Are Black Holes Actually Dark Energy Stars?
nautil.us
nautil.us
And that's what George Chapline is offering the pop sci press.
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.
"Hell, if I could explain it to the average person, it wouldn't have been worth the Nobel prize." -- Richard Feynman
Its a good standard to hold yourself to when explaining things to others. But not one to hold others to when explaining to you.
https://cacm.acm.org/magazines/2011/8/114933-the-robustness-...
My (non-physicist) understanding of this, is that neutrinos from then will be quite low energy now, due to the expansion of the universe(?), and so not detectable by the method IceCube uses. There is a minimum energy required, in part because the charged particles generated by the neutrino interaction need to be moving faster than the speed of light in water (or whatever the detection medium is) for there to be Cherenkov radiation generated and then detected.
That said, I would love to see a response from a more knowledgeable person!
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.
[1]https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.11...
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 myself).
The pop science press is depressingly bad.
"Don't take refugee in the false security of consensus."
They put it pretty bluntly in the article.
To this article's credit, though, it is more measured than others. Just as a whole it seems weird to me how much attention such a seemingly insignificant hypothesis is getting.
There's a moment at which every scientific theory is only thought credulous by a single person.
Agreed, but the same is also true of any conspiracy theory or half-baked idea. The theory should be evaluated on it's merits, not the number of supporters. And theories that can be tested are always better than ones that can't IMO.
As jboggan mentions, this theory is both falsifiable and testable in practice.
I think it's important that there are always a few people in science who go against the mainstream, as long as they do actual science, so falsifiable and testable theories.
Here is one of his recent papers: Emergent Relativity https://arxiv.org/pdf/gr-qc/0302028.pdf
It occurred to me the other day when the dark matter article hit the front page that our equation for gravity works with three dimensions but those dimensions are uniform. I can turn an object with very little effort (literally without doing work) and it’s the same size from our perspective.
How would it work if matter has more dimensions that aren’t proportional, or if space is curved in higher dimensions and the differences are in the noise floor here on earth and in orbit?
:(
Also, go through the older videos. A lot of what's covered today builds on the previously released shows.
then it sounds like normal speech.
I can't reproduce your experiment... I tried turning a piece of paper. At first it looked, say, about as large as a cantaloupe, but when I turned it got smaller and smaller until it practically disappeared, and it becomes very tiny... basically nothing more than a thin line in space. At certain angles I can barely see it at all. What is going on?
But there is a serious problem with this. If you measure the density of a black hole by using it's even horizon you'll find that the mass and event horizon do not scale together. For instance, calculated in this way, a galactic mass black hole has a density of only 200kg/m³.
* Unless you happen to be a photon.
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 Invariance (light travels at the same speed in all reference frames), it is hard to suppose that there is such a thing as "atoms of spacetime" from which it is made. However, because our world is cosmological and the big bang does actually pick out a preferred reference frame, Lorentz Invarience has to be approximate in some way.
Because of cosmology and the breakdown of reductionism at plank scales, it seems that the notion of spacetime itself is approximate and needs to be replaced with something else. Some people are trying to derive spacetime from purely quantum mechanical notions, while other people are trying to find dual systems where spacetime and quantum mechanics emerge hand-in-hand. The two approaches I'm familiar involve either holography or purely geometric and combinatorial ideas where the principles of general relativity and quantum mechanics are outputs rather than assumptions.
https://www.youtube.com/watch?v=WECVq2YBduY&t=0s&index=9&lis...
A particular solution to a set of equations does not usually have all the symmetry of the equations. In fact, I would say that, any solution to GR equations with energy and/or matter (assuming homogeneity on large enough scale) you will find something that looks like a preferred frame of reference.
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 information from all light cones within the observable universe? In other words, would different black holes contain different information?
Does my question make sense?
However, as for black holes containing the same information, our universe is expanding uniformly at an accelerating rate, and this results in cosmological horizons beyond which objects are moving faster than the speed of light (with respect to the frame of reference). Therefore, black holes in different galaxies shouldn't be able to have access to the same light cones without compromising the principle of locality. Although, if you believe that entangled black holes in different galaxies would lead to the same singularity ("ER=EPR" [1][2]), this becomes more complicated and is way out of my depth.
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Nima Arkani Hamed | Unification and Fundamental Phyics: A Status Report 9-21-2018
[0]: https://www.youtube.com/watch?v=pXYvFMqwbhc
Leonard Susskind Public Lecture | "ER = EPR" or "What's Behind the Horizons of Black Holes?"
[1]: part 1: https://www.youtube.com/watch?v=OBPpRqxY8Uw
[2]: part 2: https://www.youtube.com/watch?v=uiG_EtVQu5o
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(ignoring Hawking Radiation)?
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.
> 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.
