Why do we need a photon to mediate the electromagnetic force?

[LorentzR]

A simple question but one I personnaly find difficult.

Why do we need a photon to mediate the electromagnetic force?

 

[chroot]

Because mediating it with pasta would seem awkward?

- Warren

 

[Reshma]

Because mediating it with pasta would seem awkward?

- Warren

That was a good one!

 

[LorentzR]

Because mediating it with pasta would seem awkward?

- Warren

I thought frogs might have been more appropriate. At least they make quantum leaps.

 

[LorentzR]

My reason for asking this question was that four fold manifolds seem to come in two varieties.

Riemann and Pseudo-Riemann

The observed properties of light gives contradictory characteristics for Riemann geometry.

And the photon seems an unnecessary requirement in pseudo-Riemann geometry.

It just seems an idea founded historical convenience?

Pasta would do the job equally well and a least spaghetti is consistent with string theory.

 

[Milind_shyani]

My reason for asking this question was that four fold manifolds seem to come in two varieties.

Riemann and Pseudo-Riemann

The observed properties of light gives contradictory characteristics for Riemann geometry.

And the photon seems an unnecessary requirement in pseudo-Riemann geometry.

It just seems an idea founded historical convenience?

Pasta would do the job equally well and a least spaghetti is consistent with string theory.

Welcome to the forums
Now i don't know whether you are talking about topological manifold or a smooth manifold. But see photon is an elementary particle now the definition itself says that it is elementary.
Now if we put your logic in physics than there would be various discrepancies.for eg graviton is a virtual paritcle than what's the use of having it and so on...
I hope that i have not misunderstood your queation.

 

[LorentzR]

Welcome to the forums
Now i don't know whether you are talking about topological manifold or a smooth manifold. But see photon is an elementary particle now the definition itself says that it is elementary.
Now if we put your logic in physics than there would be various discrepancies.for eg graviton is a virtual paritcle than what's the use of having it and so on...
I hope that i have not misunderstood your queation.

I’m particular interested in the Pseudo-Riemann manifold where the contracted Riemann-Christoffel tensor vanishes. This is the event arena of general relativity where the geometry is locally modeled on the Minkowski metric.

Accepting the validity of relativity then a four-fold Riemann space-time must be rejected as the event arena for the physical world. We are left with the Pseudo-Riemannian Space-time.

My question is how does the photon (and the graviton) fit into such an event arena.

My feeling is, historically, these particles were initially invented to explain action at distance at a time when the geometry world was falsely thought to be Riemannian in nature. Riemannian Geometry being locally modeled on Euclid.

 

[Mentz114]

Why do we need a photon to mediate the electromagnetic force?
...And the photon seems an unnecessary requirement in pseudo-Riemann geometry.
It just seems an idea founded historical convenience?

Only if you quantise the EM field do you need a mediating boson. The photon is not a requirement in classical electrodynamics.

In which case spaghetti hoops are probably most appropriate.

 

[LorentzR]

Only if you quantise the EM field do you need a mediating boson. The photon is not a requirement in classical electrodynamics.

In which case spaghetti hoops are probably most appropriate.

I don’t think you have any choice in the matter; classical electrodynamics cannot describe the behaviour of the atom.

You are not addressing my question of; why the mediator of electromagnetism should have an existence independent of other quantum mechanical systems?

 

[Mentz114]

You are not addressing my question of; why the mediator of electromagnetism should have an existence independent of other quantum mechanical systems?

I don't understand. There is a debate about whether photons exist in the way other fundamental particles do. Some people will say they don't exist at all. It is a somewhat fuzzy area.

Nobody really knows 'why' anything is the way it is.

 

[ZapperZ]

I don’t think you have any choice in the matter; classical electrodynamics cannot describe the behaviour of the atom.

You are not addressing my question of; why the mediator of electromagnetism should have an existence independent of other quantum mechanical systems?

