ctamblyn
Data Ghost
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Farsight, prove it. Unless you do so, you won't get that trip to Stockholm.
It's explained by quantum electrodynamics, a subset of the Standard Model. Here's what goes on. One of the photons becomes a virtual electron and a real electron, and the other photon runs into that virtual electron, making the other electron. Remember that these are all quantum fields, not billiard-ball classical-limit particles.
(Einstein-thumping snipped)
See what lpetrich said above:
"One of the photons becomes a virtual electron and a real electron, and the other photon runs into that virtual electron, making the other electron".
We'll cut him some slack for referring to electrons rather than electrons and positrons. Also see Two photon physics on Wikipedia:
"From quantum electrodynamics it can be found that photons cannot couple directly to each other, since they carry no charge, but they can interact through higher-order processes. 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".
It's cargo-cult kid's stuff nonsense. A photon does not magically transform itself into an electron and positron with which the other photon can couple. Pair production does not occur because pair production occurred.
DeiRenDopa
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Wait, you're using Wikipedia as a primary source, for a fundamental question about QED?!?
Shouldn't you be using at least a standard (post-grad?) textbook on QED, if not a landmark paper or two? You know, full of equations and stuff?
No. That would be like bible-thumping.
Besides, lpetrich was my primary source. And he gave the given explanation that contains the blatant tautology. It's a patent non-explanation. It's obvious cargo cult trash.
Now, why don't you go and ask around about it? Do your own research, like I do.
Besides, lpetrich was my primary source. And he gave the given explanation that contains the blatant tautology. It's a patent non-explanation. It's obvious cargo cult trash.
Now, why don't you go and ask around about it? Do your own research, like I do.
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Not according to Maxwell's Equations. Nor according to QED. Not according to the Standard Model of Particle Physics. (All of which have made wall-to-wall confirmed experimental predictions, of course.)
What model of the photon tells you that they have direct interactions? What experimental data favors this model over the ones above?
No, the given explanation says pair production occurs and gives a complete quantum-mechanical description of what happens when it occurs. The physics ideas used in constructing this explanation, and interpreting it, and teaching it, are exactly the same as the methods used throughout quantum mechanics. QED explains why pair production (of anything, not just electrons) occurs. Also scattering. Also annihilation. Also diffraction. Also charged-particle paths in electromagnetic fields. Also decay.
There is no content whatsoever to your now-100-times-repeated "objection."
It's not really an objection at all, is it? It's generic denialism, isn't it? "I read something and didn't understand it. Here is an ignorant summary of it. The summary is obviously inadequate and you know it. The thing I read is therefore wrong and you know it." It works for anything! "Wave optics says that lenses focus light because lenses focus light." "Newton's Laws say things move because things move." "Schrodinger's Equation says electrons diffract because electrons diffract." "Math says pi is irrational because it's irrational."
ctamblyn
Data Ghost
I can see what lpetrich wrote. Nowhere did he say, as you put it, "pair production occurs because pair production occurs."
In any case, why can't you show me where QED says "pair production occurs because pair production occurs?"
ctamblyn
Data Ghost
To be fair, that argument does establish irrationality of a sort.
I was being general. "Electrons" here included both ordinary electrons and positrons. They are described by the same quantum field equation.
Empty assertion.
Wait, you're using Wikipedia as a primary source, for a fundamental question about QED?!?
Shouldn't you be using at least a standard (post-grad?) textbook on QED, if not a landmark paper or two? You know, full of equations and stuff?
Why so?
I'm explaining in nonmathematical terms what one can find worked out in some standard text on quantum field theory or the Standard Model. In fact, I second DeiRenDopa's recommendation of studying the primary literature.
That's hilarious.
You go back and forth between directly contradictory beliefs about the status of your ideas:
- "Every textbook, paper, Wikipedia article, online lecture notes, etc., says the explicit opposite of what I'm saying, because they're all wrong."
- "Stop contradicting me, ask anyone, do a simple Google search, everyone knows I'm right."
I have no idea how these two ideas coexist in your head. They're opposites.
"Do your own research" is also hilarious. Dude, I'm a professional physicist. I have read more physics research papers than you have read physics Wikipedia articles. The number of positrons I've actually detected exceeds the number of times you have used or heard the word "positron". The number of QED, QM, and E&M problems I've sat down and solved exceeds the number of QED/QM/EM equations that have passed before your eyes. (But because I don't share your incredulity about virtual particles, you think it's because I haven't ... um ... done a Google search for the word "virtual particles"? Which is what you think of as "research"? Riiight.)
