If you wake up when the sun rises and sleep when it sets, you maximum your use of daylight, and minimize the amount of artificial light you need. In addition, your body is kept in its natural circadian rhythm. There are clear patterns of brain wave activity, hormone production, cell regeneration and other biological activities linked to this daily cycle. As part of my Optimization Theory, I will be following this cycle myself, except when I'm attending an all-night party. At other times I will be using olive oil lamps to the light my house (see this previous post). The lamps have a pleasing, lambent glow to them.