Are we living inside a black hole?

[Alan Grayson]

James Webb’s survey of 263 galaxies hints at yes

https://interestingengineering.com/science/living-inside-black-hole-james-webb

[Liz R]

Beware of Betteridge's Law ... but even so, an interesting hypothesis although I'm not sure how it accounts for the universe expanding. Maybe a time-reversed black hole?

[Quentin Anciaux]

I have been reflecting on the idea that our universe could be the interior of a giant black hole, but several fundamental questions arise.

How can this account for the apparent flatness of the universe, given that a black hole’s interior should exhibit strong curvature? Observations indicate that our universe is nearly flat, yet this hypothesis lacks a clear mechanism to explain why.

If we are inside a black hole, where is the boundary? A black hole's internal space-time is inherently limited by the event horizon, yet our observable universe does not show any indication of such a constraint. How does this model reconcile the absence of an observable edge?

Furthermore, in classical black hole physics, the event horizon expands only when additional mass or energy is absorbed. In contrast, our universe’s observable horizon grows over time without any apparent external input. What mechanism would drive this expansion in a black hole framework?

These points suggest that such a model would require an unconventional and exotic space-time structure beyond classical general relativity. I would appreciate any insights on how these issues could be addressed.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

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[Alan Grayson]

On Monday, March 17, 2025 at 5:03:42 PM UTC-6 Quentin Anciaux wrote:

I have been reflecting on the idea that our universe could be the interior of a giant black hole, but several fundamental questions arise.

How can this account for the apparent flatness of the universe, given that a black hole’s interior should exhibit strong curvature? Observations indicate that our universe is nearly flat, yet this hypothesis lacks a clear mechanism to explain why.

If we are inside a black hole, where is the boundary? A black hole's internal space-time is inherently limited by the event horizon, yet our observable universe does not show any indication of such a constraint. How does this model reconcile the absence of an observable edge?

Furthermore, in classical black hole physics, the event horizon expands only when additional mass or energy is absorbed. In contrast, our universe’s observable horizon grows over time without any apparent external input. What mechanism would drive this expansion in a black hole framework?

These points suggest that such a model would require an unconventional and exotic space-time structure beyond classical general relativity. I would appreciate any insights on how these issues could be addressed.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

When you refer to the horizon expanding of the observable universe, are you now assuming the universe is expanding spatially, rather than just the average galactic distances increasing? BTW, I'm confused about how that horizon increases spatially. Aren't the galaxies in the unobservable regions receding faster than light speed, and this is the reason they're unobservable for us? If so, how can the observable region increase so some of them become part of the observable region? One other thing; I viewed a video showing BH's releasing material when too much is inflowing. Is some of this material from the interior, or is all of it inflowing material that is rejected? AG 

[Quentin Anciaux]

Yes, I’m assuming spatial expansion, not just increasing galactic distances. The observable horizon expands because the Hubble rate evolves over time. While some distant galaxies are receding faster than light, the expansion rate is not constant, allowing light from previously unobservable regions to eventually reach us. This is why our observable universe continues to grow.

As for black holes, when they eject material, it comes from the accretion disk, not the interior. Excess inflowing matter, under extreme magnetic fields and radiation pressure, is expelled before crossing the event horizon. Once inside, nothing escapes.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

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[Alan Grayson]

On Tuesday, March 18, 2025 at 10:30:41 AM UTC-6 Quentin Anciaux wrote:

Yes, I’m assuming spatial expansion, not just increasing galactic distances. The observable horizon expands because the Hubble rate evolves over time.

So, are you now agreeing that the universe is spatially finite and expanding, as distinguished from the model that the universe is infinite in spatial extent while the average distance between galaxies in increasing? AG  

While some distant galaxies are receding faster than light, the expansion rate is not constant, allowing light from previously unobservable regions to eventually reach us. This is why our observable universe continues to grow.

So, for some photons emitted from a galaxy in the unobservable region, they never reach us since space in that region is expanding faster than light speed, but others (emitted from different galaxies in the unobservable region) will eventually reach us since the rate of expansion slows as time progresses, such that the spatial expansion in their region has slowed below light speed? AG 

As for black holes, when they eject material, it comes from the accretion disk, not the interior. Excess inflowing matter, under extreme magnetic fields and radiation pressure, is expelled before crossing the event horizon. Once inside, nothing escapes.

That might not be true if all the mass/energy of the universe originated as a BH, which we can identify as the BB. Doesn't the ultra high temperature with all mass/energy concentrated nearly as a spatial singularity at this BB cause a BH to form? AG 

[Quentin Anciaux]

AG,

No, I’m not asserting that the universe is spatially finite. The standard ΛCDM model allows for an infinite spatial extent while still experiencing expansion. The observable universe is finite due to the speed of light and the age of the universe, but beyond that, space could extend infinitely while still expanding. Expansion refers to the metric stretching of space, not necessarily implying a finite boundary. Already discussed.

