(In this discussion we are ignoring any thermalizing interactions that would prevent direct contact with particles traveling at the speed of light from anytime in the past, even from the singularity, t=0) We still can't see to the edge of the existing universe. We can only see a portion of it. The universe is said to be e^60 times bigger than what we can see. Are you saying that at t=0 we can see all of the universe and that much of it has since left our view? If we could see ALL of the universe at any time, then what horizon did it cross so that we can no longer see it. If we could not see all of the universe at t=0, then does the principle that only premits partial view act itself as an horizon?hellfire said:At least in principle, or from a pure theoretical point of view, I do not see any impediment to see back to t = 0. Inflation is a period of expansion as any other, the only difference is that expansion is stronger. If we would be able to see some source before or from the beginning of inflation this would be located extremely far away today, more than 45 Gly, that is the current location of the particle horizon without considering inflation.
Or perhaps if we could see without obstruction to t=0 to the very singularity itself, then would that constitute an horizon of zero size and zero surface area and thus zero entropy?
I still get confused when I study the paper "Expansion Confusion" found at:
I look at graphs such as Fig 1, page 3, and Fig 3, page 11, and I see our light cone intersecting both the Hubble sphere and the particle horizon. And it would seem that trying to look down our light cone past the Hubble sphere we would encounter light moving towards us in space moving even faster away from us so that we can not now observe it on our light cone. This would seem to be a horizon. However, this intersection with the Hubble sphere occurs at about t=4Gyr. And we know we can see past this to the surface of last scattering at t=300,000yr. What's going on?