Tidally locked world

[Liminal Syzygy]

Anyone ever ran a campaign in a tidally-locked world?

I'm thinking of an generally earthlike world that hasn't always been tidally locked but became that way in the recent past (within the last 50 years or so).

 

[Liminal Syzygy]

Just to fill in details to give people more information to give input...

Tidal Locking- Just to define what this is, in the case of the planet, it means the planet's day is one year. Thus, the same face of the planet would be towards the sun forever. The moon is tidally locked to the earth, which is why the same face is always turned towards the earth.

So generally, if a planet was tidally locked, the only portions of the planet that would continue to be temperate and suitable to human life would be the twilight zones, where you are getting some but not too much sunlight. And the sun generally wouldn't change it's position, over a year it might back and forth due to seasonal variations resulting from the tilt of the planet's axis, but it wouldn't vary it's height above the horizon.

I've seen on the Web that if earth was tidally locked the average temperature right under the sun would be 61 degrees centigrade. Not sure about the far/dark side but it would be well under freezing. I've tried to find some information on how wide the habitable zone would be but not much success yet.

What caused the planet to become tidally locked? Admittedly a cliche answer that I haven't thought through much yet, but I'm thinking some kind of magical disaster. The ultimate goal of the heroes of the world being to return the planet to it's regular rotation.

What would be the result of tidal locking on an earth-like planet? It seems the theory used to be that all the water would eventually end up in glaicers on the dark side, but that has lost a bit of support recently due to some new models.

The main thing I'm trying to figure out going forward brainstorming about this campaign world is what would be some of the weather patterns and other phenomena a recently tidally locked world might see? And what would be the impact of this on the typical D&D fantasy milieu?

Just totally going forward on my own amatuer knowledge, I would guess it would be quite likely that super-hurricanes would build up in the hot side of the planet (due to the high temperature of the oceans), at times spinning off to create massive destruction on the habitable rims. This and other factors might make Druids (with their weather control powers) the last line of defense for civilization, so to speak.

I could see where the Dwarves might retreat underground, burrowing deeply towards the warm mantle to harness energy sources there.

With the destruction of most of the world's forests, elves might also withdraw, becoming violently reactionary in protecting the few remaining forested areas.

 

[Desdichado]

That's an interesting idea. I think your assumptions are all right as far as I know. The superheating on the sunward side would create massive windpatterns -- maybe not hurricanes but very strong prevailing winds that would blow from the hot side of the planet to the cold side.

You might want to look for some models on what the tempurature would actually be. It's entirely possible that some fairly unconventional life forms could survive and even thrive on both the hot and cold sides of the planet. In fact, the cold side could potentially be a combination of arctic conditions with the Underdark. Maybe the hot side has a colony of efreet.

 

[fusangite]

I haven't run such a world myself but I have a friend who has.

My one piece of advice: what you are doing makes it way more important to hash out from the outset how your physics actually works. If you are applying modern physics to D&D, there are implications far beyond how the planet's ecology works. For example, are there planes? Is there a scientific explanation for magic? If evil is objective and detectable, how does this fit into your physics? etc.

I might recommend that rather than deciding your world is tidally locked, you decide how you want your world's ecology and physics to be and then construct a system which explains it that might or might not involve your world orbiting a star.

 

[Liminal Syzygy]

Good points. On one hand I think it would be solvable by hand-waving or the world building device of acting like it's a terribly important secret that the players don't know, when actually I just haven't worked it out yet. Arguably all campaign worlds in which the sun rises and sets, waxing and waning moons orbit the planet, etc. also apply modern physics. Granted they don't take as much center stage as in the tidally locked world - which forces the players to think about it.

For this particular world, I was thinking of possibly de-emphasizing the planes and making travel between worlds in the prime material more central. I had already started to think about the outer planes and whether or not elemental planes would exist, etc. etc. But the need to address the objective evil basic building block of the system hadn't struck me yet.

Any insights on how your friend addressed this?

 

[TheAuldGrump]

Biggest problem: No atmosphere to speak of. Gasses boil off and are not replaced on the hot side. On the cold side they are solids, slowly sublimating.. Despite the hopes of science fiction writers of a bygone era there is no temperate zone.

The Auld Grump

 

[Hand of Evil]

Read ShadowJack by Zelazany, the world was tidal locked, one side ruled by reason and technology, the other rulled by passion and magic. The twightlight zone was where they met. The book did not go too much into the world but interesting concept.

 

[Liminal Syzygy]

Biggest problem: No atmosphere to speak of. Gasses boil off and are not replaced on the hot side. On the cold side they are solids, slowly sublimating.. Despite the hopes of science fiction writers of a bygone era there is no temperate zone.

What would be the timeline for this happening on an earthlike world that was suddenly locked? Can you give me any sources or is this based on your own research and/or knowledge?

 

[TheAuldGrump]

What would be the timeline for this happening on an earthlike world that was suddenly locked? Can you give me any sources or is this based on your own research and/or knowledge?

It is based on an article from Analog magazine in the 1980s. Similar articles have been published in Science and Astronomy back in the 70s. If the tide locked world is far enough away to not have it's atmosphere boil off you are likely far enough away to have a choice between cold and colder, not hot and cold.

And in honesty I should have said a breathable atmosphere, a very thick atmosphere helps distribute temperature through convection currents. However a planet big enough to hold on to it's atmosphere with gravity is likely to be a gas giant. (And then unless the inevitable moons are geosynchronous the tides involved will cause the core to begin spinning. So, not very likely I'm afraid.)

Tide locked worlds may also be a lot rarer than was assumed in the way back - even Mercury is now known to have spin. Three major gravity wells are involved, The planet, the moon, and the stellar primary.Each affects the planet, trying to lock it in place so to speak. In the case of a major moon the effect of the moon is actually greater than that of the stellar primary.

Several articles are also available on the effects of a moon upon the atmosphere, try going through back issues of Astronomy magazine. A large moon like that of the Earth's reduces the atmosphere, making it more likely to be breathable by human like life, it will also impart spin unless it is geosynchronus.

An inhabited body tidelocked to a warm gas giant might have a better chance - but still not likely to upport Terran life.

Having a planet that is tidelocked with its moon is probably the best choice for Terran style life. And again, unless the moon is geosynchronus the tides involved will impart spin.This is actually very likely, with the exception of Pluto all the moons are tidelocked with their primaries. In the case of Pluto both planet and satelite are locked. Over time this does happen, and for that matter Earth is slowly becoming tidelocked with the moon - eventually it will happen. This will actually prevent such from happening with Earth and the Sun, so a planet locked with it's primary cannot have a major moon...

Stopping the spin of the core suddenly would take an event large enough to crack the planet open. A fun article on the movie The Core goes into this a bit. http://www.badastronomy.com/bad/movies/thecore_review.html
stopping the whole planet is orders of magnitude more difficult.

A look through the sites in my bookmarks turn up: http://www.nocturne.org/world/archives/9811/0218.html
http://www.world-builders.org/lessons/sci/scia.html
http://www.dangermouse.net/gurps/science/temps.html (Hey look, a GURPS site... I didn't think I had any of those...)

A google will likely turn up more, there are a lot of good worldbuilding sites out there.

The Auld Grump, Larry Niven also wrote a science fiction story about a tide locked Earth...

 

[La Bete]

the TORG rulebook/worldbook had a section in it about an Earth that had its spin slowed and then stopped - including the temperatures over the course of serveral months after tidelocking.