All motion is relative to some frame of reference. The simplest laboratory frame of reference is three mutually perpendicular axes at rest with respect to an observer. Such a system is commonly used in the laboratory when various types of motion are being studied. The general effects of other motions to which the system as a whole is subjected are then neglected and the system is said to be isolated. In terms of the frame of reference of an observer some distance from Earth, the laboratory frame of reference would be moving with Earth as it rotates on its axis and as it revolves about the Sun. A simple form of motion in the laboratory frame of reference would appear to be a much more complicated motion in the frame of reference of the distant observer.