Some photons emitted in the unobservable region will never reach us because their source galaxies are receding too fast, while others might enter our observable universe if the Hubble rate decreases sufficiently over time. The key factor is that the expansion rate evolves, altering the fate of emitted light.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mer. 19 mars 2025, 05:36, Alan Grayson <agrays...@gmail.com> a écrit :

On Tuesday, March 18, 2025 at 10:30:41 AM UTC-6 Quentin Anciaux wrote:

Yes, I’m assuming spatial expansion, not just increasing galactic distances. The observable horizon expands because the Hubble rate evolves over time.

So, are you now agreeing that the universe is spatially finite and expanding, as distinguished from the model that the universe is infinite in spatial extent while the average distance between galaxies in increasing? AG  

While some distant galaxies are receding faster than light, the expansion rate is not constant, allowing light from previously unobservable regions to eventually reach us. This is why our observable universe continues to grow.

So, for some photons emitted from a galaxy in the unobservable region, they never reach us since space in that region is expanding faster than light speed, but others (emitted from different galaxies in the unobservable region) will eventually reach us since the rate of expansion slows as time progresses, such that the spatial expansion in their region has slowed below light speed? AG 

As for black holes, when they eject material, it comes from the accretion disk, not the interior. Excess inflowing matter, under extreme magnetic fields and radiation pressure, is expelled before crossing the event horizon. Once inside, nothing escapes.

That might not be true if all the mass/energy of the universe originated as a BH, which we can identify as the BB. Doesn't the ultra high temperature with all mass/energy concentrated nearly as a spatial singularity at this BB cause a BH to form? AG 

Already answered.

Quentin

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mar. 18 mars 2025, 16:54, Alan Grayson <agrays...@gmail.com> a écrit :

On Monday, March 17, 2025 at 5:03:42 PM UTC-6 Quentin Anciaux wrote:

I have been reflecting on the idea that our universe could be the interior of a giant black hole, but several fundamental questions arise.

How can this account for the apparent flatness of the universe, given that a black hole’s interior should exhibit strong curvature? Observations indicate that our universe is nearly flat, yet this hypothesis lacks a clear mechanism to explain why.

If we are inside a black hole, where is the boundary? A black hole's internal space-time is inherently limited by the event horizon, yet our observable universe does not show any indication of such a constraint. How does this model reconcile the absence of an observable edge?

Furthermore, in classical black hole physics, the event horizon expands only when additional mass or energy is absorbed. In contrast, our universe’s observable horizon grows over time without any apparent external input. What mechanism would drive this expansion in a black hole framework?

These points suggest that such a model would require an unconventional and exotic space-time structure beyond classical general relativity. I would appreciate any insights on how these issues could be addressed.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

When you refer to the horizon expanding of the observable universe, are you now assuming the universe is expanding spatially, rather than just the average galactic distances increasing? BTW, I'm confused about how that horizon increases spatially. Aren't the galaxies in the unobservable regions receding faster than light speed, and this is the reason they're unobservable for us? If so, how can the observable region increase so some of them become part of the observable region? One other thing; I viewed a video showing BH's releasing material when too much is inflowing. Is some of this material from the interior, or is all of it inflowing material that is rejected? AG 

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[Alan Grayson]

On Tuesday, March 18, 2025 at 11:52:42 PM UTC-6 Quentin Anciaux wrote:

AG,

No, I’m not asserting that the universe is spatially finite. The standard ΛCDM model allows for an infinite spatial extent while still experiencing expansion. The observable universe is finite due to the speed of light and the age of the universe, but beyond that, space could extend infinitely while still expanding. Expansion refers to the metric stretching of space, not necessarily implying a finite boundary. Already discussed.

Some photons emitted in the unobservable region will never reach us because their source galaxies are receding too fast, while others might enter our observable universe if the Hubble rate decreases sufficiently over time. The key factor is that the expansion rate evolves, altering the fate of emitted light.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mer. 19 mars 2025, 05:36, Alan Grayson <agrays...@gmail.com> a écrit :

On Tuesday, March 18, 2025 at 10:30:41 AM UTC-6 Quentin Anciaux wrote:

Yes, I’m assuming spatial expansion, not just increasing galactic distances. The observable horizon expands because the Hubble rate evolves over time.

So, are you now agreeing that the universe is spatially finite and expanding, as distinguished from the model that the universe is infinite in spatial extent while the average distance between galaxies in increasing? AG  

While some distant galaxies are receding faster than light, the expansion rate is not constant, allowing light from previously unobservable regions to eventually reach us. This is why our observable universe continues to grow.

So, for some photons emitted from a galaxy in the unobservable region, they never reach us since space in that region is expanding faster than light speed, but others (emitted from different galaxies in the unobservable region) will eventually reach us since the rate of expansion slows as time progresses, such that the spatial expansion in their region has slowed below light speed? AG 

As for black holes, when they eject material, it comes from the accretion disk, not the interior. Excess inflowing matter, under extreme magnetic fields and radiation pressure, is expelled before crossing the event horizon. Once inside, nothing escapes.

