swansont Posted February 23, 2011 Posted February 23, 2011 Spin exists — electrons have intrinsic angular momentum. It is not due to physical spinning.
steevey Posted February 23, 2011 Posted February 23, 2011 Spin exists — electrons have intrinsic angular momentum. It is not due to physical spinning. How does it exist in a wave, or if it doesn't, how could it exist in a virtual particle? If I drop a pebble in the water, does the wave it produces have angular momentum of some sort?
swansont Posted February 23, 2011 Posted February 23, 2011 How does it exist in a wave, or if it doesn't, how could it exist in a virtual particle? If I drop a pebble in the water, does the wave it produces have angular momentum of some sort? Yes, waves can have angular momentum, though simply dropping a pebble in probably won't. But by making the comparison, you are trying to ascribe classical behavior to a quantum system. At some level, it is doomed to fail.
Mike Smith Cosmos Posted February 23, 2011 Author Posted February 23, 2011 I have gone some way to reading around the subject in the last three days . One or two things seem to be coming home to me. Angular momentum is a very fundamental thing for the operation of the atom thus elements. The orbital angular momentum is slightly easier to understand and visualize to some extent as demonstrated by the diagram on previous postings. Although even their uncertainty or probability still tempts wonder. Despite their fuzzy clouds one can form a mental picture however approximate or inaccurate these diagrams appear. Then we come to the electron spin itself which is said to have angular momentum of two discrete values up spin and down spin. Here comes the rub! If NOT a simple spinning Top for reasons of maths inconsistencies or problems what is the nearest or nearer approximate model that we can visualize, even if it one to shoot down and move on to a more accurate model. Frank Wilczek in his recent book " the lightness of being" page 114 " in trying to understand complicated concepts or equations its good to have toy models". So is there anyone out there who has a good toy model of :- an electron A) its movement generally , say in orbit , B) its movement in or by itself including the spin bit , C) its reality as a point, charge swirl, wiggling small mass energy or whatever lepton D) its ability or lack of to stand still E) any possible exclusion or coupling with another electron. It seems to have originated way back as a fundamental particle within the plasma or shortly after the inflationary start to the Big Bang. It has been mooted that one needs to penetrate maths to get the full picture. But surely we must cloth maths models with some form of philosophical idea !
lemur Posted February 23, 2011 Posted February 23, 2011 But yes, spin physically exists. Don't think of it as a classically spinning object though, because it isn't. Just know that every electron can take on one of two spin values that are equal in magnitude and opposite. If you truly want to understand spin, you must take on the mathematics that are required for everyone else to understand it. I think his point is what makes it "spin" instead of, for example, "hue" where hue would have exactly two values, "dark" and "light?" The idea of angular momentum has to logically relate to some ability of the thing spinning, right? If an electron "spun" as a result of other electrons moving past it to initiate the spinning, that would literally make sense as spin. If there's no spin-like behaviors between electrons, why does it matter whether you call it "angular momentum" or "magnetic propensity?" Or does it have to be called "spin" to account for the fact that its a moving charge and for that reason generative of a magnetic field? Steevey, I hope I'm not confounding your issue by posting this.
swansont Posted February 23, 2011 Posted February 23, 2011 I think his point is what makes it "spin" instead of, for example, "hue" where hue would have exactly two values, "dark" and "light?" The idea of angular momentum has to logically relate to some ability of the thing spinning, right? If an electron "spun" as a result of other electrons moving past it to initiate the spinning, that would literally make sense as spin. If there's no spin-like behaviors between electrons, why does it matter whether you call it "angular momentum" or "magnetic propensity?" Or does it have to be called "spin" to account for the fact that its a moving charge and for that reason generative of a magnetic field? It's called angular momentum because it's angular momentum. Whether this "logically relates" to ability of something spinning depends on your "logic." This is quantum mechanics. If "logic" means using classical physics as a premise, then the answer is no. The electron spin is inherent and quantized. Its magnitude never changes — all you can do is change the orientation. There are spin behaviors between electrons. Did you read up on the Ising model link ajb provided?
