Don't get me wrong, I love the idea. I think it's really interesting and I've never actually considered it before. I'm just saying there are a couple big obstacles to tackle before we can reach that point. The brain has a structure called the suprachiasmatic nucleus, which interprets the light that comes into the eyes. It uses this information to release hormones like melatonin which cause drowsiness and sleep. It is true that you could block out light during the day and receive artificial light at night, but it has been shown that disruption of Circadian rhythm can cause metabolic problems in humans (ex: http://edrv.endojournals.org/content/31/1/1.long). But because this rhythm is just a 24 hour cycle, it would seem possible to have it completely reversed. It would be interesting to see the results of something like that.