[snowwrestler]

If the point is to match our natural heritage of the stars and moon, then 100% blackout is not actually accurate. Even on a moonless night, starlight is quite bright--bright enough to see contours of the landscape.

I've slept outside in remote places many times, far away from city lights. It's not even near 100% black. So I would not kill yourself to get every little stray bit of light.

[AndrewKemendo]

For me it is not the point to match a "natural" (whatever that is) sleeping environment. Rather, it is to reduce the number of things that will disturb me while I am trying to sleep.

I don't prefer to wake up when the sun comes up mostly because I don't prefer to sleep when it goes down. So it is a guarantee that I will want to be asleep when there is a significant light source outside my house. Eliminating that will optimize my sleep. End of story.