Gliese 581g - A Tidally Locked DnD World

[Dannyalcatraz]

One thing you can do to muck about with the light/dark thing is make the local neighborhood a bit more complex. Think of Isaac Asimov's Nightfall- a planet in a Multi-star system in which night only comes every 1000 years (for entirely astronomical reasons).

IOW, not only could other bodies cause eclipses that bring darkness to lightside, but also, they could bring occasional illumination to the darkside.

And I'm not just talking about stars- a largish moon with a high albedo could turn a deep, dark night into the equivalent of a stormy day. A powerful aurora effect could make nights spectacular...and relatively bright.

 

[S'mon]

For a planet like Earth that's 70% water the light side may be lush, wet, tropical, teeming with life. It won't be a burned-up desert unless the whole planet is uninhabitably dry - which could very well happen as the evaporated water from the light side falls as snow on the dark side, eventually there'll be none left on the light side and you get a planet that is half desert, half snowball.

In fact I'm not sure what could prevent that process, unless most of the dark side can be raised above freezing at least occasionally. The twilight zone would simply end up as temperate desert.

 

[jonesy]

"This magical world isn't realistic."


How about a big huge system of rivers that travels from the hotter side and brings warmth to the other side. Or even an Amazon-like system on the hot which then turns into an underground system on the cold. Then you could have hot springs and oasis smack in the middle of winter. Now just got to figure out where it comes from and how it gets back.

 

[Bluenose]

For a planet like Earth that's 70% water the light side may be lush, wet, tropical, teeming with life. It won't be a burned-up desert unless the whole planet is uninhabitably dry - which could very well happen as the evaporated water from the light side falls as snow on the dark side, eventually there'll be none left on the light side and you get a planet that is half desert, half snowball.

In fact I'm not sure what could prevent that process, unless most of the dark side can be raised above freezing at least occasionally. The twilight zone would simply end up as temperate desert.

Atmospheric circulation should do some of that. I'd think, if it was 70% water, that a world relatively close to its star would have very strong tidal effects. Theoretically, snow on the 'darkside' would mostly fall close to the habitable zone. It could then be 'recycled' by tidal effects and/or melting glaciers. Most rivers would be cold, and running from the dark side towards the light side. While I don't think it's possible to work it out mathematically without more information about the planet, it also doesn't seem impossible for a world with a higher percentage of water coverage to have liquid water even at the dark pole.

 

[S'mon]

If it's tidally locked then there won't be tidal effects from the star, though.

The water would have to precipitate as liquid in the twilight zone, maybe into a twilight sea that was linked to the day-side ocean. Rivers need gravity so I don't see them being a reliable source of replenishment.

Edit: I suspect that IRL there are good reasons why M-type stars aren't a good source of planets with rich, complex ecosystems, or else the galaxy would be teeming with complex life and probably lots of intelligent life. The deletirious effects of tidal locking may be one of those reasons.

 

[Man in the Funny Hat]

If it's tidally locked then there won't be tidal effects from the star, though.

Add a large moon and/or magic.

The water would have to precipitate as liquid in the twilight zone, maybe into a twilight sea that was linked to the day-side ocean. Rivers need gravity so I don't see them being a reliable source of replenishment.

Actually, I was thinking that the planet could still be similar to earth with 75% of its surface as ocean - but with the vast majority of that on the "light" side. As you travel to the dark side the land rises. With the heat and convection there's a lot of moisture lifted into the atmosphere to travel towards the dark side - but it would precipitate not at the center of the dark side as snow, but in the habitable band between the sides where the land rises so you could have a lot of temperate rainforest and massive rivers flowing lightside.

Heading further darkside you get glaciers, a lot of snow, mountains. Once you get to, say, 60-70 degrees lattitude it becomes barren, cold wasteland.

Really, because it's a fantasy world and not a SF project you can postulate all kinds of effects and terrain that grab your fancy.

 

[I'm A Banana]

Well, if the flying creatures can go very high, migrating might be easy - low-altitude winds help carry you sunward, high-altitude winds carrying them darkward.

So maybe not big things like birds, but small things like insects (and pixies!).

Of course, there'd need to be something in the cold half to be appealing enough to ever travel there. Without sunlight, there's not gonna be a whole lot of life, but maybe it could be like the North Pole, where tidal action brings life that flowers on the light side into the darkside gradually, feeding great behemoths there. Only instead of tidal action, you've got wind action: insects hatching in the warm light side go high enough to avoid predators, mate, and lay their eggs up high in the winds, relying on gravity to draw those eggs down to the lower wind layer, to cycle them back to the light side where they can hatch. The adults, though, manage to get devoured hulking white constantly-flying balloon-whales. Mostly mouths, they gulp great clouds of small life, sustaining themselves on it like baleen whales.

If the dark half is volcanically active, it could sustain some permanent life, even close to the "antipode." Even though Antartica is so far away from sunlight much of the time, the real killer there is rock + ice = basically lifeless (aside from moss, lichen, extremophiles, whatever). If you've got a few active volcanoes breaking that up, or a more open ocean like the North Pole, the odds for life go up nicely: the ocean can breed large quantities of fish and larger life (even migratory life that is born on the light side, but feeds on the dark side), and the volcanoes create lakes and melt icecaps and provide heat. Less Antartica, more Greenland.

Maybe in a D&D-style place you have the "light side" as the above-ground critters, and the "dark side" as the Underdark. Dwarves and drow and beholders and whatnot over in the shadow, Terrasques and T-rexes and Assassin Vines and whatnot in the light.

 

[Merkuri]

Hmm... anybody think about how the light side could be like the feywild and the dark side could be like the shadowfell?

 

[Goblyn]

Y'knw, I betcha that if one were a lich who wanted to be left alone do to one's studies, a great place to build a fortress would be the dark pole of the planet.

 

[jonesy]

Y'knw, I betcha that if one were a lich who wanted to be left alone do to one's studies, a great place to build a fortress would be the dark pole of the planet.

I'm starting to think that the dark pole is pretty prime real estate and only the biggest baddest* creature, being, or faction would have the muscle to own it.

*or maybe, just to subvert the dark is evil cliche, the most good.


Another idea for the dark side: a paradise forest somehow thriving and glimmering from neon plantlife in the deep night in the middle of a frozen desert.