Does a controversy still exist ?

[McQueen]

Anyway, say you've detected photon 1 wrt a certain setting of your polarizer. Now, you can change the setting of the polarizer that photon 2 is incident on while photon 2 is in flight. The probability of coincidental detection, in the ideal, is given as cos^2(theta) by qm, where theta is the angular difference between the polarizers. In effect, as you change the setting of the polarizer that photon 2 is incident on, you change the probability of detecting photon 2. How does this tell you whether FTL does or does not exist?

You don’t have to detect the photon before changing the polarization, because that has already been established to a consistent degree. And if your argument is to hold water , shouldn’t the probability of a photon being detected at A also change with the detection of the photon at B , something which apparently does not seem to happen ?

But again, at least afaik, quantum theory is not committed to FTL. (Of course, as far as anybody knows, the correlations might be due to FTL transmissions, but such an explanation isn't necessitated, so the assumption of locality is retained.) So far, from what you've written and referred to, such an FTL committment doesn't seem to follow. So, it might be good if you spell out your logical chain of reasoning that leads you to the conclusion that you're advocating.

If we look at the background of QM , it becomes clear that FTL is in fact central to many of the basic precepts of QM. I think that we can all agree that the matter waves postulated by Louis de Broglie , which became central to wave-particle duality and Schrodinger’s wave function are one of the key tents of QM. Yet according to de Broglies theory matter waves ( waves of probability according to Schrodinger ) which travel with an electron , move faster than the speed of light . And “……..the slower the electron the faster the velocity of its associated wave. (N.B ., Quote from Sir George Thomson , winner of the Nobel Prize in Physics. From his book “The Atom”) Thus it is the matter wave which guides the electron as to where to go. This being so , how is it possible to claim that FTL is not central to QM. Even the most basic foundations of QM have this concept of FTL inbuilt into them. If we take another approach , we get the same result. What is the size of an electron ? From the fact that an electron can give up all its energy on impact , it must be reasoned that its dimensions are fairly compact and localized , on the other hand since an electron can be influenced by another charge placed at a distance in space , the influence of the electron can be taken as being almost infinite. It is therefore difficult to come to a conclusion as to the exact size of an electron. This interaction or influence that the electron experiences from other electrons is what led to Schrodingers blurred or smeared (electron cloud ) description of the electron within the atom , which later was proved to be wrong. One way to avoid all this confusion is by the particle view of light . Thus if by the wave view of light we have : particle –> electromagnetic field –> particle . Then on the particle view we would have : particle -> photon -> particle . i.e., a charged particle generates a photon which is absorbed by another particle. This is the mechanism which is responsible for the force acting on these particles.

 

[McQueen]

Wrong. A phonon is not a quasiparticle. A phonon is a collective excitation, similar to a photon being an excitation out of a vacuum state.

Shouldn't the correct term be a "Virtual photon".

But, of course, quasi-particles cannot leave the crystal :-)

Is that why phonons travel at the speed of sound in space where there is no medium for which for them to travel through.

 

[ZapperZ]

Shouldn't the correct term be a "Virtual photon".

Why are you so hung-up on the NAME but not the physics involved? I could call it "cow photon", and it won't change a thing about the physics.

I still think you are "learning" these things via bits and pieces that you get off the web. I would be very suspicious of my knowledge if I were you.

Zz.

 

[McQueen]

Why are you so hung-up on the NAME but not the physics involved? I could call it "cow photon", and it won't change a thing about the physics.

I still think you are "learning" these things via bits and pieces that you get off the web. I would be very suspicious of my knowledge if I were you.

OK why can phonons travel at the speed of sound in space. Or are they restricted to within the crystal and if so why ?

 

[vanesch]

OK why can phonons travel at the speed of sound in space. Or are they restricted to within the crystal and if so why ?

They are of course restricted to the crystal. In fact, it does not even make sense to say so, because they are really a numbering scheme of the stationary states of the lattice vibrations ;

You could just as well ask if reciprocal vectors are restricted to the crystal or not.

The reason why phonons are a bit particle-like is because the mathematics looks much the same as the mathematics of the stationary states of the free Dirac field ; these stationary states are called electrons.

 

[ZapperZ]

OK why can phonons travel at the speed of sound in space. Or are they restricted to within the crystal and if so why ?

Considering that a phonon is DEFINED as the quanta of LATTICE VIBRATIONS, how do you propose to have this thing travel in space where there are no LATTICE VIBRATIONS? Phonons are not even well defined in liquid (even though there are loose usage of that term within that scenario), and certainly not defined in a gas. So think of how absurd it is to to talk about it in vacuum. You are taking the concept and then twisting it into ways it wasn't meant to be used.

Zz.

