Many secular cosmologists believe that the universe came into existence in a singularity, as a result of a quantum event about 14.7 billion years ago. However, this so-called Big Bang theory is not without its problems.

Ref: Faulkner, D.R. (2014), Has Cosmic Inflation Been Proved?, , accessed 05/17/2017. Image: representation of Big Bang and Inflation, by Yinweichen, License: Creative Commons Attribution, Share-Alike 2.0 Unported.