It's tough when kids ask you questions sometimes because they are so simple and basic that they're hard. Take me trying to explain to Audrey a picture in a book of the smoke coming out of a train's smokestack yesterday.
A: "What's that, Daddy?"
D: "It's smoke coming out of the train's smokestack."
A: "How come?"
D: "Because... well, because the train's engine produces exhaust."
A: "Does that smoke go back in there?"
D: "What do you mean?"
A: "Does it go back in the stack? The smoke?"
D: "It doesn't - it just goes out of the smokestack, up into the air."
A: "How come?"
D: "Because, Audrey. Because the coal in the engine of the train burns to give the train energy to go. If the coal wasn't burning the train would just sit there and all the kids you see riding on the cars in the back wouldn't be able to go anywhere. When the coal burns it produces waste in the form of smoke which exits the train through the smokestack. And the smoke just rises up into the air and doesn't go back into the train. Make sense?"
A: "Mmm-hmm." (Her emphasis on the end.)
Silence, and then I keep reading to avoid more questions I can't answer.
"How come?" is her favorite question. Not "Why?" or "What?" or "When?" or "Where?" It's "How come?" I don't know where she picked it up but I'll be damned if it doesn't make you think about stuff that you normally don't think about. And on top of that it can be asked repeatedly to make you think some more.
A hypothetical exchange might be:
D: "The table is red."
A: "How come?"
D: "Because someone painted it red."
A: "How come?"
D: "Because she liked the red color."
A: "How come?"
D: "Because red is her favorite color."
A: "How come?"
D: "Because sometime during her childhood she saw the color red and it made a strong impression on her."
A: "How come?"
D: "Because."
Normally I don't let it go that long but it can. Responding with a question sometimes helps. "What do you think?" is one I use a lot. Lots of the time she has an answer but just wanted to hear what I'd say. Or she'll shrug and say "I don't know..." to which I can say, "You know what? I don't know either!" End of subject.
The best is when Audrey asks me to sit down on the floor to have a conversation. She literally says matter-of-factly, "Daddy, let's sit down and have a conversation okay?" And then we converse about whatever she wants to talk about - usually it's her doing the talking and me doing the listening and prompting her with my own questions.
She really is a smart and curious kid. How come? I don't know. Maybe she gets it from her parents.