Hello again! Another silly question from a silly engineer if you guys would help, please? Question is: do we know enough about how time flows (in a frame of reference at rest) to assume that it has always flowed at the same rate, ever since the first plank time after the big bang? I mean, I assume (but I really don't if that is feasible or not) we can study the light from galaxies very far away and gather some conclusions how time flowed there when they emitted their light, but that was from 480 million years after the big bang. How about the initial 479 million years? Thanks all! ps: a side question - do we know if the flow of time at rest is related to the speed of light?