Yesterday, Quirks and Quarks (the Canadian Broadcasting Corporation's brilliant weekly science radio show) aired a fantastic segment on string theory and the origin of the universe, entitled "Before the Big Bang." I've been reading and hearing about string theory for a decade now, but haven't quite managed to make sense of it. After hearing yesterday's Quirks, I feel like I'm getting in the ballpark (it doesn't hurt that the production values for this episode are really high, with great, witty edits).
The Big Bang theory of the origin of our universe is widely accepted by the physics community. The idea that our universe started out as some infinitesimally small point, which expanded out to what we see today, makes a lot of sense. Except for one small thing. That initial point, called a singularity by physicists, is a physical impossibility. According to the models we have today, the temperature of the universe at that first moment would have had to be infinite, which mathematically makes no sense. Also, the singularity doesn't do a good job of explaining where all the matter and energy we see today in the universe came from. So, physicists are increasingly starting to look at other branches of physics to see what they can do to replace the singularity with a more reasonable proposition, one which can actually be explained by existing science.
Link, Link to Quirks and Quarks podcast feed