The sun hasn't gone to bed.....

MasterJ: "It's very dark mummy"
Me: "Yes darling, the sun has gone to bed"
MasterJ: "No Mummy, it can't go to bed yet"
Me: "Why can't the sun go to bed?"
MasterJ: "Because it has to have a bath first"
Me: "Oh, so it can have a bath and go to bed then?"
MasterJ: "No, it can't go to bed then!"
Me: "Why not?"
MasterJ: "Because it hasn't had a tickle yet!!"