Home> Our Star the Sun> The Little Moon 12. How Can the Little Moon Hide the Giant Sun? Exploring Size and Distance

 Summary of Activity: Students compare two objects at different distances. Students explore the concept that distance affects how we perceive the size of objects.

Duration of Activity:
40 minutes.

Student Prerequisites:
Students should have prior exposure to the topics of the Sun and the Moon through reading and class discussions and have a basic understanding of the relative locations of the Sun, Earth and Moon. They should also have practiced measuring the size and distance of objects.

Materials:

• Any large-format Big Book
• Rulers
• Balls measuring 3/4-inch and 1 1/2-inch (a ping-pong ball works well for the large ball)
• Pencils
• Work sheet to record observations

Teacher Background Information:

• The Sun is approximately 93 million miles from Earth. A car going 60 miles an hour would take about 177 years to reach the Sun from Earth.
• The Moon is much closer to the Earth. The distance is less than 240,000 miles. A car going 60 miles an hour would take about 5.5 months to reach the Moon from Earth.

Teacher Preparation:
Allow time to locate spheres of various sizes and to print out student work sheets.

Work Sheets:

 "Little Moon Giant Sun" Work Sheets Need help? View Completed Student Work Sheets

Objectives:

Students will learn that
1. Distance affects how we perceive size.
2. The further an object is from us, the smaller it looks to us.
3. The Sun and Moon have different sizes, but can appear to be the same size because of differing distances from the Earth.

Procedure:

Procedure: Part One

Whole Class Introduction

1. Distribute rulers to students.
2. Ask for a student volunteer to hold up a big book in front of the class.
3. Select three students--one at about 3’, 10’ and 20’ from the front of the classroom.
4. Ask each student for the height measurement of the book. Explain that to measure, students should hold ruler vertically at arm's length and close one eye.
5. Write measurements on the board.
6. Ask students why they think the big book looks so small. Ask why it looks even smaller from the back of the room.
7. Ask if they can think of other things that sometimes look small but are really big.
8. Explain that they will do an experiment and try to figure out why big things can look small to us.
9. Explain that they will get a big ball to represent the Sun, a small ball to represent the Moon, and they will be representing the Earth in this activity.

Procedure: Part Two

Hands-on Group Activity

1. Tape a 4-inch length of masking tape parallel to the edge of the table, creating a slightly rough surface to keep balls from rolling off the table.
2. Distribute two balls and work sheet to students.
3. Have students set the two balls side-by-side on the tape.
4. Ask students to kneel down at eye-level with the table surface and look at the balls with one eye closed.
5. Ask them to predict how many inches they will move the big ball toward the middle of the table in order for it to appear the same size as the small ball. Students record predictions on work sheets.
6. Explain to students that they will check their predictions by doing an experiment. Remind them that the big ball is like the Sun, the small ball is like the Moon, and they are the Earth.
7. Ask students to again kneel down at eye-level with the table surface and look at the balls with one eye closed. Compare the sizes of the balls. Ask students which looks bigger.
8. Keep the small moon ball at the table edge and ask students to move the big Sun ball until it looks the same size as the small Moon ball.
9. Measure the distance moved and record on work sheet.
10. If working in pairs or groups, have students alternate roles as they do this activity so that each student gets a chance to move the balls, measure, and record the distance.
11. Complete the work sheet.

Whole-class discussion:

• What did you notice as you moved the ball away from you?
• How did you make the balls look the same size?
• What happened during your experiment if you moved the big ball away from you and then rolled the small ball in front of the big ball?
• Explain that this is what happens during a solar eclipse when the small Moon moves in front of the large Sun and blocks the sunlight from viewers on Earth. Explain that the Sun is very large, but looks small to use because it is so far from the Earth (approximately 93 million miles). The Moon, while much smaller than the Sun, can look to be the same size as the Sun because it is so much closer to us (less than 240,000 miles).

Assessment:
Use the "The Little Moon" work sheet to assess your students’ work.

Bibliography:
See related books and websites.

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