Sources
http://space.about.com/od/astronomybasics/a/Origin-Of-The-Universe.htm
http://www.infoplease.com/cig/theories-universe/scientific-origins-universe.html
http://science.nationalgeographic.com/science/space/universe/origins-universe-article/
http://discovermagazine.com/2008/apr/25-3-theories-that-might-blow-up-the-big-bang