Merged Relativity+ / Farsight

[edd]

Farsight - you clearly don't like talking about virtual particles. Putting that to one side, do you think the interaction of two photons doesn't involve the fields associated with other particles?

 

[Reality Check]

You know, sometimes I feel like I'm fighting the naysayer cargo-cult ignorance all on my own.

Oh dear, Farsight - the good old logical fallacy of thinking that because I am wrong, you must be right!
You remain wrong:
* Two photon physics: photons cannot couple directly to each other
*

My point was, Farsight "If you could collect all the ash and smoke and weigh it, it would weigh just a little but less than the original coal" was wrong because you forgot about oxygen.

* The screw analogy used by a couple of people does not mean that light is a screw!
* Farsight's imaginary spiral cartoons
* to keep on going on about the invalid Williamson / van der Mark electron model since 25th March 2010!

ETA: You missed out that I agree with the correctly stated situation, i.e. that there is a difference in weight between the beginning and end products a fire due to the emission of light.

It is dumb to call everyone who knows about the valid science and points out that you are wrong about the science a "naysayer cargo-cult" or ignorant. It is simply that people like
* ben m (a professional physicist!)
* W.D.Clinger
* lpetrich
* and even me!
know and understand more science than you. We do not rely on insanely bad cartons !

 

[Reality Check]

Farsight: What is the charge of a photon? What does this mean for Maxwell's equations

...screw delusion snipped...
Displacement current tells you they have direct interactions.
...snipped usual insults....

Displacement current is not about photons interacting.
Maxwell's equations tell us that it is impossible for any uncharged particles to interact. Photons have a charge of zero. So it is impossible for photons to interact at all in classical electrodynamics (Maxwell's equations).

But maybe you do know this physics, Farsight:
What is the charge of a photon?
What does this mean for Maxwell's equations?

QED tells us that photons cannot interact directly (their charge is zero) but that they can interact indirectly.

Duh: the inanity of a Google search should be obvious to you, Farsight .
Try to understand what everyone and the science tells you: Photons cannot interact directly - their charge is zero.
Try to understand what everyone and the science tells you: Photons can interact indirectly through the formation of virtual particles.
So photons can interact and QED even allows us to predict how they interact. It is direct interactions that never happen.

ETA: Emphasized the direct and indirect so that you might understand the difference, Farsight.

 

[Reality Check]

Feynman said nobody understood why it works. It didn't explain anything.

Good old ignorance of what Feynman said .
Feynman said "On the other hand, I think I can safely say that nobody understands quantum mechanics" and that it explains a lot (how electrons and photons behave) .
Introduction to the Quantum Mechanics lecture in The Messenger Lectures, 1964, MIT

...Now we know how the electrons and light behave. But what can I call it?...
On the other hand, I think I can safely say that nobody understands quantum mechanics. So do not take the lecture too seriously, feeling that you really have to understand in terms of some model what I am going to describe, but just relax and enjoy it. I am going to tell you what nature behaves like. If you will simply admit that maybe she does behave like this, you will find her a delightful, entrancing thing. Do not keep saying to yourself, if you can possible avoid it, "But how can it be like that?" because you will get 'down the drain', into a blind alley from which nobody has escaped. Nobody knows how it can be like that.

 

[ben m]

This is a thing of beauty.

As for QED and the Standard Model, the things people say about them will be proved wrong by experiment.

Here Farsight claims to be aware that there's a widely-shared understanding of QED and the Standard Model that disagrees with his own and that he thinks will be overturned ...

I mean, you seriously think a photon spontaneously morphs into an electron-positron pair. Like magic? And that's how pair production works? Because photons don't interact with photons? No, no way can you be a professional physicist.

... and five sentences later, he's forgotten; now he thinks that his version is universally-shared version among physicists, so my disagreement proves that I'm not a physicist. .

Okeydokey!

