What are quarks made of?

On what experimental basis do you use to speculate that they are made of anything?

On what experimental basis do you use to speculate that is is made of anything?

Space-time and/or quarks could turn out to be completely fundamental while they may both be some sort of emergent phenomena which is not simply described in terms of some currently unevidenced meta-reality. Speculation on no basis whatever is pointless and right now I have no basis for saying what they really are. I do however have a basis for saying that they pass every known test of being precisely modeled as fundamental objects of the best physical theories. Therefore any new theory has to explain in detail why the current theories do so well.

I would bet no since the Large Hadron Collider is multi-billion dollars of equipment that does not do anything like that.

Likewise, I would bet no because we have zero evidence that reality permits such excursions.

Fantasy and Reality are two different things and the nature of reality has always tightly constrained what fantasies can be realized. To put a man on the Moon or a probe on Mars or a video camera in a pill rely on sciences established for decades or centuries -- the same sciences that suggest that you can't get from A to B without passing through all the points inbetween in a quite pedestrian manner.

 

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You can always play the "why" game with any theory. Any theory is always going to reduce down to some unexplained axioms that just say "this happens" with no given more fundamental reason for it.

(Though I don't think it's fair to say that electron-photon interaction is completely unexplained in the standard model, since the electron-photon interaction term can be derived based on a principle of gauge symmetry.)

That is well known, and as has already been explained to you, the experimental fact that electrons and photons can be exchanged for one another is not evidence that one is actually a bound state of the other. In past discussions you failed to provide even a proof-of-principle model and you basically just ignored a number of obvious objections to and difficulties with the idea.

It is already the general expectation of the physics community that the Standard Model is incomplete. That doesn't mean you can propose just anything and pass it off as indisputable fact just because you're impatient. The God of Gaps argument doesn't pass in science: no explanation is always preferable to a bad or unsupported one. That is how science is kept open to progress. We don't pretend to know things we don't know.

 

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This one is just too wrong pryzk. See the wikipedia article? See where it says From quantum electrodynamics it can be found that photons cannot couple directly to each other? That's wrong. All that's there is two photons. They DO couple with one another. Gamma-gamma pair production works because of a photon-photon interaction, and you don't have to be a great physicist to realize this.

I haven't ignored anything. You're ignoring the photon-photon interaction. And photon self-interaction.

Instead you pretend to not know things that you do. You KNOW that a single photon doesn't spend its life fluctuating into an electron-positron pair that then magically morphs back into a single photon which nevertheless continues propagating at c. You KNOW that in low-energy proton-antiproton annihilation to gamma photons the "fundamental" quarks have totally gone. You and people like you have to face up to these facts to complete the standard model. Until you've done this, and understood how pair production works and what the electron really is, proposing SUSY and the selectrons is futile. Worse than futile.

 

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Obviously you've never bothered to study quantum electrodynamics. The QED Feynman diagram for pair production, straight out of the same Wikipedia article you just linked to, looks like this:

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There is no fundamental four-particle (\(\gamma\gamma e e\)) interaction in QED. You'd know that if you had ever so much as glanced at the QED Lagrangian. In QED, pair production is actually built out of two three-particle (\(\gamma e e\)) interactions. For instance a \(\gamma \,\rightarrow\, e^{+}e^{-}\) with e.g. the \(e^{+}\) then absorbing the second photon: \(\gamma e^{+} \,\rightarrow\, e^{+}\).

Maybe you don't like that account of things. But when it comes to explaining pair production as well as a whole host of other reactions we see, and getting the right numbers and cross sections out of it, that is the only model anyone has shown to be completely successful at that. And that's what counts the most. Everything else is secondary. You think a simpler or nicer or more intuitive or more complete explanation is possible? Fine. Show it works and that it gets all the numbers right. Ideally, show that you can recover the QED Lagrangian as an approximation, without putting in by hand the parts of QED that you disagree with (such as a fundamental electron field). Then we'll consider it.

