Where does a helium balloon go when you let it go?
That balloon stuck on your ceiling? Outside, it would climb higher than the planes — but it would swell up and pop long before it ever reached the stars. And it sags by morning because helium keeps sneaking out through the rubber.
Talk about it
- Push a ping-pong ball under water and let go — feel the push-back? That shove is buoyancy, and air does the same to a helium balloon.
- Find the highest thing you can both see out the window, then ask: is that higher than a plane flies?
- Drop a feather and a coin at the same time and count how long each takes to land — then talk about how thin, wispy air treats light things up high.