Structure of matter

Discussion in 'Physics & Math' started by ismu, Mar 4, 2002.

  1. ismu ::phenomenon::. Registered Senior Member

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    I've visited this site couple weeks ago:

    http://www.nobel.se/physics/educational/matter/1.html

    This remind me the history about old theories of matter. Ancient theory told that any matter can be splitted continously until Alchemist made periodic table. Then we belive that proton, neutron and electron is the fundamental element composing matters. And now, the most fundametal element we can 'found' are quarks. I have some thought bothering my mind;

    - So... we haven't actually 'know' the most fundamental element, yet?
    ...And quarks is just a 'physical/math modelling' to manipulate matter?

    - Quarks still have several different properties.
    I think the most fundamental elements should have identical properties. Or at least a pair of elements, as all philosophy of almost anything in the universe; there are pairs: good and bad, plus and minus, one and zero, male and female, etc...

    - Is there any other (newer) method to analyse matter?
    ...Instead of collide them (or shooting) with other matter?

    - WHY they're spinning? Is the spin itself a fundmental property we have to 'accept without further question'?
    Vortex streams show that matters have tends to spin. Galaxies, stars, planets, moons, atoms are spinning. Electro-magnetic, 'spin' electric current (electrons) to create magnetic fields.

    My basic is engineering, not physics. Please, clear me up?
     
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  3. Bambi itinerant smartass Registered Senior Member

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    ismu,

    I've always been confused with the Standard Model, and looked for accessible resources to understand it. Your link has finally fulfilled my need.

    Thank you very much, it's an awesome site!

    As for your questions, I don't have the answers but maybe it's some consolation that I keep wondering along the very same lines.

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  5. ismu ::phenomenon::. Registered Senior Member

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    more

    You're welcome. So let's wait someone knew better than us here

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    This questions also comes to me:

    - Can we measure speed of electrons orbit? Is proton and neutron spinning? Is quark spinning?

    - Is it true that magnetism formed from orbiting electrons? If it so, can we measure speed of electrons orbit by it's magnetism?
     
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  7. Xelios We're setting you adrift idiot Registered Senior Member

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    - Is there any other (newer) method to analyse matter?
    ...Instead of collide them (or shooting) with other matter?


    I don't believe so. If we could analyze matter not using other matter in the process we could then we could break the Uncertainty Principle and measure both speed and direction to a very high accuracy. The problem with finding an alternate method of analyzing matter (that is, alternate to bouncing other matter off of it) is that whatever we use it must interact with the particle we're attempting to measure. That leaves us with very few, if not only one option, which is what we're using now.

    So... we haven't actually 'know' the most fundamental element, yet?

    Right. There are a few theories out there, the most credible one so far is called String Theory (or M-Theory). It theorizes that all matter (including quarks I believe) is made up of tiny vibrating strings. The way the string vibrates determines the type of "particle" it is. However, string theory requires at least 10 spacial dimensions in it's simplified form and 26 in it's original form. The existance of these strings can never be fully tested with the methods we're using now (particle accelerators) as we would need so much energy that a particle accelerator the size of the galaxy, or even the universe would be required.

    WHY they're spinning? Is the spin itself a fundmental property we have to 'accept without further question'?


    I'm not quite sure, but I do know they aren't actually spinning. Spin is more of a mathematical value assigned to each particle (not sure why) and not an actual angular spin. For example, an electron is actually a point charge which means it supposedly has a radius of zero. Thus, it cannot be spinning. However, we give it a spin value of 1/2, partly because of Pauli's Exclusion Principle that states that no two electrons in the same orbital can have the same spins. So in the case of helium, in the first orbital one electron would have spin 1/2, the other would have spin -1/2.

    Anyway, I'm only 17 so some of this stuff might not be completely right =P

    If you don't mind waiting a couple weeks you can get a professional answer to your questions at www.madsci.org. I've had many questions answered there and I have to say it's probably one of the most informative sites out there.
     