This is a very strange question. It's like asking "why does an object needs a force to make it move or accelerate?".

In QFT, you START with such field, the same way you make those 3 Newton Laws of motion. From there, you verify that they are correct based on observation.

Now as for having "an existence independent of other quantum mechanical systems", I have no idea what you mean by this considering that the quantum field is a "quantum mechanical system".

Zz.

 

[LorentzR]

This is a very strange question. It's like asking "why does an object needs a force to make it move or accelerate?".
Zz.

In general relativity there is no gravitational force, objects just follow geodesic paths through pseudo Riemannian space-time.

In QFT, you START with such field, the same way you make those 3 Newton Laws of motion. From there, you verify that they are correct based on observation.Zz.

Newton’s laws of motion are a set of rules used as the basis of a methodology which we use to make predictions about the motion of objects relative to a given reference system.(Given the ability to measure the location of objects relative to the reference grid). What underlies the nature of a force is unknown.

In quantum mechanics the methodology is modified by the Born rule so that the probable outcomes (observable macroscopic effects) of experimental set-ups involving quantum entities can be predicted.

Now as for having "an existence independent of other quantum mechanical systems", I have no idea what you mean by this considering that the quantum field is a "quantum mechanical system".

Zz.

Again the concept of a quantum field is an object used in our methodology, whether or not it has any physical reality is unknown and the assumption that it is a quantum mechanical system is perhaps premature.

 

[Anonym]

In general relativity there is no gravitational force, objects just follow geodesic paths through pseudo Riemannian space-time.

Newton’s laws of motion are a set of rules used as the basis of a methodology which we use to make predictions about the motion of objects relative to a given reference system.(Given the ability to measure the location of objects relative to the reference grid). What underlies the nature of a force is unknown.

In quantum mechanics the methodology is modified by the Born rule so that the probable outcomes (observable macroscopic effects) of experimental set-ups involving quantum entities can be predicted.

Again the concept of a quantum field is an object used in our methodology, whether or not it has any physical reality is unknown and the assumption that it is a quantum mechanical system is perhaps premature.

I know of a theorist here in our division that said the same thing about OTHER theorists (argue with the experimentalist is waste of time).

I don’t know whether LorentzR is theorist but he is mentally prepared to work in QG or to discuss interpretations.

Regards, Dany.

 

[ZapperZ]

In general relativity there is no gravitational force, objects just follow geodesic paths through pseudo Riemannian space-time.

So? Isn't it the same thing with QFT? You replace the classical "field" with a quantum "field". Same thing! Now you no longer have "forces", but rather an interaction via the exchange of a carrier.

Newton’s laws of motion are a set of rules used as the basis of a methodology which we use to make predictions about the motion of objects relative to a given reference system.(Given the ability to measure the location of objects relative to the reference grid). What underlies the nature of a force is unknown.

In quantum mechanics the methodology is modified by the Born rule so that the probable outcomes (observable macroscopic effects) of experimental set-ups involving quantum entities can be predicted.

You are not making your case any better here. It seems that you are equating the two, which then begs the question on why you haven't started another thread titled "Why the Force?".

Again the concept of a quantum field is an object used in our methodology, whether or not it has any physical reality is unknown and the assumption that it is a quantum mechanical system is perhaps premature.

It HAS a physical reality - the experimental observations (and there's tons of them) indicate that to be so. Why are people ignoring that fact? Is empirical observation THAT despised and irrelevant?

Zz.

 

[Anonym]

It HAS a physical reality - the experimental observations (and there's tons of them) indicate that to be so. Why are people ignoring that fact?

Zz, come on! Not everyone that visits PF is a physicist.

 

[ZapperZ]

Zz, come on! Not everyone that visits PF is a physicist.

What? Not being a physicist gives one the permission to ignore experimental observations? Can you dumb down the rules a little bit more here so that we can move this over to the philosophy forum?

Zz.

