The folks who wrote those articles on the change in the speed of light were mostly all physicists and cosmologists who have worked in their perspective fields for a long time. The emperical data shows a measureable change in "C" in the last few hundred years. So how would that be accouted for exactly? I could understand it for a 200 years ago but we have known how to calculate it very precisely for well over a hundred years now yet we still see the slow down.
I have heard of such a theory, it isn't commonly accepted though.
And most experimental data does point to the speed of light being a constant C. There is a bit of data which could point otherwise, in some theories, which these theorists prefer. (this is from my memory of a discussion of it, I haven't read the theory)
If there was an experimentally (Directly) change in the speed of light, it would be a much bigger deal as it would point to many of our theories being wrong.
As far as the interaction of "C" and material science I agree it would be much different than what we know now. However, whose to say that the way things are now is the way things have always been? We seem so confident in what we know and observe. Such arrogance we have at times. We may not even realize just how much of what we see may in fact be illusionary in nature at it's base.
It would be insanely different then what we know now. To have the effects on light that you postulated would require completely different physics (all the laws and understandings that we have would have to be wrong, all our observations/etc would have to be wrong, everything would have to be so different that we couldn't even comprehend or talk about how different it was) or a completely different world (so different that we also couldn't comprehend how different it was). Through the history we don't see the second, and all our evidence points to the first being wrong as well.
Once more, affecting the speed of light (by a lot) isn't a small change. It is a massive change that would cause our biology not to work and the wheel not to work... pretty much unless all our history is faked this is not correct.
I would bet that these theorists are claiming that the speed of light isn't a constant, but rather changes (slightly) due to other things... that the speed of light isn't a fundamental quantity. This might be true (most physicists don't agree with them), but the effects on biology, chemsitry, and most of the rest of physics would be very extreme for changes that are other then very slight.
Remember the Bible says that with God all things are possible .
Yeah, I agree, with God all things are possible. But why would He do it that way when He could just create light traveling to the earth? (if the universe is really 7000 years old, which the Bible doesn't claim) Why would He change how everything in the universe works? I mean, you have a lot of assumptions there. And how the universe works (the physics of it) seems to perfect now... why would he change it back then?
JM