Spin

[Mike Smith Cosmos]

Electrons can have angular momentum from orbiting the nucleus, which creates a magnetic field. That is indeed a physical phenomenon. The only non-physical spin is the electron's intrinsic spin angular momentum.

 

Atoms are also allowed to spin and vibrate.

 

I have just read an article that ( BoB for short ) flagged up on Spin right at the early days of this Spin thread. It does provide a good analogue picture of SPIN of the electron

 

This is from a paper

 

Hans C Oharian Rensselaer Polytechnic Institute Troy new york 12180

 

received feb 5 1984

 

Abstract : According to the prevailing beleif , the spin of the electron or of some other particle is a mysterious internal angular momentum for which no concrete physical picture is available, and for which there is no classical analogue. However , on the basis of an old calculation by Belinfante (Physica 6, 887 (1939) ) , it can be shown that the spin may be regarded as an angular momentum generated by a circulating flow of energy in the wave field of the electron. Likewise, the magnetic moment may be regarded as generated by a circulating flow of charge in the wave field. This provides an intuitavely appealing picture and establishes that neither the spin nor the magnetic moment are " internal " they are not associated with the internal structure of the electron , but rather with the structure of the wave field. Furthermore a comparison between calculations of the angular momentum in the Dirac and electromagnetic fields shows that the spin of the electron is entirely analogous to the angular momentum carried by a classical circularly polarized wave.

 

You may have read this previously. unfortunately I was caught up over Xmas with Relatives , Flue, Snow , New house etc and missed the early discussion

Edited March 4, 2011 by Mike Smith Cosmos

[swansont]

Yes, well I'm not sure about all that you say, but you did mention previously about the tremendous forces present in collapsed stars which are held up by the very exclusion principle electrons not accepting to be identical in the same energy band. If this force is so great to operate under those vast conditions the exclusion principle must itself be quite something just between two electrons , being asked to occupy the same energy level with identicle quantum numbers ( which of course they refuse to do. )

 

So I am still trying to find out off someone What quite is it? ( other than the maths ) that is preventing the two identical electrons ( same quantum numbers ) from occupying the same energy level. I know the Pauli exclusion principle says so ( but a principle itself has no Force , it must work through something ! )

 

Is it the repulsive charge E1E2/r squared where r is so infinitessimally small that the electrostatic repulsion becomes infinite .

 

[ This is not put forward as fact , just a question ]

 

 

Having identical states is called degeneracy, so it's called degeneracy pressure. It's not classical and it works with uncharged Fermions as well (neutrons, neutrinos)

[Mike Smith Cosmos]

Having identical states is called degeneracy, so it's called degeneracy pressure. It's not classical and it works with uncharged Fermions as well (neutrons, neutrinos)

 

Thank You ! With all the comments and the paper from 1985 which 'Bob For Short' put forward last Nov 2010 that I missed, I am beginning to formulate a pictorial model. That is important for me personally. I can now cloth the model with maths and further ideas. If the more recent discoveries need for the pictorial model to be changed or updated , that's fine. I find it very difficult to go straight into pure maths, with no framework. I have spoken to mathematicians and some prefer to have no picture but ride the maths. ( not me I find it almost impossible ).

 

Unfortunately your comments pose further questions. Classed as degeneracy who wins, or is it stale mate. Do the electrons allow themselves to become degenerate or part degenerate or just attempted degeneracy.

 

If one free electron was approaching a hydrogen nucleus namely a single proton , some 300,000 years after the big bang, would its intrinsic spin orientation be in a random direction, and on falling into the lowest energy state orientate the electron intrinsic spin in a particular orientation. eg would it align with any magnetic moment from the proton.

 

Later after this particular atom gets into the situation that a second proton ( plus a couple of neutrons through the rather torturous process of tunneling , deuterium, tritium,neutron decay etc ) will an approaching 2ND free electron orientate its spin to be the opposite to the previous electron spin ( say one spin up the other spin down ) an so enter the lowest energy state with the previous electron . Or does it need one plank bar X 1/2 worth of energy to flip its orientation. Sorry !

