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

Elementary particles and randomness

  1. Nov 1, 2015 #1
    From the elementary particles that science has been able to identify until now, are there any that appear to be useless, at least as far as we know?
    Or do all the identified particles play a role in the grand scheme of the universe?
     
  2. jcsd
  3. Nov 1, 2015 #2

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    What do you mean by "useless"? Particles do not have an underlying "purpose" in physical theories. They are introduced because they are needed to provide a good description of how nature works. Asking if there is a "grand scheme" is a religious and philosophical question rather than a physics question.
     
  4. Nov 1, 2015 #3
    What do you mean by "they are introduced"?
    I thought that these particles were actually tangible and had been discovered by means of scientific research, not that they were a theorerical creation for practical purposes.
    "Grand scheme" may not be the right term.
    What I mean, for example, is that we have the quarks and the electron, and that together these particles form atoms.
    Or there is the photon which carries the electromagnetic force.
    Now, are there other particles that science has been able to identify, but to which it was not able to assign a role?
    In other words and as far as we know, the universe would remain the same if these "unassigned" particles didn't exist.
     
  5. Nov 1, 2015 #4

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Physics (and science in general) is about creating a model which describes observations, nothing else. We introduce concepts such as energy, particles, and waves because it gives a good description of what we can observe. If you want to say that these concepts are "real" in any sense of the word, you are leaning more to the philosophical than to the physical side of things.

    This is not true. There is no deeper meaning in quarks and electrons forming atoms and it is not their "purpose" to do so. They have properties which make them do that, which in turn makes them a good description of observations.

    And here you are ore-supposing that there is an electromagnetic force. The implication is in the other direction, photons are introduced because they give a good description of observations, among them the emergence of the electromagnetic forces. There is no deep purpose in the existence of the EM force, it is just a good description of observations.

    Again, this is the wrong question to ask. Any concept in physics simply would not be there if it was not to describe observations, if nothing else the observation of the particles themselves. Physics is not about assigning meaning.

    By definition no. A universe where they did not exist would be intrinsically different simply by the fact that it does not have the same particle content.
     
  6. Nov 1, 2015 #5
    I am not sure I understand all this.
    How can particles be only some kind of concept if we can actually manipulate them and get something out of these manipulations?
    For example, scientists use photons, or at least a particle they call photon, in order to perform the double slit experiment.
    For example, we use electrons to produce electricity, which in turn produces something else, and so on.
    These are not observations, but actions based on the results of former observations.
     
  7. Nov 1, 2015 #6

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    We can manipulate things and we call some of those things particles. For other things, we say "they are made out of particles". That is our description. It is possible to find different descriptions for the same observations.

    The description of the regular double-slit experiment is much easier with a model without photons - with waves.
     
  8. Nov 1, 2015 #7
    A particle which does not interact at all with anything else in any way would be completely unobservable.
    A description of such a particle can't be a part of physics, since physically such a particle is a non-entity.
     
  9. Nov 2, 2015 #8
    Not totally true, you can observe them indirectly in particle accelerators. A stable particle that does not interact with anything well be detectable as a collision of two protons that produce seemingly nothing as a result, or a slew of particles who's energy doesn't add up to the original amount of energy. An unstable particle would also be detectable after it decays, you'd see a a spray of particles seemingly coming out of nothing.
     
  10. Nov 2, 2015 #9
    I agree with that, what I meant was that proposing a particle which has no effect on anything, not even indirectly, is meaningless,
    since as far as physics is concerned it makes no difference whether it exist or not.
    (A bit like adding the term '+0' to the end of a math formula)
     
  11. Nov 2, 2015 #10
    Sometimes "particles" come out of math that aren't real things. Spinon for example, I tend to think of the most elementary particles more of abstract concepts than actual things. Yes, a particle with absolutely no interactions, no structure, or energy, is perfectly valid as far as I know. You can always add zero or multiply by one.
     
  12. Nov 2, 2015 #11

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    How are you planning to produce a particle which does not interact at all in a particle accelerator?

    No it will not, because it will never be produced in a proton-proton collision. If it does not have any interactions at all, in particular it does not have any interactions with the proton constituents. There is a difference between "very weak" and "non-existent".
     
  13. Nov 2, 2015 #12
    Agreed, I retract my posts.
     
  14. Nov 2, 2015 #13
    Backing my initial question was something else.
    As far as I understand, elementary particles appeared sometime after the BB, from the cooling plasma that was there.
    If these particles were created randomly, which was supposedly the case, there must have been millions upon millions of different kinds of particles created, out of which only a tiny number interact and have thus revealed themselves to us.
    It seems to be the way things work in the universe, whatever the scale: random creation of a very large number of something, out of which only a very small number happens to be useful.
     
  15. Nov 2, 2015 #14

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Why should there be millions of different kinds of particles?
     
  16. Nov 2, 2015 #15
    Because if that was not the case, one could wonder about randomness when it comes to the creation of the universe.
    If only the particles that interact and that we have been able to observe existed, that would be an extraordinary coincidence.
    To make a comparison, imagine that instead of the initial plasma, there was a sea of molten plastic which, after cooling, formed blocks of Lego.
    Wouldn't it be incredible if all these randomly created blocks could be used to build, say, a toy car, without any block left on the side because unable to fit in the car?
    In fact, we might expect that only a tiny number of blocks could be used to build the car and that millions of others, with different shapes and sizes would be of no use for this purpose.
    The same could be true for particles.
    Out of a very large number of available particles, only a few would fit in the building of the universe.
     
  17. Nov 2, 2015 #16

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    I think this is somewhere between "philosophy" and "wrong". Can we maybe restrict the discussion to what can be addressed by the scientific method?
     
  18. Nov 2, 2015 #17
    Purpose implies intention ... by whom? ...
     
  19. Nov 2, 2015 #18
    I don't see the philosophical aspects in suggesting that there could be much more kinds of particles than those already observed???
    Having said that, could you explain why this suggestion is wrong?
    It certainly could be wrong but I'd like to know the arguments.
     
  20. Nov 2, 2015 #19
    Maybe I used the wrong word...what about replacing it with creation?
     
  21. Nov 2, 2015 #20
    Ah, well there are some reasonable theories of the existence of particles beyond those which are known and are part of the standard model.
    However these predict the possibility of particles, or objects, which DO interact one way or another with the known ones, or are components of them.
    String theory, Supersymmetry.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Elementary particles and randomness
  1. Elementary Particles (Replies: 6)

  2. Elementary particle (Replies: 14)

Loading...