Good question

These boys think I know everything. And usually when they have a question, I either know the answer, or can make up a reasonable one. But today, Bobcat stumped me:

"Why doesn't the bubble in the level pop?"

Hmmmm... I thought for a few minutes and, you know, all I could think of was, "Good question!" I know it's trapped in there, and I suppose it has something to do with the consistency of that liquid stuff in there, or surface tension or something. He shook and shook that thing trying to "pop" the bubble, and when he was done, I gave it a whirl.

I'm thinking their questions are only going to get more intelligent and difficult from now on.