Black holes might be defects in spacetime(phys.org)
phys.org
Black holes might be defects in spacetime
https://phys.org/news/2023-05-black-holes-defects-spacetime.html
301 comments
> The real takeaway is that researchers may have found a potential test for string theory.
Not really. All this paper is really saying is that they have found solutions in classical theories of gravity with extra dimensions that, in four dimensions, can look like standard black holes. So even observing effects predicted by these models would not be evidence for string theory. It would at best be evidence for possible extra dimensions of spacetime at the classical level.
Also, the paper only compares its models with the standard Schwarzschild black hole. But first, most black holes are spinning so the comparison should be with Kerr, not Schwarzschild; and second, as the paper notes early on, there are many other proposed models of compact objects that can look similar to standard black holes. Any given set of observations would have to be tested against all proposed models, not just this one.
Not really. All this paper is really saying is that they have found solutions in classical theories of gravity with extra dimensions that, in four dimensions, can look like standard black holes. So even observing effects predicted by these models would not be evidence for string theory. It would at best be evidence for possible extra dimensions of spacetime at the classical level.
Also, the paper only compares its models with the standard Schwarzschild black hole. But first, most black holes are spinning so the comparison should be with Kerr, not Schwarzschild; and second, as the paper notes early on, there are many other proposed models of compact objects that can look similar to standard black holes. Any given set of observations would have to be tested against all proposed models, not just this one.
Given that there is no absolute position in spacetime and everything is relative, in what sense is a black hole "spinning"?
Can't we just pick as a reference the black hole, and say that the everything else is spinning, just as well?
Can't we just pick as a reference the black hole, and say that the everything else is spinning, just as well?
> in what sense is a black hole "spinning"?
There are several equivalent ways of stating it:
(1) The hole's spacetime geometry is axisymmetric but not spherically symmetric;
(2) The hole has a Killing vector field that is timelike at infinity but is not hypersurface orthogonal;
(3) The hole has nonzero angular momentum as viewed in the asymptotically flat region at infinity.
> Can't we just pick as a reference the black hole, and say that the everything else is spinning, just as well?
No. All three of the above conditions are invariant and only depend on the spacetime geometry; they are unaffected by any choice of coordinates or the motion of any outside observers.
There are several equivalent ways of stating it:
(1) The hole's spacetime geometry is axisymmetric but not spherically symmetric;
(2) The hole has a Killing vector field that is timelike at infinity but is not hypersurface orthogonal;
(3) The hole has nonzero angular momentum as viewed in the asymptotically flat region at infinity.
> Can't we just pick as a reference the black hole, and say that the everything else is spinning, just as well?
No. All three of the above conditions are invariant and only depend on the spacetime geometry; they are unaffected by any choice of coordinates or the motion of any outside observers.
No, spinning is an accelerated reference frame. If you spin on a carousel, you won’t feel the same as standing still.
Now what does it mean for a black hole, which we assume to be a singularity occupying no space at all, to be spinning? We don’t know. That’s one of the gaps in our theory. But as the collapsed remnants of an object that was spinning, they should have done residual angular momentum.
Now what does it mean for a black hole, which we assume to be a singularity occupying no space at all, to be spinning? We don’t know. That’s one of the gaps in our theory. But as the collapsed remnants of an object that was spinning, they should have done residual angular momentum.
> spinning is an accelerated reference frame
Not necessarily. The three definitions for a "spinning" black hole that I gave upthread do not require the presence of any accelerated frames or observers.
> what does it mean for a black hole, which we assume to be a singularity occupying no space at all
This is not correct. A black hole is a finite region of spacetime enclosed by an event horizon. The singularity is inside the hole but is not all of the hole.
> to be spinning? We don’t know.
Yes, we do. We have known since the 1960s that the Kerr solution to the Einstein Field Equation describes a spinning black hole, and all of the geometric properties of that solution have been known for almost as long as that.
> That’s one of the gaps in our theory.
No, it's not. See above.
> as the collapsed remnants of an object that was spinning, they should have done residual angular momentum.
This is correct, but it does not imply or support your other claims.
Not necessarily. The three definitions for a "spinning" black hole that I gave upthread do not require the presence of any accelerated frames or observers.
> what does it mean for a black hole, which we assume to be a singularity occupying no space at all
This is not correct. A black hole is a finite region of spacetime enclosed by an event horizon. The singularity is inside the hole but is not all of the hole.
> to be spinning? We don’t know.
Yes, we do. We have known since the 1960s that the Kerr solution to the Einstein Field Equation describes a spinning black hole, and all of the geometric properties of that solution have been known for almost as long as that.
> That’s one of the gaps in our theory.
No, it's not. See above.
> as the collapsed remnants of an object that was spinning, they should have done residual angular momentum.
This is correct, but it does not imply or support your other claims.
You're missing the point that none of the three definitions you provided offer a mechanistic explanation.
Not a physicist, but no.
An object can spin relative to itself. Particles away from the center are constantly accelerating. Gravity or physical connection are the forces that prevent these particles from flying away.
Thinking about it, I am not even sure an object can spin relative to another object. Orbit sure, but not spin.
An object can spin relative to itself. Particles away from the center are constantly accelerating. Gravity or physical connection are the forces that prevent these particles from flying away.
Thinking about it, I am not even sure an object can spin relative to another object. Orbit sure, but not spin.
> An object can spin relative to itself. Particles away from the center are constantly accelerating. Gravity or physical connection are the forces that prevent these particles from flying away.
This is a reasonable description of spin for an ordinary object, but it can't be used for a black hole, because a black hole is a vacuum solution; it has no "particles". See my other post upthread for better ways to view spin for a black hole.
> I am not even sure an object can spin relative to another object. Orbit sure, but not spin.
The usual definition of "spin" makes use of the object's center of mass frame, yes. Orbital angular momentum is thus separated out.
Note, though, that strictly speaking, in relativity there is no invariant way to make this split. It works very well as an approximation for most objects (like planets and stars), but there are complications when one tries to apply it to things like black holes. That's one reason why physicists prefer other ways of defining "spinning" for black holes that don't involve any split between orbital and spin angular momentum.
This is a reasonable description of spin for an ordinary object, but it can't be used for a black hole, because a black hole is a vacuum solution; it has no "particles". See my other post upthread for better ways to view spin for a black hole.
> I am not even sure an object can spin relative to another object. Orbit sure, but not spin.
The usual definition of "spin" makes use of the object's center of mass frame, yes. Orbital angular momentum is thus separated out.
Note, though, that strictly speaking, in relativity there is no invariant way to make this split. It works very well as an approximation for most objects (like planets and stars), but there are complications when one tries to apply it to things like black holes. That's one reason why physicists prefer other ways of defining "spinning" for black holes that don't involve any split between orbital and spin angular momentum.
I think there are all sorts of other potential tests of string theory. The problem is that for all the actual tests that were ever proposed, it failed (supersymmetry, various proposals for sizes of the extra dimensions).
To be fair, what failed is low-energy Supersymmetry and large extra dimensions, because these things were actually accessible by current gen experiments. But there's a huuuge amount of room left unexplored.
That's my point: what experiments could be performed have been performed, and have failed.
Also, it is a massive weakness of the theory that it can be used to predict such varied values. This is a big part of why it is not exactly a scientific theory: it is not really falsifiable, since you can tweak it to predict any value you want. If we had the kind of particle accelerators needed to test high-energy supersymmetry, and if it failed again, it could be adjusted to predict higher-energy supersymmetry, and since the number line extends towards infinity, this would never stop.
Also, it is a massive weakness of the theory that it can be used to predict such varied values. This is a big part of why it is not exactly a scientific theory: it is not really falsifiable, since you can tweak it to predict any value you want. If we had the kind of particle accelerators needed to test high-energy supersymmetry, and if it failed again, it could be adjusted to predict higher-energy supersymmetry, and since the number line extends towards infinity, this would never stop.
I think you are correct, ST is closer to mathematical abstraction than an actual physical theory. I think that makes it more useful than less useful though.
Wouldn't that mean it is just more useful in mathematical reality but less useful in physical reality?
Can't you disprove string theory by disproving quantum physics?
Not without fine-tuning. The issue is that high-energy supersymmetry no longer removes the "ugly constants" of the standard model -- it just shifts them somewhere else. Disclaimer: not a physicist, but I learned a lot reading "Lost in Math: How Beauty Leads Physics Astray".
…by Sabine Hossenfelder.
I treat her like Jordan Peterson. Obviously smart, but also obviously bitter and if/when they have a valid point I’m sure someone else has said it in a less grating manner.
I treat her like Jordan Peterson. Obviously smart, but also obviously bitter and if/when they have a valid point I’m sure someone else has said it in a less grating manner.
Physics needs more insider critics. She's oppositional but - unlike Peterson - she does know what she's talking about.
Sabine argues the data, in good(ish) faith, but she does carry a chip on her shoulder.
Peterson does not argue data - he suggests analogies and then holds those analogies as iron-clad transitive relationships to argue his preconceived position.
Peterson does not argue data - he suggests analogies and then holds those analogies as iron-clad transitive relationships to argue his preconceived position.
I hear this a lot from people. As a non-physicist who enjoys her content, what am I missing? is she wrong on any specific physics? Without specific criticism this comes off as insiders being upset that a fellow insider is critical of the field
Part of the issue for me is that I don't think her research on quantum foundations is viewed very highly. Some would probably consider it completely pointless. In her videos, she claims that the majority of physicists do not understand quantum mechanics and that AI might find patterns in the randomness of quantum mechanics. This doesn't put her tendancy to tell lay people how everyone else's research is a waste of time in a good light. She's just arguing that her research is more deserving of funding.
Plenty of her points aren't without merit but she's frequently disengenious and doesn't give the full argument for what she criticises.
An example is her criticism on "decoherence solves the measurement issue" where she explains the average of multiple particles doesn't tell you what happens to just one of the particles involved. She's not wrong in the example she gives but decoherence actually can be applied to a single particle. Compare with PBS space time, they present both sides and offer an opinion as their opinion not fact.
I recently watched a lecture on issues in particle physics. Naturalness was mentioned due to a need to ensure the theory gave sensible answers, to ensure it was renormalizable, that's far more reasonable to how Sabine presents it.
Plenty of her points aren't without merit but she's frequently disengenious and doesn't give the full argument for what she criticises.
An example is her criticism on "decoherence solves the measurement issue" where she explains the average of multiple particles doesn't tell you what happens to just one of the particles involved. She's not wrong in the example she gives but decoherence actually can be applied to a single particle. Compare with PBS space time, they present both sides and offer an opinion as their opinion not fact.
I recently watched a lecture on issues in particle physics. Naturalness was mentioned due to a need to ensure the theory gave sensible answers, to ensure it was renormalizable, that's far more reasonable to how Sabine presents it.
I'm no insider but I haven't found Hossenfelder's stuff that impressive. Her reasoning tends to take the form "X is true, therefore Y", where "if X then Y" is a valid deduction, and X hasn't been proven false, so we can't say she's wrong on specific physics. But the presumption that X is true is unjustified even if X hasn't been proven false. Example: she likes superdeterminism instead of quantum mechanics with its various weird consequences. Ok, her version of superdeterminism hasn't been proven wrong, but that's a long way off from saying that it is right. It comes down to her saying "I believe X and I haven't been proven wrong, even though most other physicists believe not-X, but I like my theory better, so there". Perfectly fine and legit, but I'll take X seriously when I see more recognition for it from the rest of physics.
The same goes for this stuff about tests of string theory. As far as I can tell, string theory is perfectly good physics whether or not it is experimentally testable. That is, there is a viewpoint called "naive Popperianism" that if something isn't experimentally testable then it it isn't science, but from what I can tell, that viewpoint is not truly decisive (thus "naive"), and its proponents don't have the authority that they wish they did. As a comparable situation, there is not much dispute that general relativity (GR) is perfectly good physics except at the center of a black hole, where it predicts a singularity which people consider non-physical. Particularly, GR makes predictions about the interior of black holes (points inside the event horizon) that are considered perfectly good except at the center. But, since there is no way to observe the inside of a black hole, those predictions of GR are also not verifiable. So I'm not bothered by unverifiability. Theory is good if it has explanatory or interpretive power, not just testable predictive power.
The same goes for this stuff about tests of string theory. As far as I can tell, string theory is perfectly good physics whether or not it is experimentally testable. That is, there is a viewpoint called "naive Popperianism" that if something isn't experimentally testable then it it isn't science, but from what I can tell, that viewpoint is not truly decisive (thus "naive"), and its proponents don't have the authority that they wish they did. As a comparable situation, there is not much dispute that general relativity (GR) is perfectly good physics except at the center of a black hole, where it predicts a singularity which people consider non-physical. Particularly, GR makes predictions about the interior of black holes (points inside the event horizon) that are considered perfectly good except at the center. But, since there is no way to observe the inside of a black hole, those predictions of GR are also not verifiable. So I'm not bothered by unverifiability. Theory is good if it has explanatory or interpretive power, not just testable predictive power.
GR is ok, the problem is with researchers that use GR for work in quantum gravity, like information paradox.
> is she wrong on any specific physics?
She's not wrong about any of the empirical content of physics (so far as we know), but neither are the people she criticizes. It's a philosophical conflict. Most physicists are at least weakly inclined towards scientific realism, whereas Hossenfelder is a radical instrumentalist - and doesn't seem to think any other view is even worth engaging with.
She's not wrong about any of the empirical content of physics (so far as we know), but neither are the people she criticizes. It's a philosophical conflict. Most physicists are at least weakly inclined towards scientific realism, whereas Hossenfelder is a radical instrumentalist - and doesn't seem to think any other view is even worth engaging with.
Jordan Peterson now is so far gone into the far right now it's not remotely comparable.
Maybe been you mean Jordan Peterson the year 1 edition where he was still talking about personal responsibility.
Maybe been you mean Jordan Peterson the year 1 edition where he was still talking about personal responsibility.
Jordan Peterson has had many iterations. The year -5 edition had good psychology lectures and I disagree with the above poster who says he doesn't know what he is talking about. Within his academic realm, I think he did, although there would be points other academics would contest (this is what academics do). He has then gone through at least two transformations.
His position regarding a lot of religious topics seems tainted by his personal beliefs.
He makes frequent reference to judaeo-christian archetypes, which seems to me to grossly overstate the relevance of the belief systems.
The fundamental archetypes represented in the human mind are far older than any current form of religion, to the extent that there's overlap then either the archetypes have been co-opted, or have been overlaid with a culturally mediated avatars.
I don't think that you ever find him framing those underlying structures in a way that does not tie back to Christ.
He makes frequent reference to judaeo-christian archetypes, which seems to me to grossly overstate the relevance of the belief systems.
The fundamental archetypes represented in the human mind are far older than any current form of religion, to the extent that there's overlap then either the archetypes have been co-opted, or have been overlaid with a culturally mediated avatars.
I don't think that you ever find him framing those underlying structures in a way that does not tie back to Christ.
> which seems to me to grossly overstate the relevance of the belief systems.
It is hardly possible to overstate the relevance of those archetypes and beliefs. Nothing else has been more widespread on earth for as long to have anywhere close to the same influence on humanity.
It is hardly possible to overstate the relevance of those archetypes and beliefs. Nothing else has been more widespread on earth for as long to have anywhere close to the same influence on humanity.
I'm not familiar enough to know what a "Judeo-Christian archetype" is, but Indian/Chinese origin religions are older, just about as numerous, and not particularly similar.
(Where Buddhism is similar, it's because "religion" as a concept had to be made legible to Westerners when they showed up so they wouldn't colonize you so hard, and they did this by putting Western philosophy in it.)
(Where Buddhism is similar, it's because "religion" as a concept had to be made legible to Westerners when they showed up so they wouldn't colonize you so hard, and they did this by putting Western philosophy in it.)
Things like the virgin mother (bare in mind, much like Peterson, I'm pulling this out of my arse).
My take on that it is a perspective based subset of actuality; in the case of the mother (as opposed) to the wife, 'she' is measured from the perspective of the child, she has her nurturing capabilities but not those of reproduction.
Reproduction is outside of the child's need to understand, and is not a property of the mother as it is seen from the child's perspective.
Bare in mind that the archetype is always perceived by the child, the husband will see something else.
These restrictions are based on perspective and need, and are reflective only of a limited subset of reality.
Christianity has taken that childish abstraction, and declared it to be an actual thing, that actually existed.
It doesn't take much consideration to understand that virgins don't give birth to sons (and if they ever give birth to daughters, they'll be genetic clones of the mother).
My take on that it is a perspective based subset of actuality; in the case of the mother (as opposed) to the wife, 'she' is measured from the perspective of the child, she has her nurturing capabilities but not those of reproduction.
Reproduction is outside of the child's need to understand, and is not a property of the mother as it is seen from the child's perspective.
Bare in mind that the archetype is always perceived by the child, the husband will see something else.
These restrictions are based on perspective and need, and are reflective only of a limited subset of reality.
Christianity has taken that childish abstraction, and declared it to be an actual thing, that actually existed.
It doesn't take much consideration to understand that virgins don't give birth to sons (and if they ever give birth to daughters, they'll be genetic clones of the mother).
This is a tongue in cheek response to your interesting reply: it is certainly possible now scientifically for virgins to give birth to sons.
> Where Buddhism is similar, it's because "religion" as a concept had to be made legible to Westerners when they showed up so they wouldn't colonize you so hard, and they did this by putting Western philosophy in it.)
