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Primary question

What is going on with the atmosphere that the world is so gloomy and dark?

Information

I have had a low-magic fantasy world I have been wanting to solidify for a while now but previously dismissed the idea as too hand-wavey until this answer to a question popped up (the answer basically says: if you only block a lot of human visible light, plants can still live while it looks super glum).
I have looked around but didnt find something already posted that got me where I wanted. I found these ones here, here, and here about dark/hazy worlds.

Here are the criteria that I want to meet on this dark world

Criteria

  • The world is always darker than earth, but still has a visible day/night cycle (think full moon versus new moon but a bit brighter).
  • It is very cloudy and drizzly but its dimness would (likely) come from a dusty/hazy atmosphere even when it is not overcast.
  • The rain is still drinkable with minimal effort even if bitter.
  • It needs to be warm enough to rain (above freezing) at least the majority of the year if not all year. Chilly is fine, snow and ice is less fine.
  • There is still leafy plant life in addition to more mushroom-eqsue plants

Clarifying Details

I am fine with magic or some magic going into it, but I don't want the world to work entirely "because magic". If only some of the light spectrum is blocked then the world should still be dark while maintaining these characteristics and its plausibility... I think.

What can I do with the atmosphere or world that has at least some science that will mess with a normal range of vision while not having toxic rain and keeping at least slow growing leafy plants?

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    $\begingroup$ Gloomy ? Dark ? I live in Ireland - you're describing summer here. :-) $\endgroup$ – StephenG Jan 16 '18 at 16:39
  • $\begingroup$ Why not make the planet further away from the central star / the star weaker / something like that? Btw, planets are huge. How bright it gets depends on where you are on earth. It's a lot brighter in say central Africa than Northern Sweden, even during the height of the summer. A statement like it's darker than Earth doesn't make that much sense. Planets are huge and your story might only play in a very small region, so just moving it "north" or "south" might do the trick $\endgroup$ – Raditz_35 Jan 16 '18 at 16:48
  • $\begingroup$ Methinks you're stuck on the idea of Earth plants. A world with a smaller, or darker, or more distant sun, or a world with a misty atmosphere (lots of active volcanoes in the oceans) would evolve plants that would survive in that environment. $\endgroup$ – JBH Jan 16 '18 at 16:52
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    $\begingroup$ You only need certain shades red and blue light to allow plants to grow successfully. The problem is I can think of many ways to make it dark, the mega volcano, but they all cause the planet to be cold some time really cold. If you have sunlight you have heat and light, otherwise you lose both. Additional, even if the molten core keeps it warm, you need light for plants to grow. Tidally locked with a moon(s) would make one side of the planet dark, and you guest it COLD!! $\endgroup$ – cybernard Jan 17 '18 at 2:23
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    $\begingroup$ If the planet was always dark - then why wouldn't people get used to it? I don't think they would ever perceive it as being dark or murky unless they had something to compare it against... $\endgroup$ – Shadow Jan 17 '18 at 2:44
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Ring around the star.

Ring around Fomalhaut

from https://commons.wikimedia.org/wiki/File:Fomalhaut_B_entire-Hubble_Telescope.jpg

Just as a planet can have a ring around it, so can a star. If you were in the same orbital plane as the ring and it was between you and the star, it would shade you. Consider the situation of the outer shepherd planet in this schematic of the ring around the star Fomalhaut. It is shaded by the ring.

from http://www.solstation.com/stars/fomalhau.htm schematic of Fomalhaut ring

This is nice for your scenario in that

  • You can have it suddenly get darker if you like. The ring was formed by a dissolution of one of the inner planets in the system.

  • You have no constraints on the atmosphere of your own planet: the shade is cast by far away stuff. Degree of shade might vary with the density of the interposed ring, which can change as ring and planet orbit.

  • What would this look like from the perspective of the planet? I am sure there would be twinkling chunks and haze in the sky at all time.

  • You planet can have one pole protruding beyond the shade of the ring. Here one can still see the sun rise.


ADDENDUM - Ring are thin, I hear? Too thin to shade? Saturns rings are thin compared to Saturn or compared to their width, but we are talking about a ring around a star. How thick is Fomalhaut's ring?

http://www.dailygalaxy.com/my_weblog/2012/10/the-strange-planets-of-fomalhaut-a-spectacular-alien-star-system.html

The original ALMA research shows that the ring's width is about 16 times the distance from the Sun to the Earth, and is only one-seventh as thick as it is wide.