  8. James R Just this guy, you know? Staff Member

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    Hi ismu,

    <i>So... we haven't actually 'know' the most fundamental element, yet?</i>

    At this stage, the best thing we have is the Standard Model of Particle Physics, which has at its base 6 different types of quarks, 3 different types of electrons, 3 different types of neutrinos, plus a few particles (such as the photon) which carry the fundamental forces between all particles. These particles each have anti-particles, and they all combine to form hundreds of more complex particles, the most familiar being the proton and neutron.

    Many physicists suspect that the Standard Model is too complex to be the real story. It is possible that quarks, electrons and so on are different manifestations of something more fundamental. However, at this stage nobody has been able to see any finer structure in an electron (to take one example). To all intents and purposes, it acts like a point particle with no size. Theories such as string theory and M-theory postulate new models of particles, but they are very difficult to test.

    <i>And quarks is just a 'physical/math modelling' to manipulate matter?</i>

    That is more of a philosophical question than a physics question. Whether entities like quarks are real or are just a convenient model for things we can't directly perceive isn't really the concern of science. What is important is that the model allows us to predict things about the structure of matter.

    <i>Is there any other (newer) method to analyse matter? ...Instead of collide them (or shooting) with other matter?</i>

    Not really. To probe matter at smaller and smaller scales requires increasing amounts of energy. The best way we have found to put that energy into a small enough space is to use particle accelerators.

    <i>WHY they're spinning? Is the spin itself a fundmental property we have to 'accept without further question'?</i>

    In quantum mechanics, spin is one of many quantum numbers which particles possess. It is called spin because in some ways it behaves similarly to the spin of macroscopic objects we are familiar with. However, when we say an electron (for example) has spin, we don't really mean that it is like a little ball literally spinning in space. The term spin is one which allows us to distinguish a certain quantum mechanical property which an electron has from, say, the same property that a photon has.

    <i>Can we measure speed of electrons orbit? Is proton and neutron spinning? Is quark spinning?</i>

    Electrons in atoms do not really orbit. At the quantum mechanical level, the uncertainty in the position and velocity of an electron means that the best we can say is that electrons occupy certain regions of space around a nucleus, but they do not move like planets orbiting the sun.

    Protons and neutrons both have intrinsic quantum mechanical spin. In fact, protons, neutrons and electrons all have the same value of spin. They belong to a class of particles known as <i>fermions</i>.

    <i>Is it true that magnetism formed from orbiting electrons? If it so, can we measure speed of electrons orbit by it's magnetism?</i>

    As I said, the speed of an electron is a somewhat ill-defined concept at the quantum level. It is true that magnetism is associated with spin and orbital effects, both from the electrons and the nucleus of an atom. For example, both protons and neutrons have an intrinsic magnetism - i.e. they act like little bar magnets.
     
  9. Bambi itinerant smartass Registered Senior Member

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    James,

    Is it fair to say that spin is an electromagnetic property? If not, in what other ways (aside from magnetism) does spin manifest itself?

    tia
     
  10. James R Just this guy, you know? Staff Member

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    I wouldn't call spin an electromagnetic property.

    Apart from magnetism, it manifests itself in a fundamental way in determining atomic structure, and in the way that groups of particles behave.

    All particles can be divided into two broad groups called <i>fermions</i> and <i>bosons</i>. Bosons have integral spin (e.g. 0,1,2,3 etc.), while fermions have half-integral spin (e.g. 1/2, 3/2, 5/2 etc.).

    The Pauli exclusion principle applies only to fermions. It states that no two fermions can be in the same quantum state at the same time. The principle, when applied to electrons (which are fermions) in atoms, determines the atomic structure and hence the chemical behaviour of each atom. This has nothing to do with electromagnetism, but is fundamentally to do with spin.

    At an even more fundamental level, whether a particle is a fermion or a boson restricts certain symmetries of the quantum wavefunction for the particle.
     
  11. Bambi itinerant smartass Registered Senior Member

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    James,

    I'm afraid electrons (or any charged particle) aren't very good examples when trying to decouple spin from electromagnetism. So these examples aren't very helpful, at least not for me.

