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Dark matter = plasma?

  1. Mar 29, 2005 #1
    When I was doing science fair projects in astrophysics, sometimes I felt like asking my mentor random astronomy questions that I had in my mind. He was a very great man and taught me a lot about astronomy and kept my interest in the subject alive such that I decided I wanted to major in astrophysics in 9th grade. I am doing just that now. But I remember asking him what he thought about dark matter and what it could be composed of. I remember him saying something about how it could just be an unknown form of plasma. I am just wondering what others think about this, and if there are any advancements made in dark matter research that supports this argument or if we have discovered just the opposite.

    Thanks for your time.

  2. jcsd
  3. Mar 30, 2005 #2
    A plasma can in principle never be completely dark because there will be radiation emitted as the protons and electrons recombine. However, if the plasma is so dense and energetic that no individual atoms can form (like in the interior of the sun), then there won't be any recombination and radiation. Of course, towards the boundary of a plasma volume the density will become less, so there would be radiation from there, but if the plasma energy is very high (e.g. for very high masses of the plasma volume), the recombination probability becomes very small i.e. there won't be much radiation and the latter would anyway not be in the visible region but in the ultraviolet or x-ray and hence may be easily absorbed.
    So in this sense it is well possible that a large plasma mass at the center of galaxies might go undetected.

    Another point is that plasmas can be associated with currents and magnetic fields, which might explain for instance galactic rotation curves usually associated with dark matter (see my webpage http://www.physicsmyths.org.uk/darkmatter.htm ).
    Last edited: Mar 30, 2005
  4. Mar 30, 2005 #3


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    Thomas2, that doesn' explain anything and smacks of plasma cosmology, which I perceive you are asserting. I think it's just plain wrong. You have to invent so many ways to avoid violating accepted models that it crumbles under its own weight. I am, however, intrigued by the title of your web page - physicsmyths - it lives up to the name.
  5. Mar 30, 2005 #4


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    The reason you see plasma in the Sun is because the Sun is churning out immense quantities of energy that makes maintaining that state possible. I can think of no plausible energy source that would sustain the massive amount of plasma necessary to account for dark matter.

    I suspose that you could call a sea of WIMPS a plasma, but as they say, calling a tail a leg doesn't give you a dog with five legs.
  6. Mar 30, 2005 #5
    Darkmatter's true nature revealed! ;-)

    I've finally figured it out.
    Dark matter doesn't interact with normal matter (except by way of gravity).
    Dark matter can't be seen, or touched, or felt, but it's effects on the world are very real. So it occurred to me to ask - what in the world could not be felt, or seen, or touched, but still have such profound effects on the world around us? And it struck me...

    Dark matter is, in reality, the physical manifestation of B.S.!

    And it makes sense it you think about it. Most of our universe is comprised of B.S. B.S. is everywhere around us. 90% of this very post is comprised of B.S. Most of what we think is built on B.S. Most of what we talk about is comprised of B.S.
    So in reality science is simply catching up to what all of have known for thousands of years - that this existence of ours is comprised of - by far - mostly B.S. with trace amounts of reality mixed into it.

    Which brings to mind a disturbing thought.
    Where would we be without politicians and advertising executives?
  7. Mar 30, 2005 #6
    write a paper and contribute to your dark matter then...
  8. Mar 31, 2005 #7
    I assume you are referring to nuclear fusion in the sun here. However, contrary to what most people believe, this is not at all necessary, neither for maintaining the plasma state nor for preventing the sun from collapsing. The point is that the kinetic energy of the particles in the sun due to gravity is high enough to do this (you can easily calculate from the mass and radius of the sun that the kinetic of the particles corresponds to a temperature of 11 million degrees; see my webpage http://www.plasmaphysics.org.uk/research/sun.htm ).
  9. Mar 31, 2005 #8
    Could a failure of general relativity do away with problems such as dark matter and dark energy? This is because general relativity is the central core of whole this.
  10. Mar 31, 2005 #9
    It's a nice idea, but plasma is one thing that dark matter certainly can't be. In one word, the reason is "charge".

    Plasma, as we understand it, is a state of matter in which high temperatures overcome the electromagnetic attraction in matter - the force that attracts negatively charged electrons to their positively charged nuclei. So one of the defining characteristics of a plasma is that it consists of charged particles.

    Meanwhile, one of the defining characteristics of charged particles is that they interact strongly with light.