(ETA: not that I agree with his exact wording. There's no 100%-precise verbal statement of what a virtual particle is. Farsight's statement would be improved by removing the word "spontaneous". A genuinely-uncontroversial statement of what's going on can be found in the QED Lagrangian and the Dirac equation.)

 

[lpetrich]

Well, seeing as you dismissed Maxwell ...

So like a theologian. Treating James Clerk Maxwell as a prophet of inspired truth and claiming that it is a terrible moral evil to deny his words.

... we'll leave his equations out of it.

Farsight, you seem to have the belief that the correctness of Maxwell's equations depend on the authority of JCM himself. It doesn't, and you won't be a good scientist until you recognize that.

Displacement current tells you they have direct interactions.

A rather grossly literal-minded interpretation of a name. Not only like a theologian, but also like a scriptural percussionist.

JCM gave "displacement current" that name for two reasons:
1. It appears alongside the ordinary current in Ampere's circuital law
2. His theory of molecular vortices as the mechanism of electromagnetism

That molecular-vortex theory has had no independent support and is now discarded.

Duh. The experimental data from your photon-photon collider will show you that two photons interact.

1. search-engine result link again
2. Photon-photon collisions do not require photons to directly interact with each other. Instead, they produce virtual charged particles that go between them -- electrons, muons, etc.

But people who don't understand it say it "explains" pair production by saying one of the photons spontaneously morphs into an electron and a positron, to which the other photon couples. That's not an explanation.

Maybe not to you, but it's how one works out the process's behavior.

I tell you what Einstein said or what Minkowski said or what Maxwell said or what Thomson and Tait said.

Thump, thump, thump, thump, thump. I feel like there's a pile driver in action next door.

Hey, let's sit and watch all those photons turning into virtual and real electrons. Which then magically morph back into single photons. Defying conservation of momentum. And then those photons somehow manage to keep on travelling at c. Even though electrons can't.

Being off the mass shell is a feature of virtual particles, and that includes these electrons.
(4-momentum)² != (mass)²
So there's no contradiction. Quantum field theory != classical particle limit.

 

[steenkh]

Feynman said nobody understood why it works. It didn't explain anything.

Did Feynman really say that it did not not explain anything?

And if he did, why is that important to us? Does Feynman's statement mean that he thought QED got it wrong? And if he did, should we then on Feynman's authority conclude that QED is wrong?

 

[ben m]

Displacement current tells you they have direct interactions.

You're better off with vague answers, Farsight. Whenever you get specific you come up with a howler.

I'll explain, primarily for the lurkers, since you are beyond hope.

Displacement current is a feature of Maxwell's Equations. Those equations are linear---identically, perfectly linear by definition. According to Maxwell's Equations, electromagnetic waves are perfectly noninteracting; if you write down the equation describing two incoming E&M waves (i.e., a wave propagating east, aimed at a wave propagating west), Maxwell's Equation predicts zero scattering (no north/south/up/downgoing components will develop) no matter how much power you put into either or both waves.

Sometimes I try to diagnose Farsight's mistakes. "He probably said X because he read Y and pictured Z". This one? Displacement current tells you photons interact directly? No idea. Random neural misfire? Disinformation beamed from the Met office to Farsight's dental fillings? Reading between the lines of a 19th century telegraphy manual? Trolling? No idea. Maybe a bit subtle, but I think it ranks up there with "Worsley units", "you didn't combine the fields", and "LEP is world-class wrong" in revealingness.

Duh. The experimental data from your photon-photon collider will show you that two photons interact.

Exactly what experimental observation at a photon-photon collider will tell the difference between a your model (direct photon-photon interaction) and the Standard Model (i.e., an underlying photon-fermion-fermion interaction leads to photon-photon scattering via the virtual fermions that you so dislike)?

