... but to describe things in terms of other things. No one is asked to understand why the speed of light is what it is, it is a postulate which, together with other postulates and a fair bit of reasoning can be demonstrated to stick quite well to the world as we observe it.
There is no faith in that, if an observation does not fit, it just shows that either the reasoning was wrong or that the postulates were wrong. Back to the blackboard then...
That in fact is what makes science quite different to religions according to some: for something to be considered part of science, it must be possible to find experiments to potentially prove it wrong. If no such experience can be found, then it belongs to faith and is not generally very useful it terms of its predictions. It may of course still be very useful for one's peace of mind however.