There is something that bugs me about inertial frames. According to Einstein's definition (chapter 4 of "Relativity"), an inertial frame is one for which Newton's first law holds: "a body far enough removed from other bodies continues in a state of rest or uniform motion in a straight line." He then states that it is with respect to these frames that the Newtonian laws of mechanics are assumed to hold true. And of course, his postulate of special of relativity concerns these reference frames also, saying that wrt any two such frames of reference, the laws of nature take the same form. Also in chapter 4, he gives as an example of a non inertial frame of refenrence a frame that is attached to the earth, because wrt such a frame, the stars, which are far removed from other bodies, don't move in straight lines (they move in circles due to the earth rotating). Ok, so any frame of reference that we use on earth to measure stuff is non inertial. So then neither the Newtonian laws of mechanics nor the postulate of SR applies to them. What the heck???