4

I think that it could be possible with a red sun, and either massive oceans containing algae or a surface covered with active volcanoes. What would my atmosphere be made of, and what color would those oceans/volcanoes appear?

Although humans don't need to exist on this planet, they could theoretically discover it and explore.

Edit: I know that there is a lot more to color than what the atmosphere is made of. I was wondering more what sort of atmosphere would support either the ocean or volcano theory.

Jess OhYess
  • 41
  • 5
  • I'm looking to get purple, not turquoise, although I did find some of that information useful. – Jess OhYess Feb 18 '19 at 22:16
  • Sure Jess OhYess, I hit a dilemma about the question - it's unique. If you look here: https://en.wikipedia.org/wiki/List_of_colors:_N%E2%80%93Z There are 9 different purples and here: https://en.wikipedia.org/wiki/Color_vision#In_other_animal_species If you look at just the trichromacy section, there are 10 billion colours we can percieve. We need to draw the line about duplicate questions somewhere. – Escaped dental patient. Feb 18 '19 at 23:45
  • 1
    This would make a good meta question. I'm going to vote to keep open for now but I'd like to hear more about what the community thinks about the duplicate issue. – Cyn Feb 18 '19 at 23:47
  • Atmospheres are a little more complex than just simple color of the elements, but iodine vapor has a pretty purplish color, it might be what you're looking for. – Rafael Feb 19 '19 at 00:15
  • @Agrajag that is a fair point, but if you look at the 3 different options for turquoise in that chart, not one of them even slightly resembles any of the 9 different purples. – Jess OhYess Feb 19 '19 at 00:53
  • 2
    Jess OhYess. Without question I'm no expert on colour, but the point is, if we were to entertain all ten billion possible versions of the question which represent a minute variation in colour sense we'd enter a realm of possible allowable questions that would be phillosophicaly acceptable, but totally impractical to host on the servers. SE.'s model: "While every question deserves a chance to be answered, at some point the annoyance to those searching for a solution outweighs the increasingly-small chance that an answer will be provided." – Escaped dental patient. Feb 19 '19 at 01:11
  • @Agrajag your reasoning for closing this question is deplorable and your justification for assuming the two questions are duplicates is flawed. Earth's skies are actually violet, but we see blue, which makes the other question irrelevant. – JBH Feb 19 '19 at 15:35
  • 1
    And @renan... did you know your vote would carry the weight of a moderator's hammer? I want to hear your justification for the duplication, too. We could probably use a meta question with a community wiki answer that wraps all the "what color is my sky?" questions up for easy access by new users, but that lack isn't enough to rationalize this action. – JBH Feb 19 '19 at 15:37
  • @JBH I wasn't aware of that I'd done anything other than consider the evidence before me. Without specifically researching the parameters of the question to an extent that would not be practical to do with every question from the review queue. If the skies are violet then doesn't that make an off topic nonsense of the question anyhow, since human senses are by the example in your comment subjective - I should have voted to close as opinion based instead, the outcome would remain as is, your comment could aptly be directed at the OP to edit the question to make it objective, which it isn't. – Escaped dental patient. Feb 19 '19 at 15:51
  • @JBH Appear to whom? Trichromacy, tetrochromacy blue green colour blindness and of course that old chestnut "does the colour red look the same to you as it does to me?" Then, at what time of day - colour sensitivity to differing colours different at different luminosities. Much to resolve before the question fits the "objectivley answerable" criterion. – Escaped dental patient. Feb 19 '19 at 15:58
  • @Agrajag, we'd enter a realm of possible allowable questions that would be phillosophicaly acceptable, but totally impractical to host on the servers. You don't have enough experience on any Stack to make that statement. You should be asking if your perspective is correct on Meta before ever spouting policy that isn't reflected by the community. Your criteria (not SE's or this Stack's) doesn't even meet SE's Good Subjective, Bad Subjective definition, much less our own more complex version to accommodate imagination. – JBH Feb 19 '19 at 16:06
  • Philosophically, I concur with Agrajag: the question being, how fine a gradient is too fine? I'm trying to create a planet with a colour of 33E6FF / 30E3FB / 34E4FC / 35E5FD / 30E1F9 / you get the point. Ultimately, all these sky colour questions boil down to one typological question. I can't speak for Renan, but I think this is probably the rationale. As with the Anatomically Correct series, I think a series of similarly formatted sky colour questions could be done up en suite. – elemtilas Feb 19 '19 at 17:05
  • @JBH "There is virtually nothing I can learn from a short, static list of grocery items that make up a recipe. Instead, tell me what happened the last time you made cookies from that recipe!" The link leads to no definitions. A bunch of metaphores holding together a loose narrative which invited sharing of subjective experience. - Let me meet the people who've actually created a planet, we'll chat and get back to you. Meantime, back of the envelope calculations - ten billion possible answers to the issue at hand - with images - tens of petabytes - who will pay for that? – Escaped dental patient. Feb 19 '19 at 21:36
  • @JBH You are quite right in that I have insufficient experience to make that statement - "definitivley". I spout policy which I'm able to quote, if it's not policy it shouldn't be there to be spoutable. Stack Overflow's (Not SE's as you assert, unless there's difference without discrimination) apparent requirement that one should be experienced in actually building worlds - in a literal sense is the most bizzare and absurd assertion I've ever encountered anyone making, I think I'll retire and have surreal dreams on that one. – Escaped dental patient. Feb 19 '19 at 21:53
  • This was marked a duplicate of the wrong question. It should have been marked a duplicate of What would make a sky appear purple during the day?. – JBH Nov 09 '20 at 00:30

