Either way, the universe is unbelievably, vastly bigger even than the observable 90 billion light years we live in.
Apparently the universe originally (somehow) began as a point of infinite density and expanded outward from this point.
During this process, it would seem to need a defined size in order to be expanding at all. Even with the "blowing up a balloon" way of thinking of the universe, while the individual galaxies are growing further apart, the surface area is measurable (not infinite).
I am likely thinking of this incorrectly but I can't fit "infinite size" in with "expanding universe" in my head.
Unless these theories are incompatible, and to get infinite size you need the steady-state theory.
The big bang was an "explosion" of space itself. There was not previously empty space.
I am very familiar with all of this. My question was merely around the opposing concepts of "expansion" and "infinite".
Not infinite size AT the big bang. Infinite size of the current universe.
On the other hand if Roger Penrose is correct about Conformal Cyclic Cosmology, and cosmic inflation is false, then ultimately the universe will reach a state where scale ceases to matter and it will become mathematically indistinguishable from a hot dense big bang again.
D = d * (t - t0)