lemur Posted February 24, 2011 Posted February 24, 2011 (edited) It's called angular momentum because it's angular momentum. Whether this "logically relates" to ability of something spinning depends on your "logic." This is quantum mechanics. If "logic" means using classical physics as a premise, then the answer is no. The electron spin is inherent and quantized. Its magnitude never changes — all you can do is change the orientation. There are spin behaviors between electrons. Did you read up on the Ising model link ajb provided? Yes, I saw that electrons tend to orient according to repellant alignments between positive and negative parts (I think this is what that graph meant anyway). But I still don't see why this couldn't just be attributed to polarity without attributing that polarity to angular momentum. If the behavior is totally different from an object rotating/spinning in terms of classical mechanics, why use a word that makes reference and therefore implies analogical relationship? Isn't that misleading? edit: maybe linguists should start studying quantum etymology in which word meanings mysteriously and unpredictably tunnel between source concepts and their target meanings. You could apply the uncertainty principle to etymological references. i.e. you can measure the idea of a word or the concept it describes but not both at the same time. edit2: sorry if this joke about quantum etymology sounds rude. It's not meant that way. It just occurred to me and I found it too amusing to resist posting. I hope it doesn't offend anyone. I am not implying that quantum physics is in some way generally ridiculous, just confusing. Edited February 24, 2011 by lemur
steevey Posted February 24, 2011 Posted February 24, 2011 (edited) It's called angular momentum because it's angular momentum. Whether this "logically relates" to ability of something spinning depends on your "logic." This is quantum mechanics. If "logic" means using classical physics as a premise, then the answer is no. The electron spin is inherent and quantized. Its magnitude never changes — all you can do is change the orientation. There are spin behaviors between electrons. Did you read up on the Ising model link ajb provided? I know spin is quantized, but I'm still not visualizing what it is or what it looks like in quantum mechanics. Are you trying to say that the electron spins in integers, as if it moved in pixels? Even at that point, I still don't see how the electron is a virtual particle and a wave but somehow moves about in a circular motion with angular momentum, unless that's exactly what's going on. What if there's a p orbital or a d orbital? It wouldn't seem to be moving circular, but rather helically or conically. Based on all the research I've done outside here, it would appear that spin is a real circular motion that particles move about with, even if they go in and out of reality. But, is that just for particles in a determined state, or do waves also have angular momentum? Or if it is in a wave, is it more of a relative term for an actual "particle" form? Edited February 24, 2011 by steevey
swansont Posted February 24, 2011 Posted February 24, 2011 I know spin is quantized, but I'm still not visualizing what it is or what it looks like in quantum mechanics. Are you trying to say that the electron spins in integers, as if it moved in pixels? Even at that point, I still don't see how the electron is a virtual particle and a wave but somehow moves about in a circular motion with angular momentum, unless that's exactly what's going on. What if there's a p orbital or a d orbital? It wouldn't seem to be moving circular, but rather helically or conically. Based on all the research I've done outside here, it would appear that spin is a real circular motion that particles move about with, even if they go in and out of reality. But, is that just for particles in a determined state, or do waves also have angular momentum? Or if it is in a wave, is it more of a relative term for an actual "particle" form? The electron in an atom is NOT a virtual particle. I'ver mentioned this before. You cannot assign a trajectory to an electron. That's classical, and this is quantum. Orbitals tell you where you can find the electron, if you were to look for it, now how it moves. Yes, I saw that electrons tend to orient according to repellant alignments between positive and negative parts (I think this is what that graph meant anyway). But I still don't see why this couldn't just be attributed to polarity without attributing that polarity to angular momentum. If the behavior is totally different from an object rotating/spinning in terms of classical mechanics, why use a word that makes reference and therefore implies analogical relationship? Isn't that misleading? edit: maybe linguists should start studying quantum etymology in which word meanings mysteriously and unpredictably tunnel between source concepts and their target meanings. You could apply the uncertainty principle to etymological references. i.e. you can measure the idea of a word or the concept it describes but not both at the same time. edit2: sorry if this joke about quantum etymology sounds rude. It's not meant that way. It just occurred to me and I found it too amusing to resist posting. I hope it doesn't offend anyone. I am not implying that quantum physics is in some way generally ridiculous, just confusing. It's angular momentum. It would be more misleading and confusing to physicists if you called it something else. QM is confusing. That's why physicists study it for a long time. I took undergraduate and graduate semester-long sequences in basic QM, and more courses in applications of it, read lots of papers, and then research on top of that. That's in addition to having years of learning the classical foundations of physics.
steevey Posted February 24, 2011 Posted February 24, 2011 The electron in an atom is NOT a virtual particle. I'ver mentioned this before. You cannot assign a trajectory to an electron. That's classical, and this is quantum. Orbitals tell you where you can find the electron, if you were to look for it, now how it moves. It's angular momentum. It would be more misleading and confusing to physicists if you called it something else. QM is confusing. That's why physicists study it for a long time. I took undergraduate and graduate semester-long sequences in basic QM, and more courses in applications of it, read lots of papers, and then research on top of that. That's in addition to having years of learning the classical foundations of physics. Ok, so as a particle, an electron does in fact have some kind of motion related to angular momentum, but what about as a wave? And then why can't scientists locate the exact position of an electron at any desired moment in time if its not because they keep "appearing" and "disappearing" to new places which are random but still have specific areas where its more likely to happen?
