Activity: Earth, Sun and Moon
Theme: Astronomy
Ideal Group Size
Grade Level
Set Up/Clean Up Time
Activity Time
Small to mid-size (up to 30)
All
2 min / 1 min
5-10 minutes
Math/science questions addressed: How big are the moon and sun compared to Earth? How do the moon and
sun move compared to each other during the day, week, month and year?
Overview: Participants create a scaled-down model of our local part of the solar system and explore how the
parts move relative to each other.
Materials: Large beach ball Earth, small moon ball, 40 feet of string.
Setup: Inflate the Earth beach ball.
Ask: How big is the moon compared to Earth?
To Do: Have one volunteer hold the larger beach ball – this represents Earth. Have someone else hold the
smaller ball, which represents the moon. Using the 40-foot length of string, have the 2 volunteers stand 40 ft.
apart (if possible!).
Explain: The moon is about 1/4th size of the Earth. At this scale, the two would be about 40 ft. apart. In reality,
the moon is 240,000 miles away from Earth.
Ask: How big is the sun compared to Earth?
Explain: Really, really big! If the Earth were as big as this beach ball, the sun would be taller than a 10-story
building, and it would be more than 2 miles away!
Ask: What is an “orbit”?
To Do: Have the moon start to orbit (walk in a circle) counterclockwise around Earth.
Explain: The moon is held in orbit around the Earth by gravity, and it makes one full orbit about once every 27
days – this is part of the reason people all over the world can see the moon. The moon’s orbit is also the reason
we see different parts of it lit (different phases) over the course of a month. The moon orbits Earth about once
every 27 days, and it travels counterclockwise.
To Do: Invite another volunteer to be the sun. Ask the Earth volunteer to orbit slowly counterclockwise around the
sun, and challenge the moon volunteer to continue orbiting (carefully!) around Earth, as it moves around the sun.
Explain: The Earth takes 365.25 days (1 year) to orbit around the sun 1 time.
Optional extension: For a real challenge, invite the Earth model to ALSO spin on its axis (like a ballerina) as it
orbits around the sun. The Earth spins on its axis once every 24 hours. To be most accurate, have the Earth
model spin counterclockwise.
Activity extension: for younger participants: This activity is a great opportunity to get the whole group moving!
With one volunteer as the sun, invite EVERYONE else to imagine they are another planet orbiting around the sun,
and simultaneously spinning like a ballerina. Once everyone is dizzy and giggling, have everyone sit back down
and invite volunteers from the group to tell a story about their imaginary planet. How long is a day, or a year on
that planet? How cold is it? Is there life on that planet? What kind? What does it sound like on that planet?
These 2014 Summer Learning science activities were developed by Pacific Science Center