Reworded: Where Buddhism is similar, it's because Westerners showed up and were going to colonize anyone who didn't have something called a "religion", so they had to turn it into a recognizable "religion", which they did by copying a bunch of Western philosophy. So the older forms were even less similar.
Reworded: Where Buddhism is similar, it's because Westerners showed up and were going to colonize anyone who didn't have something called a "religion", so they had to turn it into a recognizable "religion", which they did by copying a bunch of Western philosophy. So the older forms were even less similar.
I do not mean in terms of pervasiveness - I mean in terms of them innately making up a piece of the underlying structures of human consciousness.
And to the extent that those beliefs are actually archetypal, they are not fundamentally judaeo-christian but predate and have been co-opted by those religions.
And to the extent that those beliefs are actually archetypal, they are not fundamentally judaeo-christian but predate and have been co-opted by those religions.
Hm, that seems like the opposite of Jordan Peterson (who is obviously an idiot, but has a good voice for TV)
"low-energy Supersymmetry" oh, you mean 8 TeV wasn't enough? This kind of reasoning is just like the ether, people keep harping on a god of the gaps explanation for the failure of the search.
Yeah, it’s more they might have found a way to test the latest fix, than anything.
Even if it were testable, and the test failed to validate string theory, I don't think that would convince string theorists one way or another. Strings are a de facto religion within physics.
This line of talk is way overplayed. Like people who have an enthusiast amount of knowledge follow a few people who have professional knowledge who are just unreasonably fixated on what other physicists pursue.
Doubt and questioning are a part of science but this "religion" meme about string theory et al is silly. If you're really upset that somebody is pursuing something is a blind alley, go ahead and do some physics that shows results, otherwise I really wish people would tone the unhelpful criticisms down.
Doubt and questioning are a part of science but this "religion" meme about string theory et al is silly. If you're really upset that somebody is pursuing something is a blind alley, go ahead and do some physics that shows results, otherwise I really wish people would tone the unhelpful criticisms down.
I agree. If every physicist quit string theory because we haven’t thought of a way to test it, like what @ravenstein might want, then that would be a sad day.
I don’t see the problem with physicists working on or even promoting string theory.
I don’t see the problem with physicists working on or even promoting string theory.
I am not a physicist, but what I have read from critics (badly paraphrased):
During the hype phase of string theory, every major university wanted to get in on the game, and devoted large amounts of funding towards hiring researchers with a background in string theory. If you weren't one of those people, you were at a severe disadvantage, and might not get hired at all.
String theory hovered up tons of cash in university budgets, and majorly fucked over a lot of careers. The result of all this money has been no actual scientifically proven results despite decades of research.
During the hype phase of string theory, every major university wanted to get in on the game, and devoted large amounts of funding towards hiring researchers with a background in string theory. If you weren't one of those people, you were at a severe disadvantage, and might not get hired at all.
String theory hovered up tons of cash in university budgets, and majorly fucked over a lot of careers. The result of all this money has been no actual scientifically proven results despite decades of research.
> devoted large amounts of funding towards hiring researchers with a background in string theory. If you weren't one of those people, you were at a severe disadvantage, and might not get hired at all.
> String theory hovered up tons of cash in university budgets, and majorly fucked over a lot of careers.
This is pretty misleading. An argument could be made - though I'm not necessarily endorsing it - that string theory has crowded out other quantum gravity research programs in the last few decades. But quantum gravity is a small and poorly funded subfield: we're talking about no more than a few hundred people total in the US, fighting over one medium-sized experiment worth of grant money. None of it makes any difference to the overwhelming majority of physicists.
> String theory hovered up tons of cash in university budgets, and majorly fucked over a lot of careers.
This is pretty misleading. An argument could be made - though I'm not necessarily endorsing it - that string theory has crowded out other quantum gravity research programs in the last few decades. But quantum gravity is a small and poorly funded subfield: we're talking about no more than a few hundred people total in the US, fighting over one medium-sized experiment worth of grant money. None of it makes any difference to the overwhelming majority of physicists.
If there was a more promising theory to investigate in, we would have done that, right?
Even today, we don't really have anything much better than string theory.
Even today, we don't really have anything much better than string theory.
No one is saying that string theory shouldn't be investigated.
Apologies. It was unclear what your desired goal from your original post.
> Strings are a de facto religion within physics.
I don't think string theorists are being unreasonable by not having changed their minds yet, given that no evidence has come out one way or the other.
I don't think we can extrapolate from "string theorists didn't update when presented with no evidence" to "string theorists won't update when presented with evidence".
I don't think string theorists are being unreasonable by not having changed their minds yet, given that no evidence has come out one way or the other.
I don't think we can extrapolate from "string theorists didn't update when presented with no evidence" to "string theorists won't update when presented with evidence".
There has been evidence though. All tests so far have been negative. Low energy SUSY, extra dimensions
“Science advances one funeral at a time”
- Max Planck
- Max Planck
Sadly, this is true of many things these days.
I don’t think it’s a these days thing at all.
I think it’s a human thing and every generation has to deal with the fanatics or believers or whatever you want to call it of their time.
We’re in a time where a great number of people are extremely religious without having any idea they are. The people that live by what their screen tells them. If you didn’t see some of this in the last three years that there is religion without it being labeled as such, I don’t know I’ll be able to reach you now.
I think it’s a human thing and every generation has to deal with the fanatics or believers or whatever you want to call it of their time.
We’re in a time where a great number of people are extremely religious without having any idea they are. The people that live by what their screen tells them. If you didn’t see some of this in the last three years that there is religion without it being labeled as such, I don’t know I’ll be able to reach you now.
We all live by what our screens tell us. We don't know anything outside of our own direct experience without depending on others. And for the most part we choose to trust others and it usually works out ok. That's not religion - that's an efficient way to intake information about the world, because an individual doesn't have the resources to learn about everything or go every place. If someone abuses our trust, then it's not a problem with the delivery method, it's a problem with them. So the fact that we get a lot of information via a screen is irrelevant.
Though I'm not sure what that has to do with the notion that bad ideas only die when the people who hold them die.
Though I'm not sure what that has to do with the notion that bad ideas only die when the people who hold them die.
Just because all religions are a belief doesn’t mean all beliefs are a religion.
https://en.wikipedia.org/wiki/Affirming_the_consequent
https://en.wikipedia.org/wiki/Affirming_the_consequent
I agree with your first sentence for sure.
It’s human nature for older people to be more conservative. Transcends time and culture.
It’s human nature for older people to be more conservative. Transcends time and culture.
Are you sure you’re not emphasizing my second point by thinking what I wrote was an attack of one ideology vs another?
I'm not sure what you're trying to say and I wouldn't go that far. But it's pretty straightforward to say, yes, older people like change less than younger people, even if they aren't fanatics.
Lol … I think the technical term for this is “hater”
I don't see how this is testable, given what is written here.
>If the researchers can discover an important observational difference between topological solitons and traditional black holes, this might pave the way to finding a way to test string theory itself.
This is a big if. For now they've just shown that once again something in the string theory landscape could look like something in real life.
This is a big if. For now they've just shown that once again something in the string theory landscape could look like something in real life.
I know it is the standard nomenclature, but I object to it being called string theory, as it is at best a hypothesis, if not even just philosophical speculation with more math.
It can make no predictions, it is not falsifiable, it meets none of the constraints that allow something to be science.
It can make no predictions, it is not falsifiable, it meets none of the constraints that allow something to be science.
> just philosophical speculation with more math
Speaking of nomenclature, this is not a good characterization of what philosophy is, if your intention is to reduce philosophy to what you seem to have in mind for “philosophical speculation”. Metaphysical theory thoroughly supported by argument (hylomorphic dualism, theory of act and potency) is actually stronger than mere empirical science. Empirically testable predictions do not transcend reasoned argument as observation is interpreted though the body of propositions of prior theory and enters into scientific argument as argument.
Speaking of nomenclature, this is not a good characterization of what philosophy is, if your intention is to reduce philosophy to what you seem to have in mind for “philosophical speculation”. Metaphysical theory thoroughly supported by argument (hylomorphic dualism, theory of act and potency) is actually stronger than mere empirical science. Empirically testable predictions do not transcend reasoned argument as observation is interpreted though the body of propositions of prior theory and enters into scientific argument as argument.
I think string theory is so pupular is exactly because it can make predictions that classical particle theory cannot.
Are you sure? I thought that was why it had largely fallen out of favor. The predictions it makes are not testable.
String theory is basically just noodles on the wall these days trying to find what sticks. mostly without basis and 99.9% of it falls off eventually as it's not backed by anything of substance.
> Its presumed lack of falsifiability has been one of its drawbacks[..]
Given that the definition of a theory is an hypothesis that can be tested for falsehood, it isn't a theory by definition. It is a hypothesis.. but presumably "string hypothesis" doesn't sound as nice.
Given that the definition of a theory is an hypothesis that can be tested for falsehood, it isn't a theory by definition. It is a hypothesis.. but presumably "string hypothesis" doesn't sound as nice.
From https://journals.aps.org/prd/abstract/10.1103/PhysRevD.107.0... :
> We show that topological solitons are remarkably similar to black holes in apparent size and scattering properties, while being smooth and horizonless. Incoming photons experience very high redshift, inducing phenomenological horizonlike behaviors from the point of view of photon scattering. Thus, they provide a compelling case for real-world gravitational solitons and topological alternatives to black holes from string theory.
This is certainly interesting but so far they have only looked into Schwarzschild black holes (the simplest kind of black holes). Their case would be much more compelling if they also found soliton solutions that looked like non-static (Kerr) or even non-stationary/dynamic black hole solutions (<-> black hole formation). I know far too little about solitons, unfortunately, to estimate how easy/difficult it would be to find/construct those.
> We show that topological solitons are remarkably similar to black holes in apparent size and scattering properties, while being smooth and horizonless. Incoming photons experience very high redshift, inducing phenomenological horizonlike behaviors from the point of view of photon scattering. Thus, they provide a compelling case for real-world gravitational solitons and topological alternatives to black holes from string theory.
This is certainly interesting but so far they have only looked into Schwarzschild black holes (the simplest kind of black holes). Their case would be much more compelling if they also found soliton solutions that looked like non-static (Kerr) or even non-stationary/dynamic black hole solutions (<-> black hole formation). I know far too little about solitons, unfortunately, to estimate how easy/difficult it would be to find/construct those.
> only looked into Schwarzschild black holes
What plane is the authors' "equatorial plane"? Shortly after their eqn (31), "One should a priori do a similar computation out of the equatorial plane to obtain the total size of the solitons. Due to the complexity of the geodesic equations, this is only possible numerically. However, we will see in the next section that the outer photon shell is actually almost spherically symmetric and slightly flattened at its poles". (ETA: "... the Schwarzschild topological solution is not spherically symmetric ...", just before section A. Methodology).
Central SMBHs' spin appears to be largely far from parallel to their host galaxies' angular momentum[1]. Spin gives us an equatorial plane for the SMBH. Is there physical motivation for picking an equatorial plane if we found an SMBH with negligible J (and no jets)? I don't doubt that people would land on some convention (e.g. equatorial plane parallel to host galaxy's north if available, our galaxy's north if not), but do doubt that the convention would reflect physics (i.e., that there is such a plane where J = 0 or even that such a plane is relevant where J <<< 1, even if the plane is thereby picked out) rather than useful coordinates.
I scanned the paper only briefly (I'm not really interested in black holes out of a cosmological or at least astrophysical context and am in no hurry to jump ahead of further EHT results) but found myself curious about the authors' "these solutions can be embedded in string theory" as their ref [17] at first glance seems to be about AdS, an acronym which is found only once in this paper.
What provokes my wondering is in particular, "and so an asymptotic observer will barely notice the difference between the parallax angles" (among other references to an asymptotic observer), drawing a comparison with a distant Schwarzschild observer, again around eqn (31). "Barely notice" is, at least qualitatively, interesting wording. Can an observer at infinity more than barely notice the difference between a cold noncompact spherically symmetric uncharged nonspinning central mass and a Schwarzschild BH?
[1] This is especially true for Sgr A*, see EHT paper https://iopscience.iop.org/article/10.3847/2041-8213/ac6674 which is wildly "tilt"ed (to use authors' expression).
What plane is the authors' "equatorial plane"? Shortly after their eqn (31), "One should a priori do a similar computation out of the equatorial plane to obtain the total size of the solitons. Due to the complexity of the geodesic equations, this is only possible numerically. However, we will see in the next section that the outer photon shell is actually almost spherically symmetric and slightly flattened at its poles". (ETA: "... the Schwarzschild topological solution is not spherically symmetric ...", just before section A. Methodology).
Central SMBHs' spin appears to be largely far from parallel to their host galaxies' angular momentum[1]. Spin gives us an equatorial plane for the SMBH. Is there physical motivation for picking an equatorial plane if we found an SMBH with negligible J (and no jets)? I don't doubt that people would land on some convention (e.g. equatorial plane parallel to host galaxy's north if available, our galaxy's north if not), but do doubt that the convention would reflect physics (i.e., that there is such a plane where J = 0 or even that such a plane is relevant where J <<< 1, even if the plane is thereby picked out) rather than useful coordinates.
I scanned the paper only briefly (I'm not really interested in black holes out of a cosmological or at least astrophysical context and am in no hurry to jump ahead of further EHT results) but found myself curious about the authors' "these solutions can be embedded in string theory" as their ref [17] at first glance seems to be about AdS, an acronym which is found only once in this paper.
What provokes my wondering is in particular, "and so an asymptotic observer will barely notice the difference between the parallax angles" (among other references to an asymptotic observer), drawing a comparison with a distant Schwarzschild observer, again around eqn (31). "Barely notice" is, at least qualitatively, interesting wording. Can an observer at infinity more than barely notice the difference between a cold noncompact spherically symmetric uncharged nonspinning central mass and a Schwarzschild BH?
[1] This is especially true for Sgr A*, see EHT paper https://iopscience.iop.org/article/10.3847/2041-8213/ac6674 which is wildly "tilt"ed (to use authors' expression).
From a layperson's perspective, "discovered" is doing a LOT of work in the linked article given it appears to be a hypothetical construct (topological soliton) within a hypothetical construct (string theory).
It is perfectly reasonable to use the word "discovered" for purely mathematical facts for which the demonstration is non-trivial.
If it were phrased as "discovered a mathematical solution in string theory that would, if confirmed, represent a topological soliton" that would strike me as more accurate. But this is the reason I stated up front that I'm a layperson: I can certainly imagine that within the community there are conventional uses of language that differ from a layperson's use. That's certainly the case in my own. But the way it is phrased appears, to a layperson, to indicate that the thing has been found to exist.
From another layperson's perspective, it sounds like you are arguing it is "perfectly common" whereas the parent is arguing "it is unreasonable, even if it is common"
Parent here. That's the implication, but my intent was somewhat gentler, along the lines of "Using what appears to be professional language shortcuts common in an industry is sometimes suboptimal when communicating with interested laypersons." I'm making a few assumptions there (first that "discovered" has a commonly accepted meaning in the field and second that that's how it's being used ... and I guess third that there are probably more laypersons than theoretical physicists on HN). I just don't want to hear from my curious but uninformed cousin that "hey did you hear that black holes are just space knots??!!" any more than I have to.
I guess that depends on how much of a Platonist you are :-D
I am an anti-platonist but still think its reasonable to say one discovered a mathematical fact. All this amounts to is discovering that you can reach a sentence in a formal language using the rules of the language and the axioms. One can believe that a recipe for pancakes exists without believing it does so via participating in an unseen ideal world.
All my life, they've been hawking string theory; what feels like 40-odd years of breathless articles in New Scientist and on "Horizon". I don't really understand why it's still funded.
String theory has been pretty useful outside of string theory proper. There are analogies to lots of other systems which I think continues to breathe life into the research. See: https://www.quantamagazine.org/string-theorys-strange-second...
> “It’s hard to say really where you should draw the boundary around and say: This is string theory; this is not string theory,” said Douglas Stanford, a physicist at the IAS. “Nobody knows whether to say they’re a string theorist anymore,” said Chris Beem, a mathematical physicist at the University of Oxford. “It’s become very confusing.”
I knew some string people who easily transitioned into other fields (like condensed matter) because the work was similar. I don't personally see it as a huge waste of time, and it's like the least expensive thing to fund.
> “It’s hard to say really where you should draw the boundary around and say: This is string theory; this is not string theory,” said Douglas Stanford, a physicist at the IAS. “Nobody knows whether to say they’re a string theorist anymore,” said Chris Beem, a mathematical physicist at the University of Oxford. “It’s become very confusing.”
I knew some string people who easily transitioned into other fields (like condensed matter) because the work was similar. I don't personally see it as a huge waste of time, and it's like the least expensive thing to fund.
I find this funny as well. A lot of complaints about all the funding for string theory, but it seems like just funding mathematicians, which is dirt cheap compared to anything else.
Of course they don’t know whether they’re string theorists! Nobody knows whether theorists are made of strings or not! That’s the whole point of lacking experimental verification!
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The basic thing here is that 1) we can guess from pretty basic physics that black holes have an entropy. 2) in order for a black hole to have an entropy it must have microscopic degrees of freedom. 3) String theory is one of the few ways we've ever come close to actually calculating from microscopic degrees of freedom the entropy we "know" black holes should have. I think most physicists, even string theorists (perhaps them more than others) understand that there are physical and philosophical problems with string theory, but I think most folks also think its the closest thing we have to a working theory and that it is probably a useful language in which to cast certain calculations in lieu of a more complete or rigorous theory.
