Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Theories for dark matter

  1. Sep 28, 2014 #1
    What theories attempt to explain the dark matter today?
    The force of gravity is the only thing that interacts with dark matter, the fundamental force "weaker" is gravity however, if she is not weak just reach dimensions that do not have access, dark matter could not be these heavenly bodies dimensions interacting only through gravity that comes to us? There is a theory that says something about it? sorry my bad english
     
  2. jcsd
  3. Sep 28, 2014 #2

    phinds

    User Avatar
    Gold Member
    2016 Award

    Dark matter is discussed here several times a week. I suggest you do a forum search. A good place to start is the list of links at the bottom of this page.

    EDIT: well, in this case, I see the links at the bottom of the page aren't that good for your specific question, so just try a forum search. Have you done any research on your own?
     
  4. Sep 28, 2014 #3

    Drakkith

    User Avatar

    Staff: Mentor

    The major theories are Cold Dark Matter (CDM) and Modified Newtonian Dynamics (MOND). To my understanding, CDM fits the overall observational data better than other theories, but MOND agrees better in a few certain areas such as explaining galaxy rotational curves.

    I'm not sure which theory explains gravity as interacting in multiple dimensions but I have heard of this before.
     
  5. Sep 28, 2014 #4

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Leaking gravity theories have popped up from time, sometime to explain dark energy, sometimes to explain why gravity is so weak compared to the other three fundamental forces, sometimes both and sometimes for other reasons. The most recent to come to mind was offered by Georgi Dvali in
    http://arxiv.org/abs/astro-ph/0105068, Accelerated Universe from Gravity Leaking to Extra Dimensions.
     
  6. Sep 28, 2014 #5

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Compact objects lead to gravitational lensing - astronomers frequently see gravitational lensing from stars, 5 times this rate from invisible objects would be extremely obvious. Whatever dark matter might be, it does not simply have dark equivalents to our stars.
     
  7. Sep 28, 2014 #6

    phinds

    User Avatar
    Gold Member
    2016 Award

    Why would you assume a dark matter star is 5 times as heavy as a matter star? Yes, there is 5 times as much of it in the universe, but that seems irrelevant to your assumption. There are plenty of matter stars that are more than 5 times heavier than sol, for example.

    I do NOT think there are dark matter stars, I'm just questioning your logic here.
     
  8. Sep 29, 2014 #7

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Where do you see 5 times as heavy? I compared the rate of lensing events, which corresponds to the number of stars. Yes the ratio is closer to 4 - whatever. As long as the mass distribution would be the same (= the scenario discussed in my post), details of this distribution do not matter.
     
  9. Sep 29, 2014 #8

    phinds

    User Avatar
    Gold Member
    2016 Award

    Ah ... I did misread/misinterpret what you said. Thanks for that correction.
     
  10. Sep 29, 2014 #9
    Was dark matter around prior to the Big Bang or a result of the Big Bang?
     
  11. Sep 29, 2014 #10

    phinds

    User Avatar
    Gold Member
    2016 Award

    This is a contradiction in terms. The big bang theory says that NOTHING was around before the Big Bang Singularity. EVERYTHING was a result of the BB. There are other theories, but you specifically asked about the BB.
     
  12. Sep 30, 2014 #11

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    DM was not around until after the BB. The universe was so hot immediately after the BB, nothing but energy could exist.
     
  13. Oct 1, 2014 #12
    DM was not around until after the BB. The universe was so hot immediately after the BB, nothing but energy could exist.

    Although not related to Dark Matter your reply was partially "The universe was so hot immediately after the BB, nothing but energy could exist." From reading about the Higgs-Boson the particle that gives other particles their mass comes into existence and then exists existence in very short time frames. Could the Big Bang have created these particles or could they be part of Dark Matter giving particles their mass a few minutes after the Big Bang had occurred and cooled down?
     
    Last edited: Oct 1, 2014
  14. Oct 1, 2014 #13

    Drakkith

    User Avatar

    Staff: Mentor



    The higgs boson does not give mass to particles. It is the interaction with the higgs field that does this. The higgs boson is simply an excitation of this field, much like how a photon is the excitation of the EM field.



    The higgs boson is not dark matter, but they probably existed in the very early universe when the temperature and density was high enough. As the universe expanded, the density dropped and the universe cooled until it was no longer possible to create them, and the remaining higgs bosons decayed very quickly.
     
  15. Oct 9, 2014 #14

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Bear in mind there is a difference between particles and virtual particles.
     
  16. Oct 9, 2014 #15
    It is my understanding that a Gluon Soup has been briefly created in the LHC. Is there hope that the LHC could conceivably create Dark Matter? and if so, how would we know?
     
  17. Oct 9, 2014 #16

    Drakkith

    User Avatar

    Staff: Mentor

    We'd see energy missing from the collision products.
     
  18. Oct 9, 2014 #17

    phinds

    User Avatar
    Gold Member
    2016 Award

    looks like the OP was a drive-by
     
  19. Oct 9, 2014 #18

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    There are many theories predicting particles that could be seen indirectly at the LHC. Typically the searches look for heavier dark matter particles decaying to lighter dark matter particles plus some regular matter. The detector then sees this regular matter together with an imbalance in momentum (as total momentum is conserved, but at least one invisible particle escapes in some direction and is not detected).
     
  20. Oct 10, 2014 #19
    Thank you Drakkith and mfb for your replies, especially the decaying component of which I was unaware. This is rather exciting isn't it? What a literally marvelous instrument is the LHC!
    Speaking of which, though skirting OT (hopefully less a problem if OP is a drive by) given the LHC and so many ambitious and successful ESA ventures, is there any evidence that the so-called "Brain Drain" of the 60s and 70s has begun to reverse direction? I know the US has a moderate constituency at LHC but can't help but wonder if the reduced emphasis (or at least budgeting for it) here has begun to take it's toll.
     
  21. Oct 10, 2014 #20

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    High-energy physics is dominated by Europe now. The US still has some neutrino experiments in particle physics. And many interesting research projects in other areas, including NASA. Please start a new thread if you want to discuss that in more detail.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook