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What has mass, but is not considered matter?

  1. May 19, 2012 #1
    Hello,

    I am wondering, besides the W and Z bosons of the weak force, if there is anything else in the universe that has mass, but does not qualify as matter.

    neutrino's? hmm... maybe... anything else?
     
  2. jcsd
  3. May 19, 2012 #2
    By what definition of matter do W and Z bosons not qualify?
     
  4. May 19, 2012 #3

    Dale

    Staff: Mentor

    The usual definition of matter is something that has mass and takes up space. Since W and Z bosons don't follow the Pauli exclusion principle they don't take up space and therefore are not matter. At least, that is my understanding of the justification.

    Neutrinos are fermions so they take up space and have some small mass.
     
  5. May 19, 2012 #4
    So neutrino's are actually instances of matter,...
    so, besides the W and Z boson's of the weak force , there is no exception ? -there is no instance of mass exclusive of matter??? so I can say, 'excepting the W and Z boson's of the weak force, there is no instance of massive phenomena outside the context of a material body' ??????

    ><
     
  6. May 19, 2012 #5
    Photons and Gluons have mass, they just have no rest mass. I think mesons will also qualify, being bosons(?)
     
  7. May 19, 2012 #6
    The Higgs boson has (rest) mass, and is a boson, so it won't qualify as matter in your classification scheme.
     
  8. May 19, 2012 #7
    They are composite bosons, however. If you try to squeeze them into a tiny volume, then they would start feeling their internal structure, containing 2 fermions, so the Pauli exclusion principle will kick in. Some are charged, so they repel via the electrostatic force.
     
  9. May 19, 2012 #8
    ah, yes, rest mass, this is what I meant.

    So, please, is this a correct statement:

    "everything with REST mass is also matter"
     
  10. May 20, 2012 #9
    I would say yes, but, as far as I am concerned, that would not mean that something without rest mass is not matter.
     
  11. May 20, 2012 #10

    Dale

    Staff: Mentor

    Not according to the usual definition of matter. The W and Z bosons have rest mass, but are not considered matter since they do not take up space. Similarly with the Higgs boson, should it be discovered.
     
  12. May 20, 2012 #11
    All types of mesons (particles made of one quark and one anti-quark), of which there are many kinds, and all of which all have mass, have integer spin and therefore don't follow the Pauli exclusion principles.
     
  13. May 20, 2012 #12

    Dale

    Staff: Mentor

    You don't even need to go to something as exotic as mesons. You can consider 4He nucleii which are also bosons, but much more stable than mesons. Their bosonic properties are important in superfluidity.

    However, even though they do not follow the Pauli exclusion principle at large scales they still occupy space. If you try to compress a composite bosonic fluid to densities smaller than the internal structure of the underlying fermions then the Pauli exclusion principle does come in. Thus bosons composed of fermions do occupy space.
     
  14. May 20, 2012 #13
    But you still cannot put a bunch of mesons of same kind at the same place, since at close distance, the quarks will Pauli exclude themselves.
     
  15. May 20, 2012 #14
    I would say matter is everything that is described by an action. In this respect, it has internal degrees of freedom, and it evolves under deterministic principles, and it is coupled to other matter via interaction actions.
     
  16. May 20, 2012 #15

    Dale

    Staff: Mentor

    I have answered above using the standard definition. The one you proposed is not the standard definition, but I have no objection in principle. Or rather, I don't like semantic debates.

    I would point out that your definition classifies light and even gravity as matter. I don't know if that was your intention, but I think that most people would reject such a classification.
     
    Last edited: May 20, 2012
  17. May 20, 2012 #16
    Yes, this was exactly my intetntion! To clasify light and gravitation as a form of matter. English is not my native language, but, I think one needs to distinguish between matter and substance. I think what you defined as matter is actually substance. Fields are also a form of matter in a broader sense of the word.
     
  18. May 20, 2012 #17

    Dale

    Staff: Mentor

    As long as you realize that is very non standard and not what is usually meant by the word "matter". The deliberate use of such a non-standard definition will cause difficulties in communication, but isn't wrong per se.
     
  19. May 20, 2012 #18
    ><
    basically I am looking for a bottom-line definition of matter, (something that 'takes up space',) as exlcusive from anything else that exhibits only the property of mass.

    I think that the mass-energy equivalance principle really roughs up this delimitation.

    but... I suppose it is the case that, fundamentally, what is essential for the formation of matter is an atomic structure? (but we said that neutrino's are 'matter'... if they take up space, even so little, are still so dominant and pervasive in the universe, then surely this would mean they would interact with regular matter on a regular basis?
     
  20. May 20, 2012 #19
    --ps, do you assume that neutrino's are considered matter as stemming form the assumption of the mass-energy equivalance principle??
     
  21. May 20, 2012 #20
    I guess my definition of matter is due to the following philosophical theory:
    Materialism
    noun
    2. the philosophical theory that regards matter and its motions as constituting the universe, and all phenomena, including those of mind, as due to material agencies.

    The definition of matter that you are alluding to is:
    matter
    noun
    1. the substance or substances of which any physical object consists or is composed: the matter of which the earth is made.
    2. physical or corporeal substance in general, whether solid, liquid, or gaseous, especially as distinguished from incorporeal substance, as spirit or mind, or from qualities, actions, and the like.
    3. something that occupies space.
    4. a particular kind of substance: coloring matter.
    5. a situation, state, affair, or business: a trivial matter.
     
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