# Is an electron an excitation in a magnetic field?

1. Oct 31, 2012

### CraigH

I didn't really know how to word this question, but what's confusing me is this: I was researching "what is an electron" and I read in many places that "an electron is an excitation in a magnetic field". But what does this mean? I thought that an electron is just a particle with mass and charge, and when a charge moves it creates a magnetic field. What does "an excitation in a magnetic field" mean?

Also does this mean that an electron could be created out of nowhere from a magnetic field? (I know mass cannot be created or destroyed but e=mc^2 so the mass would come from the energy)

Thanks!

2. Oct 31, 2012

### JustinRyan

I do not think this is correct. That description would fit a photon, but not an electron.

3. Oct 31, 2012

### JustinRyan

Mass can be created and destroyed. Electrons can be created but only with its anti-particle (positron e+), otherwise that would violate the conservation of charge.

4. Oct 31, 2012

### Staff: Mentor

Mass is never created or destroyed, only transferred from one place to another in different forms. (Just like energy)

5. Oct 31, 2012

### Staff: Mentor

Could you share a few links with us so we can see where you got that information from?

6. Oct 31, 2012

### JustinRyan

"The energy of this photon can be converted into mass through Einstein's equation E = m c2"

http://en.wikipedia.org/wiki/Pair_production

7. Oct 31, 2012

### Staff: Mentor

Ah, here we run into the problem of what "mass" means. Measure the mass of the system that includes the photon and atom, then measure the mass of the system after the photon has been converted into an electron-positron pair. The mass has not changed. This is because energy has mass, per the equation you linked, so the photon contributes to the mass of the system. However, at the same time, matter can be destroyed and created, and matter has invariant mass while photons do not. So yes, if we talk about invariant mass you would be correct, it can be created and destroyed when particles are.

8. Oct 31, 2012

### Khashishi

A photon doesn't have invariant mass, but a pair of photons can have invariant mass.

9. Nov 1, 2012

### ImaLooser

As far as I understand it, (not far), according to quantum field theory an electron is an excitation of the electromagnetic field. As to exactly what this "means" you would have to get a graduate degree in physics (which I do not have either). It is worth noting that some particles like neutrinos are NOT excitations of the EM field, and hence as far as they are concerned electrons and protons and neutrons might as well not be there at all.

In EM fields of a quadrillion gauss in a vacuum, electron-position pairs will be spontaneously created.

10. Nov 1, 2012

### andrien

No,it is photon which arises as a quantum of excitation after quantizing the electromagnetic field.

11. Nov 1, 2012

### mikeph

What's the source? It sounds very wrong.

12. Nov 1, 2012

### ZapperZ

Staff Emeritus
This is insufficient to start a topic. You have neglected to clearly cite your source. "Read in many places" is not a valid reference.

https://www.physicsforums.com/blog.php?b=2703 [Broken]

And I am thoroughly puzzled that there were so many responses to something like this without even checking if the starting point is even valid.

I strongly suggest we hold off further discussion on this till the OP comes back and provide these sources that we can check.

Zz.

Last edited by a moderator: May 6, 2017
13. Nov 1, 2012

### jnorman

zapper - OP question was legit. the standard model is a field model, not a particle model, and pretty much supports the concept that all "particles" are simply manifestations of the associated field. this is born out by the fact that no fundamental particles dispaly any spatial extension, ie, electrons and quarks are point particles, and their properties are manifestations of the field(s).

wiki article on QFT states:
"In QFT, photons are not thought of as "little billiard balls" but are rather viewed as field quanta – necessarily chunked ripples in a field, or "excitations", that "look like" particles. Fermions, like the electron, can also be described as ripples/excitations in a field, where each kind of fermion has its own field. In summary, the classical visualisation of "everything is particles and fields", in quantum field theory, resolves into "everything is particles", which then resolves into "everything is fields". In the end, particles are regarded as excited states of a field (field quanta). "

14. Nov 1, 2012

### ZapperZ

Staff Emeritus
Oh dear. And this somehow is compatible with electrons being an excitation SPECIFICALLY out of magnetic fields? What about them being vacuum excitations out of a fermionic ground state as well? See? I could spew such things endlessly as well!

Please reread my post. I did not ask about the legitimacy of the question, but rather the source. There is more to this than what we have been told. Furthermore, no one seems concerned on what the OP can comprehend. Don't you care even in the least bit if what you just wrote is understandable to the person who asked the question? This is not a place simply to show off our amazing breath of knowledge. This really isn't about you!

https://www.physicsforums.com/blog.php?b=2679 [Broken]

Zz.

Last edited by a moderator: May 6, 2017