 

[Anonym]

Can you dumb down the rules a little bit more here so that we can move this over to the philosophy forum?

No. I think the rules are fine, just what they are supposed to be. It should be some kind of the dynamical equilibrium, otherwise or we move over to the philosophy forum or will remain alone.

I think peoples are not in general ignoring the experiment, they don’t know that it exists and substitute the objective knowledge by subjective imagination. In addition, we have the moderators which are the control feedback loop to maintain the system alive.

Regards, Dany.

 

[ZapperZ]

No. I think the rules are fine, just what they are supposed to be. It should be some kind of the dynamical equilibrium, otherwise or we move over to the philosophy forum or will remain alone.

I think peoples are not in general ignoring the experiment, they don’t know that it exists and substitute the objective knowledge by subjective imagination. In addition, we have the moderators which are the control feedback loop to maintain the system alive.

But was exactly what I was doing, as a Moderator - pointing out experimental evidence that has been ignored in all of this. You somehow think that not being a physicist is a valid excuse for not considering it. I don't buy that.

The whole existence of PF that distinguishes it from the gazillion other physics forums IS the higher standards and quality that we asked for in these discussions. Pointing out the obvious omission of experimental observations, in my book, is crucial because it is what distinguishes physics from philosophy. For some odd reason, you are allowing and even excusing such an omission

Zz.

 

[Anonym]

But was exactly what I was doing, as a Moderator - pointing out experimental evidence that has been ignored in all of this. You somehow think that not being a physicist is a valid excuse for not considering it. I don't buy that.

The whole existence of PF that distinguishes it from the gazillion other physics forums IS the higher standards and quality that we asked for in these discussions. Pointing out the obvious omission of experimental observations, in my look, is crucial because it is what distinguishes physics from philosophy.

I agree with everything you wrote (here).

For some odd reason, you are allowing and even excusing such an omission

I also accept the existing reality.

Regards, Dany.

 

[LorentzR]

It HAS a physical reality - the experimental observations (and there's tons of them) indicate that to be so. Why are people ignoring that fact? Is empirical observation THAT despised and irrelevant?

Zz.

Pardon my scepticism but I find it difficult to visualise any experiment that can prove the existence of the photon. My understanding is that to gain any empirical information regarding the nature of the quantum world , you must first have any experimental set up which has some form of detector that will macroscopically respond (to be observable) to microscopic events in some meaningful way that will tell us something about the state of a quantum system (observables). Exactly what is happening at a microscopic level is open to conjecture, but no one can say for certain what determines the outcome of any experimental procedure.

Quantum mechanics will predict with “100%” accuracy the probable outcomes of an experimental setup but tells us nothing about what is happening within the experimental set-up prior to the macroscopic response.

Empirical observation, is vitally important since it informs us of the macroscopic behaviour of the physical world and gives us the information to confidently make predictions that will help us control our environment and ultimately improve the lot of humanity.

It is the misinterpretation of the observations or the assumption of certainty about unproven theory that is despised and irrelevant!

 

[ZapperZ]

Pardon my scepticism but I find it difficult to visualise any experiment that can prove the existence of the photon.

Actually, you have a twisted way of understand what science does, especially physics. You don't prove anything in physics. There are no proofs for Newton's laws, or anything that you have accepted. There are a SET of experimental observations that are consistent with a theoretical description. That's it! This then allows us to make a conclusion that that theoretical description WORKS and is valid within the range that we know of. It is why we can tell your electronics will work! I hate to blow your bubble, but you have had a faulty understanding of how science works.

If you think that there's another theoretical explanation for the which-way experiment and the photon anti-bunching experiment other than using the photon picture, I'd like to hear it. Till then, this is all just empty speculation.

Zz.