 

[McQueen]

Considering that a phonon is DEFINED as the quanta of LATTICE VIBRATIONS, how do you propose to have this thing travel in space where there are no LATTICE VIBRATIONS? Phonons are not even well defined in liquid (even though there are loose usage of that term within that scenario), and certainly not defined in a gas. So think of how absurd it is to to talk about it in vacuum. You are taking the concept and then twisting it into ways it wasn't meant to be used.

Lattice vibrations , yes , but how do they travel?Are they specially empowered , so that they can control their speed ? I know phonons have , or were , for a long time a well accepted part of physics. But still do they have some kind of special dispensation , that allows them to travel at specific speeds namely that of sound. The whole of Coulomb's theory can be derived from the fact that the photons has no mass. OK so the phonon is not actually a partcile , but surely it still is a vibration?

 

[Sherlock]

You don’t have to detect the photon before changing the polarization, because that has already been established to a consistent degree.

If the photons are polarization-entangled (which is what we want isn't it?), then their polarization isn't established prior to detection. Their polarization is random. Only the entanglement relationship is established -- and, depending on the photon pair source, then with polarizers aligned, A and B will always register the same results, or A and B will always register opposite results.
So let's say we're dealing with polarization-entangled photons that, with polarizers aligned, always register the same result at A and B for a given pair (either both detect, or both don't detect, with polarizers aligned). This is the entanglement relationship between paired photons that are produced by atomic calcium cascades, which were used by Aspect et al. in their 1982 experiment involving time-varying analyzers. Pairing the photons involves associating them with intervals controlled by coincidence circuitry (in the case of the Aspect experiment they wanted to pair photons emitted by the same atom). Since the emission time is a random variable, a coincidence interval is initiated by a detection at either A or B.

And if your argument is to hold water , shouldn’t the probability of a photon being detected at A also change with the detection of the photon at B , something which apparently does not seem to happen ?

The average photon count at A (or B) for, say, a 5 minute run, with polarizer in place is 1/2 what it is without the polarizer. The photon flux at A doesn't depend in any way on what you might do to the B side, and vice versa.
Individual detection is random, uncontrollable, unpredictable. What is controllable is the rate of coincidental detection, which is a function of the angular difference between the polarizers. This suggests that properly paired photons refer to disturbances that are related prior to detection, presumably because, in the process we're considering, they were emitted by the same atom. And, that's how qm treats the situation. No FTL implied.
As I mentioned before, there's no experiment (yet), afaik, that can definitively ascertain that FTL transmissions aren't happening between A and B during a given coincidence interval. But, there's no particular reason to suppose that the correlations must be due to anything FTL. It seems likely that the entanglement is produced via the emission process. The fact that there isn't any geometrical or mechanical visualization accompanying the qm account doesn't reinforce the notion that FTL transmissions must be involved.

If we look at the background of QM , it becomes clear that FTL is in fact central to many of the basic precepts of QM. I think that we can all agree that the matter waves postulated by Louis de Broglie , which became central to wave-particle duality and Schrodinger’s wave function are one of the key tents of QM. Yet according to de Broglies theory matter waves ( waves of probability according to Schrodinger ) which travel with an electron , move faster than the speed of light . And “……..the slower the electron the faster the velocity of its associated wave. (N.B ., Quote from Sir George Thomson , winner of the Nobel Prize in Physics. From his book “The Atom”) Thus it is the matter wave which guides the electron as to where to go. This being so , how is it possible to claim that FTL is not central to QM. Even the most basic foundations of QM have this concept of FTL inbuilt into them.

How is it possible that David Bohm wrote a 646 page textbook on quantum theory without mentioning any of these FTL considerations, except to say that, wrt quantum correlations such as we're considering here, events at A and B are not affecting each other. (Maybe I've missed something.)

Bohm and deBroglie were around at the same time weren't they? If what you say is true about matter waves moving FTL, then how did Bohm get by without mentioning it in a qm textbook?

I'm aware that Bohm published a non-local hidden variable formulation of qm after he wrote the textbook. But, afaik, that formulation was not meant to be a serious contender, but was presented to show that such an alternative, hidden variable formulation (albeit an explicitly non-local one) was possible. Maybe he did it to show that hidden variable formulations are required to be explicitly non-local. I don't know. But, it's clear in his quantum theory textbook that he's proceeding under the assumption that nature obeys the principle of locality. There are several places where he emphasizes this, and also several places where he emphasizes that hidden variable theories are not possible in a local universe wherein the experimental determination of natural processes is limited by a fundamental quantum of action and the uncertainty relations.

 

[DrChinese]

I know little about PDC. Are you saying that the two photons (which, as I understand it, are harmonics of the pump photon) transmitted by the nonlinear crystal are always polarized the same way --- or is it that their polarizations are always related?

