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What role does the neutrino play?

  1. Jun 3, 2007 #1
    What exactly are neutrinos doing(their purpose)?
  2. jcsd
  3. Jun 3, 2007 #2


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    Hmmm. You need to flesh out your questions a bit more - so that people
    can understand better what you're really asking.

    I don't think any particle has a "purpose" as such. All that physics can
    hope to achieve in this area is to understand what elementary particles
    exist, the details of how they interact with each other, and hopefully
    try to build up a unifying consistent picture of the whole thing.

    Neutrinos were originally "discovered" indirectly, because certain
    particle reactions were observed which didn't conserve energy. I.e:
    the incoming particles has a certain total energy, but the observed
    outgoing particles had a lower total energy. Since energy was known
    to be conserved in every physical process known, the neutrino was
    postulated as a new particle that somehow carried away the excess
    energy - but without being visible to the particle detectors available
    at that time.

    Subsequently, better detectors were built, and neutrinos were observed
    directly. Their interaction with other particles is extremely weak (hence
    it was called the "weak" interaction). Later, people realized that
    this "weak" interaction had to be mediated by another set of particles
    (called vector bosons), just as the electromagnetic interaction is
    mediated by photons. Electrons and neutrinos were recognized as
    two members of a "doublet", which transform into each other
    under a new symmetry group called SU(2)L.

    There's a lot more to it than that, and maybe I'm simplifying it too
    much. I'll leave it at that for now until I understand better what your
    question was really aiming at.
  4. Jun 4, 2007 #3
    As in the protons purpose is to combine with the neutron to form the atomic nucleus. Also what is the neutrino made of, quarks?
  5. Jun 4, 2007 #4
    The neutrino is thought to be an elementary particle. It's a lepton, like the electron.

    Its "purpose"? I'm not sure what you mean there; I'm not sure I'd take such a teleological view of elementary particles!

    In the everyday world, neutrinos mainly only show up in certain types of radioactive (beta) decays. They also play an important role in supernovae.
  6. Jun 4, 2007 #5


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    We do not like to talk about "purposes" in physics, our job is to find out how nature works and also if we can use something for our daily life.

    If you really want a good overview book on elementary particles and other stuff, without so much formulas, I can recomend:

  7. Jun 5, 2007 #6
    So you guys are telling me know one knows what its purpose is? If it has no purpose thats fine with me. But it is one or the other. From what I've read about every other particle they either produce something or change something. Is this the particle that has no function? it just flys around because that's what makes it happy?
  8. Jun 5, 2007 #7


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    1. Particles do not have feelings..
    2. You can not talk about purposes in physics.. it is just our subective opinions..

    But if I say like this, we would know of the neutrino if we could not detect it, so in order to detect it, it must undergo reactions..

    and the answer given by strangerep is very good (again)...
    Last edited: Jun 5, 2007
  9. Jun 5, 2007 #8


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    Don't anthropomorphise fundamental particles. They hate it when you do that.
  10. Jun 5, 2007 #9
    1. You don't know particles lack feelings.
    2. That wasn't a serious question
    3. No one has answered my question. Unless strangerep meant "the neutrino was postulated as a new particle that somehow carried away the excess
    energy" has now been proven to be true. which he didnt make clear.
  11. Jun 5, 2007 #10
    Purpose of neutrino is some kind of equilibrium,

    When a neotron transforms to a proton in the nuclues the following equation becomes true:

    neotron -> proton + electron + anti-neotrino

    in nuclear physics, there must be some kind of conservation,
    1- for energy
    2- for energy
    3- for momentums, and one of those momentums is Spin

    the Spin of neotron is 1/2, and also for proton is 1/2 and electron is 1/2

    so if you didn't add the anti-neotrino which have the spin -1/2 then the conservation of spin will not be fulfilled,

    approximately at 1920 Paule suggested the availability of a particle with spin which equals (-1/2) in the previous equation and said that this particle has a very small mass which tends to zero like photons, and also have no charge, and it's job is only to save momentum

    and due to the low mass and charge, scanning of this particles wasn't possible until 1950-1960 with very high energy and frequency scanners, and his suggestion was true :)

    so about your question (purpose), here is the answer

    the electrons mass is approx. 1/1850 of the proton or neotron, so why it's available while it's mass is negligible, or what it's purpose?

