Speed of light

The speed of light in vacuum is constant as far as I know, but it is less in various materials, such as glass.

I have been reading, with some skepticism, about the variance in the speed of light. Who has information that can shed some light on this? Is there something to this or is it just another example of junk science?

Here we go...
http://www.space.com/scienceastronomy/generalscience/constant_changing_010815.html

The research was met with caution by many scientists, who also said that if it is accurate, then the adjustment to theories would be significant and far-reaching.

... This implies that something in the early universe behaved differently. Because the speed of light is one factor in the fine structure constant equation, it might be it that has changed over time, Churchill said. Or it could be that unknown properties of the early universe forced atoms and electrons to behave in ways researchers don't understand.

..."There are many possibilities to incorporate a variation of the fine structure constant into existing theories, and there are some theories were the constants of nature are predicted to vary," Stiavelli said. "For the proponents of these theories this would become evidence that the theory is correct."

One of the ideas that might benefit is string theory, which holds that there are many more dimensions to the universe than just time and space. String theorists say that changes in these dimensions over time could force changes in the fine structure constant.

Several scientists told The New York Times that they were skeptical that the new finding would hold up under further scrutiny, saying that the very small difference found could be a slight statistical or observational flaw in the study. But these same scientists were also excited about the possible implications.