What they mean when saying that "time and space switch roles inside a black hole" is that in standard Schwarzschild coordinates, the direction given by the time coordinate becomes spacelike at the event horizon and, likewise, the radial coordinate becomes timelike. This statement is specific to Schwarzschild coordinates, though, or, more generally, any coordinate system that is singular/ill-defined at the event horizon. There are coordinate systems, however, that don't exhibit this pathological behavior at the horizon and, there, no switching occurs.
There were similar objections to the existence of the electromagnetic field, back in the 1890s. But it turns out that fields can propagate energy independent of any non-field objects in them... and if it can carry energy, then how can you say they aren't real?
Spacetime carries energy in the form of gravitational waves. So it is as much an object as anything else that carries energy, whether it be in wave form or mass form.
> As the EHT team begins to analyze the 2017 data on Sgr A* and M 87 over the coming months, preliminary images will begin to emerge, and the searches for the signatures of orbiting material around the black holes will be conducted. It is the most exciting time of the project.
[1] https://eventhorizontelescope.org/blog/eht-status-update-may...
I think it's fair to say black holes are a kind of "star", but the concept of dark energy and dark matter are something else.
That's certainly the case for dark matter. After decades of work we still don't know what it is, which has given the word "dark" the additional meaning of 'unknown'.
When it comes to dark energy, I think it mostly implies this second meaning.
This is really exotic space. Time dialation immediately outside of the event horizon would make any matter fall so slow that it would take millions of years of time for an observer to see that material cross the horizon.
Growth-wise, you have to keep in mind that the black hole doesn't grow when matter crosses the horizon, but when the matter gets close enough to the horizon that mass of black hole + mass of new matter creates a blackhole of a larger radius that encompasses that matter.
See especially the section on entropy.
https://en.wikipedia.org/wiki/Maxwell%27s_demon
That is an example of one way in which information can be exchanged for work.
Specifically, the entropy within the box gets converted into information inside the demon's "head", which eventually gets radiated away as entropy outside the box. This way, the box's entropy falls, but the entropy of universe as a whole is raised (or at least maintained).
If information can be destroyed, physics are no longer reversible. Playing things in reverse would give you events that occur for no reason. This is hugely important not just for particle physics, but also thermodynamics.
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.
This is also the principle that led to our theoretical understanding that the maximum amount of information that can be contained in a volume is bounded by the _surface area_ of the volume. This is the Holopgraphic Principle: https://en.wikipedia.org/wiki/Holographic_principle.
There's a great PBS Space Time youtube video on this concept, which explains it far better and more accurately that I ever could: https://www.youtube.com/watch?v=9XkHBmE-N34
If you are travelling with a probe towards the horizon though, you would be able to calculate your escape velocity, so you could tell if you are inside our outside the horizon.
Its kind of awkward if you think about it... its seems like causality has 2 versions after the horizon.
[0]: https://en.wikipedia.org/wiki/Black_hole_information_paradox
This is merely conjectured by some physicists. In reality, we have no clue what happens.
The question necessarily treats space and time as two seprate entities, which generally works fine. Relativity starts to break that question. Different inertial/non-inertial observers will get different answers. Not a huge problem for physics, because we can easily figure out the answer for each observer. But if it was super important to you what event happened first, you won't get a satisfying answer, unless the two events occur inside each other's light cones. Then there's no ambiguity.
So we get to black holes, they seriously break this question, the light cones are completely messed up.
edit: typos
> In short a black hole is how we call the possible existence of a place in the universe where there is no time nor energy
I don't know where you got this idea, but black holes don't have "no time" and they contain lots of energy (often several stars' worth).
Keep in mind that time is relative, so when talking about extreme situations like black holes it's important to keep track of what we're talking relative to. In particular, if an astronaut left a space ship, approached a black hole, passed beyond the event horizon and carried on going, that astronaut wouldn't really notice: if they looked forwards into the black hole they'd just see normal looking space, if they looked backwards they'd see their ship just as if they'd not entered the black hole. Relative to the astronaut, space and time appear completely normal; hence it doesn't make sense to talk about black holes having "no time".
Things would look different relative to the ship: the image of the astronaut they see would redshift as it approached the event horizon, and would also slow down until it came to a stop when at the horizon.
Note that this ignores tidal forces, which can be large around small black holes (the astronaut would certainly notice if their body were torn apart!). For large black holes like Sagittarius A* the tidal forces at the event horizon should be small enough to ignore.
On the other hand, based on my understanding of the Janus model as I said in my first comment, the location of the seemingly void places are actually explained by the concentration of antimatter, which repulses matter through gravity. A possibly wrong summary of what I'm visibly struggling to communicate: This model explains how on the same way matter concentration attracts matter and rejects anti-matter, antimatter concentration attract antimatter and rejects matter.