Dark Matter : Is it science?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by The God, Mar 8, 2017.

  1. The God Valued Senior Member

    Note : Dark Energy can also be added to OP title.

    Is it good or acceptable science to define the DM as it is? Isn't it quite close to saying that God exists but it cannot interact in general, it somehow manifests itself in miracles.

    Science does not accept God, so how come it accepts DM, the way it is theorized in mainstream?

    Let me push it further, gravity and light speed are interlinked, we are attempting to unify EM with gravity. So conceptualizing DM as interacting gravitationally but not electromagnetically will contradict any success on unification. So DM definition appears to be ad hoc. Isn't it?
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  3. exchemist Valued Senior Member

    I can only comment on this insofar as the philosophy of science is concerned.

    God is generally considered a non-scientific hypothesis, because there is no objective (reproducible) evidence for his existence, and no predictions can be made from the concept.

    By contrast, there are objectively observed phenomena that can be accounted for by the dark matter hypothesis (as discussed in the galactic unit thread for example) and there are predictions that can be made from its existence, since it is predicted to exert a gravitational effect on matter than can be observed. It seems to me, therefore, that dark matter is a scientific hypothesis, unlike God.

    Evidently the existence of dark matter is not yet a settled question in science. But that does not make it an unscientific hypothesis.

    I'll leave the astronomical and cosmological arguments to others, as it is not my subject, as we know

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  5. The God Valued Senior Member

    One of the aspect open for discussion is philosophy of science. DM definition does not appear to fit here.

    Reference to God was to highlight the lack of scientific philosophy only.

    Coming to your observation...

    Do we have reproducible evidence for DM? My assertion is that DM is hypothesized to account for galaxy speed distribution anomaly, so the same cannot be taken as evidence for DM.

    Can we make any prediction based on dark matter concept? Not that I am aware of any. Take for example, couple of our solar system planets were predicted based on deviation in simple keplarian motion of known objects. But I dont think we have any meaningful prediction based on DM concept.
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  7. rpenner Fully Wired Staff Member

    Dark (unseen) matter exists, even if GR is wrong.
    These I knew without research:
    1) Galactic rotation curves are consistent with a roughly spherical halo of mass of much larger extent than stars and hydrogen clouds would suggest, so if GR is right there is DM. http://www.nature.com/nphys/journal/v11/n3/full/nphys3237.html
    2) Details of gravitational lensing about the bullet cluster indicates there is a substantial gravitating component of galaxies which is not stars or gas clouds. This is evidence for DM, independent of GR. https://en.wikipedia.org/wiki/Bullet_Cluster
    3) Details of how galaxies clump and other parts of cosmology are best explained by dark matter. This clumping is observed in the Cosmic Microwave Background Radiation as invisible mass clumps differently than matter that is pushed around by light in the early universe.
    4) MOND (a speculative modification of gravity to fit flat galaxy rotation curves) doesn't make cosmological or lensing evidence not require dark matter.
    Here are more:
    5) Clusters of galaxies require DM to be gravitationally bound.
    6) Big Bang Nucleosynthesis says there was never enough normal matter to explain the matter density of the universe.
    7) Observation of giant gas clouds allows us to localize clumps of dark matter.
    8) Multiple lines of independent evidence are consistent with the universe having a particular amount of dark matter. This is a bizzare, extraordinary coincidence if dark matter were fictional. https://arxiv.org/pdf/1004.1711.pdf (figure 11)

    For Technical people:

    Last edited: Mar 8, 2017
  8. exchemist Valued Senior Member

    Well there is this: https://www.nasa.gov/home/hqnews/2006/aug/HQ_06297_CHANDRA_Dark_Matter.html

    As I understand the hypothesis, dark matter is hypothesised to interact only via gravity and the weak force, not EM. So if it exists the prediction would be for DM to separate from ordinary matter in circumstances in which the EM forces between particles of ordinary matter act on an astronomical body in a different way from the gravitation: the DM would be predicted to respond only to the latter, not the former, while ordinary matter would respond to both. This is what they say they observed here. So there is a testable prediction from the hypothesis and NASA has attempted to test it. That seems to me to make it a scientific (predictive, testable) hypothesis, regardless of the results.
  9. Oystein Registered Senior Member

    Of course it is science. It is used to explain observations. Through further observations, will we find out what it really is? Maybe. Or will we find, through further observations, that there is a different reason for the observations? Maybe. Or will we find out that it doesn't exist at all? Maybe. This is how science progresses -- science is self-checking and self-correcting.
  10. Xelasnave.1947 Valued Senior Member