I'd also like to point out that the actual total funding for string theory is extremely tiny compared to scientific research funding in general since it is a theoretical discipline with very few practitioners. If you want to attach inefficiencies in scientific funding, the LHC is a much better target. I'm a physicist and have an interest in theory, and even I think that we spend too much money on particle accelerators given what we stand to learn from them and the other pressing problems the human race has. I'd be delighted to see all that money re-allocated to large scale public works building solar panels and infrastructure or just giving it to poor people.
I'd also like to point out that the actual total funding for string theory is extremely tiny compared to scientific research funding in general since it is a theoretical discipline with very few practitioners. If you want to attach inefficiencies in scientific funding, the LHC is a much better target. I'm a physicist and have an interest in theory, and even I think that we spend too much money on particle accelerators given what we stand to learn from them and the other pressing problems the human race has. I'd be delighted to see all that money re-allocated to large scale public works building solar panels and infrastructure or just giving it to poor people.
If we follow Pareto principle, then it doesn't make sense to optimize spendings that are close to zero if compared with something like military spendings.
https://en.wikipedia.org/wiki/Pareto_principle
Even if string theory is just pure math with no base in reality, it still can be useful (any math domain for that matter).
https://en.wikipedia.org/wiki/Pareto_principle
Even if string theory is just pure math with no base in reality, it still can be useful (any math domain for that matter).
I don't think the spending is really a problem, but possibly the many work-hours of brilliant minds that might be more fruitfully employed working on different problems.
Let's not pick on the LHC for that. How many gobsmackingly brilliant engineer-hours have gone into optimizing ad targeting or fine-tuning purchase attribution?
Not to mention, the LHC is responsible for a lot of innovation in it's own right, just in terms of hardware, software, etc.
The bigger picture is that only so many resources are going to be devoted to researching fundamental physics (both money and hours of work from human beings). If the majority of those resources are focused on a dead-end theory, then the opportunity cost is quite literally everything else.
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It’s noble to want to help the poor but the economy isn’t zero sum in that way.
Almost all the surplus we have could be traced back to our discoveries in physics leading to machines.
People lived much much poorer lives without modern physics discoveries.
The expects return on physics is so great we should find ways to afford more long shot experiments not less.
Almost all the surplus we have could be traced back to our discoveries in physics leading to machines.
People lived much much poorer lives without modern physics discoveries.
The expects return on physics is so great we should find ways to afford more long shot experiments not less.
Sorry, but _even as a physicist_ I think the idea that the expected returns for society of discovering some other obscure standard model particle are trivial to nothing. Literally useless knowledge and only of interest to a tiny minority of people (of whom I am a part, I admit). Like seriously. Consider: how has anyone's life been improved by the discovery of the Higgs? By the absence of Supersymmetry?
We don’t know yet. To be determined. But science has taken us pretty far.
Neural network algorithm research was considered more of an academic endeavor rather than something that could have practical implications from the 1960s to even the early 2000s, compared to other machine learning algorithms. Look at where it took us today.
This is overblown. The vast majority of improvements to human lives can from textile and agricultural revolutions. Physics supplemented these, sure, but it wasn’t thanks to a few dudes hiding out in a lab doing theory.
This is some galaxy brain shit.
I don't understand why it wouldn't be?
One of the most fundamental scientific facts is that quantum theory (the most precisely tested theory in human history) and general relativity are incomplete. There must be a bridge. And we have no idea what that bridge is. It's been this way for over a century; the lifespan of string theory is not so long in comparison. Until we find a way to falsify it, we have to keep trying, don't we?
One of the most fundamental scientific facts is that quantum theory (the most precisely tested theory in human history) and general relativity are incomplete. There must be a bridge. And we have no idea what that bridge is. It's been this way for over a century; the lifespan of string theory is not so long in comparison. Until we find a way to falsify it, we have to keep trying, don't we?
Opportunity costs. The real debate has been whether it makes sense for string theory (whatever the prevailing definition is) to dominate funding for theoretical research of the "bridge". There are alternatives besides strings for the bridge, and there should be even more, in theory...
I don't know enough about the history of funding theoretical physics research to comment on that one way or another. However, neither did the comment I was replying to reference any actual facts about the distribution of funding that might suggest any of them had been wasted.
The fact is, we have no falsifiable theories that can unite GR and QM. Should every theory be abandoned that doesn't quickly lead to a resolution? No, clearly not. So the question is what kind of criteria we could use to determine that string theory is a dead end or is otherwise stifling true progress.
And that's pretty much what I was trying to ask previously... is ST actually sucking all the air out of the room? I'm a layperson and not just going to assume that hundreds of experts have blown their careers doing pointless calculations on a theory that "obviously" isn't worth the resources put into it. But the comment I replied to seemed to be making that assumtpion,
The fact is, we have no falsifiable theories that can unite GR and QM. Should every theory be abandoned that doesn't quickly lead to a resolution? No, clearly not. So the question is what kind of criteria we could use to determine that string theory is a dead end or is otherwise stifling true progress.
And that's pretty much what I was trying to ask previously... is ST actually sucking all the air out of the room? I'm a layperson and not just going to assume that hundreds of experts have blown their careers doing pointless calculations on a theory that "obviously" isn't worth the resources put into it. But the comment I replied to seemed to be making that assumtpion,
Yep, or at least until we find something else that is explaining things better and testing better and looks like a better path forward. As much as I dislike ST because of the ambiguity/vagueness that means it's so hard to nail down as a single concrete theory, the alternatives so far still also have a lot of those same issues (e.g. too many parameters, effectively impossible to test, etc.) so there's no reason to drop ST just yet as useless or an invalid theory.
> Until we find a way to falsify it, we have to keep trying, don't we?
By that same token, we should keep looking for the fountain of eternal youth in El Dorado until it can be conclusively proven it doesn't exist.
A theory which is not falsifiable is not a scientific theory, at least in principle, and it is hard to tell why it should be entertained for quite so long.
By that same token, we should keep looking for the fountain of eternal youth in El Dorado until it can be conclusively proven it doesn't exist.
A theory which is not falsifiable is not a scientific theory, at least in principle, and it is hard to tell why it should be entertained for quite so long.
While I agree with the general premise, don't you think that if we were to find a simple explaination that elegantly explains many things at once, it would be at least worth a try to find ways of falsifying that explaination?
Not at any cost of course, but the falsifications gathered e.g. in trying to disprove the string theory might also help us figure out what is actually going on.
Not at any cost of course, but the falsifications gathered e.g. in trying to disprove the string theory might also help us figure out what is actually going on.
Sure, but once it keeps failing for a few decades, and given that ST is significantly more complex than either QM or GR, not simpler, there has to come a time where it simply is abandoned, even if it hasn't been disproven.
A few decades…
How long did it take to go from Principia to General Relativity?
How long did it take to go from Principia to General Relativity?
Principia was proven right at every turn, and explained all of the observed mechanics experiments, all the way up until Maxwell's equations were formalized and their effects tested out, some 200 years after it was published. It's also important the theories it replaced were massively more complex.
Maxwell's equations were first formulated in 1865, the "patch" to Newton's theories was formulated soon after (the luminiferous aether), the Michelson-Morley experiment proving the patch did not work was run in 1887, and the theory of special relativity was proposed in 1905 - so it took about 20 years at most between Newtonian mechanics being conclusively proven to contradict experiments and a new theory becoming proeminent. And special relativity was quickly replaced with general relativity (just 10 years later), because, despite its success, its limitations were immediately apparent.
Maxwell's equations were first formulated in 1865, the "patch" to Newton's theories was formulated soon after (the luminiferous aether), the Michelson-Morley experiment proving the patch did not work was run in 1887, and the theory of special relativity was proposed in 1905 - so it took about 20 years at most between Newtonian mechanics being conclusively proven to contradict experiments and a new theory becoming proeminent. And special relativity was quickly replaced with general relativity (just 10 years later), because, despite its success, its limitations were immediately apparent.
What's the difference between electromagnetic field and ether?
As far as I understand it, the ether was supposed to be matter, ultimately made out of some kind of particles that obey laws of motion.
Conversely, the electric field is just a potential. It's not made up of anything, it just describes how charged particles interact if they are in a particular place in space-time.
Conversely, the electric field is just a potential. It's not made up of anything, it just describes how charged particles interact if they are in a particular place in space-time.
Pretty sure electric field is material. Interaction is described by theory, not by field, field is material nature of interaction.
Yes, but we shouldn’t pull that theory out our mathematical asses. We should always be falsifying things not trying to make an unfalsifiable theory work because the math is interesting.
The bridge is "simply" doing the math of quantum mechanics in the curved spacetime of general relativity instead of the flat one.
Why do you assume there is a bridge? Or even if there is one, why do you assume that descriptions of that bridge in a mathematical language is at all possible?
We do know that mathematical frameworks cannot be at the same time totally complete and internally consistent. Would it be a stretch to assume descriptions of our physical reality could have the same restriction? General relativity and Quantum mechanics are relatively complete in describing our physical reality, however they are not consistent with each other. Perhaps if we ever find a description that is consistent, it won’t be complete. Perhaps grand unified theories are simply a mathematical impossibility.
We do know that mathematical frameworks cannot be at the same time totally complete and internally consistent. Would it be a stretch to assume descriptions of our physical reality could have the same restriction? General relativity and Quantum mechanics are relatively complete in describing our physical reality, however they are not consistent with each other. Perhaps if we ever find a description that is consistent, it won’t be complete. Perhaps grand unified theories are simply a mathematical impossibility.
The problem with this line of thinking comes from the way the problem is posed. The reality is worse for both GR and QM.
QM is not a theory about small particles: it is a theory that describes the evolution of any object whatsoever. It just happens to be completely wrong for large objects. And even if we accepted that there is some objective cutoff points between "small objects" and "large objects" (the "objective collapse" interpretation), it would still be wrong, because it predicts effects like gravitational lensing don't exist.
Conversely, GR is also a theory about any size of object; and it is also completely wrong when tested on small objects, as it predicts effects like the self-interference of particles don't exist.
And again, even if some kind of objective boundary existed between the domains of GR and QM existed, that would need to be incorporated into the maths of both of them, and questions about behaviors close to that margin would arise.
QM is not a theory about small particles: it is a theory that describes the evolution of any object whatsoever. It just happens to be completely wrong for large objects. And even if we accepted that there is some objective cutoff points between "small objects" and "large objects" (the "objective collapse" interpretation), it would still be wrong, because it predicts effects like gravitational lensing don't exist.
Conversely, GR is also a theory about any size of object; and it is also completely wrong when tested on small objects, as it predicts effects like the self-interference of particles don't exist.
And again, even if some kind of objective boundary existed between the domains of GR and QM existed, that would need to be incorporated into the maths of both of them, and questions about behaviors close to that margin would arise.
I see. So me and my parent are both wrong. The problem isn’t about a lack of bridge, or inconsistencies/incompleteness, it is about a lack of well defined scopes for each theory.
In a sibling post I talk about how this is not a problem in psychology, and ask what the difference is. This answers that question kind of well, the difference is that in psychology/sociology the scopes are well defined. We know what a population is and apply sociology to it, and we know what an individual human being is, and apply psychology to it.
With quantum mechanics and general relativity the scope is supposed to be the cosmos, but both theories fail on some places in the cosmos. So either the theories are wrong, or the scopes are wrong. I’m leaning towards the latter.
In a sibling post I talk about how this is not a problem in psychology, and ask what the difference is. This answers that question kind of well, the difference is that in psychology/sociology the scopes are well defined. We know what a population is and apply sociology to it, and we know what an individual human being is, and apply psychology to it.
With quantum mechanics and general relativity the scope is supposed to be the cosmos, but both theories fail on some places in the cosmos. So either the theories are wrong, or the scopes are wrong. I’m leaning towards the latter.
The problem is that scale is completely smooth. IF there were some strict scale at which each theory applies, as I said, you'd then have problems for phenomena that straddle that scope. You can always add an extra electron or atom to a clump, so you'd have objects oscillating between obeying one set of equations vs the other, which seems very very very hard to actually believe.
A similar problem actually exists in psychology vs sociology, though it seems you choose to ignore it. When you want to study the behavior of two human beings (say, a married childless couple), do you apply sociology or psychology? How about a married couple with children? An extended family?
Also, psychology has to explain how an individual human behaves inside of a population, and sociology has to explain how the behavior of groups emerges out of the individual psychologies of their constituents. If they don't do this, then either one or both theories must be wrong. To take an extreme silly example, if psychology predicted that no person would never choose to kill themselves for the sake of another; but sociology predicted groups of people regularly have members sacrificing themselves for the group - then one of the theories must be wrong, you can't just say "we apply one theory when talking to a man and another when talking about the group".
A similar problem actually exists in psychology vs sociology, though it seems you choose to ignore it. When you want to study the behavior of two human beings (say, a married childless couple), do you apply sociology or psychology? How about a married couple with children? An extended family?
Also, psychology has to explain how an individual human behaves inside of a population, and sociology has to explain how the behavior of groups emerges out of the individual psychologies of their constituents. If they don't do this, then either one or both theories must be wrong. To take an extreme silly example, if psychology predicted that no person would never choose to kill themselves for the sake of another; but sociology predicted groups of people regularly have members sacrificing themselves for the group - then one of the theories must be wrong, you can't just say "we apply one theory when talking to a man and another when talking about the group".
> So either the theories are wrong, or the scopes are wrong. I’m leaning towards the latter.
Well, no. That's not really possible here. The scopes can't be adjusted. The theories are wrong. They both must explain all physical phenomena, but neither does, therefore a more accurate theory exists which we have not found yet.
I just don't know if there's much value in trying to make an analogy to psychology here. Currently it seems to be getting in the way of understanding.
Well, no. That's not really possible here. The scopes can't be adjusted. The theories are wrong. They both must explain all physical phenomena, but neither does, therefore a more accurate theory exists which we have not found yet.
I just don't know if there's much value in trying to make an analogy to psychology here. Currently it seems to be getting in the way of understanding.
>because it predicts effects like gravitational lensing don't exist.
But we use gravitational lensing, and the amount of lensing is predicted by GR?
I don't understanding this statement. Is there some additional affect around lensing we should see if quantum gravity is a thing?
But we use gravitational lensing, and the amount of lensing is predicted by GR?
I don't understanding this statement. Is there some additional affect around lensing we should see if quantum gravity is a thing?
No no; I'm saying that if you apply QM as it exists today to describe the motion of light beams around the sun, you will not get any effect similar to gravitational lensing. Since gravitational lensing is a real effect that we have clearly seen, it means that QM as it exists today is just wrong (in its predictions about how light moves around the sun).
GR does of course predict gravitational lensing. However, if you used the formulae of GR to compute the motion of photons passing through a double-slit experiment, the solution would show two different bright spots, corresponding to the two slits; in reality, we see an interference pattern. So GR is also wrong.
By definition, a (correct) theory of quantum gravity would predict both gravitational lensing and the way photons behave in a dobule-slit experiment (otherwise, we would say that either the theory is wrong, or it is not a theory of quantum gravity). However, no such theory exists today, at least none that doesn't contradict other observations.
GR does of course predict gravitational lensing. However, if you used the formulae of GR to compute the motion of photons passing through a double-slit experiment, the solution would show two different bright spots, corresponding to the two slits; in reality, we see an interference pattern. So GR is also wrong.
By definition, a (correct) theory of quantum gravity would predict both gravitational lensing and the way photons behave in a dobule-slit experiment (otherwise, we would say that either the theory is wrong, or it is not a theory of quantum gravity). However, no such theory exists today, at least none that doesn't contradict other observations.
There are already experiments (and simulations) which show Raychaudhuri focusing and Einstein lensing in purely-quantum analog gravity (see e.g. <https://scitechdaily.com/bridging-quantum-theory-and-relativ...> for something moderately accessible that allows for attaching a causal cone at each point in a relevant analog spacetime), so
> no; I'm saying that if you apply QM as it exists today to describe the motion of light beams around the sun, you will not get any effect similar to gravitational lensing
falls down because we can describe such an effect purely quantum mechanically.
Also, I think you should be put to proof with respect to a claim against quantum perturbative or canonical methods in the solar-mass lensing regime in which perturbation theory works great for classical GR, taking into account all sorts of beyond-leading-order (classical) effects like noncircularity, backreaction, helicity, you name it. The sun is a fixed enough background that it's a linearized gravity problem. What exactly in "QM as it exists today" breaks (or is broken by) this?
> ... if you used the formulae of GR to compute the motion of photons passing through a double-slit experiment ... GR is also wrong.
How exactly does taking the fully Lorentz-invariant QED or Standard Model to local Lorentz-invariance (with the radius of curvature significantly larger than the laboratory experiment) break the picture? We are nowhere near needing to consult Birrell & Davies.
What do you think needs doing here if "you used the formulae of GR", beyond solving the EFEs and the geodesic equations for the whole (region of) spacetime, and then wondering what geodesic any given photon will couple to? What do you think the scale of the correction from Minkowskian geodesics will be? And how much of that do you impute to the apparatus?
> no; I'm saying that if you apply QM as it exists today to describe the motion of light beams around the sun, you will not get any effect similar to gravitational lensing
falls down because we can describe such an effect purely quantum mechanically.