A quick note about PDC, because it can be a little confusing. There are 2 types of PDC:

Type I PDC:
The output photons of a tuned non-linear crystal have parallel and known spin, and are NOT in superposition of spin states initially. Their spin is orthogonal (perpendicular) to that of the pump photon. So they are entangled, but not as to spin - which sounds wrong. But this is easily fixed so that we have a usable Bell state for an experiment.

This is accomplished by using 2 crystals instead of one. The crystals are placed in series but 90 degrees apart. The pump stream is placed at a 45 degree angle relative to the crystals. There is a mixing of 2 output beams - i.e. the photon pair comes out of one crystal or the other, but you don't know which. The result is a good superposition of H>H> and V>V> states that can then be tested per usual, with identical polarization.

Type II PDC:
The output photons of a tuned non-linear crystal have perdendicular (orthogonal) and UNknown spin, and ARE in superposition of spin states initially. The superposition is H>V> and V>H>. This only needs a single crystal.

It's a little more complicated than my explanation implies, but this al least disctinguishes the 2 types. I am working on a new page for my site that will explain this pictorially. I will post this when it is available.

 

[Sherlock]

A quick note about PDC, because it can be a little confusing. There are 2 types of PDC:
Type I PDC:
The output photons of a tuned non-linear crystal have parallel and known spin, and are NOT in superposition of spin states initially. Their spin is orthogonal (perpendicular) to that of the pump photon. So they are entangled, but not as to spin - which sounds wrong. But this is easily fixed so that we have a usable Bell state for an experiment.
This is accomplished by using 2 crystals instead of one. The crystals are placed in series but 90 degrees apart. The pump stream is placed at a 45 degree angle relative to the crystals. There is a mixing of 2 output beams - i.e. the photon pair comes out of one crystal or the other, but you don't know which. The result is a good superposition of H>H> and V>V> states that can then be tested per usual, with identical polarization.
Type II PDC:
The output photons of a tuned non-linear crystal have perdendicular (orthogonal) and UNknown spin, and ARE in superposition of spin states initially. The superposition is H>V> and V>H>. This only needs a single crystal.
It's a little more complicated than my explanation implies, but this al least disctinguishes the 2 types. I am working on a new page for my site that will explain this pictorially. I will post this when it is available.

Ok, thanks DrC. I've been meaning to read up on this stuff. :-)

As I understand McQueen's proposed experiment, it would have to involve polarization-entangled photons wrt which the polarization has "already been established to a consistent degree", as he puts it, prior to detection. So, his experiment is impossible to implement. Or is it?

Do you understand what he's talking about?

 

[Sherlock]

If we take another approach , we get the same result. What is the size of an electron ? From the fact that an electron can give up all its energy on impact , it must be reasoned that its dimensions are fairly compact and localized , on the other hand since an electron can be influenced by another charge placed at a distance in space , the influence of the electron can be taken as being almost infinite. It is therefore difficult to come to a conclusion as to the exact size of an electron. This interaction or influence that the electron experiences from other electrons is what led to Schrodingers blurred or smeared (electron cloud ) description of the electron within the atom , which later was proved to be wrong. One way to avoid all this confusion is by the particle view of light . Thus if by the wave view of light we have : particle –> electromagnetic field –> particle . Then on the particle view we would have : particle -> photon -> particle . i.e., a charged particle generates a photon which is absorbed by another particle. This is the mechanism which is responsible for the force acting on these particles.

The consensus among physicists (from what I've read) seems to be that quantum phenomena are essentially wave like. But, who really knows? There is, as pertains to the title of your thread, still a controversy. Exactly what photons and electrons correspond to in nature is unknown. They're mathematical constructs applied to certain phenomena. In the attempt to develop a picture of quantum reality in terms of familiar analogs it's observed that some aspects of experimental results lend themselves to a wave interpretation and some to a particle interpretation. Hence, the necessary wave-particle duality wrt our apprehension and comprehension of quantum phenomena.

It's not really clear how you propose to solve the dilemma of qualitatively describing the quantum realm.

 

[ZapperZ]

Lattice vibrations , yes , but how do they travel?Are they specially empowered , so that they can control their speed ? I know phonons have , or were , for a long time a well accepted part of physics. But still do they have some kind of special dispensation , that allows them to travel at specific speeds namely that of sound. The whole of Coulomb's theory can be derived from the fact that the photons has no mass. OK so the phonon is not actually a partcile , but surely it still is a vibration?

These are the times where I just want to smack someone on the head and say "READ THE DAMN TEXTBOOK!"

... but I won't! :)

Zz.

