Creating a dark world - How can I not completely handwave the dark cloudy atmosphere

Question

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?

Answer 1

Ring around the star.

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

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.

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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.

Answer 2

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)

Answer 3

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.

Answer 4

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.

Answer 5

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.

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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.

Answer 6

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).

Answer 7

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.

Answer 8

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.