Which begs the question. Is the universe really as old as we have been told?
If my memory is accurate, it is older than I am. More I cannot say. ;-)
Well, these guys aren’t theorizing that the universal light speed can change or decay, they’re just talking about the local light speed. Essentially, they’re saying the vacuum isn’t just a vacuum, because it’s full of virtual particles, so there is a local light speed in every region of space.
Though, if they are correct, and if something caused the density of the vacuum particles to vary over time, then that could have implications essentially the same as if the universal speed of light varied.
Couple this with gravitational time dilation [per one Albert Einstein] and then the long ages for the Earth and Universe become much more ‘apparent’...
101 Evidences for a Young Age of the Earth...And the Universe
http://creation.com/age-of-the-earth
See also:
Starlight and Time by Russell Humpheys
The key to the starlight and age of the universe is ‘gravitational time dilation’.