 

[McQueen]

These are the times where I just want to smack someone on the head and say "READ THE DAMN TEXTBOOK!"
... but I won't! :)

For which I am truly thankful. A few questions. Am I right in thinking that Schrodinger’s wave mechanics is a mathematical theory in which calculations are made of quantities which can be measured experimentally. Obviously , from the success of the theory , the answers given by the calculations can be verified , but isn’t it true that the intermediate stages in these calculations have no physical meaning ? For example simple atom structures can be explained mathematically. In a stationary state the wave reduces to a simultaneous vibration of all parts of the atom , which thus resembles a vibrating system. ( Presumably it is these vibrations that give rise to quasiparticles and phonons ?) For complex atoms the waves are determined by a mathematical process which can only be interpreted geometrically in terms of space of many dimensions. This means that the waves have no physical meaning. I can understand that mathematically this makes sense , because the extra dimensions can simply be explained by attributing different numbers or symbols to them , but where does this leaves things in terms of physical quantities ?

 

[selfAdjoint]

Obviously , from the success of the theory , the answers given by the calculations can be verified , but isn’t it true that the intermediate stages in these calculations have no physical meaning ?

The point of the mathematical physicists' algebraic local quantum theory is that all the predictions of quantum theory can be coded in an abstract Hilbert space and a suitable algebra of operators on it, satisfying certain axioms. This has SPECIFICALLY nothing to do with spacetime or our world.

You have to look outside QM itself for such relationship to the world; that is why the "measurement" questions, which seem so vacuous and philosophical refuse to go away.

No advance in the quantum side of physics makes any improvement on this; superstring theory is just as abstract-mathematical as nonrelativistic QM. That is why some of us have long placed our hopes and expectations on the gravity side of physics. "Gravity is spacetime curvature", even if wrong or just "effective", is an answer on a different level from anything QM gives.

 

[McQueen]

You have to look outside QM itself for such relationship to the world; that is why the "measurement" questions, which seem so vacuous and philosophical refuse to go away.

No advance in the quantum side of physics makes any improvement on this; superstring theory is just as abstract-mathematical as nonrelativistic QM. That is why some of us have long placed our hopes and expectations on the gravity side of physics. "Gravity is spacetime curvature", even if wrong or just "effective", is an answer on a different level from anything QM gives

Agreed. But just consider for the moment that , leaving aside for the moment anything to do with the nucleus , the whole of Quantum Mechanics resembles an inverted pyramid , with the whole weight of it resting on the properties of the photon and wave particle duality. Yet , what if the photon does not really reflect this duality ? All the premises built up from this point would collapse. It could be argued that De Broglie’s original hypotheses was not based upon the properties of the photon at all but upon matter energy equivalence . Yet this reasoning requires a huge leap since it would leave out an enormous factor , that of energy . Particle accelerators have shown that massive amounts of energy are required to bring about matter – equivalence effects in sub-atomic particles. Thus it was the photon that was and is the ultimate proof of wave-particle duality. Yet if we think lucidly , without letting any considerations get in the way , it is a highly unlikely scenario , requiring an almost alchemical amount of esoteric input. At one time it was thought that wave-particle duality was inevitable because it explained why electrons did not radiate away all their energy and spiral into the nucleus , yet with the advent of experimental proof of the Lamb effect and the discovery of self-interaction of electrons wave particle duality has to a large extent been obviated.
http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/lamb.html [/URL]
By this theory the electron balances its orbit within the atom through constant emission and absorption of “virtual” photons. If the subject is considered in a non-partisan and unbiased manner , this should make greater sense than wave-particle duality , because exactly similar “virtual” transactions and transformations are observed within the nucleus. The neutron constantly changing within the nucleus to a proton and back again. Thus the self-interaction of electrons lends continuity to the process while by contrast wave-particle duality opens completely new methodology. ( when viewed from this point of view). So if the photon is not a particle and it is not a wave what could it be ? Probably the simplest most logical answer to this question is also the correct one. Namely that the photon is neither a particle or a wave but a [symbiosis} of the two. It is a wave that has all the properties of a particle. Look at hyper-sonic sound waves , they behave to a certain extent like particles but everyone knows that they are waves. The photon might be similar , only dealing with frequencies many millions of times greater than that of sound , where the difference between particle and wave is almost indiscernible.

 

[ZapperZ]

Agreed. But just consider for the moment that , leaving aside for the moment anything to do with the nucleus , the whole of Quantum Mechanics resembles an inverted pyramid , with the whole weight of it resting on the properties of the photon and wave particle duality. Yet , what if the photon does not really reflect this duality ? All the premises built up from this point would collapse.

But if this is true, then a lot of our measurement would make NO SENSE, and what we interpret and observe would not be consistent. My photoemisson experiments would give strange results and all those optical conductivity experiments would give weird measurements, because they all made use of the QM description of light. This is what would happen when the starting premise is wrong, and when you try to use it to study other things, it will start to fall apart.

Yet, no such thing is occurring. We know so much about light and its interaction with matter that we USE it to study the properties of that matter. Go to any synchrotron center if you don't believe me. What you are claiming is inconsistent with experimental practices and evidence.

Zz.

