Black Hole Hunting

Posted May 7, 2021 16:37 UTC (Fri) by zlynx (guest, #2285)
In reply to: Black Hole Hunting by Wol
Parent article: Development quote of the week

Because of the theoretical time dilation at the event horizon you really can't say anything about the "actual size" of the black hole. It's surface is frozen in time just below that horizon from our point of view.

Possibly, in theory, from the black hole's reference frame it continues to collapse and the entire universe outside collapsed into it instantly.

I remember reading about some wild theories that our universe is the inside of a black hole from another universe and the Big Bang is the collapse of several galaxies worth of mass/energy from the outside.

Black Hole Hunting

Posted May 19, 2021 17:23 UTC (Wed) by nix (subscriber, #2304) [Link]

The fun thing about this degree of spacetime distortion is that the topology of these things is demented: from some reference frames (not those outside the hole, obviously), the spacetime inside a black hole's event horizon expands constantly. *Fast*. Ludicrously fast.

It's a bit hard to find papers that describe this in comprehensible fashion to a layman, but they usually say things things like every (ridiculously tiny space interval) inflates e-fold times per (ridiculously tiny time interval) for the entire lifetime of the hole. When I say ridiculously tiny, I mean bigger than the Planck scale but not by much. So the inside of a black hole of any age is going to be an *immense* region, likely vastly bigger than the entire observable universe for almost any hole of reasonable age, and growing more immense all the time -- not that you can ever tell because anyone who can tell is on a one-way trip and cannot communicate outwards... and probably spaghettified as well.