Content was low on this site last week for a reason, I got sucked into EVE Online, which has a Linux client (though the advanced shaders don't work on Linux so it doesn't look quite as cool as that screen shot). EVE is an MMOG that is on universal scale. There are something like 5000 star systems in the environment (I've been to about 10 now). The environment is basically always running, which means your character progresses in his training whether or not you are in the environment.
They are striking an interesting balance between real persistence and fake scenarios to give players more to do. If you get a mission from an Agent (who is an NPC), that mission occurs in "dead space", i.e. off the disc of a solar system, with the Agent's coordinates to get you there. Unfortunately those areas are wiped clean pretty quickly after the mission is completed, which I found pretty annoying. On one of the missions I went on there were some valuable asteroids there, which I bookmarked, ran away, and ran back with mining equipment to mine. The ship wrecks were there when I got back, but the asteroids were not. It is a minor ding against a game like this, but one that did break the illusion that the environment was there whether or not anyone was watching it.
All in all, the game is incredible. I shouldn't have started it prior to my grad class kicking off this semester, as I don't really have the time to play. However, given that you can just train sitting on a station, I'll probably sign up to keep the account and play a bit on weekends from time to time. It is a nice distraction.