It is noteworthy that the Bible is not the only ancient record of the long day. Immanuel Velikovsky, in his book Worlds in Collision, 6-6 gives abundant documentation of this fact, as have many other writers. It is difficult to account for the widespread incidence of such an unlikely narrative unless it is based on an actual fact of early human history. Whatever the cause, the event itself seems really to have occurred. 6-7 One common criticism of the Biblical record of the long day is that its language is unscientific.
All motion is relative motion, and the sun is moving as well as the earth.
No one knows where in the universe there may be a fixed point of zero motion. That being so, all velocities must necessarily be measured with respect to some arbitrarily assumed fixed reference point. The proper point to choose is normally the one which is most convenient to the observer. Joshua's language, therefore, is perfectly modern and correct. This seems no more difficult to believe than that only the earth stopped rotating.