5 ms·

As someone with basically only popsci knowledge of black holes: people claiming it would be a literal point never made much sense - fundamentally, common sense

by rf15 1mo ago

As someone with basically only popsci knowledge of black holes: people claiming it would be a literal point never made much sense - fundamentally, common sense (as much as it can apply here) dictates that you cannot compress particles to an absolute point.

fangspire 1mo ago
[flagged]
- jambalaya8 1mo ago
  This needs a joke about unbelievable denseness.
goatlover 1mo ago
Aren't fundamental particles like electrons and quarks treated as points?
- kevindamm 1mo ago
  Kind of, but not really.. though there are simple models with electrons as a point charge, a more accurate model involves the electron field describing the probability of an electron existing at any region in space (not to be confused with the electromagnetic field, the medium in which photons propagate).
  - drdeca 1mo ago
    Sure the position of an electron is not definite, but neither is that of a buckyball, but a buckyball has a shape we can describe, an internal structure we regard as extended over space, in a way that is separate from the indeterminacy of its center of mass position. This is unlike an electron, for which, if we set aside the uncertainty as to its center of mass, my understanding is that the only internal degrees of freedom it has left (in the Standard Model) are its spin and whether it is left or right handed, with no other structure to it. It is in this sense that, AIUI, electrons are modeled as point particles. Of course, that doesn’t mean that if we zoom in enough, probing at higher and higher energy scales, that it can’t turn out to have some non-zero fundamental size outside of just uncertainty in its center of mass position. I think string theory would say that at the string scale it would be a string. But, AIUI, no experiment has shown it to have the kind of extent that would make it be called not a point particle (an extent in a sense beyond just uncertainty in COM position)
    - deleted 1mo ago
      [deleted]
- PaulHoule 1mo ago
  If you really treated them as points the theory would blow up because the electrostatic potential energy of a point charge is infinite. This is dealt with by “renormalization” which is roughly: assume the theory isn’t really valid all the way to a zero length scale and that we can average out everything that happens below some cutoff size and that it doesn’t really matter where we place the cutoff because the theory works the same if you change the cutoff and change the other parameters accordingly.
- somat 1mo ago
  They are, but there are some interesting theories about their internal structure. Be aware that this is probably junk science but I have currently been enjoying this effort to describe them via the em field. https://quicycle.com/understanding-electrons/ https://quicycle.com/understanding-electrons/ And the video essay on the subject https://www.youtube.com/watch?v=hYyrgDEJLOA https://www.youtube.com/watch?v=hYyrgDEJLOA (Huygens Optics: Williamson & Van der Mark electron model | Are electrons made of light?)
- TheOtherHobbes 1mo ago
  Points are a realist view - there's a real object there. Although some physicists disagree, QM slants very anti-realist. There are no objects anywhere, no particles, no waves, only probabilistic interactions, some of which can be snapshotted into localised partially definite results. So there are only interactions between probability distributions in space and time, and "particle-like events." No pointy objects, and no need for them.
  - goatlover 1mo ago
    QM slanting anit-realist is because some prominent physicists like Neils Bohr gave the math that interpretation, and they were more persuasive than the realists like Einstein, Schrodinger, Everett. The agnostic view is it's just a mathematical model that makes accurate probabilistic predictions when measurements are made, which says nothing about what's really going on. Of course treating particles as points is also mathematical.
  - inigyou 1mo ago
    Wouldn't it be both? Electrons occupy probability clouds, but the overall probabilities of things happening are summed over the whole cloud as if, at each point, the electron was a point particle at that point?
shagie 1mo ago
The question of "what holds it up?" is where that leads to. There's an interesting history of answering that question again and again - and the discovery of new types of stars each time. History of the Universe : What Is Hidden In The Core Of A Neutron Star? - https://youtu.be/YoYjkNQ27T8 https://youtu.be/YoYjkNQ27T8 That video goes into it... without getting mathy at any point. One of the bits that you're having trouble with is the compression of matter to a point. There's a theoretical type of black hole known as a kugelblitz - https://en.wikipedia.org/wiki/Kugelblitz_(astrophysics) https://en.wikipedia.org/wiki/Kugelblitz_(astrophysics) A kugelblitz is a theoretical astrophysical object predicted by general relativity. It is a concentration of heat, light, or radiation so intense that its energy forms an event horizon and becomes self-trapped. In other words, if enough radiation is aimed into a region of space, the concentration of energy can warp spacetime so much that it creates a black hole. This would be a black hole the original mass–energy of which was in the form of radiant energy rather than matter Rather than compressing particles, would you have difficulty with converting it to incredibly large amounts of energy that wraps space time into a singularity? If you packed enough photons into one spot, that energy would curve space time enough to form a black hole.
- tux3 1mo ago
  >Rather than compressing particles [...] If you packed enough photons into one spot I haven't watched the video, but if we're compressing electrons, neutrons, or other fermions, I imagine if we want to keep compressing that down to an arbitrarily small radius, won't we pretty quickly find it favorable to shift those fermions to something else, probably photons, to respect Pauli exclusion? Really, I don't know enough physics to figure out the reason why it shouldn't always end up in this incorporeal energy-curving-space situation either way, if we're compressing arbitrarily far.
  - georgeburdell 1mo ago
    Pauli Exclusion is just another “force” that can be overridden. Nature isn’t a list of rules
  - cscheid 1mo ago
cvoss 1mo ago
Common sense cannot be trusted on matters like these. Common sense is calibrated for reasoning over matters encountered in daily life. The further away we get from that, into more and more exotic phenomena, the less common sense can apply. Black holes are very far from the domain of common sense.