No, Farsight, I don't know that. I don't, a priori, know the rules about what fundamental particles are and aren't allowed to do, and neither do you. That's the whole point of physics: to study nature and find out what things like particles can and can't do. Not to dictate what they can and can't do.

By the way, if particles can fluctuate into and out of existence (not really a good summary of QFT, IMO) then that is, practically by definition, not "magic".

You have to face the fact that your preconceptions are just that: preconceptions.

See, all I'm getting from a lot of your posts is that the physics community is willing to entertain a lot of ideas that you just don't like, and somehow that makes us narrow minded.

 

I've read the article, and much more besides, and regardless of what there is "in QED", pair production does not occur because pair production occurs. It's that simple, przyk. There's a photon-photon interaction going on. There are no electrons or positrons until after pair production has occurred.

And it's got a hole it I can drive a coach and horses through. A single photon does not spontaneously transform into an electron positron pair whereafter the e+ magically absorbs the second photon. Two photons interact. That's it. They're the particles that are there, and afterwards the electron and the positron are the particles that are there.

No you won't. You won't even consider the obvious problem. There's a blatant tautology, and you don't want to know. Supposing the two photons are 511keV photons or thereabouts. How can one of those photons turn into a 511keV electron and a 511keV positron? Which then allegedly absorbs the other 511keV photon but isn't off like a shot leaving the electron for dust?

Photons do not hoppity-skippity jump through space going at c, then less than c, then c, then less than c because they're fluctuating into electron-positron pairs. Electrons and positrons never combine into a single photon. Thinking that they do is cargo-cult science. It's trash, przyk. Even a child can see that.

I'm not the one with the preconceptions. I'm the one exposing yours.

 

If the photons of 511keV turned into positrons and electrons of the same energy, then they would be creating more energy without using fuel, for my part. this simply cannot happen, right?

 

No, and according to QED it occurs because the \(\gamma \,\rightarrow\, e^{+} e^{-}\) and \(\gamma e^{\pm} \,\rightarrow\, e^{\pm}\) interactions occur. As for the \(\gamma e e\) interaction, we know that it is a) one of the few possible interactions consistent with special relativity, renormalisability, and lower-bounded energy, and b) implied by U(1) gauge symmetry.

If you're going to complain about a mainstream physical theory, at least complain about what the theory actually has to say and not some silly strawman of it.

That is denial and an appeal to ridicule. You deny the idea without ever explaining what's actually wrong with it by scientific standards.

So you start with two photons and you end up with an electron-positron pair. That says nothing about the best way to actually model the process in a way that reproduces all its quantitative features we see in experiments. On what basis do you disregard the results of researchers who, unlike you, actually worked on that problem?

What, the one above? The one you misattributed to QED?

Next time you claim a mainstream theory is based on a tautology, kindly cite and quote the textbook, review article, or founding research paper that actually presents things that way.

Now you're confusing classical and quantum physics. Like you are so fond of explaining to everyone, quantum particles are not and do not behave like little billiard balls. In quantum physics, if you have a short-lived particle -- like the positron we're talking about propagating between two interactions -- it fundamentally doesn't make sense to talk about its energy as if it had a fixed and well-defined one.

You may know that in quantum physics a particle's energy is basically the same thing as its frequency. You know what has a fixed and perfectly well-defined frequency? A wave propagating from \(t \,=\, -\infty\) until \(t \,=\, +\infty\).

If you're talking about asymptotic behaviour, then QED correctly reproduces this.

You can calculate, from QED, the probability of detecting a photon if you make an electron and a positron collide. It's practically zero. You can also, from QED, calculate the probability of detecting an electron-positron pair if you make an electron and a positron collide. According to QED the first order ("tree level") interaction involved is \(e^{+} e^{-} \,\rightarrow\, \gamma \,\rightarrow\, e^{+} e^{-}\). The probability of that happening is not zero. (Lesson 1 in quantum physics: probabilities of events generally don't add or multiply the way you would expect them to classically.)

