment of the Earth, Moon and Sun cause an eclipse? How are the positions of the Earth, Moon and Sun different during lunar and solar eclipses? In this demonstration, a model is created illustrating the positions of the Earth, Moon and Sun during solar and lunar eclipses.

Concepts

• Eclipses
• Orbits

Experiment Overview

This demonstration will enable students to gain a better understanding of the different positions of the Sun, Moon and Earth during solar and lunar eclipses by presenting a model.

Materials

Safety Precautions

Although the materials used in this activity are considered nonhazardous, please follow all laboratory safety guidelines.

Prelab Preparation

Model Assembly

1. Using long nose pliers create a small loop at one end of the wire.
2. Carefully push the straight end of the wire through the center of the 1.5-inch diameter Styrofoam^® ball.
3. Bend the wire at a 90º angle at a point 1.5 inches above the top of the small ball so it hangs on the loop (see Figure 1).
   {14076_Preparation_Figure_1}
4. Carefully push the straight end of the wire through the center of the large Styrofoam ball.
5. Create a loop in the wire by wrapping the wire around a pen or pencil approximately 3–4 inches from the end of the wire.
6. Move the large ball along the wire so it rests on the loop, and bend the wire at a 90º angle at a point close to where the wire emerges from the top of the large ball. About 6 inches of wire should be between the two 90º bands (see Figure 2).
   {14076_Preparation_Figure_2}
7. Insert the end of the wire into the hole in the center of the wooden block.

Procedure

1. Find a fixed position for the model and light source to rest. The light source represents the Sun. The distance between them is dependent on the strength of the light source being used and the position of the audience.
2. To demonstrate a solar eclipse, grab the wire at a point between the Earth and the base of the model.
3. Slowly twist the wire so the Moon passes in between the Earth and the light source.
4. Instruct students to observe the Moon’s shadow on the Earth.
5. To demonstrate a lunar eclipse, repeat steps 1–4, but have the moon pass behind the Earth.
6. Instruct students to observe the Earth’s shadow on the Moon.

Student Worksheet PDF

14076_Student1.pdf

Teacher Tips

• Limit the amount of extra light in the classroom to improve visibility of the shadows.
• This demonstration model can also be used to model the phases of the Moon.

Answers to Questions

1. What does the large ball, small ball and light source represent in the model?

   In the model, the large ball represents the Earth, the small ball represents the Moon, and the light source represents the Sun.

2. How are the positions of the Moon, Sun and Earth different when comparing a lunar and solar eclipse?

   In order for a lunar eclipse to occur, the Earth must be located between the Sun and the Moon. A solar eclipse requires the Moon to be positioned between the Earth and the Sun.

3. Why is a solar eclipse only viewable in certain places on Earth?

   Solar eclipses are only visible in certain places on Earth because the Moon is smaller than the Earth; therefore, the Moon’s shadow only covers a small portion of the Earth at one time. (Note: The Moon is about 27% the size of the Earth.)

4. Consider the phases of the Moon as shown in the followng diagram.
   {14076_Answers_Figure_1}
   1. Why is a new Moon required for a solar eclipse to occur?

      During the new Moon phase and the full Moon phase, the Sun, Moon and Earth align.

   2. Why is a full Moon required for a lunar eclipse to occur?

      The alignment during the full Moon causes the Earth to obstruct the sun and cast a shadow on the Moon creating a lunar eclipse. The alignment during the new Moon phase causes the Moon to obstruct the Sun creating a solar eclipse.

5. How can astronomers predict both solar and lunar eclipses centuries in advance?

   Astronomers can predict eclipses using data collected about the orbits of both the Earth and Moon. In ancient times, eclipses were predicted based on that data. The position of both the Earth and Moon can be calculated for any future date including days when they will be aligned.

Discussion

An eclipse is caused by one heavenly object casting a shadow on another heavenly object. On Earth we observe two types of eclipses, lunar and solar. These two phenomena are created by different spatial arrangements of the Sun, Moon and Earth. A solar eclipse is the result of the Moon being positioned between the Sun and the Earth, while a lunar eclipse is the result of the Earth being positioned between the Sun and the Moon. It may seem as though eclipses should be a more common event; however, the orbits of the Moon around the Earth and Earth around the Sun are not on the same plane. The Moon’s orbit is at a 5-degree incline to the Earth’s orbital path around the Sun, which reduces the frequency of eclipses (see Figure 3).

References

NASA Eclipse Website. https://eclipse.gsfc.nasa.gov/lunar.html (Accessed December, 2016).