Car Provoking Questions...???

With Alex, before I answer a question I always have to consider what triggered the question in the first place so I can give her a satisfying answer. Because if she isn't satisfied with the answer she will keep on pressing until she is. She always seems to come up with the oddest questions while driving in the car. I guess her mind takes over since she is forced to sit in one place for a period of time.

In the car on the way home from running errands:
Alex: "Does everyone have hair?"
Hmmm...some people shave their heads, some people loose their hair, why is she asking this?
Alex: "Like on their arms?"
That simplifies things.
Me: "Yes they do"
Alex: "Why?"
Me: "Well, to keep us warm. You know how dogs and bears and lions have lots of hair? Well it's because they don't wear clothes so they need more hair to keep them warm. It's a good thing we have clothes to keep us warm isn't it?"
After a little conversation about animals wearing clothes Alex gets serious and says...
Alex: "I don't want any hair on me"
Me: "Uh...let's not worry about that right now"
Then Thinking to myself, "I'd better not let her watch me shave my legs anymore or she might decide she wants to do that too."

In the car on the way to her cousin's house:
Alex: "Does the sun move?"
I know she is asking this because the sun is currently in her eyes and it wasn't a minute ago when we were driving in a different direction. Trying to keep things simple I answer with...
Me: "Yes, it does"
My answer seemed to work, the subject was dropped.
A few minutes later...
Alex: "How does the sun move?"
Brad gives me a warning not to go into the whole "well the sun doesn't actually move, the earth moves around it and we're spinning on an axle...etc" answer.
Me: "Well it wakes up every morning over there (pointing towards the East) and it moves across the sky and goes to bed over there (pointing to the West).
A long conversation goes on about the sun moving and the direction we're facing in accordance to the sun. I was trying desperately to satisfy her with an answer that wasn't too advanced which would bring up more questions and we only had a short time until we would be at our destination and the conversation would have to end. Another long pause...
Alex: "So...why does the sun move?"
She really truly WANTS to know why the sun moves! I finally tell her that we're almost to her cousin's, I have a book at home that will explain all of that to her and I will answer her question then. So now I have to have an astronomy lesson with my 4 year old and teach her all about the sun and solar system and everything because she won't be satisfied until she has solved the mystery of the moving sun.