Why is there so much crackpot physics?

[Farsight]

Nope, looks fine to me. You have quoted a wordy verbal description of the well-tested QED Lagrangian, cited later in the paper, which is the part that makes the testable predictions. If you have a problem with a QED, you have to have a problem with that Lagrangian. Which you don't. Because you don't understand it.

I understand it, you don't. And it's not fine. Now pay attention:

"Virtual electron-positron pairs, can in principle, be polarised by an external electromagnetic field, thus introducing non-linearities into Maxwell’s equations, which break the familiar principle of superposition of electromagnetic waves in vacuum. Photons from multiple, vacuum-polarising sources, can then become coupled on the common point of interaction of the polarised virtual pairs".

It's gamma-gamma pair production remember? But it's saying a photon interacts with a virtual electron-positron pair. It's saying pair production occurs because pair production has already occurred. It's a tautology. It's wrong. A photon does not spend its sad little life magically morphing into an electron-positron pair that magically manage to morph back into a single photon, which nevertheless manages to keep on going at c. QED does not model the photon-photon interaction.

Right, I'm off to bed. You've got until tomorrow to try and save some face.

 

[lpetrich]

A photon does not spend its sad little life magically morphing into an electron-positron pair that magically manage to morph back into a single photon, which nevertheless manages to keep on going at c.

But that morphing is what one finds when one calculates the photon's propagator, a function which expresses the strength of creating one at one position and then removing it from another position.

Farsight's main argument here is how absurd it seems, which is not much of an argument.

 

[ben m]

But it's saying a photon interacts with a virtual electron-positron pair.

Yep. About as good as a verbal description gets.

It's saying pair production occurs because pair production has already occurred. It's a tautology. It's wrong.

Why didn't you say so before? Anyway, if you want a verbal description: this is quantum mechanics. Whether something "has already occurred" or not is an imprecise statement to begin with, and this formulation is reasonably clear. If you are looking at a Dirac-Equation-centric derivation (leading to Feynman diagrams) it is easiest to translate into words like "pair creation" and "annihilation operator". If you are looking at at Maxwell's-Equation-centric derivation, the exact same mathematical terms are easiest to describe as "polarizability" and "susceptibility". I suppose the latter language encourages you to think of the electron-positron pairs as "already there" in the vacuum (as would have been the case in polarizable solids) whereas the former encourages you to think of them as "created" during the interaction, but ... I mean, why would you try to mine all of this meaning out of a few words when the equation on the next page is very precise about what it means?

Oh, I know: because you're looking for an argument, and you don't know how to argue with an equation, because you don't do math.

 

[Reality Check]

It's gamma-gamma pair production remember?

That is a really odd statement, Farsight.
* I search Photon-photon scattering in collisions of laser pulses (PDF) and find no mention of "gamma" let alone "gamma-gamma pair production"
* What you quote is about virtual particles but pair production is usually real particles. The paper uses "pair-creation".
* What you quote is not about a photon "morphing into an electron-positron pair". It is about virtual particle pairs appearing out of the vacuum and then annihilating each other a short time later. This is standard quantum field theory.
* QED does model the photon-photon interaction. The paper is using QED to model the photon-photon interaction!

It is impossible to remember something in a paper that does not exist in that paper .

ETA: Perhaps an explanation from my perspective will help:
* Maxwell's equations say that electromagnetic fields just add up in a vacuum (are linear).
* Virtual electron-positron pairs are always popping in and out of existence in a vacuum.
* An external electromagnetic field should polarize these virtual electron-positron pairs.
* That polarization will add an extra component to the addition of electromagnetic fields thus they will not just add up as in Maxwell's equations.
* Photons are electromagnetic fields !
Thus take a couple of laser beams and let them cross. The EM field of each beam will polarize the virtual particles thus affecting the other beam. There will be a non-linear effect that could be detectable in intense laser beams.

 

[ben m]

Sorry, misposted

 

[Perpetual Student]

For the sake of accuracy, here is a summary of the exchange about protons and electrons are photons in "loops."

http://www.internationalskeptics.com/forums/showpost.php?p=9868269&postcount=129

The key being:

I will repeat my challenge that there is no experimental or theoretical basis within QFT for the notion that electrons and protons are photons in some kind of "loops."
If you have evidence to the contrary this would be a good time to present it -- and please do include your "pointer."

 

[Farsight]

Yep. About as good as a verbal description gets.

It isn't good. It's badly wrong.

Why didn't you say so before? Anyway, if you want a verbal description: this is quantum mechanics. Whether something "has already occurred" or not is an imprecise statement to begin with, and this formulation is reasonably clear. If you are looking at a Dirac-Equation-centric derivation (leading to Feynman diagrams) it is easiest to translate into words like "pair creation" and "annihilation operator". If you are looking at at Maxwell's-Equation-centric derivation, the exact same mathematical terms are easiest to describe as "polarizability" and "susceptibility". I suppose the latter language encourages you to think of the electron-positron pairs as "already there" in the vacuum (as would have been the case in polarizable solids) whereas the former encourages you to think of them as "created" during the interaction, but ... I mean, why would you try to mine all of this meaning out of a few words when the equation on the next page is very precise about what it means? Oh, I know: because you're looking for an argument, and you don't know how to argue with an equation, because you don't do math.