Edited March 4, 2011 by Mike Smith Cosmos

[swansont]

Thank You ! With all the comments and the paper from 1985 which 'Bob For Short' put forward last Nov 2010 that I missed, I am beginning to formulate a pictorial model. That is important for me personally. I can now cloth the model with maths and further ideas. If the more recent discoveries need for the pictorial model to be changed or updated , that's fine. I find it very difficult to go straight into pure maths, with no framework. I have spoken to mathematicians and some prefer to have no picture but ride the maths. ( not me I find it almost impossible ).

 

Unfortunately your comments pose further questions. Classed as degeneracy who wins, or is it stale mate. Do the electrons allow themselves to become degenerate or part degenerate or just attempted degeneracy.

 

Obercoming the degeneracy requires a certain amount of energy; this is why there is a limit to how much mass a star can have before it collapses into a neutron star — that's the point where the electron degeneracy is overcome. It can be calculated, though I don't recall the salient details.

 

If one free electron was approaching a hydrogen nucleus namely a single proton , some 300,000 years after the big bang, would its intrinsic spin orientation be in a random direction, and on falling into the lowest energy state orientate the electron intrinsic spin in a particular orientation. eg would it align with any magnetic moment from the proton.

 

It would align in a particular way relative to the spin of the nucleus.

 

Later after this particular atom gets into the situation that a second proton ( plus a couple of neutrons through the rather torturous process of tunneling , deuterium, tritium,neutron decay etc ) will an approaching 2ND free electron orientate its spin to be the opposite to the previous electron spin ( say one spin up the other spin down ) an so enter the lowest energy state with the previous electron . Or does it need one plank bar X 1/2 worth of energy to flip its orientation. Sorry !

 

The energy difference in the orientations depend on the magnetic field. Without a field the orientations have the same energy.

 

If the spins didn't weren't opposite, then the electrons would cancel out each others existence.

 

???

[Mike Smith Cosmos]

 

 

 

The energy difference in the orientations depend on the magnetic field. Without a field the orientations have the same energy.

 

Thank you for that little lot of answers. Very helpful. You should write a book .

 

Have you any comments on the 1985 paper on spin four posts back (today by me my 3:26 , provided by Bob for short last November) ?

Edited March 4, 2011 by Mike Smith Cosmos

[Schrödinger's hat]

I'm grasping at a way of explaining spin to myself, but I don't know the maths well enough to confirm or form this idea properly.

I'll try to formulate a couple of questions that may help, maybe someone can answer.

 

How does spin transform under Lorentz boost? I've seen it written as a vector or one form, but this is confusing to me, is there also a way to formulate it as a 2-form? Either way, how does it tranform?

A lot of things that can be written as a vector in 3d are bivectors in 4d, so this set me thinking.

 

Does a relativistic angular momentum 2-form of a spin-free object have magnitude? ie is its scalar product with itself 0?

[swansont]

Thank you for that little lot of answers. Very helpful. You should write a book .

 

Have you any comments on the 1985 paper on spin four posts back (today by me my 3:26 , provided by Bob for short last November) ?

 

I don't see how the concept of a circulating charge jibes with the experimental determination of electron size. Those results seem to imply that the electron's charge is localized.

[steevey]

It's not my belief.

 

Take the electron charge and the experimentally determined size limit of the electron. Calculate how fast it would need to spin in order to generate the magnetic moment. Compare with c.

 

 

In that case though, wouldn't an electron have to have a magnitude and a direction? And the "angular momentum" is just the pattern of the electron's most probable place. We don't actually know that the electron is or isn't moving in a spherical way (or etc), but with spin, I don't see how there can't be some physical movement to generate a magnetic field.

 

Also, if spin truly isn't physical, why is it that when two electrons are forced to occupy the same physical orbit or distance from the nucleus, that their spins are forced to be come opposite? Because then the opposite spin would be the result of a physical force, and if a physical force is effecting it, I don't see how it isn't physical. Even virtual particles are physical for a short amount of time.

