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I think you misunderstand the threads. Dark Matter isn’t a thing it’s a place holder it has many candidates some more probable than others it might be that the

I think you misunderstand the threads. Dark Matter isn’t a thing it’s a place holder it has many candidates some more probable than others it might be that there is only one class of dark matter it might be that there are multiple classes of dark matter. It might be that all the dark matter will be new forms of matter it might be that some or all of it will end up being baryonic matter. It also might be that we won’t find it at all in which case we might need to say that our understanding of gravity and the geometry of space time isn’t nearly as representative of reality as we thought maybe dark matter is gravity leaking in from other universes maybe it’s the affect of additional dimensions of space time maybe quantum gravity causes some wired emerging phenomenon that affects the geometry of space time that we attribute to missing mass. There isn’t a consensus amongst scientists on anything related to dark matter other than based on observations we are missing a truckload of mass in the universe. And currently people are trying to explain it by looking for new forms of matter, normal matter that is very cold and so we can’t see it, and even attempting at modifying the theories of gravity to account for the observations we see with new relativistic and classical modified gravity models.

acqq 8y ago
> it might be that some or all of it will end up being baryonic matter It can’t be. It’s already known that 5/6 ths of all the matter in the observable Universe can’t be baryonic. > There isn’t a consensus amongst scientists Only for completely useless definitions of the “concensus.”
- dogma1138 8y ago
  >It can’t be. It’s already known that 5/6 ths of all the matter in the observable Universe can’t be baryonic. No it's not known, it's highly unlikely that the "final" dark matter candidate will be completely made up of baryonic matter but it's not been exclusively proven. Only Siths deal in absolutes. >Only for completely useless definitions of the “concensus.” Do you have a more useful definition of consensus for this matter? if so please share it.
  - gmjoe 8y ago
    By definition it's not baryonic, because we aren't detecting it and we would be detecting it if it were. "Dark" in this context means, in and of itself, non-baryonic. And please don't bring silly Star Wars references here, they don't help and this particular one is basically offensive. HN isn't reddit.
    - dogma1138 8y ago
      No Dark didn’t mean non baryonic at first when DM was conceived and still does not mean that today dark was just that dark as it wasn’t emitting any light we could detect which is why CBM, rogue brown dwarfs and primordial black holes were all a candidate for dark matter at some point. And thanks for the advice I’ll keep using my SW references when they are fitting and this one is fitting indeed. Here is another one just for you began the dark matter war has.
  - acqq 8y ago
    > it's highly unlikely that the "final" dark matter candidate will be completely made up of baryonic matter but it's not been exclusively proven. That "highly" in "highly unlikely" is the key here, that highly is "immensely huge" e.g.: http://iopscience.iop.org/article/10.3847/2041-8205/824/2/L31/meta http://iopscience.iop.org/article/10.3847/2041-8205/824/2/L3... "While future observations will determine the strength of the constraints from Eri II, existing data from Eri II and from the sample of compact ultra-faint dwarfs appear sufficient to rule out dark matter composed exclusively of MACHOs for all masses above ~10e−7 mass of the Sun." And if your definition of the "consensus" is 100.0000% then I do consider it useless. https://www.merriam-webster.com/dictionary/consensus https://www.merriam-webster.com/dictionary/consensus If you use Merriam-Webster's: "the judgment arrived at by most of those concerned" then yes, there is a consensus because "most" begins for me at "more than 60%." And I accept only those that are actually "in the field" and not those that studied something completely different but "have a strong opinion." Sorry, that's automatically useless. I know personally the Ph.Ds who believe nonsense as soon as they are out of the area they have researched personally. It's simply a https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect as in "I was successful while studying X my whole life and therefore I believe I can 'understand' Y better than those who studied Y their whole life." And I'm talking here only about the natural sciences.
gpderetta 8y ago
Isn't some weakly interactive massive subatomic particle pretty much the consensus?
- dogma1138 8y ago
  WIMPs are just a whole class of placeholder particles, there is no consensus on anything currently everyone has their own pet theory or theories depending on their field.
  - walrus1066 8y ago
    Ultimately this is because we can't yet prove by experiment, which theory is the correct one. We need to observe these guys being produced in a particle collider to definitively know what dark matter is made of.
    - dogma1138 8y ago
      It’s not just that say we find wimps in the lab we need to have some sort of a model that would explain how they are or were produced in the universe and more importantly that they were produced in the correct ratio to be the single explanation for dark matter. It’s quite possible that we will find WIMPs in a particle accelerator but then be stuck with the fact that at best they’ll only account for 3% of the dark matter we observe and then it’s again back to the drawing board.
walrus1066 8y ago
It can't be baryonic matter, because baryons are made of quarks, which carry electric charge, and therefore interact with light, xrays etc. But we don't see dark matter scattering or absorbing the x-rays & whatnot emitted by stars, nebulae etc. Hence the 'dark' in dark matter. So it has to be made of particles which have no electric charge. The only such longlived particle we know of is the neutrino, but these guys travel at nearly the speed of light, so can't clump together to form the concentrated blobs of dark matter we observe from gravitational effects. So dark matter cannot be explained by the particle we know about.
- amluto 8y ago
  Neutrons are uncharged baryons. The problems with baryonic dark matter have little to do with the charge of quarks.
  - walrus1066 8y ago
    That quarks have charge, means they participate in electromagnetic interactions. So they can absorb, emit, & scatter photons. It doesn't matter that a neutron is overall charge neutral, because it's the elementary particles that make up the neutron, that participate in interactions. This is why, you don't fall through the earth, despite being made of charge natural atoms, because the surrounding electrons of our atoms repel those of the atoms making up the ground, counterbalancing the gravity pulling us down.
    - dogma1138 8y ago
      I think you are mistaken here. Photons couple with charged particles due to their spin, this interaction can be seen through Compton scattering. https://en.m.wikipedia.org/wiki/Compton_scattering https://en.m.wikipedia.org/wiki/Compton_scattering However we have for example Neutrinos which are weakly interactive even more so than the photon and are not baryons (the real reason why neutrinos are not a baryonic DM candidate ;)). A neutrino will not interact with a photon at all since photons do not have an interaction through W and Z bosons (both W, Z and Photons are electroweeak gauge bosons) and neutrinos are not charged. There are a lot of reasons why you wouldn’t fall through the earth electromagnetism is just one of them, however even non charged baryonic matter can be “solid” and resist gravity for example neutrons will resist gravity through degeneracy it’s all a question of which type of interactions are possible. There is much more to particle interactions than charge. As far as photons interacting with neutrons, neutrons while being neutral in charge have a magnetic diepole which is why the photon can couple with them. You can make baryonic matter that is massive and does not interact well with photons, the LHC has been making some new baryonic matter but none of it is a good candidate for dark matter so far. But overall yes currently it looks like baryonic matter at least the one of the standard model without any extensions produces isn’t a good candidate for DM. :)

