Article / Updated 03-26-2016
In 1905, Albert Einstein published the theory of special relativity, which explains how to interpret motion between different inertial frames of reference — that is, places that are moving at constant speeds relative to each other.
Einstein explained that when two objects are moving at a constant speed as the relative motion between the two objects, instead of appealing to the ether as an absolute frame of reference that defined what was going on.