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Maxwells theory of electro-magnetic radiation:

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McQueen
#1
Jul28-04, 05:37 AM
P: 265
Maxwells theory of electromagnetic radiation has been around for the past two hundred odd years. Although it is probably one of the most elegant and aesthetic theories ever to be introduced in the study of Physics , today it is an anachronistic and misleading theory , based for the most part on faulty logic and observation. It accurately reflects the age in which it was conceived and is reminiscent of an eighteenth century steam engine more than anything else , Maxwell envisions electromagnetic radiation as huffing and puffing its way across the vast reaches of space. The whole conception of electric and magnetic fields alternatively exchanging energy and thereby sustaining themselves is at heart erroneous for the simple reason that there are no electric and magnetic fields per se , there are only electromagnetic fields. To speak of an electric field is wrong , there are no electric fields The field in and around a charged capacitor is frequently referred to as an electric field , in fact if a definition of an electric field exists it might be said to be represented by the field associated with a charged capacitor , yet this field is definitely not an electric field it is an electromagnetic field . How then can Maxwell’s theory possibly make sense or continue to possess any validity. Even particle physicists speak blandly of results obtained under the influence of a strong magnetic field when what they actually mean is a strong electromagnetic field. The premise that electric and magnetic fields have an independent existence has fragmented the whole of physics to such an extent that it is difficult to envision ever replacing these concepts even if our whole understanding of physical phenomenon depends on such changes being made.
Consider also this notion of spinning electrons , where has this come from. So OK the atomic model was originally based on the planetary model , it is common knowledge that the earth spins , ergo the electron must also spin ! If this is indeed the reason for the spin of a particle gaining such wide-spread acceptance , then consider this , the moon does not spin !
Consider again the magical aspects of the photon , it is both a particle and a wave , it can be in two places simultaneously , it always travels at the speed of light ( in a vacuum ) it can never be found at rest , except in its virtual form when present in electromagnetic fields surrounding a conductor in which a current is flowing , why it is at rest or attached to the conductor in this instance and not in others has never been explained or is explained by the fact that in this situation photons are virtual .
In short the photon stands for everything that we never see in real life. Yet things that we do see in real life are sometimes things which resemble the symbiosis of a wave and a particle , why can’t the photon be one of these ? Things have reached such a pass that it is impossible to even mention such a thought , let alone the idea ,that a photon might in fact actually be something that resembles a wave and a particle , such as a very high frequency wave . Apparently it is not possible , it has to be both a wave and a particle depending upon how it is viewed. With such intransigence on the part of modern day physicists in even considering possibilities to explain the seeming contradiction in a photon , it must inevitably follow that change is almost impossible.
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anti_crank
#2
Jul28-04, 10:37 PM
Sci Advisor
P: 131
Normally I'd grill a post like this, but that's getting old. Let's try some reason and see what happens
Quote Quote by McQueen
Maxwells theory of electromagnetic radiation has been around for the past two hundred odd years. Although it is probably one of the most elegant and aesthetic theories ever to be introduced in the study of Physics , today it is an anachronistic and misleading theory , based for the most part on faulty logic and observation.
Actually Maxwell's theory remains as elegant and useful today as it was then, especially when written in four-vector form. It survived both special relativity and quantum mechanics. It was only superseded by Quantum Electrodynamics, which predicts deviations from eg the Coulomb potential. Hmmmm... perhaps we should teach that in first year physics.
It accurately reflects the age in which it was conceived and is reminiscent of an eighteenth century steam engine more than anything else , Maxwell envisions electromagnetic radiation as huffing and puffing its way across the vast reaches of space. The whole conception of electric and magnetic fields alternatively exchanging energy and thereby sustaining themselves is at heart erroneous for the simple reason that there are no electric and magnetic fields per se , there are only electromagnetic fields. To speak of an electric field is wrong , there are no electric fields The field in and around a charged capacitor is frequently referred to as an electric field , in fact if a definition of an electric field exists it might be said to be represented by the field associated with a charged capacitor , yet this field is definitely not an electric field it is an electromagnetic field . How then can Maxwellís theory possibly make sense or continue to possess any validity. Even particle physicists speak blandly of results obtained under the influence of a strong magnetic field when what they actually mean is a strong electromagnetic field. The premise that electric and magnetic fields have an independent existence has fragmented the whole of physics to such an extent that it is difficult to envision ever replacing these concepts even if our whole understanding of physical phenomenon depends on such changes being made.
The only way you can say that with a straight face is if you've never taken an advanced EM course where they introduce the *gasp* electromagnetic field tensor. The non-existence of separate electric and magnetic phenomena is clearly stated in this context. Having said that, there is nothing wrong with treating the fields non-covariantly by sticking to a particular frame of reference and stating that "the fields created by charges that are stationary in this frame will henceworth be denoted electric fields". Implied is the understanding that this simply means certain components of the electromagnetic field tensor are zero in that frame, and will be non-zero upon Lorentz transformations to other frames. Historically, electric and magnetic phenomena were thought to be separate, but after Maxwell's theory, that was shown not to be the case. This was before SR, so in fact Maxwell's theory did the exact opposite to what you're suggesting. It unified, not separated.
Consider also this notion of spinning electrons , where has this come from. So OK the atomic model was originally based on the planetary model , it is common knowledge that the earth spins , ergo the electron must also spin ! If this is indeed the reason for the spin of a particle gaining such wide-spread acceptance , then consider this , the moon does not spin !
Whoever gave you this picture of spin of particles should not be allowed to teach, as no physicist worth his salt will suggest it. The spin of electrons, photons, whatever, is intrinsically determined by the relativistic wave equation of the free particle - Klein-Gordon for spin-0, Dirac for spin-1/2, and Proca for spin 1. The particles satisfying Dirac or Proca equations can be shown to carry a form of intrinsic angular momentum since the angular momentum operator does not commute with the free particle Hamiltonian. (I am giving you credit for a lot of quantum mechanics, if you don't have it please pick up a textbook and study it). String theory offers its own model for particle spin, but it is not currently accepted as mainstream.

