Thats cute, I see what you did there.
Trust me, I know why the sky is blue, scientifically. I was using that analogy because its a definite. Would you like me to use a different one?
The reason I know God exists beyond a shadow of a doubt is from the response I got from my prayers. Its truly amazing, you should try it.
And believe me, I know that I know nothing. It is possible that everything mankind "knows" is completely wrong. I try not to put definites in anything, on people's personality, our laws of physics-however this is one of the very, very few things I am completely certain on.