I realize that the analogy may be getting a bit strained, but let's go back to the dots on the balloon analogy for the expansion of space. As the balloon inflates the dots move apart from each other. But there is no more balloon between the dots than there was before the balloon was inflated. Space works the same way. There is no reason to postulate the creation of more matter to fill the intervals. In fact that idea was the center of the steady state hypothesis that was overthrown by the discovery of the cosmic background radiation.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.