Consider again the magical aspects of the photon , it is both a particle and a wave , it can be in two places simultaneously , it always travels at the speed of light ( in a vacuum ) it can never be found at rest , except in its virtual form when present in electromagnetic fields surrounding a conductor in which a current is flowing , why it is at rest or attached to the conductor in this instance and not in others has never been explained or is explained by the fact that in this situation photons are virtual .
Nothing magical about it. Counterintuitive, perhaps, but our theories can accomodate it nicely. The universe is under no obligation to live up to our expectations. QM deals with the "particle and wave" aspect and SR deals with the "always travelling at c" aspect. In fact the Maxwell equations you so hate predict that latter aspect of the photons. As for it being in two places at once - I assume you are think along the lines of the double slit experiment? It is certainly never in two places at once if you are thinking of a particle appearing in two places at once. A wave, however, is never anywhere in particular, and our universe has decreed that everything has some wavelike properties.
As for virtual photons, they are the result of our using Feynman's techniques for QED. They have no physical existence. Even if they do, your example is one of the most awful uses of QED I've ever seen. I assume you just picked it up somewhere, please let it go, it is an incorrect picture.
In short the photon stands for everything that we never see in real life. Yet things that we do see in real life are sometimes things which resemble the symbiosis of a wave and a particle , why canít the photon be one of these ? Things have reached such a pass that it is impossible to even mention such a thought , let alone the idea ,that a photon might in fact actually be something that resembles a wave and a particle , such as a very high frequency wave . Apparently it is not possible , it has to be both a wave and a particle depending upon how it is viewed.
I am not sure what you mean. Quantum field theory nicely deals with the photon as being something that resembles BOTH a wave and a particle - a quantum of the EM field. Again, please pick up a competent textbook on modern physics - have you been reading one of those books written by some crackpot who thinks he knows everything the physics community doesn't? It seems to me that you are unaware that physics already does those things you're saying it should.
With such intransigence on the part of modern day physicists in even considering possibilities to explain the seeming contradiction in a photon , it must inevitably follow that change is almost impossible.
If this translates to either of ...

a) "I believe there's a huge conspiracy amongst scientists to cover up the fact that all our theories are crap"
b) "I don't like our current theories because they contradict my 'common sense' preconceptions, and I don't understand the level to which they have been tested or how hard it was to make the paradigm shift to them"
c) "I have my own pet theory that I think is better than everything those physics bigots have but those physics bigots will never accept it because they're bigots and intransigents and they want the glory for themselves"

... you need to let go of that view right now, throw away whatever you've been reading if you picked it up somewhere, and learn what physics is all about. I will be glad to recommend books on the topics you seem to lack understanding of. If on the other hand you have already made up your mind about the mainstream theories and are absolutely determined to become a crackpot or crank, well I can't stop you. I'll be around.
Chronos
#3
Jul28-04, 10:54 PM
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When my car 'burps' I tweak it, not run it off a cliff and buy a new one.

