Splitting nothing in two

Here's an interesting thing I've just learned: It turns out that, realizing that Einstein's famous equation E=mc squared (dammit, I have to learn how to make superscripts!) means that both matter and energy contribute to the total energy in the universe. It's a BIG amount. Atomic matter, dark matter, dark energy, radiation, it all counts. And it all creates gravity. But now consider this: gravity has negative energy. And, guess what? Gravity has the same amount of negative energy as mass/energy has positive energy! The total adds up to zero!

Is this some sort of cosmic joke? One thinks not. Somehow, the inflation of the Big Bang split "nothing" into two parts - mass/energy and gravity - and created a universe out of that split. We still end up, in a way, with "nothing!"

But, on the other hand, is this supposed to be surprising? After all, there's the law of energy conservation. It HAS to even out.

As you might guess, I'm trying to learn about cosmology, and I'll tell you - as a person without much math (let alone much physics or astronomy, which depends on advanced math), it's a headache.

And then there's the main question: If the universe started with a Big Bang, initiating space, time, and all matter and radiation, what the hell banged?

Cosmology currently seems to be stuck with the idea of some fundamental sort of quantum fluctuation in which enough matter, independently of non-existing space or time, "popped" into being without any reason - sparking inflation which, in fractions of a nano-second, created all the stuff of the universe. I understand there are other ideas - string-theory branes bumping together, for instance - but excuse me: it all sounds like Merlin adding that last alchemical drop.

Sure, I know my lack of mathematical ability is limiting my thinking. But I still am curious. And I have to worry: By the time cosmology cracks what might be the last big nut, my own personal universe might well be moot.