  We demonstrate an unsuspected freedom in physics, by showing an essential
unpredictability in the relation between the behavior of clocks on the
workbench and explanations of that behavior written in symbols on the
blackboard. In theory, time and space are defined by clocks synchronized as
specified by relations among clock readings at the transmission and reception
of light signals; however spacetime curvature implies obstacles to this
synchronization. Recognizing the need to handle bits and other symbols in both
theory and experiment, we offer a novel theory of symbol handling, centered on
a kind of "logical synchronization," distinct from the synchronization defined
by Einstein in special relativity.
  We present three things: (1) We show a need in physics, stemming from general
relativity, for physicists to make choices about what clocks to synchronize
with what other clocks. (2) To exploit the capacity to make choices of
synchronization, we provide a theory in which to express timing relations
between transmitted symbols and the clock readings of the agent that receives
them, without relying on any global concept of "time". Dispensing with a global
time variable is a marked departure from current practice. (3) The recognition
of unpredictability calls for more attention to behavior on the workbench of
experiment relative to what can be predicted on the blackboard. As a prime
example, we report on the "horse race" situation of an agent measuring the
order of arrival of two symbols, to show how order determinations depart from
any possible assignment of values of a time variable.
