The "speed of light" changes depending on the medium, just like sound has a different rate depending on the medium. With light, this is the refractive index. The speed of light in a medium is inversely proportional to the refractive index of the medium, and it varies depending on the medium.
Discussion
The speed of a photon never changes. Light itself never slows down or speeds up. The average speed measured over a set distance in a medium will of course vary, but the speed of the photon will always be constant.
Sound is not the same as light. Sound needs a medium to vibrate through, thereby changing its speed. Light does not.
Virtual particles and photons nothing more than concepts, they don't exist.
You're looking at it through the (incorrect) lens of atomism, when we have an aether which was proven a long time ago.
"Light can be nothing other than a sound wave in the aether." - Nikola Tesla
Tesla and the fathers of field theory all understood this, and without their understanding we wouldn't have an electrical grid. Light doesn't travel, it is the rate of induction of the aether.
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I’m highly skeptical of this. Just because Tesla was hugely influential in the field of electro physics, does not mean he was correct about everything. The Aether has never been detected in any way shape or form; it’s not observable or measurable or detectable, like it doesn’t exist. Certainly it’s not set in stone that an Aether does not exist, but no one has been able to prove its existence.
There’s no need for any luminiferous medium for light to travel through to explain how light works.
Understandably so, I was too when I first started diving into the idea a few years ago.
MMX proved the aether exists, and all the inventions like the AC motor were developed using theory that stems from the existence of aether. It wasn't just Tesla; Faraday, Heaviside, Steinmetz, Maxwell, Dollard, and many more all knew it to be true.
"The Aether has never been detected in any way shape or form; it’s not observable or measurable or detectable, like it doesn’t exist."
That's pretty much how dark matter is described, and it is where I believe relativity dies. It cannot progress in any meaningful way without the aether.
The medium is why light exists at all, since it is the a disturbance of the medium itself. Light stops illuminating once it is no longer propagating through the medium. That is what makes frequency and vibration key, because they are the means of manipulating the aether in order to manifest energy.
You will have loosen the grip on some of your existing beliefs in order to entertain this theory from this perspective.
This was one of the first books that got me into the topic:
Still skeptical, but I’ll have a read/check out the book you mentioned 👍🏻