Remember: QED does not say "nothing happens in a photon collider". QED says very precisely what should happen in a photon collider, including the cross sections (full differential, polarized cross sections) for gg->e+e-, gg->mu+mu-, gg->gg, gg->g e+e-, gg->b bar (the latter having a *pretty good* QED prediction but with some QCD corrections), gg->Higgs, (not strictly speaking QED but the same QFT apparatus) etc.. None of this requires "photon photon interactions"; all of these final states come about via virtual charged fermions. Surely you can tell us what is different in the case that photons interact directly. Before doing the math maybe you can draw a Feynman diagram for your version of the nonlinear term---what is it, triple gauge coupling? Quadruple gauge coupling?

 

[ctamblyn]

He said one of the photons becomes a virtual electron and a real electron. You know, via that little thing we call "magic"?

Sorry, I thought you wanted to discuss QED, not the shortcomings of a strawman based on a verbal analogy based on QED. Carry on.

 

[Farsight]

Farsight - you clearly don't like talking about virtual particles.

I don't have a problem talking about virtual particles. I've spoken previously about them, and how they are "field quanta". Like you divide the field up into little chunks, and say each is a virtual particle. I've referred to Matt Strassler's blog: where he says this:

"A virtual particle is not a particle at all. It refers precisely to a disturbance in a field that is not a particle".

I've also referred to the near and far field on wiki where you can read this:

"In the quantum view of electromagnetic interactions, far field effects are manifestations of real photons, while near field effects are due to a mixture of real and virtual photons".

And I've surely referred to evanescent modes are virtual photons. The evanescent wave is a standing electromagnetic wave that isn't going anywhere. You divide it up into little chunks and say each one is a field quantum, a virtual photon. It's a bit like the virtual photons are the accounting units for your calculations. Like pennies are the accounting units of your financial calculations. If you pay a cheque into your bank account, there isn't some hailstorm of real pennies flying into some vault somewhere. In similar vein there aren't any actual photons flying back and forth in a hydrogen atom. And there aren't any actual electrons flying around before gamma-gamma pair production has happened.

Putting that to one side, do you think the interaction of two photons doesn't involve the fields associated with other particles?

No I don't. I think the interaction of two photons involves the fields associated with those photons. They are the only particles that are there. They do not interact because of the electron field. The electron field is the result of their interaction.

 

[Farsight]

Here Farsight claims to be aware that there's a widely-shared understanding of QED and the Standard Model that disagrees with his own and that he thinks will be overturned...

I think there's a widely-shared misunderstanding of QED and the Standard model that will be corrected. Photons interact with photons. Photons couple with photons. Photons couple with themselves. And when they do, the thing you call the photon field becomes the thing you call the electron field.

...so my disagreement proves that I'm not a physicist...

I have doubts about you being a physicist because you know so little physics.

(ETA: not that I agree with his exact wording. There's no 100%-precise verbal statement of what a virtual particle is.

See what I said to edd above. I reckon that comes pretty close.

Farsight's statement would be improved by removing the word "spontaneous". A genuinely-uncontroversial statement of what's going on can be found in the QED Lagrangian and the Dirac equation.)

So spell it out. What's the problem?

 

[Farsight]

You're better off with vague answers, Farsight. Whenever you get specific you come up with a howler.

It's no howler.

Displacement current is a feature of Maxwell's Equations.

You are lost in maths. Displacement current is a feature of light. It's a time-varying electric field. And it does what it says on the can. It isn't called displacement current for nothing.

Those equations are linear---identically, perfectly linear by definition. According to Maxwell's Equations, electromagnetic waves are perfectly noninteracting; if you write down the equation describing two incoming E&M waves (i.e., a wave propagating east, aimed at a wave propagating west), Maxwell's Equation predicts zero scattering (no north/south/up/downgoing components will develop) no matter how much power you put into either or both waves.

Because that displacement current is alternating. That's why we have vacuum impedance, impedance being resistance to alternating current. The two waves "ride over one another", like two ocean waves ride over one another. There's a displacement up, then down. Then each continues on its way. So it looks like there was no interaction. But when you increase the energy the displacement is so drastic that each wave is displaced into itself. And ends up displacing itself into a closed path. Simples.

