It doesn't have to even be complete darkness, you just can't be in sunlight. There is a part of your brain that controls your body clock and it relies on the sunlight to tell you when to sleep. If put in lets say and underground bunker, you are getting no input signal and your body clock goes haywire creating longer days and longer nights. Blind people still have normal days but people with no eyes at all can fall into and suffer from this cycle
@proxxxy, could you elaborate please? I've been studying some of these endocrine paths and I'm really curious if you happen to know, which gland and/or endocrine substance causes this "prolonged day" and what do eyes as such have to do with it? Thank you! :)
I'm don't know that much on the brain parts of it but on the eye things I can. On the blind people thing too, most people who are blind their eyes still work in giving sensory information to the brain. There have been studies of blind people that were sat in front of a monitor and shown faces of people smiling and yawning and they did these things too (similar to how normal people do). Their eyes still work in a sense just not properly. The light and dark your eyes are seeing (in non blind people to) resets your biological clock in accordance with the phase response curve (PRC just google it). Depending on the timing, light can advance or delay the circadian rhythm (basically your sleep cycle).
http://learn.genetics.utah.edu/content/inheritance/clockgenes/ fourth paragraph in the How do clocks affect sleep section. You do end up unsynced and with longer days than normal but it doesn't get as far as a 48 hour day. You might end up somewhere around an early 30s hour day.
It has to do with the part of your brain that controls your body clock. It uses the suns light as a sensory input to reset it each day. Without this input it becomes out of sync
It has to do with the part of your brain that controls your body clock. It uses the suns light as a sensory input to reset it each day. Without this input it becomes out of sync