If the universe originated with a Big Bang, what was going on before that? Latest estimates is that the Big Bang occurred 13.8 billion years ago. This was an actual historical event. What was going on 13.9 billion years ago?
Latest theoretical physics says that there was a pre-universe something that was inflating (growing bigger) until it reached some critical mass that caused the massive explosion that began our universe.
If this something was inflating then as we go backwards in time it was deflating. How long ago was it too small?
In short, what we know and what we can surmise on the origin of the universe is incomplete.
Gibbon's Decline and Fall of the Roman Empire in The Basic History Library (free). ------------->