Is Dark Matter's Main Rival Theory Dead? (theconversation.com) 87
"One of the biggest mysteries in astrophysics today is that the forces in galaxies do not seem to add up," write two U.K. researchers in the Conversation:
Galaxies rotate much faster than predicted by applying Newton's law of gravity to their visible matter, despite those laws working well everywhere in the Solar System. To prevent galaxies from flying apart, some additional gravity is needed. This is why the idea of an invisible substance called dark matter was first proposed. But nobody has ever seen the stuff. And there are no particles in the hugely successful Standard Model of particle physics that could be the dark matter — it must be something quite exotic.
This has led to the rival idea that the galactic discrepancies are caused instead by a breakdown of Newton's laws. The most successful such idea is known as Milgromian dynamics or Mond [also known as modified Newtonian dynamics], proposed by Israeli physicist Mordehai Milgrom in 1982. But our recent research shows this theory is in trouble...
Due to a quirk of Mond, the gravity from the rest of our galaxy should cause Saturn's orbit to deviate from the Newtonian expectation in a subtle way. This can be tested by timing radio pulses between Earth and Cassini. Since Cassini was orbiting Saturn, this helped to measure the Earth-Saturn distance and allowed us to precisely track Saturn's orbit. But Cassini did not find any anomaly of the kind expected in Mond. Newton still works well for Saturn... Another test is provided by wide binary stars — two stars that orbit a shared centre several thousand AU apart. Mond predicted that such stars should orbit around each other 20% faster than expected with Newton's laws. But one of us, Indranil Banik, recently led a very detailed study that rules out this prediction. The chance of Mond being right given these results is the same as a fair coin landing heads up 190 times in a row. Results from yet another team show that Mond also fails to explain small bodies in the distant outer Solar System...
The standard dark matter model of cosmology isn't perfect, however. There are things it struggles to explain, from the universe's expansion rate to giant cosmic structures. So we may not yet have the perfect model. It seems dark matter is here to stay, but its nature may be different to what the Standard Model suggests. Or gravity may indeed be stronger than we think — but on very large scales only.
"Ultimately though, Mond, as presently formulated, cannot be considered a viable alternative to dark matter any more," the researchers conclude. "We may not like it, but the dark side still holds sway."
This has led to the rival idea that the galactic discrepancies are caused instead by a breakdown of Newton's laws. The most successful such idea is known as Milgromian dynamics or Mond [also known as modified Newtonian dynamics], proposed by Israeli physicist Mordehai Milgrom in 1982. But our recent research shows this theory is in trouble...
Due to a quirk of Mond, the gravity from the rest of our galaxy should cause Saturn's orbit to deviate from the Newtonian expectation in a subtle way. This can be tested by timing radio pulses between Earth and Cassini. Since Cassini was orbiting Saturn, this helped to measure the Earth-Saturn distance and allowed us to precisely track Saturn's orbit. But Cassini did not find any anomaly of the kind expected in Mond. Newton still works well for Saturn... Another test is provided by wide binary stars — two stars that orbit a shared centre several thousand AU apart. Mond predicted that such stars should orbit around each other 20% faster than expected with Newton's laws. But one of us, Indranil Banik, recently led a very detailed study that rules out this prediction. The chance of Mond being right given these results is the same as a fair coin landing heads up 190 times in a row. Results from yet another team show that Mond also fails to explain small bodies in the distant outer Solar System...
The standard dark matter model of cosmology isn't perfect, however. There are things it struggles to explain, from the universe's expansion rate to giant cosmic structures. So we may not yet have the perfect model. It seems dark matter is here to stay, but its nature may be different to what the Standard Model suggests. Or gravity may indeed be stronger than we think — but on very large scales only.
"Ultimately though, Mond, as presently formulated, cannot be considered a viable alternative to dark matter any more," the researchers conclude. "We may not like it, but the dark side still holds sway."
is gravity a 5+d force? (Score:2, Interesting)
Maybe dark matter exists in a spatial dimension we don't have access to or is hidden. But gravity still interacts with this mass since the gravity field spans all spatial dimensions.
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How would your hypothesis be tested?
What predictions can it make?
The big problem with MOND is that it can't explain why some galaxies have a dark matter halo, and some don't. MOND predicts the same distortion for all galaxies, and that isn't reality.