Also, I think you should be put to proof with respect to a claim against quantum perturbative or canonical methods in the solar-mass lensing regime in which perturbation theory works great for classical GR, taking into account all sorts of beyond-leading-order (classical) effects like noncircularity, backreaction, helicity, you name it. The sun is a fixed enough background that it's a linearized gravity problem. What exactly in "QM as it exists today" breaks (or is broken by) this?
> ... if you used the formulae of GR to compute the motion of photons passing through a double-slit experiment ... GR is also wrong.
How exactly does taking the fully Lorentz-invariant QED or Standard Model to local Lorentz-invariance (with the radius of curvature significantly larger than the laboratory experiment) break the picture? We are nowhere near needing to consult Birrell & Davies.
What do you think needs doing here if "you used the formulae of GR", beyond solving the EFEs and the geodesic equations for the whole (region of) spacetime, and then wondering what geodesic any given photon will couple to? What do you think the scale of the correction from Minkowskian geodesics will be? And how much of that do you impute to the apparatus?
It’s sort of incomprehensible that there wouldn’t be, even if that bridge is forever incomprehensible to us. There are boundaries between where GR and QM are predictive, so presumably, unless there’s some strange smooth transition of equations between those two regimes (which would itself lend itself to a mathematical theory), then there must be a consistent set of equations which explain both regimes consistently and simultaneously.
Coming from psychology this feels alien to me. In psychology there is a definite boundary between individual behavioral dynamics and population behavioral dynamics. There is no smooth transition between the two, either you describe the individual or you describe a group, you cannot do both (even thought debates about IQ here on HN will have you believe otherwise) and there is certainly no smooth transition.
How is the boundary between GR and QM different from the boundary of psychology and sociology?
How is the boundary between GR and QM different from the boundary of psychology and sociology?
I would say it is completely different. In physics, quantum mechanics gives extremely precise and verifiable predictions of the outcomes of experiments within a certain range of physical conditions. So does general relativity. In contrast, psychology has no mathematical model that will, for example, accurately predict what I am going to eat for lunch, nor is there a model that predicts the exact outcomes of elections. Since physics has two models which are exquisitely precise in different size regimes, but which are mutually incompatible, you have a definite puzzle about what happens in situations where the effects of both theories should be important. There are no exquisitely precise and accurate mathematical models of anything in the social sciences, as far as I am aware.
Im neither a psychologist nor a physicist, but I think one can analogize population vs individual behaviour to condensed matter physics versus particle physics. Condensed matter physics finds emergent behaviour in large clumps of stuff that would, in principle, be totally predictable from first principles (the standard model), but which in practice are quite difficult to guess a priori. Different scales lend themselves to different tools, since nonlinear dynamics (chaos) makes it intractable to apply bedrock reductionist formulae to large systems. The higher order behaviour of complex systems is in no way less interesting or true, I would argue, than the seemingly simpler behaviour of very small systems.
In contrast to condensed matter vs the standard theory (QM basically), QM vs GR has fundamental incongruities, since both theories make claims about what happens at the same scale. Only one (or most likely neither) can be correct at the event horizon and center of a black hole.
In contrast to condensed matter vs the standard theory (QM basically), QM vs GR has fundamental incongruities, since both theories make claims about what happens at the same scale. Only one (or most likely neither) can be correct at the event horizon and center of a black hole.
The difference would be that the laws of physics are much more rigorous than the 'laws' of psychology/sociology.
Outliers in the latter aren't necessarily indicative of anything wrong with theory in general, while even a single outlier in anything in the former is indicative of an incomplete model.
There are various results in physics which should be predictable via both GR and QM independently. The results should be the same as both models are supposed to be describing the same thing, so it follows that there should be some sort of gradual transition as one set of effects gradually comes to dominate over the other. Otherwise we'd see a single point in the data where QM stops being accurate and GR takes over, but despite investigating so many different scales, we have not seen any such cutoff point.
Outliers in the latter aren't necessarily indicative of anything wrong with theory in general, while even a single outlier in anything in the former is indicative of an incomplete model.
There are various results in physics which should be predictable via both GR and QM independently. The results should be the same as both models are supposed to be describing the same thing, so it follows that there should be some sort of gradual transition as one set of effects gradually comes to dominate over the other. Otherwise we'd see a single point in the data where QM stops being accurate and GR takes over, but despite investigating so many different scales, we have not seen any such cutoff point.
> In psychology there is a definite boundary between individual behavioral dynamics and population behavioral dynamics.
I'm aware of my own behavior as an individual being influenced by social context, is that not the kind of bleed over you might look for? Maybe you're referring to specific concepts I'm not actually even understanding.
I'm aware of my own behavior as an individual being influenced by social context, is that not the kind of bleed over you might look for? Maybe you're referring to specific concepts I'm not actually even understanding.
You still use theories from psychology to describe the interaction. This is precisely what social-psychology does (admittedly spectacularly often without replication). And a good social psychology theory is consistent with other fields of psychology, like cognitive, or—more often—behavioral psychology. You don’t use population statistics to predict how you as an individual will behave in a certain situation.
If you could precisely and reliably describe and predict individual behavior for any individual, then population behavior would follow directly from those laws.
> In psychology there is a definite boundary between individual behavioral dynamics and population behavioral dynamics.
> either you describe the individual or you describe a group
In gravitational physics, with respect to a flow in a dynamical system (an example is galaxies in an expanding universe) we can use a Lagrangian observer (e.g., one galaxy, drifting along with the flow, tracing out a pathline/worldtube that depends on features like its mass-evolution and proper motion within a cluster of galaxies) or a Eulerian observer (e.g. a notional observer with no spatial motion at all, watching alllll the galaxy clusters jiggle, swirl, turn, and age a little differently in relation to her). One can convert observations of each type of observer to the other in a rigorous mathematical procedure, since they are just two (families of) the infinity of different observers allowed by even just Special Relativity. See e.g. <https://en.wikipedia.org/wiki/Lagrangian_and_Eulerian_specif...> for more detail.
>> There are boundaries between where GR and QM are predictive
> this feels alien to me
You can do both quantum matter and classical General Relativity in one of several effective field theories, which I'll return to below.
GR and relativistic quantum field theories (QFT) purport to make accurate predictions in strong gravity, which one only finds deep within black holes (i.e., not on our side of any horizon), but they make very different predictions in that regime pretty generically. Generically in the sense that choosing different behaviours of particle-particle interactions (and self-interactions) do not really move the needle on GR's prediction of a collapse to a core of infinite density. However, in various approaches which convert GR's classical gravitational waves into large number of gravitons, one can write down a matter QFT in which charged particles' self-interaction can lead to a degeneracy pressure (a repulsive force) that increases at higher particle energies such that they overwhelm gravitational collapse at very high but finite density in black holes of arbitrary mass.
In weak gravity, like we have in our solar system, QFTs allow us to prepare significant masses in superpositions of (spatial) position. General relativity does not allow for such superpositions. We are approaching lab-testability, with results from sensitive accelerometers allowed to point at tiny superposed masses.
However, in regimes far from (non-negligibly) gravitating superpositons and strong gravity, GR and QFT are usefully (and possibly fully) compatible. We get good results in astrophysics from semi-clasical gravity, where the classical curved spacetime of General Relativity couples with the expectation value of QFT matter (i.e., we average out some quantum weirdness and justify this by the weak gravitational effects of the "lumpy" weirdness being practically impossible to measure; superpositions and ultra-high-energy/ultra-high-denisty systems might be too lumpy).
We also get good results from perturbative quantum gravity and canonical quantum gravity, for example. Neither of these latter two is really classical General Relativity so they can deal with the gravitation of superposed matter (otherwise they give for all practical purposes the same answers as semiclassical gravity). These approaches do not work in strong gravity, however. Essentially they become calculationally intractable or they crash into unresolved problems splitting spacetime into space and time (in order to do time-dependent quantum mechanics).
> either you describe the individual or you describe a group
In gravitational physics, with respect to a flow in a dynamical system (an example is galaxies in an expanding universe) we can use a Lagrangian observer (e.g., one galaxy, drifting along with the flow, tracing out a pathline/worldtube that depends on features like its mass-evolution and proper motion within a cluster of galaxies) or a Eulerian observer (e.g. a notional observer with no spatial motion at all, watching alllll the galaxy clusters jiggle, swirl, turn, and age a little differently in relation to her). One can convert observations of each type of observer to the other in a rigorous mathematical procedure, since they are just two (families of) the infinity of different observers allowed by even just Special Relativity. See e.g. <https://en.wikipedia.org/wiki/Lagrangian_and_Eulerian_specif...> for more detail.
>> There are boundaries between where GR and QM are predictive
> this feels alien to me
You can do both quantum matter and classical General Relativity in one of several effective field theories, which I'll return to below.
GR and relativistic quantum field theories (QFT) purport to make accurate predictions in strong gravity, which one only finds deep within black holes (i.e., not on our side of any horizon), but they make very different predictions in that regime pretty generically. Generically in the sense that choosing different behaviours of particle-particle interactions (and self-interactions) do not really move the needle on GR's prediction of a collapse to a core of infinite density. However, in various approaches which convert GR's classical gravitational waves into large number of gravitons, one can write down a matter QFT in which charged particles' self-interaction can lead to a degeneracy pressure (a repulsive force) that increases at higher particle energies such that they overwhelm gravitational collapse at very high but finite density in black holes of arbitrary mass.
In weak gravity, like we have in our solar system, QFTs allow us to prepare significant masses in superpositions of (spatial) position. General relativity does not allow for such superpositions. We are approaching lab-testability, with results from sensitive accelerometers allowed to point at tiny superposed masses.
However, in regimes far from (non-negligibly) gravitating superpositons and strong gravity, GR and QFT are usefully (and possibly fully) compatible. We get good results in astrophysics from semi-clasical gravity, where the classical curved spacetime of General Relativity couples with the expectation value of QFT matter (i.e., we average out some quantum weirdness and justify this by the weak gravitational effects of the "lumpy" weirdness being practically impossible to measure; superpositions and ultra-high-energy/ultra-high-denisty systems might be too lumpy).
We also get good results from perturbative quantum gravity and canonical quantum gravity, for example. Neither of these latter two is really classical General Relativity so they can deal with the gravitation of superposed matter (otherwise they give for all practical purposes the same answers as semiclassical gravity). These approaches do not work in strong gravity, however. Essentially they become calculationally intractable or they crash into unresolved problems splitting spacetime into space and time (in order to do time-dependent quantum mechanics).
> We are approaching lab-testability, with results from sensitive accelerometers allowed to point at tiny superposed masses.
Do you happen to know of any promising upcoming experiments in particular? Or any groups who are at the forefront of such research endeavors?
Do you happen to know of any promising upcoming experiments in particular? Or any groups who are at the forefront of such research endeavors?
I can't say anything about promising. The hard part seems to be building an apparatus that works, and I don't know how to do that. I hear of short-lived superpositions with increasing amus or daltons but I can't deal with those units without the newest SI prefixes (fun facts, 666 Yamu is a bit more than 1 kg; and there is maybe about 0.666 YMsun locked up in observable galaxy clusters).
HN user ISL <https://news.ycombinator.com/user?id=ISL> is probably au fait with recent quantum gravimetry experiments.
The Müller group at UC Berkeley came to my mind. They did a recent paper <https://arxiv.org/abs/2210.07289>.
Gavin Morley's group at Warwick University is doing work in the area <https://warwick.ac.uk/fac/sci/physics/staff/academic/gmorley...>. He has what looks like a useful bibliography on the subject too: <https://warwick.ac.uk/fac/sci/physics/staff/academic/gmorley...>.
Finally, while not really related to your question (except that greater-precision gravimetry is likely to mean smaller superposed masses are useful), https://www.nature.com/articles/s41586-021-04315-3 is extremely cool, and I wish it could be sent back into the heyday of https://en.wikipedia.org/wiki/Time_Team . (ETA: Müller's group, similarly, https://arxiv.org/abs/1904.09084 .)
HN user ISL <https://news.ycombinator.com/user?id=ISL> is probably au fait with recent quantum gravimetry experiments.
The Müller group at UC Berkeley came to my mind. They did a recent paper <https://arxiv.org/abs/2210.07289>.
Gavin Morley's group at Warwick University is doing work in the area <https://warwick.ac.uk/fac/sci/physics/staff/academic/gmorley...>. He has what looks like a useful bibliography on the subject too: <https://warwick.ac.uk/fac/sci/physics/staff/academic/gmorley...>.
Finally, while not really related to your question (except that greater-precision gravimetry is likely to mean smaller superposed masses are useful), https://www.nature.com/articles/s41586-021-04315-3 is extremely cool, and I wish it could be sent back into the heyday of https://en.wikipedia.org/wiki/Time_Team . (ETA: Müller's group, similarly, https://arxiv.org/abs/1904.09084 .)
Thanks so much!
> We do know that mathematical frameworks cannot be at the same time totally complete and internally consistent.
I take it you're referencing Godel's theorems here, but "consistent" and "complete" have rather technical (and somewhat limited) meanings within that context, so it's not clear to me how they'd usefully map onto the potential relationship between QM and GR?
I take it you're referencing Godel's theorems here, but "consistent" and "complete" have rather technical (and somewhat limited) meanings within that context, so it's not clear to me how they'd usefully map onto the potential relationship between QM and GR?
That's a very good point. In particular, "complete" refers to the ability of the mathematical-logical system to prove every statement that is true within that system, in terms of the system.
This property is completely irrelevant to a theory like QM or GR - it is only relevant for a system that aims to be a universal foundation for mathematics (a formal language in which any mathematical statement whatsoever could be precisely formally encoded, and then proven or disproven).
This property is completely irrelevant to a theory like QM or GR - it is only relevant for a system that aims to be a universal foundation for mathematics (a formal language in which any mathematical statement whatsoever could be precisely formally encoded, and then proven or disproven).
> We do know that mathematical frameworks cannot be at the same time totally complete and internally consistent.
It would be troubling to think that physical reality was inconsistent.
It would be troubling to think that physical reality was inconsistent.
Mathematical completeness is a mathematical concern and is irrelevant for physics, because physics and mathematics have different notions of existence.
> All my life, they've been hawking string theory
I see what you did there.
Also, Sabine Hossenfelder was trained as a particle physicist and she doesn't like it either. She explains why it's like that and how it's bad and what they should be doing instead (like actively trying to reconcile the contradictory theories of gravity and quantum mechanics). She has changed career to professional youtuber https://en.wikipedia.org/wiki/Sabine_Hossenfelder
I see what you did there.
Also, Sabine Hossenfelder was trained as a particle physicist and she doesn't like it either. She explains why it's like that and how it's bad and what they should be doing instead (like actively trying to reconcile the contradictory theories of gravity and quantum mechanics). She has changed career to professional youtuber https://en.wikipedia.org/wiki/Sabine_Hossenfelder
> like actively trying to reconcile the contradictory theories of gravity and quantum mechanics
Isn't that exactly what string theory is trying to do?
Isn't that exactly what string theory is trying to do?
She's mainly against research that tries to achieve naturalness for its own sake https://en.wikipedia.org/wiki/Naturalness_(physics)
If someone is actually trying to get to the bottom of some contradictions in physics experiments I don't think she would be against this. I think she has observed that string theory has failed at it for so long and maybe some other methods can get a chance for funding instead of spending a hundred billion dollars on string theory and ten thousand dollars on other methods.
If someone is actually trying to get to the bottom of some contradictions in physics experiments I don't think she would be against this. I think she has observed that string theory has failed at it for so long and maybe some other methods can get a chance for funding instead of spending a hundred billion dollars on string theory and ten thousand dollars on other methods.
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It's cheap. A physicist I work with says it was a cheap way to have clout in the 80's in a physics department. Fundamentally, paying for a couple of people to do math on paper all day is a lot cheaper than doing what they do at cern.
String theory is seductive as it is almost a natural progression to go from point-like particles to strings with different patterns of vibration. Also, it seems to have a natural handling of gravity and so promises the holy grail of unification. It's almost like a mathematical formula that's too beautiful to not be true (though there's plenty of examples of beautiful maths that fails).
What I find curious is the “observed” properties of the whirlwinds within each and every proton & neutron are so phenomenally complex, I would not be surprised at all if the mathematical abstractions of strings represent another quantum ecosystem we may never be able to observe
And here I thought Hawking was a quantum field theorist.
Science progresses one funeral at a time.
Pretty much. We can't get past the big wigs until the big wigs are no longer enforcing beliefs that make little sense.
What causes them to do this?
What causes dictators to cling to power?
What causes political parties to prioritize their donors over their constituents?
What causes corporations to disregard the safety and health of the public if the worst they'll face is a fine for negligence?
These questions, while superficially unrelated, all point to the same underlying mechanism in the nature of societies.
What causes political parties to prioritize their donors over their constituents?
What causes corporations to disregard the safety and health of the public if the worst they'll face is a fine for negligence?
These questions, while superficially unrelated, all point to the same underlying mechanism in the nature of societies.
A structure build painfully to get money. With enough time each scientist learns to became an entertainer or a politic.
Being apes, I guess.
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Sunk cost fallacy.
A lot of people have spent a lot of their time developing this theory
A lot of people have spent a lot of their time developing this theory
And I suppose given that it was exciting in the 1980s, these are the people in positions of power at the moment.
Tenure has its pluses and minuses. If a string theorist has tenure, they’re going to be string theorizing for a very long time. Sunk cost fallacy plays a role but so does specialization. If you’re leading string theorist and you walk away from string theory, what are you? A mathematician?
