c as a constant
The speed of light is a constant from a given frame of reference. Thus in order for someone traveling near c to see the speed of light as a constant, time must slow down for them relative to an observer in a different frame of reference.
You're always traveling at the speed of light through 4D spacetime, so the faster your travel through 3D spacetime the slower your travel forward in the time dimension. Perhaps inflation is related to the speed of light in a similar manner.
Though if inflation causes the speed of light to be faster as theorized here, that 5th "inflation dimension" must be an imaginary number to work within the x^2 + y^2 + z^2 + t^2 = c^2 framework.