}]
The start of the big bang is just the cosmic horizon,
similar to the event horizon of a black hole, where time (virtually) stops.
Stephen Hawking's latest Book/TV⋅Series, "Grand Design", talks about it.

I say "virtually", because there's no such thing as a TRUE black hole.

With distance, the clock gets super, super slow,
( red⋅shifted, from our vantage point, out of the gravity well ),
yet nowhere does it truly stop.