In physics, an inertial frame of reference is a member of the subset of reference frames with the property that every physical law takes the same form in each such frame. In contrast, in the set of non-inertial frames the laws of physics are frame-dependent, and the usual physical forces must be supplemented by fictitious forces. In flat spacetimes all inertial frames are in a state of constant, uniform motion with respect to each other, while all non-inertial frames are accelerating with respec… (More on Inertial)