If it's trash, then a) why does it work so well, and b) why can't you do better than completely misunderstand it and call it names?

 

Here the relevant conservation laws are those of relativistic momentum, \(p\), and energy, \(E\).
Here \(m_e \; \approx \; 0.511 \, \textrm{MeV} / c^2\)

So for the photons (\(\gamma\)) we have \(E_1 = c \left| \vec{p}_1 \right|\) and \(E_2 = c \left| \vec{p}_2 \right|\), while for the electron (\(e^{\tiny -}\)) and positron (\(e^{\tiny +}\)) we have
\(E_3 = \sqrt{ \left( m_e c^2 \right)^2 + \left( c \left| \vec{p}_3 \right| \right)^2 }\) and
\(E_4 = \sqrt{ \left( m_e c^2 \right)^2 + \left( c \left| \vec{p}_4 \right| \right)^2 }\), respectively.

Everyone agrees that \(E_1 + E_2 = E_3 + E_4\) and \(\vec{p}_1 + \vec{p}_2 = \vec{p}_3 + \vec{p}_4\) (the conservation laws) apply to relativistic pair production which is given schematically as the process \(\gamma + \gamma \longrightarrow e^{\tiny -} + e^{\tiny +}\). Therefore \(E_1 + E_2 \geq 2 m_e c^2\) with this being an equality only when \(\vec{p}_1 = -\vec{p}_2\) and \(E_1 = E_2 = m_e c^2 \; \approx \; 0.511 \, \textrm{MeV}\). (In this case \(\vec{p}_3 = \vec{p}_4 = 0\) and \(E_3 = E_4 = m_e c^2 \; \approx \; 0.511 \, \textrm{MeV}\) so no extra "fuel" is required -- 511 keV refers to relativistic energy which include rest mass energy (511 keV) and kinetic energy (0 keV).)

Farsight is attempting to argue that since process \(\gamma \longrightarrow e^{\tiny -} \) cannot conserve both momentum and energy (or electric charge) that the process \(\gamma + \gamma \longrightarrow e^{\tiny -} + e^{\tiny +}\) requires an interaction that turns two photons into two charged particles. However since the Lagrangian for quantum electrodynamics has no such term, but does couple the electromagnetic field with the electron field in such a way that we have photon excitations always ending or starting on an electron, we can compose the process as :

\(\begin{eqnarray} \gamma & \longrightarrow & e^{\tiny -} + e^{\tiny 5} \\ & \downarrow e^{\tiny 5} & \\ \gamma + e^{\tiny 5} & \longrightarrow & e^{\tiny +} \end{eqnarray}\) or \(\begin{eqnarray} \gamma + e^{\tiny 5} & \longrightarrow & e^{\tiny -} \\ & \uparrow e^{\tiny 5} & \\ \gamma & \longrightarrow & e^{\tiny +} + e^{\tiny 5} \end{eqnarray}\) where the extra electron transfers energy and momentum. This is possible since these "electrons" and "positrons" are modeled as nothing more than excitations of the fundamental "electron quantum field" which can support short-lived momentum-transfering phenomena where the condition of obeying \(E = \sqrt{ \left( m_e c^2 \right)^2 + \left( c \left| \vec{p} \right| \right)^2 }\) is relaxed. These internal lines in perturbation theory associated with the quantum electrodynamic Lagranian are called virtual particles which Farsight is biased against.

Also, please don't quote a whole lengthy post to just ask a short question. You are encouraged to edit the quote down to just the part that concerns you or omit the quote and address the poster directly if the context of your question is obvious.

 

Hi rpenner, pryzyk, MarkM125.

