Explanations In Physics

From CasimirEffect

Is there a sensible explanation for everyday electromagnetic attraction? Why do repulsion and attraction have greatly different explanations?

To explain repulsion all you need to do is draw a Feynman diagram with two electrons swapping a photon. The photon conveys momentum between them. If you draw the same diagram for attraction, what's the photon supposed to convey ... negative momentum? Yeah right! (This could actually make sense except that 1) nobody has broken down and admitted that's what's happening, and 2) you'd need to explain why it conveys positive momentum in some cases and negative momentum in others.)

Note also that the Casimir Effect in no way explains electromagnetic attraction. Electromagnetic attraction is a far more powerful force than the Casimir effect by many orders of magnitude and varies with the second, not the fourth power of distance. In fact, the calculations for the Casimir effect assume infinitely large parallel plates in order to get rid of edge effects. Those calculations simply don't apply when the two "plates" you're talking about are all edges (i.e., particles).

By way of comparison, the explanations for electromagnetic repulsion and color attraction are simple and elegant. The explanation of color attraction is similar to the Casimir effect; the energy density inside nucleons is so high that it causes the vacuum to change, to become a simple vacuum (ie, different from the ordinary vacuum), which does not push against color-charged objects. Since the color force is extremely powerful, the inwards pressure on colored particles is extremely high. But that doesn't explain electromagnetic attraction.

There simply isn't any good explanation for electromagnetic attraction. That's right, an everyday familiar phenomenon like electromagnetic attraction has no explanation that most people can understand. Do people care? No, they do not. They'd rather ooh and aah over an unfamiliar but perfectly trivial phenomenon like the Casimir effect rather than scratch their heads over something that's a trillion times more important.

[Fundamental forces are mediated by GaugeParticles?:

Force Particle ----- -------- Electromagnetism Photons (observed -- literally) Strong Force Gluons (measurements consistent with theory) Electro Weak Z & W (measurements consistent with theory) Gravity Graviton (predicted spin-2 boson)

These are all Bosons - Higgs is another (spin 0) - supposed to give particles mass and the subject of intense search

http://www.exploratorium.edu/origins/cern/ideas/standard4.html]

The goal of GrandUnifiedTheory(ies) is to explain the first three as aspects of a single force that became differentiated as the universe expanded. Only a TheoryOfEverything (which now includes only the theory formerly known as superstrings as a lone contender) attempts to account for all four forces. See also the skater analogy for attraction and repulsion in in GravityWorks]

[Ramblings about basic issues in physics research deleted. Note: LQG is not a GrandUnifiedTheory since it does not include the electroweak or strong nuclear forces.]

Gluons on the other hand are a good model that is part of the standard theory that has been very consistent between predictions and measurements, but we're only barely scratching the surface of the high energy regimes necessary to consider them to be quite as good an approximation to reality as are photons.

Gravitons on the other hand have zero measurements, let alone ones that are consistent with theory.

Gravitons are necessary because they come out as a result of quantizing gravity. Quantizing gravity is necessary because Many-Worlds requires it. Many-Worlds is the only theory of QM that is 1) meaningful, 2) self-consistent, and 3) consistent with reality. Gravitons exist as surely as QM is correct.

  CasimirEffect:      VirtPhoton?--->Plate1   Plate2<---VirtPhoton?
  FundamentalForce?:   Particle1<-----(GaugeParticle?)----Particle2

Almost like a message between objects in programming. GaugeParticle? "sent" from Particle2 to Particle1 "tells" them to come together if it is an attractive force, or "go apart" if repulsive.]

Except that this is crap. See above about negative momentum.

