Merged Relativity+ / Farsight

[edd]

Yes. Note though that a Falaco soliton is a better analogy than a whirlpool. It's like half a smoke ring, but in water. Thomson and Tait experimented with smoke rings. And it was they who introduced the phrase "spherical harmonics".

So your justification for one analogy being useful and predictive of a quantitative result is to say that another analogy is better, make an analogy to that analogy, point out that some other people did experiments on that analogy to an analogy that's better than another analogy, and that they once named a piece of mathematics that is useful in some other situation?

Great, I'm convinced. How about the rest of you guys?

 

[Farsight]

And again let's hear it from Maxwell and Minkowski:

"A motion of translation along an axis cannot produce a rotation about that axis unless it meets with some special mechanism, like that of a screw.

"In the description of the field caused by the electron itself, then it will appear that the division of the field into electric and magnetic forces is a relative one with respect to the time-axis assumed; the two forces considered together can most vividly be described by a certain analogy to the force-screw in mechanics; the analogy is, however, imperfect."

And let's hear it from Wikipedia:

"In the past, electrically charged objects were thought to produce two different, unrelated types of field associated with their charge property. An electric field is produced when the charge is stationary with respect to an observer measuring the properties of the charge, and a magnetic field (as well as an electric field) is produced when the charge moves (creating an electric current) with respect to this observer. Over time, it was realized that the electric and magnetic fields are better thought of as two parts of a greater whole — the electromagnetic field."

The electron has one field, edd. Not two. A motionless electron doesn't have an electric field, and you don't "create" a magnetic field when you move past that electron. The field it has is an electromagnetic field, and my depiction resembles other images you've seen of a vector field for good reason.

 

[edd]

Ok why don't you write down a mathematical expression for the electromagnetic field of a stationary electron that shows some useful vector quantity spiralling out of it? That's be more useful than posting a picture of a pair of spirals with no further useful description.

 

[tusenfem]

I can think of no reasonable way in which that depiction is correct.

Well it would be correct if you could just add E and B into one field line, which you for obvious reasons cannot.

 

[ctamblyn]

I know all that Tim.

I find that remarkably difficult to believe, given the following statement:

As ctamblyn said, you can use this definition to claim that there's a field in your bathtub.

W.D.Clinger and I both pointed out the problem with the definition Tim quoted, in the posts that followed: it was from abstract algebra, not physics. It was for a totally different type of "field". It's about as relevant as the agricultural definition as far as the present context goes.

A charged particle q1 doesn't have an electric field, ...

Nonsense.

 

[tusenfem]

"A motion of translation along an axis cannot produce a rotation about that axis unless it meets with some special mechanism, like that of a screw.

One should keep in mind that this quote comes from the chapter "Part IV: The theory of molecular vortices applied to the action of magnetism on polarized light." from the book "The Scientific Papers of James Clerk Maxwell, Volume 1". It is just a cherry picked quote from a larger informative paragraph which in and off itself cannot be taken at face value to mean anything in the way it is presented here.

 

[sol invictus]

Sol: see Jackson section 1.2 where he says "Although the thing that eventually gets measured is a force" and "At the moment the electric field can be defined as the force per unit charge acting at a given point".

Force per charge - not force. So you were wrong, as always.

More importantly, the way you measure airspeed or wind is by the force air exerts on some object or device. Does that mean that air/wind is "just a force"?

Lastly, you're still trying to argue that E is just a force, but the EM field strength tensor is something different. That is patent nonsense, because the components of E are components of of the field strength tensor. Furthermore it's a trivial exercise to show that if the EM field strength F_ij is a 4-tensor field, E (meaning the set (F_01, F_02, F_03)) is a 3-vector field.

 

[ben m]

Well it would be correct if you could just add E and B into one field line, which you for obvious reasons cannot.

Unfortunately, based on previous experience in this (?) thread, that's exactly what Farsight wants to do. He has previously posted a picture of a 2D spiral which he described as the total field of an electron in the equatorial plane.

 

[ben m]

I've never said I think QFT or wave equations are gibberish, and no way have I been "insulting anyone who cites QFT in any way". Please try to stick to the physics instead of casting aspersions.

Huh. Then what's this?

No, yours does, along with your conclusion, because we can diffract electrons. How can you diffract a point particle ben? How can a point particle spin? How in an atomic orbital can a point particle exist as a standing wave? Magic? Quantum mysticism that defies all human understanding?

Yes. Note though that a Falaco soliton is a better analogy than a whirlpool. It's like half a smoke ring, but in water.

Why do you say "yes"? A 1/q^2 scattering cross section is a very specific mathematical prediction, and I don't see what equations you used to make the prediction. (Unless your method was (a) "Wait for ben_m to tell you what the experimental data says, and (b) claim that your theory predicts that.)

Well, there's plenty more where that came from. How about electron-neutrino scattering? Two point particles, right? But in this case the energy dependence is experimentally NOT 1/q^2. How about electron-photon scattering (Compton scattering)? Again, experimentally not 1/q^2. Since you've suddenly developed a secret method for calculating cross sections, let's run your method through its paces. I await your predictions.

 

[Perpetual Student]

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The electron has one field, edd. Not two. A motionless electron doesn't have an electric field, and you don't "create" a magnetic field when you move past that electron. The field it has is an electromagnetic field, and my depiction resembles other images you've seen of a vector field for good reason.

Think man! The expression F=qE is a field equation. It is a mathematical description of the condition of space due to the field E, which results in a force on the point charge q. Consequently E is a field -- by definition. Stop all the quote mining and look at the math -- the answer is there!

 

[Farsight]

Huh. Then what's this?

