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Could Dark Energy be Dark Matter cooling?

  1. Mar 19, 2010 #1
    Hi Clever People,

    I've been watching an amazing program about dark matter, dark energy and dark flow. I thought there were questions that should have been asked, but then I'm a website designer - what do I know!

    So... as an interested non-physicist, my apologies if this question is ridiculous...

    If Dark Energy is what is causing the 'empty' regions of deep space to expand / accelerate, could it be due to Dark Matter cooling down? Or heating up? Or perhaps even multiplying - like cell-division?

    I mean, if we're not quite sure what Dark Matter is except that it behaves totally differently from anything else, could it behave as above?
     
  2. jcsd
  3. Mar 19, 2010 #2

    mathman

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    Your idea is completely far out. Dark matter is stuff and it is manifest by gravitational effect only. Dark energy is a complete mystery - accelerating the expansion of the universe.
     
  4. Mar 19, 2010 #3
    Dark energy is also called the cosmological CONSTANT...it is a constant is all frames of reference and so cannot be heat energy....you might gain an understanding of this by reading about the Unruh effect...
    how Einstein figured out it is a constant I don't know, but there seems to be general agreement it IS a constant....

    You might find some interesting reading here.

    http://en.wikipedia.org/wiki/Dark_energy

    Of course, most of the time most physicsts have over history been proven WRONG....as new theories are developed and tested....so who knows...
     
  5. Mar 19, 2010 #4
    How certain are we that the cosmological constant is the same in all regions of space? In other words, is it possible that this "dark flow" that's recently been in the news is related to part of the universe expanding faster than neighboring regions? It seems logical to me that if there was inflation in the early universe then there is the possibility that regions of space are still undergoing inflation although these regions may be beyond our observable universe.
     
  6. Mar 19, 2010 #5

    PhanthomJay

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    Now I was led to believe, perhaps mistakenly, about 10 years ago, as proposed, I think, by the M-Brane theorists, that Dark Matter (or Dark Energy, which is just a different manifestation of dark matter, per E=mc^2) was a result of ultra high frequency short wave gravity waves escaping, thru the miniscule (in the order of the Planck length) higher order spatial dimensions of spacetime, from matter of another parallel universe. Is Brane Theory (M-Theory) dead??
     
  7. Mar 20, 2010 #6

    mathman

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    Dark energy is not a manifestation of dark matter. Even calling it energy is misleading. It seems to be related to the cosmological constant. Einstein made it up as a fudge factor to keep the universe static - which people believed at the time. He later called it his biggest blunder after the expansion of the universe was discovered.
     
  8. Mar 21, 2010 #7

    PhanthomJay

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    So what do you call the energy equivalence of dark matter, per E=mc^2??
     
  9. Mar 21, 2010 #8
    Calling it Dark Matter is misleading, it would be better named 'missing matter'. Our current theories of gravity do not hold up with the current mass in the universe. So either our theories of gravity are incorrect, or there is 10 times the amount of matter in the universe then there appears to be. Obviously we aren't going to go back the the drawing board with gravitational theories, so abracadabra, dark matter.

    In other words there is no 'dark matter' we don't know what we're missing and we just call it dark matter.

    So you can't actually have statistics or theories for it, since we haven't discovered it.
     
  10. Mar 21, 2010 #9

    PhanthomJay

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    I don't care if you call it dark matter or missing matter, I'm just wondering if some clever physicist has coined the term for the energy equivalence of the 'missing' matter , per E=mc^2, if in fact, the dark matter has mass (does it?) and obeys the laws of Physics (does it?).
     
  11. Mar 21, 2010 #10

    mathman

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    Dark matter has mass - that is about all we know. It is detectable by its effect on galaxies and galaxy clusters.
     
  12. Mar 21, 2010 #11

    PhanthomJay

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    So if it has mass, it has energy, assuming it obeys the Universal Law of Physics, as we know it. Maybe we don't know if it obeys these laws? If it does, maybe i'll coin a word for it and become famous. Incidentally, is dark energy the latest catchword foo what used to be called 'vacuum' energy?
     