- ghosty141 1mo ago
  I always suggest looking at the quantum eraser experiment to see how bad common sense works with quantum mechanics. It's fairly simple but intuition fails most people when it comes to explaining how it works.
  - gerdesj 1mo ago
    No need for funky stuff, just do the classic (lol) Young's slits experiment which should be more than enough oddness for anyone. I was shown it at school, using microscope glass slides that we waved over a Bunsen burner running cold, to coat with soot. We then carefully etched parallel lines with a compass by hand. Our (~17 y/o) efforts were a bit random but we did get some smudgy banding results on the screen.
    - ambicapter 1mo ago
      Using a compass is interesting, use two razor blades taped together is much easier and it’s close enough to perfect parallel lines.
      - gerdesj 1mo ago
        It was the '80s so safety razor blades were available but in a posh public school (UK version) aged ~17, compasses were everywhere and large old style razor blades were not - the modern style razor with one or two thin blades was a thing. We could have probably got some needles from matron for a finer point, than a compass. Your pair of razor blades is a great solution.
XorNot 1mo ago
Common sense - the experience gained from your common everyday experience of reality - does not apply in black holes. Common sense would tell you they can't exist at all because you can't compress atoms - you have lived your entire life with atoms being entirely incompressible for the practical purpose of anything you do. Leaning on common sense to discuss fundamental physics has been wrong since round about the start of the practice of physics.
- inigyou 1mo ago
  Common sense actually says that atoms don't exist and if you squish cheese really hard you just get really hard and slightly smaller cheese, or maybe you invent a new type of dairy product.
  - ben_w 1mo ago
    Dunno, the ancient Greeks had roughly this idea (ἄτομον) in their philosophy, so while actual atomic theory is not common sense, merely having atoms is also not-*not* common sense.
- eru 1mo ago
  Funnily enough, technical speaking atoms are a small minority of ordinary matter, that is already excluding dark matter. That's because a lot of the ordinary mass in the universe is ionised or in other weirder states.
- GoblinSlayer 1mo ago
  There's indeed a problem with existence of black holes. Why would they exist? They are usually postulated into existence.
  - ben_w 1mo ago
    They're an automatic outcome of fairly benign starting conditions in GR: Simply having more than a certain amount of mass within a certain volume. The required density for that stuff goes down as the volume goes up, so a solar-system sized object (~77 AU radius) at mere normal sea-level (Earth) air density (1.2 kg/m^3) would just be one automatically. Given that the maths of GR requires spacetime to not have a singularity*, and yet it predicts a singularity from benign starting conditions, I take this as a sign that GR is not correct. But black holes are nonetheless an outcome, not a presumption. * it's more complicated than that
somat 1mo ago
My rather pop-sci understanding is that when you start playing around with relativity math, trying various masses and densities you hit something rather worrisome. As you approach some great, but still possible, value the plot goes infinite, the singularity. This is bad for the theory because going asymptotic like that usually indicates a fundamental problem in the math. But relativity does so well everywhere else... What if it could? And thus the black hole was born. The easy thing to miss, and blew my mind when I read it. is that general relativity is the concept of space-time, emphasis on the time, and this is also compressed by the mass, so if this singularity can actually occur it would also take an infinite amount of time to fall into it. So nothing can actually enter it. From the point of view of an astronaut(deliberately ignoring all the other relativistic implications) flying directly toward the event horizon. As you approach you will quickly see the rest of the universe age and die. and if hawking radiation is real the black hole will evaporate in front of you before you can reach it.
- saimiam 1mo ago
  Does time accelerate just for the astronaut approaching the black hole (meaning they would be witnessing the future) or does it accelerate for everyone (meaning approaching a black hole is going to make everything end quicker)?
  - somat 1mo ago
    My rather limited understanding is that. first there is a lot going on and due to the forces and gravitational gradients involved, matter itself probably would not survive the journey that close to the horizon. But ignoring that, When in compressed time, from the point of view of someone freefalling, timewise everything is normal, the rest of the universe has accelerated and in the case of a black hole has just aged out and died but you are fine. from the external point of view they are taking forever to get there. Where my imagination fails(above my pay grade) is in the face of infinity, what are the implications of infinite time compression?(everything happens at once?)
    - saimiam 1mo ago
__MatrixMan__ 1mo ago
A particle is a region of space where it's probable that a certain kind of interaction will happen. I don't see any reason why they can't overlap infinitely and then squeeze to the Dirac delta function: certain to be here, no error bars. That is, apart from the Pauli exclusion principle. But you have to leave that one behind if you're dealing with masses beyond the TOV limit. Of course I'm missing something here. I've taken QM and not GR so I would have this interpretation.
antonvs 1mo ago
> … you cannot compress particles to an absolute point. What do you mean by “particle” here? This kind of handwaving is fundamentally classical, and breaks down in the presence of quantum physics.
IsTom 1mo ago
Yeah, wouldn't this cause trouble with Pauli exclusion principle?
- inigyou 1mo ago
  Only if they all had the same energy level. And if they didn't form a superconductor. I'm not sure why they would but if they did they would violate it. That's actually what makes superconductors superconducting - the really weird state where electron pairs act like bosons.
the-mitr 1mo ago
Some of the most interesting and fundamental ideas in science are counter-intuitive
jibal 1mo ago
It's a complete violation of good sense to invoke common sense here. You talk about "particles" but that's not what the world is made of. Also, particle/wave duality. Also, any number of bosons can occupy the same position. Also black holes evaporate. And on and on.
eru 1mo ago
As far as anyone knows, electrons are already point masses.
vee-kay 1mo ago
[dead]

