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Are Black Holes Actually Dark Energy Stars?

nautil.us

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Re: Are Black Holes Actually Dark Energy Stars?

#91

Post by codethief »

dsnuh wrote: post #82
philipov wrote: post #61

Earlier quoted context omitted.

It's usually referred to as a fabric because in general relativity, spacetime is dynamic, as if it were on a fabric that could stretch and contract in response to the density of matter occupying it. This is where the rubber-sheet analogy comes from. As for what it is made of, that is one of the great open questions in theoretical physics right now, but also possibly where the analogy breaks down. Because of Lorentz I…

Thanks for linking to the video, it was the most informative handling of the subject I have seen. After watching, I have a question, please forgive if it is ridiculous or displays some fundamental problem with my layman's understanding of the subject. If time becomes space-like, and space becomes time-like, can we think of black holes as "time stars"? Would every black hole within our observable universe contain info…

I'm afraid I don't have the time to watch the entire video but, being a physicist, I can still try to answer your questions. Currently, however, your question

> If time becomes space-like, and space becomes time-like, can we think of black holes as "time stars"?

doesn't make much sense to me. Time does not become spacelike nor does space become timelike. In General Relativity, time and space are not individually defined in an observer-independent fashion in the first place. The terms we use instead are "timelike directions" and "spacelike directions" as well as timelike / spacelike hypersurfaces because they are defined in such a way that all observers will agree on whether a direction / hypersurface is timelike / spacelike. So now that we've replaced the terms "time" and "space" with "timelike" and "spacelike", I hope you'll see that your question is not exactly well-defined.

But maybe I'm misunderstanding you, so please feel free to elaborate on your questions. (Or to point me to an explanation from the video in case you're referring to one.)

As for your second question:

> Would every black hole within our observable universe contain information from all light cones within the observable universe? In other words, would different black holes contain different information?

I'm afraid I can't follow this question, either. Would you mind rephrasing it? My initial impression is that you might have a wrong idea of what a lightclone is.

Re: Are Black Holes Actually Dark Energy Stars?

#92

Post by czbond »

joe-collins wrote: post #17
chc wrote: post #2

I've seen a couple of articles about this guy recently and they both struck me as weirdly credulous given the apparently complete lack of evidence supporting his theory and the fact that approximately no other scientists seem to find it credible.

At least at the pop-science level, his ideas connect a lot of dots. He'd neatly resolve the weirdness and mystery of black holes, their jets, their information paradox, and dark energy. It feels good. Whether or not any of it makes a lick of sense once you start actually crunching numbers is another question. The lack of interest from other scientists leaves me skeptical (even if I'm silently enamored of the neatness…

Never trust credentials for "leaps and bounds thinking". Trust credentials for incremental, linear thinking....

Re: Are Black Holes Actually Dark Energy Stars?

#93

Post by codethief »

dsnuh wrote: post #86
philipov wrote: post #84

Earlier quoted context omitted.

I'm not an expert either, but according to the treatments I've seen on GR, the flipping of time and space inside of black holes is just an artifact of the choice of coordinates, and can be fixed by changing your coordinate system. However, there are some ideas based on holography for solving the black hole information paradox that posit that it doesn't even make sense to talk about the inside and outside of a black h…

Thanks for the detailed reply! One point that was made in the video was that inside a black hole, space is collapsing faster than light. This seems like more than a change to coordinate system? Doesn't this mean that time is also moving faster than light? Could time effectively become "solid" at the singularity, with all events within the black hole's light cone at a single point in time, but in infinite space(ignori…

> One point that was made in the video was that inside a black hole, space is collapsing faster than light. This seems like more than a change to coordinate system?

No, this refers to the fact that inside a black hole you can travel as fast as you want and do whatever you want but even if you move around at the speed of light, you still won't be able to escape the singularity. This is because the singularity is a so-called timelike singularity – it lies in your future. It's not a point in space somewhere that you can walk around and poke; while you're in the black hole, it's actually completely invisible to you until you hit it. You can basically compare the singularity to your own death: While you can't see it right here and right now but you know for sure that you'll reach it at some point in your future.

A physicsy way of saying all this is that, inside the black hole, all future-directed worldlines emanating from a given spacelike surface will converge and eventually hit the singularity. (This is what Nima Arkani-Hamed means when he says that space "collapses".) Another way of saying this is that the aforementioned surface is a so-called trapped surface.

Back to a more intuitive explanation: In a way, falling into a black hole and towards the singularity is like falling down a waterfall: Once you've stepped over the edge (crossed the event horizon), you certainly won't be able to stop yourself from falling anymore. You cannot fall up and escape gravity.