Sometimes I try to diagnose Farsight's mistakes. "He probably said X because he read Y and pictured Z". This one? Displacement current tells you photons interact directly? No idea. Random neural misfire? Disinformation beamed from the Met office to Farsight's dental fillings? Reading between the lines of a 19th century telegraphy manual? Trolling? No idea. Maybe a bit subtle, but I think it ranks up there with "Worsley units", "you didn't combine the fields", and "LEP is world-class wrong" in revealingness.

I don't make mistakes. You just don't know much physics, that's all. I think it's because your physics degree was all maths. That's the usual thing. People spend three years doing maths, not physics.

Exactly what experimental observation at a photon-photon collider will tell the difference between a your model (direct photon-photon interaction) and the Standard Model...

Huh? It's a photon-photon collider. We collide photons with photons. So then we know that photons interact with photons to create electrons and positrons. Duh!

...fermion-fermion interaction leads to photon-photon scattering via the virtual fermions that you so dislike)? Remember: QED does not say "nothing happens in a photon collider".

Oh shut up peddling cargo-cult trash. You could assert that the photon-photon collider actually works via the interaction of pinhead angels, and I couldn't prove it isn't so. All I can do is point out that it's a photon-photon collider, duh!

QED says very precisely what should happen in a photon collider...

Only if it says pair production occurs because pair production occurs, spontaneously, like worms from mud, it ain't precise enough. Capiche?

 

[Farsight]

Did Feynman really say that it did not not explain anything?

No. He said nobody understood why it works.

And if he did, why is that important to us?

Because I understand why it works.

Does Feynman's statement mean that he thought QED got it wrong?

No. It means he thought QED didn't say enough about the underlying reality

And if he did, should we then on Feynman's authority conclude that QED is wrong?

No. We should conclude from "pair production occurs because pair production occurs" that QED doesn't say enough about the underlying reality. And that some people who say they are physicists don't know much physics.

 

[Ziggurat]

I don't make mistakes. You just don't know much physics, that's all. I think it's because your physics degree was all maths. That's the usual thing. People spend three years doing maths, not physics.

The perpetual complaint of the internet physics crank: not that the math is wrong (because god knows you're not capable of demonstrating that) but that using math is itself the problem. And it's always the result of one (or both) of two things: the crank can't do math, or the math doesn't give the answer they demand.

Huh? It's a photon-photon collider. We collide photons with photons. So then we know that photons interact with photons to create electrons and positrons. Duh!

That doesn't answer the question. If all you see are photons going in and particles coming out, you cannot use this result to distinguish between two models which both predict photons going in and particles coming out but explain those results using different mechanisms.

Oh shut up peddling cargo-cult trash. You could assert that the photon-photon collider actually works via the interaction of pinhead angels, and I couldn't prove it isn't so. All I can do is point out that it's a photon-photon collider, duh!

But the standard model does more than simply predict that an interaction occurs. It predicts QUANTITATIVELY what that interaction will produce. Change the energy of the photons, you'll get a different result. Change the intensity (the number of photons), and you'll get a different result. Now, if someone developed a "pinhead angels" model which ALSO make successful quantitative predictions of these dependencies, then yes, it would be just as valid as the standard model. But you certainly haven't done so, and if you ever managed to, well, that would be worthy of publication. But that's never going to happen, because you won't do the math. And that, per above, tells us everything we need to know about you.

Only if it says pair production occurs because pair production occurs, spontaneously, like worms from mud, it ain't precise enough. Capiche?

Yes, that isn't precise enough. It should also tell you how much pair production occurs under different conditions. Oh, look, the standard model DOES predict that. Does your model? Nope.

The "precision" of your description of the interaction is pointless if it cannot produce precise descriptions of the results.

 

[steenkh]

No. He said nobody understood why it works.

And we have to take for granted?

Because I understand why it works.

So you have a better understanding of QED than Feynman?

No. It means he thought QED didn't say enough about the underlying reality

That is quite an interpretation you have got there. why could it not simply mean that QED is right, but he does not understand it completely?

