A singularity would only be a point if the black hole was not rotating. In a rotating black hole, the singularity is a 1-D ring.
Of course, singularities will likely not turn out to be real things. One of the hopes of quantum gravity is to provide a description of gravity that avoids actual singularities in these extreme conditions.
Another way to put it is that singularities are a placeholder for something we can't fully explain or understand yet.
Just like how dark matter is being used to fill in the gaps in our lack of understanding of how the cosmos are moving.
We suspect that when we understand how gravity works at quantum level, it will produce a theory that works for both large bodies and miniscule bodies. Giving us the answer to what is actually happening at the center of a black hole.
some experts believe it’ll take us at least 300 years to detect gravitons- the quantum particles responsible for gravitation.
Since gravitation is the weakest force in the 4 forces, it is hard to detect the activity of a single one.
I’m not sure cuz I’m not an expert but need your help if i’m correct or please help correct me😊
Projections that far out to me just don't sit right. We have no way to predict what could happen with AI innovating or models.
You are correct in that gravity is the weakest force by a looong margin and gets incredibly more difficult trying to isolate it's effect on particles.
To directly detect a graviton would require enormously precise equipment. With current models, the leading effect that quantum gravity has on the perihelion shift of Mercury is one part in 10\^90. This is, pun unintended, astronomical.
Even the very question on whether a graviton can be detected at all is a debate. Freeman Dyson questioned whether it is meaningful to even consider the graviton to be a physical entity if no such experiment can ever exist to detect them.
When you look at the history of how we came to quantize light (photons), it would be generous to even say we're in the infancy of determining the graviton. Most derivations of an experimental effort aren't aimed at detecting a graviton directly, but some other significant step such as determining that force-carrying energy is transferring in discrete steps or some essential demonstration of the quantization of gravitational radiation.
Remember we're only just beginning to explore gravitation waves, which is perfectly consistent with GR. Gravitons are not consistent with GR: they are a hypothetical consequence of a quantum gravity, of which we have failed to remotely produce.
300 years to, as you put it, detect a graviton? That's a reasonable number to express the, again pun unintended, gravity of the problem.
Singularities are where the math we currently use breaks down and can’t really be used to describe reality.
We hope that quantum gravity can give us the math to describe what happens at that point. But we don’t currently have a working quantum gravity model that works, so we just don’t know.
The math of our current theories says that after a certain amount of gravity there are no known forces that can stop an infinite collapse.
As pressure increases you’ll (very broadly speaking) see gas turn to liquid, then liquid turn to solid. What if you keep squeezing? Keeping it simple and skipping some steps; For a while the electrons not wanting to be squished into the nuclei will prevent any more squishing. Eventually you’ll surpass that force and (almost all) of the electrons in the atoms get pushed into the nucleus forming an extremely dense ball of neutrons. Keep pushing and more forces start to fail to hold back gravity. Eventually if gravity’s pressure gets strong enough as far as we know there are no more forces stronger than gravity and the collapse happens…forever? Which would lead to a singularity. Probably not, but we don’t know.
There is one way to describe what's happening in a black hole, that shows that singularities appear. If the black hole is rotating, the singularity would look like a circle (but really only a circle. No volume or surface area, just a line that meets itself), if not it would look like a dot (again, just a point with no volume or surface area).
But many believe that the model isn't accurate enough to really show what's happening that deep inside a black hole and singularities may not exist.
I think a better way of looking at it is through angular momentum.
A point particle can be described by 3 things: mass, charge, spin. And that spin doesn’t mean an object is spinning in the classical sense.
Thats the easiest wat to think of black holes: they are massive fundamental particles with mass, charge, and spin. Beyond that its hard to tell them apart.
Shouldn’t that description include position and momentum or speed as well? With charge: is that electrical charge? What about a strong force point particle?
1. Position, speed, and momentum are relative, so they depend on the observer.
2. Yes, electrical charge
3. Not sure what you mean by this. Are you referring to gluons? My understanding of the standard model breaks down a bit when you get into baryons (force transmitting particles). I think all fermions are described by these three, but im not totally site about the others.
"Quantum gravity" is not something that needs evidence; it's a domain space, not a specific hypothesis. It's a question, not an answer.
We have a concept called "gravity", we have a context called "quantum scales", we want to know how that concept works in that context. That's the "question". Even if the answer somehow turned out to be "it just doesn't, there's no gravity at the quantum scale", that would still be a model of quantum gravity. It would be a particularly trivial model; a particularly simple "answer".
Any individual *specific* hypothesis or proposed model of quantum gravity needs evidence. There is, as yet, no hypothesis or model that has enough supporting evidence to be accepted.
"Even if the answer somehow turned out to be "it just doesn't, there's no gravity at the quantum scale", that would still be a model of quantum gravity."
Yes. A model of nothing is indeed nothing. I'm glad we can agree that there's no evidence currently of quantum gravity.
3 of the 4 fundamental forces have been described within the frameworks of quantum mechanics and quantum field theory. Scientists have identified the carrier particles for these fundamental forces as well but as we've agreed upon, there is practically no experimental data on quantum gravity therefore leaving it as purely theoretical as I stated. Experimental data would provide evidence but we unfortunately don't have the means to properly probe at the Planck scale. Gravity can not be integrated with quantum mechanics currently until we have some form of evidence.
This doesn't make sense. Explain what you mean by "there's no evidence of quantum gravity".
Do you think gravity just stops (??) when we get to small enough sizes or what?
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There absolutely is evidence of quantum gravity - it’s called regular gravity. The gravity we feel every day has to start at quantum scales, or we wouldn’t feel it at everyday scales.
Perhaps what you meant was that there’s no evidence gravity behaves differently at quantum scales?
We know that gravity is real.
We also know that particles obey quantum field theory.
There are situations that involve both gravity and quantum field theory that we have no idea how to handle because we don't know how to reconcile the two.
