[abdullahkhalids]

Your second point is where all the trouble is arising. Special relativity is talking about one thing and one thing only - how an object moves from one point to another in space, and how fast this process appears. The position (and speed and acceleration) are external properties of an object, they depend on who is doing the describing of these properties. Special relativity is concerned mainly with these things.

Objects also have other internal (non-space/position) related properties. For example, light has polarization. These properties can and do change with the passage of time. For example, you can change the polarization of light with a strong magnet. Relativity can and does place some restrictions on how this evolution happens, in so far as something is moving in space, but that is a more involved story.

[carlob]

And the third point is where that trouble can be resolved: light doesn't move through matter at c.

[mygo]

> Objects also have other internal (non-space/position) related properties. For example, light has polarization.

So the angular momentum of light would be put under the same category as polarization, which is a property that a single photon can have?

Or is it a property like wavelength, momentum, frequency, intensity, etc -- a property of light that can be observed only when the light is a system of lots of photons, instead of just an individual photon?

Also, sorry if my categories are wrong. If so, I hope it doesn't take away from my main question of whether it is a property of a single photon or a property of a system of photons

[abdullahkhalids]

Every category you have named, wavelength/frequency, intensity (function of frequency), linear momentum (function of frequency), polarization are properties that individual photons have. It is possible to construct photon detectors that are able to resolve these properties for a single photon thrown at them.

Orbital angular momentum is also a property of single photons, related to the shape of their wave function. You can read about it and see some example shapes on the wikipedia page https://en.wikipedia.org/wiki/Orbital_angular_momentum_of_li...

I can't think of a property of light that is only in the bulk and not at the single photon level (somebody correct me if I am wrong). But I haven't read this paper in any detail to find if the "torque" is a bulk property or a single photon property.

[nine_k]

Wavelength = 1 / frequently and is directly related to photon's energy. You only need one photon to observe these.

Intensity is number of photons per unit area per unit time, so it takes many photons normally, but a single photon produces a non-zero intensity.