No. We should conclude from "pair production occurs because pair production occurs" that QED doesn't say enough about the underlying reality. And that some people who say they are physicists don't know much physics.

So on your authority we should go from "pair production occurs because pair production occurs" to "photon interaction occurs because photon interaction occurs"? As Ziggurat has pointed out, real physicists can use standard QED to predict exactly what the interaction will produce, but you have not demonstrated anything similar, so your theory is weaker.

 

[steenkh]

I don't make mistakes. You just don't know much physics, that's all. I think it's because your physics degree was all maths. That's the usual thing. People spend three years doing maths, not physics.

You convince nobody with such statements. First of all, plenty of mistakes have been demonstrated on your part, and you have not once been able to show that maths is leading to a wrong result. In fact, it is obvious that, like me, you have no idea where the maths is leading. What would Einstein have said about math and physics?

 

[Farsight]

The perpetual complaint of the internet physics crank: not that the math is wrong (because god knows you're not capable of demonstrating that) but that using math is itself the problem. And it's always the result of one (or both) of two things: the crank can't do math, or the math doesn't give the answer they demand.

Oh spare me the perpetual ad-hominems of a naysayer who doesn't know any physics. Ben m mistook physics for maths. Displacement current is something real. See for example Taming light at the nanoscale where you can read this:

"Look around, and you will probably see numerous electronic and optical gadgets, such as mobile phones, personal digital assistants, laptops, TVs and digital cameras. These may all do different things but they have one thing in common: in the electronic circuits that drive these devices, charged particles flow through components and impart power via what is known as the conduction current. But is the motion of charged particles the only current we have available?"

That doesn't answer the question. If all you see are photons going in and particles coming out, you cannot use this result to distinguish between two models which both predict photons going in and particles coming out but explain those results using different mechanisms.

Photons go in, electrons and positrons come out. And it's a photon-photon collider. It isn't a photon-angel collider, or a photon-chocolate teapot collider, or a photon-electron collider. It's a photon-photon collider. Is there some part of this you missed?

But the standard model does more than simply predict that an interaction occurs. It predicts QUANTITATIVELY what that interaction will produce. Change the energy of the photons, you'll get a different result. Change the intensity (the number of photons), and you'll get a different result. Now, if someone developed a "pinhead angels" model which ALSO make successful quantitative predictions of these dependencies, then yes, it would be just as valid as the standard model.

So do you see the problem yet? It doesn't offer any QUALITATIVE understanding.

But you certainly haven't done so, and if you ever managed to, well, that would be worthy of publication. But that's never going to happen, because you won't do the math. And that, per above, tells us everything we need to know about you.

No it doesn't. The math is nothing to do with it. What is, is the fact that it's a photon-photon collider.

Yes, that isn't precise enough. It should also tell you how much pair production occurs under different conditions. Oh, look, the standard model DOES predict that. Does your model? Nope. The "precision" of your description of the interaction is pointless if it cannot produce precise descriptions of the results.

I'm just telling you that photons interact with photons mate. No need to start spitting feathers and huffing and puffing with outrage because somebody has the temerity to challenge the cargo-cult nonsense that pair production occurs because pair production occurs.

 

[Farsight]

And we have to take for granted?

Huh?

So you have a better understanding of QED than Feynman?

No. But I do have a better understanding of QED than you. And a better understanding of all aspects of physics. In fact, do you understand any physics at all? No!

That is quite an interpretation you have got there. why could it not simply mean that QED is right, but he does not understand it completely?

That's more or less how it was. Feynman one of my "heroes of physics", and he was known as "the great explainer". But there were some things he couldn't explain.

So on your authority we should go from "pair production occurs because pair production occurs" to "photon interaction occurs because photon interaction occurs"?

No. On your own authority you should reject "pair production occurs because pair production occurs" because it's a nonsensical tautology. Then you're left with "pair production occurs because a photon-photon interaction occurs".