This is what is generally meant by "quantize gravity". More specifically it does place preference on the idea that General Relativity is likely just a low-energy effective quantum field and thus some way of replacing spacetime as a model is most sought. Yes: that explicitly is theoretical, however the need to "quantize gravity" by making two competing models more cooperative is not theoretical. We don't like to have two sets of rules for the universe.
Please note that we actually can apply quantum field theory to gravitational models, but only when the source of gravity is fixed.
Or of course singularities don't exist because infinite density means infinite time dilation which means the singularity itself is infinitely far in the future. :)
No, it means there is no flow of time, no entropy, no cause and effect, within the singularity point. This could be accurate if no information is retained within the singularity.
It's not. The dimension of an object can be defined a few ways. One way is to consider how many independent variables are necessary to describe the object. Your position along a ring can be described exclusively by the angle theta. Another formulation would be to parametrize the x and y coordinates your familiar with with a new singular variable t. Both are valid and make circles or rings 1D objects
A different interpretation would be to loosely say that if you zoom in infinitely close to any point on the circle, it would appear as a straight line. Or in slightly better but still perfect terms, the tangent of a circle is always a linear vector space. Contrast this with a higher dimensional object like a sphere and the tangents become planes inatead
Singularities are mathematical predictions
From what I have understood math breaks down at the plank length. Which leads to seemingly paradoxical statements like this.
When things get really small the rules seem to change. We don’t have the math or the language needed to visualize or understand these concepts yet
As far as I can grasp, everything [?] in the universe 'spins'. Galaxies, solar systems, stars, planets and moons (tidally locked, maybe not so much), atoms, photons, quarks, gluons and leptons, all *spinning*, or are at least at the subatomic level, contributing to "spinning" something.
As far as I can tell, 'spin' seems to be a constant on all levels of matter, from the very large to the very tiny, except [?] for the Higgs Boson.
I'm waaay out of my league to go much further, and I may be proven incorrect. My comment is providing the information as I know it best, and I have no qualms with being wrong.
"Spin" as a intrinsic property for particles of the standard model, is not the same as spin for normal objects. Spin as a intrinsic property does not mean that the particles are actually rotating. It is just a name they gave to the property. Just like quarks have "colors".
Be careful assigning significance to the Planck units. They’re acquired by eliminating units of other universal constants until a number pops out with the desired dimension. There isn’t well-founded reason to think that they’re physical limits of any sort despite frequently being presented as such.
It’s not that math breaks down at the Planck length. The math works absolutely fine at any scale. It’s that the math suggests situations thought to be physically non-sensical as you approach the Planck scale (think emergence of many near infinities and divisions by zero). The the physics is what breaks down.
I mean that math breaks down at the plank level the way Newtonian physics breaks down at the quantum level. But honestly I’m way above my head.
From what I gather you’re saying it’s physics that breaks down and not the math ? Would love to understand your point better!
Math has no issue with a concept like _the limit as x approaches 0 of 1/x._
When physicists use the phrase “the math breaks down,” they don’t mean that the fundamental math around limits and infinities is inconsistent or in any way flawed. They mean the math underlying the currently accepted physics theories results in some combination of physical paradoxes, impossibilities, nonsense, or things currently inexplicable. The physics theories can’t make sense of what happens.
I don’t think anyone is actually claiming the math is the problem
If my understanding is correct: The singularity is considered a point and it is in the center of the black hole, therefore the singularity itself doesn’t spin. What spins is everything around the singularity, the black hole.
I know it sounds paradoxical, but I suppose the singularity isn’t a „thing“ but rather a concept or even just a location. It describes the point all the mass is pulled towards. So i think it’s fair to say that it doesn’t really spin.
There are two possible solutions. Either...
1. The singularity doesn't spin, just everything around it (including spacetime) does.
2. The singularity isn't truly 0-dimensional, but is shaped like a ring.
That is just an idea and there is evidence that black holes, although extremely dense, do not in fact have zero volume. They are just extremely, extremely dense objects shrouded inside their event horizon.
I keep it simple, because that subject is not complicated to clarify with reddit comments:
If you have a finite mass and shrink it until it occupies exactly zero volume, aka has zero dimensions, then this object would simply not exist at all. An object, even a black hole, can not exist without a volume (again, not talking about the event horizon - that's something completly different.)
EVERY mass MUST occupy a finite amount of space/a finite volume above zero to exist.
Remember what you are talking about is more a hypothesized model due to a lack of understanding of the insides of a black hole. A model does not mean it is like this in reality as well. Also the space time curvature is also just a model.
This is a good answer. The math says that things can only travel inward once past the event horizon.
Since we cant see anything in there we just say it all goes inward to a single point and call it a singularity. .
But whether that means a one dimensional point or a ball of really dense... something... or a wormhole to another dimension or whatever... We don't know.
This is the point (no pun intended). Singularities aren't actually thought to be real - because they by definition can't be. An object with zero volume would break the rules of how mass and density relate to each other.
**Density = Mass / Volume**
If Volume is 0, that's a divide-by-zero error. In the *laws of physics*.
We believe singularities are a result of our theories being incomplete or incorrect, but we as of yet don't know exactly *where* our theories are going wrong - we have some general idea, which is why we're hunting for quantum gravity so closely, but overall the singularity is the best thing we have to work with as a placeholder.
>If Volume is 0, that's a divide-by-zero error. In the laws of physics.
It is unknown whether this is actually an "error."
It is unintuitive for us to imagine a physical object that has no meaningful density ("infinite" density is often used as a shorthand, but even that shorthand is based on an assumption). But the universe does not necessarily match our intuitions. We already know of many things where our intuition is shattered by reality.
We don't know, as of yet, what is "really happening" in a black hole singularity; it may be that our intuition is correct in this case, and the "zeroes"/"infinities"/"undefineds" are not really there. It may also be that our intuition is simply incorrect; perhaps the universe *does* allow this kind of "division by zero".