acqq 8y ago

> it might be that some or all of it will end up being baryonic matter It can’t be. It’s already known that 5/6 ths of all the matter in the observable Universe can’t be baryonic. > There isn’t a consensus amongst scientists Only for completely useless definitions of the “concensus.”

dogma1138 8y ago
>It can’t be. It’s already known that 5/6 ths of all the matter in the observable Universe can’t be baryonic. No it's not known, it's highly unlikely that the "final" dark matter candidate will be completely made up of baryonic matter but it's not been exclusively proven. Only Siths deal in absolutes. >Only for completely useless definitions of the “concensus.” Do you have a more useful definition of consensus for this matter? if so please share it.
- gmjoe 8y ago
  By definition it's not baryonic, because we aren't detecting it and we would be detecting it if it were. "Dark" in this context means, in and of itself, non-baryonic. And please don't bring silly Star Wars references here, they don't help and this particular one is basically offensive. HN isn't reddit.
  - dogma1138 8y ago
    No Dark didn’t mean non baryonic at first when DM was conceived and still does not mean that today dark was just that dark as it wasn’t emitting any light we could detect which is why CBM, rogue brown dwarfs and primordial black holes were all a candidate for dark matter at some point. And thanks for the advice I’ll keep using my SW references when they are fitting and this one is fitting indeed. Here is another one just for you began the dark matter war has.
- acqq 8y ago
  > it's highly unlikely that the "final" dark matter candidate will be completely made up of baryonic matter but it's not been exclusively proven. That "highly" in "highly unlikely" is the key here, that highly is "immensely huge" e.g.: http://iopscience.iop.org/article/10.3847/2041-8205/824/2/L31/meta http://iopscience.iop.org/article/10.3847/2041-8205/824/2/L3... "While future observations will determine the strength of the constraints from Eri II, existing data from Eri II and from the sample of compact ultra-faint dwarfs appear sufficient to rule out dark matter composed exclusively of MACHOs for all masses above ~10e−7 mass of the Sun." And if your definition of the "consensus" is 100.0000% then I do consider it useless. https://www.merriam-webster.com/dictionary/consensus https://www.merriam-webster.com/dictionary/consensus If you use Merriam-Webster's: "the judgment arrived at by most of those concerned" then yes, there is a consensus because "most" begins for me at "more than 60%." And I accept only those that are actually "in the field" and not those that studied something completely different but "have a strong opinion." Sorry, that's automatically useless. I know personally the Ph.Ds who believe nonsense as soon as they are out of the area they have researched personally. It's simply a https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect as in "I was successful while studying X my whole life and therefore I believe I can 'understand' Y better than those who studied Y their whole life." And I'm talking here only about the natural sciences.