by rf15 1mo ago

fangspire 1mo ago

[flagged]

jambalaya8 1mo ago
This needs a joke about unbelievable denseness.

goatlover 1mo ago

Aren't fundamental particles like electrons and quarks treated as points?

kevindamm 1mo ago
Kind of, but not really.. though there are simple models with electrons as a point charge, a more accurate model involves the electron field describing the probability of an electron existing at any region in space (not to be confused with the electromagnetic field, the medium in which photons propagate).
- drdeca 1mo ago
  Sure the position of an electron is not definite, but neither is that of a buckyball, but a buckyball has a shape we can describe, an internal structure we regard as extended over space, in a way that is separate from the indeterminacy of its center of mass position. This is unlike an electron, for which, if we set aside the uncertainty as to its center of mass, my understanding is that the only internal degrees of freedom it has left (in the Standard Model) are its spin and whether it is left or right handed, with no other structure to it. It is in this sense that, AIUI, electrons are modeled as point particles. Of course, that doesn’t mean that if we zoom in enough, probing at higher and higher energy scales, that it can’t turn out to have some non-zero fundamental size outside of just uncertainty in its center of mass position. I think string theory would say that at the string scale it would be a string. But, AIUI, no experiment has shown it to have the kind of extent that would make it be called not a point particle (an extent in a sense beyond just uncertainty in COM position)
  - deleted 1mo ago
    [deleted]
PaulHoule 1mo ago
If you really treated them as points the theory would blow up because the electrostatic potential energy of a point charge is infinite. This is dealt with by “renormalization” which is roughly: assume the theory isn’t really valid all the way to a zero length scale and that we can average out everything that happens below some cutoff size and that it doesn’t really matter where we place the cutoff because the theory works the same if you change the cutoff and change the other parameters accordingly.
somat 1mo ago
They are, but there are some interesting theories about their internal structure. Be aware that this is probably junk science but I have currently been enjoying this effort to describe them via the em field. https://quicycle.com/understanding-electrons/ https://quicycle.com/understanding-electrons/ And the video essay on the subject https://www.youtube.com/watch?v=hYyrgDEJLOA https://www.youtube.com/watch?v=hYyrgDEJLOA (Huygens Optics: Williamson & Van der Mark electron model | Are electrons made of light?)
TheOtherHobbes 1mo ago
Points are a realist view - there's a real object there. Although some physicists disagree, QM slants very anti-realist. There are no objects anywhere, no particles, no waves, only probabilistic interactions, some of which can be snapshotted into localised partially definite results. So there are only interactions between probability distributions in space and time, and "particle-like events." No pointy objects, and no need for them.
- goatlover 1mo ago
  QM slanting anit-realist is because some prominent physicists like Neils Bohr gave the math that interpretation, and they were more persuasive than the realists like Einstein, Schrodinger, Everett. The agnostic view is it's just a mathematical model that makes accurate probabilistic predictions when measurements are made, which says nothing about what's really going on. Of course treating particles as points is also mathematical.
- inigyou 1mo ago
  Wouldn't it be both? Electrons occupy probability clouds, but the overall probabilities of things happening are summed over the whole cloud as if, at each point, the electron was a point particle at that point?

