1. Joined
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    31 Dec '19 03:48
    Goudsmit and Uhlenbeck discovered not only that electrons were orthorotating, but also that they were spinning at 1.37 times the speed of light. Or did they?

    Do electrons spin faster than the speed of light?
  2. Standard memberDeepThought
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    31 Dec '19 10:00
    @metal-brain said
    Goudsmit and Uhlenbeck discovered not only that electrons were orthorotating, but also that they were spinning at 1.37 times the speed of light. Or did they?

    Do electrons spin faster than the speed of light?
    What does the word ortho-rotating mean?

    Spin is one of the harder concepts in physics. Orbital angular momentum is easy enough to understand, it's the same as in classical physics, one multiplies the instantaneous linear momentum by the distance to the axis and it's a conserved quantity. In classical physics spin is the same concept as orbital angular momentum, for a rigid body we can just sum the angular momenta of each atom. For a point-like particle the best we can do is try to take a limit. The angular momentum of a ball is the moment of inertia times the angular velocity, which goes as the mass by the radius squared times the angular velocity. So for fixed mass and angular velocity, in the limit that the radius goes to zero the angular momentum goes to zero, so spin does not exist for classical elementary particles.

    In General Relativity the singularity is not point-like. But we do not expect that relative velocities at different points to be constrained by the speed of light.

    In quantum mechanics the situation changes. The particle is point-like and in non-relativistic quantum mechanics spin is treated in an ad hoc fashion. In relativistic theories we're into representations of the Lorentz Group. Very roughly the mathematical structure of the theory throws up a quantity we call spin which is jointly conserved with orbital angular momentum.

    I don't know who Goudsmit and Uhlenbeck are, but I'd guess they're talking about the classical GR picture above and the faster than light statement is relative to an asymptotic observer and is a co-ordinate effect.
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    01 Jan '20 09:07
    @deepthought said
    What does the word ortho-rotating mean?

    Spin is one of the harder concepts in physics. Orbital angular momentum is easy enough to understand, it's the same as in classical physics, one multiplies the instantaneous linear momentum by the distance to the axis and it's a conserved quantity. In classical physics spin is the same concept as orbital angular momentum, for ...[text shortened]... d the faster than light statement is relative to an asymptotic observer and is a co-ordinate effect.
    "I don't know who Goudsmit and Uhlenbeck are"

    Then maybe you should read up on them and find out. You might want to learn what electron spin is before commenting about it. Heck, maybe electron spin doesn't exist. How could one measure such a thing?
  4. Germany
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    01 Jan '20 11:45
    @metal-brain said
    "I don't know who Goudsmit and Uhlenbeck are"

    Then maybe you should read up on them and find out. You might want to learn what electron spin is before commenting about it. Heck, maybe electron spin doesn't exist. How could one measure such a thing?
    Intrinsic electron spin can be measured in numerous ways, the classic example is the Stern-Gerlach experiment.

    https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach_experiment

    Maybe you should have looked that up before commenting on it?
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    01 Jan '20 18:16
    @kazetnagorra said
    Intrinsic electron spin can be measured in numerous ways, the classic example is the Stern-Gerlach experiment.

    https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach_experiment

    Maybe you should have looked that up before commenting on it?
    Do electrons spin faster than the speed of light?
  6. Standard memberDeepThought
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    01 Jan '20 18:34
    @metal-brain said
    "I don't know who Goudsmit and Uhlenbeck are"

    Then maybe you should read up on them and find out. You might want to learn what electron spin is before commenting about it. Heck, maybe electron spin doesn't exist. How could one measure such a thing?
    I described electron spin in some detail in my post. What do you mean by "ortho-rotating" and who are "Goudsmit and Uhlenbeck"? Provide a reference for them, I'm not chasing down references you can provide.
  7. Subscribersonhouse
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    01 Jan '20 18:47
    @Metal-Brain
    I found this:

