When it comes to dark matter, the mysterious substance that makes up the vast majority of the mass in the Universe, there’s a whole lot we don’t understand or know about it. You might think that there are so many unknowns that are so huge that — quite reasonably — perhaps it doesn’t exist at all, and there’s some other explanation for the behavior of masses on galactic scales and up?

Image credit: NASA/ESA/Richard Massey (California Institute of Technology).

Image credit: NASA/ESA/Richard Massey (California Institute of Technology).

And yet, you can’t make that leap unless you’ve honestly (and scientifically) considered the full suite of evidence and facts that speak to the question of dark matter’s existence.

What about galaxy collisions? Cluster collisions? The fluctuations in the CMB? Large-scale clustering? Baryon acoustic oscillations? And so much more?

Image credit: ESA / XMM-Newton / F. Gastaldello (INAF/IASF, Milano, Italy) / CFHTLS.

Image credit: ESA / XMM-Newton / F. Gastaldello (INAF/IASF, Milano, Italy) / CFHTLS.

Sabine Hossenfelder does exactly this, and invites you to join her as she reviews 10 facts everyone should know about dark matter!

Comments

  1. #1 Ragtag Media
    What's a mata U
    July 28, 2015

    Hmm, “Since dark matter doesn’t interact much with itself and other stuff, it’s the first type of matter to settle down when the universe expands and the first to form structures under its own gravitational pull. It is dark matter that seeds the filaments along which galaxies later form when visible matter falls into the gravitational potential created by the dark matter.”

    See that Raskolnikov ?

  2. #2 Dick Dolan
    U.S.A.
    July 28, 2015

    Some researchers have suggested that dark matter could be a result of incomplete decay to ordinary matter of the oscillatory energy at the end of inflation. This seems reasonable. What has become of this idea? You don’t even mention it.

  3. #3 Wow
    July 29, 2015

    “Some researchers have suggested that dark matter could be a result of incomplete decay to ordinary matter of the oscillatory energy at the end of inflation”

    No mechanism, no reason to need it to happen.

    Conjecture only, and unsupported.

    This is why it isn’t even mentioned. Because it’s not worth mentioning.

  4. #4 Boris Borcic
    July 29, 2015

    Long shot, but on dark matter not possibly being formed of neutrinos, I’d like to be shown that a Fermi gas of (slightly massive) neutrinos can’t achieve dark matter density. IOW, couldn’t our acquired wisdom about a thermal distribution of neutrinos be defeated if inflation left the universe saturated with cold neutrinos? I mean, common sense knows that expanding gases cool down, so couldn’t to inflation – the most extreme case of expansion – be attributed to produce frozen things that would otherwise be unimaginable?

  5. #5 Wow
    July 29, 2015

    We have no mechanism that would produce that huge a number of neutrinos, Boris.

    See the Wikipedia on neutrinos for an introductory course on the methods of production.

  6. #6 eric
    July 29, 2015

    Fact 1 is kind of an implication of fact 5. If particles don’t interact with each other or other particles, they can’t form systems. Which means they can’t form excited state systems that would de-excite via release of a photon.

    If DM particles are some sort of boson, we might still see photons as a secondary result of pair production (i.e., DM rare interaction with some other particle -> pair of other elementary particles -> annihilate to produce photons). So I assume this means DM can’t be any form of boson, either.

    So, if they’re leptons, is there any way to detect them via their half integer spin?

  7. #7 Denier
    United States
    July 29, 2015

    DM Fact #11 that everyone should know: The required distribution of DM in a spiral galaxy needed to account for the observed spin rate is ridiculous.

    The way I had heard this described is imagine you were walking across a room with a box full of legos and you tripped. The legos go flying through the air and just happen to fall into the form of a perfectly built castle. It is not technically impossible, but the chances it actually happening are ridiculous.

    Before I get dismissed as a crackpot, know that Ethan right here on this blog has admitted this problem. This issue is the one and only thing MOND does better than DM. I am not saying MOND is correct, but the huge problem is something DM supporters (other than Ethan and very much to his credit) conveniently fail to mention.

