Sometime about noon yesterday I looked outside and noticed that our mountains were missing, as were any other terrain features more than a couple of miles away. Naturally, I jumped to the conclusion that the simulation we live in had glitched, wiping out all those pixels. Possibly that conclusion was influenced by the fact that I had heard that some of the intelligentsia of my universe (OK, Scott, Bee, and Lubosh) were arguing about the world as a simulation.
Actually I didn't bother to read their stuff, mainly because past experience has indicated to me that such discussions, where predicated on any logic whatsoever, usually are based on assuming that the simulation exists in a universe with laws of physics similar to or even exactly like our own.
Doh! Why would anyone do that? Real simulations, in our universe, aren't like that. Mostly they use simplified physics to try to capture a few elements of reality, or just imagine different physics to see what happens. So if we are a simulation, whatever that means, it's likely in a universe governed by perhaps unimaginably different physical laws.
Anyway, after a while a different explanation occurred to me: perhaps the cold front that just moved in with violent winds had stirred or advected enough of our desert dust to obscure everything further away - it certainly looked dusty out there. Of course my first guess might be more likely, but see title, above.