 

[LorentzR]

Actually, you have a twisted way of understand what science does, especially physics. You don't prove anything in physics. There are no proofs for Newton's laws, or anything that you have accepted. There are a SET of experimental observations that are consistent with a theoretical description. That's it! This then allows us to make a conclusion that that theoretical description WORKS and is valid within the range that we know of. It is why we can tell your electronics will work! I hate to blow your bubble, but you have had a faulty understanding of how science works.

If you think that there's another theoretical explanation for the which-way experiment and the photon anti-bunching experiment other than using the photon picture, I'd like to hear it. Till then, this is all just empty speculation.

Zz.

You were the one that said the "photon HAS a physical reality."

I was just pointing out you can't prove that. I think your above comments suggest you would not normally have made such bold statement.

In fact the experimental results show the photon is required to have contradictory physical properties. The normal process of logic would reject the concept. This suggests we should be looking for some other explanation, one which is self consistent.

The current conventional wisdom regarding the propagation of electromagnetism is unsatifactory, leads to fanciful add ons like guide waves or multiple worlds in an effort to achieve a fully reduced theory.

I can't see that reasoning that current wisdom is probably incorrect or a least incomplete necessarily constitutes empty speculation about possible alternatives.

In the absence of a reduced theory we have to make do and mend with the next best thing

 

[ZapperZ]

You were the one that said the "photon HAS a physical reality."

I was just pointing out you can't prove that. I think your above comments suggest you would not normally have made such bold statement.

But I QUALIFY by what I mean by that! I just didn't throw it out without explanation.

You, on the other hand, made no definition of what you mean by "physical reality". Why? Do you not think that using an example of what you consider to have a "physical reality" would be useful? Or do you think that when you make such an illustration, it could easily be shot down?

Zz.

 

[Reshma]

LorentzR,

I think you might want to read this thead:
https://www.physicsforums.com/showthread.php?t=155091

 

[LorentzR]

But I QUALIFY by what I mean by that! I just didn't throw it out without explanation.

You, on the other hand, made no definition of what you mean by "physical reality". Why? Do you not think that using an example of what you consider to have a "physical reality" would be useful? Or do you think that when you make such an illustration, it could easily be shot down?

Zz.

I suppose by physical reality I mean the object possesses states separate from and independent of the measurement process.

Empirical data clearly is dependent on the measuring process. And quantum mechanics is designed to predict the probable outcomes of the measurement process for a given experimental set-up. Quantum mechanics is not a complete reductionistic theory so there is no fully deterministic linkage between the outcome of the experiment and the quantum processes determining the outcome of the experiment.

If a reductionistic theory is possible and that theory included the photon as one of its elements then balance of probabilities would swing towards the photon having physical reality.

In the meantime we have a working methodology that makes no attempt to indicate whether its elements possesses physical reality; and to date attempts to create a reductionistic theory has demanded the elementary components of our theory to have contradictory characteristics.

 

[LorentzR]

LorentzR,

I think you might want to read this thead:
https://www.physicsforums.com/showthread.php?t=155091

Thanks I'll check it out.

 

[ZapperZ]

I suppose by physical reality I mean the object possesses states separate from and independent of the measurement process.

Empirical data clearly is dependent on the measuring process. And quantum mechanics is designed to predict the probable outcomes of the measurement process for a given experimental set-up. Quantum mechanics is not a complete reductionistic theory so there is no fully deterministic linkage between the outcome of the experiment and the quantum processes determining the outcome of the experiment.

If a reductionistic theory is possible and that theory included the photon as one of its elements then balance of probabilities would swing towards the photon having physical reality.

In the meantime we have a working methodology that makes no attempt to indicate whether its elements possesses physical reality; and to date attempts to create a reductionistic theory has demanded the elementary components of our theory to have contradictory characteristics.

Then you do not have a problem with "the photon", but rather with quantum mechanics, the most successful theory every produced in all of human civilization to date. You have a problem with the electrons, protons, neutrons, modern electronics, MRI, etc... etc..., not just "the photon".

Zz.

