Thanks for the answers @heykishan !!
Sorry for my late reply. Your answers were lucid.
My other questions were about the expansion of the universe and dark matter observation. As I mentioned earlier, both my questions are “how-what-ifs”.
Using the analogy that, everything we observe is slowed down because of the vast distances of separation and finite speed of light. Like, even light from sun is supposed to be 8 minutes old. My question is, while observing and hypothesizing that boundary of observable universe is expanding (you had mentioned 45 billion light-years, if my memory serves correct) we are essentially speaking the boundary was expanding some 45 billion years ago. This instant, whilst I type, the boundary MAY have stopped expanding or even began crunching , right? So, how are we actually accept this theory of expanding universe? I understand the Doppler shifts and you can answer with that stand-point.
Second, you had mentioned an anomaly ( don’t know whether I’m using it right here) that the systems in the outer edge of a galaxy move faster than its inner regions… and this is an observation indicating presence of dark matter.
What if, the gravitational effect of the supermassive black-hole is yet to reach its outer rings to slow’ em down ( I base this argument on the fact that gravitational waves propagate thru space and time, as was recently discovered, and so does the black holes effect, right?). This argument if true, should be observable.
In both my questions, I kind of think, information(light/EMR that we observe)is reaching us slow (by million of years), how are these observations accepted and used for developing theories?
That sums up my questions for now.