If light is a wave, what is waving?

[Drakkith]

I feel any answer other than "the electric and magnetic fields" is more philosophical than scientific currently.

 

[Studiot]

Talking of metaphysics the difficulty is this:

If we require a medium (field, aether, whatever) for the wave to travel in it implies that the medium was present before the wave started traveling and the wave spreads through the undisturbed medium at the wave velocity.

So if this medium is an electric or magnetic or electromagnetic field for a light source, how did the medium get there before the first emission of the light?

Alternatively we can suggest that the wave somehow takes its medium along with it or creates its own medium as it goes along.

 

[harrylin]

OK, so that is an historically correct "when did you stop beating your wife" question.

Yes indeed - I didn't mention or elaborate on that as I didn't want to step on someone's toes.

 

[harrylin]

[..] So if this medium is an electric or magnetic or electromagnetic field for a light source, how did the medium get there before the first emission of the light?

A similar "difficulty" would be raised by the question "if the light source is an atom that will emit the light, how did the atom get there before the first emission of the light?".

Alternatively we can suggest that the wave somehow takes its medium along with it or creates its own medium as it goes along.

That's a very different model - can you illustrate that with a water or sound wave? Or do you know an article describing that model?

 

[Studiot]

That's a very different model - can you illustrate that with a water or sound wave? Or do you know an article describing that model?

Well for an ordinary common or garden type Hawaiian surfing wave the water is there beforehand for the wave to propagate in(to). The wave can be seen to develop, travel and finally disappear.

On the other hand, when a tidal bore or surge occurs there is little or no water present beforehand. Certainly not enough to accommodate the oscillation amplitude. The bore front takes sufficient water along with it.

 

[PhilDSP]

I feel any answer other than "the electric and magnetic fields" is more philosophical than scientific currently.

Isn't it worth considering fields to be transformational devices that manipulate and transform other qualities such as force, energy, potentials, momentum, polarization potentials, etc., in a consistent and physically meaningful way? In a sense, fields collect what we know about how those other qualities are coupled together. In analogy to house construction, they provide the blueprint, but not the physical realization of the framing, plumbing, electrical system and so forth.

 

[Swetasuria]

First of all the field doesn't travel. It's just there, everywhere, including the vacuum. In reality the field is made up of quantized harmonic oscilators.

Fields can have directions, right? If they are "just there, everywhere", then how come fields are vector qantities?

 

[harrylin]

Fields can have directions, right? If they are "just there, everywhere", then how come fields are vector qantities?

Forces have directions, and as you can see in post #68, it seems that originally (and technically), fields were just the neighbourhoods where those forces were felt. However, later the term field strength (and sometimes simply "field") was used as a measure for the strength of forces that can be felt in the field - which includes directionality.

PS I'm amazed by this accurate intro in Wikipedia (although it is messed up by the there following "qualitative description"):
"In physics, an electric field is the region of space surrounding electrically charged particles and time-varying magnetic fields."
-http://en.wikipedia.org/wiki/Electric_field