That might not be true if all the mass/energy of the universe originated as a BH, which we can identify as the BB. Doesn't the ultra high temperature with all mass/energy concentrated nearly as a spatial singularity at this BB cause a BH to form? AG 

Already answered.

Please copy and paste your answer. If the universe is infinite in spatial extent, and we run the clock backward, is all  the mass/energy of the observable region confined to a tiny or zero volume? What happens to the mass/energy of the unobservable region? TY, AG

[Quentin Anciaux]

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mer. 19 mars 2025, 09:30, Alan Grayson <agrays...@gmail.com> a écrit :

On Tuesday, March 18, 2025 at 11:52:42 PM UTC-6 Quentin Anciaux wrote:

AG,

No, I’m not asserting that the universe is spatially finite. The standard ΛCDM model allows for an infinite spatial extent while still experiencing expansion. The observable universe is finite due to the speed of light and the age of the universe, but beyond that, space could extend infinitely while still expanding. Expansion refers to the metric stretching of space, not necessarily implying a finite boundary. Already discussed.

Some photons emitted in the unobservable region will never reach us because their source galaxies are receding too fast, while others might enter our observable universe if the Hubble rate decreases sufficiently over time. The key factor is that the expansion rate evolves, altering the fate of emitted light.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mer. 19 mars 2025, 05:36, Alan Grayson <agrays...@gmail.com> a écrit :

On Tuesday, March 18, 2025 at 10:30:41 AM UTC-6 Quentin Anciaux wrote:

Yes, I’m assuming spatial expansion, not just increasing galactic distances. The observable horizon expands because the Hubble rate evolves over time.

So, are you now agreeing that the universe is spatially finite and expanding, as distinguished from the model that the universe is infinite in spatial extent while the average distance between galaxies in increasing? AG  

While some distant galaxies are receding faster than light, the expansion rate is not constant, allowing light from previously unobservable regions to eventually reach us. This is why our observable universe continues to grow.

So, for some photons emitted from a galaxy in the unobservable region, they never reach us since space in that region is expanding faster than light speed, but others (emitted from different galaxies in the unobservable region) will eventually reach us since the rate of expansion slows as time progresses, such that the spatial expansion in their region has slowed below light speed? AG 

As for black holes, when they eject material, it comes from the accretion disk, not the interior. Excess inflowing matter, under extreme magnetic fields and radiation pressure, is expelled before crossing the event horizon. Once inside, nothing escapes.

That might not be true if all the mass/energy of the universe originated as a BH, which we can identify as the BB. Doesn't the ultra high temperature with all mass/energy concentrated nearly as a spatial singularity at this BB cause a BH to form? AG 

Already answered.

Please copy and paste your answer.

No, use your own fingers.

If the universe is infinite in spatial extent, and we run the clock backward, is all  the mass/energy of the observable region confined to a tiny or zero volume? What happens to the mass/energy of the unobservable region? TY, AG

Quentin

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mar. 18 mars 2025, 16:54, Alan Grayson <agrays...@gmail.com> a écrit :

On Monday, March 17, 2025 at 5:03:42 PM UTC-6 Quentin Anciaux wrote:

I have been reflecting on the idea that our universe could be the interior of a giant black hole, but several fundamental questions arise.

How can this account for the apparent flatness of the universe, given that a black hole’s interior should exhibit strong curvature? Observations indicate that our universe is nearly flat, yet this hypothesis lacks a clear mechanism to explain why.

If we are inside a black hole, where is the boundary? A black hole's internal space-time is inherently limited by the event horizon, yet our observable universe does not show any indication of such a constraint. How does this model reconcile the absence of an observable edge?

Furthermore, in classical black hole physics, the event horizon expands only when additional mass or energy is absorbed. In contrast, our universe’s observable horizon grows over time without any apparent external input. What mechanism would drive this expansion in a black hole framework?

These points suggest that such a model would require an unconventional and exotic space-time structure beyond classical general relativity. I would appreciate any insights on how these issues could be addressed.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

When you refer to the horizon expanding of the observable universe, are you now assuming the universe is expanding spatially, rather than just the average galactic distances increasing? BTW, I'm confused about how that horizon increases spatially. Aren't the galaxies in the unobservable regions receding faster than light speed, and this is the reason they're unobservable for us? If so, how can the observable region increase so some of them become part of the observable region? One other thing; I viewed a video showing BH's releasing material when too much is inflowing. Is some of this material from the interior, or is all of it inflowing material that is rejected? AG 

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[Alan Grayson]

On Wednesday, March 19, 2025 at 2:39:57 AM UTC-6 Quentin Anciaux wrote:

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mer. 19 mars 2025, 09:30, Alan Grayson <agrays...@gmail.com> a écrit :

On Tuesday, March 18, 2025 at 11:52:42 PM UTC-6 Quentin Anciaux wrote:

AG,

No, I’m not asserting that the universe is spatially finite. The standard ΛCDM model allows for an infinite spatial extent while still experiencing expansion. The observable universe is finite due to the speed of light and the age of the universe, but beyond that, space could extend infinitely while still expanding. Expansion refers to the metric stretching of space, not necessarily implying a finite boundary. Already discussed.

