Young Earth AND Big Bang?

To begin, I do believe in a young earth because that is how I interpret scripture, and I do not see any irrefutable evidence… yet… to dissuade me from my beliefs. When observation conflicts with our Biblical understanding, it is our Biblical understanding that is in error, such as was the case with the Catholic Church’s defense of a geocentric model against Copernicus’, and later Galilei’s, observational evidence of the heliocentric model. The reason that I believe in a young earth, yet a big bang, could most likely be based on an ignorant idea that I hold but do not have the ken (pun intended) to fully understand and my ideas will likely allude to my ignorance. This is why I am posing the question here as I cannot find any evidence to defend or disprove my theory and my understanding of cosmology is juvenile at best. I understand that immediately following the big bang, science believes that there was a rapid expansion period where matter expanded faster than the speed of light for a small fraction of a second. I vaguely understand that Einstein’s General Theory of Relativity breaks down at the event horizon of this expansion. My question is this… How do we know how long the period of rapid expansion was, and how do we know how much the universe expanded in that period? Is it possible that when God said “Let there be light” that He unleashed the big bang and the universe expanded to well beyond where the earth was created. Additionally, we know that time is relative to gravity. When the universe was denser, would time not have had the effect of being exponentially faster than on the fringes of the expansion where time would be relatively slower due to lower density of mass? Again, some of the points I have discussed likely allude to my ignorance. There are likely answers to these questions with solid science behind them. I realize that I might not have the background to understand some of these answers but if someone could attempt to explain this in as layman of term that they can, I would greatly appreciate it.