    the answer is like the previous discussion, it's only available to fulfill the conservation of the atoms charge :)

    and put somthing in mind, if you are going to ask about the purpose of every particle let me tell you about names of some particles:

    electron -> anti-neutrino of electron
    positron (anti-electron) -> neotrino of positron
    muon -> anti-neutrino of muon
    anti-muon -> neutrino of anti-muon
    tau -> anti-neutrino of tau
    anti-tau -> neutrino of anti-tau

    all previous neutrinos is only for conservation of spins, and the previous group is named (Leptons)

    also take those particles

    pion, anti-pion, kaon+, kaon-, kaon0, mison+, mison-, quark-up, quark-down, quark-charmed, quark-top, quark-buttom, w+, w-, z0, Lambda, Sigma+, Sigma-, Sigma0, Anti-Sigma0 .............

    Wanna more? if you would like to know the purpose of every one just take 5 courses of nuclear physics :)

    See ya
  12. Jun 5, 2007 #11
    So a neutron decides one day it wants to become a proton and to maintain proper spin a quark farts out a boson which blossoms into an electron and an anti-neutrino? I'm sure this is wrong and I am trying to oversimplify something I can't even see. But yet I just want to know :p Then beyond that what happens to the neutrino? Is it absorbed by something or is it free to live out its life roaming the galaxy?
  13. Jun 5, 2007 #12


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    That's partly because we're still not clear what you're really asking,
    even after your extra clarification. And partly because I don't know your
    current level of education, hence I'm not sure at what level to pitch my answer.
    But I'll keep trying at little longer...

    To be precise, I wrote that the neutrino was indeed postulated as a new
    particle, and then was indeed subsequently detected as technology improved.
    I'm not sure which part of that wasn't clear. Anyway...

    The neutrino can potentially interact with any other fundamental fermion,
    by which I mean it can undergo scattering reactions with those other fermions
    (because all the latter also participate in the weak interaction). One example
    of such interaction is what happens in neutrino detectors. So neutrinos
    can undergo scattering reactions with other particles (for which the probability
    is extremely low because the weak interaction is, well, "weak").
    Theoretically, a neutrino could even scatter off another neutrino, but the
    probability of that is so tiny in the extreme that I doubt anyone will observe
    it in the next thousand years of technological progress.
  14. Jun 6, 2007 #13
    You can consider the Neotrino as photon, it has a double nature, and it's energy is not mc^2 but Pc where P is the moment, and let me ask a question like yours, when gamma photon is emitted from an interaction, what happens to it?

    ofcourse it's going to interact with another thing with eather electromagnetic, weak or somthing else depending on the probability of the interaction... or it's going to damp after loosing it's energy by spreading!!

    and about simplification my previous answer was very simple, i said that neotrino was suggested only to conservate the momentum (spin) and then scientists proofed this 40 years later using high energy and frequency experiments,

    i think you even didn't read my answer...

    finally if you are not convinced then you really need to take too many courses about nuclear physics to really understand how particles born...

    and remember, the new physics is different that the past physics, now they suggest and then discover, in the past they were discovering then explaining,

    hope you understood
  15. Jun 6, 2007 #14
    Sorry I have no education in this at all, except what I have read on wikipedia. Thats why I am having you guys fill in the blanks.

    strangerep: The part that wasnt clear was the last part of that sentence, the part you left out in your last response. "..that somehow carried away excess energy" you say they have since detected it with new technology but was their assumption on its function correct?

    TheDestroyer: I did read your post and I was asking if I understood in this part of my last response "to maintain proper spin a quark farts out a boson which blossoms into an electron and an anti-neutrino" I was using silly words because even though this is all very interesting it seems humorous as well(I'm strange).
  16. Jun 6, 2007 #15


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    Well that is the tricky thing, this is at quite high level physics, so some quantum mechanical background is appropiative.

    The neutrino fullfilled the assumptions that it carries away energy from beta-decay and spin.

    My tips for you is the book:

    it is also cheap =)
  17. Jun 7, 2007 #16
    Nuclear physics is a very complicated subject, because until now 90% of it is practical, and no one succeeded in finding the real look of the nucleus, that's why people is assuming some models for the nucleus and then explaining why this model is correct,

    Add to this Quantum mechanics hasn't interfere well in nuclear physics and also quantum mechanics has it own problems

    That's why too many things are not explained very well...

    I'm not convinced about too many things I studied In nuclear physics, but everything is proofed, that's why no one can say no until he either get a better theorems or proof that previous is wrong...

  18. Jun 7, 2007 #17
    Thanks to all ^_^
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