 

[LorentzR]

Then you do not have a problem with "the photon", but rather with quantum mechanics, the most successful theory every produced in all of human civilization to date. You have a problem with the electrons, protons, neutrons, modern electronics, MRI, etc... etc..., not just "the photon".

Zz.

I don’t have a problem with quantum mechanics since it is only concerned with the observable outcome of experimental situations.

But I do have a problem with the attribution of physical states to the above list of quantum objects which is separate and independent from the observable macroscopic response of the detectors in the experiment; which is fundamentally different issue to the validity of quantum mechanics.

 

[ZapperZ]

I don’t have a problem with quantum mechanics since it is only concerned with the observable outcome of experimental situations.

But I do have a problem with the attribution of physical states to the above list of quantum objects which is separate and independent from the observable macroscopic response of the detectors in the experiment; which is fundamentally different issue to the validity of quantum mechanics.

No, it isn't. That's the whole issue behind EPR-type experiments! You are arguing about what Bell identified as "realism". It has nothing to do with those particles, but rather with how QM describes those particles. You are also mixing your "personal tastes" into this, which has never been a valid argument against anything in physics. It is why I asked for experimental observations in the very first place. If not, we might as well argue about our favorite colors.

Zz.

 

[Cane_Toad]

But I do have a problem with the attribution of physical states to the above list of quantum objects which is separate and independent from the observable macroscopic response of the detectors in the experiment; which is fundamentally different issue to the validity of quantum mechanics.

What are you saying about the relationship of physical to quantum? They do have a loose relationship in that one models the other.

I don't understand how the quantum object is "separate and independent" from observable results. The quantum object predicts the results, although this doesn't imply unity between object and result.

 

[Cane_Toad]

No, it isn't. That's the whole issue behind EPR-type experiments! You are arguing about what Bell identified as "realism".
Zz.

Please explain which issue you are talking about from EPR, and which of his statements this is applying to. I'm getting lost in the referents.

 

[Fra]

I apologize for entering the thread so late, I don't mean to comment on the previous discussions, just comment this line...

I suppose by physical reality I mean the object possesses states separate from and independent of the measurement process.

What would you say is the difference between a measurement process and interaction process in general? Aren't measurements effectively an interaction where the outcome yields new information? Human measurements are specially designed and controlled interactions. But hardly of any other principal "nature" than say two particles interacting? Or, what would the pricipal difference be?

Assuming the idea of symmetry between observation and interaction, the idea of reality beeing independent from measurements seems to suggest that this reality would be in a different universe, since it is also independent of interactions? Which would suggest that this type of reality have no connection to the universe we live in?

IMO, something that lives it's own life, independent of interactions with me(x) lacks justification for me(x). My personal thinking is that the qualifying justifications is the interactions, because what else is there? This is still a little fuzzy, but I'm not sure how much clearer it'll get.

/Fredrik

 

[reilly]

LorentzR --You would do well to study Mandel and Wolf's Optical Coherence and Quantum Optics.Virtually anything you want to know about photons is covered. Photons are old hat because they are an extremely useful and powerful concept; really no different from the concept of time, or force, or... We and our ancestors made all this stuff up; ZapperZ is dead on target about proofs and physics.

How would you design an experiment to determine the reality of a photon?
Regards,
Reilly Atkinson

 

[LorentzR]

No, it isn't.
Zz.

Sorry I can’t agree.

The evidence for the validity of quantum mechanics comes from the comparison between what quantum mechanics predicts and the actual observed outcome of the experiments. Whether or not the quantum objects whose states are described by quantum mechanics actually have an independent physical reality is completely irrelevant to the validation process.

That's the whole issue behind EPR-type experiments! You are arguing about what Bell identified as "realism". It has nothing to do with those particles, but rather with how QM describes those particles. You are also mixing your "personal tastes" into this, which has never been a valid argument against anything in physics. It is why I asked for experimental observations in the very first place. If not, we might as well argue about our favorite colors.

Zz.