[Compare

And Robert Walgate's skater analogy of how Boson exchange can mediate attraction and repulsion (gets around negative momentum issue): Page 4 of http://www.commonsensescience.org/pdf/process.pdf - "...in QM, which affects small-scale phenomena, there is a strange extension and delocalization of events that allows a seemingly impossible event: one skater throws the ball away from the other, in the opposite direction, but the other skater is still able to catch the ball. A little thought shows that if such events were possible, as they are in the world of elementary particles, they would cause an attractive force between the skaters." ]

: How can someone read about negative momentum and then claim that's not what they're reading, that the handwaving non-explanation they're reading "gets around" negative momentum? How can someone claim that an absurdity (absorption of a photon at a distance) adequately "gets around" something that's LESS absurd (negative momentum)? How can people be so stupid?!
: What we have here are fanboys of physics. People who suspend their disbelief, who suspend their critical faculties and reason, just because what they're reading is about physics. What kind of world do we live in that scientists, who are supposed to EXPLAIN the universe, are given carte blanche to say any absurdity they want, that they're not required to be LUCID so long as they appear authoritative. What is it with people's fetish with authority? Don't you guys realize that these are MORONS you're worshiping?
: Note, it's okay to be a fanboy of physics ... if you're 16.
: [You basically called negative momentum absurd above ("no one whas broken down and admitted...") now you are saying it is less absurd than topologies at the quantum scale that would allow bosons to be transferred with positive momentum. You accept uninuitive trajectories of particles as seen at the bottom in other contexts - "a photon can zig-zag across half the universe and back to the Big Bang, before it reaches its destination a centimeter from its origin" instead of dismissing the claims above carte blanche why not investigate and see what basis Walgate has for his statements? Do they contradict a many worlds framework? You are looking for an explanation and have found none to date: "...EM attraction has NO EXPLANATION " why blind yourself to answers from others who have examined the question in more detail?]
: I skimmed the paper and there is no explanation. In many-histories, a photon that zig-zags across the entire universe suffers the consequences for doing so. Not only that, but these consequences and how they're triggered are precisely spelled out. Photons rotate in the complex plane and the longer their trip, the more they rotate and interfere with each other. Finally, it isn't that a photon can go across the universe and back, but that it DOES and every other path simultaneously. So everything that happens is spelled out in excruciating detail.
: The paper doesn't look like it was supposed to give an explanation. Given that it claims all forces are electromagnetic and that relativity has problems with time, I don't think it's exemplary of modern physics. It's somewhat amazing it was brought up - it would be a strawman if you were the one who used it as an example. -JG

[The link itself seems critical of boson exchange but the point was to highlight the Walgate quote (being referenced by the author of the link). Was not able to find that quote directly so had to settle for that reference. Here is a bit more explanation from a different link and diagram also supporting attraction as a process involving bosons being generated "away" from the fermion (electron in this case) and being received from the opposite direction due to the uncertainty principle:

From http://www.egglescliffe.org.uk/physics/particles/parts/parts1.html ]

Negative momentum isn't that absurd because all it requires is for photons to have negative energy, which is an already used as an explanation for black hole radiation. However, I still don't understand a photon, or any other particle, having negative energy. But a particle emitting a photon to the left and another particle absorbing it to the right of it, that's just absurd. This isn't a "topology" issue and it's not a question of the photon taking a strange path, this is a complete breakdown of the concept of dimension. When you completely break down one of the three fundamental concepts of physics (energy, dimension, information), you're done for.

Not sure why negative energy is confusing or why it enters into things here, since the only real connection is the interval, which involves the squares of both. If memory serves, what matters here is that the momentum of a photon is not connected to its velocity. I will double-check, if you give me time. I can say that photons are not spherically symmetrical (being vector bosons), and it's that degree of internal freedom that accounts for the different responses. A full explanation of the coupling, however, is still hidden within the mathematics. -JG

You're right, I confused negative energy with negative mass. And negative mass has no relation to black holes, but to tachyons.

Imaginary mass relates to tachyons. Negative mass and energy relate to virtual particles, which thinking about it is probably what the page was referring to. If we take an ordinary electron-positron pair:

... - + ...