1 Answers1

2

This situation is actually really messy

From this accepted answer from a question at Physics.SE we read:

If shorter wavelengths are scattered most strongly, then there is a puzzle as to why the sky does not appear violet, the colour with the shortest visible wavelength. The spectrum of light emission from the sun is not constant at all wavelengths, and additionally is absorbed by the high atmosphere, so there is less violet in the light. Our eyes are also less sensitive to violet. That's part of the answer; yet a rainbow shows that there remains a significant amount of visible light coloured indigo and violet beyond the blue. The rest of the answer to this puzzle lies in the way our vision works.

and the answer goes on to explain that issue.

Therefore, a big part of your problem is from whose perspective is the atmosphere purple? Keep in mind that from space you don't see a blue atmosphere. You see blue oceans due to light scattering and reflecting in the water.

It's your story, so ultimately the perspective is that of your readers. Your readers are human. So the atmosphere is purple from the perspective of humans. Except that we really stink at seeing purple in an atmosphere that we can breathe, which means you're only asking this from the perspective of humans in space suits where the faceplate doesn't get in the way of seeing purple light. And whatever is causing the purple must be whomping powerful because we're not designed to see it in the first place (rainbows notwithstanding, go read the entirety of that Physics.SE answer).

The next problem is that atmospheric color has almost nothing to do with star color. We have a really good question on this site about exoplanet sky colors with breathable atmospheres (Terrestrial Exoplanet Skies – I've Built a Visual Sky Chart. Is it Correct?) and what that question demonstrates is that with the exception of clouds and twilight, you'd still see a blue sky even with a red star. This makes sense when you remember that sky color is due to Rayleigh Scattering of the predominant chemicals (in our case, oxygen and nitrogen). This means that you'd need an atmosphere that naturally scattered the purple spectrum and not anything else because we really stink at seeing the purple spectrum.

User Rafael is correct that Iodine would be a good candidate. Remember, it must be the predominant chemical in the atmosphere. If significant amounts of either oxygen or nitrogen exist, we'll see blue because that's how we're designed. And if there's enough iodine in the atmosphere to do that, it would probably eat through the seals of your space suit.

As for what volcanoes and oceans would look like? Well, lava would look red and oceans (assuming they're full of water) would look blue. Atmosphere has nothing to do with what either looks like. Rayleigh Scattering is not a lens that we peer through.

Conclusion

Rafael's comment (which should have been an answer) is correct that Iodine will solve your problem: kinda. No human will ever breathe the atmosphere, and it would only look purple to humans and might not to any other creature — but there you are.

JBH
  • 122,212
  • 23
  • 211
  • 522
  • 1
    that is extraordinarily helpful. In my scenario, no human ever WOULD have to breathe on that planet. Your comment about perspective was also enlightening. Is there any way the ocean could appear red? Like if there was enough algae on the surface of the water. So then if my sky was blue... after the refracted light bounced off the 'red' ocean, the sky would then appear purple? Also, this planet does not need to support any flora or fauna. – Jess OhYess Feb 19 '19 at 01:04
  • 1
    @JessOhYess, there's no way for water to appear red. You could, as you mention, add algae or some other component - or make the fluid something other than water. However, bouncing the light to make the atmosphere purple doesn't work. You're thinking that light can be mixed like paint to get different colors. That's not how light works. The color you see is the predominant refracted (scattered) wavelength. Purple is its own wavelength. Red and blue are actually at the opposite ends of the scale. So, that can't be done. – JBH Feb 19 '19 at 15:30