I suppose I am bringing my personal taste into my argument. My personal taste is to try not to be seduced by the experimental results into thinking what I’m seeing is evidence of the physical reality of quantum objects. I have to remember we do not have,as yet, a complete logical sequence that links the response of a detector in an experiment to the physical reality of quantum entities that are supposed to be under investigation.

 

[LorentzR]

LorentzR --You would do well to study Mandel and Wolf's Optical Coherence and Quantum Optics.Virtually anything you want to know about photons is covered. Photons are old hat because they are an extremely useful and powerful concept; really no different from the concept of time, or force, or... We and our ancestors made all this stuff up; ZapperZ is dead on target about proofs and physics.

I absolutely agree with ZapperZ's comments on proofs and physics. But his assertion that the Photon has a physical reality is inconsistent with his comments on proofs.

How would you design an experiment to determine the reality of a photon?
Regards,
Reilly Atkinson

I would think with great difficulty.

A reductionistic theory in which the photon is required to have physical reality would throw the balance of probabilities towards realism. As you say its all made up stuff and does not completely hold together.

 

[LorentzR]

I apologize for entering the thread so late, I don't mean to comment on the previous discussions, just comment this line...
What would you say is the difference between a measurement process and interaction process in general? Aren't measurements effectively an interaction where the outcome yields new information? Human measurements are specially designed and controlled interactions. But hardly of any other principal "nature" than say two particles interacting? Or, what would the pricipal difference be?

Assuming the idea of symmetry between observation and interaction, the idea of reality beeing independent from measurements seems to suggest that this reality would be in a different universe, since it is also independent of interactions? Which would suggest that this type of reality have no connection to the universe we live in?

IMO, something that lives it's own life, independent of interactions with me(x) lacks justification for me(x). My personal thinking is that the qualifying justifications is the interactions, because what else is there? This is still a little fuzzy, but I'm not sure how much clearer it'll get.

/Fredrik

I suspect that quantum systems continuously interact with the rest of the universe and are fully connected to the universe we live in.

In order for an observation to be made the effect of an interaction must be amplified into a detectable event. Then there must be somebody there to observer the event.

For a “particle” to have physical reality it must have a universe to interact with and be able to reference the magnitude of its physical states.

 

[LorentzR]

What are you saying about the relationship of physical to quantum? They do have a loose relationship in that one models the other.

We do not have a wholly reductionistic theory modelling one with the other. We depend on the Born rule for quantum mechaics to work.

I don't understand how the quantum object is "separate and independent" from observable results. The quantum object predicts the results, although this doesn't imply unity between object and result.

Quantum mechanics predicts the results.

 

[XVX]

I’m particular interested in the Pseudo-Riemann manifold where the contracted Riemann-Christoffel tensor vanishes. This is the event arena of general relativity where the geometry is locally modeled on the Minkowski metric.

Accepting the validity of relativity then a four-fold Riemann space-time must be rejected as the event arena for the physical world. We are left with the Pseudo-Riemannian Space-time.

My question is how does the photon (and the graviton) fit into such an event arena.

My feeling is, historically, these particles were initially invented to explain action at distance at a time when the geometry world was falsely thought to be Riemannian in nature. Riemannian Geometry being locally modeled on Euclid.

There is no metric for the Universe. And certainly, the perihelion of Mercury was not calculated with the Minkowski metric. And unquestionably, GPS systems do not use the Minkowski metric. The Minkowski metric is GR’s special case in which one has Newton’s Laws and a finite speed limit theory that is commonly known as, SR.


But why photons?

Why does matter choose energy in packets?

When EM waves are incident upon Hydrogen, is there some mechanism in Hydrogen that says, “we will wait a time ‘t’ dependent upon wave amplitude, to collect ‘E’ energy and then decide what to do with it.”?

Or does energy come in packets?

