AG, you’re cherry-picking while ignoring the full context. My statement was
a conditional explanation, not a categorical claim. Here’s what I actually
said:

"If the universe was infinite at one moment, it stays infinite—shrinking
only applies to what is within our causal past, not the entire space."

And earlier:

"We don’t know if the universe is infinite or finite. Observations are
consistent with both possibilities."

I was explaining the logical consequences of an infinite universe—not
asserting that the universe is infinite. Your failure to distinguish
between an explanation and a claim is your problem, not mine.

Quentin

Le mer. 26 févr. 2025, 13:36, Alan Grayson <agrayson2...@gmail.com> a
écrit :

>
>
> On Wednesday, February 26, 2025 at 6:30:06 AM UTC-7 Quentin Anciaux wrote:
>
>
>
> Le mer. 26 févr. 2025, 12:02, Alan Grayson <agrays...@gmail.com> a écrit :
>
>
>
> On Wednesday, February 26, 2025 at 4:44:05 AM UTC-7 Quentin Anciaux wrote:
>
> AG, the question isn’t whether I conclude the universe is infinite—it’s
> whether the cosmological models allow for an infinite universe and what
> their implications are.
>
> We don’t know if the universe is infinite or finite.
>
>
> *OK, but in the post I responded to, you categorically stated that the
> universe is infinite, and that's on you! AG *
>
>
> I did not and never have. You're so entrenched in your own prejudices that
> you forget to read.
>
>
> Really? Here are YOUR words.  "AG, the key point is that the observable
> universe is just a finite portion of an infinite whole. As we go back in
> time, the observable region contracts because the horizon of what we can
> see shrinks, but the entire universe remains infinite."  Later, you took a
> more objective view. AG
>
>
> Quentin
>
>
>
> Observations are consistent with both possibilities. If it is infinite,
> then it has always been infinite, and the observable region shrinking as we
> go back in time is just a consequence of our causal horizon contracting,
> not the entire universe shrinking. If it is finite, then its total volume
> could decrease over time.
>
> This isn’t about opinion, it’s about following the logical consequences of
> each assumption. If you’re struggling with that distinction, that’s on you.
>
>
>
> Le mer. 26 févr. 2025, 11:38, Alan Grayson <agrays...@gmail.com> a écrit :
>
>
>
> On Wednesday, February 26, 2025 at 4:29:13 AM UTC-7 Quentin Anciaux wrote:
>
> AG, the key point is that the observable universe is just a finite portion
> of an infinite whole. As we go back in time, the observable region
> contracts because the horizon of what we can see shrinks, but the entire
> universe remains infinite.
>
> Why does the unobservable part remain infinite? Because spatial infinity
> doesn’t depend on what we can observe. If the universe was infinite at one
> moment, it stays infinite—shrinking only applies to what is within our
> causal past, not the entire space.
>
> The density increases everywhere, meaning in any finite region—including
> our observable universe—matter gets packed into a smaller space. But an
> infinite universe still has no overall “volume”, so it never “shrinks,”
> only becomes denser.
>
> The dichotomy isn’t a contradiction, it’s a consequence of causal
> horizons—our observable universe is just a window into an infinite cosmos.
>
>
> And you know that how? How did you conclude it's infinite, other than
> having an opinion? AG
>
>
> Quentin
>
> Le mer. 26 févr. 2025, 11:08, Alan Grayson <agrays...@gmail.com> a écrit :
>
>
>
> On Wednesday, February 26, 2025 at 3:51:50 AM UTC-7 Quentin Anciaux wrote:
>
> AG, your statement "density can't diverge unless volume goes to zero"
> assumes a finite volume, which doesn’t apply in an infinite universe. In an
> infinite universe, density can increase indefinitely everywhere without
> requiring a total volume to shrink.
>
>
> I was explicit, that the observable universe shrinks, but according to you
> and Brent the unobservable part remains infinite. I can't imagine such a
> dichotomy. AG
>
>
> Brent is correct that the observable universe (the region we can see)
> shrinks as we go back in time, but that doesn’t mean the entire universe
> (including the unobservable part) does the same.
>
>
> Why not? Is that just your opinion, or something demonstrable? AG
>
> The observable universe is just a region within an infinite space, and as
> we go back in time, the light cone that defines what we can observe gets
> smaller.
>
> If the entire universe is infinite, its total volume remains infinite at
> all times
>
>
> OK. AG
>
>
> —but its density can still increase without bound.
>
>
> Density of what region? AG
>
> There’s no contradiction.
>
>
> The contradiction is the dichotomy between the behavior of the two
> regions. AG
>
>
> Quentin
>
> Le mer. 26 févr. 2025, 10:47, Alan Grayson <agrays...@gmail.com> a écrit :
>
>
>
> On Wednesday, February 26, 2025 at 3:33:55 AM UTC-7 Quentin Anciaux wrote:
>
>
>
> Le mer. 26 févr. 2025, 10:24, Alan Grayson <agrays...@gmail.com> a écrit :
>
>
>
> On Wednesday, February 26, 2025 at 1:22:21 AM UTC-7 Alan Grayson wrote:
>
> On Tuesday, February 25, 2025 at 10:07:41 PM UTC-7 Brent Meeker wrote:
>
> On 2/25/2025 7:59 PM, Alan Grayson wrote:
>
>       On Tuesday, February 25, 2025 at 6:40:35 PM UTC-7 Brent Meeker wrote:
>
>
>
> On 2/25/2025 3:48 PM, Alan Grayson wrote:
>
>
>
> On Tuesday, February 25, 2025 at 12:46:46 PM UTC-7 Brent Meeker wrote:
>
> I think all cosmologist, like Hartle, recognize that *the observable
> universe* was much smaller in the past.  Which is perfectly compatible
> with *the universe* be spacially flat and infinite.
>
> Brent
>
>
> I fully anticipated that response. But why would the observable universe
> behave radically different from the entire principle, particularly in light
> of the Cosmological Principle? AG
>
> It's not radically different.  It's different in exactly the way that
> finite subsets of infinite sets behave.
>
> Brent
>
>
> But if the observable universe contracts to zero volume, the entire
> universe has a singularity, which is inherently contradictory. So, the
> model is, to say the least, inconsistent. AG
>
> It's not contradictory or inconsistent, it's unphysical, i.e. it can't be
> physically realized; which just means the theory of general relativity
> doesn't work there.  This is not a surprise since GR is not a quantum
> theory and if you're concerned with a subatomic scale region you'll
> probably need a quantum theory.
>
> Brent
>
>
> My conjecture is that there's a fifth force, repulsive in Nature, that
> prevents the mass of a high mass collapsing star to reach zero volume. AG
>
>
> I don't imagine a quantum theory. More important, I can't grasp the idea
> of the observable universe contracting to zero or near zero volume as we go
> backward in time, while the unobservable universe remains infinite in
> spatial extent. Can you grasp it? Can you explain it? AG
>
>
> As I've explained already, it's not that the volume goes to zero, but
> density that goes to infinity, everywhere, there is no valid notion of
> volume in an infinite universe.
>
> Quentin
>
>
> Density can't diverge unless volume goes to zero. FWIW, Brent thinks the
> observable universe shrinks to zero or near zero as we go backward in time,
> while the unobservable part remains infinite. AG
>
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