SCPID theory claims that all natural systems will cycle to function and they act by moving around an area bounded by circular paths. These cycles or circular paths will finish at the point at which the course began . Life on Earth displays an endogenous, entrainable oscillation which is about 24 hours and cues such as daylight and dark are stimuli. Systems have clear patterns of built in self sustained and adjustable rhythms and in living things they can persist in the absence of external cues and they are entrainable to match the local time or reset by exposure to extrnal stimuli.