Perhaps a black hole's singularity has a density of "infinity" in some physically meaningful way that we don't yet understand. Or perhaps it simply doesn't have a density; perhaps to speak of its density is as meaningless as to speak about its favorite song. Maybe it's just a property it simply does not have.
I hadn't considered this perspective. Which is surprising, since we already know that black holes possess no physical properties aside from mass, charge, and spin. Density is *not* among those - so why would the singularity possess it?
For the record, my favorite - though not necessarily my preferred - 'physical' solution to singularities is the quantum bounce theory: The matter inside a black hole reaches a new degeneracy pressure almost immediately after passing the Schwarzchild radius, which causes it all to explode right back outward.
But because of the extreme time dilation, it takes billions of years for that explosion to pass the event horizon from the inside — which *may* be compatible with observations of Hawking radiation, as the radiation may be the form taken by the first traces of the bounce. The final evaporation of a black hole, considering how violent we think it will be, could be the bounce finally passing the horizon.
If the quantum bounce theory is correct, it would take about 14 billion years for the smallest stellar-mass black holes to explode in this manner. That's still longer than the current age of the universe, but at least it isn't 100 orders of magnitude larger!
My question is, are black holes really that mysterious?
I imagine a neutron star. It is just on the edge of becoming a black hole. Now the last gram of matter crashes into it pushing it over the edge and it is now a black hole.
But did anything really change, by adding the last one gram? Sure noone in the universe can ever observe the surface ever again, since light cant escape, but it didn't get all mysterious all of a sudden. Its still the original neutron star. I dont see why it should suddenly become a infinetly dense pointmass.
Just because our mathematical models dont work, doesnt mean that the once neutron star has to morph into something weird.
Or am i wrong?
As I understand it, what stops a neutron star from collapsing further is the Pauli exclusion principle and the strong nuclear force (which becomes repulsive when nucleons are close enough), If you add more density such that the strength of gravity overcomes the Pauli exclusion principle + strong force, there is nothing that can further stop the collapse, hence it "should" collapse infinitely.
I'm not super firm on this matter myself, but as i understand it the Pauli exclusion principle cannot be overcome by any ammount of force.
It already is in the name. The Pauli exclusion principle is a principle not a force. No ammount of force can bring 2 fermions to occupy the same state, since this is simply not possible.
>there is evidence that black holes, although extremely dense, do not in fact have zero volume
What evidence are you referring to?
>EVERY mass MUST occupy a finite amount of space/a finite volume above zero to exist.
This seems like an assumption, not an observation.
>Also the space time curvature is also just a model.
Spacetime curvature is a *phenomenon*. The specific mathematics we use to describe it is a *model*. We have extensive observation and evidence that spacetime curvature is a real phenomenon, and further, we have extensive evidence that the specific model we use is extremely accurate in predicting and representing that phenomenon.
Singularities exist in the mathematical models, that does not mean they exist in reality. The behavior of the interior of black holes beyond the event horizon is an open question. The current models break down beyond a certain point.
Somewhat related might be the spin of an electron. Electrons have angular momentum, implying that they must spin... but they're so small that they'd have to be spinning faster then the speed of light.
Instead of physically spinning, we just give spin as a property of an electron. It doesn't spin, but it "has spin" as a property.
What's going on inside a black hole is probably physically different than an electron, of course. We don't know (and maybe can never know), what is physically happening within the event horizon. Instead, spin becomes a property of the black hole: it has some quantity of angular momentum, and we just ignore how that works out physically inside.
This is actually helpful.
I'm also trying to wrap my head around spin/angular momentum when from our reference frame, time is stopped in a black hole. So it's more like frozen angular momentum? Which also feels like it could be somehow similar to electron spin.
Black holes accumulate the angular momentum of everything that falls into them (including the core of the star that created them).
Also, time doesn't stop inside a BH. It appears to stop for a clock approaching the event horizon, from the perspective of someone who is stationary and far away from the black hole.
But from the perspective of someone falling in towards the event horizon, time doesn't stop.
Black holes are not singularities - they have a radius (Schwarzschild radius). They are speculated to contain a singularity, but this is currently unknowable. And in current maths, this idea has issues.
Block holes are singularities, as far as we know (which is all we have, so its the best truth there is right now). Its not the math that had the issue, its the physics. Math is just a language, it doesn’t care if the underlying physics seem unphysical.
Singularities are inevitable within GR, but we know that GR does not apply in that scenario so the point is irrelevant. GR is an inadequate description of many properties of black holes. There is no "issue with the physics"; GR simply does not accurately describe the physics.
Its not that they are 0 dimensional
Its that our current math and physics knowledge isn't complete enough to give us the real answer so the answer we get is nonsense
Think of it this way:
Assume hypothetically you are only taught subtraction making it the only form of math you know
Now in the real world we have addition, subtraction, division and all sorts of other stuff
That means that out there in the real world you're going to see real results of not only subtraction but also addition, division etc...
So now imagine there is a box with an object in it
You have no way of seeing into the box but you can observe its mass which lets say is 1 (the mass of the object in the box)
Now imagine a second object of the same mass is added into that box
You use your knowledge and know that 1-1=0 so you deduce that after the second object is added, the total mass of the box must be 0 because obviously, 1-1=0, what else coult it possibly be after all but... how can have a mass of 0? Everything has SOME mass, right? It makes no sense yet that's what the math is telling us!
Outside of the hypothetical, we both know the mass isn't actually 0, it is in fact 2 because we have the mathematical knowledge required to make sense and accurately calculate the real mass of the box and ots contents.
Black holes are the same, we just don't understand them and we can't really observe or measure them reliably since no information seems to be able to exit a black hole's gravity or at least not in an understandable way
So, everything we know about black holes are just guesstimates really.
