I understand the Big Bang Theory to consist of all of the matter being pulled into one great gravitational pull. such a great force that it expelled the matter out causing the idea of Red-Shift and everything is moving away from us. But I always understood the BBT as how the universes and everything was created. How can this be so if there was matter to be pulled in and expelled during the BBT? Oh dear... My mind is soon to reenact that of the Big Bang. So yeah, how was the matter created BEFORE the BBT for the BBT to take place? Please correct me if my understanding of the BBT is incorrect.
It is a mathematical model to start with, and if one extrapolates it to the (0,0,0,0) point of space time one would arrive at the singularity that the mathematics of the model has. Do we expect that at the same time, the mass/energy that exists now in our observable universe had been "squized" to a point?
You will notice in the graphic that before we reach the mathematical singularity, going backwards, we hit the "inflation" region. That is the point where our observations end. What precedes is the inflation region that has been postulated because of the cosmological observations, and it is a quantized gravity region, otherwise the Big Bang model will not fit the data/observations. Quantum mechanics is notorious for avoiding singularities.
We have not managed to get a quantized gravity to work yet in a unified manner with the other three forces to be able to push the mathematics to the beginning of (0,0,0,0) so we cannot state what the final Big Bang model says for the very beginning.
In conclusion, the Big Bang model does not extend to the time where energy was "created". Different mathematical models are proposed for the possible beginnings but are at the moment disconnected from the empirical mathematical fit of the BB model. It is an open research field.
The flat universe theory basically states that the universe has a net energy state of zero. It exists due to some unknown perturbation which caused an explosion of space-time. There have been some experiments which have shown that matter can appear in a complete vacuum of space.