I have often been told that at the start of our "universe" (I prefer "self-contained energy system" - SCES, myself) all energy was contained in a singularity. What is the evidence for this all-containing singularity being the initiation of the big bang? Is it not reasonable that the extremely dense core of a shrinking SCES (or universe) could have exploded with energy already in existence around it? Any illumination would be appreciated. Please be aware my understanding of physics is limited.