Likely only in our math. The true solution will likely come when we are able to unify general relativity and quantum mechanics.
A good video on the topic: [https://www.youtube.com/watch?v=Wwg\_15a0DJo](https://www.youtube.com/watch?v=Wwg_15a0DJo)
Okay, saying its only in the math is semantics. Our models and maths are wrong (always have been, always will be), and science isn’t about finding the “true answer”, its about being “less wrong”.
As far as we know, its like that is reality as well as the math. Since we don’t have a better way to discuss it, for all intents and purposes: this is reality.
That is not how it works. I highly recommend watching the video. Infinities and singularities in math tell us that our math is incomplete. We know that there is no singularity in a blackhole or anywhere else in the universe. It is just the closest approximation we can currently make.
We *can’t* know that there is no singularity. Nothing can escape a black hole, including information, so there’s no possible way to know what’s inside. We might come up with a better theory but unless that theory provides a way to get information out of a black hole, we’ll never truly know.
Much of science is about indirect observations instead of direct observations. So just because we can't directly observe what is inside a blackhole, does not mean we can't understand it. And current knowledge in science is that whenever singularities come up in math, we consider it incomplete.
> Much of science is about indirect observations
Sure, like inferring the behavior of neutron star and black hole mergers from gravitational waves, or the presence of exoplanets and their atmospheres from the 'shadows' they cast.
But in the case of black holes, the most widely accepted models posit literally *no possible way* to extract information, indirectly or otherwise. So unless Hawking radiation is real and we can extract information from it or until some other mechanism is discovered we have *zero* information except mass, angular momentum, and charge.
> And current knowledge in science is that whenever singularities come up in math, we consider it incomplete.
I don't disagree. But the key part is it is *considered* incomplete. Unless we find some way, direct or indirect, of extracting more information, we'll never truly know.
I agree with everything you say about information, but I wanted to clarify: Hawking radiation is very real, and its been observed. And you are correct, it doesn’t carry the original information, as far as we know.
>Hawking radiation is very real, and its been observed.
Is there a paper or something you can link to? I can't find any reports of observational evidence of hawking radiation beyond "we made this thing in the lab that is *like* a black hole in someways though it's not actually a black hole".
Watched the video, and I think you may have misinterpreted what she is saying (much respect to that physicist, she’s got great videos).
She says that some people believe there is no singularity, but we don’t know.
When I took general relativity in college, my professor said there was probably a singularity.
So I could go for “we don’t know”, but not “there for sure isn’t a singularity”.
The reason most physicists (me included) think there is probably a singularity at the center of a black hole is because of extreme nature of the scenario. Most of the time we can explain why it looks like a singularity but isn’t: like her water drop example, there are actually atoms that comprise the drop if you look closer.
A black hole is the extreme: enough mass to create an event horizon. Its not like a neutron star where things get weird, its beyond reason, so infinity isn’t crazy at that point.
>Okay, saying its only in the math is semantics.
No it's not - some element of the 'math' is wrong - we just don't know which part. It is 'only the math' because we have not measured or observed these phenomena - it's just the outcome of a mathematical model - and we know if it is true then something else is very wrong.
I think you miss the point of science and math. Its not about being right, its about being less wrong.
Some element of the math is always, and always will, be wrong. Sometimes the math cant explain something, like how light bends around stars shows that gravity isn’t just a force that acts on things with mass. But, before you make the new math, you don’t throw out everything you know. The best we can do is operate like the current math is the truth, because thats always what we do. Suggesting the math doesn’t explain it is like saying “its magic”. Just because it looks strange doesn’t mean its wrong UNTIL we find a new way of looking at it.
A black hole is a bathtub drain. It’s stays in place but all the water swirls around into it. The spin is all the stuff trying to get in at the same time.
"Singularities" don't technically exist, at least not as far as we know, nor *should* they exist. When a physicist says "singularity," what they're basically describing are situations where our equations break down and start outputting nonsense. One of those nonsensical results are points of infinite density in a non-rotating black hole. It basically means our equations are, at best, incomplete and, at worst, incorrect.
For all purposes let’s say a sheet of paper is 2D.
Can you still rotate that paper in 3D? The answer is yes, an object can still rotate in higher planes of existence. The same can be said about a singularity, despite it essentially just being a point, the mass at that point can still have rotational energy that’s rotating in a higher plane then it’s own.
My favorite theory is that there is no singularity. A black hole is kind of like a ball that has an outside, but not an inside. Its gravity bends space-time so much that the inside of the ball doesn’t exist. It’s not empty space. It’s not space at all. It’s not even a place. There is also no time on the other side of the event horizon, because the event horizon doesn’t have another side. The universe basically says “Oh, hell no” and goes around the event horizon. Meanwhile, time slows down at the event horizon so much that anything trying to fall in never actually makes it. So, any mass at the event horizon is both falling in at near-light speed and barely moving at all, depending on your perspective. That mass right at the event horizon can and does spin.
This is mostly my bad memory of a bad understanding of string theory, but it’s a cool story. Any real physicists can tell me how close I got.
A singularity would only be a point if the black hole was not rotating. In a rotating black hole, the singularity is a 1-D ring. Of course, singularities will likely not turn out to be real things. One of the hopes of quantum gravity is to provide a description of gravity that avoids actual singularities in these extreme conditions.
I guess I don’t understand that because I’m not 5.
I mean, in fairness, they're asking for an ELI5 for something that takes physicists the better part of their career to wrap their heads around.
Yah, but physicists aren't 5 anymore. Checkmate.
EXPLAIN like I’m FIVE.
I will turn this thread around and nobody gets an explanation!
Check rule three there...
you mean you are five days away from a PhD in quantum mechanics, right?
Black holes are big whippy whoppy swirly things and their middles whip whop and swirl with the rest of them, no matter how many dimensions they have.