...except draw in the virtual electrons, so we only have to worry about one kind of interaction:

 ...   -       ...  Real stuff (+ve energy levels)
 ...------- ---...  Virtual stuff (-ve energy levels)

It should be clear that the electrons are all going to be pushed towards the hole, i.e. the positron, with the net result that the electron and positron are attracted. The virtual photon mentioned above doesn't occur in this description, but that's ok, because the EM field also involves an infinite number of other interactions. If you subtract the field without the real particles from the field with them, it's what you'd be left with. In this context, it has negative momentum because it's not an interaction, it's a difference of interactions.

Of course none of this actually works, since it has an infinite number of particles exerting forces in all directions, and these are just supposed to almost cancel. Plus it really ignores the symmetry between electrons and positrons. But real descriptions, in terms of quantum field theory and its successors, are either complex or presented poorly. Maybe this is enough to give some idea as to what's going on? Thinking about it, it's similar to your description of colour attraction - near positrons, the vacuum is changed so as to not push so hard against electrons.

I've known about that explanation of EM attraction for a very long time. First, this is not an explanation that most people would understand. Second, there still lacks an explanation for why EM attraction is so very much more complicated than EM repulsion. Finally, not only is the gross asymmetry disturbing, but it's absolutely revolting how physicists and any books on physics gloss over the difference between the two. They're simply evil sons of bitches in my book.

On the first, I don't think you're giving people enough credit. This is the same explanation as why electrons and holes attract in semiconductors, which people have no trouble with in elementary school. "A missing electron, with respect to the background, behaves like a particle with opposite properties to an electron - what repels electrons attracts it, and what attracts electrons repels it." Actually thinking about it, that explanation will carry over to the field version. A positron is negative one electrons, so should experience forces reversed, just like two electrons will experience forces doubled. No gross asymmetries, but leaves out the tricky part of deciding such things exist.

I'm not going to defend the approach taken by physics books, on this or much else. They're mostly written with a calculation-is-what-counts attitude that makes them all but useless for anything else. Unfortunately, such an approach is self-sustaining.

On a different subject, I always got the impression that colour attraction was something more fundamental than just the vacuum getting polarized. The term 'simple vacuum' seemed to imply it was something very different from a normal vacuum. And I've never thought of QM as background independent ....

And getting to tachyons, I recall an explanation for why negative mass is impossible based on classical mechanics. Any particle with negative mass would immediately accelerate to infinite velocity because its acceleration would make its energy go down to negative infinity, minimizing it.

Negative mass can't be ruled out in a coherent relativistic theory. In order to stop particles from accelerating infinitely, you have to assume all the higher velocity states are full. That's where virtual particles come from.

At a quick glance that looks like a good refactoring, Richard, aside from your usual gratuitous vitriol, and aside from your religion about ManyWorlds?. Check again; it is not a theory, it is a philosophical interpretation. This is a terminological issue, notice, because it is just a device for making intuitive sense of the actual theory of QM. It is not a theory because it makes no positive nor negative predictions even in principle, nor is there any way, even in principle, to distinguish it from the other 3 interpretations of QM.

I wasn't going to get into it, but what the hell: I noticed a few weeks ago some stuff you wrote that indicates that you simultaneously believe in modern entanglement theories. This is a contradiction. Entanglement and its related issues are indeed a theory, and as such in fact replace the older 4 interpretations of QM. By OccamsRazor, those interpretations are no longer necessary now that we've got a theory.

Many Worlds makes predictions that conflict with other theories. These include quantum computation, quantum erasure and gravitons. Many Worlds requires gravity be quantized, other theories do not. Many Worlds also predicts parallel universes, as does General Relativity, and this is yet another thing that makes sense. Many-Worlds is the only theory that actually predicts what happens at a quantum level. Many-Worlds is just chock-full of predictions, you just have to know what shape these predictions take.

Many Worlds isn't a philosophical interpretation, it's the only physical theory consistent with philosophy by virtue of being a physical theory (a theory of real physical objects). That's not quite the same thing.

