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Dark Matter and Eternal Inflation

  1. Aug 27, 2012 #1
    Before i begin, i will note that i truly don't have any idea of what i'm about to ask, but the questions elude me so ask i must.

    Firstly, Dark matter: finding it on earth.
    I've just finished watching a documentary on mapping our universe and within the program was shown a theory of trying to detect dark matter using lights under water and several swimmers, moving the lights and causing displacement.
    Images were consistently taken in an effort to 'map' dark matter in accordance to the distortion of the pictures.

    Now my thoughts on this from another angle, when two area's of different levels of heat meet, they cause a distortion of light within the air.
    i'm aware that dark matter travels through everything so either theory should in effect be equal, but i believe that trying my current theory would possibly deduce the amount of variables, and possibly give better results?


    Now Eternal Inflation,

    The idea that there are infinite universes which occasionally like bubbles if they collide leave a bruise.
    What about the theory of multiple universes becoming one, and expanding into one another,
    as appose to just colliding and leaving a bruise, they join.

    Your thoughts please.
  2. jcsd
  3. Aug 28, 2012 #2


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    I don't know what you were watching, but it sounds absolutely ridiculous. I don't think the distortions from dark matter would ever be observable in this manner unless dark matter clumped together and was very very dense, much denser than the Earth is. Plus the water itself would cause plenty of distortions just from the motion of the cameras and swimmers. Do you have a link to this documentary?
    Hot air and cold air have different refractive indexes, and when you have a boundary between the two the light is bent.

    What theory are you referring to? That air causes distortions? We already know about this and any experiment would need to account for that or avoid it.
  4. Aug 28, 2012 #3
    My own as such, yes hot and cold air have different refractive indexes, but is it possible that dark matter is in effect here, with it playing a part in those refractive indexes?
  5. Aug 28, 2012 #4


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    Not a chance, it doesn't work like that. It only interacts through gravitation which would manifest differently.
    Enough dark matter to cause a noticeable effect here on Earth would need to be a very large amount and it would need to clump together in high densities, something which we are almost certain does not happen.

    Sorry, I can't watch that, I'm not in the UK and it won't let me. I haven't seen the documentary, nor the experiment, so I obviously cannot say anything with 100% certainty, but it sounds like nonsense unless it is an analogy for something else.
    Last edited: Aug 28, 2012
  6. Aug 28, 2012 #5
    I didn't actually watch the documentary, but that sounds more like an analogy of how dark matter can be observed through gravitational lensing.
  7. Aug 28, 2012 #6
    i see, beginning to click together now, so that said adapting on my original theory,
    gravitational lensing is the distortion of matter between a distant source and an observer, with the analogy used in the documentary of using water as the medium, could you not use the different refractive indexes from the hot and cold air in the same way?
  8. Aug 28, 2012 #7
    in terms to my other theory on eternal inflation,
    it has now been discovered that our universe is expanding at an increasing rate,
    could this not be due multiple universes as appose to colliding instead joining causing this increase in expansion at a hastened rate, which will increase in speed as more join?
  9. Aug 28, 2012 #8
    By "same way", do you mean as an analogy to gravitational lensing? I suppose you could.

    No. What makes you think this is possible / if it were possible, it would happen / if it would happen, it would have this kind of effect?
  10. Aug 28, 2012 #9
    yes, that is that i was getting at, initially to be honest, but i lacked the understanding to put it across that way.
    really do wish i'd gone into physics.


    well i was thinking about bubbles, and there merging,
    two bubbles becoming one, now i know that is limited.
    but theoretically imagine a bubble without a wall, if that were to meet with another bubble it would simply become one, and all of a sudden the distance between say the center of the original bubble and the edge suddenly increases at a rapid rate.

    i believe if there are multiple universes this could be a possibility as the universe as far as i know doesnt have a wall, so i believe this effect is a possibilty.
  11. Aug 28, 2012 #10
    Ah yes, now I understand what you mean. No it's not possible (and it wouldn't work like that even if it were :). There are two problems (that immediately come to mind):
    first, in eternal inflation, the bubbles are suspended in a kind of a foam which is expanding much much faster than the bubbles themselves. Any collision between two bubbles would be extremely rare
    and secondly, and maybe more importantly, we know that the objects we observe in the night sky have been in causal connection with our little patch of the universe for a very long time (because the temperature of cosmic microwave background is almost entirely uniform in every direction). If there were regions of space which have been introduced to the universe later, that would be immediately obvious from all the astronomical data.
  12. Aug 28, 2012 #11
    Clamtrox, thankyou.
    Head shake of approval here, very rare thing.
  13. Aug 28, 2012 #12


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    Gravitational lensing is the result of light passing by a gravitational source such as a massive galaxy cluster in such a way that the cluster acts like a lens. It has nothing to do with distortion of matter. And yes, the hot/cold air acts like a lens as well. However we cannot just manipulate it at will to form an air lens.
  14. Aug 28, 2012 #13
    Darkkith/Clamtrox, The prog was a BBC production talking about the use of gravitational lensing to map the location of dark matter in a small slice of the sky / universe. I'm sure you have seen the map - it's by an English cosmologist, also by the name of Ryan I think.

    Ryankffx, the water was just an analogy (as already mentioned). Imagine if the guy was looking at the pool & could see the distorted lights but not the water. He could still carry out some measurements /calculations about the water based on the amount and type of distortion that he could see, even if he knew nothing about the water. Space / the universe is like that in that he could map the dark matter based on the distorted light even without knowing where the dark matter is.

    In relation to the second part of your post and the prog's discussion (about the bubble universes), you need to understand that this is very, very, very speculative. The prog didn't really differenciat between the reasonably certain science of the map of dark, and the highly imaginative considerations of what patterns in one piece of data (the WMAP CMBR image) might or might not mean. I would take that part with a healthy dose of scepticism, but I thought the overall prog was good.


  15. Aug 28, 2012 #14


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    Ah, ok. That makes much more sense. Thanks Lino.
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