  8. #8 Steven Maricic
    NJ, United States
    July 29, 2015

    I’m not a scientist but I have a theory about gravity. Maybe the gravitational attraction between two masses, A and B, is somehow strengthened by either of these:
    1. other nearby masses (C, D, E, etc.)
    2. electromagnetic radiation from stars.
    Maybe the presence of mass C (and D and E) does something to the space between A and B — excites it somehow, allowing more gravity to “flow” between A and B.
    The same might be true of, say, the intense electromagnetic radiation at the heart of each galaxy.
    Could gravity be “super-stimulated” the closer one gets to the center of a galaxy where large stars and planets interact at all angles? Could this be the explanation — instead of “dark matter” — for the ability of galaxies to hold together even as they spin at high speeds?
    As the space between galaxies expands, could the gravity tying one galaxy to the others weaken exponentially? Could this be the explanation — instead of “dark energy” — for the acceleration of the expansion?
    My theory could be tested in this way:
    1. measure the gravitational attraction between two equal masses (A and B) that are level with each other and , say, one meter apart.
    2. now place an equal mass C close by in the same horizontal plane.
    3. measure the attraction between A and B once more. Has it changed?
    4. take similar measurements in rooms with little electromagnetic radiation and lots of such radiation.

  9. #9 Wow
    July 29, 2015

    DM Fact #11 that everyone should know: The required distribution of DM in a spiral galaxy needed to account for the observed spin rate is ridiculous.

    Nope, that’s not a fact.

    That’s an opinion.

    Yours, in fact.

    It’s a fact you got that hellaciously wrong.

    Please try again. Or, rather, please don’t

  10. #10 Wow
    July 29, 2015

    I’m not a scientist but I have a theory about gravity.

    Then write it up and put it in a journal.

    It’s almost certain you’ve got it wrong, but exactly how or where (or the remote chance you have something) will only be found if you detail precisely your thesis.

    Your post here hasn’t managed to do that, so any criticism of your claims is going to be on the vague and imprecise claims you’ve made here.

  11. #11 Sinisa Lazarek
    July 29, 2015

    @ Steven #8

    You needn’t be a scientist to think some more on your proposal. Calculate the gravitational attraction of two bodies that can fit in a room placed one meter apart. That’s high school. Just use plain newton gxm1m2/r^2. then see if something like that is detectable.. then place a third object.. then calculate again… then turn the lights in the room and the radio, then measure again… doesn’t really require scientists at all, you can do it yourself really.

  12. #12 Cubedmass Seige
    UK
    July 29, 2015

    I’m no academic however I find your fact interesting.
    There appears to be another everything from nothing and I thought the singularity of big bang was the only one.
    I assume the dark matter that is indicated to exist is a sub-atomic partical and is not covered by classical mechanics,
    but by quantum mechanics.
    This must offer some hope, why?
    Classical Mechanics and the current mathematical system both except nothing as a possibility.
    Quantum mechanics and compound mathematics system
    does not except nothing as a possibility.
    Quantum ” the smallest amount ot energy able to cause change to a physical structure”.
    A physical structure must contain a unique amount of energy
    stored as mass or matter within a unique area of space at a
    unique point or period of time.
    This physical structure must be unique because it must be singular. It can only exist in one area of space at one point or period of time, and cannot change unless a second energy source is able to influence it.
    mass must cause contraction
    matter must cause expansion
    This very simple fact is the basis of Compound mathematics.
    Every action or interaction caused by energy must involve expansion or contraction.
    At a latter point in time at the point of interaction you must ether
    a new smaller dencer structure.
    or
    a new larger more fluid structure.
    understand this and the singularity and nothing cannot exist.
    cudedmass

  13. #13 R. Merito
    July 29, 2015

    True energy is dark matter. Consider our own bodies, if one looks the very vains are dark in color. Dark matter within all of us. Window to our souls is the eye. Although different color eye exist , the inner eye,the pupil, is dark matter. In the beginning , darkness, then a voice called from within it. Furthermore, Einstein was wrong in his understanding that light travel is the fastest , even light takes a measurable amount of time to cross it distance threw dark matter. Also , black holes generate this matter , keeping all things balanced. More study in newtrons would reviel the importance. And has not anyone considered the poles where it is said to be ozone holes? I say these are not holes , this is the radiation that will not vent out to the dark space. These are not holes but consentratoin of our radiation poison. Things that will not combine are either the same or alien to each other. All the energy needed is created from the bubble we live in , pushing threw this dark matter. The static created in the outer atmosphere would bring understanding if looked closer looked at.. These are only my thoughts as I understand !! Resources to prove these are far from me. Finally if you look straight at the sun it is not bright as our atmosphere shows it . it is dark black like the window to our souls. All is this dark matter. Not energy as we understand.
    .

  14. #14 Joshua W Davies Jr
    Cold Spring, New York
    July 29, 2015

    A segment of infinite pure energy is a quantum of it as an energetic whole. An energetic whole is a finite volume of mass that is filled with a metabolic cycle in the here and now. The metabolic cycle can be subdivided into equal and opposite segments of variable densities that fill its energetic whole with its same finite volume of mass as it’s segment of infinite pure energy. Human beings as inertial observers exist in the space time frame of a plane of reference that is restricted to within the event horizon of light’s finite speed. Our sensory perception of the energetic whole is the gross impression of finite volumes within our universe.
    As inertial observers we exist at a point within the vortex of our energetic whole. Everything that we see is relative to that point whether it be past, present or future, big or small, or fast or slow. The here and now however of the entire metabolic cycle is the same as its finite volume of mass equivalent to its quantum of infinite pure energy.

  15. #15 Joshua W Davies Jr
    July 29, 2015

    Dark matter is nothing more than finite volumes of mass that is beyond the ability of our senses to perceive. Matter is another term for human perception of mass whether as particles or as finite volumes of inertial or moving mass.

  16. #16 Michael Hutson
    United States
    July 29, 2015

    What limit does (un)observed gravitational lensing place on the clumpiness of dark matter?

  17. #17 Joshua W Davies Jr.
    USA
    July 29, 2015

    Obviously, the clumpiness observed in dark energy is caused by its gravitational attraction towards other finite volumes of dark energy to give it a significant amount of mass even to attract light energy that we can see within our plane of reference in the metabolic cycle of our energetic whole.

  18. #18 Wow
    July 30, 2015

    “True energy is dark matter. Consider our own bodies, if one looks the very vains are dark in color”

    Oh dear. Pseudoscientific crap wordsalad.

    No. Wrong conclusion, wrong reasoning, fatuous evidence.

    “Einstein was wrong in his understanding that light travel is the fastest ”

    Ridiculous preening. No evidence given other than wordsalad woomancer tract.

    “Also , black holes generate this matter ”

    Yeah, right. You’re just trolling.

  19. #19 Wow
    July 30, 2015

    “Dark matter is nothing more than finite volumes of mass that is beyond the ability of our senses to perceive”

    No it isn’t.

    Are you a godbotherer trolling too?

    Hell, are you another sock of raggie?

  20. #20 Wow
    July 30, 2015

    “mass must cause contraction
    matter must cause expansion”

    Nope. More rubbish, assumption: godbotherer trolling.

  21. #21 Boris Borcic
    July 30, 2015

    @wow what mechanism we have (and wikipedia describes) of relic neutrino production involves reasoned assumptions that are uncertain. OTOH the discovery that neutrino are massive entails a physical possibility of principle that could not be contemplated beforehand, that of neutrino “ice” or more precisely a degenerate fermi gases of neutrinos. How it could originate and what it would look like are distinct matters, as is distinct the matter of establishing that deep-frozen neutrinos couldn’t produce the appearances we label “dark matter” from establishing that the neutrinos can’t be that cold. Before what’s acknowledged to be a mystery, I don’t perceive as completely sound a refusal to explore the former question in the name of a solution to the latter question that’s less than perfectly certain.

  22. #22 Wow
    July 30, 2015

    “@wow what mechanism we have (and wikipedia describes) of relic neutrino production involves reasoned assumptions that are uncertain”

    Ah, Judith Curry is the current master of “Playing the Uncertainty”.

    However, you overplay it. Just like Judy.

    Also, unlike your avowed intent to play on uncertainty, there appears no uncertainty that it’s possible. That is no different than Russel’s Teapot.

    Just because a statement can be made doesn’t mean it can be possible.

    Please insert brain before trying again.

  23. #23 Boris Borcic
    July 30, 2015

    @Wow The discovery that neutrinos are massive entails a physical possibility of principle that could not be contemplated beforehand, that of neutrino “ice” or more precisely a degenerate fermi gases of neutrinos. How it could originate and what it would look like are distinct matters, as is distinct the matter of establishing that deep-frozen neutrinos couldn’t produce the appearances we label “dark matter” from establishing that the neutrinos can’t be that cold or abundant. Before what’s acknowledged to be a mystery, you might perceive as reasonable a refusal to explore the former question in the name of a solution to the latter question that’s less than perfectly certain, but that doesn’t justify jerking yourself off over the first word you can find as a pretext to not address what people say.

  24. #24 Wow
    July 30, 2015

    Nope, it doesn’t allow for “ice”.

  25. #25 Boris Borcic
    July 30, 2015

    Jerking yourself off over the first word you can find as a pretext to not address what people say is really bad practice. Neutrinos are fermions, and therefore obey a Fermi-Dirac statistic – look up Wikipedia – and a degenerate Fermi gas of neutrinos is definitely conceivable.

