Why the world turns

One sunny day last week, as we were walking home from the park, Big Brother looked up, pointed at all the "pretty" colors in the sky, and spewed forth an endless stream of questions.

BB: Look momma, the sun is setting
Me (huffing and puffing up the mini hill where our house sits): Yep.
BB (looking up at the sky): Why does the sun set?
Me: Because the Earth turns and the sun hides on the other side of the Earth.
BB: Why does the Earth turn?
Me (pausing for a moment trying desperately to think back to my Earth History class in college): I think it's because of the pull of the sun, but I'm really not sure.
BB (looking puzzled): How do we not fall off?
Me: Gravity is a force that makes us stick to Earth because Earth is enormous. It's shaped like a big ball - a sphere.
BB: So grabity keeps us stuck? What's inside the earth?
Me (Thinking I seriously didn't expect these kind of questions until at least 4th grade): Rocks, metals, dirt. The world is made up of several layers - the crust, mantle which is more of a lava-like substance, and a dense core.
BB: Can we go inside the Earth?
Me: Not very far. The Earth is so huge, we just don't have the technology to go inside the Earth.
BB: Can we leave the Earth and go into outerspace?
Me (trying to remember I am still walking on the street and should look out for cars): Yes, but we can't go too far. We need to use powerful spaceships or rockets to break from gravity's force.
BB: Can we visit the sun?
Me: No we don't have the technology to go as far as the sun, and even if we did, we would start to melt before we got anywhere near it. It one big fiery star.
BB: What if we wear astronaut suits?
Me: It would still be too hot.
BB: Can we go to other planets like Saturn or Mars or Jupiter?
Me: (attempting to gather all our things including kids into the house): We can't go yet, but we have sent satellites and robots to Mars.
BB: Can you show me pictures of the Earth?

The conversation went on for another 30 minutes like that that led to a display of a ball revolving around a lamp, a visit to google earth, and further discussions of Earth years, seasons, and the Earth's orbit around the sun.

I'm sure some of the informations mentioned was incorrect like the part where I said the Earth spins because of the sun. What I should have said was that it's probably because of the cosmic explosion that formed Earth and hurled it into space, and other collisions that sent it spinning. In my defense, his question caught me off guard, and no one really knows exactly why the Earth spins. I'm sure he'll ask me about all these wonderful cosmic forces I know little about next time we see a sunset. I really thought he and I would be much older before he started asking me questions I couldn't answer. There are still so many questions I myself am searching for answers to - like how it is two tiny bodies can produce soooo much laundry.