The physics of the conventional description of the universe are founded on the equations of special and general relativity. In special relativity theory an observer perceives that moving clocks run slow, and that moving objects shrink in the direction of their motion. In general relativity theory clocks slow and space expands within gravitational fields, and in the empty regions of the universe space expands continuously while time remains stable. The equations that describe these phenomena work well, but they provide no insight into an underlying physical process or processes. This paper postulates an alternative version of the universe, and a single physical process that underlies relativistic phenomena. This version of the universe has unchanging spatial distances, but a variable “speed limit” that determines the local speed of light and the local temporal rate. The combined gravitational fields of all the masses in the universe that affect a spatial location determine the local speed limit there. Prior to the start of the modern universe there was only energy, in the form of massless particles. There was no mass and no gravitational fields, and the speed limit everywhere was effectively infinite. At the start time for the modern universe mass particles formed from the energy, and their gravitational fields have been growing, at the (gradually-slowing) speed of light ever since that event, some 14 billion years ago. As a result, the gravitational intensity everywhere has steadily increased and the speed limit has steadily decreased. The alternative universe’s occupants observe cosmic redshifts due to the gradually reducing speed of light, rather than due to spatial expansion. The redshifts that we predict for that universe closely match the results of astronomical observations, despite the fact that the alternative universe is spatially stable and contains no dark energy. Where there are gradients in the gravitational intensity, the corresponding gradients in the speed limit underlie the gravitational accelerations of both masses and massless particles. Clocks, which work by counting cyclic motions involving masses, respect their local speed limit. Unlike the conventional universe, in the alternative universe the speed limit never drops to zero. The alternative universe’s black holes have no event horizons, and rather than being black they are just (very) red-shifted.