So 16 / 7 = 2.2: the ring is only as thick as double the distance from the Earth to the Sun, which is 146 million km x 2 or 292 million km. The diameter of the Earth is 12,742km. I think the Earth would be able to find shade from a ring of this size.

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    $\begingroup$ Rings are very thin. Saturn's rings are only 100 m thick at most. Given even the slightest inclination of the planet from the ring's plane, the ring won't shade anything. On a second note, reading back over the question, I feel like the OP was looking for more of an atmospheric phenomenon rather than astronomical. $\endgroup$ – kingledion Jan 16 '18 at 18:10
  • $\begingroup$ The idea of the sun rising and setting over this ring is very cool. $\endgroup$ – bendl Jan 16 '18 at 18:11
  • $\begingroup$ @kingledion I am, but this answer did open my eyes to this possibility which I quite like. It provides an answer a little outside of my scope, but it is a welcome one. Its a shame that apparently rings are very thin, because this would actually be a nice solution $\endgroup$ – BornToDoStuff Jan 16 '18 at 18:15
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    $\begingroup$ @Kingledion: re thin rings - just as my pants are much larger than yours on account of my much largerness, so too the ring of a star is greater than the ring of a planet. Addendum with refs added! $\endgroup$ – Willk Jan 16 '18 at 19:43
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    $\begingroup$ OH! That is super cool. Thanks for the reference. In the reference it seems that the planets are massively cold BUT because of the awesomeness, in the context I am thinking of I could just handwave the distance from the sun or its temperature and use a star ring to create a dark planet. $\endgroup$ – BornToDoStuff Jan 16 '18 at 20:00
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I can envision a world that matches most of what you describe, yet provides some unique opportunities for story telling.

Start with a planet with a dense, organic rich upper atmosphere, that becomes mostly transparent near the ground. This is a reasonably accurate description of the atmosphere of Saturn's moon Titan. At mid day, at ground level on Titan, the illumination is about 1000 times less than a sunny day on Earth, or about the same as 10 minutes after sunset. So it's very dim, but bright enough for a human to navigate. If an intelligent species evolved here, they would certainly develop eyes adapted to this light level.

Next, there's the issue of plant life. Consider, due to the dim illumination, there is very little plant life on the surface. However, the upper atmosphere is teaming with various photosynthetic microorganisms, akin to the phytoplankton in our oceans. They convert carbon dioxide to oxygen, thereby adding oxygen to the atmosphere. Also, when they die, they fall though the thick clouds to the ground below. There are small animals that eat this thin organic layer (of dead phytoplankton), so become the base of the food chain.

So you have a dimly lit planetary surface, with a few slow growing plants, teaming with animal life. Any intelligent life would have no idea that there was a whole universe beyond the sky. See James Blish's Surface Tension.

Info about Titan's atmosphere and illumination level: https://en.wikipedia.org/wiki/Huygens_(spacecraft)

Summary of James Blish's Surface Tension: https://en.wikipedia.org/wiki/Surface_Tension_(short_story)

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Perhaps your planet is surrounded by a thick dust field. The dust field is thick and surrounds the planet, and is approximately 5km thick.

The rain is still drinkable with minimal effort even if bitter.

The dust is just on the edge of orbit but far enough away that it wouldn't ever descend onto the planet and cause problems with the environment.

I'm not an expert but I would imagine that this would block a fair amount of light from entering the atmosphere, whilst still providing adequate enough sunlight to allow for normal life cycles to exist.

But why is there a dust field?

The space around your planet is or was a minefield, asteroids are or in the past (few thousand years perhaps) colliding with each other and the remaining fragments ricocheted off into deep space or down onto your planet (This could open up for some extra story telling, my thinking would be either an explanation for a particular species of mushroom or an event that the locals celebrate annually).

Now all that is left are small rocks and a lot of dust just orbiting the planet indefinitely.

Edit

To better answer your question, if you did want to add a little bit of magic, perhaps there is a spell/magic barrier that prevents the dust from entering the atmosphere. I feel that this would better explain why the dust is stuck orbiting the planet rather than being just on the edge of orbit, as that doesn't sound particularly scientific.