shagie 1mo ago

The question of "what holds it up?" is where that leads to. There's an interesting history of answering that question again and again - and the discovery of new types of stars each time. History of the Universe : What Is Hidden In The Core Of A Neutron Star? - https://youtu.be/YoYjkNQ27T8 https://youtu.be/YoYjkNQ27T8 That video goes into it... without getting mathy at any point. One of the bits that you're having trouble with is the compression of matter to a point. There's a theoretical type of black hole known as a kugelblitz - https://en.wikipedia.org/wiki/Kugelblitz_(astrophysics) https://en.wikipedia.org/wiki/Kugelblitz_(astrophysics) A kugelblitz is a theoretical astrophysical object predicted by general relativity. It is a concentration of heat, light, or radiation so intense that its energy forms an event horizon and becomes self-trapped. In other words, if enough radiation is aimed into a region of space, the concentration of energy can warp spacetime so much that it creates a black hole. This would be a black hole the original mass–energy of which was in the form of radiant energy rather than matter Rather than compressing particles, would you have difficulty with converting it to incredibly large amounts of energy that wraps space time into a singularity? If you packed enough photons into one spot, that energy would curve space time enough to form a black hole.

tux3 1mo ago
>Rather than compressing particles [...] If you packed enough photons into one spot I haven't watched the video, but if we're compressing electrons, neutrons, or other fermions, I imagine if we want to keep compressing that down to an arbitrarily small radius, won't we pretty quickly find it favorable to shift those fermions to something else, probably photons, to respect Pauli exclusion? Really, I don't know enough physics to figure out the reason why it shouldn't always end up in this incorporeal energy-curving-space situation either way, if we're compressing arbitrarily far.
- georgeburdell 1mo ago
  Pauli Exclusion is just another “force” that can be overridden. Nature isn’t a list of rules
- cscheid 1mo ago

cvoss 1mo ago

Common sense cannot be trusted on matters like these. Common sense is calibrated for reasoning over matters encountered in daily life. The further away we get from that, into more and more exotic phenomena, the less common sense can apply. Black holes are very far from the domain of common sense.

ghosty141 1mo ago
I always suggest looking at the quantum eraser experiment to see how bad common sense works with quantum mechanics. It's fairly simple but intuition fails most people when it comes to explaining how it works.
- gerdesj 1mo ago
  No need for funky stuff, just do the classic (lol) Young's slits experiment which should be more than enough oddness for anyone. I was shown it at school, using microscope glass slides that we waved over a Bunsen burner running cold, to coat with soot. We then carefully etched parallel lines with a compass by hand. Our (~17 y/o) efforts were a bit random but we did get some smudgy banding results on the screen.
  - ambicapter 1mo ago
    Using a compass is interesting, use two razor blades taped together is much easier and it’s close enough to perfect parallel lines.
    - gerdesj 1mo ago
      It was the '80s so safety razor blades were available but in a posh public school (UK version) aged ~17, compasses were everywhere and large old style razor blades were not - the modern style razor with one or two thin blades was a thing. We could have probably got some needles from matron for a finer point, than a compass. Your pair of razor blades is a great solution.

