A father and his son were in a boat fishing one day.

the son said "Daddy how do fish breathe under water?"

his father replied "son, I don't know !"

and few minutes went by and the boy said "Daddy why does this boat float and not sink?"

his father replied "son, I don't know !"

a few more minutes went by and the boy asked "Daddy why is the sky blue?"

his father replied "son, I don't know !"

then after about 10 minutes the boy asked "Daddy do you mind me asking all these questions?

his father replied "of course not, if you don't ask questions, how do you expect to learn anything ?"