Actually, it wasn't an explosion at all--what really happened is rather difficult for most people to grasp.
The word "explosion" implies that there was an "outside" from which it was possible to observe an explosion, or for an explosion to explode INTO. It's not that there was nothing outside--it's that there was no outside, period. By definition, nothing "outside" of the Universe does or can exist.
What actually happened was this--the universe, all of space and time and all the matter, energy, and force in it, started out smashed together into a very, very small volume, smaller than an atom, smaller than a subatomic particle, smaller than...well, it was very, very small. And for reasons that physicists are still puzzling out, and may never be able to adequately answer, that teeny tiny region of space suddenly started growing. And what grew is actual "space" itself.
At some point during this expansion, space had expanded sufficiently that matter, energy, time and the fundamental forces were decompressed enough to start acting in the manner in which we see them behaving today.
Space is still expanding--most everything in the universe we can see is getting farther and farther apart as time goes on. In fact, by some measurements, the expansion may be accelerating over time. The universe is still growing. In addition, space in all directions around us is filled with a weak radio "hiss" referred to as the Cosmic Microwave Background Radiation--this is the last, lingering trace of the heat and light that once filled the universe when everything was crammed together into a tiny volume.
So in conclusion, you're wrong about most everything.
If you choose to believe that God set the whole thing in motion, then there's nothing wrong with that. There's also no way to prove or disprove it one way or another, and may never be, since that requires us to have a working knowledge of conditions that existed prior to the birth of the universe.