    http://www.nyu.edu/classes/tuckerman/quant.mech/lectures/lecture_5/node5.html

    It seems all this came from literally near one hundred years ago.
  8. Germany
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    01 Jan '20 19:56
    @deepthought said
    I described electron spin in some detail in my post. What do you mean by "ortho-rotating" and who are "Goudsmit and Uhlenbeck"? Provide a reference for them, I'm not chasing down references you can provide.
    https://en.wikipedia.org/wiki/Samuel_Goudsmit
  9. Germany
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    01 Jan '20 20:01
    @metal-brain said
    Do electrons spin faster than the speed of light?
    You cannot meaningfully assign a velocity to intrinsic spin.
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    02 Jan '20 20:012 edits
    @kazetnagorra said
    You cannot meaningfully assign a velocity to intrinsic spin.
    So the spin of a neutron star has no meaningful velocity? That doesn't make sense. Why all this talk about how neutron stars eject gold and other precious metals. Without high velocity spin of that neutron star after collision how did those rare metals escape the gravity?
    I read that some neutron stars can be bigger than they should just because of high velocity spin. How fast can a neutron star spin? Pretty darn fast!
  11. Subscribersonhouse
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    02 Jan '20 20:412 edits
    @Metal-Brain
    You can't assign a velocity because of the uncertainty principle. You can peg the velocity but at the expense of pegging the location or Vice Versa but not both at the same time. There is only a probability of a velocity and a probability of location.
    An electron has mass so it can't even go at c, only photons can do that, electrons get very close depending how much acceleration voltage you goose it with (there are now silicon chip designs that can do that using IR laser light to accel electrons and they are working on a design that will accelerate electrons to one MILLION volts of accel, which is 0.94c in a silicon chip one inch long.
    Implications for research and cancer therapy.

    https://phys.org/news/2020-01-particle-chip.html.

    The ion implanters I am expert in has max 200,000 volts of acceleration and that using a series of voltage rings totaling about 2 feet long so when the full chip is built, it will shoot electrons 5 times higher voltage in 1/24th the length.
    But ion implanters, by name don't usually accelerate electrons, instead we go for the big three in semiconductor manufacturing, making pure silicon, an good insulator, into a decent conductor, hence, semiconductor and the ion implanter accelerates the big three, either phosphorous, arsenic or boron (all three are electron donors or receptors) as dopants to the silicon. Maybe TMI, I'll stop there. It would be a big jump to take the full one megavolt chip to accept ions though.
    For now we would LOVE to get one MEV of accel in one inch space even if it is only electrons.
    It might mean electron microscopes the size of a hotel room refrig rather than a unit the size of a car as one example.
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    02 Jan '20 20:51
    @metal-brain said
    So the spin of a neutron star has no meaningful velocity?
    1, A neutron star isn't an electron.

    2, He was just referring to spin, not linear motion.

    He didn't imply that a neutron star has "no meaningful velocity".
  13. Joined
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    03 Jan '20 04:53
    @humy said
    1, A neutron star isn't an electron.

    2, He was just referring to spin, not linear motion.

    He didn't imply that a neutron star has "no meaningful velocity".
    "A neutron star isn't an electron."

    Okay captain obvious. Your irrelevancy is noted.

    "He was just referring to spin, not linear motion."

    So was I.
  14. Joined
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    03 Jan '20 04:571 edit
    @sonhouse said
    @Metal-Brain
    You can't assign a velocity because of the uncertainty principle. You can peg the velocity but at the expense of pegging the location or Vice Versa but not both at the same time. There is only a probability of a velocity and a probability of location.
    An electron has mass so it can't even go at c, only photons can do that, electrons get very close depending ...[text shortened]... ron microscopes the size of a hotel room refrig rather than a unit the size of a car as one example.
    "You can't assign a velocity because of the uncertainty principle."

    That makes no sense. You are now saying electrons spin cannot be measured because of something completely unrelated.

    A particle before going into a slit is an interaction between the detector and the particle. The change could be just a result of the interaction required to have the observation. You are making the mistake of ASSUMING an observation doesn't require an interaction for that observation to happen.
  15. Subscribersonhouse
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    03 Jan '20 15:20
    @Metal-Brain
    You have no idea of what you are talking about. You are spouting crap like you think you are some kind of expert Like I said, you are out to prove yourself smarter than the last three hundred years of genius. Good luck with that.
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