Tidally locked campaign world

[Haltherrion]

Temperature differences in the twilight realms would vary more from weather systems. For instance, I'm looking at the "homeland" of the elves being warmer than the fjords of the dwarves due to the elves having their islands in a shallow sea (catches and retains heat).

On the weather, having static hot and static cold regions would likely lead to some circulation cells transporting hot and cold across the faces of the world and since air movement is chaotic and extreme hot/cold make for lots of turbulence, you could also have some world class storms, maybe even some standing storms like Jupiters Red Spot. Just a thought.

Very cool world concept

 

[Umbran]

I was thinking about having seasons through the power of an eliptical orbit, but may be an extra complication that I don't want to deal with.

Well, give that the PCs are apt to never actually know much about the details of the orbit, it is hardly a complication. It might be the easiest way to get seasons, if you really want them.

It is techtonically active, partially from the strain of tidal forces...maybe the core still rotates while the surface is tidally lock. That could make for some interesting (and cataclysmic) plate tectonics.

Interjecting real-world science: Note that for a fantasy world you can always toss real science aside.

Having the core and surface rotating at dramatically different rates would create some pretty massive friction - while that would drive some pretty stellar tectonics, but it wouldn't last long. That same friction will slow the whole thing down very quickly.

Plus, the gravitational effects that produce tidal locking don't just touch the surface. Gravity reaches inside the planet too - so you'd have a hard time justifying the situation.

Radioactive decay in the core, and some friction/flexing heating from a large moon are enough to keep a planet tectonically active for billions of years. You don't need to go to areas that are hard to justify.

Then there is the aurora...have the magnetic poles = light/darkside poles

For real planets, magnetic fields are formed by a dynamo effect of liquids flowing in the interior. For short times the dynamo could have an axis in just about any direction, for reasons already stated above, the dynamo is going to (mostly) share an axis with the planet's rotation. Having it 90 degrees off wouldn't be a stable state (usign current models, anyway) and would work strongly against your tidally locked scenario. The moving fluid would drag on the crust, causing it to rotate in a new direction.

 

[Nerfwright]

Interjecting real-world science: Note that for a fantasy world you can always toss real science aside.

Having the core and surface rotating at dramatically different rates would create some pretty massive friction - while that would drive some pretty stellar tectonics, but it wouldn't last long. That same friction will slow the whole thing down very quickly.

Plus, the gravitational effects that produce tidal locking don't just touch the surface. Gravity reaches inside the planet too - so you'd have a hard time justifying the situation.

Radioactive decay in the core, and some friction/flexing heating from a large moon are enough to keep a planet tectonically active for billions of years. You don't need to go to areas that are hard to justify.

For real planets, magnetic fields are formed by a dynamo effect of liquids flowing in the interior. For short times the dynamo could have an axis in just about any direction, for reasons already stated above, the dynamo is going to (mostly) share an axis with the planet's rotation. Having it 90 degrees off wouldn't be a stable state (usign current models, anyway) and would work strongly against your tidally locked scenario. The moving fluid would drag on the crust, causing it to rotate in a new direction.

I like all of Umbran's detail here, it provides nice elements for a post-cataclysmic world scenario.

A great power unleashed some terrible event (war, planar interference, big bad magical accident) which locked one face of the planet to the sun, wrecking much of the surface world's, um, surface. Civilizations and terrestrial features like continents and oceans etc did not fare well.

A few thousand years pass. Environments and shattered civilizations adapt and stabilize. Much of the old world is hidden under entirely new orders that have evolved under the tidal stasis. Now the interface between the world's juicy and still-quickly-spinning center and the outer crust is starting to 'gel' a bit more, causing the aforementioned drag to noticeably pull the crust out of lock.

Great portents of change are everywhere; wild aurorae, mad prophets, concerned astronomers, hints of returning seasons, changes in weather, OH THE GODS - IS THE SUN REALLY MOVING?!

What do the characters do next?

I like this!