Please exuse this rather long post. I believed that I could explain and describe the OP's question in a very understandable way as well as comment on and clarify other posts. I'm in a good mood today and wanted to do something both useful and fun for myself.
Darrenmackenz said:
I understand that light is part of the electromagnetic spectrum
That is correct.
Darrenmackenz said:
I also understand that light acts as both a particle and a wave.
We say that photons display a wave-particle duality, which means that in some circumstances photons behave like a particle while in other circumstances they behave like a wave, but they do never behave like a particle and a wave at the same time.
Darrenmackenz said:
I think I understand the basics that, light as it travels through a vacuum oscillates between a magnetic field and a electric field at 90 degrees to each other.
For the most part, that’s true. There are some instances where there is a time varying EM field in which the E field is not perpendicular to the B field though. There are also instances where the direction of propagation is not at right angles to the EM field too. But if you have a simple electromagnetic wave then what you say is true.
Darrenmackenz said:
How does this all, get a photon from point A to point B in a vacuum if there is no "ether" with which a photon can travel within?
Think of what you just said in a very literal sense. You can throw a baseball through the air or in a vacuum without a medium through which it moves, right? Think of the EM field the same way.
What is going on is that the presence of an electromagnet field does not require a medium to propagate through since the electric and magnetic fields are what are propagating through the vacuum. Things like sound or water waves are actually the displacement of matter which is doing the propagating. In fact scientists only knew of those kinds of waves before EM theory was fully understood and thus assumed that if light was propagating then it too had to have a medium through which it was doing the propagating. It’s much easier to think of the EM fields as photons moving through space just as, say, a baseball would and in turn think of the fact that you can throw a baseball through space without the need of a medium.
LostConjugate said:
A photon is only a change in the position of an electrostatic source. It is the electrostatic force that travels through the vacuum.
I don’t understand what you mean by this. Can you clarify it for me please? I don’t see a context in which it would make any sense. Are you speaking in terms of quantum field wherein an EM field is composed of photons? If so then it can only be said that if the, previously static, source of an electric field changes position that there is a time varying EM field present which is composed of photons. I.e. it creates photons. It cannot, however, be said to be the definition of a photon. Also it is not the force that travels through space but the field. The electromagnetic force requires the presence of a charge.
Darrenmackenz said:
Maybe you could explain to me how the oscillation propergates according to maxwell.
According to Maxwell’s laws, where there is a time-varying electric field there will also be a time-varying magnetic field. These fields coexist in what can otherwise be a vacuum. They occur in a manner in which the disturbance does not remain at the location of the source of the varying fields. I.e. the disturbances move through space.
Recall how science works – We make observations about nature and then attempt to summarize what we observe in a quantitative fashion so that we can precisely
describe[/I[ what we are observing. We call the resulting descriptions The laws of physics. However the description is not in itself an explanation. What we logically and/or mathematically deduce from. the description is what an explanation in science is all about. In the present case we’re concerned with the laws of electromagnetism, aka Maxwell’s equations. For a vacuum they are named as follows (let “@” represent the partial derivative sign)
Coulomb’s Law: div D = 0
Ampere’s Law: curl H = 0
Faraday’s Law: curl E + @B@t = 0
No monopoles: div B = 0
These equations can be manipulated to form another equation in which one contains only E and the other only B as well as the value 1/sqrt[ u_0 e_0 ] where u_0 = permeability of free space and e_0 = permittivity of free space. This is given the symbol c, i.e. c = 1/sqrt[ u_0 e_0 ] which is the speed of light in a vacuum.
If you want to see and follow the derivation then you must have an understanding of vector differential equations. If you have such skills then please see http://www.scientainment.com/tmm/images/waveq.pdf
mikeph said:
If you combine Maxwell's equations for the case of no charge, the result is a wave equation, and one solution of that equation is an electromagnetic wave.
I find this comment confusing. You say that “one” solution is an EM wave. Do you know of another solution, i.e. a non-EM wave?
harrylin said:
There is no positive evidence that "there is no ether", …
That’s because it’s impossible to prove a negative. But its logically sound to state that there is no either. The ether was defined as that which propagates the EM field. Since then it has been shown that the propagation of an EM field is not accomplished using an ether. Therefore it directly and logically follows that there is no justification for the suggestion that an ether exists. There is also no use for such a concept.
harrylin said:
As a matter of fact, many famous physicists (incl. Einstein) concluded that vacuum cannot be nothingness, which implies some kind of ether.
That is incorrect. Particle physicists define the vacuum as the lowest possible energy density. In such a vacuum particle-antiparticle pairs materialize and then annihilate each other at random. However this is in no sense an ether.
HallsofIvy said:
A light wave is a ripple in the electromagnetic field. It does not "oscillate between a magnetic field and an electric field".
I believe that he was thinking of is the fact that an EM wave can consist of an electric field oscillating along one direction and the magnetic field oscillating along another, perpendicular, direction.
Darrenmackenz said:
So your saying light induces it's own electric and magnetic fields by oscillating them, this then becomes self propergating.
That is not a good way to envision it. Don’t think of light as inducing EM fields which then propagate. Think of it as light is a propagating time-varying electromagnetic field.
mikeph said:
Darrenmackenz said:
Is there already an electromagnetic field present before light is even introduced?
Yes.
This response will be misleading if not properly understood. Any radio transmitted which is electrically neutral can emit an EM wave. It’s quite possible for an electrically neutral atom that is in an excited state to transition to a state of lower energy by emitting of a photon. You can also have a charged particle located inside a charged sphere where the total charge is zero. Set the charge inside oscillating and it will emit an EM wave. Look at your uncharged hand. If you see it then it’s emitting light and there is no electric field present. There are any number of examples of this. What mike is thinking of is the fact that at subatomic level there are fields which don’t cancel – I just wanted to be crystal clear on this point.
