Sorry, but that's a load of crap.
Since when is the definition of religion 'a system that concisely defines the laws of nature'?
What are you talking about?
Who defined gravity as "the greatest mystery in science"?
Even if it is, how does that make it "God"?
Religion is, simply put:
Belief in and reverence for a supernatural power or powers regarded as creator and governor of the universe.
Science is not a religion. If anything it is the antithesis of religion.
Gravity is not God. Gravity is a simple force of nature.