primal yell

My kid likes to lean back and teeter on the back legs of the chair, so I of course do the mom thing that includes, yelling "Stop doing that! You'll break the chair, you'll break your head."
I was trying to explain to him a few days ago about how light can travel through a vacuum, but sound can't because it needs the air molecules. We talked about space, and being outside the Earth's atmosphere, and how it is like a vacuum. I asked if he could think of anything else missing in outer space, that we have on Earth. He starts to lean back in the chair, I say "Quit doing that!" I give him a hint and say "What keeps us on the ground?" He answered, "Your yelling?" After laughing, I said "gravity".
I remember being a kid, it was fun to be able catch adults off guard.