"Did you see... ?" joke

A teacher was teaching a class about the big bang theory. She asked Billy to go outside and observe his surroundings.
She then asked...
"Billy did you see the sky?"
"Yes", said Billy.
"Did you see the sun?"
"Yes", said the boy.
"Did you see God?"
"No", said the boy.
The Teacher said, "So God really isn't there."
A little girl started to ask Billy some questions.
"Did you see the sky?"
"Yes" was the reply
"Did you see the sun?"
Again, "yes" was the answer.
"Do you see the teacher's brain? Because according to her, she doesn't have one!!!"