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    #16
    Mass tells space-time how to bend and space-time tells mass how to move. Masses produce space-time wells into which other masses are drawn because of the bending of space-time. Masses have not been observed to produce space-time peaks (I.e. a repulsive force).

    Dark matter was postulated as a “patch” to the standard model in order to preserve it while explaining the observation that stars on the edges of rotating galaxies are moving faster than the Newtonian Physics predicts. Since the stars on the galaxy rim are moving faster something which exhibits the ability to tell space-time how to bend must be outside the orbit of those rim stars, attracting them. However, such objects are not seen in optical & radio telescopes, so they are not absorbing or emitting photons or electrons. And, no objects have been observed undergoing sudden changes in momentum due to a collision with an invisible object, aside from stars rimming a black hole.

    Dark matter has been vested with the property that the farther away it is from us the greater its ability to bend space-time. Ergo, the observation that galaxies at the edge of the observable universe are moving much faster (even to the speed of light) then galaxies much closer to our own. Paradoxically, because of the properties of homogeneity and isotropism, observers in those distant galaxies would conclude that Dark Matter’s space-time bending ability is much greater here than there.

    So, DM (and Dark Energy) cannot be observed, does not exchange energy or particles with normal matter, no sample of it has been collected so its physical and chemical properties cannot be measured, its gravitational power increases with distance (hence does not follow the inverse square law) and to explain all the observations that the standard model does not explain theorists compute that DM accounts for between 75 and 95% of the mass of the universe.

    Is it either DM or M-Theory? Both theories have painted Physics into a corner.

    It’s actually a great time for theoretical physics, and in many regards similar to the situation that led to the development of quantum physics. I believe that like the Ether concept at the turn of the 20th century, both DM and M-Theory will be abandon in favor of a more satisfactory modification of the standard model which has not yet been proposed. However, as long as Federal research grants control the direction of research we will have to suffer through periods of Lysenkoism.
    "A nation that is afraid to let its people judge the truth and falsehood in an open market is a nation that is afraid of its people.”
    – John F. Kennedy, February 26, 1962.

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      #17
      Fairly recently there's been papers reviving massive compact halo objects, in the form of lots of stellar mass black holes, as an explanation for dark matter, after being out of favour for the reasons you refer to. Many "small" black holes would not throw stars around so much. A problem with this idea is the origin of so many black holes, so primordial black holes are postulated.

      Also, the anomalous rotation speed of the outer regions of galaxies is not the only evidence of DM. In galactic collisions the stars, the clouds, and the DM are affected differently, at least in our models, and some gravitational lensing observations of colliding galaxies show matter in places consistent with those models.

      More broadly, we see galaxies forming a bit too soon in the life of the universe in the standard cosmology without DM; more gravity is needed.

      Regards, John Little
      Regards, John Little

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        #18
        MACHO's were a pretty hot topic several years ago. They are among several other candidates being proposed to solve the problem presented in the following graphic, to say nothing about the speed of expansion of the visible edge of the Universe:


        Others include WIMPS, Gravitinos, Axions and the precursor to String theory, the Kaluza-Klein particle, which involves a 5th dimension in a particle that weights about 600X the mass of a Proton. MOND is interesting too, and hasn't been ruled completely out. It appears that physicists are working more on attempting to modify the standard model to make it fit new observations, and if Dark Matter or Energy are ever actually discovered they modify the model for them as well.

        Interestingly, the number of small satellite galaxies surrounding our Milky Way have jumped from 4, to 11, to 50 and now more than a thousand, as a result of the Gaia spacecraft data. How many more exist that are too small or emit too little energy for Gaia to see? From the report on the computer modeling of small galaxies surrounding our Milky Way:

        "We have now simulated, for the first time, the RAR of dwarf galaxies on the assumption that dark matter exists," explains Prof. Dr. Cristiano Porciani of the Argelander Institute for Astronomy at the University of Bonn. "It turned out that they behave as scaled-down versions of larger galaxies." But what if there is no dark matter and instead gravity works differently than Newton thought? "In this case, the RAR of dwarf galaxies depends strongly on the distance to their parent galaxy, while this does not happen if dark matter exists," explains researcher Emilio Romano-Díaz.

        This difference makes the satellites a powerful probe for testing whether dark matter really exists. The Gaia spacecraft, which was launched by the European Space Agency (ESA) in 2013, could provide an answer. It was designed to study the stars in the Milky Way and its satellite galaxies in unprecedented detail and has collected a large amount of data.

        However, it will probably take years to analyze the data. "Individual measurements are not enough to test the small differences we have found in our simulations," explains doctoral student Enrico Garaldi. "But repeatedly examining the same stars improves the measurements every time. Sooner or later, it should be possible to determine whether the dwarf galaxies behave as in a universe with dark matter—or not."
        What can be stated for sure is that even though DM was first postulated in the 1930s, as of today there is no proof that it even exists. Lots of conjunctures based on "tantalizing hints", but no solid facts. Given the state of modern science and the sophistication of detection equipment and methods, this is surprising, considering DM is supposed to make up 75-95% of all matter in the Universe.
        Last edited by GreyGeek; Jul 04, 2018, 04:37 PM.
        "A nation that is afraid to let its people judge the truth and falsehood in an open market is a nation that is afraid of its people.”
        – John F. Kennedy, February 26, 1962.

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          #19
          Sterile Neutrinos equals DM?

          Timely episode. Matt's remarks at the end are hilarious!
          "A nation that is afraid to let its people judge the truth and falsehood in an open market is a nation that is afraid of its people.”
          – John F. Kennedy, February 26, 1962.

          Comment


            #20
            Thanks GG, as a nerd, who also taught college physics, I can relate to Matt's comment at the end...
            Kubuntu 24.11 64bit under Kernel 6.12.3, Hp Pavilion, 6MB ram. Stay away from all things Google...

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              #21
              Nerds...pfffttt.

              I only had 6 extra credits in math when I graduated high school so you guys are really weird...


              ...

              Please Read Me

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