I have been watching Susskind's lectures on Cosmology which are great. There is something that I can't wrap my head around. I know that if we look far away enough into the past (about 100,000 years after the big bang I think he said) , the radiation that is being emitted comes from plasma and as a result blocks any light from getting to us from beyond. This is what I understand to be the surface of last scattering. I also get that the Hubble law states that v = Hd and as the Hubble constant approaches a constant value, there exists a cosmic horizon defined by d =c/H such that any object that passes this distance will not be observable since it would have to send a message at faster than the speed of light in order for us to observe it. I think Susskind said that the surface of last scattering would always be within our cosmic horizon. How can this be if the cosmic horizon remains fixed? If the deonized gas which makes up the surface of last scattering is moving away from us at a faster and faster rate, won't it eventually move beyond the cosmic horizon? Where am I messing up? What I am visualizing wrong? Thanks.