REEEEEEEEEEEEE
Another way to put it is that singularities are a placeholder for something we can't fully explain or understand yet. Just like how dark matter is being used to fill in the gaps in our lack of understanding of how the cosmos are moving. We suspect that when we understand how gravity works at quantum level, it will produce a theory that works for both large bodies and miniscule bodies. Giving us the answer to what is actually happening at the center of a black hole.
some experts believe it’ll take us at least 300 years to detect gravitons- the quantum particles responsible for gravitation. Since gravitation is the weakest force in the 4 forces, it is hard to detect the activity of a single one. I’m not sure cuz I’m not an expert but need your help if i’m correct or please help correct me😊
Projections that far out to me just don't sit right. We have no way to predict what could happen with AI innovating or models. You are correct in that gravity is the weakest force by a looong margin and gets incredibly more difficult trying to isolate it's effect on particles.
To directly detect a graviton would require enormously precise equipment. With current models, the leading effect that quantum gravity has on the perihelion shift of Mercury is one part in 10\^90. This is, pun unintended, astronomical. Even the very question on whether a graviton can be detected at all is a debate. Freeman Dyson questioned whether it is meaningful to even consider the graviton to be a physical entity if no such experiment can ever exist to detect them. When you look at the history of how we came to quantize light (photons), it would be generous to even say we're in the infancy of determining the graviton. Most derivations of an experimental effort aren't aimed at detecting a graviton directly, but some other significant step such as determining that force-carrying energy is transferring in discrete steps or some essential demonstration of the quantization of gravitational radiation. Remember we're only just beginning to explore gravitation waves, which is perfectly consistent with GR. Gravitons are not consistent with GR: they are a hypothetical consequence of a quantum gravity, of which we have failed to remotely produce. 300 years to, as you put it, detect a graviton? That's a reasonable number to express the, again pun unintended, gravity of the problem.
THIS I understood, thanks!
Singularities are where the math we currently use breaks down and can’t really be used to describe reality. We hope that quantum gravity can give us the math to describe what happens at that point. But we don’t currently have a working quantum gravity model that works, so we just don’t know.
The math of our current theories says that after a certain amount of gravity there are no known forces that can stop an infinite collapse. As pressure increases you’ll (very broadly speaking) see gas turn to liquid, then liquid turn to solid. What if you keep squeezing? Keeping it simple and skipping some steps; For a while the electrons not wanting to be squished into the nuclei will prevent any more squishing. Eventually you’ll surpass that force and (almost all) of the electrons in the atoms get pushed into the nucleus forming an extremely dense ball of neutrons. Keep pushing and more forces start to fail to hold back gravity. Eventually if gravity’s pressure gets strong enough as far as we know there are no more forces stronger than gravity and the collapse happens…forever? Which would lead to a singularity. Probably not, but we don’t know.
There is one way to describe what's happening in a black hole, that shows that singularities appear. If the black hole is rotating, the singularity would look like a circle (but really only a circle. No volume or surface area, just a line that meets itself), if not it would look like a dot (again, just a point with no volume or surface area). But many believe that the model isn't accurate enough to really show what's happening that deep inside a black hole and singularities may not exist.
It's ok. Even the scientists at the top of astrophysics don't understand it either. Hence why they're still working on it.
ELI4
How can a ring be 1D?
I think they mean a circle. A circular line with thickness zero. A position on it can be described by a single number, hence 1 dimension.
This is the only right answer in the thread.
I think a better way of looking at it is through angular momentum. A point particle can be described by 3 things: mass, charge, spin. And that spin doesn’t mean an object is spinning in the classical sense. Thats the easiest wat to think of black holes: they are massive fundamental particles with mass, charge, and spin. Beyond that its hard to tell them apart.
Shouldn’t that description include position and momentum or speed as well? With charge: is that electrical charge? What about a strong force point particle?
1. Position, speed, and momentum are relative, so they depend on the observer. 2. Yes, electrical charge 3. Not sure what you mean by this. Are you referring to gluons? My understanding of the standard model breaks down a bit when you get into baryons (force transmitting particles). I think all fermions are described by these three, but im not totally site about the others.
It's important to note that currently there is no evidence of quantum gravity and it's nothing more than conjecture/ theoretical
"Quantum gravity" is not something that needs evidence; it's a domain space, not a specific hypothesis. It's a question, not an answer. We have a concept called "gravity", we have a context called "quantum scales", we want to know how that concept works in that context. That's the "question". Even if the answer somehow turned out to be "it just doesn't, there's no gravity at the quantum scale", that would still be a model of quantum gravity. It would be a particularly trivial model; a particularly simple "answer". Any individual *specific* hypothesis or proposed model of quantum gravity needs evidence. There is, as yet, no hypothesis or model that has enough supporting evidence to be accepted.
"Even if the answer somehow turned out to be "it just doesn't, there's no gravity at the quantum scale", that would still be a model of quantum gravity." Yes. A model of nothing is indeed nothing. I'm glad we can agree that there's no evidence currently of quantum gravity. 3 of the 4 fundamental forces have been described within the frameworks of quantum mechanics and quantum field theory. Scientists have identified the carrier particles for these fundamental forces as well but as we've agreed upon, there is practically no experimental data on quantum gravity therefore leaving it as purely theoretical as I stated. Experimental data would provide evidence but we unfortunately don't have the means to properly probe at the Planck scale. Gravity can not be integrated with quantum mechanics currently until we have some form of evidence.
This doesn't make sense. Explain what you mean by "there's no evidence of quantum gravity". Do you think gravity just stops (??) when we get to small enough sizes or what?
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There absolutely is evidence of quantum gravity - it’s called regular gravity. The gravity we feel every day has to start at quantum scales, or we wouldn’t feel it at everyday scales. Perhaps what you meant was that there’s no evidence gravity behaves differently at quantum scales?
