The problem is that you are not talking about nothing. You are actually talking about an empty space.
Erm - no. Empty space would be
something. What we're talking is a singularity. Chaos. Tohu va Bohu. Infinite possibility. No-space. No-time. Everything, compressed into nothingness. The point that's not a point, where all opposites become one - and none. Up is down, hot is cold, now is then, and never.
Its really hard for our minds to phantom nothing. How can we imagine what is not? We are creatures of matter and substance, so we think of everything in those terms. When there is nothing we see an empty space. But nothing is not simply an emptiness.. it is not a vast space waiting to be filled... for that would be something. Its not an energy source waiting to produce something. Nothing is simply nothing. Nothing can only be nothing. For if its something other than nothing... its not really nothing.
So even if an Atheist thinks he has an explanation for everything, he still cannot explain why there was never a pure nothing... why there was always something.
Well, you see, and that's where you are wrong: I have yet to meet atheists who think that they can explain
everything - as opposed to some theists, who believe that they have all the answers, contained in the pages of an anthology of myths composed in the late bronze age. In fact, I'd go so far as to claim that most atheists became such because they realized that the answers provided by their original religion were too shallow, too simplistic, too altogether convenient and human.
The driving force behind science is the admittance of ignorance - and the desire to fill in the blanks.
The driving force behind religion, on the other hand, is the illusion of knowledge - and the desire to cling to it.
As for singularities and such like: present-day physics is a discipline that conceives of things few people can fathom, based on mathematical models that can be tested for accuracy. Ten-dimensional space curving in upon itself. Super-strings. Quantum mechanics. Gluons. And, yes, singularities.
*I* don't pretend to understand it all, having at best a cursory knowledge of such matters.
But even the most obscure mathematical novel still makes a billion times more sense to me than "The Great Celestial Artist hand-crafted the Universe". Why? Because that's as if a species of sentient dogs believed that dinosaur fossils came to be in the ground because the Dog From Heaven put them there. It's thinking within altogether human categories that leads people to imagine a creator. And to me, it's just a supremely silly idea, and one that solves none of the mysteries surrounding the fabric of space-time. Quite the contrary, you end up with a super-being that just existed, but whose deeds, thoughts and motivations are strangely reminiscent of our own species.