If you believe the big bang theory, our universe did not always exist. A law in physics is the conservation of matter and energy. Where did the matter and energy come from to ignite the big bang?
Also, you stated that a "start" isn't a concept of physics. I'll grant that all time began at the big bang and therefore, it is meaningless to describe what happened before, but this is simply not satisfying. I WANT to know, by golly, what happened before the big bang.