I'm a mad man. It wasn't too much extra work and it makes for a great easter egg of sorts, but I programed in realistic orbits for everything in the game.sounds like a wonderful use time for a budget minded developer. so launching in 2028 are we?
There is the standard "day night" cycle as the alien ship orbits the planet every hour or so, but everything else works too. If you play the game for an ungodly amount of time, the main planet will complete an orbit around the sun.