Time concepts in physics, biology, and pharmacokinetics.

Three major types of time relativity are discussed: physical, biological, and psychological. Physical relativity illustrates how the same distant event may occur in the past of one observer and in the future of another. Moreover, space and time variables are not viewed in isolation from one another, but rather are blended together into a static, four-dimensional "block universe." Biological relativities arise through coordinate transformations of physical time-scales such that relevant processes become invariant in space-time. Because pharmacokinetic processes are integrated through a common, highly coordinated series of systems, relations between mammalian species may be probed through empiric allometric coordinate transformations. Psychological time relativity deals with a creature's awareness of its own duration and location within a restricted range of reality; it involves the transformation of perceived sequences (stimuli) into durations.