Am I an atheist?

[theVOID]

... and there is evidence to suggest that the speed of light is universally slowing down. I understand what refraction is, and what a spectrum is about.

Light often speeds up and slows down, depending on the composition of the area it is travelling through. It is only in a vacuum that light has a constant speed, this is still a good medium of measurement for space though, because although empty regions of space are not entirely vacuums, the percentage of deviation from the vacuum speed of light is negligible.

There is a creationist claim that the vacuum speed of light is slowing down, but it's far more likely that our skill at measuring has increased.