If you adjust your priors in response to data and end up walking away from a faulty theory, I think the term is “scientist”. It sounds like the problem from your perspective is they identify themselves as “string theorists” first and “scientists” second.
And yet, “science advances one funeral at a time” probably because scientists are people.
Until now, there hasn’t been any data around string theory whatsoever. It’s been a purely mathematical exercise without even a hint of a possible experiment to test it.
So walking away from string theory years ago, in my mind, would make you a mathematician.
So walking away from string theory years ago, in my mind, would make you a mathematician.
I agree, it’s impossible to completely divorce humans of their biases. One way is to create a system of diversity in rival ideas. So while a scientist is a noun, science should be viewed as a verb. The person may be biased, but the goal is that the process is not. (Still easier said than done).
I didn’t really intend to convey the idea that I thought bias was the major factor. As a practical matter, if you’re an expert in a field and your foundational theories are seriously challenged, it challenges your foundation as an expert.
It’s fun to talk about scientists as these staunch defenders of their theories and say “science advances one funeral at a time” but the reality of the situation is that sometimes scientists are faced with the realization that their entire life’s work is in ruins. It’s hard to imagine a more severe test of character than that. Harder still to imagine how one might pick up the pieces and move on to something else and still be able to contribute to science in a meaningful way.
It’s fun to talk about scientists as these staunch defenders of their theories and say “science advances one funeral at a time” but the reality of the situation is that sometimes scientists are faced with the realization that their entire life’s work is in ruins. It’s hard to imagine a more severe test of character than that. Harder still to imagine how one might pick up the pieces and move on to something else and still be able to contribute to science in a meaningful way.
I can’t stop thinking about one the greatest scientific discoveries in this context.
Kepler was convinced the planetary orbits around the sun were circular and could be described with the five Platonic solids. His theory was testable, and when he measured it against observation, it failed. He could have persisted, modified his theory, and continued on the wrong path, but instead, he discarded his theory and discovered elliptical orbits with his three laws of planetary motion.
Kepler was a scientist.
Kepler was convinced the planetary orbits around the sun were circular and could be described with the five Platonic solids. His theory was testable, and when he measured it against observation, it failed. He could have persisted, modified his theory, and continued on the wrong path, but instead, he discarded his theory and discovered elliptical orbits with his three laws of planetary motion.
Kepler was a scientist.
No one has come up with something demonstrably better yet.
Most of the New Scientist is breathless articles. It's borderline science-fiction hooking in the very latest of publications
pun intended? :D
Article states that solitions are not black holes but only seem like black holes from a distance. Also they are hypothesized from string theory but haven’t ever been seen, probably because they’d appear the same as black holes except up close?
Title should be updated to something like: “A theorized defect in space time that appears to be a black hole”
Title should be updated to something like: “A theorized defect in space time that appears to be a black hole”
It's a really thin article. It fails to say how "topological solitons" are different from wave-mechanical solitons, nor does it explain why they look like black holes, or why they lack an event horizon.
I'm routinely disappointed with phys.org. It's pop-sci with the "-sci" component reduced to a remnant.
I'm routinely disappointed with phys.org. It's pop-sci with the "-sci" component reduced to a remnant.
100% agree. It does link to an actual paper which is a step up from blogspam
https://link.aps.org/doi/10.1103/PhysRevD.107.084042
https://link.aps.org/doi/10.1103/PhysRevD.107.084042
For some reason it really irks me that they are using the word defect. It's like they forgot that the rules/model we set follow what happens in reality. If there is a defect, it's not in spacetime, it's in our understanding.
If your spacetime contains black holes you may be entitled to compensation from the manufacturer. Please retain this notice and your receipt. Known in the state of California to cause spaghettification. Offer not valid in worldlines crossing the event horizon.
It's a technical term in crystallography/solid state physics as well.
https://en.wikipedia.org/wiki/Crystallographic_defect
https://en.wikipedia.org/wiki/Crystallographic_defect
Think of it as an abnormality in spacetime.
"Since we know that infinite densities cannot actually happen in the universe"
Because we exist. If infinite density existed, our atoms would be in there.
Not true. For example we could be surrounded by a sphere of uniform infinite density, in which case our atoms wouldn't be pulled in either direction.
For those of us like myself who are terribly naive, why wouldn't that just cause all of the atoms to be torn apart?
Unless the sphere were infinitely far away, only the center point would be in balance, and everything else would be immediately sucked to the edge of the sphere. If the sphere's radius was infinite, that might explain the expansion of the universe itself, but not the presence of infinite density within the universe itself.
Unless the sphere were infinitely far away, only the center point would be in balance, and everything else would be immediately sucked to the edge of the sphere. If the sphere's radius was infinite, that might explain the expansion of the universe itself, but not the presence of infinite density within the universe itself.
When you do the math for gravity inside a shell of material, the quadratic falloff exactly counteracts the distances and the total pull is exactly zero.
https://en.wikipedia.org/wiki/Shell_theorem
https://en.wikipedia.org/wiki/Shell_theorem
> Unless the sphere were infinitely far away, only the center point would be in balance
This is false. https://en.wikipedia.org/wiki/Divergence_theorem
This is false. https://en.wikipedia.org/wiki/Divergence_theorem
If the sphere had infinite density, wouldn't that mean that every atom in the universe would be inside? So how could our atoms be outside?
Why? At a distance, gravity doesn't really care about density, only mass.
An infinitely dense object would shred anything it touches by its infinitely high tidal force, but there's only a limited amount of material it can touch within a given time and the Universe is not infinitely old.
An infinitely dense object would shred anything it touches by its infinitely high tidal force, but there's only a limited amount of material it can touch within a given time and the Universe is not infinitely old.
> but there's only a limited amount of material it can touch within a given time and the Universe is not infinitely old
Okay, to be precise something like that can't have existed in the observable universe (at the time we observe), but could exist in a distant bubble that's expanding at the speed of light.
Okay, to be precise something like that can't have existed in the observable universe (at the time we observe), but could exist in a distant bubble that's expanding at the speed of light.
>the Universe is not infinitely old
You don't know that. Claiming that there is a start to the universe is an absurd, religious ex nihilo argument.
You don't know that. Claiming that there is a start to the universe is an absurd, religious ex nihilo argument.
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Compare the infinite set of integers to the infinite set of reals. Infinite sets can be subsets of much larger infinite sets.
Also, density is mass divided by volume. You have two variables to play with.
But all of this detracts from the notion that infinity and singularity may have no physical analog. They're mathematical constructs.
Also, density is mass divided by volume. You have two variables to play with.
But all of this detracts from the notion that infinity and singularity may have no physical analog. They're mathematical constructs.
How does that follow?
There would be infinite m/v there, and finite everywhere without infinite density, so literally every single random draw of a single mass-unit would be in an area of infinite density, or so goes the idea.
That's presupposing that the mass portion of m/v is infinite, which, from our understanding of black holes, we have no reason to believe. Pathological local densities tell you nothing about the mass distribution of the universe precisely because they're so pathological.
Every theory has a domain of applicability, determined by tests within that domain. I don't think its reasonable to assume that the domain of applicability of any our theories extends to various infinities.
(This is not sarcastic)
How do we know we aren't?
Well, there have been thoughts that we are living in a blackhole from another universe. So there's that.
These questions aren't answerable at the moment. It's all just speculation.
These questions aren't answerable at the moment. It's all just speculation.
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Yeah, I stopped reading when i got to that sentence
Infinity and singularity are mathematical constructs. They look great on paper, but we don't know if they have actual physical analogs. It could be that relativity and the physics around black holes, the big bang, etc. are wrong.
> Infinity and singularity are mathematical...
THIS. That I've seen, the [astro]physicists are confident that there are no actual physical infinities nor singularities. With the public, they'll use those terms for situations "approaching" infinities and singularities. But in private, they're busy using all sorts of clever mathematics and calculations and arguments to avoid having any infinity or singularity occur, even on paper.
A very basic example: https://en.wikipedia.org/wiki/Dirac_delta_function#Motivatio...
THIS. That I've seen, the [astro]physicists are confident that there are no actual physical infinities nor singularities. With the public, they'll use those terms for situations "approaching" infinities and singularities. But in private, they're busy using all sorts of clever mathematics and calculations and arguments to avoid having any infinity or singularity occur, even on paper.
A very basic example: https://en.wikipedia.org/wiki/Dirac_delta_function#Motivatio...
Are you saying that we have evidence that universe is not infinite?
Could be true that there is nothing with infinite density. But it is certainly not known with certainty, so the statement is horribly wrong.
>It could be that relativity and the physics around black holes, the big bang, etc. are wrong.
Of course, that's almost certain
>It could be that relativity and the physics around black holes, the big bang, etc. are wrong.
Of course, that's almost certain
The article has some pop-science feel to it:
> But we do have candidates, including string theory.
Oh no, you mean the theory that physicists say we see no evidence of at all? Great, if that is the basis, ... lets see what follows.
> In string theory all the particles of the universe are actually microscopic vibrating loops of string. In order to support the wide variety of particles and forces that we observe in the universe, these strings can't just vibrate in our three spatial dimensions. Instead, there have to be extra spatial dimensions that are curled up on themselves into manifolds so small that they escape everyday notice and experimentation.
Right, it would most definitely escape the experiments I have in my garage ... Who talks about "everyday experimentation" when talking about string theory? I mean, in "everyday experimentation" we don't even see atoms and most of us in their "everyday experimentation" do not even see molecules. Really makes you wonder what "everyday experimentation" they are going on about.
> That exotic structure in spacetime gave a team of researchers the tools they needed to identify a new class of object, something that they call a topological soliton. In their analysis they found that these topological solitons are stable defects in space-time itself. They require no matter or other forces to exist—they are as natural to the fabric of space-time as cracks in ice. The research is published in the journal Physical Review D.
But cracks in ice do consist of something: Usually air that fills the gaps. And even if we put ice in perfect vacuum somehow, there is still space between the parts of the ice. It is not like there is nothing. Seems like a bad analogy. At least they would have to go into what "fills" the gaps like with ice. Some space-time-vacuum?
On top of that, the article tries to explain things by using even more in my vocabulary undefined terms like "soliton".
> Because they are objects of extreme space-time [...]
Ah, they are "of extreme space-time"! Now I know ... nothing.
I don't feel like I understood anything valuable, but more like reading a sci-fi novel. Although, sometimes sci-fi novels do make more sense in their own invented universe than this article. Was this article perhaps generated by some language model?
> But we do have candidates, including string theory.
Oh no, you mean the theory that physicists say we see no evidence of at all? Great, if that is the basis, ... lets see what follows.
> In string theory all the particles of the universe are actually microscopic vibrating loops of string. In order to support the wide variety of particles and forces that we observe in the universe, these strings can't just vibrate in our three spatial dimensions. Instead, there have to be extra spatial dimensions that are curled up on themselves into manifolds so small that they escape everyday notice and experimentation.
Right, it would most definitely escape the experiments I have in my garage ... Who talks about "everyday experimentation" when talking about string theory? I mean, in "everyday experimentation" we don't even see atoms and most of us in their "everyday experimentation" do not even see molecules. Really makes you wonder what "everyday experimentation" they are going on about.
> That exotic structure in spacetime gave a team of researchers the tools they needed to identify a new class of object, something that they call a topological soliton. In their analysis they found that these topological solitons are stable defects in space-time itself. They require no matter or other forces to exist—they are as natural to the fabric of space-time as cracks in ice. The research is published in the journal Physical Review D.
But cracks in ice do consist of something: Usually air that fills the gaps. And even if we put ice in perfect vacuum somehow, there is still space between the parts of the ice. It is not like there is nothing. Seems like a bad analogy. At least they would have to go into what "fills" the gaps like with ice. Some space-time-vacuum?
On top of that, the article tries to explain things by using even more in my vocabulary undefined terms like "soliton".
> Because they are objects of extreme space-time [...]
Ah, they are "of extreme space-time"! Now I know ... nothing.
I don't feel like I understood anything valuable, but more like reading a sci-fi novel. Although, sometimes sci-fi novels do make more sense in their own invented universe than this article. Was this article perhaps generated by some language model?
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This is pretty badly written. Something looks like a black hole but doesn't have an event horizon? Isn't a black hole nothing but an event horizon to an outward observer? How does it look like a black hole if it doesn't bend light with gravity?
You could hold it in your hand "if you survive the encounter"? So you can't hold it in your hand? *What would happen to you if you touched it?"
You could hold it in your hand "if you survive the encounter"? So you can't hold it in your hand? *What would happen to you if you touched it?"
The Topological solitons would appear exactly like predicted black holes from a distance, with shadows, light rings, and gravitational wave signatures. It is not about the event horizon. It just telling you we would see them as black holes if we look to them from some distance. Remember that cannot observe the event horizon directly, the famous gravitational waves discovery in 2015 is an example of indirect black holes observation
The other important difference is that they could form without mass which is not the case with black holes. So I am not sure that I would agree with you.
The other important difference is that they could form without mass which is not the case with black holes. So I am not sure that I would agree with you.
So if they form without mass, why would they bend light like black holes? If they don't bend light, then it seems to me that they would not really appear as black holes.
I find a lot of posts from phys.org to be highly editorialized, with ambiguous and sensational headlines.
It is a low quality source, imo
It is a low quality source, imo
I think implication is that there's a spectrum of related phenomena (and that "black holes" with an event horizon are an extreme case)
Collapsar asymptotically approaches state of black hole as inverse exponent of time. Feel free to detect such small difference.
"But we do have candidates, including string theory. In string theory all the particles of the universe are actually microscopic vibrating loops of string."
Actually string. Brilliant exposition this.
Actually string. Brilliant exposition this.
(I'm not a physicist, but) from the paper:
> All together, the Schwarzschild topological solitons have scattering properties very similar to Schwarzschild black holes. The main difference will be a residual faded glow that emerges from inside the would-be shadow.
So basically, things fall in, bounce around, and come back out (albeit scrambled)? Seems intuitively more reasonable than singularities?
> All together, the Schwarzschild topological solitons have scattering properties very similar to Schwarzschild black holes. The main difference will be a residual faded glow that emerges from inside the would-be shadow.
So basically, things fall in, bounce around, and come back out (albeit scrambled)? Seems intuitively more reasonable than singularities?
Something I was always wondering about black holes:
Does there really have to be a singularity? If I understand relativity correctly, time slows down as mass increases. Couldn't this slowdown affect the contraction so that it never can actually reach an "actual" singularity point?
Does there really have to be a singularity? If I understand relativity correctly, time slows down as mass increases. Couldn't this slowdown affect the contraction so that it never can actually reach an "actual" singularity point?
This is actually a pretty tricky question. The standard black hole solutions are highly idealized in order to make them tractable. In particular, they have a lot more symmetry in time than you would expect a black hole to have. Actually forming a black hole from realistically distributed matter undergoing gravitational collapse is a more complicated problem to talk about in GR. So you pose a genuinely interesting question.
I think the singularity theorems address it however: https://en.wikipedia.org/wiki/Penrose%E2%80%93Hawking_singul...
The basic idea is that singularities are a very general feature of general relativity, not confined to specific solutions to the field equations but sort of inevitable for a large number of initial conditions. So while the standard black hole solutions are highly idealized, we have good theoretical reason to believe that singularities exist in non-trivial solutions to the Einstein Field Equations.
I think the singularity theorems address it however: https://en.wikipedia.org/wiki/Penrose%E2%80%93Hawking_singul...
The basic idea is that singularities are a very general feature of general relativity, not confined to specific solutions to the field equations but sort of inevitable for a large number of initial conditions. So while the standard black hole solutions are highly idealized, we have good theoretical reason to believe that singularities exist in non-trivial solutions to the Einstein Field Equations.
You're confused by mathematical terminology. Since mathematics is ignorant about time, "inevitable" is a synonym to "exists" there, because mathematics can easily assume infinite time passed by usual induction, but in physics time isn't negligible. Even in terms of mathematics you need to believe in actual infinity to believe that formation of a black hole completes.
https://youtu.be/351JCOvKcYw
There are a number of theories on black holes not being singularities.
PBS space time goes into a few of them
There are a number of theories on black holes not being singularities.
PBS space time goes into a few of them
Time slows down from the perspective of an outside observer.
From the perspective of a particle falling into a black hole, the singularity will be reached in finite time.
From the perspective of a particle falling into a black hole, the singularity will be reached in finite time.
That's true but from our perspective this state won't be reached anywhere in the universe -- so there can't be any singularity from our perspective?
And you don't actually see a singularity, you see only an event horizon, and more accurately, the matter trapped orbiting the event horizon.
From the perspective of a particle falling into a black hole, it will be burned by Hawking radiation even before it reaches event horizon.
Well, I don't think any physicist believes that an actual singularity exists in the center of a black hole in physical reality. The mathematics of GR actually do predict a singularity, but this is typically viewed as a limitation of the theory, not an actual physical object.
Instead, most physicists believe that a theory of quantum gravity (a theory which accounts for gravitational interactions between quantum particles in general) would slightly modify the equations of GR to arrive at a finite solution for the interior of the black hole. Of course, such a theory eludes us so far.
Instead, most physicists believe that a theory of quantum gravity (a theory which accounts for gravitational interactions between quantum particles in general) would slightly modify the equations of GR to arrive at a finite solution for the interior of the black hole. Of course, such a theory eludes us so far.