  26. #26 Wow
    July 30, 2015

    However, if I stop looking at your words because you think that is “jerking yourself all over”, your posts come to:

    “”

    Nothing.

    So, yes, I know neutrinos are fermions and by definition therefore obey fermi-dirac statistics.

    This doesn’t change the fact that this in no way supports your claims. Your claims are not based on those facts, they are irrelevant.

    Your claims are completely orthogonal to the categorisation of fermions, since their categorisation DOES NOT mean there are thousands of times as many of them as possible.

    Nor does your claim about “neutrino ice” come from the fermion nature of neutrinos.

    So, either I take your words and find that they’re complete and utter wank, or I don’t in which case you’ve said bugger all.

    And since quoting you creates so much mental pain in you, I won’t bother any more. It’ll be up to you to work out what I’m counterpointing and debunking.

  27. #27 Wow
    July 30, 2015

    Boris, there’s no need to give wild ass guessing a titwank just so you can pretend to know science.

    Try working out the science first and find what is supported.

    Otherwise you’re just going “But there COULD BE Russel’s Teapot!”.

    But I guess you’re another godbotherer making shit up to drown out the intelligence that is an anathema to blind faith.

  28. #28 Boris Borcic
    July 30, 2015

    Since you don’t provide a first name, so I’ll just call you Trouduc. Trouduc, I made no claim and certainly no claim of a form to which your spunk would apply. But to observe that, you’d have needed to read what I wrote (as opposed to skim it for pretexts of your own self-assertion).

  29. #29 Boris Borcic
    July 30, 2015

    Incidentally, since we observe that the vast majority of the mass of the universe is from stuff we can’t identify, and since this mass belongs to the output of the Big Bang, doesn’t this entail that the models we have of processes occurring during the Big Bang, deserve to be taken with a grain of salt?

  30. #30 eric
    July 30, 2015

    Boris @25:

    a degenerate Fermi gas of neutrinos is definitely conceivable.

    When you say ‘ice’, I immediately think of the high pressure/gravitationally compact type of degenerate Fermi gas, like a neutron star. There doesn’t seem to be any evidence of those sorts of DM degenerate Fermi gasses. The galaxy lensing observations would seem to argue against such things, because those haloes are extremely disperse.

    But degenerate can also refer to low temperature states. I guess that’s a possible form of DM (though I will happily stand corrected if an expert comes along and tells me that ‘no DM can’t possibly be that). But I’m not sure how the ‘ice’ label applies, because all the particles are so disperse and non-interactive that they don’t resemble any sort of solid phase anything.

  31. #31 Joshua W Davies Jr
    United States
    July 30, 2015

    Dark matter is that portion of the finite volume of mass that fills the metabolic cycle of our energetic whole with finite energetic volumes that are beyond the ability of an inertial observer’s sensory perception. We are aware of the presence of dark energy only by its gravitational lending of visible aggregates of mass within our own plane of reference of the metabolic cycle that fills its energetic whole with a finite volume of mass in the here and now.

  32. #32 Ragtag Media
    July 30, 2015

    “Are you a godbotherer trolling too?”
    Are you receiving psychiatric treatment for your monomania?

    “Trouduc”
    Well, that’s a new one for “it” to be called.

  33. #33 Wow
    July 30, 2015

    “Since you don’t provide a first name, so I’ll just call you Trouduc”

    Since you are a dumbass, I’ll call you dumbass.

    So, dumbass, you’re wrong. There isn’t a method that will produce enough neutrinos for it to be dark matter without producing a shitload of other stuff.

    Whether they’re fermions, whether they have mass. Both those claims are irrelevant. They in no way shape or form indicate anything that would make more of them appear.

    So, no, your titwank to uncertainty isn’t going to make uncertainty do what you want, it’s only going to make a mess on you.

  34. #34 Wow
    July 30, 2015

    Yes, but you don’t seem to be condimenting your “idea” (for want of a better word), dumbass.

    No salt applied on your idea.

  35. #35 Wow
    July 30, 2015

    Josh, all I read there was “blah blah blah”.

    Words that meant absolutely nothing. Try with some meaning to them, rather than string blather together.

  36. #36 Wow
    July 30, 2015

    eric, #30, there;s nothing about degenerate fermi gas that means we have enough neutrinos to make the mass up.

    There’s nothing there more than a Russel’s Teapot claim.

    After all, we DO know that teapots exist, right? So one COULD exist orbiting Jupiter, right? And we know that something at the trojan will stay there a long time, right? So therefore there COULD be a teapot orbiting Jupiter at the Trojan!

