This book is legendary. Time is illusory, as the real measure of that nominal concept is actually an invarient travel of distance (by light) relative to a variety of varient motion by matter subject to length contraction (including contraction due to gravity).

The invarience of light's speed allows all things to be compared to it, in order to find out when length contraction is happening or isn't in some scenario or other. This is how we know electrons contract in particle accelerators.