 

[McQueen]

My photoemisson experiments would give strange results and all those optical conductivity experiments would give weird measurements, because they all made use of the QM description of light. This is what would happen when the starting premise is wrong, and when you try to use it to study other things, it will start to fall apart.
Yet, no such thing is occurring. We know so much about light and its interaction with matter that we USE it to study the properties of that matter. Go to any synchrotron center if you don't believe me. What you are claiming is inconsistent with experimental practices and evidence

Are these the same photoemission experiments conducted by Einstein , are any of them online , I would appreciate a reference if they are. But to come back to the question at hand . Would the experiments give strange results ? Take your example of optical conductivity experiments. Till quite recently the explanation given for the transmission of light through substances like glass did not depend upon photons at all , in fact photons hardly came into it. The explanation was ( and still is ?) as follows: “The distortion of the electron cloud of an atom by an electric field , in this case the electric field of the light, is described as polarization. As a result of polarization, some of the energy may be absorbed, i.e., converted into elastic deformations (phonons), and consequently heat. On the other hand, the polarization may propagate as a material-bound electromagnetic wave with a different speed than light. As you can see there is no reference to photons although phonons are mentioned with regard to the conduction of heat. Take electricity as another example , electrical motors were being designed since Faraday’s time , which worked perfectly well , although in actual fact over the course of the next 150 years , the theory of electricity underwent many changes . What is relevant is not whether those changes were for the better ( of course they were ) but the fact that many experiments worked even without these changes and were at the time thought to be the genuine explanation for these phenomenon . They were only improved upon because of an openness to consider alternative theories. What about gravity , think of catapulting the Voyager spacecraft around the planets to distances of billions of miles, without having any idea as to what it is. We might know how gravity works but we don’t know ( for certain) what it is , or why it works in the way it does. So faced with theories such as the disembodiment of sub-atomic particles as for instance with neutrons having definite size and mass , so that they can in two places at once , or FTL communication , both of which explanations are offered as a reason for the results of the Double Slit Experiment with single particles , is it not possible or even plausible to at least examine alternate explanations. Especially when , as I had pointed out , the whole of these theories stem from the properties of the photon which can be both wave like and particle like. What if the photon is not a particle or a wave but something totally different ? It would no longer make sense to attribute these properties to other sub-atomic particles , because then the photon would have nothing in common with these particles.

 

[inha]

What if the photon is not a particle or a wave but something totally different ?

But it already is something totally different. It's not a particle nor is it a wave but a photon. Using the photon picture one can calculate both XRD spectra and IXS spectra that agree with experiments. Wouldn't that be quite a feat for photons if they didn't even exist?

 

[ZapperZ]

Are these the same photoemission experiments conducted by Einstein , are any of them online , I would appreciate a reference if they are. But to come back to the question at hand . Would the experiments give strange results ? Take your example of optical conductivity experiments. Till quite recently the explanation given for the transmission of light through substances like glass did not depend upon photons at all , in fact photons hardly came into it. The explanation was ( and still is ?) as follows: “The distortion of the electron cloud of an atom by an electric field , in this case the electric field of the light, is described as polarization. As a result of polarization, some of the energy may be absorbed, i.e., converted into elastic deformations (phonons), and consequently heat. On the other hand, the polarization may propagate as a material-bound electromagnetic wave with a different speed than light. As you can see there is no reference to photons although phonons are mentioned with regard to the conduction of heat. Take electricity as another example , electrical motors were being designed since Faraday’s time , which worked perfectly well , although in actual fact over the course of the next 150 years , the theory of electricity underwent many changes . What is relevant is not whether those changes were for the better ( of course they were ) but the fact that many experiments worked even without these changes and were at the time thought to be the genuine explanation for these phenomenon . They were only improved upon because of an openness to consider alternative theories. What about gravity , think of catapulting the Voyager spacecraft around the planets to distances of billions of miles, without having any idea as to what it is. We might know how gravity works but we don’t know ( for certain) what it is , or why it works in the way it does. So faced with theories such as the disembodiment of sub-atomic particles as for instance with neutrons having definite size and mass , so that they can in two places at once , or FTL communication , both of which explanations are offered as a reason for the results of the Double Slit Experiment with single particles , is it not possible or even plausible to at least examine alternate explanations. Especially when , as I had pointed out , the whole of these theories stem from the properties of the photon which can be both wave like and particle like. What if the photon is not a particle or a wave but something totally different ? It would no longer make sense to attribute these properties to other sub-atomic particles , because then the photon would have nothing in common with these particles.

Einstein's "photoelectric effect" model is PRIMITIVE. I have given several citation of a review of photoemission experiments, especially angle-resolved photoemission on high-Tc superconductors. ARPES, resonant photoemission, x-ray photoemission, etc.. are all techniques that were built using the photon picture, NEVER using "wave" picture of light. And when I say that, I am not distinguishing light as "particle" instead of a "wave", because in QM, that dichotomy is meaningless.