    So, plasmas interact strongly with light, and the defining characteristic of dark matter is that it doesn't interact with light at all (hence "dark"). So the dark matter can't be a plasma.

    Incidentally, the famous "cosmic microwave background" radiation is caused by plasma scattering in the early universe. It is an imprint of the light that was scattering throughout the universe when it was just 400,000 years old. That was the moment when the universe cooled sufficiently for the plasma to recombine into neutral atoms, and light could suddenly travel unimpeded.
  11. Apr 5, 2005 #10
    if it does intract with normal matter why cant we find any by measureing its gravitional force and if there is soooo much of it wouldnt we directly feel its affects??
  12. Apr 5, 2005 #11


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    It probably does interact with normal matter, just very, very weakly...so much so that gravity is the only way we've been able to detect it thus far. I'm not sure what you mean by your second question.
  13. Apr 5, 2005 #12


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    The weakly interacting aspect of dark matter applies not only to ordinary matter, but to itself as well. When ordinary matter gravitates together, it clumps forming familiar objects like stars and planets. When dark matter gravitates toward matter or other dark matter, it passes right through the other particles, hence there is no clumping. It merely forms a diffuse cloud of yo-yoing particles that is only modestly denser in the middle than around the edges. It is only easily detectable in large amounts - like clouds the size of galaxies.
  14. Jan 10, 2009 #13
    Saw an ad for this guys site at the top of the physics forum page.
    Jay Alfred is his name.
    Holding our skepticism at all his many hypothesis on dark matter aliens ghosts etc in check.....
    Is there any basis for possibility in his hypothesis that Super Symmetric "dark matter" particles are mostly behaving as a plasma in our universe?
    The models are suggesting that its "warm dark matter" rather than hot or cold. How hot is warm? Its distribution does make it look like its not inclined to bond in solids, liquids as readily as normal matter.
  15. Jan 15, 2009 #14
    What does MonstersFromTheId mean by B.S.? And to answer silverslith, plasma life is not possible - at least in our current terms. Peter Ward discussed that in Life as we do not know it. Also, Why couldn't dark matter be plasma? I remember numerous sources saying that 99.99 percent of the universe is plasma. There are numerous kinds of plasma out there.
  16. Jan 15, 2009 #15


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    Maybe the Dark Matter Faeries are assembling 99.99% of our universe into plasma/matter factories. Or maybe not...
  17. Jan 15, 2009 #16


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    Necropostia, but I will let my response abide until some mentor decides to remove it.
  18. Jan 16, 2009 #17


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    That makes no sense at all. Plasma would be detectable not only because it CAN emit EM radiation, but also because it would exhibit electromagnetic interaction since it would be charged! All the properties of Dark Matter that we know of today indicates that these are not charged particles.

    The fact that we CAN already detect these plasma in many parts of the universe clearly indicates that these CAN be detected. These are definitely not dark matter.

    You really ought to study a little bit on all that we know of already about the properties of dark matter before proposing some of these rather outlandish ideas (including the one you posted in the Engineering forum).

    Last edited: Jan 16, 2009
  19. Jan 16, 2009 #18


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    As ZapperZ has already pointed out, plasma (in the usual meaning) is baryonic matter (a slight misnomer, 'cause it also includes electrons, which are leptons).

    An astonishingly wide range of diverse and independent observations are all consistent with the mass-energy universe being composed of dark energy (~70%), dark matter (actually cold dark matter, ~25%), baryonic matter (~4%), and photons and neutrinos (the rest; note that neutrinos are hot dark matter)*.

    I'm not sure what sources you are remembering ("I remember numerous sources saying that 99.99 percent of the universe is plasma"); maybe you could try to dig one up? Perhaps what it said was that the baryons in the present-day universe are mostly (~99%) plasma?

    * black holes are an interesting category ... should they count as baryonic matter? or in a class of their own? Whichever way, they are a trivial fraction of the universe's mass-energy
  20. Jan 18, 2009 #19
    I learned that from my science teacher and from sources online such as this, and this. If they're wrong, why would they teach us in schools that this is a fact?
  21. Jan 18, 2009 #20

    George Jones

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    From your second link:

    "Plasma in the stars and in the tenuous space between them makes up over 99% of the visible universe and perhaps most of that which is not visible."

    This number refers to normal, baryonic matter, not dark matter.
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