XorNot 1mo ago

Common sense - the experience gained from your common everyday experience of reality - does not apply in black holes. Common sense would tell you they can't exist at all because you can't compress atoms - you have lived your entire life with atoms being entirely incompressible for the practical purpose of anything you do. Leaning on common sense to discuss fundamental physics has been wrong since round about the start of the practice of physics.

inigyou 1mo ago
Common sense actually says that atoms don't exist and if you squish cheese really hard you just get really hard and slightly smaller cheese, or maybe you invent a new type of dairy product.
- ben_w 1mo ago
  Dunno, the ancient Greeks had roughly this idea (ἄτομον) in their philosophy, so while actual atomic theory is not common sense, merely having atoms is also not-*not* common sense.
eru 1mo ago
Funnily enough, technical speaking atoms are a small minority of ordinary matter, that is already excluding dark matter. That's because a lot of the ordinary mass in the universe is ionised or in other weirder states.
GoblinSlayer 1mo ago
There's indeed a problem with existence of black holes. Why would they exist? They are usually postulated into existence.
- ben_w 1mo ago
  They're an automatic outcome of fairly benign starting conditions in GR: Simply having more than a certain amount of mass within a certain volume. The required density for that stuff goes down as the volume goes up, so a solar-system sized object (~77 AU radius) at mere normal sea-level (Earth) air density (1.2 kg/m^3) would just be one automatically. Given that the maths of GR requires spacetime to not have a singularity*, and yet it predicts a singularity from benign starting conditions, I take this as a sign that GR is not correct. But black holes are nonetheless an outcome, not a presumption. * it's more complicated than that

somat 1mo ago

My rather pop-sci understanding is that when you start playing around with relativity math, trying various masses and densities you hit something rather worrisome. As you approach some great, but still possible, value the plot goes infinite, the singularity. This is bad for the theory because going asymptotic like that usually indicates a fundamental problem in the math. But relativity does so well everywhere else... What if it could? And thus the black hole was born. The easy thing to miss, and blew my mind when I read it. is that general relativity is the concept of space-time, emphasis on the time, and this is also compressed by the mass, so if this singularity can actually occur it would also take an infinite amount of time to fall into it. So nothing can actually enter it. From the point of view of an astronaut(deliberately ignoring all the other relativistic implications) flying directly toward the event horizon. As you approach you will quickly see the rest of the universe age and die. and if hawking radiation is real the black hole will evaporate in front of you before you can reach it.

saimiam 1mo ago
Does time accelerate just for the astronaut approaching the black hole (meaning they would be witnessing the future) or does it accelerate for everyone (meaning approaching a black hole is going to make everything end quicker)?
- somat 1mo ago
  My rather limited understanding is that. first there is a lot going on and due to the forces and gravitational gradients involved, matter itself probably would not survive the journey that close to the horizon. But ignoring that, When in compressed time, from the point of view of someone freefalling, timewise everything is normal, the rest of the universe has accelerated and in the case of a black hole has just aged out and died but you are fine. from the external point of view they are taking forever to get there. Where my imagination fails(above my pay grade) is in the face of infinity, what are the implications of infinite time compression?(everything happens at once?)
  - saimiam 1mo ago

__MatrixMan__ 1mo ago

A particle is a region of space where it's probable that a certain kind of interaction will happen. I don't see any reason why they can't overlap infinitely and then squeeze to the Dirac delta function: certain to be here, no error bars. That is, apart from the Pauli exclusion principle. But you have to leave that one behind if you're dealing with masses beyond the TOV limit. Of course I'm missing something here. I've taken QM and not GR so I would have this interpretation.

antonvs 1mo ago

> … you cannot compress particles to an absolute point. What do you mean by “particle” here? This kind of handwaving is fundamentally classical, and breaks down in the presence of quantum physics.

IsTom 1mo ago

Yeah, wouldn't this cause trouble with Pauli exclusion principle?

inigyou 1mo ago
Only if they all had the same energy level. And if they didn't form a superconductor. I'm not sure why they would but if they did they would violate it. That's actually what makes superconductors superconducting - the really weird state where electron pairs act like bosons.

the-mitr 1mo ago

Some of the most interesting and fundamental ideas in science are counter-intuitive

jibal 1mo ago

It's a complete violation of good sense to invoke common sense here. You talk about "particles" but that's not what the world is made of. Also, particle/wave duality. Also, any number of bosons can occupy the same position. Also black holes evaporate. And on and on.

eru 1mo ago

As far as anyone knows, electrons are already point masses.

vee-kay 1mo ago

[dead]