Is Dark Matter Just Old Gravitons from Other Dimensions? (livescience.com) 104
"Dark matter, the elusive substance that accounts for the majority of the mass in the universe, may be made up of massive particles called gravitons that first popped into existence in the first moment after the Big Bang," writes Live Science.
"And these hypothetical particles might be cosmic refugees from extra dimensions, a new theory suggests." The researchers' calculations hint that these particles could have been created in just the right quantities to explain dark matter, which can only be "seen" through its gravitational pull on ordinary matter. "Massive gravitons are produced by collisions of ordinary particles in the early universe. This process was believed to be too rare for the massive gravitons to be dark matter candidates," study co-author Giacomo Cacciapaglia, a physicist at the University of Lyon in France, told Live Science. But in a new study published in February in the journal Physical Review Letters, Cacciapaglia, along with Korea University physicists Haiying Cai and Seung J. Lee, found that enough of these gravitons would have been made in the early universe to account for all of the dark matter we currently detect in the universe.
The gravitons, if they exist, would have a mass of less than 1 megaelectronvolt (MeV), so no more than twice the mass of an electron, the study found. This mass level is well below the scale at which the Higgs boson generates mass for ordinary matter — which is key for the model to produce enough of them to account for all the dark matter in the universe....
The team found these hypothetical gravitons while hunting for evidence of extra dimensions, which some physicists suspect exist alongside the observed three dimensions of space and the fourth dimension, time. In the team's theory, when gravity propagates through extra dimensions, it materializes in our universe as massive gravitons. But these particles would interact only weakly with ordinary matter, and only via the force of gravity. This description is eerily similar to what we know about dark matter, which does not interact with light yet has a gravitational influence felt everywhere in the universe. This gravitational influence, for instance, is what prevents galaxies from flying apart.
"The main advantage of massive gravitons as dark matter particles is that they only interact gravitationally, hence they can escape attempts to detect their presence," Cacciapaglia said.
"And these hypothetical particles might be cosmic refugees from extra dimensions, a new theory suggests." The researchers' calculations hint that these particles could have been created in just the right quantities to explain dark matter, which can only be "seen" through its gravitational pull on ordinary matter. "Massive gravitons are produced by collisions of ordinary particles in the early universe. This process was believed to be too rare for the massive gravitons to be dark matter candidates," study co-author Giacomo Cacciapaglia, a physicist at the University of Lyon in France, told Live Science. But in a new study published in February in the journal Physical Review Letters, Cacciapaglia, along with Korea University physicists Haiying Cai and Seung J. Lee, found that enough of these gravitons would have been made in the early universe to account for all of the dark matter we currently detect in the universe.
The gravitons, if they exist, would have a mass of less than 1 megaelectronvolt (MeV), so no more than twice the mass of an electron, the study found. This mass level is well below the scale at which the Higgs boson generates mass for ordinary matter — which is key for the model to produce enough of them to account for all the dark matter in the universe....
The team found these hypothetical gravitons while hunting for evidence of extra dimensions, which some physicists suspect exist alongside the observed three dimensions of space and the fourth dimension, time. In the team's theory, when gravity propagates through extra dimensions, it materializes in our universe as massive gravitons. But these particles would interact only weakly with ordinary matter, and only via the force of gravity. This description is eerily similar to what we know about dark matter, which does not interact with light yet has a gravitational influence felt everywhere in the universe. This gravitational influence, for instance, is what prevents galaxies from flying apart.
"The main advantage of massive gravitons as dark matter particles is that they only interact gravitationally, hence they can escape attempts to detect their presence," Cacciapaglia said.
Pssssht (Score:4, Funny)
Well, duh, why didn't I think of that? It's so simple!
A village in another dimension (Score:2)
Is missing its gravitons.
The bit I loved was... (Score:2)
"The main advantage of massive gravitons as dark matter particles is that they only interact gravitationally, hence they can escape attempts to detect their presence,"
You have to smile when theorists see the untestability of their model as an advantage!
Re: The bit I loved was... (Score:2)
It's not actually untestable, just untestable by the approach used.