WIMPs are the best explanation so far.
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I'm not sure it could be tested directly. It's just a hypothesis. But depending on how much these hidden objects interact with gravity it could explain the missing mass of large scale objects like galaxies.
The problems I see with WIMPs is we would have discovered these objects by now. Dark matter pervades the entire universe, they should be everywhere. Even on how weakly they interact surely at high energies something would have appeared.
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How do you make that out?
We've explored a range of particle masses, from the 511keV mass-energy of an electron-positron pair down to the (small) handful of eV for neutrinos (all flavours, though their exact masses are still buried in the fog of measurement noise), and up to the 13.6TeV working energy of the LHC, recognising the Higgs boson at an energy of 125-odd TeV. We've explored in a less-controlled way, the "landscape" up
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WIMPs are the best explanation so far.
Wimps you say? And here I was sold decades ago that I should strive to be more than the 98-pound weakling.
Seems Charles Atlas was full of shit he should have known and recognized was matter.
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How would your hypothesis be tested? What predictions can it make?
The idea that dark matter exists in another dimension is a well-known hypothesis in the field of string theory. The hypothesis does make predictions that modern physicists are trying to verify. Here is an article [quantamagazine.org] which describes some aspects of this hypothesis and what some scientists are doing to investigate it further. I was only a physics undergraduate who ultimately became a software developer, so I won't try and butcher an explanation of this frontier of science.
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How would your hypothesis be tested? What predictions can it make?
The idea that dark matter exists in another dimension is a well-known hypothesis in the field of string theory.
String Theory is even more convoluted and un-provable: it posits that we live in a 10-dimensional multiverse, but, hang on.... we can never actually prove those dimensions exist, so you'll just have to take the word of Very Smart People for that.
Until someone can actually prove something in regard to these airy theories that rely exclusively on exotic equations (that require very strained circumstances to work, even on paper), theoretical physicists may as well be debating how many angels can dance on the h
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Re: is gravity a 5+d force? (Score:5, Interesting)
There is no such thing as gravity. It's just space-time curved by the presence of mass. So we're looking for that mass.
My guess is it will turn out to be something like quantum virtual particles popping in and out of existance. Particle/anti-particle pairs have properties which cancel each other out. Except for mass, which is always positive for both. We can't detect them because they don't last long enough to interact with anything. Or clump together into larger "dark matter" objects.
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There is no such thing as gravity. It's just space-time curved by the presence of mass.
We have observed gravity waves propagating across billions of light-years. So gravity appears to be more than just bent space.
First observation of gravitational waves [wikipedia.org]
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I thought gravitational wave is a ripple in space-time.
Gravitational Waves (Score:5, Informative)
We have observed gravity waves propagating across billions of light-years. So gravity appears to be more than just bent space.
That's exactly what a gravitational wave is: a bend in space-time that propagates.
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There are no "forces", we replaced those with "interactions" long time ago.
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He didn't say that "Gravitational waves don't exist".
No, but he did say "gravity appears to be more than bent space" using gravitational waves as evidence of that when, in fact, gravitation waves are evidence that gravity is exactly a bend in space-time.
Dark Energy not Dark Matter (Score:4, Interesting)
My guess is it will turn out to be something like quantum virtual particles popping in and out of existance.
No, quantum fluctuations like that lead to Dark Energy, essentially the energy of free space and we _REALLY_ do not understand that: if you do the calculations based on what we think we know so far you end up with a cosmological constant over 100 orders of magnitude away from what appears to be the value in our universe.
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While that currently explains gravity perfectly, if the hypothesized graviton is ever discovered, then gravity will be shown to work in the same way as the other fundamental forces via the exchange of force-carrying particles.
Re: is gravity a 5+d force? (Score:4, Informative)
There's nothing particularly different about interpreting general relativity as curved space and the way we describe the rest of the forces. General relativity is a field theory with "curved space" being the gravitational field. Maxwell and quantum electrodynamics are both field theories, and you can give them a similar geometric interpretation if you want.
Einstein apparently didn't like that geometric interpretation, by the way, but non-Euclidean geometry was new and sexy at the time, and a lot of people around Einstein were geometers. The actual "gravitation field == curved space-time" interpretation was promoted by people like Weyl, and then John Wheeler basically taught the entire post-WWII generation of American physicists that specific interpretation.