Er, no. We're on the crackpot physics thread, I'm pointing some out, you're pretending you can't see it, and trying to hide behind math. Tsk. Watch and learn...

That is a really odd statement, Farsight.
* I search Photon-photon scattering in collisions of laser pulses (PDF) and find no mention of "gamma" let alone "gamma-gamma pair production"
* What you quote is about virtual particles but pair production is usually real particles. The paper uses "pair-creation".
* What you quote is not about a photon "morphing into an electron-positron pair". It is about virtual particle pairs appearing out of the vacuum and then annihilating each other a short time later. This is standard quantum field theory.

Virtual particles are virtual. They aren't real particles that appear out of the vacuum and annihilate one another a short time later. See Matt Strassler's article. OK, now take a look at the wiki Two photon physics article. It says "A photon can, within the bounds of the uncertainty principle, fluctuate into a charged fermion–antifermion pair, to either of which the other photon can couple". Now watch my lips: no it can't. A 511keV photon does not hoppety-skip through space magically morphing into a 511keV electron and a 511kev positron, which magically turn back into a single 511keV photon which all the while manages to keep on travelling at the speed of light. And pair production does not occur because pair production occurred. Spontaneously. Like worms from mud. That's crackpot!

* QED does model the photon-photon interaction. The paper is using QED to model the photon-photon interaction!

The paper gave you a photon-electron interaction. So does wiki. See this bit: "From quantum electrodynamics it can be found that photons cannot couple directly to each other, since they carry no charge". Somebody has inserted the next sentence since I've raised this issue. The front portion of a photon is a little like a partial positron, the back is a little like a partial electron. But the main point is that photons interact with photons, and QED doesn't cover it.

...Virtual electron-positron pairs are always popping in and out of existence in a vacuum...

No they aren't. That's pop-science cargo-cult physics.

 

[edd]

The front portion of a photon is a little like a partial positron, the back is a little like a partial electron. But the main point is that photons interact with photons, and QED doesn't cover it.

Wow. I expect some things from Farsight but I didn't expect anything like that.

 

[Farsight]

I tell you edd, this is a big issue. And you heard it here first.

 

[edd]

Yeah, all photons having a positive charge at the front and a negative one at the back, and you knowing where QED is wrong - that'd definitely count as big. And I definitely heard it hear first.

 

[ben m]

Virtual particles are virtual. They aren't real particles that appear out of the vacuum and annihilate one another a short time later.

Yes, they're virtual particles that appear out of the vacuum and annihilate one another a short time later.

It says "A photon can, within the bounds of the uncertainty principle, fluctuate into a charged fermion–antifermion pair, to either of which the other photon can couple".

Again, this is another reasonably good way to verbally describe the QED Lagrangian. Which has been extensively tested in experiments.

Now watch my lips: no it can't. A 511keV photon does not hoppety-skip through space magically morphing into a 511keV electron and a 511kev positron, which magically turn back into a single 511keV photon which all the while manages to keep on travelling at the speed of light.

Of course it doesn't. Again, a better verbal description of the physics is that it morphs into a (virtual) massless electron and a massless positron---in the language of QED the word is "off-shell"---which annihilate and return to being a massless photon. There's nothing wrong with that, and the general effect being used ("the mass in a propagator is subject to quantum-mechanical uncertainty") has been observed directly in experiment.

I'm curious which QED books you've read such that you didn't learn this extremely basic fact about virtual particles.

 

[ben m]

All verbal descriptions of QED are "really wrong" and "pop science".

All mathematical descriptions of QED are "hiding behind math"

All experimental predictions/confirmations of QED are (*&#$!@&@^@@

(Numerical QED predictions and experimental confirmations do not register in this system. It was just swamp gas. Please look into the neuralyzer---ZAP. What were we talking about? Spring training has started, will Jeter's ankle hold up do you think?)

 

[Perpetual Student]

Yeah, all photons having a positive charge at the front and a negative one at the back, and you knowing where QED is wrong - that'd definitely count as big. And I definitely heard it hear first.

Maybe that's the big overdue "pointer" I've been promised.
Farsight, can you produce some experimental evidence and an alternative to the standard QED treatment of the photon to demonstrate this revelation?
Your Nobel prize is being polished as you read this.

 

[ben m]

I love that Farsight's photons violate charge-reversal and time-reversal invariance. It's not "some sort of charge form factor", it's specifically + at the front, - at the back. When did that start, Farsight? Before or after Ben Franklin decided on the arbitrary sign convention? Does a photon emitted by antimatter have the opposite electric dipole?

