The next two animations below show two light sources that are almost
outside the central point's horizon. This is similar to the case of
the cosmic background radiation, which was emitted only 380,000 years
after the Big Bang, when the universe was much smaller than it was
now, but which is only now reaching us some 13.3 billion years later,
having travelled a distance larger than the distance between source
and destination when the light was originally emitted!
The final two animations below show two light sources just outside the
central point's horizon. The light from the left and right points
will never reach the central point. This is perhaps easiest to see on
the first animation, even though both show exactly the same situation.
