Classroom Activity

Model a Solar Eclipse

A person holds out a foam ball attached to a pencil and partially covers a basketball held by another person in the distance.

Overview

Students use simple materials to model the basics of a partial, annular, and total solar eclipse.

Materials

Large (1-3 feet in diameter) yellow circle or ball to represent the Sun OR a projected image of the Sun

1-inch or 2-inch foam balls OR any small balls, one per student

Pencils, one per student

Management

The relative sizes of the yellow circle or ball and the foam balls can vary depending on the size of the room and number of students.
If foam balls are not available, any spherical substitute will work, including aluminum foil balls.
For young students, insert pencils into the foam balls before distributing them.
For older students, introduce the lesson by asking students if anyone has ever seen a lunar or solar eclipse. Ask them what causes eclipses. Then, start the lesson at Step 8 below.
Important safety note! Remind students that they should never look directly at the Sun as it could damage their eyes.

Background

A solar eclipse occurs when the Moon passes between Earth and the Sun, fully or partially blocking the Sun's light from our perspective. Because Earth’s orbit around the Sun and the Moon’s orbit around Earth are not perfect circles, the distances between them change throughout their orbits. During a total eclipse, the distances are such that the Moon covers all of the Sun's disk area.

When the Moon is farther from Earth during an eclipse, it leaves a glowing ring of sunlight shining around the Moon, resulting in an annular eclipse.

Two side-by-side images of the Sun show an annular eclipse on the left, in which a glowing ring the Sun's disk surrounds the black silhouette of the Moon. On the right, a total solar eclipse shows the Sun fully blocked by the Moon.

Photos of an annular total solar eclipse (left) and a total solar eclipse (right). Credits: Left, Annular Eclipse: Stefan Seip (Oct 3, 2005). Right, Total Eclipse, NASA/Aubrey Gemignani (August 21, 2017) | + Expand image

Sometimes the Moon blocks only a portion of the Sun, creating a partial eclipse that appears like a bite has been taken out of the Sun’s disk.

A series of three images show the Sun being progressively more eclipsed by the Moon from left to right.

The Sun appears partially eclipsed in this series of photos taken from NASA’s Johnson Space Center in Houston on August 21, 2017. Credit: NASA/Noah Moran | + Expand image

Procedures

Ask students for their prior knowledge about the Moon and eclipses.
Ask students if they’ve ever used their hand to block sunlight. Have students demonstrate how they do this, inside the classroom, pretending the lights are the Sun.

Step 2. Image credit: NASA/JPL-Caltech | + Expand image
Ask students if they’ve ever used anything else to block sunlight. Depending on their answers, ask if they’ve ever used a visor or ducked behind a tree or building to find shade.
Show students the yellow circle or ball and explain that we are going to pretend this is the Sun.

Step 4. Image credit: NASA/JPL-Caltech | + Expand image
Have students pretend they are using their hands to block the Sun’s rays.

Step 5. Image credit: NASA/JPL-Caltech | + Expand image
Ask students what objects they have seen in the sky during the day or at night. Accept all reasonable answers.
Ask students if any of those objects would be able to block the Sun. If available, hold up toy examples of objects that they’ve named, such as an airplane or bird. If they haven’t already mentioned the Moon, ask if the Moon might be able to block the Sun.
Distribute the foam balls and pencils, instructing the students to insert their pencil into their foam ball. Explain that the foam ball represents the Moon.
Ask students to hold up their Moon to try to block the yellow circle or ball representing the Sun.
- Does the Moon block the Sun entirely?
- If not, what do they need to do to fully block the Sun?
Have students stand up and form a circle or semicircle around the Sun. Have them move closer to or farther from the Sun and change the distance between the Moon and their head as needed so that the Moon will block the Sun.
Discuss with students what happens when the Moon partially and fully blocks the Sun. What do we see from Earth? Explain that we call it a solar eclipse when the Moon blocks either all or part of the Sun.
Explain to students that their head represents Earth in this model. Show students how the Moon orbits Earth, and have them practice orbiting. Note: the Moon orbits Earth in a counter-clockwise direction as viewed from above the north pole.
Have students continue to model the Moon’s motion until they return their Moon to the position where it totally blocks the Sun. Explain that this is what happens during a total solar eclipse.

Step 13. Image credit: NASA/JPL-Caltech | + Expand image
Have students model a partial solar eclipse by positioning their Moon so that only part of the Sun is blocked.

Step 14. Image credit: NASA/JPL-Caltech | + Expand image
Explain that everything has to be lined up just right for a solar eclipse to occur. Explain that sometimes the Moon's orbit takes it slightly higher or lower than where the Sun appears in the sky. Have students model this. If the Moon is higher or lower, does it block the Sun?

Step 15. Image credit: NASA/JPL-Caltech | + Expand image
Have students walk toward the Sun. Does the Moon still fully block the Sun? Have them walk forward until the Sun leaves a thin ring around their Moon. Explain that what they are seeing is known as an annular eclipse and can occur when everything lines up just right, but the distances are not far enough for the Moon to totally block the Sun.

Step 16. Image credit: NASA/JPL-Caltech | + Expand image

Discussion

What do we see from our perspective on Earth during a total, partial, or annular solar eclipse?

Assessment

Students should be able to model a partial, annular, and total eclipse.

Extensions

Set up a light to represent the Sun, similar to the setup for the Moon Phases lesson. Have students model a total solar eclipse with this setup.
Have students model a lunar eclipse – when Earth comes between the Sun and the Moon.
Check for future eclipses and learn how to safely observe a solar eclipse. Note that this involves either setting up a pinhole camera or securing a class set of eclipse glasses.