Here's a website which explains this way of looking at black holes as "waterfalls" of space a bit further: https://jila.colorado.edu/~ajsh/insidebh/waterfall.html

> Doesn't this mean that time is also moving faster than light?

As mentioned in my other comment, I recommend steering clear of the terms "time" and "space" as those are not individually well-defined and equally agreed upon by all observers. Instead, time and space are relative – if I use a different coordinate system than you, we will have very different notions of which events occur at the same point in time (and are thus part of the same spatial slice). It's called relativity for a reason. :)

So, my counter question to your question would be:

> Time as measured by whom? ;)

But even if you define time with respect to a given observer, it still does not "move" or have a "velocity" that you could compare to the speed of light. Only massive objects actually move through spacetime and only when they're close enough, you can compare their relative velocities.

Re: Are Black Holes Actually Dark Energy Stars?

#94

Post by dsnuh »

codethief wrote: post #91
dsnuh wrote: post #82

Earlier quoted context omitted.

Thanks for linking to the video, it was the most informative handling of the subject I have seen. After watching, I have a question, please forgive if it is ridiculous or displays some fundamental problem with my layman's understanding of the subject. If time becomes space-like, and space becomes time-like, can we think of black holes as "time stars"? Would every black hole within our observable universe contain info…

I'm afraid I don't have the time to watch the entire video but, being a physicist, I can still try to answer your questions. Currently, however, your question > If time becomes space-like, and space becomes time-like, can we think of black holes as "time stars"? doesn't make much sense to me. Time does not become spacelike nor does space become timelike. In General Relativity, time and space are not individually defi…

I just realized I was replying to the wrong parent comment! So sorry. I was talking about a PBS Space Time episode on YouTube I saw in (or came across via) a different comment.

https://youtu.be/KePNhUJ2reI

Re: Are Black Holes Actually Dark Energy Stars?

#95

Post by njarboe »

bsder wrote: post #87
diegoperini wrote: post #19

Earlier quoted context omitted.

If what LIGO achieved is not loud enough for the 21st century, then we are probably doomed. It is a NEW kind of telescope that has not even been utilized for 1% of its potential. PS: I'm not arguing with your statement, you have all the right to think that way. Maybe even people who lived during Einstein's earlier times thought the same for their previous century.

> If what LIGO achieved is not loud enough for the 21st century, then we are probably doomed. The problem is that it is REALLY hard to describe to the layman just how excruciatingly difficult it is to do what LIGO does. I like to think that I know a thing or two about electrical engineering and quantum mechanics, and even I probably don't get just exactly how amazing LIGO is.

The original paper on the first detection of a black hole merger by LIGO is really great[1]. It's even open access. Much of the paper is accessible to someone at the freshman physics level. Download the pdf as it is in a much nicer format than the online version.

[1]https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.11...

Re: Are Black Holes Actually Dark Energy Stars?

#96

Post by codethief »

0898 wrote: post #15
takk309 wrote: post #9

Earlier quoted context omitted.

Would this be one way that information would not be destroyed, at least from the reference frame of the outside observer?

Question if you don't mind. This "information being destroyed" thing. What do they mean by information? Isn't information a human construct? How is the universe supposed to know what information is?

There're different levels of making this statement precise. Here's one:

Physics is a deterministic theory, even at a quantum level where we call determinism unitarity. (Leaving the measurement problem & collapse of the wave function aside for a moment.)

Determinism means, we can start with one state of a given physical system and basically hit the "fast forward" or "backward" button to see what the state was like in the past and what other state it's going to evolve to in the future. This assignment of future states to past or current states and vice versa is unique and one-to-one, hence deterministic:

past -> future

A --------> X

B --------> Y

where the arrows indicate evolution in time.

This is what allows us to make predictions for the future outcome of experiments or draw conclusions from experimental results in the first place.

Now, the problem with black holes and in particular their evaporation through Hawking radiation is that Hawking radiation does not in any known way depend on what once fell into the black hole but, instead, just on the black hole's total mass. So let's say you start with two different mass distributions A, B of the same mass M and each collapses and forms a black hole BH of mass M. You could argue that the original matter is still somewhere inside the black hole, so the black hole's internal state still depends on the past matter distribution and we should indicate this by talking about black hole BH_A and black hole BH_B. So we have:

A -> BH_A

B -> BH_B

Then Hawking radiation sets in and both black holes vanish eventually and give way to a state of Hawking radition H:

A -> BH_A -> H

B -> BH_B -> H

As mentioned before, the Hawking state H really only depends on the mass M of the black hole, so since both BH_A and BH_B had the same mass, we will also get the same final Hawking state H. As you can see, the mapping {past events -> future events} is no longer one-to-one: From H alone you cannot draw any conclusions about the original state anymore. (Was it A or B?)

