  Contrary to our immediate and vivid sensation of past, present, and future as
continually shifting non-relational modalities, time remains as tenseless and
relational as space in all of the established theories of fundamental physics.
Here an empirically adequate generalized theory of the inertial structure is
discussed in which proper time is causally compelled to be tensed within both
spacetime and dynamics. This is accomplished by introducing the inverse of the
Planck time at the conjunction of special relativity and Hamiltonian mechanics,
which necessitates energies and momenta to be invariantly bounded from above,
and lengths and durations similarly bounded from below, by their respective
Planck scale values. The resulting theory abhors any form of preferred
structure, and yet captures the transience of now along timelike worldlines by
causally necessitating a genuinely becoming universe. This is quite unlike the
scenario in Minkowski spacetime, which is prone to a block universe
interpretation. The minute deviations from the special relativistic effects
such as dispersion relations and Doppler shifts predicted by the generalized
theory remain quadratically suppressed by the Planck energy, but may
nevertheless be testable in the near future, for example via observations of
oscillating flavor ratios of ultrahigh energy cosmic neutrinos, or of altering
pulse rates of extreme energy binary pulsars.
