FROM YOUR FAVORITE RACE\RELIGION\POLITICAL SUBGROUP,
TO ALL MY JEWRESEARCH HOMIES,
HAPPY JEW YEAR!
It's simple. "Empty" space is not empty. It's full of electromagnetically-neutral particles, which we can call "ley particles" or "leys" (sometimes spelled "layze"). Each ley particle consists of a perfectly-balanced electron and positron orbiting one another. Electromagnetic radiation is a wave traveling through this field of ley particles.
The reason the speed of light changes as waves pass through different substances is that the density of the ley particle field is different within different substances because atoms displace some of the ley particles, which cannot easily penetrate the negative electrical field of the electron shell of an atom (not easily, but they do penetrate it).
These interactions are also responsible for what we perceive as gravity; there is a gradient between "empty" space, which has the highest density of ley particles, and space which contains matter, which has a lower density of ley particles, depending on the radius of the negative electrical fields of the atoms therein (more mass = wider negative electrical field radius). This gradient results in a constant flow of ley particles from areas of greater density toward areas of lesser density, and this flow acts on all matter and electromagnetic waves, as well as other less-understood subatomic "particles."
>She reached the conclusion that the speed of light is changing while working at NASA.
Of course it is. As the galaxy, sun, and planets move through space, they encounter areas of lesser and greater aetheric density. c is greater when there are more ley particles present. The idea that c is ever a constant is one of our most foolish assumptions.