Dark Matter vs. Dark Energy

  1. If Dark Matter was the mirror twin to Dark Energy, then normal matter would be siamese twins?
     
  2. jcsd
  3. Currently we don't know what dark matter is or if it even exists, same goes for dark energy. I personally don't believe in dark matter, atleasts the dark matter that is suppost to supply the extra gravity to explain why some star orbit so quickly even though they are at the edges of galaxies.
     
  4. mathman

    mathman 6,661
    Science Advisor
    Gold Member

    Different stuff

    According to current theory, dark matter (more precisely non-baryonic matter) and dark energy are completely different (although I have seen some speculation that there is some connection).
    In any case, dark matter is supposed to consist of stuff that doesn't interact with ordinary matter or emit any electromagnetic energy.
    Dark energy is based on a construct of general relativity. It may be related to the energy of the vacuum, although qualitatively, there is a vast discrepancy.
    In both cases, there is observational evidence for something, but these explanations are still quite tentative.
     
  5. Dark matter may just be a flow of negative and positive charges (which come from intergalactic space) across our galaxy.
    The magnetic field of the galaxy would concentrate the charges as they move inwards and so they would keep high velocity stars in orbit by pushing the stars towards
    the centre of the galaxy.The stars should be a little flatter on one side than on the other to reflect the pressure that the flowing charges create on their surfaces.It's possible that the flowing charges could be the gravitational force carriers themselves - the ones in Le Sage's theory of pushing gravity.
    I think dark energy is two new kinds of stable quarks which have a mass similar to the mass of the strange quark, and this explains why the strange quark has a 50 % uncertainty in its mass - its being mistaken for the new quarks in accelerator experiments from time to time.A new family of stable quarks would mean that there are two stable families (the up and down is the other one) and two unstable families ( the strange,charm and top and bottom).
     
    Last edited: Jul 15, 2004
  6. mathman

    mathman 6,661
    Science Advisor
    Gold Member

    I have never seen any description of such things. They should be evidenced by a lot of electromagnetic radiation.
    I am guessing you made this up. There is no evidence for such particles.
     
  7. Chronos

    Chronos 10,225
    Science Advisor
    Gold Member

    Excellent point. WMAP supports the premise that EM processes cannot explain the CMBR. By process of elimination, WIMP is the best guess at explaining 'dark matter'.
     
  8. Garth

    Garth 3,535
    Science Advisor
    Gold Member

    Have you tried Self Creation Cosmology? (see thread on this forum). SCC predicts a matter density parameter Omega of 0.22. Because it is a linearly expanding, 'freely coasting' universe this is all baryonic. The matter is dark in the sense that is is non luminous, just cold primordial hydrogen and helium with a high primodial metallicity (as observed in the IGM). It does not require dark energy at all, only a moderate amount of false vacuum energy density. (Omega = 0.11) This can be observed and tested in the vicintiy of the solar system as the Casimir force.
     
  9. Mathman:
    I have never seen any description of such things. They should be evidenced by a lot of electromagnetic radiation.

    Kurious:

    Not if the charge is very small - smaller than the charge of a quark for example.Then the EM wavelength could be very long and out of the range of measurement.

    There could be a new family of quarks with masses close to the mass of the strange quark - there is a 50% uncertainty in the mass of the strange quark
    -perhaps it is sometimes being mistaken for new quarks.These quarks could be dark energy.
     
    Last edited: Jul 17, 2004
  10. Heading Towards Omega


    Are you using critical density in order to understand the dynamics? Friedmann's curvature parameters are leading in this respect and extends too.......?

    Heading towards Omega takes on a whole new definition? :smile:


    http://physicsweb.org/objects/world/thumb/13/11/8/pw1311081.gif

     
    Last edited: Jul 17, 2004
  11. Garth

    Garth 3,535
    Science Advisor
    Gold Member

    sol2 - "Are you using critical density in order to understand the dynamics? Friedmann's curvature parameters are leading in this respect and extends too.......?"
    The inclusion of a scalar field and the redefinition of the equivalence principle in the theory produce a modified set of field equations. the Friedmann model universes are solutions of the GR field equations are they therefore also have to be modified. The theory is highly determined and has only one unconstrained cosmological parameter, H, which is to be determined by observation. The density of baryonic matter and false vacuum energy are fully determined by the field equations. The solution is a conformally flat space-time (either a cylinder - in the Jordan frame, or cone - in the Einstein frame of the theory) with a baryonic density of 0.22 and a false vacuum energy of 0.11 (observed in the laboratory as the Casimir force) leading to a total density of 0.33. There is no further unknown dark matter or energy.
     
  12. From one perspective I see geometrical consistancy being revisied here.

    I also see tipping light cones as a way of describing these curvature parameters. Gravity probe B seems very helpful in this regard, but if we remove the intent of the dynamics revealled in casimere, why would you say there is no dark energy?


    You have to define this movement some how, so you are speaking to reconstructing preconcieve values of Einsteins that are geometrically consistent? Looking at statement again here quoted, that you are satisfied?