Some photons emitted in the unobservable region will never reach us because their source galaxies are receding too fast, while others might enter our observable universe if the Hubble rate decreases sufficiently over time. The key factor is that the expansion rate evolves, altering the fate of emitted light.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mer. 19 mars 2025, 05:36, Alan Grayson <agrays...@gmail.com> a écrit :

On Tuesday, March 18, 2025 at 10:30:41 AM UTC-6 Quentin Anciaux wrote:

Yes, I’m assuming spatial expansion, not just increasing galactic distances. The observable horizon expands because the Hubble rate evolves over time.

So, are you now agreeing that the universe is spatially finite and expanding, as distinguished from the model that the universe is infinite in spatial extent while the average distance between galaxies in increasing? AG  

While some distant galaxies are receding faster than light, the expansion rate is not constant, allowing light from previously unobservable regions to eventually reach us. This is why our observable universe continues to grow.

So, for some photons emitted from a galaxy in the unobservable region, they never reach us since space in that region is expanding faster than light speed, but others (emitted from different galaxies in the unobservable region) will eventually reach us since the rate of expansion slows as time progresses, such that the spatial expansion in their region has slowed below light speed? AG 

As for black holes, when they eject material, it comes from the accretion disk, not the interior. Excess inflowing matter, under extreme magnetic fields and radiation pressure, is expelled before crossing the event horizon. Once inside, nothing escapes.

That might not be true if all the mass/energy of the universe originated as a BH, which we can identify as the BB. Doesn't the ultra high temperature with all mass/energy concentrated nearly as a spatial singularity at this BB cause a BH to form? AG 

Already answered.

Please copy and paste your answer.

No, use your own fingers.

I forgot where that was posted. AG

If the universe is infinite in spatial extent, and we run the clock backward, is all  the mass/energy of the observable region confined to a tiny or zero volume? What happens to the mass/energy of the unobservable region? TY, AG

Did you answer the above question? AG 

[Quentin Anciaux]

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mer. 19 mars 2025, 10:19, Alan Grayson <agrays...@gmail.com> a écrit :

On Wednesday, March 19, 2025 at 2:39:57 AM UTC-6 Quentin Anciaux wrote:

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mer. 19 mars 2025, 09:30, Alan Grayson <agrays...@gmail.com> a écrit :

On Tuesday, March 18, 2025 at 11:52:42 PM UTC-6 Quentin Anciaux wrote:

AG,

No, I’m not asserting that the universe is spatially finite. The standard ΛCDM model allows for an infinite spatial extent while still experiencing expansion. The observable universe is finite due to the speed of light and the age of the universe, but beyond that, space could extend infinitely while still expanding. Expansion refers to the metric stretching of space, not necessarily implying a finite boundary. Already discussed.

Some photons emitted in the unobservable region will never reach us because their source galaxies are receding too fast, while others might enter our observable universe if the Hubble rate decreases sufficiently over time. The key factor is that the expansion rate evolves, altering the fate of emitted light.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mer. 19 mars 2025, 05:36, Alan Grayson <agrays...@gmail.com> a écrit :

On Tuesday, March 18, 2025 at 10:30:41 AM UTC-6 Quentin Anciaux wrote:

Yes, I’m assuming spatial expansion, not just increasing galactic distances. The observable horizon expands because the Hubble rate evolves over time.

So, are you now agreeing that the universe is spatially finite and expanding, as distinguished from the model that the universe is infinite in spatial extent while the average distance between galaxies in increasing? AG  

While some distant galaxies are receding faster than light, the expansion rate is not constant, allowing light from previously unobservable regions to eventually reach us. This is why our observable universe continues to grow.

So, for some photons emitted from a galaxy in the unobservable region, they never reach us since space in that region is expanding faster than light speed, but others (emitted from different galaxies in the unobservable region) will eventually reach us since the rate of expansion slows as time progresses, such that the spatial expansion in their region has slowed below light speed? AG 

As for black holes, when they eject material, it comes from the accretion disk, not the interior. Excess inflowing matter, under extreme magnetic fields and radiation pressure, is expelled before crossing the event horizon. Once inside, nothing escapes.

That might not be true if all the mass/energy of the universe originated as a BH, which we can identify as the BB. Doesn't the ultra high temperature with all mass/energy concentrated nearly as a spatial singularity at this BB cause a BH to form? AG 

Already answered.

Please copy and paste your answer.

No, use your own fingers.

