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I am writing a sci fi novel in which one of the primary factions is a lost space colony sent to Proxima Centauri (Alpha Centauri C) roughly 350 years prior on a generation ship. The trip took roughly 80 years, leaving humans living independently in the system for around 270 years. I am playing with the idea of diverging evolution and the thought occurred to me that the exposure to light (as a component of radiation) produced not just by a different sun but three suns (as Alpha Centauri is a trinary system) is likely to cause our sight to change.

How would light in the Alpha Centauri system affect our vision long term?

More specifically I am interested in whether or not this might affect our ability to see further into the spectrum in either direction or even decrease our ability to do so. Also, whether or not it would affect the ability to distinguish similar colors such as separating blue from green and in-between variations like cyan and turquoise. Is there a possibility these colors may seem to blur together or that they might be more finely distinguished (not limited to examples).

For background, I imagine the colonists living primarily in sealed habitats both on planet and in space. There is no terraforming or miraculously habitable planets so they are mainly exposed to artificial light, but it is widely spread and common for individuals to both go on spacewalks and for habitats to have observation areas with large windows, which should allow for ample exposure to real sunlight. Lastly, there has been no overlap with any other humans since the generation ship left Sol, and the relatively recent development of limited FTL travel is part of what kicks off the story.

Obviously this is an interesting overlap between color theory, human biology, and physics, so I don't expect totally definite answers, but references would be nice if possible. The main reason behind this question is because I think it would be interesting if there was a situation in which an individual from Alpha Centauri could literally not read a display because of the color scheme, or if conversely they could see something that someone from Sol could not.

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  • $\begingroup$ It might help if you were to tell us a little about the light spectrum available on your planet in this trinary system. On the other hand, evolution tends to work through selective pressures over hundreds if not thousands of generations, and you only seem to be dealing with maybe 8-15 generations at most. Genetic engineering seems your best bet. That being said, tetrochromacy occasionally occurs in the normal human population, maybe you can expand on that. $\endgroup$ – BLT-Bub Nov 9 '19 at 6:25
  • $\begingroup$ @WeareMonica. Alpha Centauri is made up of Cass G, K and M type stars in order (A,B,C), and honestly the technically information about the produced radiation goes a bit over my head. That said, I would note that I read a study where a scientist was able to produce an entirely separate species of domesticated grey fox by selective breeding 20 generations (they reproduced almost every year, making it a nearly 30-year study). So assuming extreme circumstances and the increase in genetic variation due to radiation exposure I'm being optimistic with evolution's limitations. $\endgroup$ – TitaniumTurtle Nov 9 '19 at 6:50
  • $\begingroup$ If they're mainly exposed to artificial light, they're more likely to adapt to the artificial light which is going to be less luminous that the Earth's Sun's natural light levels. Windows might be a problem if Proxima is really a flare star. $\endgroup$ – IKM Nov 9 '19 at 7:20
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    $\begingroup$ Proxima Centauri is approximately one-tenth light year distant from both Alpha Centauri A and B. They will appear as a close pair of stars in the night sky. Their colonists' eyes won't have adapt to the light of a trinary system, but to the ambient color & the levels of illumination under the light of Proxima Centauri. $\endgroup$ – a4android Nov 9 '19 at 7:45
  • $\begingroup$ Color is a perception, it exists in the mind; it is not a physical quantity, it does not exist in nature. Our eye do not see color; color is synthesized in the brain from the raw data provided by the eyes. There is no direct relationship between any property of the light falling upon the retina and the color perceived by the brain; the perceived color of an object depends on lots of things, such as the color of nearby objects, the illuminant etc. That being said, here on Earth the color vision systems of primates is pretty much unique; other animals see color in a different way. $\endgroup$ – AlexP Nov 9 '19 at 8:04
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  • "The main reason behind this question is because I think it would be interesting if there was a situation in which an individual from Alpha Centauri could literally not read a display because of the color scheme, or if conversely they could see something that someone from Sol could not."

    This is very very obviously possible.

