NOW: The Physics of Time - Richard A. Muller

Muller makes an argument for time being fundamental, not emergent. At the moment of the Big Bang, a “leading edge of time” was set in motion, and everything lives on that uneven edge. If space is always expanding — that is, new space is always being created (the Hubble Expansion) — why isn’t time also created?

Every moment, the universe gets a little bigger, and there is a little more time, and it is this leading edge of time that we refer to as now.

The flow of time is not set by the entropy of the universe, but by the Big Bang itself. The future does not yet exist (despite its inclusion in standard space-time diagrams); it is being created. Now is at the boundary, the shock front, the new time that is coming from nothing, the leading edge of time. (293)