[lend000]

This is awesome. The effect of light on our biology is truly incredible -- I have a bad habit of not being able to get to bed before 12am, even if I want to (I know many here will scoff at that), but when I go camping and I'm without unnatural light, I'm exhausted by 9pm and wake up at sunrise. My sleep cycle adjusts the first day.

When I use a campfire, I usually stay up significantly later, which is interesting. Just because the light is "natural" does not necessarily mean it's natural to have the light at a certain hour.