"Por que, mamae?"

It started suddenly, and I was very happy when he first said the "por que, mamae?" (why, mommy?) Thinking it is good for being curious and to want to know 'the world'.... well, now he asks "por que, mamae?" at the end of any phrase I say! Sometimes I have a perfect answer (why is there thunder? why can't Josefine walk yet?) but sometimes he leaves me speechless (why does Oma not live with us? why is the moon 'in half' today? why does 'our building' not grow, like us? why does the truck use gasoline but my bike doesn't?) It must be in the genes - both Jason and I were very curious when we are young... I just hope I can keep up with all his questioning!