The nature of the magnetic field.

[peron]

QED states that the magnetic field is a kind of "photon lattice" and the force we feel when a magnet pulls of something is the exchange of these virtual photons. But I become confused right about here, if the magnetic field is virtual photons, which are themselves wave packets of magnetic and electric fields.

Is the magnetic field with in a photon made out of more photons? OF course this can't be, so I'm obviously missing a key part of the theory, please can someone explain?

 

[billbray]

I'd like to see some answers to this one as well...

 

[Antiphon]

The photon is a quantum of the field. They are what the fields are made of.

There are no magnetic or electric field in the photons. If there are EM fields, there are photons.

 

[peron]

The photon is a quantum of the field. They are what the fields are made of.

There are no magnetic or electric field in the photons. If there are EM fields, there are photons.

So then what is a EM field?

 

[Phrak]

I think you are asking what is a classical electromagnetic field. Quantum electrodynamics is a theoretical construction designed to replace the classical theory.

 

[peron]

I think you are asking what is a classical electromagnetic field. Quantum electrodynamics is a theoretical construction designed to replace the classical theory.

I apologize if I wasn't clear, my question was concerning the quantized view of the magnetic field in Quantum Electrodynamics. In QED, as I have come to understand, the magnetic field is nothing more than a "photon field" of sorts. But photons themselves are made out of magnetic fields.

I believe that I might be missing some big piece of the puzzle. So, what does Quantum field theory really say about magnetic fields?

Thanks.

 

[tiny-tim]

Hi peron!

QED states that the magnetic field is a kind of "photon lattice" …

… In QED, as I have come to understand, the magnetic field is nothing more than a "photon field" of sorts. But photons themselves are made out of magnetic fields …

i] QED doesn't talk of the magnetic field … it talks of the electromagnetic field (of which the magnetic field is simply a component)

ii] can you tell us which book you got these statements from, and/or provide a link? …

… and the force we feel when a magnet pulls of something is the exchange of these virtual photons.

iii] a photon "is" an electromagnetic field, with E.B = E² - B² = 0

iv] an electromagnetic field is sometimes said to be "mediated" by the photon, and to involve the "exchange" of both virtual photons and virtual electrons, but that is a mathematical description rather than a physical one.

 

[peron]

Hi peron!



i] QED doesn't talk of the magnetic field … it talks of the electromagnetic field (of which the magnetic field is simply a component)

ii] can you tell us which book you got these statements from, and/or provide a link? …


iii] a photon "is" an electromagnetic field, with E.B = E² - B² = 0

iv] an electromagnetic field is sometimes said to be "mediated" by the photon, and to involve the "exchange" of both virtual photons and virtual electrons, but that is a mathematical description rather than a physical one.

http://en.wikipedia.org/wiki/Magnetic_field#Quantum_electrodynamics"

These theories explain that the electromagnetic field is derived from the photon field; indeed, all electromagnetic interactions are mediated by this field. The most accurate modern description of the electromagnetic interaction (and much else) is Quantum electrodynamics (QED),[19] which is incorporated into a more complete theory known as the "Standard Model of particle physics".

Ok, I have just become even more confused. What is the magnetic field then?

 

[tiny-tim]

http://en.wikipedia.org/wiki/Magnetic_field#Quantum_electrodynamics"

Ok, I have just become even more confused. What is the magnetic field then?

The magnetic field is three of the six components of the electromagnetic field.

The electromagnetic field is a 2-form (a vector is a 1-form), and has 6 components labelled xt yt zt xy yz and zx (a vector of course has 4 components, labelled t x y and z).

The xt yt and zt components are the electric field, and the xy yz and zx components are the magnetic field.

wikipedia's statement that "the electromagnetic field" (btw, not "the magnetic field") "is derived from the photon field" is both vague and weird … it certainly isn't a combination of photon fields.

What about "photon lattice" … where did that come from?

 

[jfy4]

The electric and magnetic fields in the classical sense were entities in and of themselves, in the full sense, they were just that. Then as time progressed it could not help be noticed that the interactions taking place in the realm of electricity and magnetism were happening at the speed of light. Then the speed of light showed up in the E&M wave equation. Promptly thereafter light was decided to be made up of electric and magnetic waves oscillating.

Then Quantum arrives. The quantum field theory of the electric and magnetic fields in the radiation gauge ends up yielding a particle that resembles in every way, a photon. Thus, history, and physics must be rewritten, in a sense, and there never was an electromagnetic field in the sense that it was a unique entity, it was light all along!

Therefore do not get hung up on classical/quantum mix-ups such as a recursion where the electric/magnetic fields are made of photons, but photons are made of electric and magnetic fields, but electric/magnetic fields are etc... the convenient but ultimately unsatisfactory theory of classical electrodynamics must be circumscribed by a new theory, QED, of which we should extract the most current and almost canonical physics from.

 

[peron]

The magnetic field is three of the six components of the electromagnetic field.

The electromagnetic field is a 2-form (a vector is a 1-form), and has 6 components labelled xt yt zt xy yz and zx (a vector of course has 4 components, labelled t x y and z).

The xt yt and zt components are the electric field, and the xy yz and zx components are the magnetic field.

wikipedia's statement that "the electromagnetic field" (btw, not "the magnetic field") "is derived from the photon field" is both vague and weird … it certainly isn't a combination of photon fields.

What about "photon lattice" … where did that come from?

So, the photon isn't made out of perpendicular magnetic and electric fields? And the electromagnetic field isn't made out of photons? So what is the magnetic field made out of?
I know I'm asking a What is? question which aren't really answered in science, like What is space?, but the magnetic field exists and it must be made out of something, I want to know what that something is.

 

[Vanadium 50]

QED states that the magnetic field is a kind of "photon lattice"

I don't think it says anything like that. That may be the source of your confusion.

 

[peron]

I don't think it says anything like that. That may be the source of your confusion.

I really want to learn this stuff, can anyone give me good places to go to to read this stuff? I would really appreciate that, thanks. :)