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I Dark Matter Interactions

  1. Jun 26, 2017 #1
    As I have come to understand it - we have no current means of directly interacting with Dark Matter. We can only observe the gravitational effects that Dark Matter has on Baryonic Matter.

    My question is: What forms of detection have been attempted and determined to not directly interaction with Dark Matter - other than light, because that is pretty obvious?

    (I'm asking because I'm trying to put together a Sci-Fi novel that utilizes Dark Matter, and I don't want to get its interactions wrong)

    Also, although I'm sure this answer is "We don't know yet", are there any likely particles, fields, or energies that can/would directly interact with Dark Matter?
  2. jcsd
  3. Jun 27, 2017 #2
    All i know is that one their is that they are something sort of WIMP( weakly interacting massive Particle). So getting it to interacting is pretty difficult. I'd hazard a guess that it is unknown.
    I would say more but it is based on my understanding of thanks i have read/see and would rather give fact rather thanks misguided assumptions.

    But dark matter is still a theory,i believe.
  4. Jun 27, 2017 #3
    In science "theory" means something different than in ordinary language. Theory in science is the best thing we can have.
  5. Jun 27, 2017 #4
    It's true that we only directly observe it through gravity. However, most theories would mattamrically require that they also interact via the weak force. The problem is that would only be able to see that if it directly interacted with an atoms nucleus. Currently running experiments are watching for those (interaction with the nucleus creates a tiny flash of light.)
  6. Jun 27, 2017 #5


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    How do you quantify this? It is certainly not true for axions or sterile neutrinos.

    You also have indirect searches for decay/annihilation products and collider experiments looking for missing transverse momenta and/or monojets/monophotons.
  7. Jun 27, 2017 #6
    Until its proven
  8. Jun 27, 2017 #7


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    This is one the absolutely most common misconceptions about the empirical sciences. You can never "prove" a theory. You test it to check whether it continues being a goid description in regimes where it has not been tested yet or to accuracies at which it has not been tested before. If the prediction fails you need to revise the theory, which does not make it "false", it makes it a bad description in the new regime. It does not invalidate the use of the theory in regimes where it is known to be sufficiently accurate. If this was not the case we would not be using Newtonian gravity for anything today - but we do.
  9. Jun 27, 2017 #8


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    The Wikipedia article has a good summary of the attempts at detecting dark matter:

    There's some more detail at the linked article for WIMPs:

    The basic idea is that what they're looking for in these searches is an unexpected interaction, typically with an atomic nucleus. They're looking for energy coming out of the experiment that they didn't see go into it, and for that energy to correspond to a particle of a specific mass. So far there's been nothing definitive, but we've only barely started to probe the expected sensitivity required to detect dark matter.
  10. Jun 27, 2017 #9


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  11. Jun 27, 2017 #10
    Hi newjersey:

    I think that the technical word you use in the above quote is misspelled.
    Did you mean
    "metamerically": In a metameric manner
    "metameric": exhibiting structural isomerism​
    At this point I have to make a guess that you are using the term "metamerically" metaphorically because the only definitions for "structural isomerism" seem to be related to chemistry.
    "structural isomerism": a form of isomerism in which the same atoms are arranged in different orders; either having the same or different functional groups
    Would you please elaborate in non-technical language what you intended as the meaning of the quote?

    Also, when you said "theories", did you mean
    most theories of all types, or
    most scientific theories,
    or most physics theories,
    or most particle physics theories?​

  12. Jun 27, 2017 #11
    Hi kimbyd:

    I wonder if the usage of the technical word "theory" is properly applied to the concepts leading to the type of research you describe in the above quote. At the present time, there seem to be many still plausible competing ideas about what kinds of stuff dark matter will turn out to be made of. The usage of scientific "theory" that seems to me to be the most respected applies to a collection of related ideas that either
    (1) have already been verified by experimental observation as being useful in the context of a reasonably wide range of application, for example, (a) general relativity, and (b) evolution,
    or also perhaps
    (2) have a single concept of what is being searched for, for example, the Higgs boson.​
    With so many competing ideas about dark matter, I suggest a more accurate word for a concept leading to the kind of experiment you describe in the quote would be "speculation". Three examples of such ideas are: (a) WIMPs, (b) MACHOs, and (c) primordial black holes.

  13. Jun 27, 2017 #12


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    No, speculation is highly inaccurate. We have quite a lot of evidence that supports the existence of dark matter. That the evidence is not currently specific enough to single out a single, specific dark matter candidate does not justify the implications that come with the term.

    The way to understand it is that "WIMP" is not a single theory, but rather a class of related theories with common elements.

    And by the way, MACHOs are basically ruled out by CMB data, as no compact objects could have formed before the emission of the CMB, but the dark matter signal is very apparent. Primordial black holes within a narrow mass range aren't yet ruled out by the data, but are considered a very exotic proposal. The leading class of theories are contained within the WIMP class of theories.
  14. Jun 27, 2017 #13
    Hi kymbyd:

    Thank you for your reply. I think I must have not phrased my remarks clearly enough. I have no problem with the usage: "dark matter theory". However, the "WIMP theories" together with the now defunct "MACHO theory" and the "primordial black hole theory" all together seem to be too speculative to be "theories". Also, a "theory" that has had no positive experimental/observational support seems to me to be more accurately called a "speculation".

