Re:Gravity Kills Schrödinger's Cat
by JadeNB on Saturday June 20, 2015 @06:19PM
(#9751243)
What if the light cones of A and B don't intersect at all? There are certainly places in the universe so far apart that light not only can't now, but could never, have travelled from one to the other; that is part of why the near-isotropy of background radiation is something that needs to be explained, I thought.
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Are there regions of the universe that have never been causally connected? They all originated in the same event, so I'd be surprised if that's true, but I'm no expert. I know cosmic inflation during the big bang was superluminal, but I have to concede I'm not completely familiar with the consequences of that, so good point.
Indeed, the fact that they are moving apart at superluminal speeds is exactly why they have never been causally connected. The fact that such non-causally connected islands still "look the same" is called the horizon problem (https://en.wikipedia.org/wiki/Horizon_problem), and it is one of the issues that Guth's inflation might solve (https://en.wikipedia.org/wiki/Inflation_(cosmology)#Horizon_...).