This is (one half of) what is meant when people say that information is lost (about the original state).

The other half is that a classical (eternal) black hole state is a so-called pure state from the point of quantum mechanics: There is never any doubt about its precise state. It is always perfectly described by only its mass (and angular momentum and charge)[1]. Hawking radiation, however, is not such a state once the black hole has fully evaporated. Instead, at that point it is a so-called mixed quantum state meaning that it could be any of a whole "mix" of states. We can only give a probability distribution for what the state is in reality; in Hawking's case it's a perfectly thermal distribution. (Side remark: I should point out that such a mixed state is not the same thing as a superposition in quantum mechanics! In particular, the probability distribution here is not related to any wave function.)

Anyway, what this means is that we have now evolved from a black hole state BH, that was precisely known, to another state about which nothing can be said anymore outside of the probability distribution:

BH -> Hawking_1 or Hawking_2 or Hawking_3 or …?

This constitutes a loss of predictability.

TL;DR To sum up, there are two aspects: The loss of information and the loss of predictability. Both are just the two sides of the same medal: The breakdown of determinism.

[1] https://en.wikipedia.org/wiki/No-hair_theorem

Re: Are Black Holes Actually Dark Energy Stars?

#97

Post by codethief »

dsnuh wrote: post #94
codethief wrote: post #91

Earlier quoted context omitted.

I'm afraid I don't have the time to watch the entire video but, being a physicist, I can still try to answer your questions. Currently, however, your question > If time becomes space-like, and space becomes time-like, can we think of black holes as "time stars"? doesn't make much sense to me. Time does not become spacelike nor does space become timelike. In General Relativity, time and space are not individually defi…

I just realized I was replying to the wrong parent comment! So sorry. I was talking about a PBS Space Time episode on YouTube I saw in (or came across via) a different comment. https://youtu.be/KePNhUJ2reI

No worries, I hadn't watched the video yet, anyway. :) So feel free to rephrase your questions if you like!

Re: Are Black Holes Actually Dark Energy Stars?

#98

Post by walru »

Semiapies wrote: post #68
joe-collins wrote: post #17

Earlier quoted context omitted.

At least at the pop-science level, his ideas connect a lot of dots. He'd neatly resolve the weirdness and mystery of black holes, their jets, their information paradox, and dark energy. It feels good. Whether or not any of it makes a lick of sense once you start actually crunching numbers is another question. The lack of interest from other scientists leaves me skeptical (even if I'm silently enamored of the neatness…

Yep. I've been hearing mentions of this guy's theories from pop science publications for years even though, as the article says, "The idea has found no support in the astrophysical community—over the last decade, Chapline’s papers on this topic have garnered only single-digit citations." The pop science press is depressingly bad.

I would much rather live in a world where this person may be heard than likewise.

"Don't take refugee in the false security of consensus."

https://www.youtube.com/watch?v=4Z2uzEM0ugY

Re: Are Black Holes Actually Dark Energy Stars?

#99

Post by opportune »

Trombone12 wrote: post #76
Sarki wrote: post #52

On another note a theory which seems to fit particularly well is called Janus. The concept lies in the existence of a twin universe (ours being matter based the twin being antimatter based) merged together where the black holes are basically where the antimatter is concentrated and thus repulses all the matter hence this seemingly void. This is a succint summary but I hope it makes sense to the more knowledgeable rea…

That makes no sense, black holes are like super much the opposite of a void. Further, repulsion is precisely the opposite of gravity.

Yeah you can interpret a Schwarzchild radius as a “void” in a certain sense (though more like a one-way dump) but a black hole is still very much a participant in the physics of our universe

Re: Are Black Holes Actually Dark Energy Stars?

#100

Post by opportune »

lottin wrote: post #53

"The fabric of space-time" — I hear this a lot, but what does it mean? Does it mean that space and time are a "fabric"? What is such a fabric made of? The idea that space and time are actual objects, instead of intellectual constructs, has always struck me as wrong. (I'm not a physicist.)

Think of the universe, from beginning onward, as a 4-dimensional manifold. Physicists don’t know exactly what the topology of that manifold is, but they do know that mass can affect it
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