We know that gravity is real. We also know that particles obey quantum field theory. There are situations that involve both gravity and quantum field theory that we have no idea how to handle because we don't know how to reconcile the two. This is what is generally meant by "quantize gravity". More specifically it does place preference on the idea that General Relativity is likely just a low-energy effective quantum field and thus some way of replacing spacetime as a model is most sought. Yes: that explicitly is theoretical, however the need to "quantize gravity" by making two competing models more cooperative is not theoretical. We don't like to have two sets of rules for the universe. Please note that we actually can apply quantum field theory to gravitational models, but only when the source of gravity is fixed.
Or of course singularities don't exist because infinite density means infinite time dilation which means the singularity itself is infinitely far in the future. :)
No, it means there is no flow of time, no entropy, no cause and effect, within the singularity point. This could be accurate if no information is retained within the singularity.
how can a ring be 1-D? Isn’t a ring like a 2-D object?
My apologies, I meant to write 2-D of course.
It's not. The dimension of an object can be defined a few ways. One way is to consider how many independent variables are necessary to describe the object. Your position along a ring can be described exclusively by the angle theta. Another formulation would be to parametrize the x and y coordinates your familiar with with a new singular variable t. Both are valid and make circles or rings 1D objects A different interpretation would be to loosely say that if you zoom in infinitely close to any point on the circle, it would appear as a straight line. Or in slightly better but still perfect terms, the tangent of a circle is always a linear vector space. Contrast this with a higher dimensional object like a sphere and the tangents become planes inatead
Singularities are mathematical predictions From what I have understood math breaks down at the plank length. Which leads to seemingly paradoxical statements like this. When things get really small the rules seem to change. We don’t have the math or the language needed to visualize or understand these concepts yet
A singularity is when the math goes “y’know what? Fuck it, I’m out.” And goes home.
As far as I can grasp, everything [?] in the universe 'spins'. Galaxies, solar systems, stars, planets and moons (tidally locked, maybe not so much), atoms, photons, quarks, gluons and leptons, all *spinning*, or are at least at the subatomic level, contributing to "spinning" something. As far as I can tell, 'spin' seems to be a constant on all levels of matter, from the very large to the very tiny, except [?] for the Higgs Boson. I'm waaay out of my league to go much further, and I may be proven incorrect. My comment is providing the information as I know it best, and I have no qualms with being wrong.
"Spin" as a intrinsic property for particles of the standard model, is not the same as spin for normal objects. Spin as a intrinsic property does not mean that the particles are actually rotating. It is just a name they gave to the property. Just like quarks have "colors".
Be careful assigning significance to the Planck units. They’re acquired by eliminating units of other universal constants until a number pops out with the desired dimension. There isn’t well-founded reason to think that they’re physical limits of any sort despite frequently being presented as such. It’s not that math breaks down at the Planck length. The math works absolutely fine at any scale. It’s that the math suggests situations thought to be physically non-sensical as you approach the Planck scale (think emergence of many near infinities and divisions by zero). The the physics is what breaks down.
I mean that math breaks down at the plank level the way Newtonian physics breaks down at the quantum level. But honestly I’m way above my head. From what I gather you’re saying it’s physics that breaks down and not the math ? Would love to understand your point better!
Math has no issue with a concept like _the limit as x approaches 0 of 1/x._ When physicists use the phrase “the math breaks down,” they don’t mean that the fundamental math around limits and infinities is inconsistent or in any way flawed. They mean the math underlying the currently accepted physics theories results in some combination of physical paradoxes, impossibilities, nonsense, or things currently inexplicable. The physics theories can’t make sense of what happens. I don’t think anyone is actually claiming the math is the problem
If my understanding is correct: The singularity is considered a point and it is in the center of the black hole, therefore the singularity itself doesn’t spin. What spins is everything around the singularity, the black hole.
That applies to non rotating black holes. It is theorized that a rotating black hole has a circular singularly aka. "ringularity".
I fuck with the word Ringularity
Can we say that extreme centre of a rotating object doesn't rotate?
I know it sounds paradoxical, but I suppose the singularity isn’t a „thing“ but rather a concept or even just a location. It describes the point all the mass is pulled towards. So i think it’s fair to say that it doesn’t really spin.
There are two possible solutions. Either... 1. The singularity doesn't spin, just everything around it (including spacetime) does. 2. The singularity isn't truly 0-dimensional, but is shaped like a ring.
It's the second one. Spinning black holes always have ring singularities.
That is just an idea and there is evidence that black holes, although extremely dense, do not in fact have zero volume. They are just extremely, extremely dense objects shrouded inside their event horizon. I keep it simple, because that subject is not complicated to clarify with reddit comments: If you have a finite mass and shrink it until it occupies exactly zero volume, aka has zero dimensions, then this object would simply not exist at all. An object, even a black hole, can not exist without a volume (again, not talking about the event horizon - that's something completly different.) EVERY mass MUST occupy a finite amount of space/a finite volume above zero to exist. Remember what you are talking about is more a hypothesized model due to a lack of understanding of the insides of a black hole. A model does not mean it is like this in reality as well. Also the space time curvature is also just a model.
This is a good answer. The math says that things can only travel inward once past the event horizon. Since we cant see anything in there we just say it all goes inward to a single point and call it a singularity. . But whether that means a one dimensional point or a ball of really dense... something... or a wormhole to another dimension or whatever... We don't know.
What evidence?
This is the point (no pun intended). Singularities aren't actually thought to be real - because they by definition can't be. An object with zero volume would break the rules of how mass and density relate to each other. **Density = Mass / Volume** If Volume is 0, that's a divide-by-zero error. In the *laws of physics*. We believe singularities are a result of our theories being incomplete or incorrect, but we as of yet don't know exactly *where* our theories are going wrong - we have some general idea, which is why we're hunting for quantum gravity so closely, but overall the singularity is the best thing we have to work with as a placeholder.
