The current scientific model has us understanding that space and time are a single fabric. Neither existed prior to the big bang, so certainly if God is responsible for the big bang, he exists outside of time and space as we understand them. Trying to explain how God came to exist would be like trying to explain what a four-dimensional cube looks like. We can’t possibly fathom either idea, but for someone who exists outside of the limits of our perceivable dimensions it’s probably very simple to understand. A person born blind can’t begin to imagine what the color blue looks like. A person born deaf could never have the slightest inkling of what a pentatonic scale sounds like. And a person born within the constraints of time and space could never possibly understand what the things beyond those constraints are like. But being born without the ability to understand does not possibly justify disbelief. Atheism takes a stance of certainty, and requires just as much faith in something you could never know as theism does; making atheists, at best, hypocrites. A human saying “there is no god” is as absurd on its face as a blind person saying “there is no blue,” even though a blind person has just as much reason for the belief. They can dismiss everything anyone has ever told them about blue because their personal life experience does not confirm the existence of blue, nor does the experience of any of their blind friends. Certainly the personal experiences of the non-blind in which they think they experienced blue can be scientifically explained by the blind model of colors, so do you think a blind person would be justified in saying “blue doesn’t exist and everyone who thinks it does is a moron/gullible/has confirmation bias”?