Questions Jack has been asking me lately

My oldest child will be 5 in just 2 weeks, and he often stuns me speechless with some of his profound questions, like:

1)  Why do airplanes need two pilots?

2)  How did the sun get made?

3)  What is gravity and why do we need it?

4)  What are my "tennis balls" for?  (pointing to his lower man parts)

5)  Why aren't the other planets like earth?

6)  Who made people?

7)  I know why there's grass on the roof of Starbucks.  It's to keep the heat in the building.  (Yes - there's a grass roof on top of our local Starbucks.  And I know this isn't a question, but it's profound nonetheless.)

I usually start off my answers with something like, "Jack, that was a very good question, and it has more than one answer." Meanwhile my brain spins frantically for a short, appropriate and hopefully, correct answer.

And I get to do this two more times with the twins.  At least I'll be better prepared next time around!