I agree with your 'explanation' rpenner, but only so far. Unlike the conventional/current math/abstract models/explanations which you guys have presented with great erudition, my naive approach of reality observations allows me to go further into the reality of what is happening in the electrons/photons pair-creation/annihilation 'event centre' being discussed.

That further reality is based on mainstream observation and not on some abstract mathematical 'modeling' involving 'virtual' particles; but based on real 'intermediate' particles which are 'intermediate excitations' in an 'intermediate field' which 'bridges the 'theoretically separate' electron field and photon field; as I foreshadowed here....

In my earlier response to MarkM125, I addressed the reality of the composite field which is known already to exist as such 'empirically' and not just 'theoretically modeled':

This empirically observed and technologically utilized plasmonic 'field' exists, and is basically described as a plasmon 'sea' combining the energies of photons and electrons, which 'sea' behaves like a field which 'couples' the e-m energies and features of the electron field and the photon field. The 'identities' of the electron and the photon 'merge' into an 'amorphous' mixture of the energy contents of both electron and photon 'constituents'.

When we consider the plasmonic field and localized energy content therein, we can see how it could be that, in some 'collision' scenario 'event centre' having certain energy quotients from photons/electrons contributing to that event (pair annihilation/pair creation), the energy is transiently in a plasmonic form in the plasmonic field, and not in electronic or photonic energy/field per se.

Eventually (quite brief event duration) the 'event' resolves itself via resonance and other perturbation dynamics during the brief 'plasmonic phase', resulting in either 'electrons' OR 'photons'. Any 'intermediate 'particles/features' are 'plasmonic' state, neither one nor the other (effectively and qualitatively 'equivalent' to the abstract model 'virtual' features in the current quantum theory).

So, in the end, all that matters is the 'plasmon state/field' energy available in an event centre, and the resonant dynamics of said 'plasmon state/field' energy differentiation into the most fundamental 'stable' features (either electrons or photons) which can 'leave' from said event via their distinguishable e-m/electron field-excitation modes/speeds. This reasonable 'plasmonic' field/energy state process/scenario also indicates that the electron energy 'merges' with the photonic energy, hence implying that the electron 'standing configuration' dissociates into the more 'fundamental' form of 'plasmonic' state/field, which in turn implies that electron has a 'standing substructure' which can be transiently disrupted in sufficiently energetic 'events' where photonic and electronic energy can 'transiently merge' and then re-differentiate according to the dynamics involved at the event centre.

Thanks to you all, rpenner, MarkM125, pryzyk, Farsight and Mazulu, for your interesting discussions here. Most stimulating and helpful. Bye for now.

 

I am. And in case you didn't notice, you just reiterated the silly assertion that pair production occurs because pair production occurs. It doesn't.

Yours is the denial, I've explained what's wrong with it. And yes, I will ridicule it. it's called reductio ad absurdum.

On the basis that they offer a tautology instead of an explanation.

I don't need to, because you've demonstrated that the Wikipedia article is faithful to your understanding of QED.

Oh that's all right then, on top of everything else we can throw conservation of energy out of the window. And we can let that 511keV positron travel at the speed of light to make sure it gobbles up the other 511keV photon, whereafter it's still a 511keV positron. This fairy story just gets worse and worse przyk. Why on Earth are you defending it?

Huh? Are you trying to say a 511keV photon can have any energy you like? Because it didn't start its little life an infinite time ago? Or that the your positron can have some negative energy? Geddoutofit przyk.

Now you're throwing out conservation of momentum too. This is going downhill, przyk.

It works so well because the leading half of the photon behaves somewhat like a partial positron. And I haven't misunderstood it. The photon is not a positron with an electron on its tail, and you cannot chop it in two lengthways.

 

What I'm saying rpenner, is that it needs one, and that it also needs to recognise that the electron field is a configuration* of the photon field rather than a separate field in its own right, therefore being in line with electroweak unification. This is merely an interpretational change, and it will advance the standard model.