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Perpetual Student
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The above should motivate any sincere student of physics to re-evaluate his views on this subject. Only an arrogant fool would persist in his folly.
Hellbound
Merchant of Doom
Reality Check
Penultimate Amazing
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.
If you could collect all the ash and smoke and weigh it, it would weigh much more than the original coal because oxygen has been added.
If you could collect all the ash and smoke and weigh it, it would weigh just a little but less than the original coal plus the oxygen added.
My point was that light emitted from fires is the conversion of a change in binding energy to photons. Rest masses do not change. Weights do change but IMO not really because of Special Relativity - they change because General Relativity has gravity (and thus weight) from rest masses and energy.
IOW:
* In SR, weights do not change in fires because light is emitted (photons have energy but no mass, i.e. m = 0 in E=mc2).
* In GR, weights do change because light is emitted since weight depends on both mass and energy. In general this is not a weight of m =E/c2.
AFAIK: On Earth though the change in weight is m =E/c2 where E is the change in binding energy because we are in a weak enough gravity field. Do the same experiment on the surface of a neutron star and all bets are off!
What looks li9ke a repeated fantasy from you, Farsight, is:
That is not what physics tells us.
That is not what a moment's thought tells anyone - photons are neutral and so cannot directly interact electromagnetically. They do not interact via the strong or weak forces. They have no mass and so do not interact directly through gravity. They have energy so there is an argument for an enormously weak gravitational interaction. I hope that is not what you are talking about
.Reality Check
Penultimate Amazing
Two photon physics: photons cannot couple directly to each other
:
"From quantum electrodynamics it can be found that photons cannot couple directly to each other, since they carry no charge, but they can interact through higher-order processes. 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".
Also see Two photon physics on Wikipedia stating that you are wrong, Farsight
:"From quantum electrodynamics it can be found that photons cannot couple directly to each other, since they carry no charge, but they can interact through higher-order processes. 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".
Reality Check
Penultimate Amazing
Unfortunately, Farsight, your "research" mostly looks like Google searches followed ignoring or misunderstanding or quote mining what you find.
See Two photon physics: photons cannot couple directly to each other which contradicts your often repeated assertion that Photons do have direct interactions with each other.
My "research" consists of a science oriented high school education, 3 years of undergraduate study (physics, chemistry, math, computing), 4 years of graduate work (the last 3 concentrating on theoretical state physics) and an ongoing interest in science from then on.
I am the first to admit that not practicing science for almost 30 years leads to some mistakes from me. But at least I can read and understand Wikipedia
!In SR the inertial mass of a system is dependent on it's total energy, not on the rest mass of it's constituent particles. And the gravitational mass is equal to the inertial mass.
An obvious example: check out how much a lump of Uranium weighs. Compare to weight of a lump of other atoms with the same number of protons, neutrons, and electrons. This difference doesn't require GR to explain.
Well, seeing as you dismissed Maxwell when we were talking about the screw nature of electromagnetism, we'll leave his equations out of it. As for QED and the Standard Model, the things people say about them will be proved wrong by experiment.
Displacement current tells you they have direct interactions.
Duh. The experimental data from your photon-photon collider will show you that two photons interact.ben m said:
Feynman said nobody understood why it works. It didn't explain anything. 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. That's cargo-cult science. And that turbine hum you can hear is Feynman turning in his grave.
No. It's pointing out tautological nonsense.ben m said:
Not me. I tell you what Einstein said or what Minkowski said or what Maxwell said or what Thomson and Tait said. And I tell you about the hard scientific evidence. You just dismiss it all.ben m said:
I don't believe it. Your physics knowledge is just so weak. 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.ben m said:
He said one of the photons becomes a virtual electron and a real electron. You know, via that little thing we call "magic"? Well whaddya know, pair production has occurred! Then he said the other photon runs into that virtual electron. But do we get Compton scattering? Apparently not. What we get is more magic. 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. Magic!
No, not magic. Cargo-cult trash. And you defend it.
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Perpetual Student
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Mr. Duffield, your ignorance of particle physics, QED and QFT is palpable.
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