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Dark Matter Missing Mass Really too Much Gravity

  1. Aug 8, 2010 #1
    Photons must have a certain amount of energy to be absorbed by an electron. A photon with a little too much energy to be absorbed by one electron and not enough to be absorbed by another would be invisible to all electrons and everything else. However such photons still have energy so they would interact with matter and each other through gravity.
     
  2. jcsd
  3. Aug 8, 2010 #2
    Its nice that your title is completely unrelated to your post.
    For any photon energy, there exists something that will absorb/interact with it, electron or otherwise.
    Because we have no quantum theory of gravity, it is unclear if photons influence other bodies through gravity.
     
  4. Aug 8, 2010 #3
    Its nice that your title is completely unrelated to your post.

    Then why do you address my point that photons could be dark matter.


    1. You say there is no connection between missing mass and dark matter.

    http://www.datasync.com/~rsf1/missmass.htm

    In 1933 Fritz Zwicky was the first to find a need to invoke the idea of missing mass or dark matter. He looked at eight Coma galaxies. By assuming visual equilibrium,* he calculated the mass-to-light ratio and determined that about 90% of the mass necessary to account for the observed ratio was missing and therefore invisible. or "dark." Here, the apparent rapid velocities of the galaxies, with respect to their common center of mass, suggested that much more mass (than could be seen) was required to keep the galaxies from flying out of the cluster. (BSVD)


    2. You said that missing mass has nothing to do with gravity.

    http://plus.maths.org/content/what-dark-matter
    We put it to Martin Rees, Astronomer Royal and Professor of Cosmology and Astrophysics at the University of Cambridge. Here is his answer. The second part of the question has been answered in Plus by John D. Barrow.
    What is dark matter?
    The galaxies in our Universe are not exclusively made up of the stuff we can see, but are held together by the gravitational pull of so-called dark matter. We shouldn't assume that everything is equally conspicuous and shouldn't therefore be surprised by this discovery.

    3. For any photon energy, there exists something that will absorb/interact with it, electron or otherwise.

    Prove it.

    4. Because we have no quantum theory of gravity, it is unclear if photons influence other bodies through gravity.

    Unclear to you perhaps. You make my point by saying that it unclear. The question is could photons be dark matter and if it is unclear then it is possible.

    --------------------------------------------------

    Produce a creditable source that will deny in public that photons influence other bodies through gravity.

    Prove that for any photon energy, there exists something that will absorb/interact with it, electron or otherwise.

    I am interested in the truth so I await your answer.
     
    Last edited: Aug 8, 2010
  5. Aug 8, 2010 #4
    Wow, someone is feisty.
    Your post title is "Dark Matter Missing Mass Really too Much Gravity," suggesting that the problem isn't that there is missing mass ("dark matter"), but instead there is too much gravity (i.e. gravity should be weaker, or less coupled, etc). But apparently you're trying to argue that dark matter is just photons, which also wasn't clear from your first post.



    Nope, didn't say that. Dark matter is DEFINED as 'missing' mass.

    Again, didn't say that. The reason why mass is missing, is due to the observed effects of gravity.

    Electrons, protons, muons, etc will absorb any energy of photon with which is can be excited. Line absorption occurs when the energy matches the separation between orbitals in an atom, or vibrations in a molecule, etc etc. But charged particles can also be excited thermally/kinetically by photons in e.g. compton scattering (http://en.wikipedia.org/wiki/Compton_scattering). Thats the idea behind a "black-body" which will absorb ANY wavelength of light incident upon it--now there aren't any true black-bodies besides black-holes, but lots of things are close (e.g. large metals, carbon/silicone aggregates, plasmas, etc). There are also QFT effects to consider, e.g. pair-production, etc.



    Yes, definitely unclear to me... If its clear to you, then please explain--you'll very likely get a Nobel prize for it. So, well done.
    From my knowledge, even though photons are clearly effected by gravity (e.g. lensing, etc) their "non-locality" might prevent them from generating their own gravitational fields. Additionally, because they have no rest-mass, only mass in the form of momentum, if they do create gravitational fields they would definitely be different from classical G-fields.

    It is definitely possible for photons to create gravity, I would even say likely. Photons can not be dark matter however.
    One of the main problems with photons as dark matter is the same as neutrino's for dark-matter (one of the older ideas), which is that they are "hot." While dark matter seems to be "cold."
    Dark matter needs to have decoupled from normal matter very early after the big-bang to produce the observed CMB anisotropies, and galaxy/cluster sizes.
    Also, dark matter can't be traveling uniformly at the speed of light (like photons) because they clump together in galaxies and clusters (like Zwicky's initial observations), or more clearly in something like the bullet cluster (http://en.wikipedia.org/wiki/Bullet_cluster)

    In summary: photons interact VERY STRONGLY with matter (the opposite of dark matter), they also travel very very very fast (unlike dark matter), and finally, although photons might create gravity, its certainly not enough to account for the missing mass problem (e.g. the rotation curves of galaxies).


    Dramatic-much?
     
  6. Aug 8, 2010 #5
  7. Aug 8, 2010 #6
    Thank you. I got an answer out of you.

    Also, dark matter can't be traveling uniformly at the speed of light (like photons) because they clump together in galaxies and clusters (like Zwicky's initial observations), or more clearly in something like the bullet cluster (http://en.wikipedia.org/wiki/Bullet_cluster)

    It was worth the ridicule.

    Silence about the rest does not indicate agreement.
     
  8. Aug 12, 2010 #7
    Hi Zhermes and agnifire,
    I like your topic on whether "photons influence other bodies through gravity"; whether "photons could be dark matter"; and what is the nature of dark matter eg. "dark matter needs to have decoupled from normal matter.
    I always believed that Einstein showed that light coming from distant stars, passing close to the sun, are gravitationally affected by the sun. Since the gravitational force can only act between matter, there has to be some form of matter in the photons that make up the light coming from distant stars. It is also obvious that the matter in the light (photons) is not normal matter, it has no rest mass. However, could it not be measured by the energy it contains? According to Einstein E = m c^2; and the energy of a photon is: E = h f; where h stansds for a Planck constant and f for the frequency of the photons. Thus mass of a photon is: m = ( h f ) / c^2; However this form of mass in a photon consists of quanta particles and since quanta travel at the speed of light, it is in its own dimension, quantum dimension where its time dimension is zero according to Einstein's time dilation, relativity theory. Since the quanta particles are in a different dimension , it is not observable or directly measureable from our fourth dimensional universe.
    My understanding of science is that all matter, forces and energies can be measured in the quanta dimension and if the quanta particle has some form of mass, non relativistic mass ,but which is both gravitaional and kinetical, it is possible to suggest that dark matter could be this quanta mass not measurable from our fourth dimensional universe.
    Yours cosvis.
     
  9. Aug 12, 2010 #8

    Vanadium 50

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    Personal theories are not discussed on PF.
     
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