lemur Posted February 24, 2011 Posted February 24, 2011 It's angular momentum. It would be more misleading and confusing to physicists if you called it something else. QM is confusing. That's why physicists study it for a long time. I took undergraduate and graduate semester-long sequences in basic QM, and more courses in applications of it, read lots of papers, and then research on top of that. That's in addition to having years of learning the classical foundations of physics. Ok, I think I have some logic as to how the spin of the electron makes sense. First, electrons are in motion around the nucleus so they must necessarily create a magnet field like any other moving electric charge, correct? So is this basic movement of the electron its spin? And it is quantized because the electron cannot move at different speeds, but the direction can change, which is why spin and magnetic polarity can change direction? Is this right? Something else occurred to me about electrons and their angular momentum, but I don't know if it would be too much a diversion to post it in this thread. Basically, I'm thinking about the relationship between the magnetic field generated by spin and the way a photon is produced when the electron changes levels. Specifically, I'm wondering if this has to do with separation of the magnetic and electric fields of the electron due to a moment of relative stasis (since electric and magnetic fields seem to only be able to exist separately when they're not moving). Should I start a different thread about this?
swansont Posted February 24, 2011 Posted February 24, 2011 Ok, so as a particle, an electron does in fact have some kind of motion related to angular momentum, but what about as a wave? And then why can't scientists locate the exact position of an electron at any desired moment in time if its not because they keep "appearing" and "disappearing" to new places which are random but still have specific areas where its more likely to happen? No, there is no physical motion associated with spin. There is no exact position to locate. Again, you cannot model this classically and have it make any sense. Any analogy you draw with macroscopic phenomena will probably fail. Ok, I think I have some logic as to how the spin of the electron makes sense. First, electrons are in motion around the nucleus so they must necessarily create a magnet field like any other moving electric charge, correct? So is this basic movement of the electron its spin? And it is quantized because the electron cannot move at different speeds, but the direction can change, which is why spin and magnetic polarity can change direction? Is this right? No. The orbital motion is not classical, and spin is not the same as orbital motion. It is intrinsic to the electron. Something else occurred to me about electrons and their angular momentum, but I don't know if it would be too much a diversion to post it in this thread. Basically, I'm thinking about the relationship between the magnetic field generated by spin and the way a photon is produced when the electron changes levels. Specifically, I'm wondering if this has to do with separation of the magnetic and electric fields of the electron due to a moment of relative stasis (since electric and magnetic fields seem to only be able to exist separately when they're not moving). Should I start a different thread about this? Probably, since it may deal with different misconceptions.
lemur Posted February 24, 2011 Posted February 24, 2011 No, there is no physical motion associated with spin. There is no exact position to locate. Again, you cannot model this classically and have it make any sense. Any analogy you draw with macroscopic phenomena will probably fail. No. The orbital motion is not classical, and spin is not the same as orbital motion. It is intrinsic to the electron. Probably, since it may deal with different misconceptions. Sometimes I think the only point to things you say is to reduce everything to equations.
swansont Posted February 24, 2011 Posted February 24, 2011 Sometimes I think the only point to things you say is to reduce everything to equations. What you can communicate in physics is extremely limited without them.
mississippichem Posted February 24, 2011 Posted February 24, 2011 Sometimes I think the only point to things you say is to reduce everything to equations. The English language wasn't designed with Quantum mechanics in mind. Nobody here is trying to reduce everything to equations, that's just the way things have to be. I wish some things could be explained with some simple analogy, but the fact is that many things in science cannot. Especially in quantum mechanics where the whole subject is quite counter intuitive. If we could explain the behavior of atoms and particles with classical mechanics then we wouldn't need quantum mechanics at all.
lemur Posted February 24, 2011 Posted February 24, 2011 The English language wasn't designed with Quantum mechanics in mind. Nobody here is trying to reduce everything to equations, that's just the way things have to be. I wish some things could be explained with some simple analogy, but the fact is that many things in science cannot. Especially in quantum mechanics where the whole subject is quite counter intuitive. If we could explain the behavior of atoms and particles with classical mechanics then we wouldn't need quantum mechanics at all. I thought that there were specific reasons that the Bohr model and other models failed and that quantum mechanics was correcting for these failures by incorporating the finding that light, electrons, etc. are limited to whole-unit amounts. I don't know why I'm even bothering to get into this discussion, because once it gets to this point there's nothing I can do as a math-aversive thinker to convince you that no math is possible with corresponding qualitative ideas that the equation describes and/or predicts in accurate detail. Yes, I know that a formula like F=MA explains force to me in terms of speed-change of an object with mass, but I also know how to explain it in words about phenomena that can be described and explained. I don't understand how quantum physics should not be translatable in this way.