    Firstly DM would seem to be science perhaps what you seek to determine is it really there.
    I have never felt comfortable about DM simply because we can't see it, yet observations highly suggest its presence.
    If science is to prevail we need more than an uncomfortable feeling before we reject DM.
    We need a new model.
    I have always believed GR somehow described a flow of space such that gravity probably was a result of an external pressure upon an object rather than the attraction between bodies.
    So my feeling is one could expect the rotation of galaxies may be as observed to fit what I see asan external pressure as oppossed to a centralised attraction.
    Unfortunately I am unable to offer more than "my feeling" but I dont see my approach as inconsistence with GR and as such feel GR may well be applied in support of my approach.
    It is clear that many "objects" would "fly apart" if the attraction between the masses we observe was the only force. So it is entirely reasonable if things work via attractionto look for more mass.
    I know GR does not need a force but GR is a scientific model and as such may not describe reality but given its sucess I think maybe it could be applied differently to reflect the external pressure I believe opperates.
    I know I am not scientific here but I am not a scientist.
    I view space and the objects in it as somewhat like objects suspended in water in so far as it is the pressure of the surrounding water that hold stuff in place rather than any interaction between the object via attraction.
    Now please dont be hard on me those of you who are better educated I offer my idea somewhat like someone leaning over a mechanic and saying did you check the spark plugs.. But so much of what we believe is based upon theconcept of attraction and frankly I do not believe there is such a force and I dont know that it has ever been provided a mechanism.
  11. The God Valued Senior Member

    Observations and need are not disputed. What is questioned is scientific sufficiency of a concept.

    Is it not like this that based on observations something must exist which interacts only gravitationally but not through EM, and we know nothing about this something.

    Is it sufficient to be called as scientific concept? Isn't it incomplete? Isn't it too vague?

    How different it is from saying that there are hundreds of unexplained miracles, so there must be something like all powerful God but it does not interact otherwise.
  12. The God Valued Senior Member


    This is what I am attempting to say....if science is to prevail we need a comprehensive conceptualization before we accept a concept.
  13. Xelasnave.1947 Valued Senior Member

    Well my approach is not comprehensive thats for sure and all I can do is suggest "if we look at it this way then maybe".
    However if we view the universe similar to objects suspended in water do you think that could explain our observations.
    I havent tried to fit the bullet cluster into my approach but I think an external force could still give us the impression there is matter where there appears to be none.
    You always say there is little discussion is my approach even worth considering oreven discussing.
    How you could reduce it to an equation is well beyond me.
  14. spidergoat Valued Senior Member

    You need to read up on the difference between science and pseudoscience, and the difference between an hypothesis and a theory.
  15. The God Valued Senior Member


    I am not commenting on your thoughts about pressure aspect.

    I am saying if the concept of DM comprehensive or self sufficient. IMO it is not.
  16. The God Valued Senior Member

    May be you can post here any relevant extract.
  17. Xelasnave.1947 Valued Senior Member

    I can understand your reluctance to comment given I have left myself open to being called a crackpot and you donot want to be labled similar via association however I see no point in simply questioning the current model if you have nothing to replace it with.
    And for others who will jump to point out what "theory" means let me assure you I know the implications of theory and see my thoughts as mere ideas.
    In my defence I at least offer something more than I do t like DM.
    I see no point in saying DM is not to my liking therefore get rid off it, which TG seems to be your approach.
    If you cant offer a new direction what is the point in simply saying you dont like the prevailing model.
    DM is not well understood but if attraction is required what alternative is there.
    Do you have an alternative or some other way to deal with dark matter if not I believe you must accept the current model.
  18. Xelasnave.1947 Valued Senior Member

    DM may be seen by you as not being comprehensive can you outline what you mean?
    I dont understand how you critisize without a specific complaint.
    Do you have one?

    I was just thinking about my pressure idea and would think the observations we attribute to dark energy could be explained via a universal pressure, what do you think?

  19. spidergoat Valued Senior Member

    Not really the criteria for an hypothesis.
  20. Xelasnave.1947 Valued Senior Member

    I dont know that you are correct here.
    We make observations and then fit them to our best models. I do not think scientists have the same luxury as me to sit back and come up with a generalisation then see if it fits.
    Upon my understanding its one step at a time a slow build up of theories that finally may produce an overall concept.
    However perhaps I could ask if you have an overall concept?
    And further how could you arrive at an overall concept unless you indulge in speculation, as I have and clearly not science.
  21. The God Valued Senior Member

    Speculation and ideas are fine, these could be a part of process of developing a consistent model.

    Take Dark Matter...

    1. It interacts with baryonic matter gravitationally, it does not interact with baryonic matter EM way.

    2. It does not interact with itself gravitationally in the same way.

    3. Nothing more is known about DM.

    Are these two points sufficient to include this hypothesis as a part of scientific discourse? Are they not just some fantastic ideas, falling short of being labelled as scientific concept?
  22. The God Valued Senior Member

    Self sufficiency is surely a criterion for an hypothesis.

    To me the present conceptualization of DM is just few statements. It has not come to a level wherein it can be accepted as science.
  23. rpenner Fully Wired Staff Member

    I don't think you have that right. Try saying it again without unclear antecedents.
    ajanta likes this.

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