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So I'm making a world where one polar half of the planet is purple and the other is blue (in the middle it mixed, like purple/blue).

I've done a lot of research on sky color and found that purple was one color that's the hardest to be a sky color (because the sunlight spectrum doesn't have purple). But what I found was if my sky is blue but the atmosphere has large dust-like particles that are the right size to reflect red light so when it mixes with the blue sky makes purple.

My question is what particles would be the right size to reflect red from sunlight? The needed size of the dust would be enough, then I can make up some mineral to be the dust, I just need the right size that reflects red light from the sunlight spectrum.

Cause only the half of planet is purple I was thinking of making that polar half have a lot more dust , caused maybe by volcanos and the volcanos put out purple-reddish ash that would be in air and settle on the ground too.

Thanks. My Planet (doesn't have land yet)

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marked as duplicate by Josh King, sphennings, MozerShmozer, user25818, Cort Ammon Aug 31 '17 at 18:48

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    $\begingroup$ Not sure of it will work, but maybe make the sun a red dwarf could help with the scattering of the red color over the atmosphere. $\endgroup$ – Tridam Aug 31 '17 at 15:16
  • $\begingroup$ Would making your native race red-green color blind works for you? Seems it is the simplest one if you can tweak with that $\endgroup$ – Vylix Aug 31 '17 at 15:47
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Smoke and sulfur (as in, volcanoes) is historically good. You'd also be wrecking that hemisphere's agriculture, though... not that it wouldn't happen anyway; whatever shifts the sunlight that way also makes it less useful for ordinary white- and yellow-light plants.

A sky like this

purple skies

can be obtained with Earth's Sun light and approximately three times the Earth atmospheric depth, so you'd need a mechanism to get that. An oblate planet with a massive twin in tidal lock, perhaps (even if probably long-term unstable)?

On the other hand, this situation would naturally occur all the time at the Poles if the planet's tilt was exactly zero. Both poles would be in a perpetual sunrise/sunset situation, with most of the sky purple, half the horizon red, the other half night-black.

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