    Regarding WIMPs, I understand from other threads on these forums (can't locate them right now) that the upper energy limit for plausible WIMP dark matter is not very far above what is currently measurable, and all of the lower range of energies have failed to achieve experimental support.

    Is it still appropriate to use the term "MACHO theory" now that this "theory" is no longer in the running to be an explanation of what dark matter is?

    Now, let is suppose hypothetically the the future experiments that explore up to the maximum theoretical energy for WIMP dark matter also fail to achieve positive results. Would the term "WIMP theory" still be proper terminology? I suppose "defunct MACHO theory" and "defunct WIMP theory" would still be a useful usage.

  15. Jun 27, 2017 #14


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    I don't think you have the understanding of the subject matter to make that determination.
  16. Jun 27, 2017 #15
    OK, so WIMPS are still being investigated, other theories seeming to be less plausible.
    Maybe there is something we don't yet get what it is, like the famous singularities in relativity.
    Like trying to measure the wind direction at the North pole.
  17. Jun 28, 2017 #16


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    It's not possible to quantify the likelihood of things we haven't yet thought of. The best that can be done is to keep collecting new evidence, to push observations into new regimes, and hope that we'll find enough about the holes in current theories to guide the way to more accurate ones.
  18. Jun 28, 2017 #17
    Hi kimbyd:

    It is certainly quite possible that you know a great deal more than I do about dark matter research, and it also quite possible I have made a mistake. There are two points which I have been making regarding the use of the term "theory". Which one are you telling me is wrong.

    1. None of the three categories of "theories" about what dark matter is made of ((a) WIMPs, (b) MACHOs, and (c) primordial black holes) have up until now had any experimental/observational support.
    2. The proper use of the term "scientific theory" to describe scientific ideas requires that the ideas have at least some experimental/observational support.

    (1) might be a mistake since it is possible that some experimental/observational support exists about (a), (b), and/or (c) that I am not aware of.
    (2) might be a mistake if the scientific community generally considers it to be appropriate to use the word "theory" to describe some ideas in sense of "scientific theory" when there has been no experimental/observational support for these ideas.

    With a few minor format changes, definitions of "theory" from
    1. a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena - e.g.: the wave theory of light.

    2. (a) a belief, policy, or procedure proposed or followed as the basis of action her method is based on the theory that all children want to learn. (b) an ideal or hypothetical set of facts, principles, or circumstances —often used in the phrase in theory - e.g.: in theory, we have always advocated freedom for all.

    3. (a) a hypothesis assumed for the sake of argument or investigation. (b) an unproved assumption - syn.: conjecture. (c) a body of theorems presenting a concise systematic view of a subject theory of equations.

    4. the general or abstract principles of a body of fact, a science, or an art - e.g: music theory.

    5. abstract thought - syn.: speculation.

    6. the analysis of a set of facts in their relation to one another.
    The above are all definitions of "theory" as used in ordinary English. Which of the above do you believe are generally accepted by the physics community as a complete acceptable definition of "theory" when used in the phrase "scientific theory" as applied to ideas about physics?

    The following is from
    A scientific theory is an explanation of some aspect of the natural world that can, in accordance with the scientific method, be repeatedly tested, using a predefined protocol of observations and experiments.[1][2] Established scientific theories have withstood rigorous scrutiny and are a comprehensive form of scientific knowledge.[3]
    It is important to note that the definition of a "scientific theory" (often ambiguously contracted to "theory" for the sake of brevity, including in this page) as used in the disciplines of science is significantly different from the common vernacular usage of the word "theory".[4][Note 1] In everyday non-scientific speech, "theory" can imply that something is an unsubstantiated and speculative guess, conjecture, idea, or, hypothesis;[4] such a usage is the opposite of the word "theory" in science. These different usages are comparable to the differing, and often opposing, usages of the term "prediction" in science versus "prediction" in vernacular speech, denoting a mere hope.
    Note 1: Per NAS 2008: "The formal scientific definition of theory is quite different from the everyday meaning of the word. It refers to a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence."​

    BTW: another word that might be correctly used rather than "speculation" for theoretical based scientific ideas without experimental/observational support is "conjecture".

  19. Jun 28, 2017 #18


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    Attempts to exclude certain models as not being theories are ultimately worthless, as they argue that these models are of less value based upon arbitrary conditions that have nothing to do with the usefulness of such models to science.

    By large, actual scientists don't concern themselves very much with what a model is called, but on its contents. That's what's important.
  20. Jun 29, 2017 #19
    Hi Kimbyd:
    I think we will have to agree to disagree. I don't believe that a decision about the usage of the term "theory" changes in very many minds the usefulness of a conjecture based on sound theoretical ideas even without any observational support. The MACHO conjecture remains useful in that it led to observational data that proved it was wrong. The WIMPs conjectures remain useful without any (so far) observational support, because it leads to well planned experiments that should eventually lead to either support that calling it a theory is justified, or of a conclusion that, like the MACHO conjecture, it is also false.

    My concern with a scientist referring to a conjecture without observational support as a "theory" is that it creates confusion in the minds of non-expert but interested readers that the conjecture has actually been confirmed to be supported by observational evidence when it has not yet been.

  21. Jun 30, 2017 #20


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    Well, you're in luck, because scientists only very rarely refer to dark matter as a "theory".

    There are lots of things about the way science is explained to non-scientists that are misleading. This really isn't one of them. First, it's not done often. Second, it doesn't mislead people about the quality of evidence for dark matter.
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