Edited March 5, 2011 by steevey

[Mike Smith Cosmos]

I don't see how the concept of a circulating charge jibes with the experimental determination of electron size. Those results seem to imply that the electron's charge is localized.

 

I will have to think on that one!

 

I am just wading my way through the ISING Model.

 

Has a distinct " homing in " feeling about it. . Degenerate pressure, magnetic moments, circulating charge in a magnetic field, and circulating magnetism in an electric field. I need to read on , think and digest.

Edited March 5, 2011 by Mike Smith Cosmos

[swansont]

In that case though, wouldn't an electron have to have a magnitude and a direction? And the "angular momentum" is just the pattern of the electron's most probable place. We don't actually know that the electron is or isn't moving in a spherical way (or etc), but with spin, I don't see how there can't be some physical movement to generate a magnetic field.

 

Which doesn't matter. Argument from personal incredulity isn't a valid argument.

 

Also, if spin truly isn't physical, why is it that when two electrons are forced to occupy the same physical orbit or distance from the nucleus, that their spins are forced to be come opposite? Because then the opposite spin would be the result of a physical force, and if a physical force is effecting it, I don't see how it isn't physical. Even virtual particles are physical for a short amount of time.

 

This is not true. Orbitals are not well-defined trajectories, so you can't say they are occupying the same physical orbit.

[steevey]

Which doesn't matter. Argument from personal incredulity isn't a valid argument.

So just because I point something out its automatically invalid? That seems sort of, uh...ludicrous.

 

Anyway, a magnetic field is a moving electrical field, which means the electron has to be causing the motion of the electrical field in some way.

 

 

This is not true. Orbitals are not well-defined trajectories, so you can't say they are occupying the same physical orbit.

 

Electrons take up physical space, that's why when you have a bunch of them, you can see a physical 3D object. Its like saying paper is only 2D, yet if I stack them, I make a 3D object because they are actually 3D. And since as an undefined wave state the electron occupies the entire orbital, then the physical space being taken up by the electron is the entire orbital.

Edited March 5, 2011 by steevey

[Cap'n Refsmmat]

So just because I point something out its automatically invalid? That seems sort of, uh...ludicrous.

No, that's not what swansont said. Just because you don't understand how something could work does not mean it cannot work. Just because you can't see how there's no physical motion does not mean it's impossible.

 

Electrons take up physical space, that's why when you have a bunch of them, you can see a physical 3D object. Its like saying paper is only 2D, yet if I stack them, I make a 3D object. And since as an undefined wave state the electron occupies the entire orbital, then the physical space being taken up by the electron is the entire orbital.

That won't work, because orbitals overlap. You'd end up proving that atoms can't have more than one or two electrons at all.

 

In any case, you can have two electrons in the same orbital, so long as they have opposite spins.

[steevey]

That won't work, because orbitals overlap. You'd end up proving that atoms can't have more than one or two electrons at all.

 

In any case, you can have two electrons in the same orbital, so long as they have opposite spins.

 

 

Well, according to the definition of a magnetic field, there has to be a specific motion that makes the electrical field rotate in the specific oriented way that it does.

 

 

No, that's not what swansont said. Just because you don't understand how something could work does not mean it cannot work. Just because you can't see how there's no physical motion does not mean it's impossible.

 

 

That's exactly what he seems to be doing though. Its as if he can't accept the possibility it might be a real physical thing thats going on just because I'm stating that possibility. I already know it might not be physical, but I also know that it could too be physical.

Edited March 5, 2011 by steevey

[Cap'n Refsmmat]

Well, according to the definition of a magnetic field, there has to be a specific motion that makes the electrical field rotate in the specific oriented way that it does.

...in classical physics.

 

That's exactly what he seems to be doing though. Its as if he can't accept the possibility it might be a real physical thing thats going on just because I'm stating that possibility. I already know it might not be physical, but I also know that it could too be physical.

There is no physical way for an electron to spin fast enough to generate the requisite magnetic field. It's that simple. Quantum physics doesn't involve spinning electrons, and it does not need spinning electrons.

