The Runaway Planet
Professor Picklebottom has accidentally switched off the Gravity Stabiliser!
Scientists think one of the planets may escape its orbit and disappear into deep space.
Before the Solar System falls apart, your mission is to investigate:
What happens when an orbit suddenly disappears?
Can you predict the runaway planet's path?
9-12 yrs
Easy
15
min
Stage 2, Stage 3
Mission Briefing.
Designed by Darin Carr (BSc, DipEd)
NESA Accredited Teacher Chemistry & Physics Specialist
Creator of the LAB™ Learning System
Professor Picklebottom
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The Runaway Planet
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NESA Accredited Teacher
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High school chemistry & physics specialist 30+ years
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The Crazy Scientist in primary schools — 15 years
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International conference presenter on science education
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Creator of the LAB™ Learning System
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Curriculum aligned: NSW Science & Technology K–6 (2024)
A picture is worth a thousand words — check this out and see if you can spot the science hiding in plain sight.
Mission Equipment
1 wooden embroidery hoop, 17–20 cm diameter
1 marble — standard glass marble works best.
Smooth flat surface: a table or smooth floor. NOT carpet — the marble will not roll freely enough to maintain an orbit.
1 sheet of white A3 or butcher's paper to place under the hoop — use a pencil to mark the marble's escape path after the lift.=
Ruler or tape measure to record escape distances.
Let’s Investigate
1
Set the stage
Place a marble inside the loop and move the loop so that the marble moves around on the inside of the loop.
This is how planets move in their orbits.
3
Run the experiment
Set the marble inside and give it a gentle push along the inner wall so it begins orbiting.
While the marble is orbiting steadily, lift the hoop cleanly and quickly straight upward — remove it completely. Watch exactly what the marble does..
5
Change a variable
Would the path change if you changed:
Speed of orbit
Mass of the marble (planet)
2
Prediction
Place a small sticker or piece of tape on the hoop rim to mark the lift point. Before the marble starts orbiting, place three cards on the table outside the hoop:
A — straight out from the marked point (tangent)
B — halfway between A and C, a gentle outward curve
C — directly away from the centre of the hoop through the marked point
4
Think about the results
Ask students to compare their written prediction with what they observed. Who predicted a straight line? Who predicted outward? Who predicted it would stop?
Did it work? Share the science! Tag @the_crazy_scientist on Instagram — we love seeing your experiments!
The Crazy Scientist LAB Learning System™
Every experiment follows The Crazy Scientist Lab Learning System™ — a simple way to help kids think like real scientists.
We
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LINK to what they already know,
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ACTIVATE curiosity through hands-on discovery
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BUILD understanding that actually sticks.
Swing a ball on a string in a circle above your head. Let go. It flies off — but not outward from the centre. It goes straight, in whatever direction it was moving the moment you released it.
Planets orbit the Sun. But an orbit is not something that happens naturally in space. Something has to be pulling each planet inward, every single moment.
The moment that pull disappears, the planet does not slow down. It does not curve away. It does what any moving object does when no net force acts on it. (according to Newton's 1st Law)
Before you see the experiment: what single force is keeping Earth in its orbit right now — and what would happen to Earth the instant that force switched off?
Write your answer before you see the experiment.
You watched the marble orbit. You watched the hoop lift. The marble flew off.
Think back to the exact direction it went. Did it curve outward from the centre — or did it travel in a straight line from exactly where it was at that moment?
While the marble was inside the hoop, what was pushing it inward and keeping it in a circle? What was doing the same job as gravity?
The marble was still moving at full speed when the hoop lifted. Why didn't it slow down or stop — even a little?
If the Sun vanished right now — in which direction would Earth travel? Draw it on your page. Mark your current position in Earth's orbit and draw the arrow.
An object moving in a circle needs a constant inward force. Remove that force — and it travels in a straight line. Immediately. Every orbit in the universe depends on this.
You're on a merry-go-round and let go of the handle. Which way do you fly — straight outward from the centre, or along the curve you were already moving? How does your answer match what the marble did?
"Want the full teacher guide? The Crazy Scientist Lab includes classroom delivery tips, how to manage the WOW moment, differentiation for Stage 2 & 3, — ready to teach tomorrow."
Think Like a Scientist
Scientists don't just do ONE experiment; they change one part of the experiment (independent variable) and then see how it affects another part of the experiment
(dependent variable)
Change ONE variable and test again.
Does the size of the hoop change the direction the marble travels after the lift?
Does a heavier marble travel further in a straight line than a lighter one after the hoop is removed?
🧪 Try it! Change ONE thing and test again. What did you discover?
Dr Puddledrip’s Science Tip
Want to go deeper? Tap a section below to explore. ▼
The Science Behind It
Why doesn't the marble keep going in a circle?
While the marble is moving around the hoop, something is constantly changing its direction.
When the hoop is lifted away, that influence disappears.
Watch carefully: does the marble continue in a curve, or does it travel another way?
Scientists use experiments like this to investigate how objects move when forces change.
Why is the result surprising?
Many people expect the marble to shoot outward when the hoop is removed.
But is that what you observed?
The experiment reveals something interesting about motion that scientists have been investigating for hundreds of years.
What does this have to do with space?
The marble and the planets have something in common.
Planets don't travel through space randomly. Something is constantly affecting their motion and changing their path.
This simple investigation helps us explore one of the biggest questions in astronomy:
What keeps planets moving around the Sun instead of wandering away into space?
Dr Puddledrip's Curiosity Question
If Earth suddenly stopped orbiting the Sun, where do you think it would go?
Draw your prediction before you look it up.
Try next
• See Newton's First Law in action, keeping a coin still while a card flies away → [The Coin Heist]
• Explore what happens when two equal forces act on two people — and both move → [Newton's Question: Who Moves?]
Extension: G&T Years 5 & 6
How does this explain orbits?
Planets behave exactly like the marble. Earth is moving through space at about 30 km/s. Gravity acts like the hoop wall — constantly pulling inward, constantly bending Earth’s straight‑line path into a curve. No gravity → no orbit → Earth travels straight.
Vocabulary
Orbit: A curved path created when gravity continuously bends an object’s straight‑line motion.
Inertia: The tendency of an object to keep doing whatever it is already doing — moving objects keep moving in a straight line.
Know a parent or teacher who'd love this? Send it on! 👇
READY TO TEACH THIS
TOMORROW?
Running the experiment is easy; however, teaching it well is another challenge.
Teachers often ask:
How do I adapt this for Stages 1,2 or 3?
What do I do with fast finishers?
What misconceptions will they have?
How do I structure this for a full class?
What syllabus outcomes does it cover?
What do I say when they ask WHY?
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