Our universe is a 3D Manifold in a higher dimensional space.
All event horizons have a "surface normal" (orthogonality) direction at any point. For example a conventional Black Hole (2D one) has an event horizon that is a 2D surface. That is, for a flatland creature living on that EH it takes two coordinates to define a location, but these flatlanders would experience "time" as the "growth" of the EH (like when more mass falls into it, and the EH grows), and the direction is "outward" (perpendicular to EH surface)
Now here's the interesting part: Event Horizons come in all dimensions. Our "Universe" is a 3D EH, but of course at any point in space there's a unique "rate of time" and a common "direction" of time, which from a higher dimensional space perspective is simply the "orthogonal direction" to all our space directions. (Time orthogonal to Space [i.e. Minkowski]).
As matter falls into our "Universe", that moves time forward for us. But our universe itself consists of all the "points" (Quantum Decoherence Points) which are co-located on a 3D manifold embedded in a higher dimensional space.
This means the Big Bang has things exactly "inverted", and is wrong. Matter didn't "originate from inside". It's the opposite o that. Everything "fell in" from outside. The reason our universe is expanding and accelerating is because it's a black hole EH. Black Holes mainly just grow (excluding tunneling etc).