Based on my understanding, Hubble sphere is the region that contains GALAXIES receding subluminally while GALAXIES outside are receding superluminally (obviously on the border, GALAXIES recede at the speed of light). Particle horizon is the limit of what we have seen so far since the (big bang? Light scattering? Or the light spectrum reached visible due to redshift?) *So far I think I understand the hubble sphere but when particle horizon comes in, I'm confused, so many questions. Event horizon is the boundary in which future objects can come into causal contact with us, beyond it are things that we can never have any information to. Questions: 1) The hubble sphere divides galaxies that recede superluminally and subluminally, so in an accelerating universe like ours, the hubble sphere should get smaller since galaxies will eventually recede faster than before, is this correct? 2) If the galaxies outside the hubble sphere are receding superluminally and the hubble sphere is getting smaller then we can never have any contact with those galaxies, so where is the particle horizon? Same as hubble sphere? I know they are not the same but I'm confused. I have read Cosmology by Harrison but I'm confused, there are a lot of clarifications that I need.