Using 21st Century Western Anglophone society as a baseline:

How would the infrastructure of cities (For example shared leisure spaces, transportation networks and homes) differ from our own in order to accommodate the specific needs of following alien society on their home planet.

Use facts and citations, and do not proffer opinions, or any content that is off topic.

Please excuse the extraneous detail, but this has been added in an attempt to avoid deletion on the grounds of "opinion" and "open ended".


On an Earth like planet with a comparative level of technology to 21st century California, there are two species. They are "rubber forehead" aliens and share the same essential physical form with each other (and with humans). They breath the same air and eat the same food. They have separate languages, but each is taught the other's language in school. So being at least partial bilingual is common.

One species is exclusively nocturnal and the other is exclusively active in the daytime.

The nocturnal species has good night vision, but is less sight orientated than the daytime species. They are very sensitive to UV light. It burns their skin very easily and hurts their eyes.

The daytime species is dependant on UV light. It is a significant factor in their metabolism. Without it they quickly become sluggish and eventually dormant. Low light levels put them in to a "dumb" like state where they can perform basic tasks such as turning on a UV lamp, but not higher functions such as reading or writing.

The two species use the same city infrastructure such as public transport, shops and restaurants. Just not at the same time.

Their cities essentially have a day shift and a night shift.

There is minimal physical crossover, except at dawn and dusk as one species is going out while the other is going home.

Otherwise, there is a "Zootopia" vibe. Specially adapted facilities, but largely shared commercial and industrial spaces.

This world is not an allegory for modern day discrimination or segregation, and those issues are out of scope.

  • 1
    $\begingroup$ "How would such a civilization be different from our own": Who is we whose own civilization serves as a baseline? Chinese, Indians, Dutch, Zulus, Arabs? "they don't occupy the same space at the same time": Since this world apparently does has neither windows with curtains nor artificial light sources, the civilization is clearly profoundly different from "ours". $\endgroup$
    – AlexP
    Jun 8, 2022 at 19:48
  • 1
    $\begingroup$ Ok, so comparing Morlock and Eloi should be a good start for you :) $\endgroup$
    – Alexander
    Jun 8, 2022 at 19:50
  • 1
    $\begingroup$ Just wanted to share this fun vocab word: active in the daytime = diurnal. $\endgroup$ Jun 9, 2022 at 13:26
  • 2
    $\begingroup$ The edit didn't really help narrow it down. This is incredibly broad at present. You've not specified the society that is "our own" from which it might differ - there are so many cultures on Earth at present, and many differing lifestyles within each culture. Please focus the question down to a single problem with an identifiable solution. Also, asking for an infinite (unbounded) list would be too broad and way too much for the site. $\endgroup$ Jun 9, 2022 at 19:02
  • 3
    $\begingroup$ VTC because (a) No matter what facts and citations are involved, how a society (culture, politics, philosophy, demographics, biases...) might evolve its infrastructure (which has more to do with physiology than diurnality/nocturnality) is very subjective and opinion-based. (b) Demanding citations and facts when you're asking about a fictional alien society is irrational. (c) the Q is too vague and broad- some human cities have elevated trains, others have bike paths. Do you have a specific Q? $\endgroup$
    – JBH
    Jun 19, 2022 at 7:56

4 Answers 4


Just some jumbled up thoughts I threw together after seeing your prompt.

The interesting imbalance here is that daytime people are not in danger in the dark whereas nocturnal people are in danger in the light. This means that daytime people can build a world where they don't need to be protected at night, just be at home, so they can have windows with no curtains even at night. Nocturnal people need to keep out of the light to not burn.
This could create some resentment towards the daytime people since they are more free in what they do and build.

Daylight people
Depending on the tech level of this society, UV lights would be put in places where daytime people want to stay awake (factories, libraries, maybe even at home). Their houses would be similar to ours but with many many windows and roof windows. They'd develop glass that allows 100% of UVs to pass through, and use this glass all over their buildings. Trees and shelters would be cut down or be minimally present in cities in order to maximise UVs reaching the people. The fact that plants "take" UVs from them means that plants would be seen as bad.

Nocturnal people
Nocturnal people would develop better eyesight or use night vision goggles (again depending on tech level), or rely on other senses. They'd carry out activities that don't rely on vision for accuracy. They'd live in basement apartments and bunker houses, or just windowless houses. Their religion/culture would probably be based around stars, constellations and planets.

They would probably not live in the same neighbourhoods as noise would be an issue for the sleeping people. There would be a day and a night shift for everything (police, hospitals, shops, factories). There would be constant productivity but the city would also have to keep their services open 24/7.

Even with little physical overlap, I'd assume people would develop connections with each other if only by leaving messages (letters, texts, internet). People are social beings and crave the unknown: they'd want to learn about "the other side".
Then there would be those that seek to increase the divide (depending on the drama you want in your story), by weaponising UVs for example.


Absent the capacity for a dialog between the two, one would genocide the other in short order. For that matter, even if they can talk, it's anything but clear that massacres will occur (at least if they're human-like... we're pretty massacre-happy after all).