You're right that from an observer outside of the event horizon, a black hole hasn't happened yet (and never will).
There's a fun thought experiment to be had here. We're all familiar with the concept of "going back in time". Even though the math doesn't check out and our imaginations of what that looks like are totally impossible, it's something we can (and often like to) imagine.
Now, what happens when you move backwards not in time, but in space? And I don't mean changing your direction 180 degrees, but moving backwards within the confines of space. So, if your present coordinates are (X, Y, Z), you move "backwards in space" 5 meters such that no matter what your direction of motion, if you move "forwards in space" by 5 meters you end up right where you started, at (X, Y, Z). You're basically creating an inverted bubble around (X, Y, Z) and making it so that all possible paths lead "outward" toward (X, Y, Z). Any point that is A meters away from (X, Y, Z) is actually A+5 meters away from you.
In a 2-D world this can be modeled with a third dimension. We all live on a flat plain but someone on a 5-meter hill is actually farther away than their 2-dimensional coordinates would imply. You're able to move away from a point in 2-D space without changing your 2-D coordinates (because you're actually moving in another dimension).
For 3D space, this extra dimension is time itself. The only way to move "backwards" in a comprehensible sense within 3 dimensions is by moving backwards within time. So, I'm not actually moving 5 meters "backwards" within space but moving backwards in time such that I will appear at (X, Y, Z) in 3-D space at precisely the same time it would take me to move forward 5 meters. I'm blipped out of space until such time has passed to allow me to reach (X, Y, Z) again, so I've successfully "moved backwards in space" by 5 meters. So, if I move "backwards in space", then I'm really putting (X, Y, Z) in front of me time-wise.
So, what's the center of a black hole? We can imagine it has coordinates (X, Y, Z). And let's pretend it's actually moving backwards into space, which we now conceptualize as putting its "present" coordinates forward in time. But, it's actually moving backwards in space (i.e. moving universally farther from every other point in space) at a speed faster than we can travel. The center of the black hole is always in the future and even as we move closer to the center, it's still infinitely far away. As we cross the event horizon, we ride the current and start moving faster than the universal speed limit, cutting ourselves off from ever interacting with the outside universe again. However, we're still never going to be able to reach the center, and indeed the center of the black hole has still not happened from our point of reference (and still never will).
There's a fun thought experiment to be had here. We're all familiar with the concept of "going back in time". Even though the math doesn't check out and our imaginations of what that looks like are totally impossible, it's something we can (and often like to) imagine.
Now, what happens when you move backwards not in time, but in space? And I don't mean changing your direction 180 degrees, but moving backwards within the confines of space. So, if your present coordinates are (X, Y, Z), you move "backwards in space" 5 meters such that no matter what your direction of motion, if you move "forwards in space" by 5 meters you end up right where you started, at (X, Y, Z). You're basically creating an inverted bubble around (X, Y, Z) and making it so that all possible paths lead "outward" toward (X, Y, Z). Any point that is A meters away from (X, Y, Z) is actually A+5 meters away from you.
In a 2-D world this can be modeled with a third dimension. We all live on a flat plain but someone on a 5-meter hill is actually farther away than their 2-dimensional coordinates would imply. You're able to move away from a point in 2-D space without changing your 2-D coordinates (because you're actually moving in another dimension).
For 3D space, this extra dimension is time itself. The only way to move "backwards" in a comprehensible sense within 3 dimensions is by moving backwards within time. So, I'm not actually moving 5 meters "backwards" within space but moving backwards in time such that I will appear at (X, Y, Z) in 3-D space at precisely the same time it would take me to move forward 5 meters. I'm blipped out of space until such time has passed to allow me to reach (X, Y, Z) again, so I've successfully "moved backwards in space" by 5 meters. So, if I move "backwards in space", then I'm really putting (X, Y, Z) in front of me time-wise.
So, what's the center of a black hole? We can imagine it has coordinates (X, Y, Z). And let's pretend it's actually moving backwards into space, which we now conceptualize as putting its "present" coordinates forward in time. But, it's actually moving backwards in space (i.e. moving universally farther from every other point in space) at a speed faster than we can travel. The center of the black hole is always in the future and even as we move closer to the center, it's still infinitely far away. As we cross the event horizon, we ride the current and start moving faster than the universal speed limit, cutting ourselves off from ever interacting with the outside universe again. However, we're still never going to be able to reach the center, and indeed the center of the black hole has still not happened from our point of reference (and still never will).
The actual article linked has a better title and the abstract is probably sufficient for anyone interested in the subject: https://link.aps.org/doi/10.1103/PhysRevD.107.084042
The given title is just flat out misleading.
The given title is just flat out misleading.
To the outside observer, modern particle physics looks like a cross between religion and Emperor Has No Clothes. Much of what constitutes a successful researcher and institution is not practical result (or even tangible or reproducible), but instead is political.
I'm pretty sure that you walked out with no clothes in the scientific community, people would be happy to point out you have no clothes. People can make names for themselves poking holes in other's theories. Hell, Einstein tried to do that with quantum mechanics without much success.
I guess, in that sense it's political. But the politics here is to try to bring about rational reasoning. And eventually, quantum mechanics won, not because it was the most reasonable theory, (it's not and who would design a universe this way?), but it has the most amount of experimental evidence to back it up.
I guess, in that sense it's political. But the politics here is to try to bring about rational reasoning. And eventually, quantum mechanics won, not because it was the most reasonable theory, (it's not and who would design a universe this way?), but it has the most amount of experimental evidence to back it up.
I don't think most physicists in this area think the Standard Model is "correct" in the sense of actually describing what makes the universe tick. They mostly recognize it as a set of curves that are extremely well fitted to experimental data, up to a point (at which point it fails completely and necessitates a switch to another model).
I’m not very familiar with modern particle physics. Can you explain what you mean by this?
I'm not too current. Last time I looked at this was 2016. My take is: Many experiments are conducted on "unique" equipment which is inaccessible to outsiders. This makes experiments irreproducible in the classical sense. For example, the CERN particle accelerator is the largest in the world, no other similar facilities exist. Much of the research done is on such facilities.
2. Scientists in the field agree upon a "standard model", which predicts certain phenomena but not others. For the other phenomena, they use a different model, which is incompatible or not reconciled with the first model. Both of these models resemble over-fitted models that describe but don't explain. There is no beautiful, elegant combination of geometry and mathematics to discover the underlying meaning of the universe there.
3. Experiment results are highly processed by researchers and constitute terabytes or petabytes of data which is easy to manipulate to suit a researcher's opinion or political ends. Lots of noise and very little discernible signal.
4. Recent experiments don't seem to be yielding new, novel, interesting or viable lines of thinking.
> There is no beautiful, elegant combination of geometry and mathematics to discover the underlying meaning of the universe there.
This is not a fair criticism. Its not like some of the smartest groups of people alive have not tried for over half a century. Nobody has the slightest real clue on a way out. What else to do, except to constantly try and break the model somehow?
This is not a fair criticism. Its not like some of the smartest groups of people alive have not tried for over half a century. Nobody has the slightest real clue on a way out. What else to do, except to constantly try and break the model somehow?
There's a cult around string theory, where despite it not producing a single testable hypothesis in its multi-decade dominance, it maintains its dominance as an orthodoxy, sucking up most of the research grants. Speaking out against string theory in the particle physics circles of academia gets you branded a heretic and outcast, potentially costing you a career in particle physics.
We cannot, and should not come to terms with the prospect that the universe's complexities may be totally out of our reach. Best to keep trying in one way or another. Unfortunately, my comments are not constructive, I don't have a better avenue to suggest. All that I can tell is that phenomenon on human scale are easier to grasp. The bigger or smaller you get, the harder it is to observe.
If I am not completely wrong, this headline has nothing to do with the linked article. The article is about "topological solitons" that - according to the article - look "to outside observers" like black holes.
I think the headline just doesn't do enough work specifying how unlikely this is. The article otherwise seems to match.
We are "outside observers", correct? So black holes we see "might" (theoretically, in an unproven and maybe unprovable system of physics) be defects in spacetime.
We are "outside observers", correct? So black holes we see "might" (theoretically, in an unproven and maybe unprovable system of physics) be defects in spacetime.
I share your understanding but when the article does not even mention that possibility, a link text seems to be an odd place to make such a claim.
I don't understand how you didn't take that away from the article... it was clear to me what it was saying.
Can you give me some pointers where you read this?
I mean, at the end they even write "It's only once you got close would you realize that you are not looking at a black hole." I take from that that they are aware that black holes are different from topological solitons. And I read at no place that they consider black holes actually being topologial solitons.
So, when the authors think that those two things are different and they classify solitons as "defects in spacetime", wouldn't this directly contradict the headline "Black holes might be defects in spacetime"?
I would be glad if you showed me where my reasoning is wrong.
I mean, at the end they even write "It's only once you got close would you realize that you are not looking at a black hole." I take from that that they are aware that black holes are different from topological solitons. And I read at no place that they consider black holes actually being topologial solitons.
So, when the authors think that those two things are different and they classify solitons as "defects in spacetime", wouldn't this directly contradict the headline "Black holes might be defects in spacetime"?
I would be glad if you showed me where my reasoning is wrong.
Maybe the disconnect is that there's an implicit "[What we see as] Black holes might be defects in spacetime" in front of the headline.
We can't get close to black holes, maybe ever but certainly not currently, so the difference between what the article is saying and how you're reading it is a bit philosophical IMO.
The article glossed over it a bit, but from the sounds of it, every observation we know of from our position (and current technology level) would match.
We can't get close to black holes, maybe ever but certainly not currently, so the difference between what the article is saying and how you're reading it is a bit philosophical IMO.
The article glossed over it a bit, but from the sounds of it, every observation we know of from our position (and current technology level) would match.
I see. My reading was that black holes don't exist. That there is an alternative, topological explanation for the phenomena we've observed and so far classified as black holes.
Only if you don’t look at it through the lens of selling advertisements based on impressions.
The phys.org article isn't worth spending time on. It's better to read the original arxiv paper that @supermatou linked in a peer thread.
> Since we know that infinite densities cannot actually happen in the universe, we take this as a sign that Einstein's theory is incomplete. But after nearly a century of searching for extensions, we have not yet confirmed a better theory of gravity.
Is it really true that infinite densities are impossible? Consider a function that measures the volume of an object with respect to time, say V(t). If the force of gravity is strong enough to overcome every other force, wouldn't V(t) approach 0 as t goes to infinity? Isn't that essentially having infinite density?
Is it really true that infinite densities are impossible? Consider a function that measures the volume of an object with respect to time, say V(t). If the force of gravity is strong enough to overcome every other force, wouldn't V(t) approach 0 as t goes to infinity? Isn't that essentially having infinite density?
It's what you would consider a mathematical limit. The limit is never actually reached. V(t) becomes vanishingly small, to the point that time effectively stands still, but mathematically it should still always remain a non-zero value, and thus density at the singularity isn't infinite. Anyway, at that point measuring things becomes exceedingly difficult and abstract.
You just arrived to infinite density using a concept of infinite time. Now you need to justify existence of infinite time.
The argument is that there is no infinite amount of _anything_. That is a fictional concept of 'too many parts to count'.
The argument is that there is no infinite amount of _anything_. That is a fictional concept of 'too many parts to count'.
I guess my point is that there isn't really an infinite quantity in mathematics, either. What we think about as "infinity" usually involves some type of unbounded limit.
You’ve just defined gravitational collapse.
The real question is: is the volume infinitely compressible or is there something that would eventually oppose enough counterforce to halt the collapse?
The real question is: is the volume infinitely compressible or is there something that would eventually oppose enough counterforce to halt the collapse?
the infinite density is actually after a finite amount of time, since black hole collapse has already happened, which is why it matters that they are predicted to have infinitely dense points at their centers. The key is that this isn't a limit, GR seems to expect that there are infinitely dense objects just floating around breaking space-time.
I’m sick of the QC for spacetime. Back when I was a kid, spacetime was highly reliable. Glitches in the matrix or continuum were almost nonexistent. Sad that you Gen Z-ers can’t keep it together.
Wasn't string theory very thoroughly "dis-proven" (as in you have to go through absurd hoops to make it still work which indicates it most likely is not the truth at all, even though you can not completely rule it out because some concepts are very resistant to be proven to not exist).
Hmm? I've not heard of any such thing. The main problem I've heard is that it's hard to come up with a test that will confirm or reject the hypothesis, let alone distinguish between the different variations.
I just was interested enough to look up what’s the nearest known black hole to Earth, and it’s Gaia BH1 which is 1560 light years away from us…can I still get my hope up that during my lifetime I can witness some significant breakthrough regarding our knowledge of black hole?
if AGI 2030 then presumably singularity shortly after at which point physics is immediately solved subject to the computational limits of the amount of energy available in our solar system (beyond which we start paying speed of light delays to move compute to energy dense regions of the galaxy, unless warp drives are solved too).
Defect isn't the right word to use for something that is part of a process that seems to play out in every instance we are aware of.
If every supernova above a certain size creates a black hole that's not a defect, it's an effect. If the center of every galaxy contains a black hole - how can that be a defect?
If every supernova above a certain size creates a black hole that's not a defect, it's an effect. If the center of every galaxy contains a black hole - how can that be a defect?
The actual paper (no paywall):
https://arxiv.org/pdf/2212.06837.pdf
I've been keeping my brain occupied on long drives by trying to come up with a theory of everything, because... why not?
My current pet hypothesis is that all fundamental particles are sort-of like tiny black holes, and that the space-time distortion caused by black holes is precisely the same thing that ordinary matter causes. All matter and energy are space-time distortions, which is why mass-energy bends space time. It's not a secondary effect, the bending is what everything is, not a property that things have. (This is essentially just a variant of Kaluza Klein theory, or others like it.)
Particles are kept apart by their spin, same as in well-established physics. Matter is still mostly empty space, same as normal.
In this toy model, neutron stars are like a boba tea, with the black holes of particles close-packed but still not touching.
When forced into forming a black hole, the event horizons of individual particles begins to merge, forming a "super-particle" that expands out. When fully-formed, the black hole is hairy, with a very dense packed crust of still-separate particles layered over a very lumpy surface, inside which there is... nothing. Not even space-time. The surface is where space-time ends.
It's like... imagine if we lived on a knitted jumper or a space-time like woven cloth and could only follow threads. If someone were to poke a hole in the weave with a finger, pushing aside the threads, then it would be meaningless to ask what threads are inside that hole. There aren't any. The "weave space" doesn't extend into the hole.
This simultaneously satisfies a long list of requirements gathered from modern physics:
1. Black hole formation is a gradual, continuous process at both microscopic and macroscopic scales. This model can start all the way down with the first pair of particles that got squished together and then can be extended all the way up to something the size of a star.
2. Black holes are hairy instead of smooth, satisfying thermodynamics and quantum information theory.
3. There's no paradox of what happens when you go past the event horizon. There's no singularity. The event horizon is a surface, essentially just a highly red-shifted neutron star. Hitting it is the same as hitting a neutron star. You do not go through. You get squished.
4. There's no need for complex maths to explain black hole evaporation. In a sense, black holes don't exist, they're just a very time-dilated neutron star, and their evaporation is just an ultra-slow-motion explosion of a neutron star.
5. A well-established theorem is that many properties of a black hole grow in proportion to their surface area (2D), not their volume (3D). This theory matches that. There is no volume, there's only the surface. The inside doesn't exist. When approaching from normal flat 3D space, space gradually becomes fractal (2.x dimensional), smoothly transitioning to a 2D space, which is the event horizon.
6. It is time-reversible. Seen backwards in time, "fingers" of 3D space invade into the event horizon, splitting it up into smaller and smaller chunks that bud off to form small, stable spheres that evaporate away. These are the particles that made up the black hole.
My current pet hypothesis is that all fundamental particles are sort-of like tiny black holes, and that the space-time distortion caused by black holes is precisely the same thing that ordinary matter causes. All matter and energy are space-time distortions, which is why mass-energy bends space time. It's not a secondary effect, the bending is what everything is, not a property that things have. (This is essentially just a variant of Kaluza Klein theory, or others like it.)
Particles are kept apart by their spin, same as in well-established physics. Matter is still mostly empty space, same as normal.
In this toy model, neutron stars are like a boba tea, with the black holes of particles close-packed but still not touching.
When forced into forming a black hole, the event horizons of individual particles begins to merge, forming a "super-particle" that expands out. When fully-formed, the black hole is hairy, with a very dense packed crust of still-separate particles layered over a very lumpy surface, inside which there is... nothing. Not even space-time. The surface is where space-time ends.
It's like... imagine if we lived on a knitted jumper or a space-time like woven cloth and could only follow threads. If someone were to poke a hole in the weave with a finger, pushing aside the threads, then it would be meaningless to ask what threads are inside that hole. There aren't any. The "weave space" doesn't extend into the hole.
This simultaneously satisfies a long list of requirements gathered from modern physics:
1. Black hole formation is a gradual, continuous process at both microscopic and macroscopic scales. This model can start all the way down with the first pair of particles that got squished together and then can be extended all the way up to something the size of a star.
2. Black holes are hairy instead of smooth, satisfying thermodynamics and quantum information theory.
3. There's no paradox of what happens when you go past the event horizon. There's no singularity. The event horizon is a surface, essentially just a highly red-shifted neutron star. Hitting it is the same as hitting a neutron star. You do not go through. You get squished.