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I would agree with your statement, but would love to hear hypothetical ways to test this? I mean the big question seems to be how does it propagate through extra dimensions? Could we find insight via massive collisions like blackhole mergers and other experiments studying gravitation waves (e.g. we discover the energy released seems to dissipate into extra dimensions or some kind of weird synergy which I wouldn't even begin to be able to explain in terms of physics). Is there some type of novel trap that co
Missed the Point (Score:2)
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Yeah, the "just" in the title is bizarre. If that is what it turns out to be, that would be truly amazing.
That is not what that word means (Score:5, Informative)
When you say something is "just" something else, that something else has to be something mundane and even predictable. Why can't Slashdot afford even one editor for whom English is their first language?
Re:That is not what that word means (Score:5, Funny)
When you say something is "just" something else, that something else has to be something mundane and even predictable. Why can't Slashdot afford even one editor for whom English is their first language?
Don’t worry, when it’s posted again in a few days it might be better.
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When you say something is "just" something else, that something else has to be something mundane and even predictable.
When you say "just old XXX" it gets even worse.
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No true graviton is old.
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Picking up the torch as the grammar nazi?
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Picking it up? I never put it down.
I prefer to let user errors slide, which may be why it hasn't previously been apparent.
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These are the particles that interact not with matter, not with light but with karma. Karma is the actions of the mortals. Dharma is the justice meted out by Time to the mortals for their Karma. Time is the fourth dimension, the Other Dimension mentioned in
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So what you're saying is, they're Justified and they're ancient? And they come from up above?
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Just Gravitons can be a heavy weight to bear.
Betteridge's Law of Headlines (Score:2, Insightful)
"No".
The eager rush for exotic forms of matter is continuing. There are several far less exotic explanations which various physicists refuse to discuss rationally.
1) Bad models of the size and age of the universe. The red shift and the background temperature of the universe are verified, but Hubble's Law about red shift versus distance is concluded based on measures of distance. Complex models of slowing of of expansion of the universe are based on detected luminosity and conclusions about the size and age
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Your stuff doesn't explain why galaxies do not fly apart which dark matter does explain.
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Your stuff doesn't explain why galaxies do not fly apart which dark matter does explain.
Actually , it's more like "If dark matter existed, the rate at which galaxies fly apart would match current theory." Drank matter is the luminiferous aether of our time.
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No, "drank matter" is what physicists do at late night, after they drank too much beers.
Drank marrer is what I get when I post on my phone.
Drank Matter (Score:3)
Isn't Drank Matter the awful tasting carbonated grape soda that opioid addicts mix with cough syrup to get a buzz when their supply of fentanyl dries up?
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As distinct from "Dank Matter", the self-indulgent Whedonverse wannabe sci-fi series that got cancelled just as it got to the eagerly anticipated and greatly foreshadowed appearance of the Big Bad That Kills Everyone Oh Noes How Will They Survive (TM).
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MACHO, MACHO, MACHO Man (Score:5, Interesting)
I think such objects are called MACHOs for MAssive Compact Halo Objects.
These contrast with WIMPs for Weakly Interacting Massive Particles.
MACHOs have been considered but ruled out because reasons you mention. Similarly, neutrinos as the WIMPs have been ruled out because they would be hot dark matter as even if they have a small rest mass, the fly around almost at the speed of light, and current models require cold dark matter, hence the search for exotic particles.
Then there is Mordhai Milgrom's Modified Newtonian Dynamics theory, which proponents such as Pavel Kroupa claim explain galaxy rotation curves and Milky Way and Andromeda satellite galaxies really well, only the Dark Matter Mafia say it doesn't.
If I am keeping up with the press releases and the YouTube talks on the subject, Kroupa and his colleagues claim that their supercomputer modeling strongly falsifies Dark Matter on that scale, but I believe that Kroupa admits that Milgrom's "MOND" theory doesn't explain the very early universe and the inhomogeneity or lack thereof in the Cosmic Background radiation. Kroupa whinges that no one will grant him money to hire a numerical modeling person to tackle a relativistic supercomputer model of the early universe.