I'm not biased against virtual particles. But I am opposed to the myth that they are short-lived real particles. They aren't. I thought Matt Strassler did a fairly good article on virtual particles:

"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."

Please have a word with przyk about conservation laws.

* you can maybe find an alternative word or phraseology, no problem.

 

But it was said that one 511keV makes two particles of both being 511keV? if they were both the same sort of particle then they would repel each other? that would mean they could not form a atom or quark or anything...?

Virtual particles are those that expend energy in their movement. if they do not move much, say they are 'trapped' or paired, then they would not lose energy or the whole world would dissolve. what you are saying is that the world dissolves around us as we go from place to place. you could say though that animals are virtual particles, as they expend energy that needs to be replenished through eating and drinking, yes?

So, if the particle is virtual, it will dissolve into nothing, meaning that somewhere down there, there is stuff disappearing. if that is true, then how can it be, as an accepted 'deal with the universe,' that no energy disappears, it just changes form? what does it change form into?

 

In case you didn't notice, I actually said something very different. You had to quote me out of context to make it appear like I was stating a tautology, and even the part you do quote isn't a tautology. It explains that pair production, i.e. the reaction \(\gamma \gamma \,\rightarrow\, e^{+} e^{-}\), is composed out of more primitive interactions, one of which is \(\gamma \,\rightarrow\, e^{+} e^{-}\).

Note that I did not say that the \(\gamma \,\rightarrow\, e^{+} e^{-}\) interaction occurs because the \(\gamma \,\rightarrow\, e^{+} e^{-}\) interaction occurs. That would have been a tautology had I said something that amounted to that. But I didn't.

Seriously, just how mind-numbingly obtuse and dishonest can you get? When you quote me out of context like this, you are a simple copy-and-paste away from me lighting it up like a billboard for everyone to see.

And what, precisely, would I be denying?

No. Reductio ad absurdum is a form of argument where you show that a number of axioms together leads to a logical contradiction, from which you conclude that one of the axioms must be wrong.

You gave no such argument. All you did was take QED and call it names. That is not a rational form of argument.

The only tautology you identified was a strawman of your own invention. Nobody pretends that "pair production occurs because pair production occurs" is a valid logical argument, and nobody except you attributes it to QED.

As you should have picked up on by now, pair production is not even considered a fundamental interaction in QED. It's rather the \(\gamma e e\) coupling that would better fit that description. Depending on how you want to think about it, you can either take the \(\gamma e e\) coupling as a postulate that is simply part of the definition of QED, or you can take it as a consequence of U(1) gauge symmetry and take that as a postulate that is part of the definition of QED. In neither case is it a tautology. A postulate is simply where our understanding of the fundamentals of a theory ends.

Huh? You again seem to casually forget that QED is a quantum theory. Energy conservation in a quantum theory means that the probability distribution of a quantum state over the various eigenstates of the Hamiltonian is invariant in time. QED, of course, necessarily satisfies this form of energy conservation -- the only one we think rigorously and fundamentally holds -- trivially by construction as a quantum theory.

The type of (classical) energy conservation you are holding to has not been considered fundamental or accurate since quantum physics was invented. Same with momentum, incidentally.

More generally, the Standard Model has been extensively tested in accelerators and is consistent with all known experimental data. So if you think the Standard Model violates some deeply held principle of yours, that principle is not supported by any evidence.

Evidence? Model of this behaviour, and demonstration that it is consistent, within error bars, with say everything in the particle physics booklet?

 

The word atom means not cuttable. "a" meaning not.
Surely we should now rename the atom "Tom"

 

It isn't. It's a photon-photon interaction. It's pair production. It doesn't work because there's a "more primitive" pair production that happened like spontaneous words-from-mud magic. Jesus H Christ przyk, think man. Don't you get this tautology thing yet? Pair production does not occur because pair production occurs. It occurs because one photon interacts with another. That's the more primitive interaction. QED doesn't model it. And it needs to.