4. There's no need for complex maths to explain black hole evaporation. In a sense, black holes don't exist, they're just a very time-dilated neutron star, and their evaporation is just an ultra-slow-motion explosion of a neutron star.
5. A well-established theorem is that many properties of a black hole grow in proportion to their surface area (2D), not their volume (3D). This theory matches that. There is no volume, there's only the surface. The inside doesn't exist. When approaching from normal flat 3D space, space gradually becomes fractal (2.x dimensional), smoothly transitioning to a 2D space, which is the event horizon.
6. It is time-reversible. Seen backwards in time, "fingers" of 3D space invade into the event horizon, splitting it up into smaller and smaller chunks that bud off to form small, stable spheres that evaporate away. These are the particles that made up the black hole.
While I understand these are just idle musings, you should note that this is failing to address the biggest problems that actually "require" a theory of everything.
Most importantly, it doesn't explain how quantum fields interact with a non-flat space-time. If you try to combine QM with the space-time-deforming characteristics of mass from GR, you quickly get infinities all over the place, which is obviously not what we observe.
Secondly, the object that you are calling a black hole is simply different from the object called a black hole in GR. That object, by definition, has a huge mass in an extremely small volume. All the other descriptions of it are derived properties of how GR says masses affect the structure of space-time. And it should also be noted that the event horizon of a black hole is much wider than the size of the object just before collapse, as far as I know - which sounds different from what your model would predict (but perhaps not?).
Most importantly, it doesn't explain how quantum fields interact with a non-flat space-time. If you try to combine QM with the space-time-deforming characteristics of mass from GR, you quickly get infinities all over the place, which is obviously not what we observe.
Secondly, the object that you are calling a black hole is simply different from the object called a black hole in GR. That object, by definition, has a huge mass in an extremely small volume. All the other descriptions of it are derived properties of how GR says masses affect the structure of space-time. And it should also be noted that the event horizon of a black hole is much wider than the size of the object just before collapse, as far as I know - which sounds different from what your model would predict (but perhaps not?).
Of course, the experimental observations that lead to QFT need to be accounted for, but not any specific mathematical model of QM. If two models like GR and QM disagree, we’ve got to drop one of the two. In my opinion it’s easier to keep GR, because I’ve never heard of a way to make QM particles produce spacetime curvature. (Conversely there is an entire zoo of theories that extend GR down to particles.)
Fundamentally, GR predicts that even an individual electron curves spacetime, and not just at “interstellar” distances. The effect ought to be continuous all the way down to the particle’s “surface” for a want of a better term.
It’s a consistency principle. Theories don’t end at the edge of the experimental benchtop or the surface of a planet. Either everything everywhere follows a rule or nothing does. The experimenter themselves is QM and GR, as is every particle and every planet.
In this sense, there are several ways to “add” most of QM theory to any extension of GR such as Kaluza Klein theory.
Most of these are some variants of the many worlds interpretation (MWI). This can reproduce superposition and the various “spooky action at a distance” effects without anything spooky actually being needed. Locality can be preserved and the hidden variables are in parallel universes. The mathematical issues with hidden variables also vanish if you assume the experimenter is also a part of the quantum experiment and not just standing outside of it like some sort of God looking down at space time from above.
My pet variant of MWI is to do away with the discrete, tree-like “splits” and assume that the many worlds form a continuum. Essentially this means that there are multiple time dimensions, smoothly splitting the universe at every instant. Hence observations are not special in any way, and can’t even be clearly identified. It’s just stuff that “goes on”.
The really hard part for any TOE is not QM! The brutally difficult aspect is explaining the three particle generations.
Very few theories even begin to explain that…
Fundamentally, GR predicts that even an individual electron curves spacetime, and not just at “interstellar” distances. The effect ought to be continuous all the way down to the particle’s “surface” for a want of a better term.
It’s a consistency principle. Theories don’t end at the edge of the experimental benchtop or the surface of a planet. Either everything everywhere follows a rule or nothing does. The experimenter themselves is QM and GR, as is every particle and every planet.
In this sense, there are several ways to “add” most of QM theory to any extension of GR such as Kaluza Klein theory.
Most of these are some variants of the many worlds interpretation (MWI). This can reproduce superposition and the various “spooky action at a distance” effects without anything spooky actually being needed. Locality can be preserved and the hidden variables are in parallel universes. The mathematical issues with hidden variables also vanish if you assume the experimenter is also a part of the quantum experiment and not just standing outside of it like some sort of God looking down at space time from above.
My pet variant of MWI is to do away with the discrete, tree-like “splits” and assume that the many worlds form a continuum. Essentially this means that there are multiple time dimensions, smoothly splitting the universe at every instant. Hence observations are not special in any way, and can’t even be clearly identified. It’s just stuff that “goes on”.
The really hard part for any TOE is not QM! The brutally difficult aspect is explaining the three particle generations.
Very few theories even begin to explain that…
> In my opinion it’s easier to keep GR
As far as I've read, most physicists have the opposite impression: that QM is much closer to the truth, and that it's almost impossible to add explain the Heisenberg Uncertainty Principle in GR. As some others have shown in the comments here, there are even models of QM that actually predict various GR phenomena for relatively flat space times (i.e. anything that's not very close to the event horizon of a black hole).
> Fundamentally, GR predicts that even an individual electron curves spacetime, and not just at “interstellar” distances.
That's exactly the problem. Since the electron is not localized in space-time according to all QM observations, it's very hard to define how it can then bend space-time. This is not an interpretation problem (so MWI vs CI has nothing to do with it), it's a problem with the math itself.
The problem with MWI on the other hand is that there is no satisfactory way to arrive at the observed measurement outcome probabilities, especially in these continuous splitting scenarios. These become an extra postulate just like in the CI interpretation.
> The really hard part for any TOE is not QM! The brutally difficult aspect is explaining the three particle generations.
Well, that's hardly a real problem. That there are multiple kinds of particles may very well just be a fundamental aspect of nature, one that doesn't require any explanation, any more than the value of c or pi does. If we had a theory that unifies QM and GR, that could be the final theory of how the universe works (well, assuming it also somehow explained what dark matter and dark energy are, to be fair).
As far as I've read, most physicists have the opposite impression: that QM is much closer to the truth, and that it's almost impossible to add explain the Heisenberg Uncertainty Principle in GR. As some others have shown in the comments here, there are even models of QM that actually predict various GR phenomena for relatively flat space times (i.e. anything that's not very close to the event horizon of a black hole).
> Fundamentally, GR predicts that even an individual electron curves spacetime, and not just at “interstellar” distances.
That's exactly the problem. Since the electron is not localized in space-time according to all QM observations, it's very hard to define how it can then bend space-time. This is not an interpretation problem (so MWI vs CI has nothing to do with it), it's a problem with the math itself.
The problem with MWI on the other hand is that there is no satisfactory way to arrive at the observed measurement outcome probabilities, especially in these continuous splitting scenarios. These become an extra postulate just like in the CI interpretation.
> The really hard part for any TOE is not QM! The brutally difficult aspect is explaining the three particle generations.
Well, that's hardly a real problem. That there are multiple kinds of particles may very well just be a fundamental aspect of nature, one that doesn't require any explanation, any more than the value of c or pi does. If we had a theory that unifies QM and GR, that could be the final theory of how the universe works (well, assuming it also somehow explained what dark matter and dark energy are, to be fair).
My personal goal has always been a TOE that allows aspects like particle generations and their various properties to be derived ab-initio from axioms with only simple constants such as integers or pi.
So particle generations ought to be an output, or an essential aspect of the geometry of the thing. In any event, the theory must model the generations, not just layer fields on top of fields like layers of pancake, or... epicycles on top of epicycles.
> most physicists have the opposite impression: that QM is much closer to the truth
This is the crux of the problem: QFT is newer than GR, and people often assume that newer is better. It had one huge numeric prediction success, and that has cemented the theory as more successful than all others in the minds of researchers. Never mind that they've sprinted up a valley to stare at a dead end, a proverbial insurmountable cliff up ahead.
> the electron is not localized in space-time
QM theorists would like to have things both ways at the same time, and then they make the surprised Pikachu face when things turn into nonsense. You can't have point particles smeared in space or even space-time. Pick one.
Or... use a model that allows a point in 3D space but treats it as a higher-dimensional object (surface/volume) in a higher dimensional space, such as the parallel worlds of MWI.
There are other options also. But throwing up one's hands is not the right path to a TOE, in my opinion...
So particle generations ought to be an output, or an essential aspect of the geometry of the thing. In any event, the theory must model the generations, not just layer fields on top of fields like layers of pancake, or... epicycles on top of epicycles.
> most physicists have the opposite impression: that QM is much closer to the truth
This is the crux of the problem: QFT is newer than GR, and people often assume that newer is better. It had one huge numeric prediction success, and that has cemented the theory as more successful than all others in the minds of researchers. Never mind that they've sprinted up a valley to stare at a dead end, a proverbial insurmountable cliff up ahead.
> the electron is not localized in space-time
QM theorists would like to have things both ways at the same time, and then they make the surprised Pikachu face when things turn into nonsense. You can't have point particles smeared in space or even space-time. Pick one.
Or... use a model that allows a point in 3D space but treats it as a higher-dimensional object (surface/volume) in a higher dimensional space, such as the parallel worlds of MWI.
There are other options also. But throwing up one's hands is not the right path to a TOE, in my opinion...
Your first point sounds a lot like the Schwarzschild Proton conjecture by Nassim Haramein, don't know if you were aware of it. Alas, I need to point out that it is basically considered pseudoscience!
I got the original concept from the quite famous "black hole electron" theory, but I'm not saying that particles are exactly like tiny black holes.
PS: My toy theories are not to be taken seriously, they're a product of idle musing only.
My method however, I think is sound: try and come up with something that simultaneously satisfies as many known experimental and theoretical constraints as possible, poke holes in it (hah!), fix, rinse, and repeat. Or discard as necessary. Whatever.
A motivation that has been bugging me is: What sets the scale of particles? How does the universe know that a proton here should be the same size as a proton there? Why can't we have giant protons?
A simple geometric argument could be something like assuming that particles are black-hole-like things as described previously, and that they are solitons. They're the smallest units of spin, where their rotation and size is balanced such that some aspect moves at the speed of light. They can't get smaller because then their rotation would have to increase past the speed of light. Hence, all particles have their sizes fixed by the constancy of the speed of light.
That's why I pasted my rambling thoughts in response to this article, my original idea started off thinking of particles as solitons that are also somewhat like black holes, which is the topic of the article.
PS: My toy theories are not to be taken seriously, they're a product of idle musing only.
My method however, I think is sound: try and come up with something that simultaneously satisfies as many known experimental and theoretical constraints as possible, poke holes in it (hah!), fix, rinse, and repeat. Or discard as necessary. Whatever.
A motivation that has been bugging me is: What sets the scale of particles? How does the universe know that a proton here should be the same size as a proton there? Why can't we have giant protons?
A simple geometric argument could be something like assuming that particles are black-hole-like things as described previously, and that they are solitons. They're the smallest units of spin, where their rotation and size is balanced such that some aspect moves at the speed of light. They can't get smaller because then their rotation would have to increase past the speed of light. Hence, all particles have their sizes fixed by the constancy of the speed of light.
That's why I pasted my rambling thoughts in response to this article, my original idea started off thinking of particles as solitons that are also somewhat like black holes, which is the topic of the article.
I don’t have anything to add other than I enjoy reading your idle musings. I’m not a physicist and don’t really know any real physics passed 101 college courses. I have similar idle musing with the speed of light so it’s nice to read another layman’s thoughts.
Some other notes from what I understand of current mainstream physics:
- elementary particles have no defined size in QM (electrons, quarks, neutrinos, photons etc); there is no known lower-bound on how small they could be, and there are serious mathematical issues both with assuming a non-0 radius, but other problems with assuming a radius of 0
- composite particles like a proton or a hydrogen atom have a size because of the relative strengths of the forces holding together their components; for example, the three quarks making up a proton must exist at a certain distance from one another because of the properties of the strong force; the electron of a hydrogen atom must "orbit" the proton at a certain distance because of the properties of the electrical force
- QM spin is not a rotation speed of any kind; QM particles are not little balls rotating around their center; quantum spin has no known relation to the speed of light
- replacing one constant of nature (the size of a proton, or at least of an elementary particle) by another constant of nature (the speed of light) is not really simplifying the theory; one could just as easily go the other way, and say that the speed of light is derived from the size of elementary particles in some other way
- elementary particles have no defined size in QM (electrons, quarks, neutrinos, photons etc); there is no known lower-bound on how small they could be, and there are serious mathematical issues both with assuming a non-0 radius, but other problems with assuming a radius of 0
- composite particles like a proton or a hydrogen atom have a size because of the relative strengths of the forces holding together their components; for example, the three quarks making up a proton must exist at a certain distance from one another because of the properties of the strong force; the electron of a hydrogen atom must "orbit" the proton at a certain distance because of the properties of the electrical force
- QM spin is not a rotation speed of any kind; QM particles are not little balls rotating around their center; quantum spin has no known relation to the speed of light
- replacing one constant of nature (the size of a proton, or at least of an elementary particle) by another constant of nature (the speed of light) is not really simplifying the theory; one could just as easily go the other way, and say that the speed of light is derived from the size of elementary particles in some other way
> elementary particles have no defined size in QM
That's only kinda-sorta true, and only in a very restricted sense.
All particles have a wavelength, but that can change depending on their velocity.
In QM models, it is a simplification to treat particle as point-like to make the mathematics tractable. It isn't necessarily an accurate picture of the underlying reality.
> QM spin is not a rotation speed of any kind; QM particles are not little balls rotating around their center; quantum spin has no known relation to the speed of light
That's not exactly the case. From my best understanding, Spin is just the Dirac Belt Trick, an indication that particles are part of the spacetime fabric and attached to it. When they rotate, the fabric rotates with them locally. This requires two full rotations (720 degrees) to go back to the original state, which is why you have "spin 1/2" and the complicated maths.
Two good visualisations are here: https://youtu.be/LLw3BaliDUQ and: https://youtu.be/jdVoFr5d4Rw
That's only kinda-sorta true, and only in a very restricted sense.
All particles have a wavelength, but that can change depending on their velocity.
In QM models, it is a simplification to treat particle as point-like to make the mathematics tractable. It isn't necessarily an accurate picture of the underlying reality.
> QM spin is not a rotation speed of any kind; QM particles are not little balls rotating around their center; quantum spin has no known relation to the speed of light
That's not exactly the case. From my best understanding, Spin is just the Dirac Belt Trick, an indication that particles are part of the spacetime fabric and attached to it. When they rotate, the fabric rotates with them locally. This requires two full rotations (720 degrees) to go back to the original state, which is why you have "spin 1/2" and the complicated maths.
Two good visualisations are here: https://youtu.be/LLw3BaliDUQ and: https://youtu.be/jdVoFr5d4Rw
> In QM models, it is a simplification to treat particle as point-like to make the mathematics tractable. It isn't necessarily an accurate picture of the underlying reality.
As far as I understand, it is more than that: it is an explicit assumption of the theory that elementary particles do not have an internal structure, and so their radius must be 0. This is not to be confused with the wave-like representation, which of course does have a size in space.
On the spin question, I will not claim I understand enough to actually go into more detail than the (probably simplistic) observation I've read that quantum spin can't be understood in terms of classical rotation/movement.
As far as I understand, it is more than that: it is an explicit assumption of the theory that elementary particles do not have an internal structure, and so their radius must be 0. This is not to be confused with the wave-like representation, which of course does have a size in space.
On the spin question, I will not claim I understand enough to actually go into more detail than the (probably simplistic) observation I've read that quantum spin can't be understood in terms of classical rotation/movement.
Your ideas are intriguing to me, and I wish to subscribe to your newsletter.
Has anyone considered that black holes may be defects in the model? There's an old phrase, "the map is not the territory". Some old maps show the edge of the world with giant sea monsters & ships falling off the ocean.
Einstein originally thought that black holes were simply an mathematical artifact, and not possible in reality.
Since then, we have observed objects that look a lot like we would expect black holes to look. There are theories, such as this one, that describe those objects as something different than what GR proposes, but thus far no testable prediction has contradicted GR's version.
Part of the problem is that many of the differences are about the interior of the event horizon. At least under GR's model, such differences are nit observable, even in principle.
Since then, we have observed objects that look a lot like we would expect black holes to look. There are theories, such as this one, that describe those objects as something different than what GR proposes, but thus far no testable prediction has contradicted GR's version.
Part of the problem is that many of the differences are about the interior of the event horizon. At least under GR's model, such differences are nit observable, even in principle.
What if black holes are NaNs in the simulation we live in. Maybe it was written by a phd student as an experiment for his thesis.
More like a half-baked elementary school science project.
Consider:
* Lazy evaluation was used to reduce computational costs. Unless an event is observed, it never collapses into reality. Cannot use up all household's hyper-electricity supply, parents will be mad.
* Make GR and QM work nicely together? Nah, too hard, the show-and-tell is tomorrow morning.
* Intelligent beings on multiple planets? Just a single planet will do for a C, maybe a C+. And no time left to make them interestingly different anyway.
Be ready, once the project grade is announced, this simulation will just blink out of existence. Hyper-CPU power will be needed for billions of years (our time) of hyper-Minecraft.
Consider:
* Lazy evaluation was used to reduce computational costs. Unless an event is observed, it never collapses into reality. Cannot use up all household's hyper-electricity supply, parents will be mad.
