Every physicist worth his or her salt will take a definite stand on the wave/particle question of light. It is a common misunderstanding of the general public that this question simply means that light has a “dual nature”. Far from it. Either you think that light is a particle or it is a wave. There is no in between.
The ultimate question is whether it makes more sense for a particle to have wave-like characteristics or for a wave to have particle-like characteristics.
Consider a double-slit experiment.
When a “beam” of light is shot through, there is an interference pattern seen on the other side. This indicates that light is most definitely a wave. But now we have to ask in what way waves can exhibit particulate behaviour. Very easily, in fact. When two waves interfere with each other, there are certain regions of high energy intensity interspersed by regions of no intensity. In other words, sometimes the two waves are additive and sometimes they cancel each other out. This behaviour is identical with particles inside of empty space.
So, how is it possible for a particle to have wave-like characteristics? This is very difficult if not impossible to imagine. In fact, I don’t have any need to imagine it because I am very comfortable with the way in which true waves can behave in particulate ways.
About the luminiferous ether. Because light was found to propagate transversely, and because transverse waves were known to propagate only in solid bodies, many 19th century scientists felt necessary to picture the light propagation medium as a static, solid block. But it is obvious that the ether cannot be a typical substance, as we know them to be. It is its own thing, with its own characteristics. There is no reason that the ether cannot be an extraordinarily dense, yet highly fluid medium.
Because of its density, it will be able to transmit transverse waves, and because of its fluidity, we can imagine that it moves in concert with gravitational fields. This means that the luminiferous ether that surrounds the earth may very well be stationary with respect to the earth’s surface. In fact, there may be an even deeper connection between the ether and gravity. It may very well be that gravitational fields are entirely functions of the activity of the light propagation medium.
Well, experiments have shown that no motion through the ether can be detected. Because of this, we must assume simply that the earth’s gravitational field and its ether context are coincidental. In does not make sense to assume the non-existence of a light propagation medium. The reason for this is simple: there cannot be an energy wave without a medium for it to travel through. In fact, the best definition for an energy wave is something to the effect of, “a radiating disturbance of a practically continuous substratum.”
James Clerk Maxwell, however, attempted to describe light as some kind of ever propagating electric-magnetic fluctuation. However, there are no examples in nature of electric or magnetic fields doing this kind of perpetual dance through space. We know that a single electric current describes a single, spatially-bound magnetic field. If you crank up the juice on the current, the magnetic field gets bigger. If you move the wire through which the current flows, the magnetic field adjusts immediately to its new location. Magnetic fields, in other words, do not have minds of their own.
Because there was, in the 19th century, such a clamour to describe the nature of light, Maxwell decided to forcefully marry the relatively inexplicable phenomenon of light energy propagation with the much more researched one of electromagnetism. Well, Maxwell got away with it because no one had any better ideas. To this very day, physicists are stuck with describing light energy as being “electromagnetic radiation”.
There is no reason to complicate matters. If we just say that light energy consists of ever expanding, transversely oscillating spherical wavefronts within an extraordinarily dense yet highly fluid propagation medium, then we can just leave it at that.
There is not necessarily anything fundamentally “quantum” about light.
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