this post was submitted on 13 Aug 2023
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Cover author: Michał Kałużny http://astrofotografia.pl/
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I'm also no authority, but I strongly disagree that "it follows" that the stuff must be coming out.
We know that stuff enters black holes, and we know that they gain mass when it does. We think they shrink in mass over extreme periods of time, but other than that, I'm fairly sure we've never seen a black hole lose mass.
So if the mass comes out in a white hole, why does the black hole retain its mass?
I haven't read the book but I can't imagine he says, without strongly stating that it's very speculative, that such a thing could happen.
@exscape
@readbeanicecream
By definition, a manifold has a place where things go in, and other things come out. So yes, it does in fact logically follow. If its a manifold, then it logically follows that what goes in comes out.
You're saying we know a bunch of stuff I'm not certain we know.
My understanding is that by definition, the singularity has infinite mass and infinite gravity, so there is no way it can gain mass; because infinity + 1 = infinity. It's the very nature of infinities. You can have a number of infinities, but manipulating them arithmetically always yields infinity. 2 x infinity = infinity. 3 / infinity = infinity.
Like zero, it is more identity than number. 0 = nothing, infinity = everything.
So if you hope to have me follow your narrative, you're going to address this assertion concerning increasing the mass of black holes first.
Almost nobody actually believes the singularity is real, it's just what the math tells us -- it's where the math of GR breaks down, and a better theory of gravity would be needed to resolve it.
I've never heard a black hole described as a manifold, but then again I'm not sure exactly what a manifold is.
@exscape
@readbeanicecream
A couple examples of manifolds:
exhaust manifold on combustion engine takes raw cylinder exhaust gases in pipes that all come down and combine into a single larger pipe that connects to the input of a catalytic converter.
the plenum in your attic is a manifold. One big duct runs from your air handler into a box with several ducts coming from it, delivering air to each of the vents. the ducts and the plenum form a manifold.
In literature, it means 'many and various'.
In mathematics, "a collection of points forming a certain kind of set, such as those of a topologically closed surface or an analog of this in three or more dimensions"
In Kantian philosophy, "the sum of the particulars furnished by sense before they have been unified by the synthesis of the understanding"
Origins: Old English manigfeald ; current noun senses date from the mid 19th century.
All from the wikipedia
They all have some descriptive relevance, but the one that really counts for us is the math one, suggesting the closed surface.
It wouldn't surprise me though if it still worked; there are many examples of topologically closed surfaces that can still be traversed, if in unexpected ways. I'm thinking of another manifold, the klein bottle, and of course the mobieus strip.