McQueen
#4
Jul31-04, 11:08 AM
P: 265
Maxwells theory of electro-magnetic radiation:

In reply to Anti-crank
Actually Maxwell's theory remains as elegant and useful today as it was then, especially when written in four-vector form. It survived both special relativity and quantum mechanics. It was only superseded by Quantum Electrodynamics, which predicts deviations from eg the Coulomb potential.

If we accept the fact that Maxwell’s theory is correct , how would this account for the existence of photons as individual ‘packets ‘ of energy? Maxwell’s theory of electromagnetic radiation is essentially a wave theory which works in the broader sense but fails in the more specific sense.
In the photoelectric effect Maxwell's wave theory predicts that as the intensity of light is increased, the current flow should also increase. The frequency should not affect the maximum kinetic energy of the photoelectrons. In reality the intensity of the light has nothing to do with photo-electric emission and it is only the frequency of the incident light which has any effect.
Maxwell confirmed that electromagnetic waves are generated by accelerating electric charges. Consequently, there developed a theory for the emission of light as being due to the oscillatory motion of electric charges located in the atoms of the radiating source.
Today we know that in fact the emission of light is due to electrons gaining and losing energy and not as was thought due to their rotation around the nucleus. This particular point is a good illustration of the reasoning I have been trying to follow. While it is admitted that light is emitted by electrons changing their energy levels , electromagnetic radiation of lower frequency such as radio-waves is still attributed to the oscillatory motion of ions and electrons in the crystal lattice of the conductor. So what we have in effect is two causative factors for what is essentially the same phenomenon , electromagnetic radiation. The point is that even gamma rays (another form of electromagnetic radiation ) are created through a similar process , namely through the nucleus losing or gaining energy . For instance it would be ridiculous to suggest that gamma rays are produced through the oscillatory motion of nucleons . The next thing is , how is electrical energy conducted through an electrical conductor ? The widely accepted notion is that it is through electrons , but electrons only interact through photons , yet photons are prohibited from the electrical conduction process by the Pauli Exclusion Principle. The only answer left is that electrical energy must be transmitted through “virtual” photons , which is ridiculous. This is precisely the point I am trying to make. If we accept Maxwell’s theory of a displacement current , it means that electromagnetic forces (i.e fields ) are excluded from the process of the conduction of electrical energy. In reality electrical energy , (look at transformers ) must be conducted through electromagnetic forces . In turn electromagnetic forces must be mediated by photons . However because Maxwell’s theory needs a displacement current in order to work it specifically prohibits this. Light ( a form of electromagnetic radiation ) travels through solids from atom to atom and electron to electron , why can’t the same process apply to lower frequency electromagnetic radiation (i.e top a current flowing in a conductor ) ?
The spin of electrons, photons, whatever, is intrinsically determined by the relativistic wave equation of the free particle - Klein-Gordon for spin-0, Dirac for spin-1/2, and Proca for spin 1. The particles satisfying Dirac or Proca equations can be shown to carry a form of intrinsic angular momentum since the angular momentum operator does not commute with the free particle Hamiltonian

Accepted , but the notion of spin was first instituted by Henri Lorentz , who keeping in mind Maxwell’s theory and the negative charge of the electron felt that there had to be an additional motion of the electron to account for the magnetic properties , which he had suggested might be due to its spin. This theory was revived by Dirac and others.
Nothing magical about it. Counterintuitive, perhaps, but our theories can accomodate it nicely. The universe is under no obligation to live up to our expectations. QM deals with the "particle and wave" aspect and SR deals with the "always travelling at c" aspect.
All these properties of the photon and other sub-atomic particles as manifested in the “Double Slit Experiment “ would be perfectly accounted for by an aether type of scenario. Before scoffing at this statement , you should realize that QM itself has put forward a theory of an aether of sorts. Without this aether theory of QM there would be no way for QED to work.
anti_crank
#5
Aug1-04, 12:54 AM
Sci Advisor
P: 131
My deepest apologies. I had written two pages worth of reply but the godforsaken site ate it - I was logged out (timeout?) before I got a chance to post and it vanished at the compose screen. I do not have the mental strength to rewrite it now. **slams keyboard**
Epsilon Pi
#6
Aug1-04, 07:16 PM
P: 193
Just two points regarding this most serious and documented post:
Why the notion of spin was so determined by a newtonian mechanics concept, such as those, they are normally used to describe it?
Is it not that notion of spin an entirely electromagnetic notion? In fact the electron has an intrinsic "magnetic" field or, as it were, an intrinsic magnetic property, why should we try then to explain something that is intrinsic, within the concepts of another old paradigm?

