As I just explained, it’s not really about observation, it’s about causation. If two objects can never possibly interact, then are they really in the same universe?
Looking out in space is also looking back in time. Anything (roughly) that is further than we can observe in the microwave background would be further back in time than the beginning of time, and therefore doesn’t exist at all in our universe. It’s a bit brain bending.
Thus the term “observable universe”. Everything beyond our observable universe is being expanded away from us at faster than the speed of light, so nothing outside will ever reach us. Causality is completely and irrevocably severed at those distances so, arguably, anything outside the observable universe is not part of “our” universe.
I’m not sure “drifting” is quite accurate.
That’s kind of a weird question. Russia isn’t communist and arguably never got further than state capitalism under the Soviet Union. Russia is certainly a dictatorship/oligarchy now, but so is the US (with extra steps that are currently being dismantled anyways).
That’s just it. The laws of physics, at least as far as we understand them, absolutely preclude changing our position in any way that would reveal anything outside our observable universe. Lifespans don’t come into it at all. If you lived forever traveling at the speed of light, you would never achieve that change of position.
The cosmic background is the leftover “noise” of the big bang, and we observe it roughly uniformly in every single direction. So where did the big bang occur? Everywhere. Everything that exists is precisely at the center of the universe, right where the big bang happened.
It’s all about the concept of spacetime. Spacetime isn’t space and time considered together, it’s a singular thing that operates by rules that we are ill equiped to comprehend intuitively.