Atomic clocks exchanging signals serve as a background against which to measure the motion of objects on or near the
Earth. The background of clocks and signals requires feedback involving computation, both internal to each clock and for
regulating relations between clocks. Feedback within a clock responds to a flow of measured outcomes which, by quantum
theory, are unpredictable. The steering of atomic clocks in response to unpredictable occurrences of outcomes depends
on a wave function, and the choice of this wave function requires an assumption underivable in any logic consistent with
quantum theory—another form of unpredictability.
Currently backgrounds for motion, for example used in the Global Positioning System, consist of one or another
(physical) reference frame as a realization of a (mathematical) reference system that consists of a spacetime coordinate
chart with a specified metric tensor field—a structure that expresses neither the unpredictability inherent in atomic clocks
nor the feedback by which one deals with this unpredictability. Without requiring the assumption of a metric tensor or
even a spacetime, here we introduce a novel type of reference system consisting of the records and criteria resident in
real-time computers that mediate feedback, a reference system that, by expressing feedback, structures the unpredictables
in a background of motion. The criteria for clock adjustment are discussed. Trade-offs involved in these criteria call for
adjusting a background in response to the motion of the objects tracked.