AG, the key issue is that the universe isn’t collapsing into a localized region—it’s expanding/collapsing everywhere. A black hole forms when mass collapses within a surrounding spacetime, creating an event horizon. The early universe, however, was homogeneous and isotropic on large scales, meaning there was no "outside" region for an event horizon to form around it.
In GR, a universe that contracts to extremely high density doesn’t necessarily become a black hole—it follows different equations that describe a hot, dense state rather than a localized collapse. The FLRW metric describes a global evolution of spacetime, not a local gravitational collapse like a black hole. That’s why the early universe could be dense without forming a black hole—it didn’t have a surrounding spacetime to collapse into. Quentin Le mer. 19 févr. 2025, 09:33, Alan Grayson <[email protected]> a écrit : > > > On Tuesday, February 18, 2025 at 11:19:45 PM UTC-7 Alan Grayson wrote: > > On Monday, February 17, 2025 at 11:59:45 PM UTC-7 Alan Grayson wrote: > > [image: Alan Grayson's profile photo] > Alan Grayson > 11:56 PM (1 minute ago) > > > > to Everything List > Running the clock backward, and assuming the physical size of the universe > converges to a singularity with zero volume at T=0, will it form a Black > Hole? TY, AG > > > Let me pose the problem differently; if the entire *universe* contracted > to almost zero volume, is there anything we know that would prevent it from > becoming a BH? 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/fee93dd9-e889-429d-8984-1a1a1d30aba8n%40googlegroups.com > <https://groups.google.com/d/msgid/everything-list/fee93dd9-e889-429d-8984-1a1a1d30aba8n%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/CAMW2kArL5cDdaUfctX2Cr60Ov5-_KSU2FxhYUin75pBzC9yrWw%40mail.gmail.com.
