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 <[email protected]> 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 <[email protected]> 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 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 <[email protected]> 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 -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/0534ced9-b434-4ba0-8d54-070aa9241fbfn%40googlegroups.com <https://groups.google.com/d/msgid/everything-list/0534ced9-b434-4ba0-8d54-070aa9241fbfn%40googlegroups.com?utm_medium=email&utm_source=footer> . -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/1f59ad4b-eafd-42e1-95f3-1d1626005f20n%40googlegroups.com.