Just some inquisite thoughts

Regards

EP


Quote Quote by McQueen
Accepted , but the notion of spin was first instituted by Henri Lorentz , who keeping in mind Maxwell’s theory and the negative charge of the electron felt that there had to be an additional motion of the electron to account for the magnetic properties , which he had suggested might be due to its spin. This theory was revived by Dirac and others.
anti_crank
#7
Aug2-04, 02:53 AM
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P: 131
If we accept the fact that Maxwellís theory is correct , how would this account for the existence of photons as individual Ďpackets Ď of energy? ... In reality the intensity of the light has nothing to do with photo-electric emission and it is only the frequency of the incident light which has any effect.
This can be explained via QFT, or by the 'old' QM where EM waves are given ad hoc particle properties. I donít claim that Maxwell's model explains the photoelectric effect, but that the Schroedinger or Dirac equations can incorporate interactions with a classical electromagnetic field described by the potentials V and A. In fact, the first-order approximation to QED amounts - as far as interactions between charges are concerned - to classical electromagnetism, as well as the required particle properties for photons. Because itís a rather rigorous proof, itís a little long to state here, but Iíll make use of this later on.
Maxwell confirmed that electromagnetic waves are generated by accelerating electric charges. ... For instance it would be ridiculous to suggest that gamma rays are produced through the oscillatory motion of nucleons .
The only thing that varies between those situations is the spacing of the energy levels, as the emitted photons have to carry it away. Since the only intrinsic properties of a photon are its energy and angular momentum, we have (quite arbitrarily) broken them down into different groups based on their energy. Most of these distinctions are historical, when it was not understood that they can all be lumped under the term 'photon' or EM radiation. The distinctions remain useful today, but one should not read too much into it. And indeed the thermal motion of nucleons will never reach energies required to produce gamma rays.
The next thing is , how is electrical energy conducted through an electrical conductor ? ... why canít the same process apply to lower frequency electromagnetic radiation (i.e top a current flowing in a conductor ) ?
Iím a bit unsure as to your exact point, but once again it seems that there is a huge gap between the model you *think* physics uses, and the model physics does use. Electrical energy is NOT something that is transmitted down the wire. In fact I don't think that there IS such a thing - it's sometimes being taught in high school, but it's a lousy concept. If you give me what you think is the formal definition of electrical energy, I can clear up that misconception for you. Maybe you are thinking of voltage difference as between the two ends of a battery? Energy *can* be stored in EM fields, but not in the way you're suggesting. In reality, though electrons do move within the wire, they simply drift between a high and a lower potential. The EM field is the physical entity that 'tells' them what the potential is at a point in space (or rather, the difference between adjacent points in space, since the potential is not absolute). There is nothing wrong with picturing virtual photons carrying this message, although it is somewhat misleading. In fact this is the reason the concept of a field was invented in the first place, long before it was quantized and gained a life of its own. As for energy, what happens is that as charges are pushed from regions of high potential to low potential, they gain kinetic energy which can be used to extract work out of the system. There are some very low frequency EM waves emitted by wires due to various electron scattering, small fluctuations in the driving potential etc, but I'm guessing that's not what you're thinking of.
As for transformers, what does the displacement current term have anything to do with them? I challenge you to mathematically show that the displacement current makes them not work. I think they were around even before Maxwell wrote his equations. They're all about EM induction, which is nicely explained by Maxwell - and hence low energy QED. EM fields are present in the transformers, yes, but it is the action of those fields on the electrons in the wires that makes the transformer do its job. Hence virtual photons (if you want to think of it this way, but I will not defend that model too far) are present - they carry information between the driving AC voltage in the primary coil to the electrons in that coil, from the electrons in the primary to the electrons in the secondary, and from the electrons in the secondary to whatever device it is attached to. On the other hand, the displacement current is absolutely required for the consistency of the framework and for the existence of (classical) EM waves.
photons are prohibited from the electrical conduction process by the Pauli Exclusion Principle
I have to pick on this one. This statement is so ignorant of elementary quantum mechanics that I must insist you rectify that before we debate QM any further. Photons are bosons, and do not obey the EP. As for QM's model of conduction, this is more indepth; if you're willing to make an effort to learn it, I'm willing to help along the way.