Then there is astrophysicist and science populizer Sabine Hossenfelder who explains that the Dark Matter people claim the missing source of gravitation holding galaxies and clusters together is a particle whereas the MOND people are claiming the effect is an unknown field. Her explanation that maybe both camps are correct because in quantum mechanics, a field can be a particle and a particle can be a manifestation of a field, well, appears to be hand wavings on the level of this know-it-all guy I knew in high school.
Maybe Hossenfelder is on to something? The Dark Matter/MOND divide should be thought about in terms of whether the effect is loosely coupled to the visible matter such as the dark matter halo that is supposed to extend well beyond the observable galaxy or if the effect is strongly connected to the visible matter, giving rise to the corrections to Newtonian acceleration in MOND?
There you have it. I have watched hours of YouTube videos on this subject, so you don't have to.
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Maybe Hossenfelder is on to something? The Dark Matter/MOND divide should be thought about in terms of whether the effect is loosely coupled to the visible matter such as the dark matter halo that is supposed to extend well beyond the observable galaxy or if the effect is strongly connected to the visible matter, giving rise to the corrections to Newtonian acceleration in MOND?
Overall I think Dr. Hossenfelder is pretty good at explaining things succinctly (sometimes too succinctly), often covering a wider picture than most. However, as is brought up in the video, evidence of the bullet cluster along with many other smaller galaxies who are stripped of dark matter is a death knell for MOND. MOND requires consistency in observation and the inconsistencies just keep increasing in confidence. Saying the dark particle has its own field is really a subset of WIMPs with an extra ste
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There you have it. I have watched hours of YouTube videos on this subject, so you don't have to.
Dude, WTF?!? Now what am I supposed to do today. I got an entire fridge full of beer and a now useless YouTube playlist. Worst rainy day every.
More Fundmental Problem (Score:3)
Large quantities of exoplanets unattached to stellar systems is a non-starter. Generally, planets contain large quantities of metal...
There is actually a more fundamental problem than that: planets are made of baryonic matter. This means they would couple and be part of the plasma in the early universe whereas Dark Matter is non-baryonic matter since it was decoupled at this point and compressing the plasma gravitationally giving the charactistic "clumpiness" seen by the WMAP and Planck satellites.
Whatever Dark Matter is it cannot be made of baryons. If you want macroscopic Dark Matter then the only serious remaining candidate I'm awa
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The problem observed with the CMB is that when you compress a plasma then, just l
Re: Betteridge's Law of Headlines (Score:2)
VLT can also lead to "bad" models of the universe.
one of many ideas (Score:5, Informative)
Re: one of many ideas (Score:3)
It's testable, too. If you have extra dimensions, you must have supersymmetry and the upgraded LHC will determine if that exists.
If you have extra universes, type 1a supernovae must violate conservation of mass and energy and (in principle) we've the ability to determine that as the 1a is a standard candle.
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I asked for the testability you mentioned above before finishing the comments. Thanks for sharing.
I am a bit lost on how the test of a standard candle works? Are you saying their emissions of photons would change?
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http://astro.physics.uiowa.edu... [uiowa.edu]
Let's say we have a type 1a supernova and it's one of the stars mapped in 3D by Gaia, so we've a relatively precise measure of distance. The actual brightness follows a very standard curve, but can be somewhere within a range of values. Since we know the measured distance and the measured brightness, we know where in the range it is.
Now, I could be wrong on this, but that would seem to imply that we know the original mass of the star (since that must determine where in the r
Wouldn't gravitons move at the speed of light? (Score:3)
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> If so, they wouldn't clump in galaxies and clusters any more than neutrinos would. They would just scatter across the universe.
Shhh, don't forget about the missing mass needed for 'gravitons' to interact with, obviating the need for these gravitons.
Quantized Inertia does a better job as explaining the rotation of galaxies and Casimir/capacitance effects without the need for hypothetical new dimensions holding hypothetical new particles interacting in hypothetical new ways using classic wave theory.
But
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Quantized Inertia does a better job as explaining the rotation of galaxies and Casimir/capacitance effects without the need for hypothetical new dimensions holding hypothetical new particles interacting in hypothetical new ways using classic wave theory.