You are fooling yourself. Look above at your "more primitive". You just said it again!

You're being mind-numbingly abtuse. Go ahead, light me up. And I will light up your more primitive.

The photon-photon interaction. You start with two photons. They interact. Then you've got an electron and a positron. Not before.

You're in denial again.

Apart from those who say it's composed out of more primitive interactions, one of which is \(\gamma \,\rightarrow\, e^{+} e^{-}\). Now who said that? Let me think. Why przyk, that was you!

And what you should have picked up on by now is this: it should be.

Oh, it's a postulate is it? A definition? Since when did QED turn into Humpty Dumpty physics? Understand this: the fundamental interaction is \(\gamma \gamma \rightarrow e^{+}e^{-}\). Now go away and fix QED for me.

rpenner, earn your spurs. Come and put przyk straight.

Again, go and fix it for me. Because you cannot make a 511KeV electron and a 511KeV positron out of a 511KeV photon all on its own.

I don't. I think it's incomplete, and that this is an example of how incomplete it is.

Don't you thump your bible at me, przyk. It won't get you off the hook.

 

That's what is said, but it isn't true. If it was I could whip away the second photon and voila, I've got free energy.

You misread that. The assertion is one 511KeV photon spontaneously becomes a 511keV electron and a 511keV positron.

Have a read of Matt Strassler's article on virtual particles. See this bit: 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. Przyk will try to tell you that the first 511KeV photon magically morphs into an 511KeV electron and a 511keV positron. What he neglected to mention was that these are virtual particles. And that a virtual particle is not a particle at all.

Best to set virtual particles aside for a moment. In gamma-gamma pair production, each photon changes form. One changes form into an electron, the other changes form into a positron. There is no magic wherein the photons mysteriously disappear whilst electrons and positrons spontaneously pop into existence. Electron-positron annihilation is the reverse of this. It's nothing exotic, it's done in PET scanners in hospitals, see this: http://tech.snmjournals.org/content/29/1/4/F1.expansion.html

 

You are asserting that on the basis of no evidence and no theoretical model that could even be compared with evidence. In short, you are making an assertion by fiat without explaining why anyone should actually believe you.

Farsight, do you speak English? Can you not tell the difference between "X because X" and "X because Y"?

I don't need to deny anything in this regard. It's you who seems to be operating under some serious confusion about where the burden of proof lies.

You want to claim that everything we see in particle accelerators can be understood in terms of a theory with a direct photon-photon interaction? It never seems to occur to you that if you want to say something like that, and you expect to be taken seriously, then you have a hell of a lot of work to do in supporting that conclusion.

That's not a tautology, Farsight.

Then again, you apparently can't tell the difference between an appeal to ridicule and a reductio ad absurdum, so I'm not sure what I would have expected of you.

Because you say so?

Yes. QED has a definition and postulates. Just like any other theory.

I don't take orders from you. Seriously, just who do you think you are?

We already think the Standard Model is probably incomplete, for much better reasons than anything you've given here.

I am asking you to show you can explain experimental evidence. Did you not bother to look up what the particle physics booklet actually is before posting your knee-jerk reaction? You just blew off everything that is actually known and measured about particles. You just blew off all the data that any proposed theory of particle physics would have to explain.

I guess you must think that the accepted standards of scientific discourse just don't apply to you. It would explain a lot.

 

This is a new misconception on the subject , Duffield. You must have made this one up specially for this thread.

 

No, that's essentially how it is. You might prefer to say the energy changes form or offer some variant, but that is what happens. Particles don't disappear whilst other particles appear like magic.

przyk: sorry, I have to go out. I'll respond later or tomorrow. Hopefully rpenner will clear up your problems with conservation of energy etc. He's a good sincere poster on whom we can all rely. Isn't that right rpenner?

 

Duffield,

You are trying to side step the fact that you just got caught spewing another "pearl". LOL