My layman understanding is that the universe is much bigger than that we can observe however due to the cosmological constant the observable universe is the matter etc. that is not moving away from us at a speed faster than light.
The two circle's indicated are the observable universe from their own perspective, A can never reach B as he is moving away from him faster than light and vice versa. A and B can however reach C, so they both decide to go there to meet up.
My question is would they ever actually reach each other?
From my research I know (without understanding the maths) that even moving towards each other at 0.99c they will still only move towards each other at say 0.9999C (basically never above light speed) but it seems that matter from outside their observable universe could reach them. I have tried to find an answer and found that perhaps when A and B get to C their home universes have now moved away so that neither could ever get home (which means A will never see B's home galaxy and vice versa) but this still doesn't explain how A could reach B (if it even can). I may be misunderstanding the expansion / observable universe but from what I have read the above logic (A never reaches B) should be correct?