Particle Horizon and CMB If particle horizon is the maximum distance we can see presently in the universe, how come we are able to see CMB? CMB is radiation from surface of last scattering happened at t~380k years. 
Suppose universe is expanding at a constant rate ( i.e. no acceleration), will we be able to see CMB again??
 A: The particle horizon is the distance from which light emitted at the moment of the Big Bang will just now be reaching us.
The CMB was emitted 380,000 years after the Big Bang. So the CMB radiation we see has been travelling for less time than the light emitted at the Big Bang, and therefore the CMB radiation has travelled a shorter distance than the particle horizon.
In other words, the CMB horizon is always inside the particle horizon, so we will always be able to see it.
A: If recombination were been an aisled event, i.e. something that happened in a certain place with some finite spatial extent, then it is possible that light didn't have enough time to reach us from there (this event happened outside the particle horizon).
However recombination was not an aisled event, it happened everywhere in the universe at the same time, light scattered for the last time in all directions.
From our location in earth CMB was emitted as well, but those photons are now very far away from us. The photons that we do see are those that were far enough at the moment of last scattering so that their trajectories are meeting us today. That is our surface of last scattering
If another planet lying outside our observable sphere looks far enough they will also see their own last scattering surface, they will also observe the CMB.