Einstein said things like:
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I've never heard of an explanation as to how gravitons, if ever discovered, would make it appear as if space really were curved in order to explain all gravitational phenomena including gravitational waves, lensing, and event horizons of black ho
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I've never heard of an explanation as to how gravitons, if ever discovered, would make it appear as if space really were curved in order to explain all gravitational phenomena including gravitational waves, lensing, and event horizons of black holes.
In quantum field theories, as I understand them, "particles" are simply the quantized time-dependent derivatives of the underlying field. In General Relativity, the underlying field is the metric tensor. If you could quantize gravity, "gravitons" would appear as the quanta, but the fact that it's quantized still doesn't mean space is not curved.
Think of a stretched rubber sheet. Tap it, and you get ripples propagating across it, which are moving curvature of the sheet. In QM, those ripples have to be quanti
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The gravitational charge is energy and momentum, so everything interacts with gravitational fields. That universality certainly makes it extra intuitive to describe gravity geometrically. That doesn't make it the only way though. Einstein pointed out that you can describe anything as a combination of geometry and physics and what you put into either category is fairly arbitrary. I think the gravity as space-time interpretation does tend to lead people who insist it is True with a capital T astray though. Th
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I look forward to your publication and subsequent Nobel prize for your successful experiment that violates the equivalence principle.
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I'm afraid I'm not going to get a Nobel prize for that. Notice that I did not say "equivalence principle" I said "absolute equivalence of gravity and acceleration."
The equivalence principle is only true locally, that is, over infinitesimal distances. It is, in fact, fairly easy to tell the difference between acceleration and Earth's gravitational field, even if you are locked in an elevator. You can imagine a completely uniform gravitational field but if you do more than imagine you discover that in order t
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I didn't say I invented it. I believe you accused me of that in the same post where you insisted that acceleration and gravity not being absolutely equivalent is the same as claiming a violation of the equivalence principle.
You also nominated me for a Nobel prize so back then you did think I was super clever I guess? So fickle.
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Einstein apparently didn't like that geometric interpretation, by the way, but non-Euclidean geometry was new and sexy at the time
Yeah, bleeding edge indeed, about a century old at that point.
(a friendly nitpicking; I agree with your point, and would have up-voted it, had I mod points). It just struck me as odd that you're calling non-Euclidean geometry "new and sexy" at the time of creation of the theory of general relativity.
But granted, the analogy between the model of gravity and a model of "curved space-time" looks sexy, in a way, and science popularizers sure loved it.
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Give or take a couple of millennia. Simply describing it as "non-Euclidean" means someone has looking at Euclid's axioms, and wondering "what if?"
By the time that calculus and projective geometry were around, and in particular the routine use of complex numbers (for example, in infinite series for calculating trigonometric ratios and constants like pi and e) - which really challenge the algebraic interpretation of geometry - people were starting
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Well, when you're overturning Newton and Euclid, 60 or 70 years since Riemann gave his lecture is pretty new, and nonlinear geometry work that's become synonymous with General Relativity was going on right up until after Einstein published his first paper.
New and sexy depends on the field. Arguably, Clifford algebra has been new and sexy in some corners of physics over the last twenty years, despite being named after a guy who died in 1879.
Re: is gravity a 5+d force? (Score:2)
Wasn't this just a mathematical trick? Kind of like spherical coordinates, a pinch to make numbers seem more "straight" when viewing the problem through this pair of glasses rather than the "intuitive" cartesian one?
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This is an untestable philosophical interpretation. There are other interpretations, which produce similar practical results without "singularities" and other non-physical artifacts arising left and right in the calculations.
So who knows.
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To be pedantic, both mass and energy will curve spacetime. Pack enough energy into a small space, and you'll have the same effect on space-time as the equivalent E=mc^2 mass. If you impart energy into a spring by stretching it, you are in fact making it ever-so-slightly "heavier" - more massive. Same with charging a battery - the stored electrical potential energy will make a charge ba
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OK. I get that. But dark matter curves space-time inwards (toward the center of mass). Making that responsible for the anomalous rotation of galaxies and other stuff. Dark energy has been hypothesized as that which makes galaxies accelerate away from each other. Sort of like anti-mass. But that's not supposed to exist [wikipedia.org] in the particle/anti-particle duopoly.