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  • $\begingroup$ I like the idea of some extra space debri crashing into the planet for more story elements, it could open up a lot of possibilities. The problem being scientific and the solution being magic actually suits me fine. I think that if I could find something saying that the dust could at least be thinner near the surface I could either make it be a dustier than anticipated story with the frequent rain washing most of it away, or use magic to deal with some of the lowest hanging dust. $\endgroup$ – BornToDoStuff Jan 16 '18 at 17:18
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    $\begingroup$ @BornToDoStuff I'm glad I at least gave you some ideas. Further thinking, maybe the barrier only protects a small part of the atmosphere rather than the whole planet. Maybe the dust does fall towards the planet but the barrier disintegrates some of the dust, this could explain it being thinner nearer the surface. Hope this helps $\endgroup$ – Lara Croft Jan 16 '18 at 17:25
  • $\begingroup$ @BornToDoStuff, plain and simple: low-orbit dust experiences more atmospheric drag and falls down quickly. $\endgroup$ – ZuOverture Jan 17 '18 at 4:58
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I'm going to suggest that the star it's orbiting is near the end of it's life, or it's just a slow burning star.

https://astronomy.stackexchange.com/questions/6210/are-there-stars-that-dont-emit-visible-light

https://www.quora.com/Why-do-stars-emit-visible-light

You might need to have a planet that's closer to the star to inhabit to get enough warmth, UV (for plants), and other considerations.

You could also have a moon that is tidally locked (or similar) to keep the planet in an eclipse state. Maybe the moon wasn't always in that position, but it orbited the planet in the correct direction and eventually slowed (or sped up) due to the gravitational force of the sun so that it is "locked" in one spot between the sun and the planet. This could be something like a Lagrange point between the Earth and the moon, or simply a spot where the speed of the moon matches the speed of the planet in it's orbit.

https://www.space.com/30302-lagrange-points.html

Another idea is that it's a hot planet that has lots of humidity, causing fog and clouds. Anyone who has been in a sufficiently foggy area knows that fog seriously reduces the amount of light available to see by, and clouds are known for their light blocking capabilities.

The "Coldfire Trilogy" by C.S. Friedman gives the impression that it is nearly constantly darker than Earth due to a combination of high humidity and maybe volcanoes. This is also a magic realm, which was colonized from Earth and stranded due to misfortunes which I won't get into as they would be spoilers (I think). It's a good series, so you should enjoy that research.

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Debris in your planets orbit or atmosphere are good ideas. Moon(s) blocking sun light most of the time.

There is a question of what level of technology exists here.

The problem here is how they got to this level of technology with no or little sunlight.

  1. Aliens who destroyed their own world and moved here.
  2. Planet existed in full daylight in the past, but now the star has dimmed significantly.
  3. Maybe the sun is just forming, and it hasn't reached full power yet, maybe its another 100k years or more till full power.

There are red and blue grow leds specifically designed to allow plants to grow. An advanced enough civilization could basically light different areas of the planet they need lighting.

You could literally light entire farm fields with leds, and one such a planet even more advanced lighting techniques might exist.

The problem is to maintain the planet in semi-warm environment, even with something blocking the sun/star.

  1. If you were close enough the heat of the sun would still reach you, but I suspect you would need to be a lot closer.
  2. Either that or rewind the planet to a time where lava was only 10's of feet below the surface of the planet. If you found the right depth of lava the surface of the planet would definitely be warm/hot and remain that way for long periods of time. Even 100,000 years is nothing in galactic terms, and your whole society could evolve and become extinct in that amount of time.

If the planet was high/low enough compared to the star only the pole of the planet would get direct light. Very careful placement could result in most of the world not getting much sunlight. However, the north/south pole depending on elevation would definitely get full or nearly full daylight.


Maybe your whole world is an alien experiment. They have erected a force field around your planet which block most of the light most of the time.

  1. Scientific experiments to see how life develops under these conditions.
  2. The aliens are just plain mean and like messing with lower civilizations.
  3. Bored and need something to do, so they bother others like Q on Star Trek.
  4. Prison planet. (all lefties go to prison per Dilbert episode) or similar.
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It could possibly be a thick atmosphere.

If it darkened over time gradually then the plant could evolve or if it was dark from the beggining then any plants still existing would have the ability to survive (natural selection).

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Ozone layer.

