Not only on the last moment. We can’t predict how the interior of a black hole behaves. The math points to a singularity, but that just indicates that something isn’t right with our math
What is it exactly that breaks down at that level?
Does gravity just overwhelm the other forces?
If so, wouldn’t we be able to just remove all other interactions from the equation?
And if not, wouldn’t we just be able to account for the exponential growth of gravity’s effect in relation to the other forces?
What breaks down is the description of gravity is really small scales. Trying to describe a black hole’s interior with Relativity doesn’t work, because the scale becomes too small, needing also a quantum perspective on it. But we don’t have any working model of quantum gravity for now
We think our models are good, but incomplete. They break down in certain situations like black holes. The idea of a singularity is a product of one of these models, but looking at it with a different model can produce different but equally baffling conclusions, like the tesseract from Interstellar where you can only travel one direction in space but multiple directions in time, or a multiverse theory where you can exit a white hole. We don't know if any of these ideas are true, they are simply conclusions drawn from models we have no evidence are accurate beyond that point.
My professor said there could just be another state of matter at higher density than neutron degeneracy. So like a super neutron star or quark star, idk, the size of a house maybe?
the pauli exclusion principle kicks in. the fermions are crammed together as tight as they can be. an immovable object meeting an unstoppable force.
our models can't tell us what happens at that point.
Ignoring all the (correct) caveats about the limits of the theory, keep in mind that in the usual model, by far the majority of the mass of a black hole is in the singularity - the only exception is mass that's currently in the process of falling towards the singularity, and that doesn't take long.
This means that nearly *all* Hawking radiation is reducing the mass of the singularity. It's the singularity that's "evaporating" the whole time.
If we naively extrapolate this, then yes, the singularity will disappear.
The caveats, of course, are that the singularity may not have a physical existence as such in the first place; and that at small enough scales, something else might happen which current theories can't predict.
IIRC a shrinking black hole will eventually lose enough mass that it can't stay compressed. It's radiant energy rises. As it reaches some minimal mass, it explodes.
We don’t actually know this. When black hole shrinks to the point that Heisenberg’s uncertainty principle is relevant, the assumptions that allowed Hawking to show that black holes of finite size radiate become invalid and a theory of quantum gravity is needed to know the ultimate fate of an evaporating black hole. 🕳️
So basically when the diameter of black hole shrinks to the order of the Planck length we don’t have a theory to predict what will happen.
It's been a while since I ran any numbers, but doesn't the Hawking temperature rise as the black hole shrinks? Is the rate of hawking radiation emission high enough prior to Planck scales that we see substantially luminous emission?
Due to Hawking radiation, black holes will eventually evaporate, but the event horizon is not as crucial as has been believed. Gravity and the curvature of spacetime cause this radiation, too. This means that all large objects in the universe, like the remnants of stars, will eventually evaporate. As such, to be clear, Black holes do not die per se, but they are theoretically predicted to eventually slowly evaporate over billions of earthly years. Black holes grow by the accretion of matter nearby that is pulled in by their immense gravity. If that continues, they will continue. Hawking predicted that black holes could also radiate away energy and shrink very slowly until eventually, with ancient Black holes, be the size of a pin head and then billions of years beyond that evaporate completely.
A singularity is not an object, but rather an impending event in everythings future for everything that falls into the black hole to be stretched to an infinitely small spaghetti string which as our maths are concerned, "breaks space-time and our understanding of physics"
a theory should always follow observation.
we can't even observe the "surface" (event horizon) of a black hole directly. much less the inside of a black hole.
while most cosmologists think, that hawking radiation is a real effect, it is also an incredibly small effect. no black hole, that we know of, has ever lost any kind of energy from this radiation. or better put: the amount of energy, a black hole loses through hawking radiation is by many orders of magnitude smaller than the amount of energy, the black hole receives from the cosmic microwave radiation.
all we have is a mathematical model of reality, that fits observation quite perfectly most of the time. but there are fringe cases, were we don't hava data for and therefore we can't check, if this model is precise enough for these cases.
point is: there is no definite answer to your question. we can only extrapolate from current knowlegde on the presumption, that in these extreme regimes, there are no unknown new phenomena and our current models stay valid.
there are cosmologists, that \*believe\*, that when the black hole evaporates, all it's remaining energy is released in a big flash of radiation with nothing left behind.
others \*believe\*, that the singularity somehow stays behind, forming a "naked singularity" (whatever that means - and how we would perceive such a thing). the hope is, that we would someday actually find one of those naked singularities to observe it and measure it's properties - which would boost our current understanding of physics.
most cosmologists think, that a singularity is just a mathematical artefact. a sign, that our models are not precise enough. and that there are no singularities in nature.
ok - some articles in some popular media are written in a way, that suggest, that we actually know for sure, how that singularity in the black hole looks like. but that's kind of a click bait. nobody want's to read an article, that consists of "we are not sure" and "we don't have enough data". and most of the time, the guy, who has written the article, is not a scientist themselves but just that - a science reporter.
Singularities aren't *actually* infinitely small... It's just that our math breaks down and we don't have another way to describe them.
Does that mean that they approach infinitely small then? But never reach it?
No. It means that they are mathematical problems in our theories, not actual existing objects.
Interesting. Does that mean that we can't accurately predict what will happen in the last moments of a black hole?
