My "fact" doesn't refer to the universe being flat. I would never call this a fact. The "fact" I referred to is that the universe appears to us to be flat as far as we can tell.
Our observable sphere in ly is always smaller than the age of the universe in years (so ~14 thousand million years)
This ignores the basic fact that the universe is expanding at an accelerating rate. I'm comfortable calling this one a fact. Many 9s behind that confidence percentage (even if the number of nines was recently lowered).
A Universe that begins in a singularity cannot have an infinite diameter
Based on what logic? You are probably imagining an infinitesimally small sphere expanding out and becoming the universe. This is a good description of only our observable universe. There's no reason not to think that point wasn't part of an infinitely large manifold. This would point to an infinitely large universe.
I'm not an expert, but in my curiosity I've spoken to Dr. Don Lincoln from Fermilab about this very topic, so that's the source of my confidence. Along with my own subsequent (armchair) research. I've since followed up and done my best to understand why this misconception is so prevalent. I'm convinced it's because many sources say "universe" when they mean "observable universe", leading to many misconceptions.
> "This ignores the basic fact that the universe is expanding at an accelerating rate."
And that ignores the basic fact that information about those parts of the Universe didn't have time to arrive yet (that is where relativity is violated). You are mixing the concept of "observable universe" with "observed universe". At a given time, given the expansion rate of the universe you have an "observable universe" (those ~90E9 ly), but it will only be fully observable somewhere in the future, in the present you only get to observe ~14E9 ly). In a nutshell what you are proposing is that we are observing particles with infinite redshift. Or perhaps in a simpler way: You can be observing today parts of the universe that are (for instance) 25E9 ly away today, but you are observing particles of light that left that part of the universe a long time ago so that the c x t condition was never violated.
> "This is a good description of only our observable universe. There's no reason not to think that point wasn't part of an infinitely large manifold. This would point to an infinitely large universe."
Based on the theory of the Big Bang which is the de facto theory accepted by Cosmology. It is true that you could have an infinitely large manifold and that is a very interesting theory. But I was answering inside the actual theory that is the accepted one now-a-days the Big Bang (and I actually referred that in the answer). Also, even inside the manifold theory theory, our universe that is what is being discussed here, would still not have an infinite diameter.
Our observable sphere in ly is always smaller than the age of the universe in years (so ~14 thousand million years)
This ignores the basic fact that the universe is expanding at an accelerating rate. I'm comfortable calling this one a fact. Many 9s behind that confidence percentage (even if the number of nines was recently lowered).
A Universe that begins in a singularity cannot have an infinite diameter
Based on what logic? You are probably imagining an infinitesimally small sphere expanding out and becoming the universe. This is a good description of only our observable universe. There's no reason not to think that point wasn't part of an infinitely large manifold. This would point to an infinitely large universe.
I'm not an expert, but in my curiosity I've spoken to Dr. Don Lincoln from Fermilab about this very topic, so that's the source of my confidence. Along with my own subsequent (armchair) research. I've since followed up and done my best to understand why this misconception is so prevalent. I'm convinced it's because many sources say "universe" when they mean "observable universe", leading to many misconceptions.
You seem as misinformed as most.