I don't think I have the patience to once again describe optical conductivity. I don't have the energy anymore to correct the popular misconception of "electron cloud by atom field" when it comes to solid. Even after saying that bulk property of a solid often has no resemblance to the property of individual atoms, this still doesn't get the message through. And in glass, what "electron cloud" are we talking about? There's no conduction electron. The electron cloud for each of the atom? Then how come I rearrange the atom and get a different property? Or I have light coming in different crystallographic direction and get different transmission? Your classical description is adequate, but it doesn't give the complete picture. Like in any other phenomena, the classical picture starts running into trouble when you try to stretch it into the extreme situation.

One thing Einstein did not see during his life time was the multiphoton photoemission process. Here, the semi-log plot of the photocurrent vs. instensity changes in slope DISCRETELY according to how many photons is required to cause the emission of a single photoelectrons. Again, I have described this phenomenon more than once, especially since I have observed this myself. Now go and explain THAT with your classical picture.

Zz.

 

[McQueen]

One thing Einstein did not see during his life time was the multiphoton photoemission process. Here, the semi-log plot of the photocurrent vs. instensity changes in slope DISCRETELY according to how many photons is required to cause the emission of a single photoelectrons. Again, I have described this phenomenon more than once, especially since I have observed this myself. Now go and explain THAT with your classical picture.

There’s one thing I can’t understand in all this , though the references you had made to multiphoton photoemission do seem to throw some (light) on the subject. Take the reflection of light , when we look out of the window into the garden on a sunny day , we see brilliant colours ( there’s no need at the moment to go into optical conductivity) , and this is the result of the electrons in the objects ( flowers etc., ) that we see outside the window , rapidly absorbing and re-emitting photons of a given energy. This absorption and emission has to take place at a very rapid rate at least at around 10^^-18 secs for each absorption and emission. Given that this is so , could it be that individual electrons are continuously emitting at this rate , for instance if we are dealing with green light at 550 nm. Does it mean that single electrons are emitting at 5.4 x 10^^14 photons per sec. Or is it an intermittent and uncoordinated affair with individual electrons absorbing an electron and then after some time firing off an electron and then going quiescent for some time and then absorbing and emitting another electron. The reason that I said your references throw some light on this subject is because apparently to trigger photo emission at below the threshold through multiple photons requires powerful light sources such as lasers , which shows that it needs a concentration of energy to achieve electron ejection below the threshold level. Am I making any sense or am I talking through my hat.

 

[ZapperZ]

There’s one thing I can’t understand in all this , though the references you had made to multiphoton photoemission do seem to throw some (light) on the subject. Take the reflection of light , when we look out of the window into the garden on a sunny day , we see brilliant colours ( there’s no need at the moment to go into optical conductivity) , and this is the result of the electrons in the objects ( flowers etc., ) that we see outside the window , rapidly absorbing and re-emitting photons of a given energy.

Please justify this description. How do you know this is the valid explanation for what you are describing?

Zz.

 

[alfredblase]

FYI, I stopped seriously reading your article after this introduction. The question has been answered for quite a while now: light is neither a (classical) particle nor a (classical) wave. Light is some quantum mechanical thing to which the classical notions of particles and waves are good approximations under various circumstances.

Oh dear oh dear, even a dunce like me can contradict the best comment in this thread... hehe or maybe I'm wrong. What about the Schrodinger WAVE equation? What about the optical Bloch equations? The former treats light all mathematical objects as waves, and the latter can be used to predict the TRANSITION RATES (classical particle notion if ever I heard one) of atoms in illuminated by laser light. A combination of Schrodinger formalism and notions such as Rabbi FREQUENCY are employed on the way to the optical Bloch equations.

emm maybe I AM a dunce and I'm getting confused by basic stuff, but common.. Schrodinger WAVE equation... its not an approximation is it? hahaha

But I think you have a point. No one REALLY understands QM, its obviously lacking badly as far conceptualising goes, a real failure as far as a physicist is concerned, perhaps not a mathematician though... Light is bound to be something thing other than a particle or a wave...or not hehe ... String Theory might provide a more definate answer in time?...

 

[ZapperZ]

Oh dear oh dear, even a dunce like me can contradict the best comment in this thread... hehe or maybe I'm wrong. What about the Schrodinger WAVE equation? What about the optical Bloch equations? The former treats light all mathematical objects as waves, and the latter can be used to predict the TRANSITION RATES (classical particle notion if ever I heard one) of atoms in illuminated by laser light. A combination of Schrodinger formalism and notions such as Rabbi FREQUENCY are employed on the way to the optical Bloch equations.
emm maybe I AM a dunce and I'm getting confused by basic stuff, but common.. Schrodinger WAVE equation... its not an approximation is it? hahaha
But I think you have a point. No one REALLY understands QM, its obviously lacking badly as far conceptualising goes, a real failure as far as a physicist is concerned, perhaps not a mathematician though... Light is bound to be something thing other than a particle or a wave...or not hehe ... String Theory might provide a more definate answer in time?...