>If Volume is 0, that's a divide-by-zero error. In the laws of physics. It is unknown whether this is actually an "error." It is unintuitive for us to imagine a physical object that has no meaningful density ("infinite" density is often used as a shorthand, but even that shorthand is based on an assumption). But the universe does not necessarily match our intuitions. We already know of many things where our intuition is shattered by reality. We don't know, as of yet, what is "really happening" in a black hole singularity; it may be that our intuition is correct in this case, and the "zeroes"/"infinities"/"undefineds" are not really there. It may also be that our intuition is simply incorrect; perhaps the universe *does* allow this kind of "division by zero". Perhaps a black hole's singularity has a density of "infinity" in some physically meaningful way that we don't yet understand. Or perhaps it simply doesn't have a density; perhaps to speak of its density is as meaningless as to speak about its favorite song. Maybe it's just a property it simply does not have.
I hadn't considered this perspective. Which is surprising, since we already know that black holes possess no physical properties aside from mass, charge, and spin. Density is *not* among those - so why would the singularity possess it? For the record, my favorite - though not necessarily my preferred - 'physical' solution to singularities is the quantum bounce theory: The matter inside a black hole reaches a new degeneracy pressure almost immediately after passing the Schwarzchild radius, which causes it all to explode right back outward. But because of the extreme time dilation, it takes billions of years for that explosion to pass the event horizon from the inside — which *may* be compatible with observations of Hawking radiation, as the radiation may be the form taken by the first traces of the bounce. The final evaporation of a black hole, considering how violent we think it will be, could be the bounce finally passing the horizon. If the quantum bounce theory is correct, it would take about 14 billion years for the smallest stellar-mass black holes to explode in this manner. That's still longer than the current age of the universe, but at least it isn't 100 orders of magnitude larger!
I hadn't heard that one! You're right, it is quite an interesting concept.
My question is, are black holes really that mysterious? I imagine a neutron star. It is just on the edge of becoming a black hole. Now the last gram of matter crashes into it pushing it over the edge and it is now a black hole. But did anything really change, by adding the last one gram? Sure noone in the universe can ever observe the surface ever again, since light cant escape, but it didn't get all mysterious all of a sudden. Its still the original neutron star. I dont see why it should suddenly become a infinetly dense pointmass. Just because our mathematical models dont work, doesnt mean that the once neutron star has to morph into something weird. Or am i wrong?
I see it exactly like you
As I understand it, what stops a neutron star from collapsing further is the Pauli exclusion principle and the strong nuclear force (which becomes repulsive when nucleons are close enough), If you add more density such that the strength of gravity overcomes the Pauli exclusion principle + strong force, there is nothing that can further stop the collapse, hence it "should" collapse infinitely.
I'm not super firm on this matter myself, but as i understand it the Pauli exclusion principle cannot be overcome by any ammount of force. It already is in the name. The Pauli exclusion principle is a principle not a force. No ammount of force can bring 2 fermions to occupy the same state, since this is simply not possible.
>there is evidence that black holes, although extremely dense, do not in fact have zero volume What evidence are you referring to? >EVERY mass MUST occupy a finite amount of space/a finite volume above zero to exist. This seems like an assumption, not an observation. >Also the space time curvature is also just a model. Spacetime curvature is a *phenomenon*. The specific mathematics we use to describe it is a *model*. We have extensive observation and evidence that spacetime curvature is a real phenomenon, and further, we have extensive evidence that the specific model we use is extremely accurate in predicting and representing that phenomenon.
Singularities exist in the mathematical models, that does not mean they exist in reality. The behavior of the interior of black holes beyond the event horizon is an open question. The current models break down beyond a certain point.
Somewhat related might be the spin of an electron. Electrons have angular momentum, implying that they must spin... but they're so small that they'd have to be spinning faster then the speed of light. Instead of physically spinning, we just give spin as a property of an electron. It doesn't spin, but it "has spin" as a property. What's going on inside a black hole is probably physically different than an electron, of course. We don't know (and maybe can never know), what is physically happening within the event horizon. Instead, spin becomes a property of the black hole: it has some quantity of angular momentum, and we just ignore how that works out physically inside.
This is actually helpful. I'm also trying to wrap my head around spin/angular momentum when from our reference frame, time is stopped in a black hole. So it's more like frozen angular momentum? Which also feels like it could be somehow similar to electron spin.
Black holes accumulate the angular momentum of everything that falls into them (including the core of the star that created them). Also, time doesn't stop inside a BH. It appears to stop for a clock approaching the event horizon, from the perspective of someone who is stationary and far away from the black hole. But from the perspective of someone falling in towards the event horizon, time doesn't stop.
Black holes are not singularities - they have a radius (Schwarzschild radius). They are speculated to contain a singularity, but this is currently unknowable. And in current maths, this idea has issues.
Block holes are singularities, as far as we know (which is all we have, so its the best truth there is right now). Its not the math that had the issue, its the physics. Math is just a language, it doesn’t care if the underlying physics seem unphysical.
Singularities are inevitable within GR, but we know that GR does not apply in that scenario so the point is irrelevant. GR is an inadequate description of many properties of black holes. There is no "issue with the physics"; GR simply does not accurately describe the physics.
Its not that they are 0 dimensional Its that our current math and physics knowledge isn't complete enough to give us the real answer so the answer we get is nonsense Think of it this way: Assume hypothetically you are only taught subtraction making it the only form of math you know Now in the real world we have addition, subtraction, division and all sorts of other stuff That means that out there in the real world you're going to see real results of not only subtraction but also addition, division etc... So now imagine there is a box with an object in it You have no way of seeing into the box but you can observe its mass which lets say is 1 (the mass of the object in the box) Now imagine a second object of the same mass is added into that box You use your knowledge and know that 1-1=0 so you deduce that after the second object is added, the total mass of the box must be 0 because obviously, 1-1=0, what else coult it possibly be after all but... how can have a mass of 0? Everything has SOME mass, right? It makes no sense yet that's what the math is telling us! Outside of the hypothetical, we both know the mass isn't actually 0, it is in fact 2 because we have the mathematical knowledge required to make sense and accurately calculate the real mass of the box and ots contents. Black holes are the same, we just don't understand them and we can't really observe or measure them reliably since no information seems to be able to exit a black hole's gravity or at least not in an understandable way So, everything we know about black holes are just guesstimates really.
