Is a scifi setting of constant artificial light everywhere plausible? I'm thinking to the point that the average adult person has not gone out of a city and has no experience of general darkness (obviously he has knowledge of what night used to mean and what darkness is, under a cover for example, but not what darkness is like out in the woods). There are lights literally everywhere, in the very makings of walls/ceilings/etc with no OFF switch available.

I'm interested not only in potential implications of this, but also in explanations as to why this would happen (in a voluntary sense) and how it could be done. Closest plausible reason I have in mind is some kind of efficient energy producing and distribution method by way of light that needs to always be on, everywhere (though I'm not close to a how on this).

It's for a short story, so I may be able to dodge going too deep into it, but I want to cover problems and potential plotholes/inconsistencies.

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    $\begingroup$ What is the reason behind this? One cannot sleep well in illumination. The Pineal gland, which is producing the sleeping-hormon melatonin is triggered by darkness. Long term illumination (e.g. MK-Ultra) raises health issues, lowers cognitive abilities, makes aggressive and so on. $\endgroup$
    – jawo
    Commented Dec 1, 2014 at 11:50
  • $\begingroup$ Idea: Overpopulated underground bunker, space station or other hermetically isolated scenario. To save space, people work and sleep in shifts. Simulating a day/night cycle would be unfair towards those who are on the night-shift, so it's always day-lighting. $\endgroup$
    – Philipp
    Commented Dec 1, 2014 at 13:18
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    $\begingroup$ Even at the sleeping areas? This had no benefits but disadvantages. In working and living areas yes, but in sleeping areas none at all. And why shouldnt there be an off switch? If you don't use chemicals to produce the light from luminescence but by any electricity, you can turn it of. And even luminescence could be covered to make darkness. $\endgroup$
    – jawo
    Commented Dec 1, 2014 at 13:23
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    $\begingroup$ It's the basis of the plot of Asimov's Nightfall (where the characters are nominally not human, so they may have different physiology if the story calls for it). $\endgroup$ Commented Dec 1, 2014 at 17:08
  • $\begingroup$ So there are lights on the undersides of beds, on the shadow sides of persons, on the palms of your hands, and the inside of your eyelids so that the concept of darkness is gone. Kind of a stretch. $\endgroup$
    – Oldcat
    Commented Dec 5, 2014 at 18:51

5 Answers 5


1. Constant light harms your health.

The Pineal gland, an organ which is producing the sleep-hormone melatonin, is triggered by darkness and give malfunctions if there's constant light at long term. The CIA made some experiments with that in the MK-Ultra program, just google it.

The people get desorientated, aggressive, depressive and have massive cognitive malfunctions and impairments. So at least for sleep you need darkness.

2. Artificial light

Is not the same as natural light! The Body needs UV-B to produce vitamin-D. Vitamin-D deficiency can lead to many physical and psychical issues like depression, nervousness and so on. Even illuminant to buy which are declared as "daylight" can not prevent this.

Also, it seems like artificial light can raise cancer. Don't panic, its always a question of intensity.

3. How?

There are multiple ways you could bring up constant light. We are not only able to do so, but we really do. Think of facilities which are running 24/7 to produce goods. Large and expensive assembly lines as like in car-constructions are good examples for that. Due they are so expensive, they have to run continuous to be economic.

Other examples are control room of naval vessels or the International Space Station.

So 24/7 light isn't a real problem. You only need a UPS to make sure the light keeps up during blackouts. Look at modern LED-Bulps, they need very low energy. If accumulator get better capacity in future, UPS can keep them up for long. Redundant energy pruduction will help a lot.


Technically it is possible with easy.

But it makes no sence due it would bring massive health issues.

  • $\begingroup$ Is the pineal glands trigger via the eyes (IE, putting a blinder or shade over the eyes would trigger the same effect as darkness despite the body being bathed in artificial light)? And just to add - the dull sound artificial lighting comes with could also be an issue. $\endgroup$
    – Twelfth
    Commented Dec 1, 2014 at 20:00
  • $\begingroup$ @Twelfth, I don't know about the pineal gland specifically, but the body's day/night regulation uses the entire skin surface to detect time of day. $\endgroup$
    – Mark
    Commented Dec 2, 2014 at 1:47
  • $\begingroup$ I cannot prove it, dont know where I've read that, but the pineal gland is also triggered through cranium. Even if almost no light is coming through, it still some and the wavelenghts do their jobs, as Samuel postet in his answer. $\endgroup$
    – jawo
    Commented Dec 2, 2014 at 6:16

An always on light source could simply be the local star for a tidally locked planet and people can easily thrive in constant illumination.

There is no such planet in the Sol solar system, yet. I could imagine that such a situation would be ideal for a distant (greater than 1 AU) planetary body where a city or base needs to have constant daytime in order to receive enough energy from the sun to keep its population alive.

The implications of constant light are not so devastating, depending on the intensity of light. Firstly, for humans, the circadian rhythm and normal melatonin secretions will only be disrupted under very bright conditions (greater than 3000 lux). On Earth, you, like the many animals that inhabit the arctic, can live there in the local summer where the sun never sets.

Besides, we have eyelids, if we close them when it's bed time we can fall asleep even with the lights on. The pineal gland doesn't know the difference. Melatonin is suppressed with blue light and light filtering through closed eyes has very little light of that frequency range. If you want to get tired before you close your eyes, remove blue light from the spectrum or wear blue-blocking glasses.


If the people living there are biologically similar to us then this would not be a good idea. Constant light is highly disruptive to sleep patterns and actually bad for your health.

Even if the lights had to be "always on" then they would be recessed back and have blinds or shades to pull over them to give you the ability to effectively control the light level in a room.

If the people in question were modified to not require sleep then in that case it might make sense to have always-on light if they were cheap enough to run. Even then it seems like a strange choice to make.

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    $\begingroup$ This is not an answer to the question but a rehashed version of my comment. $\endgroup$
    – jawo
    Commented Dec 1, 2014 at 13:06
  • $\begingroup$ @Sempie The question was "Is a scifi setting of constant artificial light everywhere plausible?" The answer is no. I then went on to discuss blinds/shades and modified biology neither of which you mentioned. $\endgroup$
    – Tim B
    Commented Dec 1, 2014 at 13:09
  • $\begingroup$ Blinds being a way someone would use the "always on" light technology without having constant light. Modified biology being the way that constant light might actually happen. $\endgroup$
    – Tim B
    Commented Dec 1, 2014 at 13:12

I imagine the critical point is not how but why. It's definitely possible, but it's tough to be a human when the lights are always on, due to the reasons that are listed in all of the other answers.

This, however, points to an intriguing possibility: what if the space the humans are inhabiting isn't designed for humans? If an alien race evolved on the bright side of a tidally locked planet, darkness could be incredibly strange and unnerving for them. They are used to it always being bright and hot (and probably windy). If they designed a space station or city on a spinning planet, it seems likely that they would always have light everywhere, even in their sleeping quarters, since they have not evolved with a night.

Likewise, a structure for robots might always have lights on, since they don't need to sleep. This would make sense if it was cheaper to build lots of lights than it was to build eyes that are good at seeing in the dark. They also might run off of photovoltaics, in which case a constant source of light would keep them charged at all times.

In both situations, it would be tough to be a human. I imagine that people would probably want to construct dark spaces just to have some respite from everything constantly being bright.


If you had 10 lightbulbs with 100 watt each per square metre it would be like summer daytime with no clouds, all the time, everywhere. It may get a bit toasty!

Maybe people would even literally be afraid of their own shadows, since they had never seen them before. Also some lights would have to be UV light (UV-B to be precise) just so that you wouldn't get vitamin D deficiency. Also seen as light bulbs get quite hot if you had them in the floor then it may get uncomfortable to walk.

I have not considered the sleep issues as these seem to have already been discussed. This is just the first thing that popped into my head when I read the question.

In addition this may get quite expensive to run.


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