What that is, is me pointing out the hard scientific evidence that demonstrates that the electron is not a point particle. The Schrodinger equation is a wave equation. I say yes to 1/q² because it relates to the Coulomb's Law.

Force per charge - not force. So you were wrong, as always.

Oh that is such a thin-gruel nitpick, sol. I've already given the expression:

where q1 and q2 are charge in Coulombs. Neither of the particles concerned has an electric field. They both have an electromagnetic field. When they have no initial relative motion the mutual force on each of them is linear, and this force is the result of electromagnetic field interaction.

...It is just a cherry picked...

And the Minkowski quote was just cherry-picked, and the Einstein quote, and so it goes. Take a tip from me: when somebody airily dismisses what Maxwell / Heaviside / Minkowski / Einstein etc said as "mere cherry picking", be skeptical.

 

[Farsight]

Think man! The expression F=qE is a field equation. It is a mathematical description of the condition of space due to the field E, which results in a force on the point charge q. Consequently E is a field -- by definition. Stop all the quote mining and look at the math -- the answer is there!

What? There is no force unless you've got two charged particles. The mutual force depends on their separation. And their charge too, but we usually keep it simple and talk about electrons and positrons which have "unit" charge. And neither of them are point particles. You cannot set up an "electric field" without using charged particles. And you cannot set up an electric field which doesn't appear to be a magnetic field when you move through it. E is not a condition of space. If it was, you would only see linear force when you threw one charged particle past the other, and you don't.

This is getting bizarre, guys. Who will step up to the plate and say Farsight is right about x?

 

[edd]

This is basically like saying there's no such thing as energy because particles have four-momentum, then.

 

[Perpetual Student]

We have:

F=qE

F=qvxB

and:

F=q(E+vxB)

all three are called "field" equations.

Farsight: 8..., 9..., 10 -- you're out!

 

[Perpetual Student]

What? There is no force unless you've got two charged particles. The mutual force depends on their separation. And their charge too, but we usually keep it simple and talk about electrons and positrons which have "unit" charge. And neither of them are point particles. You cannot set up an "electric field" without using charged particles. And you cannot set up an electric field which doesn't appear to be a magnetic field when you move through it. E is not a condition of space. If it was, you would only see linear force when you threw one charged particle past the other, and you don't.

This is getting bizarre, guys. Who will step up to the plate and say Farsight is right about x?

Consider a stationary charged plate, particle, whatever (it does not matter) and it's associated electric field E(x,y,z). Now a stationary particle with the charge q(x,y,z) will experience a force F(x,y,z), where (x,y,z) defines a position in space. That's it:
F=qE

It's called a field equation. Good grief!

 

[AlBell]

I begin to pity those who respond to Farsight.

 

[Perpetual Student]

I begin to pity those who respond to Farsight.

 

[Farsight]

This is basically like saying there's no such thing as energy because particles have four-momentum, then.

No it isn't, and I'll use this to illustrate my point. See on wiki where p₀ is given as E/c?

Consider a cannonball in space, moving at 10m/s towards you. What you've been saying about electromagnetism is like saying "a cannonball has momentum and it has kinetic energy, and I can take away the momentum whilst leaving the kinetic energy unchanged". You can't. You can apply a force to bring that cannonball to a halt. Its kinetic energy is essentially force x distance, its momentum is essentially force x time. You convert from distance to time using c, which is distance/time. That cannonball's momentum and its kinetic energy are nothing more than two aspects of its energy-momentum. You can't have one without the other, and so it is for the electromagnetic field. Hence no magnetic monopoles.

And get this: an electron at rest has energy 511keV, and because we know that what we're really dealing with is energy-momentum, we know that that that it has momentum too. And we also know that that momentum is hidden. We call it spin angular momentum, and the Einstein-de Haas demonstrates that "spin angular momentum is indeed of the same nature as the angular momentum of rotating bodies as conceived in classical mechanics". We don't talk about spinors for nothing. Here's a picture of a BEC spinor. Familiar, isn't it? See the mention of knots and topological charge. Ooh, and look at that blue torus on the Edinburgh TQFT page. Are you getting the picture yet edd?

Right, I have to go. Bye for now.

 

[Kwalish Kid]

And the Minkowski quote was just cherry-picked, and the Einstein quote, and so it goes. Take a tip from me: when somebody airily dismisses what Maxwell / Heaviside / Minkowski / Einstein etc said as "mere cherry picking", be skeptical.

But you are demonstrating that you are never skeptical. You make claims that practicing physicists and cosmologists point out are grossly incorrect, you defend these claims with very small, non-technical passages, people note that you are cherry-picking, yet you stick to the belief that you formed on the basis of a small portion of the non-technical work of scientists.

Shouldn't a skeptic look to the technical parts of a technical work to understand it, rather than a very small portion of the non-technical writing that accompany the technical work?

 

[Perpetual Student]

No it isn't, and I'll use this to illustrate my point. See on wiki where p₀ is given as E/c?

Consider a cannonball in space, moving at 10m/s towards you. What you've been saying about electromagnetism is like saying "a cannonball has momentum and it has kinetic energy, and I can take away the momentum whilst leaving the kinetic energy unchanged". You can't.
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You are so focused on being right that you do not pay attention to what is being said. You have totally missed the point!
You can analyze the energy and do calculations regarding the energy of your cannon ball while disregarding the momentum -- if an analysis of the energy yields useful results in the context under consideration. That does not "take away the momentum." We are merely not looking at he momentum while doing some mathematics regarding the energy.
When using F=qE ( a FIELD equation), we are doing something similar. As long as E and q are stationary that's all we need. Stop quote mining and think, man!