steevey Posted February 24, 2011 Posted February 24, 2011 (edited) The English language wasn't designed with Quantum mechanics in mind. Nobody here is trying to reduce everything to equations, that's just the way things have to be. I wish some things could be explained with some simple analogy, but the fact is that many things in science cannot. Especially in quantum mechanics where the whole subject is quite counter intuitive. If we could explain the behavior of atoms and particles with classical mechanics then we wouldn't need quantum mechanics at all. Mathematics for unobservable things is based on words put into terms of numeric values, there has to be some way to describe it which logically equals the equation otherwise the equations would be meaningless and no one would know what they represent. Maybe Heisenberg forgot to mention it in his diary or only high esteemed physicists know. No, there is no physical motion associated with spin. There is no exact position to locate. Again, you cannot model this classically and have it make any sense. Any analogy you draw with macroscopic phenomena will probably fail. If there is no physical spin or physical thing that is the electron going at an angle, how does angular momentum exist? Is it more of a way to measure the orbitals? It seems as though "energy" and "angular momentum" in QM seem to be the same thing, since one unit of angular momentum makes an electron leap up 1 orbital, and a photon with 1 eV (or something along those lines) makes an electron leap up 1 orbital. I can see an electron as a wave just fine, but what I don't see is how this constant "angular momentum" fits in anywhere. I just can't seem to work out what x is in z=cos(log(Ln(x+z^cosh+y-(2/acos(t/y)))^tan(Q)+U^tan(J))))^tan(90) Edited February 25, 2011 by steevey
swansont Posted February 25, 2011 Posted February 25, 2011 If there is no physical spin or physical thing that is the electron going at an angle, how does angular momentum exist? Is it more of a way to measure the orbitals? It seems as though "energy" and "angular momentum" in QM seem to be the same thing, since one unit of angular momentum makes an electron leap up 1 orbital, and a photon with 1 eV (or something along those lines) makes an electron leap up 1 orbital. No, there are transitions where the principle quantum number doesn't change. A spin-flip transition. The change in angular momentum is in multiples of [imath]\hbar[/imath]. Changes in energy have no similar basic unit, i.e. the energy of different transitions are not multiples of each other.
steevey Posted February 25, 2011 Posted February 25, 2011 (edited) No, there are transitions where the principle quantum number doesn't change. A spin-flip transition. The change in angular momentum is in multiples of [imath]\hbar[/imath]. Changes in energy have no similar basic unit, i.e. the energy of different transitions are not multiples of each other. I'm still not seeing how angular momentum plays out in the picture if spin or angular momentum has nothing to do with any physical motion. Is it derived from the Bohr model since electrons occupied circular orbitals and therefore were always accelerating in a different direction but in a constant pattern? I thought the Bohr model was wrong. If I just have this piece of matter thats a wave, and then it gets determined to be a single point, does its virtual-particle-ness disappear? And if so, is it that there is a physical motion caused by angular momentum, however an electron is moving so fast with no determined pattern that we can't tell exactly where it is? But if it has only 1 specific quantized angular momentum, and its only acting as a particle and not at all like a virtual particle, what's stopping scientists from actually finding an exact position or determining where it will be next? Edited February 25, 2011 by steevey
swansont Posted February 25, 2011 Posted February 25, 2011 I'm still not seeing how angular momentum plays out in the picture if spin or angular momentum has nothing to do with any physical motion. Is it derived from the Bohr model since electrons occupied circular orbitals and therefore were always accelerating in a different direction but in a constant pattern? I thought the Bohr model was wrong. If I just have this piece of matter thats a wave, and then it gets determined to be a single point, does its virtual-particle-ness disappear? And if so, is it that there is a physical motion caused by angular momentum, however an electron is moving so fast with no determined pattern that we can't tell exactly where it is? But if it has only 1 specific quantized angular momentum, and its only acting as a particle and not at all like a virtual particle, what's stopping scientists from actually finding an exact position or determining where it will be next? I've explained a number of time that it's not a virtual particle. It's getting to the point of being really annoying that you keep incorporating that into your questions. It's not derived form the Bohr model. It's observed by experiment, and incorporated into quantum mechanics. It's not tied in with discrete trajectories, because they don't exist. That's the way quantum mechanics is, and how these systems behave. Angular momentum tells us that some transitions are not possible. Because a photon is spin-1, you cannot have a photon absorption get you between certain states, e.g. from an S state to a D state, because they differ by 2 units of angular momentum. You also can't go from an S state to another S state, because the angular momentum must change by 1. (these are called selection rules)