I picture particles like billiard balls surround by a potential barrier. When a photon hits Hydrogen, the photon can either, get over the barrier and be absorbed into the center or there is just a collision with the outer barriers. An EM wave of high energy, but low frequency has a bunch of balls, but individually, they are weak and none can penetrate the absorption barrier. These are photons. These are the packets of energy that bombard a target. The target is not bombarded by some solid piece of energy that the target chooses whether to take a bite out of or not and how big the bite should be. I see no contradictions with the photon, GR and Minkowski space.

QM showed this interaction with matter and quantized energy and QED was just the next step in saying, well, if EM waves are made of photons, then what about the rest of E&M? And QED has been tremendously successful, although, its greatest triumph of the anomalous magnetic dipole moment of the electron is not nearly as good for the muon.

And trying the same strategy to understand gravity in a similar way and make us believe in a graviton has been a failure. While I don’t believe in the graviton, GR reigns supreme here, Einstein was unable to formulate an EM theory with “his” strategy. And QM reigns supreme here.

As of today, IMO, the photon is the explanation for the EM forces and GR is the explanation for the gravitational force.

BTW, one step in disproving the photon would be to give a new model for the photoelectric effect………….just...for starters.

 

[Anonym]

And unquestionably, GPS systems do not use the Minkowski metric.

?

To the best of my knowledge, they do. I have no reference handy, but all algorithms (iterations, Kalmans, etc.) are based on the Minkowski interval.

Regards, Dany.

 

[cristo]

?

To the best of my knowledge, they do. I have no reference handy, but all algorithms (iterations, Kalmans, etc.) are based on the Minkowski interval.

Regards, Dany.

GPS systems involve satellites orbitting a massive body (the earth) and thus must use general relativity somewhere. In fact, GPS uses both special and general relativity. Check out this paper for more info: http://relativity.livingreviews.org/Articles/lrr-2003-1/

 

[LorentzR]

There is no metric for the Universe. And certainly, the perihelion of Mercury was not calculated with the Minkowski metric. And unquestionably, GPS systems do not use the Minkowski metric. The Minkowski metric is GR’s special case in which one has Newton’s Laws and a finite speed limit theory that is commonly known as, SR.

.

I was trying to make the distinction between Riemann space and Pseudo Riemann space.

The former is locally modeled on Euclid and the latter, as used in GR, locally modeled on Minkowski.

The metric in a gravitaional field is Schwarzschild's

 

[Anonym]

In fact, GPS uses both special and general relativity.

Thank you. Your statement is obviously correct:

“Hence, the principle of the constancy of c finds application as the fundamental concept on which the GPS is based.

Therefore, to implement Eqs. (1 ), the receiver must generally perform a different rotation for each measurement made, into some common inertial frame, so that Eqs. (1 ) apply.

For the GPS it means that synchronization of the entire system of ground-based and orbiting atomic clocks is performed in the local inertial frame, or ECI coordinate system [6].” Etc.

I refer to XVX:” There is no metric for the Universe. And certainly, the perihelion of Mercury was not calculated with the Minkowski metric. And unquestionably, GPS systems do not use the Minkowski metric. The Minkowski metric is GR’s special case in which one has Newton’s Laws and a finite speed limit theory that is commonly known as, SR.”

I am at holydays now and can’t check about Mercury. I am sure that he is wrong about it too. His statements I consider absurd.

Regards, Dany.

 

[cristo]

I am at holydays now and can’t check about Mercury. I am sure that he is wrong about it too. His statements I consider absurd.

What, particularly, about his statements are absurd? There is no "metric for the universe," since GR is a local theory.

The solution to the precission of the perehilion of Mercury was one of the great successes of GR. This certainly does not use the flat spacetime metric, but instead uses the Schwarzschild metric. You can see this derivation is many GR textbooks if you are not convinced!

 

[Mentz114]

There is a metric for the universe. It's called the Friedman-Lemaitre-Robertson-Walker metric. See any book on cosmology.