  13. Mar 21, 2010 #12
    Dark energy looks suspiciously like inflation generated by all those mysterious particles spotaneously popping out of quantum foam uncertainties.
     
  14. Mar 22, 2010 #13
    We do not 'know' dark matter has mass. We 'know' that there is a unexplainable force causing more gravity then the known mass acounts for. Really it is much more likely that our theories on gravity are wrong then an invisible all powerful 'mass'-ive force holding the universe together.

    That sounds more religious then science, but the human race has a tendency to make up stuff when they can't explain what they see. That is where dark matter comes from, the human imagination. So asking if the imaginary mass has energy has a very simple answer: It has imaginary energy!

    All this energy comes from unicorns that live in an invisible planet made of dark matter.

    Ain't science great!!?
     
  15. Mar 22, 2010 #14

    mathman

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    Since there is no evidence (except what may be happening inside black holes) that general relativity is wrong, your assertion seems less likely than the existence of dark matter, particularly since astronomers seem to be able to get a picture of its distribution.
     
    Last edited: Mar 22, 2010
  16. Mar 22, 2010 #15
    Umm.... What is your evidence that my invisible unicorn theory is wrong?
     
  17. Mar 23, 2010 #16
    Actually, we know a bit more about dark matter. It doesn't have pressure (i.e. it doesn't interact electromagnetically), and it concentrates around galaxies. Different gallaxies have different percentage of dark matter content, so there definitely is something around we don't see - not just our theories are wrong.
    So, when we already have started to measure dark matter density, it is not very wise to claim it was created by imaginary unicorns.

    About dark energy - we don't even know whether the universe is accelerating or slowing down! Our guessing is based on supernova theories (we don't know if they are correct) and actual experiments are so few, that saying anything about the Universe shape is way too soon.
    The only thing we know - galaxies are red-shifted. Anything else is just imaginary unicorns. We don't know the relation between distance and red shift, because we can't determine neither.

    So, don't get depressed. We can bake almost any theory about Universe geometry and no one can proove us wrong yet :).
     
  18. Mar 23, 2010 #17

    Ich

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    Come on. Somehow you missed the last 80 years?
    There's SN1a, WMAP, BAO, nucleogenesis... all of which give independent evidence for a coherent picture. It's not like LCDM depends on a single, poorly understood observation.
     
  19. Mar 23, 2010 #18

    Janus

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    You are vastly understating the body of evidence that exists in support of the dark matter model.

    It's not as if nobody has tried to come up with alternative theory of gravity to explain it, it just that every promising one has been shot down by new observation that can't be made to fit. The DM model has not been shot down by these new observations which is why it still survives.(in fact, each new observation seems to increase the likely-hood of its being correct)
     
  20. Mar 24, 2010 #19

    JcX

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    The idea of dark matter comes from mathematical model of gravitational force.
    Scientist suggests that there must be matter that we don't see in our universe, maybe between galaxies that exert the gravitational effects that we feel.
    The content/percentage of dark matter is chosen to fit and balance all the gravitational effects that has been observed in the universe (expansion of universe, perturbation of orbits, etc).
    We predicted the existence of them, but we can't be really sure of what dark matter is.

    Some theories such one those who suggest multi-dimensional universe says that dark matter is actually some matters in other universe. String Theory says that only gravitons are able to escape from the membrane of the dimension, hence only gravitational forces are able to penetrate between dimensions. Living in this dimension, we can feel the gravitational effects from other dimension, but we don't see them, that's why we called them Dark Matter.
    That's one of the explanation that I liked a lot... although...... it's hard to imagine.
     
  21. Mar 24, 2010 #20
    All our calculations of distance are based on supernova theories. All this "acceleration" may as well be an error in our understanding of star dynamics.
     