    Here on Earth, illuminated by our one and only Sun, different animal lineages see color in different ways. Among mammals, we primates are one of the very few lineages to have trichromatic color vision. Carnivorans, including our beloved cats and dogs, are dichromats, meaning that there are many many color combinations which we can easily distinguish but would appear uniform to a cat or a dog.

    Other animals, for example quite many insects, have more than three color receptors, so that they can distinguish color combinations which we humans cannot. Moreover, many insects see in the near ultraviolet, so that they can see patterns which are utterly invisible to us; do a search for flowers as seen by bees and be amazed. Moreover again, some insects can discriminate between light with different polarization, so that, for example they can determine the position of the sun behind a veil of clouds.

    These examples mean that here on Earth, where all living things are illuminated by the same sun, color vision, and the extent of the visual spectrum, varies dramatically between animal species. Aliens from outer space would almost certainly have a color vision system different than what we chimpanzees have.

    All this is because, in the end, the exact response curves of color receptors are the result of accidents. There is nothing in nature which says that the maximum sensitivity should be at light with a wavelength of about 555 nanometers; it could have been 535 nm, it could have been 575 nm, with no significant loss of functionality. There is nothing in nature which says that trichromatic color vision is best. There is nothing in nature which says that infrared begins at 700 nanometers; in fact, it does not begin at 700 nanometers, but at about 690 to 700 nanometers, because the boundary between visible deep red and invisible infrared varies a little between individuals, and even in the same individual at different times.

  • "The ability to distinguish similar colors such as separating blue from green and in-between variations like cyan and turquoise."

    It is unclear what the question is asking here. At first sight, the question seems to assume that color is an inherent property of an object. It is not. The color of an object depends upon the illuminant, and objects which appear to be of the same color under one illuminant may suddenly acquire different colors under another illuminant, while objects which under one illuminant appear of different colors may well appear of the same color under a different illuminant. This is why better LED lamps, for example, take pains to boast how well color is reproduced under their light compared to the light of the sun. This is also why savvy buyers will always want to see the color of a piece of clothing, or a piece of cloth, in natural light, and won't be satisfied with its appearance in the artificial light of the shop.

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  • $\begingroup$ 1) It's not just carnivores that are dichromates, but herbivores too. 2) The different color perceptions under different illuminants is why many people disliked CFLs and daylight LED bulbs, They'd gotten used to the much lower color temperature of incandescent bulbs, and - since they apparently didn't get outside enough - came to think that was "natural". So now you can buy LED bulbs that replicate the spectrum of incandescent bulbs. $\endgroup$ – jamesqf Nov 10 '19 at 18:49
  • $\begingroup$ @jamesqf: I know that herbivores are dichromats too, but I couldn't think of a herbivore pet... The bad color reproduction of LED lamps was due to the way they emit light -- their spectrum is not continuous, but it is usually made of distincting lines. Even the best LED lamps rarely have a color rendering index over 95. $\endgroup$ – AlexP Nov 10 '19 at 22:04
  • $\begingroup$ @AlexP The reason I asked about distinguishing colors, was because I read an article once that indicated a certain African tribe had around 20 variations of Green that looked indistinguishable to most Europeans, but no concept of blue. Likewise I have found out from some exchange students that in many east asian countries, blue and green are considered incredibly similar. One region, whose name I can't remember, even uses the same name for the two colors except distinguished as 'of the forest' and 'of the sea'. $\endgroup$ – TitaniumTurtle Nov 13 '19 at 4:47
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    $\begingroup$ @TitaniumTurtle: Being able to distinguish two colors and having names for them are two very different things. As far as we know, all people have about the same color disrimination ability, women more so than men. The set of names of colors varies quite a lot among languages; for well-known example, while English has a word for "blue" in general, in Russian one must choose between siniy for dark blue and "goluboy* for light blue, which creates interesting problems for translators. (Your example refers to the Japanese language.) $\endgroup$ – AlexP Nov 13 '19 at 7:26
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No difference. Evolution does notwork on such short timescales. Jews have been cutting off their foreskins for thousands of years yet each new generation gets born with them again. Unless an extremely specific mutation randomly appears in the population, AND that mutation conveys a large benefit to the chances of breeding, AND the breeding successfully carries the mutation to the offspring.. unless all those things happen the colonists will still be born with the same old Earth eyes like they have done for millions of years.

