If galaxies were moving within static space like shrapnel from an explosion centered on us, what key observational fact would be missing?

Answer

The neat proportionality between redshift and distance.

If movement were only due to initial momentum in static space, the shifts would be dictated by random gravity and momentum; the observed systematic proportionality with distance proves the expansion of space itself.

If galaxies were moving within static space like shrapnel from an explosion centered on us, what key observational fact would be missing?
lightgalaxycosmologyexpansionredshift