Accepted , but the notion of spin was first instituted by Henri Lorentz ... This theory was revived by Dirac and others.
As I've said, the mechanical based model of spin has long been discarded as unfeasible. If we agree, why are we beating this dead horse? Electron spin isn't a theory, it's a certitude. The experimental fact remains (Stein Gerlach experiment, spin-orbit coupling in the hydrogen atom, the periodic table in which each orbital contains two electrons in spite of the Exclusion Principle) that an electron carries an internal quantum number that can take one of two values, as well as an intrinsic angular momentum not explained by the orbital wavefunction. Any theory of the free electron has to accomodate this somehow. Before the Dirac equation, this was introduced by a Pauli spinor (a 2-component vector). The classical limits of this theory were generally off by a factor of two. The Dirac equation explained it, and has correctly explained things ever since. That we call this intrinsic degree of freedom 'spin' is the only common thread with that model.
All these properties of the photon and other sub-atomic particles as manifested in the ďDouble Slit Experiment ď would be perfectly accounted for by an aether type of scenario.
Let's see the math. Before you waste some time working it out, consider this. No classical theory, with or without an aether, will reproduce all the successful predictions of QM because they lack an uncertainty principle (and once you put it in, you've got QM). One can hand-wave around position-momentum uncertainty, but it would take a VERY imaginative aether theory to explain the quantization of angular momentum, or why one cannot know the x,y,z components simultaneously.
Before scoffing at this statement , you should realize that QM itself has put forward a theory of an aether of sorts. Without this aether theory of QM there would be no way for QED to work.
I have no idea what you're thinking of, and I fancy myself well versed in QED, though feel free to correct me if you believe Iím wrong in this. Are you perhaps thinking of the zero-point energy present in the quantization of the field? Or perhaps that the aether is the electromagnetic field itself? (That's not a bad picture, actually. It might be the first model you've proposed that I can agree with). QED does not explain the EM field, it postulates it, and in any event the electroweak theory currently claims ownership over the photon field - that's the place to postulate an aether. However, there are no obvious benefits from doing so - what's the difference whether we postulate the field or the aether? The reason (classical) aether was discarded is that there was no way to validate its existence, and science is minimalistic.
As for scoffing, I have done that in the past (just see my very first post), and I will do so again, whenever someone takes it upon himself to single-handedly rewrite physics, or some large portion of it. (I am not implying you are trying anything of the sort.) In every such instance that I am aware of, such people exhibit either huge gaps in their understanding of the physics they're trying to rewrite, are unaware of the enormity of their task, and/or are unable to put their speculations into a rigorous formalism. Worse still, they tend to show cognitive dissonance when the flaws in their ideas are pointed out, paranoia and/or delusions of grandeur, prejudice against the physics community, or even up to all of the above. Why uneducated (scientifically speaking, of course) people think they are capable of judging existing theories wrong or writing their own theories is utterly beyond me. I don't claim to know how to design and build a house, and if an architect does the job for me, I defer to his judgement. That may seem elitist to some, but I believe otherwise. Would you allow just anyone to perform brain surgery on you? Of course not, itís a task that requires a great deal of training and experience. Science works the same way, and frankly I am sick of the indignity it has to suffer from cranks and crackpots. No other highly skilled profession has to endure it. When's the last time you've heard some sixteen year-old claiming they can perform brain surgery? Yet here we have sixteen year-olds obstinately pushing a model of gravity so flawed it's not even worthy of my attention. Personally I blame it on the equally unexplainable anti-intellectuallism in popular culture, but I do have to give it one shred of credit: its existence, and what has come forth from it, is the main reason I live and breathe today. Virtually, of course.
McQueen
#8
Aug2-04, 08:28 AM
P: 265
This can be explained via QFT, or by the 'old' QM where EM waves are given ad hoc particle properties. I don’t claim that Maxwell's model explains the photoelectric effect, but that the Schroedinger or Dirac equations can incorporate interactions with a classical electromagnetic field described by the potentials V and A. In fact, the first-order approximation to QED amounts - as far as interactions between charges are concerned - to classical electromagnetism, as well as the required particle properties for photons. Because it’s a rather rigorous proof, it’s a little long to state here, but I’ll make use of this later on.
Some of the drawbacks of Quantum Field Theory:

The Quantum Mechanics theory for the propagation of electromagnetic radiation is represented by Quantum Field Theory . Quantum Field Theory describes processes in which particles are created or destroyed. Put simply this means that the energy of the photon is transmitted through the creation and annihilation of virtual particles. When a quantum field becomes more excited , the number of quanta of excitation increases. This occurs because new particle-anti particle pairs are created from radiation. When a quantum field becomes less excited the number of quanta of excitation decreases. This is achieved by processes in which particles and anti-particles collide and annihilate one another to produce radiation. (Both of these processes are permitted by Einstein’s
E = mc2 and were explicitly predicted by Dirac . However the equation E = mc2
Does not suggest that these interactions can take place at the low energies present in an electromagnetic field , which can typically be as low as 10 –19 eV , according to Einstein’s theory the minimum energy for transformations to take place should be at least 1.5 MeV.]
These were attractive features of quantum field theory and raised the hope that it might be truly a fundamental theory capable of providing a new world view. However there were serious problems within quantum electrodynamics that had to be overcome before such hopes stood any chance of being realized. Using QED to predict the value of a physically measurable quantity involved , in practice , working out the contribution made by several different sub-processes . Put in other words how does the translation of a specific energy evolve through interaction via the creation and annihilation of virtual particles . Making sure that these sub-processes were fully identified was a problem in itself , working out their individual contributions was even worse. Even in the simplest cases determining the contribution was difficult , and in the more complicated cases the result was usually a meaningless infinity showing that something was wrong.
Put simply Quantum Field Theory does not work , it attempts to juxtapose the alternating electric and magnetic fields of Maxwell’s theory with the creation and annihilation of virtual particle pairs. The question of how theory electromagnetic waves propagate is still open to question.
I have to pick on this one. This statement is so ignorant of elementary quantum mechanics that I must insist you rectify that before we debate QM any further. Photons are bosons, and do not obey the EP. As for QM's model of conduction, this is more indepth; if you're willing to make an effort to learn it, I'm willing to help along the way.
I am sorry you are wrong , I cannot at the moment post the mathematical proof , but I have it here somewhere. Free electrons , such as those found in counductors , according to the EP cannot absorb or emit photons becuase they can't cope with the recoil. It is in every elementary text book. I will post a longer reply later dealing with the other points.
anti_crank
#9
Aug3-04, 01:24 AM
Sci Advisor
P: 131
Quote Quote by McQueen
The Quantum Mechanics theory for the propagation of electromagnetic radiation is represented by Quantum Field Theory . Quantum Field Theory describes processes in which particles are created or destroyed. Put simply this means that the energy of the photon is transmitted through the creation and annihilation of virtual particles. When a quantum field becomes more excited , the number of quanta of excitation increases. This occurs because new particle-anti particle pairs are created from radiation. When a quantum field becomes less excited the number of quanta of excitation decreases. This is achieved by processes in which particles and anti-particles collide and annihilate one another to produce radiation. (Both of these processes are permitted by Einsteinís E = mc2 and were explicitly predicted by Dirac . However the equation E = mc2 does not suggest that these interactions can take place at the low energies present in an electromagnetic field , which can typically be as low as 10 Ė19 eV , according to Einsteinís theory the minimum energy for transformations to take place should be at least 1.5 MeV.]
These were attractive features of quantum field theory and raised the hope that it might be truly a fundamental theory capable of providing a new world view.
Some good points, some less so. Quantum field theory is a branch of physics that includes several theories. Electromagnetism is just one of them; its particular theory is called quantum electrodynamics. This is a snippet of info that you should find in any of those elementary books. The description of QFT is mostly correct, but you don't mention that it has in fact already provided a new world view. It neatly accomodates particle/wave duality for all known particles by postulating that both photons and the particles that make up matter are excitations of their respective fields.
However there were serious problems within quantum electrodynamics that had to be overcome before such hopes stood any chance of being realized. Using QED to predict the value of a physically measurable quantity involved , in practice , working out the contribution made by several different sub-processes . Put in other words how does the translation of a specific energy evolve through interaction via the creation and annihilation of virtual particles . Making sure that these sub-processes were fully identified was a problem in itself , working out their individual contributions was even worse. Even in the simplest cases determining the contribution was difficult , and in the more complicated cases the result was usually a meaningless infinity showing that something was wrong.
Once again you are living in the past. QED has been renormalized, the infinities dealt with, and the contributions from those diagrams can now be included in a systematic, meaningful and testable way. QED has been tested to amazing accuracy: one of its predictions has been validated to 12-13 significant figures. Renormalization is an annoyance and whether it is introduced by some physics (ie we don't really understand the very short range behavior of the fields), or it is simply an artifact of using perturbation theory (ie the mathematics used in Feynman diagrams introduces the divergences - the field equations are impossible to solve directly), is AFAIK an open question. But the correct way to fix that is certainly not by taking a step backwards to an aether theory.
Put simply Quantum Field Theory does not work , it attempts to juxtapose the alternating electric and magnetic fields of Maxwellís theory with the creation and annihilation of virtual particle pairs. The question of how theory electromagnetic waves propagate is still open to question.
Really now... study it before making such statements. QFT is responsible for the whole Standard Model, which has been around for 20 years despite great efforts to experimentally falsify it. If you don't like it, then propose a viable alternative - we'll consider it as soon as you reproduce, say, the electron's g factor to those 13 digits. The propagation of EM waves is a closed question: they are excitations of the quantized EM field, which permeates all space. There: this is as close to an aether as you can get. The reason for the field's existence is the imposition of a local gauge symmetry. That symmetry is what's postulated.
I am sorry you are wrong , I cannot at the moment post the mathematical proof , but I have it here somewhere. Free electrons , such as those found in counductors , according to the EP cannot absorb or emit photons becuase they can't cope with the recoil. It is in every elementary text book. I will post a longer reply later dealing with the other points.
Not a chance, unless I misunderstood what you were saying. No competent textbook will claim that photons obey the exclusion principle. None. If you do find such a quote in a textbook, by all means cite it here: I will contact the author and get him to issue a correction. Let me try to decipher what you mean: no free electron can emit a real photon without something else being involved. Granted: in the electron's rest frame, there is no energy available to create a photon AND recoil; it violates energy conservation. But so what? Those are virtual photons involved, who are allowed to break almost any rule you want, as long as they're absorbed at the other end. The rigorous treatment may be found in a number of textbooks.
the energy of a photon is transmitted through the creation of virtual particle/antiparticle pairs
This is just plain wrong. Either this honestly is the picture you get from QED (in which case, do yourself a favor and study it properly; this isn't the only such 'pearl' you've let slip), or you are deliberately setting up strawmen to attack what those in the business call "the best theory we have". If you're unwilling to debate it on its own merits, then there's really no point for this discussion.
what_are_electrons
#10
Aug4-04, 06:35 PM
P: n/a
I am learning from this thread and think maybe you could help me with a related question.