If it is possible to have anti-energy and as a result anti-mass, then that would require an energy deficit at other than quantum distances to make the un
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So - exactly like "bright" matter. Which - from a gravitational point of view, is exactly correct. Dark matter has the same effect on gravity as normal matter - it's oddity is twofold : that it doesn't produce as much light as a similar amount of "bright matter" (baryonic matter), and it seems to interact less with electromagnetic radiation than"bright matter" in other ways then generating EM radiation. Which also - automatically - means
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Gar. Voted up by the Dunning Krugers who don't understand dick about physics. "You see the scientists are so STUPID because I'm smarter!" I can't even begin to dissect everything wrong with this post.
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Classical Newtonian gravity lends itself particularly well to a 3D world because of the "inverse distance squared" factor. An extra dimension would "dilute" gravity, making it weaker over long distances (1/r^3 instead of 1/r^2), but to explain the movement of galaxies, gravity has to be stronger over long distances, not weaker.
Putting dark matter in the extra dimension requires not only a hypothetical kind of matter, but also to explain how gravity acts on that extra dimension while still being 1/r^2 in the
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One can only hope (Score:2)
Re:One can only hope (Score:4, Interesting)
MOND is a hack.
WIMPs are also a hack.
The problem with MOND is not its hackery but its failure to explain observed reality.
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MOND is a hack.
WIMPs are also a hack.
The problem with MOND is not its hackery but its failure to explain observed reality.
Referring to my analogy, the 19th century might have been able to account for the shift of Mercury's perihelion, while failing elsewhere. It would nevertheless have remained a hack. MOND was always a hack as well, which helped explain the observed anomalous galaxies rotation. It is just that it has become obvious that outside that it makes incorrect predictions. Which confirms that it is nothing but a hack, rather than good science.
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WIMPs are also a hack.
We already observe weakly interacting particles that have mass, neutrinos. They are so prevalent they are everywhere. They only interact through an unlikely interaction with the weak force, so only at very short distances, to the point they are nearly unobservable. It’s not a hack at all to consider there may actually be much heavier, and thus slower, neutrino like particles just with substantially more mass and a right handed nature.
Re: One can only hope (Score:3)
Re: One can only hope (Score:4, Interesting)
Dark matter has a bunch of useful predictions.
a) if it's matter then it can move about like matter. You can't observe it directly in the electromagnetic spectrum, but you can see it's gravity lensing effect, so you should be able to see how it's distributed.
b) if it's "dark" then it's got to be different from normal "light" (shiny) matter. In particular it shouldn't move around due to electromagnetic interactions.
There are useful predictions that come out of that. For example, there's the idea that most galaxies will have dark matter more or less proportional to their size, however maybe if galaxies crash into each other or something else, the dark matter could be lost and separated from it's host galaxy. That would lead to some galaxies that seem identical having different amounts of dark matter and you could see that by seeing different amounts of gravity lensing by galaxies of the same size and visible weight.
Once you start making specific proposals for what dark matter is (neutrinos? WIMPS? primordial black holes?) you get a bunch of new predictions. For example if all of dark matter was made up of black holes, then wouldn't they occasionally eat a star or a planet or something?
N.B. mostly amateur interest, don't assume what I say is greatly right. If anyone enlightened wants to say more that would be great.
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For example if all of dark matter was made up of black holes, then wouldn't they occasionally eat a star or a planet or something?
tiny black holes on the scale of a solar mass or less are incredibly dense compared to normal matter, even degenerate matter like neutron stars. They have so much kinetic energy in such a tiny cross section that passing through anything like a planet is less of an effect than a high powered rifle round through a single piece of tissue paper. The average relative speeds of objects in the galaxy, or solar system, means that it’s extremely probable there will be a massive velocity difference and as s
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That one has been pretty dead since the late 1980s. People have been looking for the flashes produced by such objects in the galaxy (against a background of more distant parts of the Galaxy since the early 1980s. They have been seeing occasional such flashes - but not enough to provide the mass necessary to account for the Galaxy's anomalously fast rotation. Whatever the "missing mass" is, MAssive Compact Halo Objects (MACHOs, to name one of the searches ; I forget what "OGLE" - anoth
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MOND may be a hack, but dark matter isn't even a theory. It's nothing more than an observation that something is wrong with our current theories..