In fact, it goes much deeper than that because QM without MW isn't a physical theory at all, just a bunch of meaningless math. MW is the theory, the thing that talks about the Real World, and QM is just its expression in mathematical language. The whole notion that an "interpretation" is superfluous, unnecessary or "philosophical" is idiotic. QM makes NO predictions, it's MW that makes ALL the predictions for it. It's not QM that's been experimentally verified to the 10th decimal place, it's MW. You can no more experimentally verify QM than you can experimentally verify that 2 + 2 = 4.

: The above pargraphs tries to hide the tacit but contentious assumption that philosophers and philosophical interpretation should have some kind of primacy over the activity of physicists (or pretty much everybody esle, including mathematicians). This is in contrast with the overwhelming consensus of both mathematicians and physicists expressed quite clearly by Feynman: "shut up and calculate". RK has nowhere near the authority to impose his contentious assumptions , and call other people MORONS because they do not subscribe to his personal philosophy.
: Interpretation isn't philosophical, it's physical. It's what distinguishes physics from math. So it's quite ironic that you call upon mathematicians as authorities on what physics is all about!
: Further, Feynman said "shut up and calculate" in response to all the morons swallowing the absurd non-explanation that is Copenhagen (either version of it). Feynman himself bought into Many-Worlds, as do all cosmologists today and anyone else who can't afford to "shut up and calculate". And from the proportion of physicists going on the superstrings bandwagon, it seems that nobody wants to just "shut up and calculate".
: So I have plenty of authority behind me when I say that a set of math equations isn't a physical theory until you've given it an interpretation. And this wouldn't be contentious at all except that, you guessed it, people are morons.
: The only interpretation you need is being able to predict observable phenomena based on calculations, but if you want that interpretation to go into metaphysical stuff like "negative momentum is more real than " whatever, or that the many worlds which you did not have a conclusive test for are more "real" than other explanations, then that's personal philosophy. As long as the equations of QM are confirmed by reality, they are a lot more than meaningless math, regardless of their philosophical interpretation.
: Logical positivism is dead and dying. Are you seriously telling us that anything beyond the observable universe simply doesn't exist because we can't ever observe it? That quarks don't exist because we can't observe them directly? That the curled up dimensions of superstrings are less real than the large ones? Can you really not understand how the "philosophical interpretation" you disparage is the only link between a bunch of meaningless equations and reality? Do you really think the mapping between equations and reality begins and ends where your imagination does, that you can dismiss anything you find inconvenient as a "mathematical construct" while denying that your intuitive interpretation is in fact interpretation? Do you really defend absolutely horrible, centuries-obsolete, metaphysics and philosophy of science while you show contempt for all philosophy? No need to answer, it's rhetorical.
: Logical positivism isn't a solution. It's a problem. It's a knee-jerk reaction to every paradigm shift. You observe something that doesn't make sense and suddenly you're surrounded by scads of no-brained mystics who go on and on about how nothing should make sense. Who say, as if this were something deep instead of risibly superficial, that only observations matter. Logical positivism was the reaction to Einstein's overturning of Newtonian space and time. Logical positivism was the reaction to quantum mechanics' overturning the notions of definite point-particles. The former is long dead, we've passed through that stupid fad by getting a solid intuitive grasp of general relativity. The latter is something else entirely.
: It's taken us nearly a century for logical positivism to start to die down with respect to quantum mechanics. And why? Because physicists *insist* on teaching *obsolete* classical mechanics! Because they insist on not being overshadowed by the new generation, by stopping them from developing an intuitive grasp of quantum mechanics. And that's how we end up with morons who think that wavefunctions aren't real, that quantum multiplicity doesn't apply to the macroscopic world, that quantum "indeterminacy" is a meaningful notion that can replace multiplicity, that interpretation of mathematical equations (ie, PHYSICS) is a matter of "personal philosophy". Logical positivism is turning off your brain. Logical positivism is a weapon to neutralize the idiots out there *in positions of authority* who can't be made to understand the new physics. Logical positivism is a disease. Logical positivism has gone out of control for a whole goddamn century! Logical positivism is the enemy of real science. That's how we've ended up with entanglement having been dismissed as a curiosity for almost an entire goddamned century. Logical positivism was never fucking worth it.
: Richard, first of all you throw more philosophy at us, and that we can only disdain. Second, you're doing it so badly it's just about lame: in three paragraphs of slur against something called "logical positivism" you managed not to bring a single argument against it. Why don't you take your rant against logical positivism on a separate page and construct a proper argument as to what are the problems with logical positivism. That should be an interesting exercise.
: [He already gave a number of examples where it leads to absurd conclusions. If you inherently disdain any and all philosophy except the one you've decided to cling to, without looking at it, that's your failing and not his.]