Do you know of any experiment done in ultrahigh vacuum that has shown that any wavelength of light (as a beam or a single photon) has been deflected or changed in any way by a simple or complex, pulsing or static, electric field, magnetic field or an EM field?
McQueen
#11
Aug5-04, 02:56 AM
P: 265
This is just plain wrong. Either this honestly is the picture you get from QED (in which case, do yourself a favor and study it properly; this isn't the only such 'pearl' you've let slip), or you are deliberately setting up strawmen to attack what those in the business call "the best theory we have". If you're unwilling to debate it on its own merits, then there's really no point for this discussion.


It took two thousand years for Ptolemy’s ideas to be discarded , it took much longer than that for Newton’s idea that objects will move indefinitely in a straight line unless subjected to some outside force to be enunciated ,and so on. I stress this point in order to demonstrate that merely the fact of an idea having been accepted for the past twenty or thirty years does not mean that it is true. Any opposition or change to accepted ideas , especially in science , has always resulted in fanatical opposition. QM itself was for a long time , subject to this kind of opposition , going back a little further in time , people were burnt at the stake if they so much as suggested that the earth might revolve around the sun or even that the earth was round ! In today’s enlightened scientific environment the least one can expect is , if not acceptance , then a certain amount of tolerance. In this respect PHYSICS FORUMS stands out almost alone on the web , in allowing people to air their views , regardless of how outrageous , in the theory forum.
It is not always easy to explain such an abstract theory as QM in layman’s terms , or to convince someone with different ideas , given these limitations , of the validity of one’s own ideas. The option always exists , however , if one is interested enough , of looking into new ideas and trying to judge if they possess any foundation.
In Quantum Field Theory more importance is given to fields than to matter , fields are all pervasive in the Universe while matter is merely a consequence of the interaction of fields . We are able to view matter as particles because fields tend to interact powerfully over infinitesimal areas. Hence , according to QFT , every field is associated with a particle and conversely every particle is associated with a field. Thus we have the electric field associated with electrons , the magnetic field associated with magnetons , the electromagnetic field associated with photons , the sound field associated with phonons , the gravitational field associated with the graviton and the list goes on through the strong force and the weak force and various other forces.
Hence according to Quantum Field Theory matter is only a manifestation of the interaction of fields. The three main ideas underlying this theory are (1) sub-atomic particles have no independent existence (2) sub-atomic particles display characteristics of wave-particle duality (3) sub-atomic particles are/maybe manifestations of interacting fields.
My own take on all this , is that QM is unequalled in explaining the working of the atom and interactions of the nucleus. When it comes to macroscopic phenomenon , and this is just my view , QM has gone catastrophically astray in accepting wave-particle duality as a fundamental axiom .
I have posted this site in another thread , you might be interested in looking through it: http://www.geocities.com/natureoflight/pgindex
what_are_electrons
#12
Aug7-04, 10:20 PM
P: n/a
Quote Quote by McQueen