I forgot where that was posted. AG

If the universe is infinite in spatial extent, and we run the clock backward, is all  the mass/energy of the observable region confined to a tiny or zero volume? What happens to the mass/energy of the unobservable region? TY, AG

Did you answer the above question? AG 

Yes, multiple times.

Quentin

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

Le mar. 18 mars 2025, 16:54, Alan Grayson <agrays...@gmail.com> a écrit :

On Monday, March 17, 2025 at 5:03:42 PM UTC-6 Quentin Anciaux wrote:

I have been reflecting on the idea that our universe could be the interior of a giant black hole, but several fundamental questions arise.

How can this account for the apparent flatness of the universe, given that a black hole’s interior should exhibit strong curvature? Observations indicate that our universe is nearly flat, yet this hypothesis lacks a clear mechanism to explain why.

If we are inside a black hole, where is the boundary? A black hole's internal space-time is inherently limited by the event horizon, yet our observable universe does not show any indication of such a constraint. How does this model reconcile the absence of an observable edge?

Furthermore, in classical black hole physics, the event horizon expands only when additional mass or energy is absorbed. In contrast, our universe’s observable horizon grows over time without any apparent external input. What mechanism would drive this expansion in a black hole framework?

These points suggest that such a model would require an unconventional and exotic space-time structure beyond classical general relativity. I would appreciate any insights on how these issues could be addressed.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

When you refer to the horizon expanding of the observable universe, are you now assuming the universe is expanding spatially, rather than just the average galactic distances increasing? BTW, I'm confused about how that horizon increases spatially. Aren't the galaxies in the unobservable regions receding faster than light speed, and this is the reason they're unobservable for us? If so, how can the observable region increase so some of them become part of the observable region? One other thing; I viewed a video showing BH's releasing material when too much is inflowing. Is some of this material from the interior, or is all of it inflowing material that is rejected? AG 

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[Alan Grayson]

I didn't understand it, so I wanted to study it again. But the better solution is this; let's just fuck it!  AG 

[John Clark]

On Wed, Mar 19, 2025 at 4:30 AM Alan Grayson <agrays...@gmail.com> wrote:

> If the universe is infinite in spatial extent, and we run the clock backward, is all  the mass/energy of the observable region confined to a tiny or zero volume?

The short answer is nobody knows what will happen if you run the clock back to zero, and the mystery remains regardless of if the universe is finite or infinite. Nobody knows what will happen when things get super small because our two best physical theories, Quantum Mechanics and General Relativity, disagree with each other. Most believe that something will prevent a zero volume from ever occurring, but nobody knows what that "something" is.  

  John K Clark    See what's on my new list at  Extropolis

23x

[Alan Grayson]

Maybe it's a 5th force. What I'd like to know is this; assuming an infinite spatial universe and that it gets very very small as we run the clock backward, the observable regions shrinks, but what happens to the unobservable region? Quentin claimed to have an answer, but I can't recall what it was. AG 

23x

[John Clark]

On Wed, Mar 19, 2025 at 7:56 AM Alan Grayson <agrays...@gmail.com> wrote:

 > assuming an infinite spatial universe and that it gets very very small as we run the clock backward, the observable regions shrinks, but what happens to the unobservable region?

It makes no difference if it's infinite or finite, if inflation is correct then if you go back to just after inflation stopped then things that are unobservable now would have been unobservable then, but if you go back before inflation started everything would've been observable, that's why the temperature of the Cosmic Background Radiation is at the same 2.7° kelvin temperature even for spots in the sky that are 180° away from each other; without inflation there was never enough time for light to go from one of those spots to the other, they were just too far from each other, but with inflation at one time those two distant spots were in causal contact with each other and the temperature could have evened out.  

  John K Clark    See what's on my new list at  Extropolis

ktb

[Quentin Anciaux]

Well guess I have to use my fingers for you... you know any decent email client has a search function:

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.

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. 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—but its density can still increase without bound. There’s no contradiction.

Quentin 

This is *one* of numerous answers given.

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

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[Alan Grayson]

On Wednesday, March 19, 2025 at 6:44:47 AM UTC-6 Quentin Anciaux wrote:

Well guess I have to use my fingers for you... you know any decent email client has a search function:

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.

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. 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—but its density can still increase without bound. There’s no contradiction.

If average galactic distances decrease as we go back in time, the density increases locally everywhere without limit in the unobservable region. Won't this be a singularity of infinite density everywhere as T decreases to zero? AG

[Quentin Anciaux]

Yes, if we extrapolate the standard Big Bang model backward in time, the density increases everywhere without bound as T approaches zero. In an infinite universe, this means every region, even in the unobservable part, reaches arbitrarily high density simultaneously. This is why the Big Bang is often described as a singularity in time, not in space—it’s not a localized point, but rather a state where all of space was at infinitely high density at the same time.

