I think it's pretty clear that Peter is either a chemist or a physicist. He is obviously very analytical and approaches pizza-making from a scientific point of view, paying very close attention to the smallest details in math, measurements, and documentation. If you read his posts about pizzas he's made, they bear quite a resemblance to scientific journals, which I think is awesome because his information is verifiable and can easily be reproduced. He's organized, too, like a scientist. Man, I could go on and on.
If he's not a scientist, he always wanted to be. (My guess, though, is that he is a scientist who always wanted to be a pizza guy.)