 

Physical explanations of spin also cannot account for its quantization -- there are only two possible spin states for electrons. They also cannot account for protons and electrons having the same spin, despite protons being composed of three independent particles which each have their own spin. And so on.

 

Simply put: Physics has no need of a physical explanation of spin.

[steevey]

...in classical physics.

 

 

There is no physical way for an electron to spin fast enough to generate the requisite magnetic field. It's that simple. Quantum physics doesn't involve spinning electrons, and it does not need spinning electrons.

 

Physical explanations of spin also cannot account for its quantization -- there are only two possible spin states for electrons. They also cannot account for protons and electrons having the same spin, despite protons being composed of three independent particles which each have their own spin. And so on.

 

Simply put: Physics has no need of a physical explanation of spin.

 

Then what's moving the electrical field? If angular momentum isn't even a physical thing, why would that move it?

 

Also, can't quantinization be explained by destructive interference in the waves? If an electron could posses any energy or any spin or any etc, then the waves would be too destructive to be coherent or form really any matter. So quantinization is the result of only the possible non destructive waves existing. So if electrons with only whole integer energies can exist without producing destructive wave interference, then those are the only ways they will exist.

Edited March 5, 2011 by steevey

[Cap'n Refsmmat]

Also, can't quantinization be explained by destructive interference in the waves? If an electron could posses any energy or any spin or any etc, then the waves would be too destructive to be coherent or form really any matter. So quantinization is the result of only the possible non destructive waves existing. So if electrons with only whole integer energies can exist without producing destructive wave interference, then those are the only ways they will exist.

In what waves? In the electron's wavefunction? I don't know that spin appears in the wavefunction at all; I don't know enough about the subject to be certain, though.

 

Other forms of quantization can be expressed in terms of the boundary conditions imposing limitations on the waves as you described, but they usually allow for harmonics and higher-energy modes. (For example, a wave on a string is limited to certain frequencies, but it can also be any integer multiple of those frequencies.) Spin does not exhibit this behavior.

[steevey]

In what waves? In the electron's wavefunction? I don't know that spin appears in the wavefunction at all; I don't know enough about the subject to be certain, though.

 

Other forms of quantization can be expressed in terms of the boundary conditions imposing limitations on the waves as you described, but they usually allow for harmonics and higher-energy modes. (For example, a wave on a string is limited to certain frequencies, but it can also be any integer multiple of those frequencies.) Spin does not exhibit this behavior.

 

Spin doesn't appear in Schrödinger's equation, but spin is used to describe physical effects of the properties as a wave. So how does spin have a physical effect if it isn't a physical thing? It's how the magnetic field is oriented isn't it? And by the way I've seen it, I haven't seen the electron itself spinning, only the magnetic field in a certain direction, but how is the magnetic field rotating then if the electron isn't?

 

 

Spin is quantized though, which means there's a reason particles don't posses just any and all spins, which I'm guessing has something to do with wave interference, but if that isn't true for spin which I don't know if it is, its still true for an electron's energy or angular momentum. An electron cannot posses any and all possible energies because not every value of energy allows a non destructive wave.

 

Physical explanations of spin also cannot account for its quantization -- there are only two possible spin states for electrons. They also cannot account for protons and electrons having the same spin, despite protons being composed of three independent particles which each have their own spin. And so on.

A proton is made up of three quarks which can only have only two possible spin states. So, two quarks will have opposite spins which will cancel out, then what's left over is an extra up quark which could account as a sort of net spin.

 

 

 

 

Edited March 5, 2011 by steevey

[swansont]

Spin doesn't appear in Schrödinger's equation, but spin is used to describe physical effects of the properties as a wave. So how does spin have a physical effect if it isn't a physical thing?

 

As I've mentioned to Lemur, one has to be careful about what one considers "real" or "a physical thing" in physics. Physics describes how things behave, not what they are. But that's for another thread.