No, dark matter is a hypothesis that explains an observation.
The observation to be explained is that the motion of the matter that we can see is not explained by the gravity of the objects we can see.
The hypothesis is that the parts of the motion that aren't caused by the objects we can see is caused by the gravity of things we don't see.
A reasonable hypothesis, keeping in mind that "reasonable" is not the same as "right." It has been right before: the existence of Neptune, for example, was predicted by the
Nice - a counterexample to Betteridge's law (Score:5, Interesting)
Well, I guess they didn't ask *should* dark matter's main rival theory be dead. The answer to that is most definitely yes, in my opinion.
Here's the thing. It's not like it's just galactic rotation curves that give evidence for dark matter. Watch this video (fast forward to 2:36 if you don't want the intro) to see a list of observational evidence explainable by dark matter: https://www.youtube.com/watch?... [youtube.com].
We know almost for sure that dark matter exists because it does so many things other than just explain the galactic rotation curves. We can see gravitational lensing from dark matter clumps. Check out the bullet cluster, where the non-dark matter seems to have collided but the dark matter sailed on through. The power spectrum of fluctuations in the cosmic microwave background fits the dark matter hypothesis. The list goes on: https://en.wikipedia.org/wiki/... [wikipedia.org]. Mond could not explain even half of these items; dark matter existing would explain each of them.
Is it possible that there's dark matter and also Mond? Maybe, if Mond is so weak it makes indetectible perturbations. However, it hard even to write down a theory of Mond that respects special relativity. (Mond typically says to strengthen gravity for any acceleration below some cutoff value, but making that cutoff value observer-independent isn't all that easy to do.). Mond was a really cool idea and I wanted it to be true when I heard about it in 2003. Unfortunately the evidence just isn't there, and dark matter is more or less undeniable at this point.
The big question is what dark matter is made of, and the most boring (read "probably correct") hypothesis out there is that dark matter is made of axions (https://en.wikipedia.org/wiki/Axion). The strong force seems to obey CP symmetry precisely - every experiment you can do that involves just the strong force looks identical whether you use regular matter or a mirror-image setup made of antimatter. The symmetry is so precise, it's kind of like walking into a room and seeing a pencil balanced on its tip on the table. Frank Wilczek and Steven Weinberg asked: suppose there's an invisible string on the eraser end of the pencil holding it up. What properties must that string have? It turns out that not only would the candidate particle (they called the axion) solve the strong CP symmetry problem, it would also be a weakly interacting particle that would have been made in just the right abundance in our early universe to account for the mass of dark matter we observe today. We haven't found axions directly yet, but it does feel like the puzzle pieces of dark matter and CP symmetry could fit together.
Betteridge and WIMPs etc (Score:4, Interesting)
The big question is what dark matter is made of, and the most boring (read "probably correct") hypothesis out there is that dark matter is made of axions
That's certainly one hypothesis but I woud hardly define it as "probably correct". WIMPs are definitely still very much a possibility and, I would argue just as likely especially with the discovery of the Higgs that could lower the cross-sections further without requiring any new particles other than DM itself. The other intriguing possibility is that DM is made up of primordial black holes. LIGO is rapidly exploring this hypothesis and I believe cosmologists could not explain where they came from if they are found in the remaining areas of phase space bur the aluring thing about this explanation is that it requires nothing new in terms of particles.
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We know there's a massive asymmetry regarding matter and anti-matter at the Big Bang. I wonder if the presence of dark matter and energy balances that anomaly.
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We know there's an infinitesimal asymmetry which left the universe with one baryon+lepton for every several billion photons after hadronization occurred and 99.9999999% of the resulting matter and antimatter annihilated.
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MOND was never a viable theory, it was zombi theory almost from the day it was proposed because it was concocted to explain away only one class of observations - the unexpectedly fast rotation of galaxies - but couldn't even do that as it could not explain the velocity dispersion. So it stumbled out of the gate, and should have been put down then. Actually it was -- it never gathered more than fringe support. But this overwhelming disproof of the notion should drop it from discussion entirely.