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    As far as I understand so far, the fractional vs. whole spin numbers are derived from particle decay and conservation of momentum. So even if spin had basis exclusively in electromagnetism it wouldn't be apparent from such experiments. Ditto for exclusion principle and electron shells, since we are again dealing with electromagnetism. And actually, for exclusion principle it even makes sense: try and put two permanent magnets alongside each other in the same orientation -- they'll naturally tend to flip the other way (so could it be the same thing with electrons and their spin numbers?)

    The wave function symmetries you mentioned sound intriguing.

    But I just find it weird that a quantum number would manifest itself in terms of electromagnetic field and yet not be associated with it. Does spin cause effects similar to magnetism in the weak or strong fields? Also, I haven't heard of it affecting gravity either (although there's some sort of half-secret antigrav research with superconductors that I keep hearing about every now and then.)
     
  12. James R Just this guy, you know? Staff Member

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    <i>But I just find it weird that a quantum number would manifest itself in terms of electromagnetic field and yet not be associated with it.</i>

    It <i>is</i> associated with it. Electrons and protons are charged particles. Neutrons are made up of charged quarks. The intrinsic spins of those particles, combined with the charge (which is another quantum number), results in the magnetic properties of the particles. However, spin is more a general concept than just an electromagnetic property. Carrier particles of the strong, weak and (probably) gravitational forces all have spin. Some have charge too; others do not.

    The graviton has not been detected yet, but it is predicted to have spin 2 and no charge. The spin affects the propagation modes of gravitational waves and the ways in which they can be generated.
     
  13. ismu ::phenomenon::. Registered Senior Member

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    The magnetic vortex theory.

    James,

    Thanks for your explanation about matter. But when it come into magnetism, i can't get clear picture to imagine how the magnetic field formed in matter. My picture was, that magnetism (in permanent magnet) formed because there are electrons orbits. And they work similar with superconductor selenoid, in molecular sizes.

    So... how we suppose to imagine the magnetism in permanent magnet?

    I've also visited this site. Here Christopher J. Arnold describe the magnetic vortex theory.
    What do you think; is this can be used as reference to picture magnetism in permanent magnet, or is it an unproven/invalid theory?

    Any other suggestion?
     
  14. James R Just this guy, you know? Staff Member

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    ismu,

    The simplest way to picture magnetism in matter is to think of individual atoms as little bar magnets. Each atom contributes a little bit of magnetic field, and the fields of atoms can add to each other to make a big magnet.

    The vortex theory does not seem particularly helpful to me, though I have not examined it in detail. One flaw I noticed almost immediately is that the theory ignores the fact that magnetic field lines always form closed loops. This also implies that there are no magnetic monopoles.
     
  15. ismu ::phenomenon::. Registered Senior Member

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    James R

    Yes, it was a classic theory of magnetism.
    But, this way i still can't clearly figure:
    - Corelation between permanent magnet (in atomic scale) and electromagnetics.
    - What should happen with material structure in magnetizing material, both by elctromagnetic and rub a material with permanent magnet

    But magnetic field lines itself doesn't really exists isn't it? And the poles itself only a 'sign' to show the differences about direction of those fields.
    How if we see magnetic field as a kin of radiation? (wich still have 'direction' property).

    Kansas State University also have theory about magnetic vortex. And it seems there are obvious corelation between electrons spin with magnetism.
    What do you think?
     
  16. James R Just this guy, you know? Staff Member

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    Re: James R

    ismu,

    <i>But magnetic field lines itself doesn't really exists isn't it? And the poles itself only a 'sign' to show the differences about direction of those fields.</i>

    Well, that's a difficult question. Magnetic field lines are a useful concept in explaining many phenomena associated with electromagnetism; so are electric field lines. But on the page you linked above, the authors clearly accept that field lines exist, whilst at the same time ignoring the fact that they must form closed loops.

