Solar System Scale & Size

Grades: K-4 Prep Time: About 20 Minutes Lesson Time: About 60 minutes

What Students Do: Explore Size and Distance in the Solar System

Students will build a model of the solar system using beads and string. They will also compare the sizes of planets using common fruits and seeds. This lesson comes after a simpler balloon activity that also taught about size and distance in the solar system. It helps students understand scale (comparing sizes) and distance, and shows how models can help us understand big ideas.

Big Questions This Lesson Answers

• What is the universe, and where does Earth fit into it?
• What patterns happen because of how Earth moves in the solar system?

Goal: Students will be able to build a model showing the relative size and distance of things in the solar system.

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1.0 Materials

For the Solar System Bead Model

Each student needs:

• Large craft pony beads in these 11 colors (one of each):
• Yellow (Sun)
• Opaque red (Mercury)
• Cream (Venus)
• Clear blue (Earth)
• Clear red (Mars)
• Black (Asteroid belt)
• Orange (Jupiter)
• Clear gold (Saturn)
• Dark blue (Uranus)
• Light blue (Neptune)
• Brown (Pluto – a dwarf planet, which is smaller than a regular planet)
• 4.5 meters of string
• A small piece of cardboard (10 cm x 10 cm) to wrap the string around when finished
• A measuring tape, meter stick, or other metric measuring tool

Teacher Tip: Pick string that is thicker than twine but thinner than yarn, so it won't tangle. Look for 100% cotton, 4-ply knitting and weaving string. It often comes on a large cone.

Tip for Younger Students: To save time, you can:

1. Cut the string ahead of time and put a set of beads in a plastic bag for each student.
2. Mark measurements on a table ahead of time so students can find their spot and tie on the bead.
3. If marking the string ahead of time, tape newspaper down to protect the floor. Add 4 cm to each planet's distance to leave room for tying the bead on with a double knot.

For the "Farmer's Market Solar System" (Class Demo)

• 1 honeydew melon
• 1 cantaloupe
• 1 lemon
• 1 lime
• 2 grapes
• 1 macadamia nut
• 3 peppercorns

Handouts to Print (from the Student Guide)

• (A) Solar System Predictions – one per student
• (B) Solar System Beads – one per student
• (C) Planet Bead Calculations – one per student
• (D) Farmer's Market Solar System – one per student

Optional Materials (from the Teacher Guide)

• (E) Farmer's Market Solar System Answer Key
• (F) Solar System Cut-outs
• (G) Grading guides for this lesson
• (H) A chart matching this lesson's goals to learning standards

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2.0 Vocabulary

Astronomical Unit (AU): A standard way to measure distance in the solar system. Earth is 1 AU away from the Sun.

Models: A model is something that helps explain how natural things or human-made things work. It can also help show problems or flaws.

Planet: A round object that moves in orbit (a circular path) around a star, like how Earth moves around the Sun.

Prediction: Using what you know to guess what will happen before it does.

Relationship: How two or more things are connected.

Scale: A measurement used to compare the sizes of different objects fairly.

Solar System: Our solar system has 8 planets that orbit the Sun. It also has dwarf planets (like Pluto), comets, asteroids, and moons. Some other stars have their own solar systems, too, with planets and other objects circling them.

System: A group of connected parts that work together to make a whole thing.

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3.0 Steps to Follow

Getting Ready (About 45 minutes)

Building the "Solar System Beads" Kit

A. For each student, get ready: a 4.5-meter piece of string, colored beads, cardboard, tape, and a measuring tool.

Printing

B. Print Handouts (A) through (D) from the Student Guide.

Getting Ready for the "Farmer's Market Solar System"

C. Have the fruits ready for students to look at, or use the cut-out shapes from item (F).

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Step 1: Get Started (About 10 minutes)

Making Predictions

A. Ask students to imagine going on a trip to visit every planet in the solar system. When we plan a trip on Earth, we think about how far away places are and how long it will take to get there. Have students guess how long it would take to travel from Earth to each planet or object in the solar system. They will show this by drawing the distances on handout (A) Solar System Predictions. Their drawing should show how far apart they think the Sun, planets, and Asteroid Belt are from each other, using a regular piece of paper as their scale. Students might need a reminder of all the planets and the order they go in.

Next, ask students to make a second guess using more information. Tell them: if we drove a car at highway speed all the way to the Sun, it would take about 163 years! Driving to Mars at that speed would take 81 years. Driving to the dwarf planet Pluto would take 6,357 years! Of course, rockets travel much faster than cars — a spacecraft heading to Mars travels about 12,000 miles per hour. But comparing it to driving a car helps students understand just how far apart things really are.

Tip for Older Students: Have them figure out the numbers using math instead of just guessing.

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Step 2: Explore (About 10 minutes)

Finding the Scale

A. Hand out (B) Solar System Beads Instructions and (C) Planet Beads Calculation Worksheet.

B. Older students should fill in the chart on worksheet (C), changing each planet's distance (measured in AU) into centimeters. For younger students (Kindergarten–1st grade), do this together as a class, using simple, non-standard ways to measure each AU.

C. Have students measure and cut a piece of string 4.5 meters long.

D. Using the distances they calculated, students tie a bead onto the string with a double knot at the right spot for each planet.

E. When finished, look over the models together, then wrap the string (with the beads on it) around the cardboard holder to keep it neat.

Tip for Older Students: Instead of measuring the whole string ahead of time, they can measure from the Sun to each planet one at a time, tying on each bead right after measuring. This way, they won't need to add the extra 4 cm for the knots.

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Step 3: Explain (About 20 minutes)

A. Have older students answer the questions on worksheet (C). For younger students, talk about it together as a class instead. This step helps students think about how their first guesses compared to what they found out from the model.

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Step 4: Go Further (About 10 minutes)

A. Let students look at the fruits, nuts, and peppercorns (or the cut-out shapes from the Teacher Guide). Explain that just like there's a scale for distance between planets, there's also a scale for planet size. Have students guess which fruit, nut, or peppercorn matches the size of each planet, using worksheet (D) Farmer's Market Solar System. They can use the same item more than once. Have them work together and talk about their choices.

B. When they're done, use answer key (E) to reveal the real answers so students can check their guesses.

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Step 5: Check Understanding (About 20 minutes)

A. Have students finish the last two questions on worksheet (D). Then, as a class, talk about how their first guesses compared to what they learned by the end. This is a great time to remind students that scientists often don't know the answer right away — they use models and guesses to discover new things. Remind students that they can be scientists too, by staying curious, making predictions, gathering information, and changing their ideas when they learn something new.

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4.0 Going Further

Students might wonder why Pluto is no longer called a planet, and why our solar system now has 8 planets instead of 9 like people used to think. This is a good chance to talk about classification — sorting things into groups based on what they have in common. Explain that before we had spacecraft to explore space and powerful telescopes to see clearly, we didn't know as much as we do now.