Continuing from another section ... where this doesn't belong ...

What do you mean by nothing, by travel, by fast, by light?

I will start with "what is a photon" ... or "what is light"?

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Login ... neither wave nor particle, classically modeled incorrectly by EM theory. At lower energy the wave like aspect dominates ... at higher energy the particle aspect dominates. This is because our view of things is ... pragmatic, not "truth". Also a photon is more particle like in small scale situations, and more wave like in large scale situations. My grandfather'r radio transmitter was at 800 Kilocycles AM. The wavelength at that low frequency (low energy) is about 374 meters, his transmitting antenna had to be half that length (half dipole) or 187 meters or 560 feet tall. That is one big, diffuse particle!

The quantum vacuum isn't empty, so what do yo mean by nothing? Something imaginary?

By travel, there is both group velocity and phase velocity ... it is group velocity that is limited, that is the speed at which modulation can travel ... which isn't greater than C ... in whatever units you care to define that. Speed isn't the same as velocity. Fast is relative .. for sub C velocity, this is significant. But with light in a vacuum (in matter it is less fast hence index of refraction) comparisons don't mean what we think they mean, hence Special Theory of Relativity. Speed not being the same as velocity (because space-time connection) is further clarified in the General Theory of Relativity.

Travel is ... cause/effect propagation (aka group velocity) or is it timeless consequence (quantum entanglement)? Basically temporal and non-temporal logic in math terms. They are different, that is why quantum entanglement can't be used for faster-than-light signaling. All tests to prove any variability of C (speed) in vacuo has failed (this is the consequence of it being a dimensionless quantity ... in space-time). The velocity does change .. gravitational lensing etc. In fact we can choose our units of distance and time, such that C= 1.0.

Edit .. a half dipole antenna is 1/4 wave length, so an antenna 280 feet tall ;-)