    I am thinking of Reinmann here.
     
    Last edited: Jul 22, 2004
  13. Garth

    Garth 3,535
    Science Advisor
    Gold Member

    All cosmological observations, even those as simple as red shift, are theory dependent that theory being GR refined by Inflation. The only evidence for the existence of dark energy is the fact that WMAP indicates that the universe is flat which according to GR requires Omega = 1, yet measurements of density: including luminous matter, non-luminous mass required to close galactic clusters, and that required for galaxy formation models, total to around Omega = 1/3, hence the remaining 2/3 is dubbed dark energy. It also proves useful to explain the apparent (theory-dependent) observation from distant S/N that the universe is accelerating in its expansion. Change the theory, replace GR with SCC, and the predicted total density is only Omega = 1/3, while also yielding a conformally flat universe. Hence no dark energy is required. However it does predict and require a false vaccum energy (observed by experiments on the Casimir force) of average Omega = 0.11. Furthermore it does yield a 'freely coasting' universe that expands strictly linearly as investigated by Gehaut, Lohiya et al. referenced in my paper "Self Creation Cosmology - An Alternative Gravitational Theory" http://arxiv.org/abs/gr-qc/0405094. Such a universe does not require Inflation (which is why Gehaut, Lohiya investigated that model in the first place), they found it matched the distant S/N data and predicted a baryonic density of about Omega = 0.2. As SCC requires and predicts a matter density of Omega =0.22 the problem is solved, dark matter is ordinary baryonic hydrogen and helium with high primordial metallicity. It is dark in the sense of being non-luminous but not in the sense of being unknown.
     
  14. Nereid

    Nereid 4,014
    Staff Emeritus
    Science Advisor
    Gold Member

    Er no. That may 'solve' the cosmological DM 'problems', but it doesn't touch all the observations which point to the existance of non-baryonic DM, e.g. gravitational lensing (numerous examples, near and far), X-ray emission from cluster IGM (some model assumptions required, but those are quite independent from any cosmological models), galaxy rotation curves, (local) GC motion, and much more ...

    I suspect that the latest results from SDSS would be hard to square with SCC too.
     
  15. Garth

    Garth 3,535
    Science Advisor
    Gold Member

    Er yes actually! I do not dispute that DM is there, the question is, "What is it?" The averaged DM density from all the various observations you mention centre around 23% of critical density, SCC predicts 22% which is near enough do you not think? The reason why most of this is called non-baryonic is because the standard nucleo-synthesis model only allows a maximum of 4% density as baryons. As I mentioned in my post above the Indian team have shown that in the freely coasting universe, as the SCC solution, nucleosynthesis produces about 20% baryons + high priordial metallicity, this metallicity is indeed observed amongst the Lyman Alpha forest coming from the IGM, and normally attributed to (again un-observed) Population III stars. The IGM is also hot which is interesting and may be due to such first stars, but also the earliest galaxies appear mature which is perplexing, perhaps the universe is older than the standard theory thinks?

    There could also be the odd 1% or so of neutrino density not accounted for

    The SDSS results are heavily theory dependent and are degenerate in that they verify a family of different theories. It is only as you restrict the theory used to interpret and process the data to the standard GR + Inflation model that you get the so-called "precision cosmology".
     
    Last edited: Jul 23, 2004
  16. Nereid

    Nereid 4,014
    Staff Emeritus
    Science Advisor
    Gold Member

    Yep, that's a key question!
    This is what I meant when I said that SCC "may 'solve' the cosmological DM 'problems'"
    That is *one* reason why it's called 'non-baryonic', but certainly not the *only* reason.

    In brief, some classes of observations show DM as large mass/luminosity ratios. One by one the various potential baryonic repositories of the excess mass have been shown to be far from adequate. One of my favourites is Bahcall's HST observations - too few red dwarfs in the Milky Way halo.
    I have been meaning to check up on this; thanks for the reminder! My initial reaction is 'this can't be right - the oldest stars show very low (but non-zero) metalicity, and if DM were H+He+high metalicity, it would have to manifest itself in galaxy halos (for example) in some relatively easily observable fashion'.
     
  17. Garth

    Garth 3,535
    Science Advisor
    Gold Member

    There are obviously a lot of areas to be checked out in freely coasting cosmology, and a lot is still speculative. However the inference is that a lot of the non-luminous dark matter is in the IGM and not in galactic halos at all. There must of course be also a substantial amount in the halos to give the correct galactic rotation curves, however it may be cold matter, Jupiters, non-emitting Black holes or just plain bricks! It is very difficult to eliminate each of these candidates, the point is that the mass does not have to consist of some exotic non-baryonic species, just ordinary hydrogen and helium.

    The papers can be found at:
    A Concordant "Freely Coasting Cosmology"
    http://arxiv.org/abs/astro-ph/0306448

    A "Freely Coasting" Universe
    http://arxiv.org/abs/astro-ph/0209209
     
Know someone interested in this topic? Share this thead via email, Google+, Twitter, or Facebook

Have something to add?