Yes, it explains perhaps 99%+ of galaxy rotation curves but does not address galaxies with little to no dark matter at all despite the conditions for such strippage being rare. Nor does it properly address gravitational lensing. Nor does it address the microwave background. All it takes is a single counter example, and the evidence is past the tipping point such that very few people take a modified dynamics approach by itself as the sole exploration seriously anymore.
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I think your concluding the graviton emissions would be evenly disputed but it seems like it's saying some phenomena could be continually producing them. This means even if they are spreading out, there would still likely be some domain where the density of gravitons greater and this region would be what keeps galaxies in their shape.
Aliens Super Structures (Score:1)
Do we know how to Science! (Score:5, Insightful)
"And these hypothetical particles might be cosmic refugees from extra dimensions, a new theory suggests."
You cannot have a theory around a hypothesis. You just have a hypothesis.
I normally don't get bugged out on semantics, however science reporting especially to the public is full of this stuff, which discredits real scientific theories. Because a hypothesis is more often wrong than right. While a Theory is more often right then disproved. We get to a Scientific theory After a lot of real evidence shows it to be true. A hypothesis is often just an educated guess, that may happen to fill a blank hole in an equation.
This type of reporting is why so many people snuff their noes at scientific statements, because the news makes it out that every new crazy idea is true because it is science, then shows it to be untrue a week or years later. While for almost all these cases, what was reported was just a hypothesis.
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This type of reporting is why so many people snuff their noes at scientific statements, because the news makes it out that every new crazy idea is true because it is science, then shows it to be untrue a week or years later. While for almost all these cases, what was reported was just a hypothesis.
This video sums that up perfectly [youtube.com]
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This is more like fiction, or storytelling, or CNN news.
Particle Physics (Score:5, Informative)
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That's not what a theory means. "Theory" is roughly a synonym for "description". Theoretical science is the half of the scientific enterprise that focuses on coming up with new descriptions. The theory of evolution describes how species evolve. The theory of relativity describes the geometry and dynamics of spacetime. A theory is a description.
A theory might or might not be a good description. In areas we don't understand well, like dark matter, there tend to be lots of competing theories. That is, l
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Are Slashdot headlines just sillyness (Score:1)
...rephrased as questions, the answer to which is always "No" ?
Observations (Score:5, Insightful)
Galaxy rotation rates which we now know are variable for a given observed mass distribution as if some have it and some don’t
Gravitational lensing that can’t be attributed to what is seen
Models of galaxy formation
How visible matter gets distributed during galaxy collisions
The structure of the cosmic microwave background
How groups of galaxies move
Regardless of what it exactly is, a vast number of non interacting particles (except through gravitation), small enough to not cause visible lensing events does explain observations while other theories do not. Since all of the easy explanations have been ruled out, the answer is nearly guaranteed to be something odd or unusual. In any case, the universe doesn’t owe us a common sense answer when our common sense is based on an infinitesimally thin slice of the energy and scale possible.
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Just as a quick reminder : post-WWII, we had a standard model that seemed to work pretty well. Fast-forward a few decades, and the improvements to our various measure instruments showed huge discrepancies. To address that, essentially we could either:
A) Admit the error, and back to the drawing board to try and rebuild a new model that fit better with what we could see (no need to restart from scratch, just go back to genera
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Almost exactly right. (Score:5, Funny)
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Dark matter is the spacetime fabric (Score:1)
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The smoothly distributed dark matter displaced by the quarks the Sun consists of, pushing back and exerting pressure toward the Sun, causes gravity.
If that was true, then gravity would be proportional to volume, not mass. It is not.
Re: Dark matter is the spacetime fabric (Score:2)
Well, no. You're thinking dark energy. Dark matter is clumpy.
Re: Bending Over Backwards (Score:2)
But that won't buy us the next larger particle accelerator. We would be stepping back to a world of theoreticians who need nothing more than chalk and a blackboard.
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this.
Re: Bending Over Backwards (Score:3)
That's not actually correct. We know the standard model cannot be complete, if what we have is correct, regardless of dark matter. If the standard model is incorrect, we need improved sensitivity (which means higher energies) to establish where and why.
So we need bigger accelerators anyway. I'd bite the bullet and go for a 100 mile diameter ring. It's pointless building anything smaller because it's far more expensive in the long run and increases the instability of the rock.