[steevey]

As I've mentioned to Lemur, one has to be careful about what one considers "real" or "a physical thing" in physics. Physics describes how things behave, not what they are. But that's for another thread.

 

Ok, physics describes how things behave, so now that we've gotten that out of the way, tell me what spin is physically like. Or, How exactly could a magnetic field of an electron rotate but not the electron itself? Or can we not answer it with our current knowledge because we don't know exactly what comprises a magnetic field?

 

Also, can't physics describe what things are made of too? Through physics and testing of experiments and observation, we determined what an atom is, or is that just science in general?

Edited March 5, 2011 by steevey

[swansont]

Ok, physics describes how things behave, so now that we've gotten that out of the way, tell me what spin is physically like.

 

 

Seriously? I tell you physics doesn't do that, so you ask anyway?

[Cap'n Refsmmat]

Ok, physics describes how things behave, so now that we've gotten that out of the way, tell me what spin is physically like.

There is no physical way to answer that question, because it is impossible to see the motion and behavior of a single wave-particle at all times. You can only guess.

 

Or, How exactly could a magnetic field of an electron rotate but not the electron itself?

Because it has spin.

 

Also, can't physics describe what things are made of too? Through physics and testing of experiments and observation, we determined what an atom is, or is that just science in general?

Physics can tell you that the electromagnetic force exists, but can't tell you how it works. I mean, mustn't there be some physical thing pushing on the particles?

 

Physics can tell you how gravity behaves, but it can't tell you why gravity chose to behave that way instead of any other way.

 

And so on.

 

However, gnome physics may be able to explain spin:

 

http://blogs.scienceforums.net/capn/2011/02/28/gnome-physics/

[steevey]

Seriously? I tell you physics doesn't do that, so you ask anyway?

 

Yeah, how would spin physically behave, but refsmmat has already said we can't answer it anyway, so you don't need to respond.

[lemur]

Physics can tell you that the electromagnetic force exists, but can't tell you how it works. I mean, mustn't there be some physical thing pushing on the particles?

My impression of the modeling is that electron interactions are somewhat predictable insofar as their force characteristics are known, but their interactions are highly unpredictable so they can only really be understood concretely where numerous particles are exhibiting average behavior. Still, ON AVERAGE, don't they push against each other purely due to force-repelling-force? As far as the basis for that force, does anyone bother to make claims as to whether force is fundamental or has antecedent causes?

[Cap'n Refsmmat]

My impression of the modeling is that electron interactions are somewhat predictable insofar as their force characteristics are known, but their interactions are highly unpredictable so they can only really be understood concretely where numerous particles are exhibiting average behavior. Still, ON AVERAGE, don't they push against each other purely due to force-repelling-force? As far as the basis for that force, does anyone bother to make claims as to whether force is fundamental or has antecedent causes?

The question of whether it has antecedent causes is exactly what I mean is not physics. Sure, they repel due to the electromagnetic force, but how does that actually work?

[lemur]

The question of whether it has antecedent causes is exactly what I mean is not physics. Sure, they repel due to the electromagnetic force, but how does that actually work?

I rarely think about protons as being more than sources of mass/gravity and positive electrostatic charge, but I saw something today that made sure to highlight their transparency as consisting of different-directional quarks. I bet that before protons were known to consist of quarks, a physicist like you would have said that the question of whether protons consist of sub-particles or other constituent mechanics is not physics. It's ALL "potential physics." However, there's no way of knowing whether professional physicists will actually choose one direction or another.

 

Personally, I think it's interesting when some issue is not formal physics (yet) because it allows anyone with tacit knowledge to contemplate how physics would or could approach the problem. I suppose that would be a "speculations" issue, but I still think it is potential physics research. The easy question I was trying to pose with regard to this, however, is simply whether physics is leaning toward establishing primacy for either force or energy. I mean, you could either try to dissect forces for energy-relations that constitute them OR consider force-fields as fundamental entities that express energy but are themselves neither energy nor reducible to it. This sort of gets back to the ever-resurfacing conflict between nouns and verbs, though, I think. I.e. between objects and motion.