From eSkeptic (link) by Michael Shermer

Quote Originally Posted by Michael Shermer
Why is there something rather than nothing? The question is usually posed by Christian apologists as a rhetorical argument meant to pose as the drop-dead killer case for God that no scientist can possibly answer. Those days are over. Even though scientists are not in agreement on a final answer to the now non-rhetorical question, they are edging closer to providing logical and even potentially empirically testable hypotheses to account for the universe. Here are a dozen possible answers to the question.

The Definitive Dozen

1 GOD. The theist’s answer to the question is that God existed before the universe and subsequently brought it into existence out of nothing (ex nihilo) in a single creation moment as described in Genesis. But the very conception of a creator existing before the universe and then creating it implies a time sequence. In both the Judeo-Christian tradition (along with the Babylonian pre-Judeo-Christian cosmogony) and the scientific worldview, time began when the universe came into existence, either through divine creation or the Big Bang. God, therefore, would have to exist outside of space and time, which means that as natural beings delimited by living in a finite universe, we cannot possibly know anything about such a supernatural entity. The theist’s answer is an untestable hypothesis and thus amounts to nothing more than a god-of-the-gaps argument.
The article continues with a review of the scientific attempts to answer the question. Very interesting read.