Solar System Scale & Size

What Students Will Do

We will explore how big the planets are. We will also explore how far apart they are.

Students will make a model of the solar system. A model is something that helps us understand a big idea by making it smaller or easier to see. Students will use beads and string for their model. They will also use fruit and seeds to compare how big each planet is.

This lesson comes after a balloon activity. It helps students learn more about size and distance in the solar system. It also shows how models help us understand things we cannot easily see.

Big Question

What is the universe? Where does Earth fit in it?

We will also think about: What patterns can we see because of how Earth moves in the solar system?

Goal: Students will make a model that shows how big the planets are and how far apart they are.

Materials

For the Bead Solar System

Each student will need:

• 11 colored beads (one of each color):
• Yellow = Sun
• Red = Mercury
• Cream = Venus
• Blue = Earth
• Red (different shade) = Mars
• Black = Asteroid Belt (a ring of space rocks)
• Orange = Jupiter
• Gold = Saturn
• Dark Blue = Uranus
• Light Blue = Neptune
• Brown = Pluto (a dwarf planet — smaller than a regular planet)
• A piece of string, about 4.5 meters long
• A small piece of cardboard to wrap the string around when done
• A ruler or measuring tape

Tip for teachers: Use string that is not too thin and not too thick. Cotton string works well.

Tip for younger students: You can cut the string ahead of time. You can also mark the table with the measurements so students just tie their beads on.

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

Worksheets to Print

• Solar System Predictions
• Solar System Beads
• Planet Bead Calculations
• Farmer's Market Solar System

Words to Know

• Astronomical Unit (AU): A way to measure distance in space. Earth is 1 AU away from the Sun.
• Model: Something that helps us understand a big or hard idea. It can also show us what might go wrong.
• Planet: A round object in space that circles around a star. Earth circles around the Sun.
• Prediction: A smart guess about what might happen, based on what we already know.
• Relationship: How things connect to each other.
• Scale: A way of measuring things so we can compare them fairly.
• Solar System: The Sun and everything that circles around it — 8 planets, dwarf planets like Pluto, comets, space rocks (asteroids), and moons.
• System: A group of parts that work together as one whole thing.

What We Will Do

Get Ready (About 45 minutes)

For the Bead Solar System:
Have string, beads, cardboard, tape, and rulers ready for each student. Print the worksheets.

For the Farmer's Market Solar System:
Get the fruits, nut, and peppercorns ready. You can also use paper cutouts instead.

Step 1: Think About It (About 10 minutes) — Making Predictions

Ask students to imagine going on a trip to visit every planet. When we plan any trip, we think about how far away places are and how long it will take to get there.

Ask students to guess how far each planet is from Earth. They can draw the planets, the Sun, and the Asteroid Belt on paper, showing how far apart they think everything is. Remind them of the order of the planets if they need help.

Then tell them this: If we drove a car at highway speed all the way to the Sun, it would take about 163 years! Driving to Mars would take 81 years. Driving to Pluto would take 6,357 years! Real spacecraft travel much faster — about 12,000 miles per hour. But this car example helps us understand just how far away these places really are.

Step 2: Explore (About 10 minutes) — Finding the Scale

Give students the instruction sheets. Have them measure and cut a string 4.5 meters long.

Using special measurements, students will tie a bead onto the string for each planet. When they finish, they will look over their model. Then they will wrap the string around the cardboard to keep it neat.

Step 3: Explain (About 20 minutes)

Have students answer questions comparing their first guesses to what they found out. Talk about it together as a class.

Step 4: Learn More (About 10 minutes)

Let students look at the fruits, the nut, and the peppercorns (or the paper cutouts). Explain that just like the planets are different distances apart, they are also different sizes.

Ask students to guess which fruit or seed matches the size of each planet. They can use some items more than once. Have them work together and talk about their ideas.

Then show them the answer key so they can check their guesses.

Step 5: Check What We Learned (About 20 minutes)

Students will answer two more questions about what they learned. Talk together as a class. Compare their first guesses to what they know now.

This is a great time to remind students: Scientists don't always know the answer right away. They make guesses, test their ideas, and learn new things. Just like real scientists, students used models, made predictions, and changed their ideas when they learned something new!

Want to Learn More?

Students might wonder why Pluto is no longer called a planet, and why we now say there are 8 planets instead of 9. This is a good time to talk about grouping things by what they have in common. Long ago, before we had powerful telescopes and spacecraft, we didn't know as much as we do now.