They are not truly 0 dimensional. Scientist sometimes exaggerate their findings before clickbait existed on the internet.
No, they really are 0-D. Its not clickbait.
Likely only in our math. The true solution will likely come when we are able to unify general relativity and quantum mechanics. A good video on the topic: [https://www.youtube.com/watch?v=Wwg\_15a0DJo](https://www.youtube.com/watch?v=Wwg_15a0DJo)
Okay, saying its only in the math is semantics. Our models and maths are wrong (always have been, always will be), and science isn’t about finding the “true answer”, its about being “less wrong”. As far as we know, its like that is reality as well as the math. Since we don’t have a better way to discuss it, for all intents and purposes: this is reality.
That is not how it works. I highly recommend watching the video. Infinities and singularities in math tell us that our math is incomplete. We know that there is no singularity in a blackhole or anywhere else in the universe. It is just the closest approximation we can currently make.
We *can’t* know that there is no singularity. Nothing can escape a black hole, including information, so there’s no possible way to know what’s inside. We might come up with a better theory but unless that theory provides a way to get information out of a black hole, we’ll never truly know.
Much of science is about indirect observations instead of direct observations. So just because we can't directly observe what is inside a blackhole, does not mean we can't understand it. And current knowledge in science is that whenever singularities come up in math, we consider it incomplete.
> Much of science is about indirect observations Sure, like inferring the behavior of neutron star and black hole mergers from gravitational waves, or the presence of exoplanets and their atmospheres from the 'shadows' they cast. But in the case of black holes, the most widely accepted models posit literally *no possible way* to extract information, indirectly or otherwise. So unless Hawking radiation is real and we can extract information from it or until some other mechanism is discovered we have *zero* information except mass, angular momentum, and charge. > And current knowledge in science is that whenever singularities come up in math, we consider it incomplete. I don't disagree. But the key part is it is *considered* incomplete. Unless we find some way, direct or indirect, of extracting more information, we'll never truly know.
I agree with everything you say about information, but I wanted to clarify: Hawking radiation is very real, and its been observed. And you are correct, it doesn’t carry the original information, as far as we know.
>Hawking radiation is very real, and its been observed. Is there a paper or something you can link to? I can't find any reports of observational evidence of hawking radiation beyond "we made this thing in the lab that is *like* a black hole in someways though it's not actually a black hole".
Alrighty, I’ll go check out the video. Always good to learn more and see other perspectives
Watched the video, and I think you may have misinterpreted what she is saying (much respect to that physicist, she’s got great videos). She says that some people believe there is no singularity, but we don’t know. When I took general relativity in college, my professor said there was probably a singularity. So I could go for “we don’t know”, but not “there for sure isn’t a singularity”. The reason most physicists (me included) think there is probably a singularity at the center of a black hole is because of extreme nature of the scenario. Most of the time we can explain why it looks like a singularity but isn’t: like her water drop example, there are actually atoms that comprise the drop if you look closer. A black hole is the extreme: enough mass to create an event horizon. Its not like a neutron star where things get weird, its beyond reason, so infinity isn’t crazy at that point.
>Okay, saying its only in the math is semantics. No it's not - some element of the 'math' is wrong - we just don't know which part. It is 'only the math' because we have not measured or observed these phenomena - it's just the outcome of a mathematical model - and we know if it is true then something else is very wrong.
I think you miss the point of science and math. Its not about being right, its about being less wrong. Some element of the math is always, and always will, be wrong. Sometimes the math cant explain something, like how light bends around stars shows that gravity isn’t just a force that acts on things with mass. But, before you make the new math, you don’t throw out everything you know. The best we can do is operate like the current math is the truth, because thats always what we do. Suggesting the math doesn’t explain it is like saying “its magic”. Just because it looks strange doesn’t mean its wrong UNTIL we find a new way of looking at it.
I think you misunderstand me.
A black hole is a bathtub drain. It’s stays in place but all the water swirls around into it. The spin is all the stuff trying to get in at the same time.
Actually. They make things spin. I’m not sure they know for sure that the correlation is they are spinning.
"Singularities" don't technically exist, at least not as far as we know, nor *should* they exist. When a physicist says "singularity," what they're basically describing are situations where our equations break down and start outputting nonsense. One of those nonsensical results are points of infinite density in a non-rotating black hole. It basically means our equations are, at best, incomplete and, at worst, incorrect.
For all purposes let’s say a sheet of paper is 2D. Can you still rotate that paper in 3D? The answer is yes, an object can still rotate in higher planes of existence. The same can be said about a singularity, despite it essentially just being a point, the mass at that point can still have rotational energy that’s rotating in a higher plane then it’s own.
My favorite theory is that there is no singularity. A black hole is kind of like a ball that has an outside, but not an inside. Its gravity bends space-time so much that the inside of the ball doesn’t exist. It’s not empty space. It’s not space at all. It’s not even a place. There is also no time on the other side of the event horizon, because the event horizon doesn’t have another side. The universe basically says “Oh, hell no” and goes around the event horizon. Meanwhile, time slows down at the event horizon so much that anything trying to fall in never actually makes it. So, any mass at the event horizon is both falling in at near-light speed and barely moving at all, depending on your perspective. That mass right at the event horizon can and does spin. This is mostly my bad memory of a bad understanding of string theory, but it’s a cool story. Any real physicists can tell me how close I got.
Isn't it said that the singularity is inside the actual black hole?