I'd also put particle detectors
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Inception Science (Score:2)
The theoretical dark matter that we can't prove exists might be theoretical gravitons (which we can't prove exist) coming from other theoretical dimensions (which we really can't prove exist).
We're being presented with a hypothesis based on two other hypotheses that have no proof at all? The only thing that's remarkable is that they kept a straight face while presenting this.
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The theoretical dark matter that we can't prove exists might be theoretical gravitons (which we can't prove exist) coming from other theoretical dimensions (which we really can't prove exist).
No. Dark matter and dark energy exists as measured in multiple ways. We do not know exactly what it is. That gap has historically existed in physics. Light was known to exist since the dawn of humans but the exact nature of light has not been known until more modern times.
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No.
We've seen gravitational effects and literally nothing else, hence the name dark matter. That isn't something that's been "measured in multiple ways" and it doesn't define what it is.
Dark matter can't be defined as "whatever the hell is causing that gravity effect" and left at that, as if you'd solved the dilemma and no further research needs to be done, yet that's exactly what you're trying to do.
Using that same logic, light would have been defined as "that thing that lets us see" and nobody would have
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We've seen gravitational effects and literally nothing else, hence the name dark matter. That isn't something that's been "measured in multiple ways" and it doesn't define what it is.
This is a physicist explaining the evidence for dark matter. [youtube.com] It spans over a century.
Dark matter can't be defined as "whatever the hell is causing that gravity effect" and left at that, as if you'd solved the dilemma and no further research needs to be done, yet that's exactly what you're trying to do.
Please watch the video or read up on the evidence. Something is causing a lot of gravity and it is not normal matter. Hence dark matter.
Using that same logic, light would have been defined as "that thing that lets us see" and nobody would have ever investigated further to define what it actually was.
Wow you really misunderstood the point. Since the dawn of humans, we know that light exists. No one could capture light. No one knew why some forms of light were hot like a fire or the sun was hot while the moon was cool. Thus we did not know the exact nature of light . By your logic light
Red lectroids or black ones? (Score:5, Funny)
Assuming, of course, that the particles are from the eighth dimension. Laugh while you can, monkey boy.
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Re: Red lectroids or black ones? (Score:3)
The new idea is falsifiable. The upgraded LHC can look for supersymmetry. If supersymmetric particles don't exist, there are no higher dimensions.
Equally, since we have good enough models for type 1a supernovae to use them as standard candles, we can determine if such supernovae violate the conservation of mass and energy. If they do not, there are no other universes.
(Conservation laws apply to closed systems only. If you can inflate another universe, then at the initial point - and the initial point only,
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When we experimentally confirm the existence of dark matter and/or dark energy, then we might have to abandon or fundamentally redefine the Standard Model; but until then, perhaps we really need a better explanation then "spooky stuff in the distance" for the inexplicable cohesion of galaxies or the ev
If you don't comprehend the difference (Score:2)
Between the simple, observable phenomena such as the expansion of the universe, spacetime and the property of the speed of light, and the fictional phenomena of epicycles and angels, that's strictly your problem.
If you cannot understand the difference between testable, falsifiable, predictions and mysticism, then don't blame scientists.
Happens there too (Score:1)
Old coders kicked out of other universes for not buying into stupid fads. (No, I'm not salty...really.)
Occam's razor (Score:2)
The more I read about the search of dark matter -- and dark energy too -- the more I think about the the 19th century search for aether, which never existed and eventually proved not to be necessary to explain anything. Each new hypothesis about dark matter seems to violate ever more widely Occam's razor.
The April 2022 issue of Scientific American has an article "Scanning the Cosmos for Dark Matter". It describes several different hypotheses and suggests how to verify or refute each. The most simple hyp
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This hypothesis doesn't explain dark energy either. Generally speaking, I don't think any theory has really tried to kill these two birds with one stone. Unless you really want to throw the monkey wrench and discuss if gravity could have a repulsive element like most/all other forces.
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(and assumes that the value of c has been constant since the instant of the Big Bang, a foolish assumption IMHO).
And you have evidence that the speed of light has changed over the history of the universe. And you can prove it?
