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Eldar Black Holes

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Re: Eldar Black Holes

#51

Earlier quoted context omitted.

We are in a black hole. The event horizon of the entire universe is on the same order as the observable universe. We are inside the black hole of the universe.

What?

The grandparent may be referring to the cosmic event horizon.

https://en.wikipedia.org/wiki/Event_horizon#Cosmic_event_hor...

Re: Eldar Black Holes

#52
post #49

Earlier quoted context omitted.

Here's something I've wondered about black holes, related to what's inside. Simplistically, there must be mass inside, i.e., every black hole has a mass that can somehow be measured, e.g., by orbital velocities of satellites. And the mass-energy has to equal the mass-energy that has fallen in. So far so good. But the stuff that falls in is not purely described by its mass. It also has angular momentum, electrical cha…

You have almost formulated the no-hair theorem. https://en.wikipedia.org/wiki/No-hair_theorem

I never thought of that in the context of strangeness, lepton number, and other conserved quantities. I don't think strangeness is really measurable (and I don't remember if it's technically conserved), but black holes should probably preserve lepton number somehow. Is that a quantum gravity sort of problem?

Re: Eldar Black Holes

#53
post #36
post #32

Earlier quoted context omitted.

> https://www.youtube.com/watch?v=vNaEBbFbvcY This is mind blowing...shatters my misconception of blackholes....is there any more books on this?

It was interesting to watch, but the presenter presents everything as truth, but aren’t many of his explanations still theories? I’d like to see what other competing theories there are..

I think most of what he said is just an interpretation of what the math of classical black-holes says (basically the Schwartzschild equation). This math is uncontroversial and there is no better theory of a black hole, at least at this level of detail.

If I understand correctly competing theories disagree on more complicated descriptions, those that ask different questions or want to describe more details.

Re: Eldar Black Holes

#54
post #8

There is a fascinating PBS Space Time video[1] about black holes that questions the very existence of whatever is "inside" a black hole. They point out that as you approach a black hole, your proper time is advancing slower and slower when compared to an observer located far away from the black hole (like us, on Earth). That means that from the point of view of this far observer, nothing happens inside a black hole u…

That's the thing that never made sense to me about the black holes. The closer you are to the event horizon, the faster the time passes for the universe around you. So reaching the event horizon should take infinite amount of the "outside time", so right before you reach the horizon, you should see the whole future of the universe, including its end, if there's any. So how do black holes gain any mass then?

First you have to define mass. It's currently "defined" extrinsically, by a piece of metal machined by the SI. That doesn't allow an intrinsic answer definition of a black holes mass.

The answer is kinda easy if I can make up my own intrinsic definition. The mass is the mass of the stuff around the black hole. A black hole is a singular point, it can't have mass, don't be silly.

Re: Eldar Black Holes

#55
post #11

Earlier quoted context omitted.

I imagine this as time asymptotically slowing as you approach the singularity so that the singularity is forever stuck at the time of the supernova explosion that gave birth to it. You can never reach it because you and your movements too, slow down the closer you get. Is that correct?

A traveler can reach it all right, but only from his own point of view. From the point of view of almost everyone else in the Universe, including us on Earth, it will never ever reach it. It's like the traveler has jumped into an other universe "located" in an infinitely distant future.

So let's say I fall into a black hole. And then four billion years later, someone else falls into a black hole from the same direction. From an outside perspective at a point nearly infinitely far away in time, we would seem to slow until we are right next to each other at the event horizon, correct? Does this mean everything that falls into a black hole crosses the event horizon (from their perspective) at the same moment, a moment which only exists from the crossers' perspective, as it is always infinitely far away from a perspective outside the event horizon?

Re: Eldar Black Holes

#56
post #35

Earlier quoted context omitted.

That's the thing that never made sense to me about the black holes. The closer you are to the event horizon, the faster the time passes for the universe around you. So reaching the event horizon should take infinite amount of the "outside time", so right before you reach the horizon, you should see the whole future of the universe, including its end, if there's any. So how do black holes gain any mass then?

Doesn't it mean that only the space around the black hole sees that "infinite amount of time" pass, and not the whole universe? So in that case, you wouldn't be seeing the "future of the universe" just the "future" (I guess) of the space around the black hole. I kind of see blackholes in space as vortexes in a lake. Anything that gets "trapped" in the vortex moves much faster, including the water (space-time) itself.…

> including the water (space-time)

I think you meant to say ether.

Re: Eldar Black Holes

#57
post #8

There is a fascinating PBS Space Time video[1] about black holes that questions the very existence of whatever is "inside" a black hole. They point out that as you approach a black hole, your proper time is advancing slower and slower when compared to an observer located far away from the black hole (like us, on Earth). That means that from the point of view of this far observer, nothing happens inside a black hole u…

Between reality and maths, the maths are the more fundamental thing that is used to explain reality. What you call reality is just some circumstances that your brain got used to.

Re: Eldar Black Holes

#58
post #8

There is a fascinating PBS Space Time video[1] about black holes that questions the very existence of whatever is "inside" a black hole. They point out that as you approach a black hole, your proper time is advancing slower and slower when compared to an observer located far away from the black hole (like us, on Earth). That means that from the point of view of this far observer, nothing happens inside a black hole u…

That's the thing that never made sense to me about the black holes. The closer you are to the event horizon, the faster the time passes for the universe around you. So reaching the event horizon should take infinite amount of the "outside time", so right before you reach the horizon, you should see the whole future of the universe, including its end, if there's any. So how do black holes gain any mass then?

There are two frames of reference here, and only from the frame of the external observer does what you say hold true. From the point of view of infalling mass, there is no “freeze-frame” and time proceeds normally. The classic example to illustrate this is a black hole with so much mass that you can fall past the event horizon without experiencing significant tidal forces. You could survive the fall, Andy live for hours inside the hole before tidal forces turned you into subatomic sphagetti.

Re: Eldar Black Holes

#59
post #18
post #8

There is a fascinating PBS Space Time video[1] about black holes that questions the very existence of whatever is "inside" a black hole. They point out that as you approach a black hole, your proper time is advancing slower and slower when compared to an observer located far away from the black hole (like us, on Earth). That means that from the point of view of this far observer, nothing happens inside a black hole u…

off-topic a bit: does anyone have suggestions for paths for the layperson toward being able to reason and intuit about this stuff at one level beyond pop physics claptrap? I have heard "the theoretical minimum" suggested in the past, but I haven't heard from anyone who has actually used it to go from zero to say, general relativity, only people who think it sounds good. It also seems like a steep investment -- I just…

There are for-hire physicist you could pay for consultations:

https://aeon.co/ideas/what-i-learned-as-a-hired-consultant-f...

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