In ECM the universe is not expanding — it is accumulating vacuum mass in its Phase-Kernel.
Cosmic redshift measures how much vacuum mass has accumulated between source and observer.
Dark energy is simply the density of Phase-Kernel mass in the vacuum.
Galaxies accelerate because they are sliding down gradients in the vacuum mass field.
The cosmic microwave background is maximally redshifted primordial light after extreme Phase-Kernel mass accumulation.
The universe has a termination radius where Phase-Kernel accumulation saturates, causing gravity and redshift to cease.