..... My own take on all this , is that QM is unequalled in explaining the working of the atom and interactions of the nucleus. When it comes to macroscopic phenomenon , and this is just my view , QM has gone catastrophically astray in accepting wave-particle duality as a fundamental axiom .
I have posted this site in another thread , you might be interested in looking through it: http://www.gecoities.com/natureoflight/pgindex
I quite agree that QED is great, but QM as applied to atoms is a mess. QM can not, without too many approximations, define the nature and properties of even Helium. A probable reason for this is that we do not know enough about the true nature of the electron, the proton or the neutron. In a similar vein, we have a problem with the photon. If you doubt my writing, grab the latest symposium review on the electron or the photon, or grab one of the books titled "The Enigmatic Electron" or "The Engimatic Photon".
Vern
#13
Aug7-04, 11:00 PM
P: 123
Quote Quote by what_are_electrons
Do you know of any experiment done in ultrahigh vacuum that has shown that any wavelength of light (as a beam or a single photon) has been deflected or changed in any way by a simple or complex, pulsing or static, electric field, magnetic field or an EM field?
"Fundamentals of Photonics", Saleh and Teich,Wiley Interscience, 1991
Chapter 19, NonLinear Optics.

There is a wealth of interactions using electromagnetics to control light. That is the chapter that shows how to construct a conjugate mirror which reflects light back directly the way it came in instead of at right angles. Interesting stuff !!

Keep on chuggin !!

Vern
Chronos
#14
Aug8-04, 01:10 AM
Sci Advisor
PF Gold
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P: 9,380
Interesting discussion. Points scored on both sides by my reckoning. I tend to lean towards the standing wave concept [matter is 'frozen' energy]. It makes sense. It would, however, help if someone could explain the process.
McQueen
#15
Aug8-04, 04:39 AM
P: 265
Chronos
matter is 'frozen' energy
Absolutely , I subscribe to this view. The point is how much energy is required to demostrate matter energy equivalence ? Surely not the energy present in radio waves as is implied in QM , even if these interactions are virtual ? Virtual interactions by their very classification should not impinge on the real world , even mathematically. Visit my site at http://www.geocities.com/natureoflight/pgindex
Chronos
#16
Aug8-04, 05:40 AM
Sci Advisor
PF Gold
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P: 9,380
Question: Since the known universe is presumed to be a mere 10.8E+24 meters in diameter, hence, longest EM wavelength possible, it should be easy to convert that to a temperature [you do the rest of the math, I am feeling lazy]. Will discuss what that may or may not mean after you integrate that over the upper limit imposed by the planck length.
Epsilon Pi
#17
Aug8-04, 07:10 AM
P: 193
Quote Quote by what_are_electrons
I quite agree that QED is great, but QM as applied to atoms is a mess. QM can not, without too many approximations, define the nature and properties of even Helium.
QM is based on the wave nature of energy, I mean when it is not "frozen" as Chroot has pointed out; QM is based on a complex wave equation and nuclear interactions of matter is based mostly on symmetry laws, where we have odd parity as a logical consequence; but in nature we find another kind of parity I mean even parity, as those found in weak nuclear interactions.
My point is then don't we really have a problem with the way we have coped those two different problems, I mean the symbolism we use? Must we not solve this another form of the wave-particle problem?
I know there has been invented some "theoretical mechanisms" to solve the problem of symmetry breaking we find in nature, but then I wonder again don't we have a problem with the symbolism that must include both kinds of parities? not precisely with the nature of electrons and photons that are again manifestation of energy at basic levels, at those basic levels where we find ourselves with the need to rationalize duality in a concept of unit? But this rationalization of duality at atomic levels is certainly an open problem yet, if we want to solve this another schism we find in those two schools: that of QM and that of QED at least found in text books.

Just some thoughts and questioning

Regards
EP
McQueen
#18
Aug8-04, 10:55 AM
P: 265
QM is based on the wave nature of energy, I mean when it is not "frozen" as Chroot has pointed out; QM is based on a complex wave equation and nuclear interactions of matter is based mostly on symmetry laws, where we have odd parity as a logical consequence; but in nature we find another kind of parity I mean even parity, as those found in weak nuclear interactions.

Louis de Broglie himself was never able to explain what these matter waves were , to this day no-one has really come up with a definition of what matter waves are. It is simply a mathematical construct . The reason for the adoption of matter waves was that no other explanation seemed possible to explain how atoms could exist , classical laws certainly could not explain the existence of matter. However with the realisation that electrons in the atom maintain their stabiltiy through the constant emission and absorption of virtual electrons , wave particle duality was no longer necessary to explain the fact that atoms were able to exist. Remember that the existence of virtual photons had been found by experiment , namely the Lamb shift while wave-particle duality was largely a theoretical concpet with no supporting proof except that of the double slit experiment.


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