    Your link to Kansas State University refers to magnetic vortices which are much different to the ones in the article you linked before. From my reading, I would say KSU is doing real science, whilst the person or people in your first link have some non-standard ideas which I suspect, at first glance, are incorrect, or at least do not take us anywhere useful.

    Yes, I agree there is a link between magnetism and spin, which I have tried to explain partly in earlier posts.
     
  17. ismu ::phenomenon::. Registered Senior Member

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    Spin... Orbit...

    Ok James,

    Here where i baffled to drag a conclusion, You've mentioned that:

    Electrons in atoms do not really orbit.
    So... they're only moving around in limited space according to its energy, right?

    - Spin is more of a mathematical value assigned to each particle (not sure why) and not an actual angular spin.

    - I wouldn't call spin an electromagnetic property.... However, spin is more a general concept than just an electromagnetic property...

    - Electrons and protons are charged particles. Neutrons are made up of charged quarks.

    How should i figure this:
    - What should happen with material structure (in atomic scale) while magnetized, by elctromagnetic or rub a material with permanent magnet?

    Btw, what is spin-wave mentioned by KSU?
     
  18. Xelios We're setting you adrift idiot Registered Senior Member

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    Electrons in atoms do not really orbit.
    So... they're only moving around in limited space according to its energy, right?


    I think he's referring to the fact that electrons set themselves up in shells around the nucleus. We call these orbitals, but that's probably not the best word for them. Basically, an electon doesn't orbit a nucleus because it can appear at any point in its shell at random. It's not orbiting like the moon orbits earth, it's more like they're floating around the nucleus appearing in random spots at set "heights" from the nucleus. (ie. in the first orbital an electron, characterized 1s1, will randomly move around the nucleus but will always remain approximatly the same distance away from it.)

    It's a technicality, but an important one. Most people are happy saying electrons orbit the nucleus, they're just not quite right

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  19. ismu ::phenomenon::. Registered Senior Member

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    Ok Xelios.

    We know that electric current (means flow of electrons, moving electrons) disperse magnetic flux. If their move random, How's permanent magnetic formed?
    If i'm not mistaken, stronger magnetic occure on elements which have more odd number of electrons. How's that? (Or am I mistaken? :bugeye: )
     
  20. ismu ::phenomenon::. Registered Senior Member

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    More...

    I got more thought after reading IBM research on magnetization decay.

    James,

    ...and how should we figure about magnetization decay by thermal energy and/or by kinetic energy?
    (Using magnetic votex theory --wich you said wrong-- I can 'imagine' there are some disturbance on it's vortices)
     
    Last edited: Mar 6, 2002
  21. James R Just this guy, you know? Staff Member

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    ismu,

    The process of creating a bulk magnet, such as a common bar magnet involves aligning the spins of the atoms in the magnet so that they point in a particular direction. In an unmagnetised piece of iron, for example, the spins of various atoms all point in random directions (although in iron there are actually groups of aligned atoms, which are called "domains"). When the piece of iron is magnetised, the spins of all the atoms line up in the same direction, meaning that the magnetic fields of all the atoms add together to create one overall field for the bar magnet.

    A spin wave, as I understand it, is a wave in which the spins of atoms or particles flip over and back again as a wave passes. It has nothing to do with bulk magnetisation.
     
  22. Xelios We're setting you adrift idiot Registered Senior Member

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    Just curious James, when a piece of iron is magnetized and all the electrons inside it spin in the same direction, why isn't this violating Pauli's Exclusion Principal? I thought you could not have two electrons in, say, the first energy level with the same direction of spin?
     
  23. James R Just this guy, you know? Staff Member

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    Xelios,

    It's a little more complicated than I've outlined above. In iron, there is a quantum effect called <i>exchange coupling</i> between electrons which makes iron ferromagnetic. Also, it's not the electrons in the atoms which all align; it is the individual atoms which line up with each other, so that their overall spin (including electron and nuclear spin) points in the same direction. Electrons in different atoms still obey the Pauli principle.
     

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