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Comment by EMM_386 | Hacker News Reader

What my mind fails to understand is, if the universe was infinite, how does that work with the "big bang" theory?

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.

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I think you should read this article "Misconceptions about the Big Bang": http://pages.erau.edu/~reynodb2/LineweaverDavis_BigBang_SciA...

The big bang was an "explosion" of space itself. There was not previously empty space.

> 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.

Technically I think yes, it may have a finite extent. If inflation theory is correct though, it will continue to inflate at extreme rates (if unevenly) for infinite time and so depending on how you think about infinity will have infinite extent in spacetime.

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.

https://en.wikipedia.org/wiki/Conformal_cyclic_cosmology

Some shapes have finite volume and infinite surface area.

https://en.m.wikipedia.org/wiki/Gabriel%27s_Horn

The size of the universe is governed by an equation like this (this is pure analogy):

   D = d * (t - t0)

Where “d” is space, “t” is “time” and “t0” is “the beginning”. Notice that when t=t0, we get a 0 term.

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