But the SOLUTION to the Schrodinger equation, usually called the "wavefunction", is not a PHYSICAL wave. This is NOT the wave you see or detect! For a system of more than 1 particle, this wavefunction sits in a CONFIGURATION space, not in real space. This wavefunction is also NOT equivalent to the "wave" picture in classical light/EM theory, i.e. it is not the wave equation that you get from Maxwell equations. Don't be mislead by the NAME. Instead, pay attention to the PHYSICS.

And it is silly to say "no one really understand QM", as if we "understand" classical mechanics any better when it fails to describe a whole zoo of phenomena that QM can. Maybe it's our stubborness in trying to FIT nature in the classical picture that is causing all of these weird conceptual problems. You have a square object, and you're trying to force it through a round hole. When you can't get it through, rather than attributing the fact that you're trying to fit an object that isn't meant to go through that hole, you blame the hole!

Zz.

 

[alfredblase]

Ok so QM doesn't consider classical waves, I stand corrected and apologize for displaying my ignorance. :P

But at the risk of displaying it again, like Hurkyl said, "Light is some quantum mechanical thing"... Doesn't sound like he or anyone else understands it, and by understand I mean feel comfortable with the PHYSICS not just the maths. (There is a reason that physics sounds like physical I think). Physics is more than just a bunch of equations, there has to be a conceptual understanding of the problem too. And we can only concieve objects in our head that we are familiar with. By familiar I mean that we may have seen something in everyday physical life that aids our imagination. I mean we need something we can picture or else its just maths. But even the idea of a point it ridiculous, especially if we extend the argument to fundamental particles with mass... infinite density and all that... If there is some one out there who can explain what it is that people who really understand QM picture when they think of light, valid in all circumstances, not just in the classical limit of this, or the classical limit of that, then I will stand corrected on this point too. Thanks ;) I'm sorry but QM is deeply unatractive because it seems like just a bunch of yucky maths. If the general physics community is really ok with that then perhaps we should do away with physics departments altogether and replace them with applied mathematics departments. At least that would make sense. But it would be a shame too. Maths should be a modelling tool to work on problems/objects that we concieve in my oipinion. I mean what is a measured result if not a conception? Maths without conceptions is just counting stars, and saying that you own them. Its accountancy no more. There's no truth or beauty in that.

 

[ZapperZ]

Ok so QM doesn't consider classical waves, fair enough I stand corrected.
But like Hurkyl said, "Light is some quantum mechanical thing"... Doesn't sound like he or anyone else understands it, and by understand I mean feel comfortable with the PHYSICS not just the maths. Physics is more than just a bunch of equations, there has to be a conceptual understanding of the problem too. And we can only concieve objects in our head that we are familiar with. By familiar I mean, a fuzzy point or a wave, I mean we need something we can picture or else its just maths. If there is some one out there who can explain what it is that people who really understand QM picture when they think of light, valid in all circumstances, not just in the classical limit of this, or the classical limit of that, then I will stand corrected on this point too. Thanks ;)

But I'm sure Hurkyl, or anyone else, would not want to write the whole book on QED on here! I certainly don't! It is silly to explain light in the intimate details of QED when the basic QM knowledge here is still shaky.

And I question the approach to QM using "conceptual understanding". There's nothing a priori to indicate everyone has the ability to have a "conceptual understanding" of QM, especially when most people are trying to forcebly impose CLASSICAL understanding into a realm in which such a thing may not be applicable. I find that highly illogical. I have already argued several times on why "QM is so difficult" to understand if one doesn't make any connection to the mathematics.

Zz.

 

[alfredblase]

so you are saying the Standard Model approach is to find some equations that fit the results, THEN try to work out the objects described by the maths. And then there is the further complication that the objects the maths, or even the maths alone may be too complicated for you.

Ok consider instead the way string theory is approached by a student of the subject. The idea of objects as open or closed strings, or membranes is presented. Then the idea of compact dimension is presented. All not too difficult to visualize. THEN you begin to tackle the maths of object actions, interactions and blah blah blah. I prefer that by a long way, don't you? And even though string theory may never be proven, who knows, I'd still be willing to risk spending four or five years undertaking a doctorate in that area rather than on the generaly accepted Standard Model, because I like the idea, the concept, its there its available to the begginer, to the general public even. That is important in physics. Its no use if only a select few can really concieve the objects, who knows maybe they don't and they just pretend to! hehe

 

