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.
Clinicallydepressedpoochie@lemmy.world 1 day ago
My point is, it doesn’t reveal anything about the nature of the universe only about the limited view we can observe.
Tinidril@midwest.social 1 day ago
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 a bit brain bending.
NotLemming@lemm.ee 21 hours ago
So when you say never, do you mean not in the ‘lifetime’ of our sun, or?
JohnDClay@sh.itjust.works 21 hours ago
Not till the heat death of the universe.
Clinicallydepressedpoochie@lemmy.world 1 day ago
I would say yes they are part of the same universe because if you changed your position it would reveal things you didn’t see before and mask thing you use to see. Not that that is possible yet, but there are no laws of physics preventing it, only our super short live spans.
Tinidril@midwest.social 23 hours ago
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.