Black Holes: Cosmic Vacuum Cleaners or Science Facts?

This mission will help you explore the incredible pull of gravity, just like the powerful force around a black hole.

The Big Question

How can we see the invisible pull of gravity?

What You'll Need

• A bedsheet or large, stretchy piece of fabric
• A few different sized balls or round objects (e.g., a marble, a ping pong ball, a tennis ball, a small melon)
• Four helpers (or chairs/tables to hold the corners)

Mission Steps

1. Set Up the Fabric. Have your helpers hold the corners of the sheet taut, creating a flat, stretchy surface.
2. Add Some Mass. Place the heaviest ball (like the melon) in the center of the fabric. Watch how it creates a dip.
3. Test the Pull. Gently roll the smaller balls (marble, ping pong ball) across the fabric, away from the heavy ball. Observe how their paths curve towards the dip.
4. Explore Orbits. Try rolling a ball fast enough around the heavy ball so it stays in a circular path, like a planet orbiting a star.

Talk About It

• What happened to the fabric when you placed the heavy ball in the middle?
• How did the path of the smaller balls change when they got near the heavy ball?
• How is this like gravity and how planets orbit the sun?

Take It Further

For older rangers, try using the fabric to model how a black hole’s immense gravity warps spacetime. Imagine the fabric is space itself and the heavy ball is a black hole. What happens when you try to roll a small object near the edge of the deep dip?

FAQ

Q: Is this exactly how black holes work? A: This is a model to help understand gravity's pull. Black holes have much, much stronger gravity than anything we can create in our homes. Q: Why can't we see black holes? A: Black holes are so dense that their gravity is strong enough to trap light, so no light escapes for us to see. Q: What is "mass"? A: Mass is how much "stuff" is in an object. The more mass something has, the stronger its gravity.