steevey Posted February 25, 2011 Posted February 25, 2011 (edited) I've explained a number of time that it's not a virtual particle. It's getting to the point of being really annoying that you keep incorporating that into your questions. It's not derived form the Bohr model. It's observed by experiment, and incorporated into quantum mechanics. It's not tied in with discrete trajectories, because they don't exist. That's the way quantum mechanics is, and how these systems behave. Angular momentum tells us that some transitions are not possible. Because a photon is spin-1, you cannot have a photon absorption get you between certain states, e.g. from an S state to a D state, because they differ by 2 units of angular momentum. You also can't go from an S state to another S state, because the angular momentum must change by 1. (these are called selection rules) Maybe electrons aren't virtual particles, but I keep seeing in places that they seem to "pop" in and out of different locations with no discrete pattern. In fact, I've even heard that electrons themselves pop in and out of existence in different locations very quickly almost quote-ably. But if thise isn't a virtual particle, what makes an electron different? Another way I heard it was that electrons, as particles, can appear in different locations without existing or passing through in the intervening space. But also, I don't see what about spin actually exists in reality. I have a hydrogen atom, surrounded by a single electron. The electron is a wave-particle which when undetermined takes the form of a specific shape, which I think is "S" for "sphere". Where's the angular momentum in this electron which is just a wave? It's just a wave that has the form of a sphere. Unless that doesn't matter because observable things only occur with particles in a determined state, making a wave act as single particle, but they still have no discrete path, so how is their angular momentum even constant if the path it takes isn't specific? It could go one direction, or the other. It could go that way, or the other way, with no predictable motion, so how does a physical spin exist? Edited February 25, 2011 by steevey
swansont Posted February 25, 2011 Posted February 25, 2011 Maybe electrons aren't virtual particles, but I keep seeing in places that they seem to "pop" in and out of different locations with no discrete pattern. In fact, I've even heard that electrons themselves pop in and out of existence in different locations very quickly almost quote-ably. But if thise isn't a virtual particle, what makes an electron different? Another way I heard it was that electrons, as particles, can appear in different locations without existing or passing through in the intervening space. Discussions of virtual particle/antiparticle pairs are not discussions about electrons in an atom. But also, I don't see what about spin actually exists in reality. I have a hydrogen atom, surrounded by a single electron. The electron is a wave-particle which when undetermined takes the form of a specific shape, which I think is "S" for "sphere". Where's the angular momentum in this electron which is just a wave? It's just a wave that has the form of a sphere. Unless that doesn't matter because observable things only occur with particles in a determined state, making a wave act as single particle, but they still have no discrete path, so how is their angular momentum even constant if the path it takes isn't specific? It could go one direction, or the other. It could go that way, or the other way, with no predictable motion, so how does a physical spin exist? I can't explain that. To or paraphrase Feynman what I can explain, I can't explain in terms you understand. (It's not a matter of simplifying the terminology, it's a matter of you taking, and passing, three years of physics at a university)
StringJunky Posted February 25, 2011 Posted February 25, 2011 (edited) Discussions of virtual particle/antiparticle pairs are not discussions about electrons in an atom. I can't explain that. To or paraphrase Feynman what I can explain, I can't explain in terms you understand. (It's not a matter of simplifying the terminology, it's a matter of you taking, and passing, three years of physics at a university) I remember a scientist once described the language of Quantum Physics like this: Twas brillig, and the slithy toves. Did gyre and gimble in the wabe. Edited February 25, 2011 by StringJunky
Klaynos Posted February 25, 2011 Posted February 25, 2011 ! Moderator Note The universe is under no obligation to be understandable by you. Having said that, just because you don't understand something doesn't mean no one does. Things are hard, sometimes you need a lot of fundamentals before the interesting stuff becomes clear.
StringJunky Posted February 25, 2011 Posted February 25, 2011 ! Moderator Note The universe is under no obligation to be understandable by you. Having said that, just because you don't understand something doesn't mean no one does. Things are hard, sometimes you need a lot of fundamentals before the interesting stuff becomes clear. I wasn't contesting what Swansont said...I was just contributing somebody else's take on the problem of understanding it. The Jabberwocky quote was the scientist's way of saying that Quantum physics has it's own logic ,language and internal consistency.
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