Dark matter isn't so exotic (Score:1)
Re:Dark matter isn't so exotic (Score:4, Interesting)
Dark matter could also be tiny black holes
There are plenty of reasons to believe that is not true.
Tiny black holes are not stable.
If tiny black holes are stable (because physics doesn't work the way we think), then some of them would merge or grow into medium-sized black holes. Yet there are ZERO observed black holes below 3.3 solar masses, the minimum size from collapsed stars.
If there were trillions or quadrillions of tiny black holes in our galaxy, 30 times the mass of all the stars, we would see signs of them everywhere, yet we see them nowhere.
Tiny black holes? [Re:Dark matter isn't so exotic] (Score:2)
Dark matter could also be tiny black holes
There are plenty of reasons to believe that is not true. Tiny black holes are not stable.
No, more specifically, there is a size below which tiny black holes decay. Above this size (about 10^8 tons) black hole decay takes longer than the lifetime of the universe. That's a diameter of about 3E-13 meters, or 0.003Angstroms, still tiny by any reasonable meaning of "tiny".
If tiny black holes are stable (because physics doesn't work the way we think), then some of them would merge or grow into medium-sized black holes.
Not entirely clear. Their cross-sections will be incredibly tiny, and their gravity is only a factor at very short distances.. I'd want to see a calculation before I'd have confidence that they'd merge and grow
Yet there are ZERO observed black holes below 3.3 solar masses, the minimum size from collapsed stars. If there were trillions or quadrillions of tiny black holes in our galaxy, 30 times the mass of all the stars, we would see signs of them everywhere, yet we see them nowhere.
Probably correct, but
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Assuming you're the Geoffrey.Landis your screen name purports, I'm similarly going to assume that your quite specific limit refers to the size at which the temperature (well, spectrum) of the radiation emitted has a similar flux to
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Assuming you're the Geoffrey.Landis your screen name purports, I'm similarly going to assume that your quite specific limit refers to the size at which the temperature (well, spectrum) of the radiation emitted has a similar flux to the CMB, so that at larger sized, the CMB delivers mass-energy to the BH, and at smaller sizes the BH delivers mass-energy to the rest of the universe.
In which case, that's a moving target. Slowly moving, but moving nonetheless.
Yep. If Hawking is right, black holes don't live forever.
A very very very very long time... but not forever.
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I think the large majority of astrophysicists accept this. Not because it's Hawking's idea, but because his arguments are solid.
The second point - that the impact of the CMB (and "local" conditions) on a BH's event horizon will mean that BHs with a mass above a certain limit (and so, effective temperature of their event horizon below a certain value) are not shrinking at the moment, while smaller BHs are shrinking (by radiating into the CMB and their
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Neutrinos were hypothesised in the 1930s to provide a "classical" fudge factor in a reaction that was expected to be fully quantised. Further observations showed that a "neutrino" (IT: "little uncharged one") would also balance the angular momentum in a number of reactions involving charged (viz: easily detected) particles, which would have made them that much more useful.
But neutrinos weren't detected (and filled a substantial
Disingenuous (Score:5, Insightful)
MOND is a class of hypotheses.
This article is motivated reasoning committing unforgivable composition error.
What a scientist does is test each hypothesis separately and see how theory and data correlate.
What a propagandist looking for funding does is throw out the scientific method to favor his friends.
One MOND hypothesis being ruled out is /progress/.
Since Supersymmetric approaches are obviously not bearing fruit, all options should be on the table.
Even 'stretchy entanglement', non-Mach event horizons, and other odd non-DM, non-MOND hypothesis.
Dishonest tribal people should be excluded from science funding.
Let's Call it Undead Then (Score:3)
As we all know the sequels are almost never better than the
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To be fair, something similar can be said for dark matter - *what* dark matter is has many explanations.
And in favor of the dark matter theory, some of the explanations for what dark matter is could be very plausible - some have theorized that at least part of what is termed "dark matter" could be objects such as black holes and brown dwarfs that we aren't accurately measuring. Let's just call this the "boring dark matter" for the sake of discussion.
