Being at rest

As a subject, an observer is fundamentally at rest in a reference frame, and this being at rest allows for measuring the motion of physical objects. Exploring the experience of centrifugal force brings to the fore the natural inclination to see oneself at rest in a reference frame. The discrepancy between the experience of centrifugal force and its lack of fundamental significance in Newton's laws of motion points toward the importance of the observer as a subject in his or her own reference frame, specifically the observer's experience of being at rest in this reference frame. In addition, the observer's being at rest for himself or herself in a reference frame is a central feature of both special and general relativity.