Earth's Bright Neighbor
Children ages 8 to 13 select from a variety of fruits to construct a scale model of the Moon, Earth, and Sun. After determining the correct sizes and distances for their models, they remove the Moon. They consider what it would be like if the nearby Moon were no longer reflecting the Sun’s light in the nighttime or daytime sky. Allow 30 minutes for this activity.
This model builds upon the concept that the Moon reflects sunlight, as explored in Mirror Moon. If desired, Mirror Moon may be conducted in a darkened room in conjunction with this activity.
What's the Point?
- Optional: Chalk or white board, or poster paper and markers to record the children's ideas
- One of each of the following fruits and other foods (listed from largest to smallest):
- (55"–wide) giant pumpkin or Halloween orange pumpkin garbage bag
- (4 1/2"–wide) large orange or cantaloupe or coconut
- (2"–wide) lime or kiwi
- (1/2"–wide) small grape or large blueberry
- (1/4"–wide) pea or navy bean
- (1/8"–wide) peppercorn
- (1/64"–wide) poppy seed
- Measuring tape
- Books about the Moon
- Art supplies, such as colored pencils, crayons, and markers
- 1 (1/2"-wide) small grape or large blueberry
- 1 (1/8"–wide) peppercorn
- Review the background information.
- Provide an open area where the children may spread out and work in pairs.
Facilitator's Note: Use the Exploratorium’s "Build a Solar System" online calculator to adjust the sizes and distances of your model to suit your needs. It is recommended that you select recognizable objects to represent the planets: e.g. a grape rather than a lump of Play-Doh. This will help make the experience more memorable for the children!
For additional ideas, see the lesson plan, How Far is the Moon, which uses a basketball and tennis ball to represent the Earth-Moon system. Or, build a scale model of the solar system through the Explore activity Jump to Jupiter.
- Optional: Provide a large indoor or outdoor space where the children can model the distance between the Sun and the Earth-Moon system, 491 feet or 150 meters (about three blocks). Plan to have an older child or adult helper place the pumpkin at that distance during step four in the activity, or you may wish to identify a marker that is three blocks away.
- If you do not wish to use food as a model, use the size measurements listed in the materials list to identify substitutes. If possible, select common household materials — the relative sizes of the Sun, Earth and Moon are more memorable if represented by familiar, standard-sized objects.
- Display several books about the Moon in a place where the children can page through them before and after the activity.
Facilitator's Note: The children may have many erroneous ideas related to the relationship between the Sun, Earth, and Moon, such as:
- The Earth is the center of the solar system. (The planets, sun and moon revolve around the Earth.)
- The Earth is larger than the Sun.
- The Earth is the largest object in the solar system.
These and other education misconceptions are listed at http://amasci.com/miscon/opphys.html by Operation Physics, an elementary/middle school physics education outreach project of the American Institute of Physics.
1. Assemble the children in a group and invite them to share their ideas about the size and distance of the Moon. Keep track of their ideas on poster paper, if desired. It is not important to correct the children's ideas, rather this activity should encourage them to explore and learn more.
- How big is it compared to Earth? Compared to the Sun or other familiar solar system objects?
- How long would it take to get there in a spacecraft?
- Have spacecraft visited the Moon?
- When did humans first visit the Moon?
2. Present the fruits and explain that the children will create a model of the Moon, Earth, and Sun.
- What's a model?
We use models to help us represent objects and systems so that we can study and understand them more easily. Motorized toy cars and dollhouses are examples of models. Their parts are the right sizes and spacing relative to each other. The models work basically the same way as the "real thing." Many video games model complex events and times or places that we can't really experience. The children are constructing "a scale model," which has smaller parts, but parts that are relatively the same size and distance to each other as the real Sun, Earth, and Moon.
- In this model, which fruit represents the Sun? The pumpkin.
- Which fruit represent the Earth? Answers may vary. Allow the children to discuss their ideas and propose which fruit represents Earth.
The Sun is 100 times wider than the Earth. Earth is represented in this model by a small grape or large blueberry.
- How big is the Moon compared to the Earth? Which of the other fruits would be a good representation of the Moon? Answers may vary. Allow the children to discuss their ideas and propose which fruit represents the Moon.
Earth is four times wider than the Moon. The Moon is represented by a peppercorn. The Earth is 7921 miles wide, and the Moon is 2159 miles wide.
3. Challenge the children to work in pairs to determine the distance between the Moon and Earth in the model. Provide the teams each with a small grape or large blueberry ("Earth"), a peppercorn ("the Moon"), and a ruler. Estimating is a way to engage the children. Reassure them that this estimate is just guessing and that you are not expecting anyone to know answers to questions for which they do not have any experience. You may need to remind the children that scale involves showing size and distance relationships accurately.
Share the answer: if the Earth was a grape or blueberry and the Moon was a peppercorn, they would be 15 inches (38 cm) apart at this scale. Explain that the models are 1 billion times smaller than the actual Earth and Moon. For example, it would take 1 billion grape-sized "Earths," placed side-by-side, to equal the actual width of Earth. The Moon is about 238,500 miles away from Earth. (It actually ranges from 225,600 miles to 251,800 miles in its orbit.)
- Does the answer surprise the children?
4. Challenge the children to work as a group to determine how far the Earth-Moon system is from the Sun at this scale. If possible, ask the children to estimate the distance outdoors. Have one child bring the pumpkin and represent the Sun; another holds the grape or blueberry "Earth," and a third holds the peppercorn "Moon." Bring a ruler. Invite the "Earth" and "Moon" to stand the appropriate distance apart. Have all the children work together to determine how far away the "Sun" should stand.
Share the answer: if the Earth was a grape or blueberry and the Moon was a peppercorn, they would be 491 feet or 150 meters (about three blocks) from the Sun. Have an older child or adult helper place the pumpkin 491 feet away and then return to the group, or identify a marker that is about three blocks away.
- Are the Moon, Earth, and Sun standing still like we have modeled them? No! Remind the children that the Earth is in motion as it orbits the Sun, and the Moon orbits the Earth.
- Is there anything else missing from our model? The other planets!: Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune.
- What is our model mostly made up of? Empty space!
- Remind the children of the Mirror Moon demonstration. How are we able to see our Moon among all that empty space? It reflects the Sun’s light.
Facilitator's Note: The nearest stars (besides our Sun) are in the Alpha Centauri system. At this scale, Alpha Centauri would be about 25,000 miles (41,000 kilometers) away.
5. Have the child holding the peppercorn return to the group and ask the children consider what our world would be like if there was no Moon. Ask the child holding the grape to remain as the children consider how the appearance of the sky would change with the Sun (represented by the distant pumpkin) as the only bright source of light.
Allow the children time to illustrate their findings about Earth's neighbor, the Moon, and describe what Earth would be like without the Moon's light. Have them draw and color, comic-book style, the Moon's relationship to the Earth and Sun on their Earth's Bright Neighbor comic panel. Summarize that models, like the one the children made, are useful scientific tools. Scientists use computer models to help them understand the relationship between the Sun, Earth and Moon. They use complex mathematics to look at the past, into the future, and for considering what might have been!
Instruct the children to add the Earth's Bright Neighbor comic panel as the next page in the Marvel Moon comic book by clipping the book together at the upper left corner.