They do compete in all the different realms that people exist in, for real estate, for resources, etc. There's not much synergy here. You can run two shifts in factories, maybe, but you only need double that production because there are double the number of people in a city/region/country. They're not going to want to share sleeping arrangements... the nocturnals likely need something pretty dark, the daypeople won't much like large blackout curtains and the like.

As much as an economy is strong from the amount of natural resources available, then people who you never talk to, never befriend, are never invested in are halving your own standard of living.

Worse still, farming is something that tends to require day-living, does it not? Even if one posits that they do the garden-keeping and animal husbandry at night only to harvest on following nights... this again just puts them at odds with the daypeople. Real estate (prime farmland is uncommon). Irrigation water is always limited. Deposits of mineral fertilizers, etc.

Given all these things, even if there is some overlap in early mornings and late evenings where they can communicate, how likely is it that the words would be anything more than threats, and non-idle ones at that?

No evolution is possible here. They will have long since wiped one or the other (or both) out before they ever learned to live together, and if they did learn to do that they'd discover very little benefit to doing so.

The only reason this doesn't apply to humans themselves is that with us enough of us are awake to fend off attacks from invaders. And woe when that isn't the case.

  • $\begingroup$ You're going off topic. But to address those issues, there's no need for war or conflict, they're sharing the same space but at different times. Farming needs daylight, but farmers can farm crops at night and leave them to grow during the day. They don't socialise, but they're still perfectly capable of watching each others TV or reading each other's books. $\endgroup$ Jun 9, 2022 at 8:45
  • $\begingroup$ This is a fair point. If you say these aliens are like humans in all ways but one, then you cannot reasonably claim they don't all kill each other. Humans like to kill each other. Perhaps you can add an external reason. $\endgroup$
    – Daron
    Jun 9, 2022 at 11:31
  • $\begingroup$ The bit about evolution has already been explained. They evolved on separate parts of the planet. $\endgroup$
    – Daron
    Jun 9, 2022 at 11:31
  • $\begingroup$ @AaarghZombies They don't share the same space at different times... their crops don't get rolled up and put away in the closet at dawn. They're virtually no space they can share, for that matter. $\endgroup$
    – John O
    Jun 9, 2022 at 13:06
  • $\begingroup$ @John O, why would they need separate crops? Surely since they evolved on the same planet they'd eat the same food? They could also use the same buildings. Imaging an office building that had both a day shift and a night shift. Even things like public transport, they'd just use the same trains but at different times. The could even live in the same apartment blocks, only one has sun lamps in their homes and the other has blackout blinds. $\endgroup$ Jun 9, 2022 at 14:59

Intelligent species adjust

Both species are intelligent. May be initially there are conflicts (like WW-I or WW-II) but at some time, all will agree to survive and make adjustments. Minor conflicts will remain but massacre will come to an end.

Different countries

In humans, people of similar habits, religion, ideology, language and culture live in their countries (Chinese, Indians, Dutch, Zulus, Arabs). That is how countries were created. But there are migrations and adaptations.

In your world, nocturnal and day people can live in different countries or places on the planet with suitable habitat. But there could be some migrations and adaptations and co-existence in some parts of the planet.

  • $\begingroup$ Can we presume that any conflicts were resolved at an earlier time in their history. I'm going for a Zootopia vibe. $\endgroup$ Jun 9, 2022 at 15:03

Dormitories and the Wayfaring Youth

enter image description here

On Earth, the houses have the bedrooms next to the living space. During the night, people use the bedrooms and the living space is empty. During the day it is hard to sleep when people are downstairs making noise.

On your planet people share bedrooms. Day people use a bed at night, and the same bed is used by a Night person the following day. To not wake each other, the sleeping quarters are separate buildings.

Perhaps you buddy up with the other kind of person and share the same bed every cycle. Or perhaps you use a different bed every night.

This leads to a civilization with less privacy than Earth. On Earth the bedroom is a private area where teenagers lock themselves inside when they are upset. Your world has no such equivalent. Where do the upset teenagers go instead? I leave that to your imagination.

It also leads to a civilization where mobility or temporary homelessness is easier. Provided you are happy to live out of a suitcase, you can sell your home, start a new job in a different city, or travel around the world at your leisure. There will always be a bed for you in the local dormitory.

The problem of buying a house is not so urgent for the people of this world. Many people do not own or rent living quarters. There are many recreational facilities that cater for these people during the day (or night). Places they can relax when they are not working or sleeping.

  • $\begingroup$ Hotbunking for houses? i'd never thought of that. Cool. $\endgroup$ Jun 9, 2022 at 12:21
  • $\begingroup$ I fear there might be housemate-sharing kind of issues. Since the originating cultures are different, I bet they would cry when the other(s) didn't open the curtains and clean the fridge. Again :p. It would have been easier if people shared the same culture. $\endgroup$ Jun 10, 2022 at 3:10
  • $\begingroup$ @Tortliena There is no fridge in the dormitories. $\endgroup$
    – Daron
    Jun 10, 2022 at 9:00
  • $\begingroup$ @Daron In the living space, yes :). It would happen everywhere the facilities are shared. $\endgroup$ Jun 10, 2022 at 10:08

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .