I prefer total darkness and white noise when I sleep...I think it has something to do with melatonin reacting to light...to be honest, though, I could fall asleep any time, any where...it probably depends on whether you have trouble sleeping more than regular sleep patterns...

This might help explain the fire question...
[io9.gizmodo.com]

It has to do with our circadian rhythms, which are triggered by light.

I work nights so getting the room dark helps. I think it helps over all get to sleep faster.

Fire light is both much less blue than daylight and a lot weaker, our eyes and brains compensate for the low light so much that we do not notice how dim it really is. You do not really need to cut out all light only full spectrum light with a high blue content, which is how your brain tells daylight from firelight. Interestingly there has been some research done which shows that we are just the opposite when very young, and that babies sleep better with some light and noise, perhaps because that means that adults are near and therefore they are safe.

I'm a darkroom person..always have been,just my preference I guess..

I've slept with a good quality sleep mask on at times. It helped a lot. I prefer a very dark room and colder room. I can't sleep in the heat.

I would suspect that's evolutionary? That the dark told our brains to shut down and go to sleep for the night. That would make sense. The colder temp. makes sense in that scenario too.

My house caught fire once and since then I have always slept with a night light on. Also, we have major earthquakes here that seem to happen in the middle of the night. I sleep just fine, no issues.

I can sleep anywhere While in Marine Corp I slept next to a carrier's generator which is by no means quiet.

I prefer a dark room, though I have found to be able to fall asleep in a tent in daylight, in a conference room during a meeting, or watching tv. Just depends on how tired or bored you are, I guess.

It helps me to have it as dark as possible. My ex couldn't sleep if you didn't cover the light om the cable box. She was light sensitive.

Like others have said, I think it boils down to individuals.

I shared an apartment with a friend after our high school careers ended. We were broke, so our apartment was a large converted storage unit. It was 3 spacious rooms and a bathroom. It was built without windows and the door was a big security thing that was heavy. We stuck a towel under it each night and were plunged into complete darkness. It didnt have to be night for it to be pitch black even. Opening the door in the morning was like emerging from years of living in a cave.

Best sleep I've ever had, and I've been trying to recreate that blackness ever since.

I see it more as a need to compensate for the artificial light which has been introduced into most of humanity's environment in the past century or so, artificially extending the scope of work (both paying work and housework and intellectual stimulation and so on) and confusing natural biological rhythms. Also, fixed work schedules that don't flex with changing sunrise and sunset. With all this in play, it makes sense that some people would benefit from forcing their sleeping environment to be pitch black as it would have been before electric street lights and so forth, and to sleep in total darkness when convenient, even if the sun is up.

Campfires don't burn by themselves all night, they die down. They are a point source of light and warmth and a different color temperature than halogen street lamps (for example).

Personally I sleep well enough that I doubt blackout curtains would make much of a difference for me. I'd probably gain more from doing something about my prostate issues so I don't have to pee 3 or 4 times a night. Everyone's different.

It does occur to me there is a relationship with sleep and light. Humans are a diurnal species, meaning that they work on a dual cycle of light and dark. This doesnt mean that it has to be totally dark. But it is also the reason for the high suicide rate in people who have emmigrated to the polar regions (e.g. Alaska) with 6 months light and 6 months of light.

It has to do with electro-magnetic fields. Every cell in your body has an electrical charge, and therefore susceptible to influence from external electrical fields. It has nothing to do with the amount of light in the room. I do not have sufficient knowledge on this topic to lend my support or refute. But this is the gist of the debate.

I have to agree I always have the TV on when I fall asleep set to go off within an hour and a night light I don't like stubbing my toe at nightand then that damn phone wakes me up in the morning usually in the middle of a good dreamso I can go to work again

Recipe for a good night's sleep:
DItch the screen before bed
Dark cool/cold room
Good duvet
Warm body in close proximity

I have come to relish a simple black sleep mask. It cuts out ambient light, and now just putting it on hastens sleep.

There are many studies that suggest light color and intensity can adversely effect the circadian rhythm.

I find I sleep better when my monitor (connected to video sources in the bedroom) is off then when I don't bother powering it down.

I have blackout material between the cellular blinds and curtains that cover the six windows in my bedroom.

For me, I tend to get to sleep and sleep better when the room is dark.

As long as I don't have a bright light shining directly at my head, I can sleep
in any kind of room.
I have east-facing windows. I created a removable black-out covering for them.
It's really helpful, especially in the summer, when the sun is up earlier than I am.

This makes perfect sense to me. Everyone is different and every circumstance is different. When I was in basic training we were often so tired we could sleep anywhere and I can remember falling asleep sitting on a washing machine is a brightly lit room. When sitting at a speech I am always falling asleep and worry I might fall out of my chair. I can easily fall asleep after lunch in a reclining position after reading a few pages of a book and exactly 20 minutes later be wide awake. Night time can be different and one little worry can keep me awake. I have gotten to where I need a dark, cool and perfectly quiet room. I understand and totally believe the problem with the blue light from electronics and try to let at least 1 hour elapse between computer/TV and bed.

There is always a level of light that won't interfere. But most of this articles are written for people with problems to sleep. And in this case it might be a sensibility to light, so no light can help.

It depends on the person and other factors. In my case, meds that I must take to prevent migraine pain (which became present 24/7 in menopause), induce horrible hypnopompic/gogic hallucinations. These are greatly impacted by my ability to see any light when my eyes inadvertently open during sleep. I often long for a more completely dark room to see if the frequency of nightmarish hallucinations would be reduced.

Some of what the scientific community knows about light and citcadian rythms is summarizeded in this linked review article. I have not waded through all of it, but wonder if we understand what the impact of low levels of light typically encountered during the night might be, if any. Some level of night vision is a good thing, safety wise. If we slept outside, seldom would any night be completely dark...

[ncbi.nlm.nih.gov]

No, it's true but some are more sensitive than others.
Growing up, I had a room created by my dad in the basement that had no windows. With the door closed, the only light in the room (with the lamp off) was the tiny glow from my electric alarm clock (dim red). In that amount of darkness, once I was adjusted to that light level, it illuminated the room allowing me to see quite well.
I could also "see it" through my closed eyelids, and that would help awaken me a few times a night.
My brother however could sleep in direct sunlight if need be. ?

Ever since I had a severe panic attack in the middle of the night some years back, I've found I can't sleep in total darkness. Yeah, I use a night light, or I pop the shade a little bit so that light comes in from the street lamp. It's helped me ever since.

I need a bit of ambient light in order to sleep. My parents live out in the country and I struggle to sleep when I visit because it's too dark. I'm used to the street lights of being in the city.