No one doubts but that we imagine time from the very fact that we imagine other bodies to be moved slower or faster or equally fast. We are accustomed to determine duration by the aid of some measure of motion.
The Soviet Union came apart along ethnic lines. The most important factor in this breakup was the disinclination of Slavic Ukraine to continue under a regime dominated by Slavic Russia. Yugoslavia came apart also, beginning with a brutal clash between Serbia and Croatia, here again 'nations' with only the smallest differences in genealogy; with, indeed, practically a common language. Ethnic conflict does not require great differences; small will do.