I came up with an idea on the new FES, that I thought of posting here because most of the serious discussion seems to happen on here.
Basically, I considered a second UA, one that passes through solid objects (so that we are not shielded from it by the Earth), but that only affects electromagnetic radiation. This "Electromagnetic Accelerator" (EA) would cause significantly greater acceleration than the UA does, such that light accelerates upwards relative to the surface of the Earth. This would explain a couple of phenomena:
Day/night
When the sun is too far away, all its rays are bent upwards in a parabolic arc before they reach us.
Horizon
Light from objects too far away either hits the ground or is bent upwards before it reaches us. This also explains the "sinking ship" effect: the bottom portion of the ship appears to sink into the ocean because all of the light either hits the ocean or is bent upwards, but light from the top portion will be able to go further down before being bent upwards and becoming visible to us, since the ocean is lower relative to it. Also, this allows for an extremely high Greater Ice Wall to keep the atmosphere in, while remaining invisible.
This idea is still fairly fresh in my head, and it is based upon an idea someone else came up with (I don't remember who), stating that light from the sun is bent upwards - though for a different reason, I don't remember the specifics. Undoubtedly this hypothesis will gain more detail as I consider it further, I just thought I might post it here for your consideration too.