Your colony is too small, and the benefit of a mutation too low to make a difference. Evolution takes extremely long times, and by now it's driven more by exogenetic activity such as your ability to function well in society and civilization. These provide greater impacts on breeding traits and your desirability as a mate than say, being a bit more sensitive to red light than the next guy.

The only possible impact on our vision which I can think of, is in the development of the brain and eye in very young children. Children who are not exposed to the proper visual stimulation very early in their development can have problems developing this later in life. The required parts of the brain for processing the visual input need to be stimulated into developing early. There is a chance your colonists might have issues where if the children are only exposed, or greatly exposed to the red light when they are very young, that they never properly develop the ability to see some other parts of the visual spectrum. This is not genetic, each new pair of eyes will be physically the same as earth eyes. But it's a possible developmental problem for each individual, and after many generations, maybe they aren't even aware of it anymore.

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The concept of "visible light" is actually way broader than the human vision. It relates also to the photosyntesis, to the transparency of the atmosphere and to chemistry in general.

The lower-energy (red) limit is the ability to invoke a chemical reaction in a substance that is generally stable at the temperatures of liquid water. A substance that is less stable is less useful in biology anyway.

The higher-energy (violet) limit is the ability to invoke a chemical reacion not only in a substance specifically sensitive to it, but to almost any substance irradiated by it. That's why UV is ionizing radiation - it simply tears apart whatever chemical bond it hits. That's also why air is not very transparent to it.

It is an useful coincidence that our Sun has a maximum emission in the middle of these limits. A redder star would not create the chemical diversity in the ocean so no life is likely to appear, a bluer star would readilly sterilize any life that tries to evolve.

Human retina is actually sensitive to a bit broader spectrum than we are used to, esp. in the violet end. It is actually the lens that limits the sensitivity there and people with old-ish artifical eye lens can see all the way to, say, 200nm (not to be recommended, because UV is damaging to almost every tissue including retina).

So what is left as a possible human evolution is to move the limits between the colors in the direction of the most light available. But not by much. A blu-ish light may make "Deuteranopia" (shifted red/green boundary) less of a concern or even an advance. A red-ish light may give an advance to those w/ shifted boundary between blue and green. A generally weaker light may make a color blindness less of a concern, but that's probably an extreme case.

Anyway, the modern displays are engineered in a way to make people less color-blind (using a narrow "consensus" spectral bands in red, green and blue colors). So probably no chance of creating a completely unreadable color scheme.

(Then again, I had to deal once with an important secretary. She was partially color-blind, unaware of the very fact and repeatedly failed to recognize some differently colored lines of text in a software product we created. She didn't play fool - she later went to a doctor and had my findings confirmed. Not that she couldn't read them, she just didn't discriminate between the blue and the green lines. We ended up changing one of the colors to the gross disappointment of almost all other users.)

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Perhaps not exactly the answer that you were looking for, but color is super weird and interesting and based on perception. The visual light spectrum is specific, colors have number identifiers, etc. BUT perception is where it gets really interesting to me. There are studies that show that cultures with more words for colors, are able to distinguish more colors. For example if a culture has 20+ different words for shades of green, they will be able to distinguish between shades of green that another group of people thought were all the same color. SO while I can't quite attest to how three suns would change how you see color, it would be reasonable I think to assume that over several generations in space/not earth the exposure to a wide spectrum of colors may be less, resulting in certain words for colors not being known anymore and future generations not being able to distinguish "new" colors from the ones they already have words for. Not really an answer to the sun bit..but I think its important to note that the visible light spectrum(what we can see) is not the same as the perception of color(what we think we see)

https://www.businessinsider.com/language-can-affect-how-we-see-colour-heres-how-science-2017-10

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