How large are these charges and how far apart are they? Are they approximately one wavelength apart, for example? Perhaps I can compare your predictions to an experimental result I have right in front of me which is relevant to this sort of hypothesis.

 

[Dancing David]

The better question is how does that charge separation occur at all?

I mean they would attract and cancel right away.

 

[edd]

The better question is how does that charge separation occur at all?

I mean they would attract and cancel right away.

Nah they both have to go at the speed of light remember?

 

[Farsight]

Yeah, all photons having a positive charge at the front and a negative one at the back, and you knowing where QED is wrong - that'd definitely count as big. And I definitely heard it hear first.

They don't have a positive charge at the front and a negative charge at the back. That's not what I said. See two-photon physics and note that it does say this: but half wavelength is a positive charge and the next half wavelength is a negative charge. That's wrong, and I said the front portion of a photon is a little like a partial positron, the back is a little like a partial electron. Draw a positive field variation followed by a negative field variation.

 

[Farsight]

Yes, they're virtual particles that appear out of the vacuum and annihilate one another a short time later.

It's a popscience myth. It doesn't actually happen. Space is not a seething maelstrom of electrons and positrons popping in an out of existence. A virtual particle is not a real particle. Nor is it a short-lived real particle. As per Matt Strassler's article, it is not a particle at all. Pay attention now:

"The best way to approach this concept, I believe, is to forget you ever saw the word “particle” in the term. A virtual particle is not a particle at all. It refers precisely to a disturbance in a field that is not a particle".

Again, this is another reasonably good way to verbally describe the QED Lagrangian. Which has been extensively tested in experiments.

No it isn't. A 511keV photon does not hoppety-skip through space magically morphing into a 511keV electron and a 511kev positron, which magically turn back into a single 511keV photon which all the while manages to keep on travelling at the speed of light. And pair production does not occur because pair production occurred. That's a tautology. That's crackpot.

Of course it doesn't. Again, a better verbal description of the physics is that it morphs into a (virtual) massless electron and a massless positron---in the language of QED the word is "off-shell"---which annihilate and return to being a massless photon. There's nothing wrong with that, and the general effect being used ("the mass in a propagator is subject to quantum-mechanical uncertainty") has been observed directly in experiment.

There's plenty wrong with that. Virtual particles are not real particles. Electrons are not massless. An electron and a positron cannot annihilate to a single photon. It's a fairy tale, ben.

I'm curious which QED books you've read such that you didn't learn this extremely basic fact about virtual particles.

I "learned this basic fact" years ago. I can't remember where from. But I rejected it as a fairy tale when I learned more physics. You will too.

I love that Farsight's photons violate charge-reversal and time-reversal invariance. It's not "some sort of charge form factor", it's specifically + at the front, - at the back. When did that start, Farsight? Before or after Ben Franklin decided on the arbitrary sign convention? Does a photon emitted by antimatter have the opposite electric dipole?

Don't look at me. Look at whoever edited that Wikipedia article.

How large are these charges and how far apart are they? Are they approximately one wavelength apart, for example? Perhaps I can compare your predictions to an experimental result I have right in front of me which is relevant to this sort of hypothesis.

See my reply to edd above. I've never said a photon consists of two charged particles. That's would be getting things totally back to front.

 

[ben m]

They don't have a positive charge at the front and a negative charge at the back. That's not what I said. See two-photon physics and note that it does say this: but half wavelength is a positive charge and the next half wavelength is a negative charge. That's wrong,

It IS wrong. It was added by an anonymous user who also added gibberish to the "proton" article.

and I said the front portion of a photon is a little like a partial positron, the back is a little like a partial electron. Draw a positive field variation followed by a negative field variation.

And that's wrong too. Please do not add it to Wikipedia. I can "draw a positive field variation followed by a negative field variation". The former is nothing like a positron, in whole or in part, whatever that means. The latter is nothing like a partial electron. The two together are nothing like a photon.

 

[Farsight]

It IS wrong. It was added by an anonymous user who also added gibberish to the "proton" article.

I'm glad we agree about something.

And that's wrong too. Please do not add it to Wikipedia.

I've never updated Wikipedia, and have no plans to do so.

I can "draw a positive field variation followed by a negative field variation". The former is nothing like a positron, in whole or in part, whatever that means. The latter is nothing like a partial electron. The two together are nothing like a photon.

Sorry ben, but you're wrong about this. Like I said, a 511kev photon doesn't spontaneously morph into an electron and a positron which you label as "off shell" so you can break all the rules of physics. Virtual particles are virtual, they don't pop in and out of existence like magic. But QED can handle photon-photon pair production, for a reason. Yes, the anonymous wiki editor got it wrong, but the "given reason" really is crackpot. Think about it. Think for yourself.

Gotta go.