I actually favor "bo
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Dark Matter research is powered by Dark Funding :-)
"Look, it's full of models!" (Score:5, Interesting)
What "model"? There is no "model" that accounts for all the observed data, what we have is a model that fails to explain all our observations, then essentially just gives a name to the bits we can't account for. Then to confuse things further for the layman, somebody decided to use the name of a concrete object for this imaginary one, and then claims that 85% of the universe is made up of it! Fi, "dark matter", that's a terrible name. What is actually being described is just plain lack of knowing, an informed ignorance. It is neither "dark" nor "matter".
I would suggest the word, "theory" instead of "model". It is perfectly fine to tell people we just don't know something, even if that something is important. "We can't explain why the universe is expanding yet. The old theories don't exactly fit, and the new ones don't either."
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Great post. "Dark matter," is a misnomer. It's "invisible gravity." Also, "dark energy" is "invisible energy." The corelative math suggests that both are related to the asymmetry of particles and anti-particles at the Big Bang.
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What "model"? There is no "model" that accounts for all the observed data, what we have is a model that fails to explain all our observations,
Despite other posters praising this - it is not a correct description of the situation, though challenging the original poster for referring to a "standard dark matter model" has some basis, given that we do not now have a theory of what comprises dark matter. The observational data matches matter that has mass, and acts in an entirely normal way gravitationally, but interacts with normal matter and itself in no other way. This descriptive behavior appears to match all observations, and thus far all anomalo
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The word theory is already in use. A theory is a model that has been shown to provide accurate predictions in a wide variety of cases. Both Newton's and Einstein's models of gravity have reached the status of scientific theory.
What we need is a new model that predicts everything accurately predicted by Newton and Einstein, and is able to make accurate predictions of things Newton and Einstein fail at. We don't have that yet: Einstein's is still the best we have, so that's what we keep using until something
Pre-existing curvature in the universe. (Score:4, Interesting)
The universe seems to curve in ways that observable matter and it's mass can't explain. Examples are the accellerating expansion and galaxies sticking together despite appearing to spin too fast. The explanaion is that something else curves space.
The universe seems to act like a 4-dimensional bubble rising to a surface, with lots of smaller bubbles clinging to it's outside and denting the interior. As it gets closer to the surface, pressure drops and the bubble expands. It's a matter of the pressure gradient. Within the bubble, galaxies concentrate around the dents.Sometimes enough matter concentrates that it tears off and forms a bubble of it's own (black holes).
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The universe seems to act like a 4-dimensional bubble rising to a surface, with lots of smaller bubbles clinging to it's outside and denting the interior.
So God does not play dice, but God takes bubble baths?
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"dark matter" is admission that modeling everything in the universe based on our understanding of gravity does not work
add: ...unless there are things in the universe other than those we can currently observe.
Dark matter is fake (Score:2)
Dark matter is fake, and MoND is wrong. Quantized Inertia is correct. A new book on the subject is being published this month.
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May be he/she means, a scientific paper the size of a book?
Heads 190 times in a row? No big deal! (Score:2)
I mean, once you've got 189 in a row, your odds of getting to 190 is 50/50.
Shot in the dark (Score:1)
Right now the theory is there is some matter that is unobservable by normal metrics but is indirectly observed by how gravity is interacting at large scales.
What is the "resting point" of spacetime? Does that make sense? Is that a thing that can be distinguished? We assume that there is dark matter curving spacetime but do we have an actual reference for spacetime at rest? Is this akin to the "MOND" theory tha
We can create and detect dark matter (Score:2)
"And there are no particles in the hugely successful Standard Model of particle physics that could be the dark matter — it must be something quite exotic."
They mean dark matter particles that aren't neutrinos. We can create and detect neutrinos, the only known dark matter particle so far. Dark matter isn't dark because it's mysterious as asshole journalists love to imply, it's dark because it doesn't reflect light. And it doesn't reflect light because it doesn't interact with electromagnetism, which a
Re: (Score:2)
It's "dark" primarily because it neither emits nor absorbs light.
I still don't quite understand (Score:2)
Why can not the missing mass that being called dark matter be photons. I mean they have mass while moving, and there is a lof of it out there, and it's interaction is low, etc.
Re: (Score:2)
Because we would detect them, and they do not have the correct behavior of not interacting with normal matter.