 

[Anonym]

There is no "metric for the universe," since GR is a local theory.

Perhaps I did not understand him properly. Tomorrow I will prepare the answer as needed.

Regards, Dany.

 

[lightarrow]

I picture particles like billiard balls surround by a potential barrier. When a photon hits Hydrogen, the photon can either, get over the barrier and be absorbed into the center or there is just a collision with the outer barriers. An EM wave of high energy, but low frequency has a bunch of balls, but individually, they are weak and none can penetrate the absorption barrier. These are photons. These are the packets of energy that bombard a target. The target is not bombarded by some solid piece of energy that the target chooses whether to take a bite out of or not and how big the bite should be. I see no contradictions with the photon, GR and Minkowski space...

So, which are photon's dimensions? If they existed, would they be independent of its energy? If a photon is a particle, how is its wavefunction related with the existence of that particle in a specific point of space? Is the wavefunction THE particle?

I sincerely cannot understand how you can so easily give real existence to mathematical objects.

Yes, QED has been proved up to a very high degree. Does it mean we should believe in the existence of "energy packets" flying from source to detector? Maybe; but maybe someone could, one day, describe the same results with a different theory.

Certainly, it's not the case to reject a theory that works so well! But I'm not saying this. What I mean is that I can't understand how can low energy photons exist from source A to detector B if you cannot detect them (because you destroy them in doing it).

 

[cristo]

There is a metric for the universe. It's called the Friedman-Lemaitre-Robertson-Walker metric. See any book on cosmology.

Of course, the FRW metric is as close to a model of the visible universe that we have. However, my point was that GR is a local theory, with local curvature. For example, the FRW metric would not describe the metric outside, say, a massive star. In retrospect, my point didn't really answetr the question!

Anyway, this has gotten rather off topic-- I've just noticed that this is a thread in the QP forum!

 

[ZapperZ]

So, which are photon's dimensions? If they existed, would they be independent of its energy? If a photon is a particle, how is its wavefunction related with the existence of that particle in a specific point of space? Is the wavefunction THE particle?

I sincerely cannot understand how you can so easily give real existence to mathematical objects.

Can you show me evidence in history where we actually give in THAT easily? May I remind you how much resistance the Einstein's photoelectric effect model had when it was first introduced? Should I point out to you Millikan's highly skeptical paper on it when he set out to literally falsify it? Where is this "easy" part? I want to know!

So you also have issues with the whole of classical E&M? After all, it IS nothing more than a set of "mathematical objects"? I don't see you complaining about this in the classical physics section whenever classical E&M is discussed. The energy band gap in your semiconductor is also a relic of some mathematical objects. Yet, you freely use it in your electronics.

If such a picture doesn't exist, then show me an alternative explanation to the experimental observations that I have mentioned, which, btw, NO ONE has attempted to tackle. Show me a non-photon formulation of the anti-bunching phenomenon and we'll talk. Yet, all we get are nothing more than objections due to a matter of TASTES! This is not physics and this has never been a valid argument against anything in physics.

Zz.

 

[George Jones]

?

To the best of my knowledge, they do. I have no reference handy, but all algorithms (iterations, Kalmans, etc.) are based on the Minkowski interval.

Regards, Dany.

Like cristo, I don't see how GPS calculations can be done solely with the Minkowski metric. Here's a simplified (but still quite accurate) https://www.physicsforums.com/showpost.php?p=731738&postcount=5" that uses the Schwarzschild metric and some Newtonian approximations.

 

[Anonym]

Like cristo, I don't see how GPS calculations can be done solely with the Minkowski metric.

Come on, guys! The original statement was:

And unquestionably, GPS systems do not use the Minkowski metric.

“A man ought to read just as inclination leads him; for what he reads as a task will do him little good." I find it strange that I know to read English better than you!

Thanks for the refs. Few years ago I was involved in the engineering projects connected with GPS.

Regards, Dany.