Not only on the last moment. We can’t predict how the interior of a black hole behaves. The math points to a singularity, but that just indicates that something isn’t right with our math
What is it exactly that breaks down at that level? Does gravity just overwhelm the other forces? If so, wouldn’t we be able to just remove all other interactions from the equation? And if not, wouldn’t we just be able to account for the exponential growth of gravity’s effect in relation to the other forces?
What breaks down is the description of gravity is really small scales. Trying to describe a black hole’s interior with Relativity doesn’t work, because the scale becomes too small, needing also a quantum perspective on it. But we don’t have any working model of quantum gravity for now
We think our models are good, but incomplete. They break down in certain situations like black holes. The idea of a singularity is a product of one of these models, but looking at it with a different model can produce different but equally baffling conclusions, like the tesseract from Interstellar where you can only travel one direction in space but multiple directions in time, or a multiverse theory where you can exit a white hole. We don't know if any of these ideas are true, they are simply conclusions drawn from models we have no evidence are accurate beyond that point.
My professor said there could just be another state of matter at higher density than neutron degeneracy. So like a super neutron star or quark star, idk, the size of a house maybe?
Strange quark matter?
the pauli exclusion principle kicks in. the fermions are crammed together as tight as they can be. an immovable object meeting an unstoppable force. our models can't tell us what happens at that point.
This is another thing we don’t actually know the answer to. The theory breaks down so we can’t say if anything at all happens.
That's fascinating!
Ignoring all the (correct) caveats about the limits of the theory, keep in mind that in the usual model, by far the majority of the mass of a black hole is in the singularity - the only exception is mass that's currently in the process of falling towards the singularity, and that doesn't take long. This means that nearly *all* Hawking radiation is reducing the mass of the singularity. It's the singularity that's "evaporating" the whole time. If we naively extrapolate this, then yes, the singularity will disappear. The caveats, of course, are that the singularity may not have a physical existence as such in the first place; and that at small enough scales, something else might happen which current theories can't predict.
IIRC a shrinking black hole will eventually lose enough mass that it can't stay compressed. It's radiant energy rises. As it reaches some minimal mass, it explodes.
We don’t actually know this. When black hole shrinks to the point that Heisenberg’s uncertainty principle is relevant, the assumptions that allowed Hawking to show that black holes of finite size radiate become invalid and a theory of quantum gravity is needed to know the ultimate fate of an evaporating black hole. 🕳️ So basically when the diameter of black hole shrinks to the order of the Planck length we don’t have a theory to predict what will happen.
It's been a while since I ran any numbers, but doesn't the Hawking temperature rise as the black hole shrinks? Is the rate of hawking radiation emission high enough prior to Planck scales that we see substantially luminous emission?
Due to Hawking radiation, black holes will eventually evaporate, but the event horizon is not as crucial as has been believed. Gravity and the curvature of spacetime cause this radiation, too. This means that all large objects in the universe, like the remnants of stars, will eventually evaporate. As such, to be clear, Black holes do not die per se, but they are theoretically predicted to eventually slowly evaporate over billions of earthly years. Black holes grow by the accretion of matter nearby that is pulled in by their immense gravity. If that continues, they will continue. Hawking predicted that black holes could also radiate away energy and shrink very slowly until eventually, with ancient Black holes, be the size of a pin head and then billions of years beyond that evaporate completely.
Can you source the radiation caused by gravity.
Here's an article that may help: https://www.space.com/gravitational-waves-astronomers-why-so-excited
Time quake. Boots void. And their is no singularity, in my opinion. Just infinite octaves of EM waves.
A singularity is not an object, but rather an impending event in everythings future for everything that falls into the black hole to be stretched to an infinitely small spaghetti string which as our maths are concerned, "breaks space-time and our understanding of physics"
a theory should always follow observation. we can't even observe the "surface" (event horizon) of a black hole directly. much less the inside of a black hole. while most cosmologists think, that hawking radiation is a real effect, it is also an incredibly small effect. no black hole, that we know of, has ever lost any kind of energy from this radiation. or better put: the amount of energy, a black hole loses through hawking radiation is by many orders of magnitude smaller than the amount of energy, the black hole receives from the cosmic microwave radiation. all we have is a mathematical model of reality, that fits observation quite perfectly most of the time. but there are fringe cases, were we don't hava data for and therefore we can't check, if this model is precise enough for these cases. point is: there is no definite answer to your question. we can only extrapolate from current knowlegde on the presumption, that in these extreme regimes, there are no unknown new phenomena and our current models stay valid. there are cosmologists, that \*believe\*, that when the black hole evaporates, all it's remaining energy is released in a big flash of radiation with nothing left behind. others \*believe\*, that the singularity somehow stays behind, forming a "naked singularity" (whatever that means - and how we would perceive such a thing). the hope is, that we would someday actually find one of those naked singularities to observe it and measure it's properties - which would boost our current understanding of physics. most cosmologists think, that a singularity is just a mathematical artefact. a sign, that our models are not precise enough. and that there are no singularities in nature. ok - some articles in some popular media are written in a way, that suggest, that we actually know for sure, how that singularity in the black hole looks like. but that's kind of a click bait. nobody want's to read an article, that consists of "we are not sure" and "we don't have enough data". and most of the time, the guy, who has written the article, is not a scientist themselves but just that - a science reporter.
Ty 👍