  22. Mar 24, 2010 #21
    The basic ideas of the standard model are well established. However what is the most ridiculous part of this standard mode? It is inflation! The fundermental properties of the initial start is very well understood, then we have our universe. It seemed so natural to think of a process that gets from an
    infinitely small high energy point towards the universe we see today.Hey presto we have inflation. How can any scientists be taken seriously when they come up with such a crazy conclusion. They'll have us beleive that spacetime expanded faster than the speed of light to get from the big bang to where we are today with a total disregard of Einsteins ideas.
    Then we have Quantum theory that says that spacetime is a neutral summation of positive and negative forces. The uncertainty principle allows these forces at extremely small scales to momentarily obtain large energies. There are claims that particles within spacetime can briefly pop out of absolutely nothing.
    Now we have dark matter and dark energy that fills all space which no one understands. The phenomena affects the speed of galaxies and seems to have a repulsive force.

    Surely it's about time that the ideas of Sir Fred Hoyle. Who I consider should be recognised as the greatest scientist since Albert Einstein should have his last theory of Quasi Steady State theory re-examined seriously. It brings together the great ideas of the Standard Theory and the best of the Steady State Theory together.

    To me it is obvious... the dark energy is inflation the byproduct of universe full of MINI BANGS. Constant creation occuring within the fabric of space, existing within a dynamic Universe with no beginning or end. A universe where matter and spacetime are curved back from the largest scales.. to feul the energies within the quantum world at the smallest scales.

    Dark Energy IS inflation. It has to be.
     
    Last edited: Mar 24, 2010
  23. Mar 25, 2010 #22
    dark matter persists because it is not a theory. It has no actual attributes other then a mathmatical model. What is it? By definition it is 'whatever is causing the unknown gravity'. I do not think that a 'whatever' should be considered a viable scientific theory. Again how can you prove my invisible unicorns wrong. Just because there is evidence that other theories are wrong does not mean my unicorns do not exist. In fact since other theories are wrong my unprovable unicorns are more likely to be right.

    You have mentioned other observations that point to the fact that there is something we do not understand. I am not saying that 'something' isn't causing what we see, I am saying it is not 'dark matter'. Dark matter is an undefined identity, it just sounds scientific but has as much base as my invisible unicorn theory. Why couldn't invisible unicorns be causing these effects? Nothing in science actually disallows the existance of invisible unicorns, what makes invisible unicorns less viable then dark matter.


    BTW I am not a multiverse theory fan either, nor a string theory fan, for the same reasons. Mathimatical models should explain observations not create them.
     
  24. Mar 25, 2010 #23

    bapowell

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    Really? Why do you say this? Most modifications to gravity theory don't offer plausible alternatives to dark matter. The bullet cluster http://en.wikipedia.org/wiki/Bullet_Cluster practically closed the book on alternative theories of gravity in favor of particulate dark matter. [/QUOTE]

    The only thing stupid about dark energy is its name. We know that vacuum energy can lead to accelerated expansion of spacetime. This is what happens during inflation. What's happening now is fundamentally no different. You should learn a bit more about the science before you make such heavy-handed opinions about things.
     
  25. Mar 25, 2010 #24

    bapowell

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    This isn't correct. There is evidence from the cosmic microwave background that the present day universe is undergoing accelerated expansion.
     
  26. Mar 25, 2010 #25

    bapowell

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    You clearly don't have a good grasp on cosmology, let alone inflation. I don't quite understand where your hubris comes from, but I'll try to explain things. The first lesson is that Einstein's special relativity applies locally to inertial observers. It does not apply to cosmology. For this we need general relativity. Here, it's perfectly OK for space to expand at superluminal rates. The stuff in the universe must of course obey v < c locally, and all of it does -- even during inflation.[/QUOTE]
    Something doesn't seem right with this. Could you elaborate?

    Right. Might the dark energy that nobody understands be the large energies associated with the quantum vacuum??
    It could be!
     
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