"Where did the universe come from?" That's a question theists frequently pose in an attempt to try and show the existence of a god. And they often claim that since scientists don't know where the universe came from, then obviously "god musta done it".
But now those pesky scientists may have an answer, and whaddya know, it doesn't include "god".
The universe may have existed forever, according to a new model (http://phys.org/news/2015-02-big-quantum-equation-universe.html) that applies quantum correction terms to complement Einstein's theory of general relativity. The model may also account for dark matter and dark energy, resolving multiple problems at once.
"In addition to not predicting a Big Bang singularity, the new model does not predict a "big crunch" singularity, either (http://www.sciencedirect.com/science/article/pii/S0370269314009381). In general relativity, one possible fate of the universe is that it starts to shrink until it collapses in on itself in a big crunch and becomes an infinitely dense point once again. ...
In cosmological terms, the scientists explain that the quantum corrections can be thought of as a cosmological constant term (without the need for dark energy) and a radiation term.
These terms keep the universe at a finite size, and therefore give it an infinite age. The terms also make predictions that agree closely with current observations of the cosmological constant and density of the universe."
It's far too early to say that this is a definitive answer, but step by step we're getting closer to figuring it out.