He's a bright boy

I'm not sure when kids are supposed to start asking these questions, but I've recently had conversations with six-year-old Primus about:

• The concept of nothingness. His contention: "There is no such thing as nothing". My reply: "well, what have you got left in a bag when you had one apple, and someone takes it out?". I had to point out that if there was no such thing as nothing, then you wouldn't be able to take out that last apple because you wouldn't be able to have nothing left. He seemed to get it - there is such a thing as nothing, but it's not the same kind of thing as "things". I refrained from hitting him with the concept of Concepts.
• The extent and composition of the universe. This went along the lines
  P: "Daddy, where does Gold come from"
  Me: "They dig it out of the ground"
  P: "But how did it get there?"
  Me: "It was there when the Earth formed" (which cued a sidebar discussion about what elements are and some examples of elements vs. things that are made of combinations of elements)
  P: "But how did it get into the stuff that made the earth?"
  Me: "Well, it was created when another star exploded..." (which started a discussion of nuclear fusion and how elements are created in stars, which he kind of understood because he remembered the They Might Be Giants song I sometimes sing them in the bath, followed by the explanation that heavier elements like gold and iron are only created in supernovae)
  P: "Ah. But where did the stuff that other star was made of come from?"
  Me: "Well, that's what the universe was made of after the big bang. It was mostly hydrogen with a bit of helium and smaller bits of stuff like lithium and boron"
  
  
  And from there it got a bit complicated, with his queries prompting me to explain the big bang and how the universe was really small early on and grew into what we see today. And how the Universe had a defined starting point, and about the possible heat death of the universe and the Big Rip.
  
  P: "But what was outside the really small thing?"
  Me: "There was no outside - that tiny little thing was the universe."
  P: "But what was outside? There has to be something."
  Me: "Nothing. You can't have anything outside the universe. The universe is all there is!"
  P: "But there's not such thing as nothing!"

I've got to say, this is a lot more interesting than the pure "Why?" phase, even though it's essentially the same game.