# How does cosmic horizon work?

This is about the horizon which divides us from stuff that is too far to see because it's moving away from us faster than the speed of light.

If point $A$ and $B$ are so far away that $B$ is a bit outside $A$'s horizon, what if I look at the point $C$ that's midway between them? It will get light from $B$, because there's nothing from stopping that happening. However, any light at $C$ must be moving with speed $c$ with respect to $A$ while $C$ itself is moving slower. Therefore, any light that is at $C$ should also reach $A$ if the direction is right (and it is, if it came from $B$).

Where is the flaw?