# Origins of the electromagnetic force

1. Jun 17, 2014

### Crapsghetti

I saw a very old post where someone asked where an electron gets it's charge. Where does the charge come from? Doesn't it arise from the interaction with photons? My understanding is that electric charge and magnetism can not exist without photons, and the electron itself most likely could not exist independent either, a kind of relativistic quality. Can a single photon ever exist in a void without electrons? I don't think so.

I suppose that the electromagnetic force is created by an exchange of photons between charges, but is the charge itself also created by this photon interaction?

2. Jun 17, 2014

### DennisN

Hi Crapsghetti, and welcome to PF! Electric charge is an intrinsic property of particles, i.e. it is there from the beginning, i.e. it is not created by any interaction. "Where do these charges come from?", or, better put, what is the origin of these charges? We have no information about that (today) - it is simply a feature of the particles as we know them.

Last edited: Jun 17, 2014
3. Jun 17, 2014

### bhobba

4. Jun 17, 2014

### Crapsghetti

Seems like an interaction to me. Can you really have a charge that doesn't emit photons? Can you have a photon that did not come from a charge? They seem linked to me. With out one the other can not exist.

Last edited: Jun 17, 2014
5. Jun 17, 2014

### DennisN

Question 1 to consider: How do you get from

to
Question 2 to consider: Where do the fractional electric charges ($\pm 1/3$, $\pm 2/3$) of the quarks/antiquarks come from?

6. Jun 17, 2014

### Bill_K

The same place that the electron came from.

7. Jun 17, 2014

### DrChinese

Yes. Some non-linear crystals will split 1 photon into 2 photons.

8. Jun 17, 2014

### kurros

Well the electric charge of a particle is *defined* to be the strength with which it couples to photons. So if there were no photons to couple to, then electric charge would be meaningless.

9. Jun 17, 2014

### bhobba

You can - there is no mathematical reason you cant have a property of charge with no field and conversely. But when you go into the math, notably the gauge symmetry view, one practically screams out for the other. To be specific given the electric field E you define ∇.E = p and show that p, plus a few reasonableness assumptions, has all the properties of that interesting thing called charge - specifically charge density.

The following by Kobe gives the detail if you can get a hold of it:
http://inspirehep.net/record/157843/citations

Thanks
Bill

Last edited: Jun 17, 2014
10. Jun 18, 2014

### Crapsghetti

Hmm... but the original photon must have come from a charge and the 2 photons might as well be one, right? My understanding of quantum physics is pretty naive lol. I guess a photon could create a photon. So, you got me.

11. Jun 18, 2014

### Crapsghetti

Okay, so you are saying that there is an interaction, but the they do not create each other.

And for your question 2, it's the exchange of gluons, duh! Can a gluon exist without a quark? Can a quark exist without gluons?

12. Jun 18, 2014

### Crapsghetti

That is very interesting. I will try to read that later. I'm in a biochemistry internship. I don't know why I like physics. I think it's just because I like to think about stuff.

Anyway, sorry for the three posts in a row. I don't see how that kind of thing is bad forum etiquette. To me, it neatly spaces out each reply I gave to each poster. It is at least an organized way of triple posting.

Hosanna!