gpderetta 8y ago

Isn't some weakly interactive massive subatomic particle pretty much the consensus?

dogma1138 8y ago
WIMPs are just a whole class of placeholder particles, there is no consensus on anything currently everyone has their own pet theory or theories depending on their field.
- walrus1066 8y ago
  Ultimately this is because we can't yet prove by experiment, which theory is the correct one. We need to observe these guys being produced in a particle collider to definitively know what dark matter is made of.
  - dogma1138 8y ago
    It’s not just that say we find wimps in the lab we need to have some sort of a model that would explain how they are or were produced in the universe and more importantly that they were produced in the correct ratio to be the single explanation for dark matter. It’s quite possible that we will find WIMPs in a particle accelerator but then be stuck with the fact that at best they’ll only account for 3% of the dark matter we observe and then it’s again back to the drawing board.

walrus1066 8y ago

It can't be baryonic matter, because baryons are made of quarks, which carry electric charge, and therefore interact with light, xrays etc. But we don't see dark matter scattering or absorbing the x-rays & whatnot emitted by stars, nebulae etc. Hence the 'dark' in dark matter. So it has to be made of particles which have no electric charge. The only such longlived particle we know of is the neutrino, but these guys travel at nearly the speed of light, so can't clump together to form the concentrated blobs of dark matter we observe from gravitational effects. So dark matter cannot be explained by the particle we know about.

amluto 8y ago
Neutrons are uncharged baryons. The problems with baryonic dark matter have little to do with the charge of quarks.
- walrus1066 8y ago
  That quarks have charge, means they participate in electromagnetic interactions. So they can absorb, emit, & scatter photons. It doesn't matter that a neutron is overall charge neutral, because it's the elementary particles that make up the neutron, that participate in interactions. This is why, you don't fall through the earth, despite being made of charge natural atoms, because the surrounding electrons of our atoms repel those of the atoms making up the ground, counterbalancing the gravity pulling us down.
  - dogma1138 8y ago
    I think you are mistaken here. Photons couple with charged particles due to their spin, this interaction can be seen through Compton scattering. https://en.m.wikipedia.org/wiki/Compton_scattering https://en.m.wikipedia.org/wiki/Compton_scattering However we have for example Neutrinos which are weakly interactive even more so than the photon and are not baryons (the real reason why neutrinos are not a baryonic DM candidate ;)). A neutrino will not interact with a photon at all since photons do not have an interaction through W and Z bosons (both W, Z and Photons are electroweeak gauge bosons) and neutrinos are not charged. There are a lot of reasons why you wouldn’t fall through the earth electromagnetism is just one of them, however even non charged baryonic matter can be “solid” and resist gravity for example neutrons will resist gravity through degeneracy it’s all a question of which type of interactions are possible. There is much more to particle interactions than charge. As far as photons interacting with neutrons, neutrons while being neutral in charge have a magnetic diepole which is why the photon can couple with them. You can make baryonic matter that is massive and does not interact well with photons, the LHC has been making some new baryonic matter but none of it is a good candidate for dark matter so far. But overall yes currently it looks like baryonic matter at least the one of the standard model without any extensions produces isn’t a good candidate for DM. :)