Art Somerville's Nave Gallery has brought us thoughtful installations before, but their new "Ghost Town" sounds positively compelling. Artists imagine our earth in a process of transformation, with cities growing and shrinking, populations moving, people interacting with nature, and everything cycling both naturally and unnaturally toward growth, decay, and chaos. Might sound like a bunch of hippie nonsense, but we think it makes for some appealing art. "Ghost Town" runs through March 21 at......