However, in modern cosmology, the singularity at T=0  is generally considered an indication that our current physical theories break down rather than an actual point of "infinite density everywhere." Quantum gravity effects (which we don’t yet fully understand) would likely smooth out this singularity, preventing true infinite density. Inflationary models also suggest that what we call the "Big Bang" may not be a singular beginning but instead a transition from a pre-existing state (such as a quantum fluctuation, an eternal inflation scenario, or a bounce from a prior contracting phase).

So, while classical general relativity predicts a singularity of infinite density everywhere as T -> 0, most physicists suspect this is a limitation of the theory, and quantum gravity will provide a more complete picture.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

To view this discussion visit https://groups.google.com/d/msgid/everything-list/d3770fa7-6df0-42d7-a3ce-a48f01951391n%40googlegroups.com.

[Alan Grayson]

On Wednesday, March 19, 2025 at 8:22:35 AM UTC-6 Quentin Anciaux wrote:

Yes, if we extrapolate the standard Big Bang model backward in time, the density increases everywhere without bound as T approaches zero. In an infinite universe, this means every region, even in the unobservable part, reaches arbitrarily high density simultaneously. This is why the Big Bang is often described as a singularity in time, not in space—it’s not a localized point, but rather a state where all of space was at infinitely high density at the same time.

 

That's what I recall, but it seems ridiculous so I didn't want to state it. AG

However, in modern cosmology, the singularity at T=0  is generally considered an indication that our current physical theories break down rather than an actual point of "infinite density everywhere." Quantum gravity effects (which we don’t yet fully understand) would likely smooth out this singularity, preventing true infinite density. Inflationary models also suggest that what we call the "Big Bang" may not be a singular beginning but instead a transition from a pre-existing state (such as a quantum fluctuation, an eternal inflation scenario, or a bounce from a prior contracting phase).

So, while classical general relativity predicts a singularity of infinite density everywhere as T -> 0, most physicists suspect this is a limitation of the theory, and quantum gravity will provide a more complete picture.

 

I personally doubt there will ever be a quantum theory of gravity. A repulsive fifth force seems like a simpler possible solution. Is there any substantive objection to this conjecture? AG 

[Cosmin Visan]

We are living in consciousness.

[Brent Meeker]

All theories treat the unobservable regions as being similar to the observable (what else could you justify?).  So every finite region, observable or not shrinks to zero. 

Brent

[Brent Meeker]

Right.  Which is why nobody believes that limiting case obtains.

Brent

[Alan Grayson]

But if every finite subset of an infinite set strinks to zero, in the case the assumed infinite set is the spatial extent of the universe, won't the infinite spatial set of the universe also shrink to zero (which is what Quentin denies)? AG

[Alan Grayson]

For example, the integers is an infinite set and can be covered, that is contained within, a countable set of finite subsets. AG

[Brent Meeker]

No.

Brent

[Alan Grayson]

But, as I've shown, this contradicts basic set theory. AG 

[Brent Meeker]

Basic set theory has no metric.  Shrink to zero in meaningless for a set.

Brent

[Cosmin Visan]

@Brent. The only thing that you ever observe is your own consciousness. Which undoubtedly does a great job at tricking you into believing that you observe an "external world".

[Alan Grayson]

"No" isn't an argument. It's just a claim. My argument is based on set theory and topology. If an infinite set can be contained in a countable set of finite sets, and if they represent spacetime, and each shrinks to zero, then so will the original infinite set. But maybe the infinite set of spacetime points cannot be contained in a countable set, in which case we'd have to use the Axiom of Choice. But I'm not sure if the infinite set of spacetime points can be covered or contained in an uncountable set created by applying the Axiom of Choice. In any event, you need an argument to establish your claim. AG 

[Alan Grayson]

On Thursday, March 20, 2025 at 1:40:02 AM UTC-6 Cosmin Visan wrote:

@Brent. The only thing that you ever observe is your own consciousness. Which undoubtedly does a great job at tricking you into believing that you observe an "external world".

The only trick here is your usual one; thinking you've written something useful. AG 

[Cosmin Visan]

@Alan. You don't understand infinity. Infinity is God. Set theory is people thinking that the forms that they see in their consciousness are all there is (indeed they are all there is), but there is also the formless part that gives rise to the forms. And in any final analysis of reality you have to take them both into account, otherwise you end up in paradoxes.

[Alan Grayson]

The entire universe can be covered with a countable set of 4 dimensional balls, each centered at integer clock readings, with unit radii, each ball includes its boundary. No need in this model for applying the Axiom of Choice. Each ball is infinite in the number of events it contains, and each is closed since it contains its boundary, so we can consider each ball as a finite region of spacetime. As time runs backward, each ball shrinks as close to zero as desired, and ISTM that the entire universe shrinks with it. How can the universe remain infinite in spatial extent in this situation? AG

[Alan Grayson]

On Thursday, March 20, 2025 at 2:16:03 AM UTC-6 Cosmin Visan wrote:

@Alan. You don't understand infinity. Infinity is God.

