Here's a conversation my dad and I had with the children on our way through the parking lot. The children each had a balloon.
Dad: Don't let go of those balloons.
A: Why not?
Me: Because they will fly away forever.
Z: Why forever?
Me: Because none of us can fly to go catch the balloon if it flies away.
Dad: Yeah, where's Superman when you need him?
Z: In our imaginations.