    See, just because you can make a claim that something can possibly exist, it doesn’t mean that it can actually have a possibility.

    Any more than “it’s possible there’s a teapot orbiting Jupiter” means it’s actually possible.

  37. #37 Joshua W Davies Jr
    USA
    July 30, 2015

    Infinite pure energy is omnipresent and dimensionless. A segment of its steady state is a quantum of it as an energetic whole in the here and now as a finite volume of mass. A metabolic cycle fills its energetic whole in the here and now with events some of which as inertial observers we can observe providing they are within our plane of reference.
    Our plane of reference within the metabolic cycle is limited to within the event horizon of our sensual perception of light’s finite speed. The few events that we can observe are relative to one another within a space time frame of reference.
    As I have mentioned, all that we can observe within the whole of the metabolic cycle is what we observe based on our sensory perception that is our plane of reference within the metabolic cycle of its energetic whole as the energetic expressions of the finite speed of light. Light energy is not reflected off dark energy (matter) within our space time of reference. The only way that we know of its existance is by a greater energetic center of gravity relative to its finite volume of mass that is attractive to lesser volumes of mass within our own plane of reference within the metabolic cycle of its energetic whole.

  38. #38 Wow
    July 30, 2015

    Yup, still meaningless blather.

  39. #39 PJ
    Perth, west Oz
    July 30, 2015

    @37

    Que ??? |(

  40. #40 eric
    July 30, 2015

    Wow @36: you seem to be violently agreeing with me.

  41. #41 Ragtag Media
    July 30, 2015

    Yes eric, by default it has to agree with you because it knows that a Russel’s Teapot is MUCH MORE easier to create in an uncontrolled environment of chaos than a planet with living beings that contemplate their surroundings and relate to them as I am.
    Next?

  42. #42 Wow
    July 31, 2015

    “Wow @36: you seem to be violently agreeing with me.”

    Not really, eric. We’re probably talking past each other here if this is your conclusion.

    Your comment @30 is correct in the limited sense that there’s nothing stopping a fermion losing so much energy as to place itself into a condensed state (indeed this is what I took to be dumbasses’ statement on “ice” to be), but this doesn’t mean that neutrinos can drop low enough to form it and has ABSOLUTELY BUGGER ALL to do with there being enough of them to be dark matter.

    You may, in your lack of addressing it, have intended that the inference be that you didn’t take this to be anything proving there are enough neutrinos, hence we may be talking past one another.

    Ta.

  43. #43 Wow
    July 31, 2015

    Yes, PJ, precisely.

    A pristine example of wordsalad from someone who likely is trolling.

  44. #44 Wow
    July 31, 2015

    What’s that raggie? That’s utter nonsense.

    Teapots have to form in a specific shape.

    Planets and beings don’t.

    So 1 way to organise those 10^20 atoms (teapot)

    vs 10^100 ways to organise those 10^60 atoms (planet and life)

    Which is more likely?

  45. #45 Jim Salsman
    July 31, 2015

    “We know that dark matter can’t be … black holes. The main reason this doesn’t work is that we know the total mass dark matter brings into our galaxy, and it’s a lot, about 10 times as much as the visible matter. If that amount of mass was made up from black holes, we should constantly see gravitational lensing events — but we don’t.”

    On the contrary, if inflation resulted in sufficient intermediate mass black holes (around 100,000 solar masses each) to explain the formation of relatively recently discoved quasars at z>6, those would require that all dark matter be comprised of such black holes, and they would not be detectable through gravitational lensing. This is not some kind of a crackpot theory, it is the only viable explanation of early AGN:

    http://arxiv.org/abs/1503.02317

    http://arxiv.org/abs/1501.07565

    http://iopscience.iop.org/2041-8205/720/1/L67/pdf/2041-8205_720_1_L67.pdf

  46. #46 Wow
    July 31, 2015

    On the contrary, they would still happen far more often than they appear to.

  47. #47 Bob H.
    U.K.
    January 12, 2016

    As the search goes on for elementary particles (and energy) which may prove the existence of dark matter and energy, will the new model be named “The substandard model”?

    Perhaps the new discoveries will somehow go along the way to explain the long standing mysteries such as gravity, space, and time

  48. #48 Wow
    January 13, 2016

    No, it won’t Bob.

    Only people like yourselves, unversed but unable to let that hold them back, would be “substandard”.

    Maybe there needs to be a 11th fact: blowhards will abound with any discussion of dark matter, because they don’t know what the hell is going on.

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