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The microscopic blackhole theory is probably on about the same footing as this. You can purpose cosmological models that would permit them at sizes necessary with their own issues, like how long should these blackholes evaporate. However, detecting them seems to be the same problem between both these. We need something testable but more theories are always helpful.
Quantum gravity (Score:2)
Some physicists keep insisting that gravity HAS to have a particle to explain its existence. The graviton and quantum gravity will be looked at as the aether of our time.
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Some physicists keep insisting that gravity HAS to have a particle to explain its existence. The graviton and quantum gravity will be looked at as the aether of our time.
The comparison sounds rather backwards, because to me, the particle model of forces replaced the aether theory. We don't need the aether as a medium for electromagnetic wave motion, and all the evicence says that such a medium can't exist.
The same goes for gravity and other fundamental forces. If think gravity is so different from other forces and doesn't work by exchanging particles, then you need to find another explanation -- perhaps a gravitational aether?
(My terminology may be a little rusty after
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There is a very complete explanation of gravity. It's called general relativity. There's even some newer theories that are viewing gravity as a result of gradients in time dilation.
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I also studied GR, and I don't regard it as opposing the particle model. There have been similar geometric formulations of electromagnetism too, such as the Kaluza-Klein theory. The geometric formulation of GR explains gravity at the macroscopic level, but I like to think there's an underlying quantum/particle mechanism that mediates the force.
I also studied a gauge-theory formulation of gravity as a part of the Geometric Algebra [cam.ac.uk] course, and it also gave a nice unifying feel between gravitation and the o
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I don't think QT and GR are opposing models at all. I see them more as different models that describe different aspects of the universe. Kind of like how photosynthesis and turbulent flow of fluids have their own models. I don't see gravity as a force at all and see no real reason why it has to be explained with QT. Every model that tries to explain it as such falls well short with little in the way of testability. Personally I feel that one day someone will figure out a model that explains what exactl
No! (Score:2)
No!
No, it's unicorn fart. (Score:2)
If I add calculations to it can I claim to have a theory that dark matter could be made of unicorn fart? This "study" is no different. Speculation upon speculation upon wild guesses. This is not physics.
Here is some context (Score:2)
Whenever someone talks about extra dimensions, it's good to understand how far down the hypothetical rabbit hole we are and how little evidence it's based on.
We don't have a shred of evidence for extra dimensions. People have been looking for a long time. They haven't found any.
So why do they take the idea seriously? Because it's required by string theory. If string theory is accurate, extra dimensions must exist. But string theory also isn't supported by a shred of evidence. They've been searching fo
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Funny, how many real world things work because we can use i in an equation. Seriously - space travel, nuclear power, VLSI electronics . . . George Gamow even showed how the poor sap from Poe's "The Gold Bug" could've found the buried treasure if he'd understood the
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You're talking about math, not science. Math is self contained. It doesn't try to describe anything but itself. You can define any mathematical system you want. Any of them is just as "real" as any other. Most of them don't describe the universe we live in, but that's ok. They're still valid mathematics. Maybe we'll find a use for them some day and maybe we won't. It doesn't matter as far as the math is concerned.
Science tries to describe the world we live in. It tries to identify particular mathem
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Rocketry must seem like magic, eh? All that incomprehensible math to predict orbital mechanics - do you just accept that math because it did something you think is useful, or is space travel just a bunch of malarchy to you?
GPS - the whole reason we were able to invent GPS systems is because that math you don't seem to like predicted the possibility and even made realizing that possibility a reality.
Math is self cont
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Math contains all possible mathematical systems. Science tries to find the one particular mathematical system that corresponds to our universe. It does that through experiment. If a mathematical system doesn't match experiment, it's still fine as far as pure math is concerned, but science rejects it. It isn't the one we're looking for.
"Just" you say (Score:1)
Why not just ask Professor Hikita? (Score:1)
Experiment (Score:2)
"The main advantage of massive gravitons as dark matter particles is that they only interact gravitationally, hence they can escape attempts to detect their presence," Cacciapaglia said.
In other words, no experiment can tell if the theory is a good fit for observation? That is a main advantage for it to succeed, indeed.
Phlogiston (Score:1)