 Activity

# Building a Model of the Earth and Moon

## This simple model, allows the student to build a model of the Earth and the Moon accurately representing their relative sizes and to gauge the relative distance

Students with visual impairment (as well as sighed students) often struggle to grasp the relative size of the Moon and the Earth and the distance between the Earth and the Moon.  A majority of students greatly underestimate the distance between them.

This simple model, allows the student to build a model of the Earth and the Moon accurately representing their relative sizes and to gauge the relative distance between the two celestial bodies utilizing this model.

It would be appropriate as an introduction to the Sun-Earth-Moon System or after initial instruction has occurred.

### Materials

• 2 small paper clips per student
• clay or playdoh
• 1 basketball per each group of 2 students
• 1 tennis ball per each group of 2 students

### Preparation

• For each student, take one paper clip and unbend it.  Form the metal into a square.

### Procedure

• Introduction: If this activity is used as an introduction, ask the students what they already know about the Moon.  Discuss.  Ask about the size of the Moon.  Do they think the Moon is smaller, larger, or about the same size as the Earth.  Discuss.  Students may know about gravity on the Moon versus Earth. Ask the students why the Moon has much less gravity than the Earth (much less mass).  Discuss.
• Pre-teaching:  Some students may not understand the concept of diameter.  If this is the case, pre-teaching using a raised line or large print circle may be necessary prior to this activity.
• Tell the students that in this activity they will build a model of the Moon and Earth using clay to better understand how large the Earth is relative to the Moon.

#### Relative diameter

1. Give each student a lump of clay or playdoh, 1 paper clip, and 1 paper clip formed into a square (See Preparation.)
2. The Earth:  Students will make a sphere to represent the Earth that has a diameter the size of the distances between the sides of the square which is made of the unbent paper clip.   (1″) See picture above. The model of the clay with small paper clip used as a guide for size
1. The Moon: Students will make a smaller sphere to represent the Moon that has a diameter the size of the small paper clip.  When they have built this sphere, it should fit between the paper clip.  (1/4″) See picture
2. After students have built both models, discuss the relative sizes and diameters of the Earth and the Moon.  Tell the students that the diameter if the Earth is 4 times the diameter of the Moon.  Earth’s diameter is approximately 8,000 miles while the diameter of the Moon is approximately 2,000 miles.  Are the students surprised at how much greater a diameter  the Earth has than the Moon?
3. Tell students that if you lay four Moons end-to-end, they would fit in the Earth from one end to the other.

#### Relative Distance between the Earth and Moon

• The distance between the Moon and the Earth is often assumed by students to be much less than it actually is.  Discuss with the students how far they think the Moon is from the Earth.  Show students the basketball (model of Earth) and the tennis ball (model of the Moon).
• Place the students in groups of 2 and give each group a basketball and a tennis ball.
• Have them stand up and discuss how far away they think the Moon (tennis ball) would be from the Earth (basketball). Have one individual stand with the Moon (tennis ball) at the distance they have estimated from the Earth (basketball).  Measure this distance with a trundle wheel.
• Discuss whether these distances were smaller or larger than the relative distance should have been (about 7 meters).
• With the entire class, walk a distance of 7 meters using the trundle wheel.
• Explain that the Moon is 33 Earth diameters away from the Earth. For math whizzes that is 8,000 X 33.  Allow someone to estimate   240,000 miles

#### Closure:

• Ask the students how far away the Sun would be using this model.   They will likely know that it would be very far away.
• If time allows, walk 280 meters with the trundle wheel.  Explain to the students that we have traveled only 10% of the way to the Sun given this model.  We would need to walk 2,800 meters to arrive at the Sun.  Actual distance to the Sun is 150 million km.

### Variations

• eTouchSciences has a very engaging app for use with the Novint Falcon haptics device which allows students to “feel” the weight of a bowling ball on the Moon, the Earth, and several other planets.  This would tie in well with the content in this activity if this device is available.
• For students who have the math background, relative volume can be calculated based on the relative diameters of the Earth and the Moon.

### NGSS Standards

Middle School: Space Systems

• ESS1.B: Earth and the Solar System: The solar system consists of the sun and a collection of objects, including planets, their moons, and asteroids that are held in orbit around the sun by its gravitational pull on them. (MS-ESS1)

Middle School Engineering:  Systems and System Models

• Models can be used to represent systems and their interactions. (MS-ESS1-2)

This model was adapted from The Arkansas Leadership Workshop “Hands-On Astronomy”  headed by Linda S. Shore, 2008

The activity was adapted by Jim Clark.

Pictures by Ditmar Hospitál

By Laura Hospitál