The common attitude towards many-worlds is very reminescent of creationists' claims about evolution, wherein lots of idiots claim that evolution has no predictive or explanatory power. Of course, this is false.

Entanglement isn't a theory, it's a phenomenon. It in no way replaces many-worlds, it's a small part of it. Entanglement does replace idiocies like the Heisenberg Uncertainty Principle (as originally formulated), but these were ideas created by idiots for idiots, for people who never understood quantum mechanics and had no intention to ever do so.

And far from Many-Worlds being obsolete, it is the standard interpretation of superstrings. Pay special attention to the similarity between Feynman's explanation of many-histories and to superstring theorists' explanation for why there's always a brane handy to wrap around any tear in spacetime.

Well, I'm talking about the original Many-Worlds interpretation...in terms of that, there was no way even in principle to detect the presence of those other worlds. That's an example of what I meant.

So what? Do you have any way even in principle of directly observing a quark? No, you do not. Do you have any way even in principle of observing an inflaton? I don't think so. These things exist because they are entailed by the only theory that makes sense of observation. There is no sensible theory of subatomic particles that doesn't have quarks. There is no sensible theory of physics that doesn't include parallel universes. They exist and that's all there is to it. So live with it and don't complain when a perfectly good theory of physics (MW) has that feature just because other retarded theories do not.

And since when did you give up on atomic theory just because it predicts the existence of things (atoms) you will never, ever see? For that matter, when did you stop believing in a large universe of 10^78 particles just because you'll never see most of those particles? Come on, OccamsRazor (eliminating conceptual objects from theories, not physical objects) is basic philosophy of science! How come most people screw up philosophy of science so badly? It's really not that hard.

If you're talking about an update of it in terms of String Theory/M-theory, then I'm not familiar with that. When I've spent time on such things in recent years, I've concentrated on the spin-networks/foam side of things rather than on the string theory side, since the math seemed so unapproachable over there. (Not that I can always follow spin-network math, either, but... :-)

No update. The explanation for why there's always a brane handy to wrap around any discontinuity in spacetime is because one can warp there from across the universe in an instant, wrap the tear, then zoom back where it came from. Just like in Feynman's many-histories, a photon can zig-zag across half the universe and back to the Big Bang, before it reaches its destination a centimeter from its origin. We don't see it because this all cancels out. And the same for FTL branes ... except around tears in spacetime.

Forgive my ignorance for a moment... Is there a known disbalence between electromagnetic attraction vs repulsion? i.e., Two magnets, if appropriately aligned, will push away from each other with a force that is not equal to their attraction if their poles are reversed? --WilliamUnderwood

No. Why do you ask?

I don't remember off hand; I think it was an explanation of gravity I came across somewhere, but I don't remember the reference, or any of the specifics really. --cwillu

That sort of thing tends to be impossible for direct and simple reasons, such as that it would tend to imply a non-zero contour integral (usually "lines of force" terminate neatly in magnetic poles or electric charges), which is a contradiction in terms under most conditions. Contriving a space where it wasn't self contradictory, it would at minimum still be a non-conservative system. Perpetual motion and "free energy" might sound nice, but then you wouldn't have a stable universe. http://www.answers.com/topic/path-integral -- DougMerritt