How can you know that? Well, the good news is that at least now, you're not speculating about my sexual life. AG

 

Set theory is people thinking that the forms that they see in their consciousness are all there is (indeed they are all there is), but there is also the formless part that gives rise to the forms.

I've seen that, quite terrifying since in the formless state we can't think or speak, since those functions only work when we have form, human form. The terror is the lurking fear that once in the formless state, we can't exit from it. sAG

 

And in any final analysis of reality you have to take them both into account, otherwise you end up in paradoxes.

Paradoxes can originate from other states as well. AG 

[Quentin Anciaux]

AG, your reasoning assumes that because each countable 4D ball shrinks arbitrarily close to zero, the entire universe must shrink as well. This misinterprets how infinity works in both set theory and general relativity.

Shrinking finite regions doesn’t imply a finite universe. Each of your 4D balls represents a finite spacetime region, but an infinite number of shrinking finite regions does not make the total universe finite. Even if every individual region shrinks, an infinite set of them still covers all of space, preserving its infinite extent.

The universe can remain infinite despite local contraction. Imagine an infinite 1D line divided into shrinking segments. Each segment gets smaller, but since there are infinitely many, the total length remains infinite. The same applies in higher dimensions: even as each 4D ball shrinks, the universe as a whole remains infinite because there is no bound on the number of shrinking regions.

General relativity allows an infinite universe to contract everywhere without requiring a finite total volume. This is why an infinite universe can undergo a Big Bang—density increases everywhere without demanding a global contraction.

Your argument assumes a globally shrinking boundary, implying that these 4D balls define the total size of the universe. But in an infinite universe, no such global boundary exists. There is no edge where "shrinking" causes the entire structure to collapse into a finite size.

An infinite universe remains infinite while every finite region contracts. Your logic would only apply if the universe were globally finite from the start. Since an infinite universe has no fixed size to contract, space simply becomes denser everywhere as you go back in time.

Quentin 

All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)

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[Alan Grayson]

On Thursday, March 20, 2025 at 6:11:01 AM UTC-6 Quentin Anciaux wrote:

AG, your reasoning assumes that because each countable 4D ball shrinks arbitrarily close to zero, the entire universe must shrink as well. This misinterprets how infinity works in both set theory and general relativity.

Shrinking finite regions doesn’t imply a finite universe. Each of your 4D balls represents a finite spacetime region, but an infinite number of shrinking finite regions does not make the total universe finite. Even if every individual region shrinks, an infinite set of them still covers all of space, preserving its infinite extent.

The universe can remain infinite despite local contraction. Imagine an infinite 1D line divided into shrinking segments. Each segment gets smaller, but since there are infinitely many, the total length remains infinite. The same applies in higher dimensions: even as each 4D ball shrinks, the universe as a whole remains infinite because there is no bound on the number of shrinking regions.

General relativity allows an infinite universe to contract everywhere without requiring a finite total volume. This is why an infinite universe can undergo a Big Bang—density increases everywhere without demanding a global contraction.

Your argument assumes a globally shrinking boundary, implying that these 4D balls define the total size of the universe.

Their union does define the total size of the universe if they cover it, which they do. Your general argument is likely correct, but to be sure we have to deal with the convergence value of this union as the balls shrink in volume. AG

[Brent Meeker]

On 3/20/2025 1:12 AM, Alan Grayson wrote:

On Wednesday, March 19, 2025 at 11:49:50 PM UTC-6 Brent Meeker wrote:

On 3/19/2025 10:09 PM, Alan Grayson wrote:

On Wednesday, March 19, 2025 at 10:50:41 PM UTC-6 Brent Meeker wrote:

On 3/19/2025 9:14 PM, Alan Grayson wrote:

On Wednesday, March 19, 2025 at 3:28:40 PM UTC-6 Brent Meeker wrote:

On 3/19/2025 4:56 AM, Alan Grayson wrote:

On Wednesday, March 19, 2025 at 5:40:48 AM UTC-6 John Clark wrote:

On Wed, Mar 19, 2025 at 4:30 AM Alan Grayson <agrays...@gmail.com> wrote:

> If the universe is infinite in spatial extent, and we run the clock backward, is all  the mass/energy of the observable region confined to a tiny or zero volume?

The short answer is nobody knows what will happen if you run the clock back to zero, and the mystery remains regardless of if the universe is finite or infinite. Nobody knows what will happen when things get super small because our two best physical theories, Quantum Mechanics and General Relativity, disagree with each other. Most believe that something will prevent a zero volume from ever occurring, but nobody knows what that "something" is.  

  John K Clark    See what's on my new list at  Extropolis

Maybe it's a 5th force. What I'd like to know is this; assuming an infinite spatial universe and that it gets very very small as we run the clock backward, the observable regions shrinks, but what happens to the unobservable region? Quentin claimed to have an answer, but I can't recall what it was. AG

All theories treat the unobservable regions as being similar to the observable (what else could you justify?).  So every finite region, observable or not shrinks to zero. 