* Make GR and QM work nicely together? Nah, too hard, the show-and-tell is tomorrow morning.
* Intelligent beings on multiple planets? Just a single planet will do for a C, maybe a C+. And no time left to make them interestingly different anyway.
Be ready, once the project grade is announced, this simulation will just blink out of existence. Hyper-CPU power will be needed for billions of years (our time) of hyper-Minecraft.
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How can spacetime have a “defect”? Isn’t this just a feature?
In this case it's about topological defects[1], also known as topological solitons, which is explained rather well on SE here[2].
Mathematicians and physicists try to give words to concepts, they don't always map well. As Wikipedia puts it:
Topological solitons arise with ease when creating the crystalline semiconductors used in modern electronics, and in that context their effects are almost always deleterious. For this reason such crystal transitions are called topological defects. However, this mostly solid-state terminology distracts from the rich and intriguing mathematical properties of such boundary regions. Thus for most non-solid-state contexts the more positive and mathematically rich phrase "topological soliton" is preferable.
[1]: https://en.wikipedia.org/wiki/Topological_defect
[2]: https://physics.stackexchange.com/questions/285731/what-is-a...
Mathematicians and physicists try to give words to concepts, they don't always map well. As Wikipedia puts it:
Topological solitons arise with ease when creating the crystalline semiconductors used in modern electronics, and in that context their effects are almost always deleterious. For this reason such crystal transitions are called topological defects. However, this mostly solid-state terminology distracts from the rich and intriguing mathematical properties of such boundary regions. Thus for most non-solid-state contexts the more positive and mathematically rich phrase "topological soliton" is preferable.
[1]: https://en.wikipedia.org/wiki/Topological_defect
[2]: https://physics.stackexchange.com/questions/285731/what-is-a...
Interesting. During my time in solid state physics and later quantum information, we just used "(topological) defects", not "topological solitons", though of course papers trying to sound cool could use that term. It takes about 2 uses to not conflate "defect" with anything deleterious, just the breaking of an otherwise functional symmetry.
The same way computers can have a "bus" despite there being no large multi-passenger motor vehicle inside the laptop sitting on our desks. It's technical jargon that means something other than what the layperson thinks it means.
It's probably easiest to visualize the sense in which "defect" is used in the article by the analogous concept of https://en.wikipedia.org/wiki/Crystallographic_defect , a disruption in what is otherwise an orderly, regular structure.
It's probably easiest to visualize the sense in which "defect" is used in the article by the analogous concept of https://en.wikipedia.org/wiki/Crystallographic_defect , a disruption in what is otherwise an orderly, regular structure.
What I understood from the purported distinction when reading this article was that black holes result from physical activity within spacetime. Wheras solitons are constructs resulting from the mathematical arrangement of the fabric of spacetime (involving those other dimensions posited by String Theory) .
Do we happen to work at the same software company, by any chance?
It's not a bug. It's a feature.
Just update the specification with the observed behaviour and presto - black holes are no longer defective !
[deleted]
Did anyone else see the metric equation in the pdf? Talk about heavy-duty use of trig. Like a pre-calc nightmare. How was it derived?
> heavy-duty use of trig
Trig functions are useful in differential equations, expect them everywhere in differential geometry and geometric analysis.
> How was it derived
If you mean eqn (15) of "the pdf" <https://arxiv.org/abs/2203.12625> (which is what the author at the link at the very top of the discussion was trying to summarize), then it's largely a generalization of Weyl's 1917 "Zur Gravitationstheorie" approach (English translation at sci-hub: <https://sci-hub.se/https://link.springer.com/article/10.1007...>, in particular part B §4-§5 starting at page number 793, pdf page 15 of 32) into higher dimensions.
The particular generalization is described in "the pdf"'s reference 15, "Generalized Weyl Solutions" <https://arxiv.org/abs/hep-th/0110258v2>. Choice quote, "Depending on which feature of Weyl's class one focuses on, there are several directions in which one can try to extend it into higher dimensions." The authors choose an approach which produces a notion of the passage of time for a hypervolume of two fewer dimensions than the whole; contrast this with a notion of the passage of time for a three-dimensional hypersurface of a Lorentzian (3+1, or four dimensions) manifold like our own universe appears to be.
The authors of "the pdf" per the top of II. THE GEOMETRIES focus on five and six dimensions, the former producing following the logic of their ref 15 a set of 3d spatial volumes that are related by a notion of time, which invites comparisons with a Lorentzian manifold like our own, and which they do in III and IV. Their result is that they cannot make their structures observably indistinguishable from Schwarzschild black holes. They do not go further into merely very slowly spinning their topological solitons, and it's not clear what the metric for those would look like, or observationally how they would compare to very slowly spinning Kerr solutions (which become indistinguishable from Schwarzschild).
One of the recurring themes of M-theory/stringy gravity starts with that we see a lot of spinning objects in hydrostatic equilibrium, including relativistic objects like neutron stars (notably millisecond pulsars). We can pick out the orbits of even very small companion objects in close orbits around these (< 2% of mass of Earth, < 1/2 the apoapsis of Mercury <https://exoplanets.nasa.gov/exoplanet-catalog/7134/psr-b1257...>). Those orbits are essentially Kerr orbits (non-gravitational perturbations from e.g. the NS's radiation or magnetic field are small). M-theory/stringy gravity appears largely stuck on recovering spherical symmetry (for black holes and galaxies (e.g. Verlinde's vintage 2011 emergent gravity)) rather than obviously rotating distributions of mass with lumpy and even heavy satellites (from Draugr to the Large Magellanic Cloud and its dozens of friends, to clusters of thousands of galaxies). General Relativity's universality of free fall (UFF or "strong equivalence principle") is extremely well supported at all these scales. That UFF needs to be searched for (often requiring strong suppression of extra gravitational degrees of freedom, except exactly where they want to be different from naive quantization of General Relativity) in these supergravity theoretical ideas mean these theories are maybe-interesting but of no practical astrophysical value at this time.
Trig functions are useful in differential equations, expect them everywhere in differential geometry and geometric analysis.
> How was it derived
If you mean eqn (15) of "the pdf" <https://arxiv.org/abs/2203.12625> (which is what the author at the link at the very top of the discussion was trying to summarize), then it's largely a generalization of Weyl's 1917 "Zur Gravitationstheorie" approach (English translation at sci-hub: <https://sci-hub.se/https://link.springer.com/article/10.1007...>, in particular part B §4-§5 starting at page number 793, pdf page 15 of 32) into higher dimensions.
The particular generalization is described in "the pdf"'s reference 15, "Generalized Weyl Solutions" <https://arxiv.org/abs/hep-th/0110258v2>. Choice quote, "Depending on which feature of Weyl's class one focuses on, there are several directions in which one can try to extend it into higher dimensions." The authors choose an approach which produces a notion of the passage of time for a hypervolume of two fewer dimensions than the whole; contrast this with a notion of the passage of time for a three-dimensional hypersurface of a Lorentzian (3+1, or four dimensions) manifold like our own universe appears to be.
The authors of "the pdf" per the top of II. THE GEOMETRIES focus on five and six dimensions, the former producing following the logic of their ref 15 a set of 3d spatial volumes that are related by a notion of time, which invites comparisons with a Lorentzian manifold like our own, and which they do in III and IV. Their result is that they cannot make their structures observably indistinguishable from Schwarzschild black holes. They do not go further into merely very slowly spinning their topological solitons, and it's not clear what the metric for those would look like, or observationally how they would compare to very slowly spinning Kerr solutions (which become indistinguishable from Schwarzschild).
One of the recurring themes of M-theory/stringy gravity starts with that we see a lot of spinning objects in hydrostatic equilibrium, including relativistic objects like neutron stars (notably millisecond pulsars). We can pick out the orbits of even very small companion objects in close orbits around these (< 2% of mass of Earth, < 1/2 the apoapsis of Mercury <https://exoplanets.nasa.gov/exoplanet-catalog/7134/psr-b1257...>). Those orbits are essentially Kerr orbits (non-gravitational perturbations from e.g. the NS's radiation or magnetic field are small). M-theory/stringy gravity appears largely stuck on recovering spherical symmetry (for black holes and galaxies (e.g. Verlinde's vintage 2011 emergent gravity)) rather than obviously rotating distributions of mass with lumpy and even heavy satellites (from Draugr to the Large Magellanic Cloud and its dozens of friends, to clusters of thousands of galaxies). General Relativity's universality of free fall (UFF or "strong equivalence principle") is extremely well supported at all these scales. That UFF needs to be searched for (often requiring strong suppression of extra gravitational degrees of freedom, except exactly where they want to be different from naive quantization of General Relativity) in these supergravity theoretical ideas mean these theories are maybe-interesting but of no practical astrophysical value at this time.
What if black holes are a very thin shell and all the matter is just on the surface, orbiting so fast around a center that it cannot escape
First: “Orbiting the center” implies movement in circles and ellipses, and thus implies angular momentum. Angular momentum is a conserved quantity. If the collapsing star didn’t have it, the black hole’s contents won’t spontaneously develop it. Some black holes do have it, but not all.
Second: under general relativity spacetime is biased so the three direction “future” is pointed to the center of the black hole. This is true of any mass, but in the black hole it is so intensely pointed that even traveling through the space part of spacetime at the maximum possible speed (the speed of light) isn’t fast enough to escape that, not in any direction. Perhaps the fastest moving objects at the very edge of the region of space we call the “event horizon” could fall in slowly enough that the black hole evaporates around them? I dunno, I don’t have math for it. But even then I wouldn’t count on it for the general case.
Better to imagine everything crushed as it is dragged to the center - perhaps first into neutronium, and then quarkium, and then something hard to say except that it’s all a giant high-energy mess.
Second: under general relativity spacetime is biased so the three direction “future” is pointed to the center of the black hole. This is true of any mass, but in the black hole it is so intensely pointed that even traveling through the space part of spacetime at the maximum possible speed (the speed of light) isn’t fast enough to escape that, not in any direction. Perhaps the fastest moving objects at the very edge of the region of space we call the “event horizon” could fall in slowly enough that the black hole evaporates around them? I dunno, I don’t have math for it. But even then I wouldn’t count on it for the general case.
Better to imagine everything crushed as it is dragged to the center - perhaps first into neutronium, and then quarkium, and then something hard to say except that it’s all a giant high-energy mess.
> orbiting so fast around a center
Inside the event horizon you’d need to orbit faster than the speed of light. Outside the event horizon - if the matter wasn’t in orbit before then it can’t magically gain momentum to be in orbit.
Inside the event horizon you’d need to orbit faster than the speed of light. Outside the event horizon - if the matter wasn’t in orbit before then it can’t magically gain momentum to be in orbit.
Sure, but wouldn't something need to be in the center for it to do that?
https://www.livescience.com/62547-what-is-center-of-universe...
The universe has no center. Maybe nothing has a center?
The universe has no center. Maybe nothing has a center?
I don't think black holes are what is being described here, but no, it would not fundamentally be all that different from a binary system orbiting around a shared center of gravity between the two objects.
[deleted]
> Since we know that infinite densities cannot actually happen in the universe...
Lol, and how exactly do we know that?
Lol, and how exactly do we know that?
https://physics.stackexchange.com/questions/26515/what-is-ex...
But if it wasn't for that, you wouldn't be able to collect infinite mass in less than infinite time.
But if it wasn't for that, you wouldn't be able to collect infinite mass in less than infinite time.
Is it true that general relativity also predicts white holes?
they might be cosmic whale blow holes too
Or proof of a simulation... :)
Test
The only defect is in our understanding.
People understand this dogma perfectly well, no reasoning or critical thinking required. Literal, to be under the standing of another mind.
No logical basis exists for black holes, they are a rationalization for the faulty foundation upon which they lie, a fantasy to explain condescending pseudotheory.
The defect is defending a false doctrine, accepting as truth a scientifically evident hoax.
No logical basis exists for black holes, they are a rationalization for the faulty foundation upon which they lie, a fantasy to explain condescending pseudotheory.
The defect is defending a false doctrine, accepting as truth a scientifically evident hoax.
I think defects imply you know there is some purpose other than the phenomenon you are referring to as a defect
Not at all. Defects are typically just points of discontinuity or where a pattern breaks. These happen when something relatively continuous is forming but then the pattern breaks locally due to either global initial conditions or something unusual happening locally.
I think the term is probably borrowed from the theory of crystal lattices where defects are classified: dislocations, substitutions, and holes. As a crystal is forming, sometimes two contiguous regions can't come together in the same pattern because of initial conditions where the lattice won't line up right. These then form adjacent "grains". Alternatively, sometimes internal stresses result in a dislocation where a large section of crystal shifts along a line of symmetry. Or sometimes a stray impurity is hanging out and a crystal forms around it. Or holes happen where it's just like musical chairs as the crystal is forming and there's one too few atoms to go around.
In none of those cases is there some "purpose", and yet there is a clear local discontinuity in an otherwise large scale pattern. The terminology fits pretty well to the situation here I think, only they're speaking about topological phenomena.
I think the term is probably borrowed from the theory of crystal lattices where defects are classified: dislocations, substitutions, and holes. As a crystal is forming, sometimes two contiguous regions can't come together in the same pattern because of initial conditions where the lattice won't line up right. These then form adjacent "grains". Alternatively, sometimes internal stresses result in a dislocation where a large section of crystal shifts along a line of symmetry. Or sometimes a stray impurity is hanging out and a crystal forms around it. Or holes happen where it's just like musical chairs as the crystal is forming and there's one too few atoms to go around.
In none of those cases is there some "purpose", and yet there is a clear local discontinuity in an otherwise large scale pattern. The terminology fits pretty well to the situation here I think, only they're speaking about topological phenomena.
String theory like most of theoretical physics is just made up. Today our knowledge of atomic physics and the cosmos is no more improved little since 1945. There’s a lot of theories, but ultimately they just add up to different kinds of particles interacting in non-verifiable ways. If you look at the actual advancements it’s pretty laughable we’re sitting here saying “Hey look this theoretical thing called a black hole, that easily could just be some type of unknown radio telescope interference? It maybe might exist for a different reason than we thought!” Your layman’s understanding that a black hole is some kinda big suck-y thing in space is actually better then engineering an elaborate and probably incorrect theory.
Defect means imperfection, shortcoming, flaw. This implies reality has a design, a plan, that it was executed according to, which execution can have defects in it, compared to the plan. Design & plan means designer & planner.
So yeah, we should be careful what words we use.
So yeah, we should be careful what words we use.
It also means an irregularity in an otherwise regular structure. It's jargon, which probably shouldn't be used in a popular science article, but it does not imply any sort of plan.
> which probably shouldn't be used in a popular science article
Depends on if you're maximizing for 'engagement' I guess :/
Depends on if you're maximizing for 'engagement' I guess :/
Define "regular structure". So the center of the sun is as regular as my living room, but a black hole is a bit too much for someone. For whom though? And how did they decide this?
Funny that I get downvoted. I'm curious what is pissing everyone off that much. Physics and spacetime have no "defect" unless you define relative to what. Our theories of physics are just models we work with for our benefit, reality is entirely unconstrained by our models and concerns. And our opinions of a "defect" with respect to our models.
We've long known the singularity is only "singularity" with respect to General Relativity. It's the place where the model breaks down. The model, not reality.
We've long known the singularity is only "singularity" with respect to General Relativity. It's the place where the model breaks down. The model, not reality.
"Defect" has a different meaning here than it has in common language, so people disagree with the comment.
If you are curious, then try articles like on "Topological defect", "Crystallographic defect", "Cosmic string", ... in Wikipedia to get an idea what defect is supposed to mean here.
> Our theories of physics are just models we work with for our benefit, reality is entirely unconstrained by our models and concerns.
True but every student of physics is taught right from the beginning that every model only has a range of parameters in which it is valid.
Example: you can easily calculate speeds non-relativistically just fine if you are aware that you will only get good approximations of reality if the speeds involved are a low (~ single-digit) percentage of the speed of light. Outside of that, the results will be non-sense.
We create the models after reality and use these models to predict things. After experiments, we know if the the model is still valid in a new range of parameters. Since we know that the laws of nature do not change (we can and do test that!), we can now assume that we have a model that fits well with reality in a wider range than before.
What you see here in progress is exactly the attempt to find an alternative explanation for that what we expect blackholes to look like because we know that our models might not be right there.
If you are curious, then try articles like on "Topological defect", "Crystallographic defect", "Cosmic string", ... in Wikipedia to get an idea what defect is supposed to mean here.
> Our theories of physics are just models we work with for our benefit, reality is entirely unconstrained by our models and concerns.
True but every student of physics is taught right from the beginning that every model only has a range of parameters in which it is valid.
Example: you can easily calculate speeds non-relativistically just fine if you are aware that you will only get good approximations of reality if the speeds involved are a low (~ single-digit) percentage of the speed of light. Outside of that, the results will be non-sense.
We create the models after reality and use these models to predict things. After experiments, we know if the the model is still valid in a new range of parameters. Since we know that the laws of nature do not change (we can and do test that!), we can now assume that we have a model that fits well with reality in a wider range than before.
What you see here in progress is exactly the attempt to find an alternative explanation for that what we expect blackholes to look like because we know that our models might not be right there.
Its presumed lack of falsifiability has been one of its drawbacks and has been the source of some of the controversy around it.
Finding a potential test that could be conducted with telescopes instead of high energy particle accelerators would be a big moment in modern physics.