# What is free electromagnetic field?

1. Nov 3, 2014

### sergiokapone

Maxwell's equations solutions in vacuum - is a free electromagnetics waves.
Such solutions can be obtained even without knowing anything about the charges and currents. Does this mean that such waves is the essence , not related charges, e.g. free electromagnetic waves?

Moreover, the Maxwell's equations with $\delta$-shaped sources also give the solutions, that looks like free electromagnetic waves, but in a far (wave) zone. Sometimes it is said that it is a field that is off the charge , but its amplitude is uniquely determined by the motion of the sources .

Is it possible to think that there are waves that are generated by charges , and others which exist independently?

2. Nov 3, 2014

### Jano L.

Yes, total field can be though of as sum of retarded fields of close-by particles and the background field. The background field can be thought of as having no sources, or as having very distant sources.

3. Nov 3, 2014

### sergiokapone

Did I understand correctly, if we imagine the world with no charges, for example, the EM-waves will still exist?

4. Nov 3, 2014

### dextercioby

The classical e-m field is created by classical sources. The <free Maxwell fields> are a useful approximation, especially when going into quantum mechanics.

5. Nov 3, 2014

### sergiokapone

Ok, thanks for all.

6. Nov 3, 2014

### mikeph

There are two questions here. Do free-space solutions to Maxwell's equations exist? (Yes) Will they exist in a spacetime that has never contained any charges or currents? (No)

7. Nov 3, 2014

### sergiokapone

But it does not follow from the Maxwell's equations.
Therefore , the answer is "no" - a hypothetical.

8. Nov 3, 2014

### sergiokapone

The answer rather "may be not, but it is possible"

9. Nov 4, 2014

### Jano L.

Mathematically, it is possible to have non-vanishing EM field without electric charge anywhere.

10. Nov 4, 2014

### HomogenousCow

Only if you have non-zero boundary conditions. Which then makes the problem, incomplete in a sense.

11. Nov 4, 2014

### zoki85

Neutron-antineutron annihilation creates gamma rays. Can we conclude from this, the neutron is composed of charged subatomic particles ("quarks")

12. Dec 27, 2014

### zoki85

*Bump*
:)

13. Dec 27, 2014

### Vagn

No, electron-positron annihilation also produces gamma-rays but there's no evidence that electrons and positrons have any substructure.

14. Dec 27, 2014

### zoki85

You didn't understand the question