[ZapperZ]

so you are saying the Standard Model approach is to find some equations that fit the results, THEN try to work out the objects described by the maths. And then there is the further complication that the objects the maths, or even the maths alone may be too complicated for you.
Ok consider instead the way string theory is approached by a student of the subject. The idea of objects as open or closed strings, or membranes is presented. Then the idea of compact dimension is presented. All not too difficult to visualize. THEN you begin to tackle the maths of object actions, interactions and blah blah blah. I prefer that by a long way, don't you? And even though string theory may never be proven, who knows, I'd still be willing to risk spending four or five years undertaking a doctorate in that area rather than on the generaly accepted Standard Model, because I like the idea, the concept, its there its available to the begginer, to the general public even. That is important in physics. Its no use if only a select few can really concieve the objects, who knows maybe they don't and they just pretend to! hehe

Please don't equate what I said with what is going in String Theory. I place a lot of emphasis on experimental observations, being an experimentalist. If you have been in the forum, you would have seen my objection and discomfort to that branch of physics.

If you wish, you may either read my take on this in my journal, or go to physicspost.com.

Zz.

 

[alfredblase]

Would it be right to say that a Quantum Mechanical object, be it light or any other, is a point particle, with a time dependant probablity distribution for its position, energy, interaction with other objects, and so on and so forth? If that's true it doesn't seem too hard to visualise...

 

[McQueen]

Please justify this description. How do you know this is the valid explanation for what you are describing?

The quote above referred to my statement that when we look out of a window on a sunny day , we see brilliant colours , and this is the result of the electrons in the objects ( flowers etc., ) that we see outside the window , rapidly absorbing and re-emitting photons of a given energy. This absorption and emission has to take place at a very rapid rate at least at around 10^^-18 secs for each absorption and emission.
The reference is one of your posts :
https://www.physicsforums.com/showthread.php?t=99218 [/URL]
[QUOTE=ZapperZ]“When light hits a metallic surface, the conduction electrons actualy ABSORBS the photons, causing a transition from one conduction band to another (there's a whole spiel here that I'm skipping about the transition is actually between two points between two different band separated by a reciprocal lattice vector). But this doesn't last and the conduction electrons will drop back to the original band and re-emit this photon,”
and “So if one prefers, the light being reflected is not the same light that was incident onto the mirror.” [/QUOTE]
So the question I really wanted answered was do these electrons [I] continuously [/I] absorb and emit photons at the frequency of the particular light they are being radiated with , as an example I had given green light at 550 nm and a frequency of 5.4 x 10 ^^ 14 Hz. The reason for my making this statement is that if we turn our attention away from the garden and to the window pane through which we are looking , we find that it takes about 10 ^^- 18 seconds for each absorption and emission to take place , based approx. on the number of atoms in the glass which the photon has to traverse , the speed of light through glass etc., Taking into consideration Fermat’s Law which states that light will take the shortest route through the glass , it seems likely that the same electrons are involved and are continuously absorbing and emitting photons at something like the rate of frequency of the light which they are transmitting. The thing is even if you stand looking out of the window for a couple of hours , the process doesn’t stop. Is it a [I] continuous [/i] emission and absorption process on the part of the electrons ? Or do individaul electrons absorb a photon , hang around for a while then re-mit it?

 

[ZapperZ]

The quote above referred to my statement that when we look out of a window on a sunny day , we see brilliant colours , and this is the result of the electrons in the objects ( flowers etc., ) that we see outside the window , rapidly absorbing and re-emitting photons of a given energy. This absorption and emission has to take place at a very rapid rate at least at around 10^^-18 secs for each absorption and emission.
The reference is one of your posts :
https://www.physicsforums.com/showthread.php?t=99218 [/URL]
So the question I really wanted answered was do these electrons [I] continuously [/I] absorb and emit photons at the frequency of the particular light they are being radiated with , as an example I had given green light at 550 nm and a frequency of 5.4 x 10 ^^ 14 Hz. The reason for my making this statement is that if we turn our attention away from the garden and to the window pane through which we are looking , we find that it takes about 10 ^^- 18 seconds for each absorption and emission to take place , based approx. on the number of atoms in the glass which the photon has to traverse , the speed of light through glass etc., Taking into consideration Fermat’s Law which states that light will take the shortest route through the glass , it seems likely that the same electrons are involved and are continuously absorbing and emitting photons at something like the rate of frequency of the light which they are transmitting. The thing is even if you stand looking out of the window for a couple of hours , the process doesn’t stop. Is it a [I] continuous [/i] emission and absorption process on the part of the electrons ? Or do individaul electrons absorb a photon , hang around for a while then re-mit it?[/QUOTE]

Read CAREFULLY what you quoted me, and what you are citing as an example. "Garden" and "window panes" have NO CONDUCTION ELECTRONS!

The optical properties of INSULATORS can be very different than the optical properties of METALS! Thus, when you go on and on with the electron transition and stuff but talking about colors reflecting off your garden, my question would be: you have metallic plants??!

Zz.