As Ziggurat has pointed out, real physicists can use standard QED to predict exactly what the interaction will produce, but you have not demonstrated anything similar, so your theory is weaker.

I'm not some my-theory guy. I'm telling you that if you've got a photon-photon collider, it's a photon-photon collider, not a photon-electron collider.

You convince nobody with such statements. First of all, plenty of mistakes have been demonstrated on your part...

Oh no they haven't. If they have, give us a list of them. You know you won't.

and you have not once been able to show that maths is leading to a wrong result. In fact, it is obvious that, like me, you have no idea where the maths is leading.

Er, no, it's obvious that you have no idea of either the maths or the physics. And yet you play the naysayer, like some Emperor's New Clothes groupie. A defender of orthodoxy, even when it's patent nonsense. On a crtitical-thinking forum? Bizarre.

 

[DeiRenDopa]

But the standard model does more than simply predict that an interaction occurs. It predicts QUANTITATIVELY what that interaction will produce. Change the energy of the photons, you'll get a different result. Change the intensity (the number of photons), and you'll get a different result. Now, if someone developed a "pinhead angels" model which ALSO make successful quantitative predictions of these dependencies, then yes, it would be just as valid as the standard model.

So do you see the problem yet? It doesn't offer any QUALITATIVE understanding.

Wait, what?

On the one hand, there's a theory which makes breathtakingly accurate predictions, is accessible to everyone on the planet (so can be independently, and objectively, verified and validated), and can explain every relevant historical experimental result.

On the other hand, there's a bunch of words, some strange diagrams, which no one understands or can explain, predicts nothing, and can explain no relevant historical experimental result.

The first one does not offer any qualitative understanding (or at least it does not, to you).

The second one does not offer any qualitative understanding (to everyone whose studied it, except you, and you have spectacularly failed - after many years of trying - to get even one other person to agree with you).

Would you care to try again?

 

[Ziggurat]

Oh spare me the perpetual ad-hominems of a naysayer who doesn't know any physics. Ben m mistook physics for maths. Displacement current is something real. See for example Taming light at the nanoscale where you can read this:

There isn't a single thing you've said here which makes ANY difference to the discussion at hand. Your link, for example, has nothing to do with pair production or photon-photon interaction. And insisting on the use of the term "displacement current" is really just a semantic objection. The "reality" of the term isn't in question, the results are, what it actually does, and for all your whining, you have nothing to show for it. You say that Ben is making a mistake, yet you can't actually demonstrate that mistake. You can't say, "this is a quantitative prediction Ben makes, this is the quantitative prediction I make, and here is the experiment proving that Ben's prediction is wrong and my prediction is right".

In fact, you can't make a single quantitative prediction at all.

Photons go in, electrons and positrons come out. And it's a photon-photon collider. It isn't a photon-angel collider, or a photon-chocolate teapot collider, or a photon-electron collider. It's a photon-photon collider. Is there some part of this you missed?

I haven't missed a thing. You, however, have missed the elephant in the room: a quantitative description of the events.

So do you see the problem yet? It doesn't offer any QUALITATIVE understanding.

Mythology presents a qualitative understanding of the world. You don't need science if that's all you're interested in. I want more than that. I want a quantitative understanding of the world. Science offers that. You reject that.

No it doesn't. The math is nothing to do with it. What is, is the fact that it's a photon-photon collider.

So you've got a "theory" which predicts that a photon-photon collider will produce particles. You can't say how often, and you can't say how many.

The standard model, however, CAN tell us these things.

It is your theory, not the standard model, which is essentially indistinguishable from the angel theory. Angels inside the collider wrap photons in a magic knot, turning them into electrons. There, I qualitatively understand it.

I'm just telling you that photons interact with photons mate.

The standard model tells me that. Except it tells me far more than that, too.

No need to start spitting feathers and huffing and puffing with outrage because somebody has the temerity to challenge the cargo-cult nonsense that pair production occurs because pair production occurs.

You are deeply, deeply confused.