Michelson and Morely proved that the ether does not exist. What this shows is that space is empty - it contains nothing. If space contains nothing and photon exist in space then the photon must be something - here are no other values in the set.
I have only found one serious attempt to compare the speed of light at different frequencies. (Lovell B, et al (1964) Relative Velocity of Light and Radio Waves In Space Nature 202, 377 (25th April 1964)
The results were consistent with light traveling slower than radio waves, but the...
What do you mean by virtual electrons and virtual positrons. How do these differ from real ones? Do they have substance? Do they have mass? Do they have momentum?
That tells me what photons are not.
My question is what are photons?
It comes back to the question: what is vibrating, is it the photon that has substance or is it the environment?
The former poses the problem of how then the photon has zero mass, and the latter faces the problem...
The problem is that the freshmen physics textbooks do not really address the question.
Either the photon must have substantial form, in which case how to explain that it has no mass, or the environment in which it is moving is the cause of its existence, but this is to re-invent the ether by...
Perhaps you could elaborate on the word packet. Is this a substantive packet, ie does it have material form. If so how can it not have mass. If not then what exactly is the means by which energy is transmitted? What is it that is oscillating?