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Stopping particle spin

  1. Jul 24, 2005 #1
    is it possible (just in theory) to reduce the spin of a particle to zero?

    take a lepton for example - to reduce complications.

    if it is, what will happen?

  2. jcsd
  3. Jul 24, 2005 #2
    :rofl: :rofl: :rofl: :rofl:

    spin is INTRINSIC angular momentum. You can't change spin at all !! And don't even bother picturing "spin", its nothing at all like normal angular momentum.
    Last edited: Jul 24, 2005
  4. Jul 24, 2005 #3


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    This question is almost a logical contradiction. You might as well ask "Is it possible to reduce blue to 24?"

    The problem comes in due to the word "spin". It has been explained many times on here that this word is only historical in nature to the classical spinning motion. It really has no physical equivalent to that. Once you realize this, then you can see why your question really, even in theory, really can't be answered, at least not in a rational fashion.

  5. Jul 24, 2005 #4
    i know, i read this thing long ago. one qm book says electron dimension is smaller than any physical meaning, and if the physical spin applies, the speed of the circumference will exceed speed of light etc etc. spin is just intrinsic angular momentum, it's the most basic mathematcal concept in qm. i learnt qm. is there for some reason "spin" property can dissapear? that's all i meant. sorry if this question sounds silly.
  6. Jul 24, 2005 #5


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    Spin is a fundamental property, like charge. If you somehow change the charge on the electron, it is not an electron any longer. Likewise with spin.

    Can a particle have zero-spin ? Yes it can.
  7. Jul 24, 2005 #6


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    You can think of it this way: what we call an "electron" has spin 1/2. When you have something interact with it in whatever form you decide, that non-zero angular momentum will have to go somewhere. If it ends up in something of the same mass, you have another electron (or a positron),... otherwise, there's no electron left on the reaction (but still, the total angular momentum of the components went somewhere)... gotta go!
  8. Jul 24, 2005 #7
    no, no and no again

    Scroll down to the 'five socalled easy pieces'-entry

    https://www.physicsforums.com/journal.php?s=&action=view&journalid=13790&perpage=10&page=2 [Broken]

    Last edited by a moderator: May 2, 2017
  9. Aug 6, 2005 #8
    From what I have read, there is no 'spin', but there is energy. So this is my question. If an atom were to reach absolute zero, or some temperature that would make all energy stop. What would happen to the Atom? Would it disappear and cease to exist or what? I need this for a story I am writing and my own curiosity.
    Thanks, NanLou4
  10. Aug 6, 2005 #9
    1) Particles do have spin, but as others have mentioned it is a different concept from the classical concept of spin.

    2) Absolute zero cannot be reached because Heisenberg's uncertainty principle forbids it.

    3) If the uncertainty principle didn't apply (if Planck's constant was zero), and you did manage to reduce the energy of a particle to absolute zero, why would it cease to exist? Fermions don't require energy to exist. If you removed the energy from a boson, however, it would cease to exist, but bosons are particles like photons (light), which don't have mass. The particles that make up atoms are fermions, so an atom would continue to exist even if its energy was drained.
    Last edited: Aug 6, 2005
  11. Aug 7, 2005 #10
    Remove the energy from a boson ? How are you gonna do that ? A boson IS energy.

    Bosons are particles with integer spin that therefore respect the Bose-Einstein statistics. Photons are bosons with spin 1 and zero 'rest'mass. However not all bosons are massless !!! Eg : the massive intermediate vectorbosons that mediate the weak force. Or the pions (ie the lightest meson : a quark-antiquark-pair) that mediate the residual strong force (you know the ancient Yukawa particle)

  12. Aug 7, 2005 #11
    Well, that was the point. As bosons try to escape the event horizon of a black hole, their energy is completely removed, correct? I guess that's along the lines of what I was thinking.

    Ah, my bad. :redface: Thanks for the corrections.
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