Brent

But if every finite subset of an infinite set strinks to zero, in the case the assumed infinite set is the spatial extent of the universe, won't the infinite spatial set of the universe also shrink to zero (which is what Quentin denies)? AG

No.

Brent

But, as I've shown, this contradicts basic set theory. AG

Basic set theory has no metric.  Shrink to zero in meaningless for a set.

Brent

"No" isn't an argument. It's just a claim. My argument is based on set theory and topology. If an infinite set can be contained in a countable set of finite sets,

But that's not the case.  The number for finite sets is, hypothetically, infinite.  Space is a continuum, an order alpha1 infinity.

We should get back to what is actually shown by the FLRW model.  It assumes the universe isotropic and so can be characterized by a scale factor, a.  So the only variables are a and time t.  Parameters are pressure and mass/energy density which depend on a.  Our present state is taken to be the boundary condition at a=1.  The the solution can be propagated into the future and into the past.  In the past a goes to zero.  In the future it can expand toward and asymptotic limit, expand without limit, or contract to zero.  All this is calculus, so it's assuming a continuum of spacetime.  The set theory measure of every piece of spacetime is the same alpha1 infinity.

Brent

and if they represent spacetime, and each shrinks to zero, then so will the original infinite set. But maybe the infinite set of spacetime points cannot be contained in a countable set, in which case we'd have to use the Axiom of Choice. But I'm not sure if the infinite set of spacetime points can be covered or contained in an uncountable set created by applying the Axiom of Choice. In any event, you need an argument to establish your claim. AG 

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[Alan Grayson]

On Thursday, March 20, 2025 at 11:38:17 AM UTC-6 Brent Meeker wrote:

"No" isn't an argument. It's just a claim. My argument is based on set theory and topology. If an infinite set can be contained in a countable set of finite sets,

But that's not the case.  The number for finite sets is, hypothetically, infinite.  Space is a continuum, an order alpha1 infinity.

We should get back to what is actually shown by the FLRW model.  It assumes the universe isotropic and so can be characterized by a scale factor, a.  So the only variables are a and time t.  Parameters are pressure and mass/energy density which depend on a.  Our present state is taken to be the boundary condition at a=1.  The the solution can be propagated into the future and into the past.  In the past a goes to zero.  In the future it can expand toward and asymptotic limit, expand without limit, or contract to zero.  All this is calculus, so it's assuming a continuum of spacetime.  The set theory measure of every piece of spacetime is the same alpha1 infinity.

Brent

Concerning your last sentence above, we consider the observable region as finite, because it has a closed boundary, even though the number of events within are an alpha1 infinity. AG 

[Alan Grayson]

On Thursday, March 20, 2025 at 6:11:01 AM UTC-6 Quentin Anciaux wrote:

AG, your reasoning assumes that because each countable 4D ball shrinks arbitrarily close to zero, the entire universe must shrink as well. This misinterprets how infinity works in both set theory and general relativity.

Shrinking finite regions doesn’t imply a finite universe. Each of your 4D balls represents a finite spacetime region, but an infinite number of shrinking finite regions does not make the total universe finite. Even if every individual region shrinks, an infinite set of them still covers all of space, preserving its infinite extent.

The universe can remain infinite despite local contraction. Imagine an infinite 1D line divided into shrinking segments. Each segment gets smaller, but since there are infinitely many, the total length remains infinite. The same applies in higher dimensions: even as each 4D ball shrinks, the universe as a whole remains infinite because there is no bound on the number of shrinking regions.

General relativity allows an infinite universe to contract everywhere without requiring a finite total volume. This is why an infinite universe can undergo a Big Bang—density increases everywhere without demanding a global contraction.

Your argument assumes a globally shrinking boundary, implying that these 4D balls define the total size of the universe. But in an infinite universe, no such global boundary exists. There is no edge where "shrinking" causes the entire structure to collapse into a finite size.

An infinite universe remains infinite while every finite region contracts. Your logic would only apply if the universe were globally finite from the start. Since an infinite universe has no fixed size to contract, space simply becomes denser everywhere as you go back in time.

Quentin 

As each 4D ball shrinks, they continue to cover spacetime. Now IF the shrinking is asymmetrical, the sum of the radii could still become finite, as in examples of sum of series. For example, the series 1 + 1/2 + 1/3 ... diverges, but not if each denominator is squared. This is what I meant earlier when I wrote we have to take convergence into account. AG 

[Alan Grayson]

On Monday, March 17, 2025 at 7:53:46 AM UTC-6 Alan Grayson wrote:

James Webb’s survey of 263 galaxies hints at yes

https://interestingengineering.com/science/living-inside-black-hole-james-webb

Critique of the claim:  https://www.youtube.com/watch?v=jPXbFeaZS6c   AG