Make your planet to circle a neutron star, O giant or other very hot star, and the high level of UV radiation would ionize the atmosphere, making ozone and nitrogen oxides that blocks out visible light on the planet.

However, since the star radiates in primarily soft X-rays that penetrates this layer well, plant life on the surface can use this radiation for photosynthesis. Think things like melanin or other types of radiotrophic synthetic process.

Since the star make little radiation in the visible spectrum(to not boil or scorch the planet), you will have an overcast sky with the ionized ozone layer, little light from both the star and from the absorption of the atmosphere, surface plant life which don’t use visible wavelengths and all the things you can get for your requirement. Add in magnetic fields and particles that comes with the hot star you get magic-like abilities, for the human race, they just arrived off-world, therefore does not have eyes that can see the X-rays like other life on this planets can, giving a dark overcast impression.

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  • $\begingroup$ As I mentioned on one of your previous answers, you need to hit Enter twice to separate paragraphs, not just once. $\endgroup$ – F1Krazy Jun 5 '18 at 7:51
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The 'dark ages' are called the 'DARK ages' for a reason, They started with an event that, literally, put the earth into darkness. Something was blocking out the sunlight. It is hypothesized that it was a volcano that created a thick dust cloud around the earth. See The Dark Ages Were Caused By Two Enormous Volcanic Eruptions and Climatic and societal impacts of a volcanic double event at the dawn of the Middle Ages for a scholarly article.

Volcanic activity in and around the year 536 CE led to severe cold and famine, and has been speculatively linked to large-scale societal crises around the globe.

Also see They really were the Dark Ages

In London, England, the 'pea soup' fogs that blocked out the sunlight were due to particulate pollution from burning dirty coal fires.

So there are a few possibilities in your world.

I would suggest that there are huge coal or other organic or carbon deposits, that have been set on fire and have been burning for a very long time. These would produce a huge particulate smoke cloud that covered an area.

Your question does not specifically state that this has to be planet-covering, just covering 'your world'. During the Dark Ages, their 'world' was Europe. It also does not give a time frame for this effect.

A second option would be continuous dust storms. A weather pattern that produced constant high velocity upper atmosphere wind patterns. The wind energy would have to come from some extreme temperature differential. Perhaps a tidally locked planet with a thick atmosphere would produce constant convection air currents from the hot side to the cool side. Since the rotation of the planet would be very slow, there would be no or minimal Coriolis effect.

A third option would be continuous volcanic activity on the planet. An earthly example would be Two centuries of continuous volcanic eruption may have triggered the end of the ice age. Also, apparently Io has permanently active volcanoes.

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    $\begingroup$ Can you provide a citation for the idea that the Dark Ages were literally darker than at other times? That's interesting and I want to know more. $\endgroup$ – JBH Jan 16 '18 at 16:53
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    $\begingroup$ I had to do a double take here. No, the dark ages most certainly weren't called that because it was literally dark. Your article talks about possible volcanic events between 536 and 540 CE, not that the dark ages as a whole were literally dark... and not that they were named as such because of it. $\endgroup$ – Elukka Jan 16 '18 at 17:12
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    $\begingroup$ @Elukka, that insight is why I asked for more info. The phrase "Dark Ages" is historiagraphical, which is a fancy way of saying, it's a name we give the period between the decline of the roman empire and the renaissance wherein Europe experienced low intellectual productivity. However, that there was also a period of actual darkening is an interesting coincidence. $\endgroup$ – JBH Jan 16 '18 at 17:21
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    $\begingroup$ This absolutely is not why they are called the Dark Ages. The term 'Dark Ages' was coined by an Italian scholar named Francesco Petrarch. Petrarch, who lived from 1304 to 1374, used this label to describe what he perceived as a lack of quality in the Latin literature of his day. Petrarch - almost certainly - had no knowledge of any eruptions 800 years before his birth, and was describing his own time $\endgroup$ – Binary Worrier Jan 16 '18 at 17:49
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    $\begingroup$ @JustinThyme, Petrarch's phrase is clearly metaphorical. He wrote, They were great men, but placed in the depths. We are small, but placed on the heights, thanks to God. They lived in the dead of night; we live in a bright noonday... I consider that this applies not only to the two authors I have before me, but to all the pagan philosophers [...] whose mind's eyes were blocked by an impenetrable cloud from any vision of the truth. $\endgroup$ – LSerni Jan 16 '18 at 21:03

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