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Yora
2017-06-10, 09:22 AM
I made a quick simulation of replacing the moon with a small gas planet and one of the things that came out is the possibility of 16 eclipses per year, with total ones lasting up to 30 minutes. In practice it's probably more like 8 or fewer eclipses per year, both total and partial, and only half of them would be seen from any one place on the planet. But still, one to three total eclipses every year and lasting 15 to 25 minutes would still be quite dramatic. I think this is something that totally would have to come up in adventurs now and then.

Any fun idea how it could impact gameplay during campaigns? I don't have anything specific in mind yet, so I am really open to anything.

bulbaquil
2017-06-10, 10:55 AM
My own campaign world has four moons, two of which are large enough to totally eclipse the sun, so I've done some thinking along these lines.

Eclipses would be more commonplace, and any given point in the world would see more of them, but I think they'd still be good timing markers for occult rituals and things like that. In traditional astrology, eclipses are seen as bad omens - them occurring more frequently might lessen the effect, but they'd probably still be viewed as periods of bad luck. (We have a full moon every four weeks, after all, and that hasn't stopped the full moon from having symbolic meaning - e.g. werewolves). Alternatively or in addition, they might be used as calendrical markers or for religious rites.

Think about the declination of your "moon" - the reason we don't have eclipses every month is that the moon is slightly inclined relative to the sun, so we only have an eclipse when the moon is new/full at the same time as it matches the height. If the moon's orbit around Earth were coplanar to Earth's around the sun, every new moon would be a solar eclipse, and every full moon a lunar eclipse.

Yora
2017-06-10, 11:00 AM
Yeah, that's why I went down to 1 or 2 from the 8 you would get with flat orbits.

My setting has a pretty major element about transitions between the material world and the spiritworld. Total eclipses would seem like a great opportunity for having a unique transition event. Day becomes night. That should have some serious symbolic meaning for spirits.

1337 b4k4
2017-06-10, 06:33 PM
Eclipses are a time of resurrection. For as long as anyone can remember, every time an eclipse starts the dead begin to rise, the more complete, the more "powerful" the effect (partial eclipses generate a localized effect, total eclipses encompass the entire world). The longer it runs, the older a corpse can be and still be resurrected. This as been a mixed blessing to the world. Those that have died only recently, before the decay of death has taken hold can be returned to full life and health with a mere few days of rest. Older corpses, with minimal decay may experience periods of agony as they return to life with parts of themselves missing, but with adequate care, even they can be restored to health. But the longer a body has been dead, the more damage they feel and suffer upon resurrection. While minor eclipses can be cause for celebration, long total eclipses are cause for fear as long dead corpses return to life, but are instantly driven mad by the pain of being alive in such a decimated body. These are no longer the men or women they once were, they have become monsters and will kill anything or anyone in their path.

Lord Torath
2017-06-11, 02:49 PM
Eclipses are a time of resurrection. For as long as anyone can remember, every time an eclipse starts the dead begin to rise, the more complete, the more "powerful" the effect (partial eclipses generate a localized effect, total eclipses encompass the entire world). The longer it runs, the older a corpse can be and still be resurrected. This as been a mixed blessing to the world. Those that have died only recently, before the decay of death has taken hold can be returned to full life and health with a mere few days of rest. Older corpses, with minimal decay may experience periods of agony as they return to life with parts of themselves missing, but with adequate care, even they can be restored to health. But the longer a body has been dead, the more damage they feel and suffer upon resurrection. While minor eclipses can be cause for celebration, long total eclipses are cause for fear as long dead corpses return to life, but are instantly driven mad by the pain of being alive in such a decimated body. These are no longer the men or women they once were, they have become monsters and will kill anything or anyone in their path.
It strikes me that such a world might invest heavily in cremation. Any body dead more than those requiring "a few days of rest" following rising from the dead would be thoroughly burned to prevent the rise of angry souls.

Yora
2017-06-11, 03:35 PM
But I like the idea that any resurrection can only be performed during an eclipse. You not just need to have the right tools and be at an appropriate site of power, you also have only 2 or 3 opportunities per year.

Similarly, sorcerers are always putting their major summonings during eclipses, which gives players a nice fixed timetable to stop them before it's too late.

I like to pursue the idea that during an eclipse portals to the Spiritworld are opening everywhere. You better stay put until the sun returns or you might find yourself trapped on the other side with no way back for several months. (Which you almost certainly won't survive.)
At the same time spirits are going to pour into the material world. Most of them will return to their realm before the eclipse ends, but in the meantime they will be stalking the darkness.
The best policy is to light a fire, burn special herbs, and recite protective chants until it's over. Then it is pretty safe with little to worry about. If something forces you to go chasing through the darkness, things look much less promising.

Thrudd
2017-06-11, 03:52 PM
Wait - the moon replaced with a gas planet? Meaning the inhabited "planet" is actually a moon of the gas planet? Or you mean that it is a ball of gas with the same mass as the moon, orbiting an earth-like planet, held together by some sort of magic? Or this earth-like planet is way out from it's star, or not orbiting a star, so the temperature is low enough for the small gas-body to maintain form?

There must be a star at a distance similar to our sun, because we're talking about eclipses - so I'm guessing a magical body (of course, the star could be a magical body, too).

Eclipses could cause magic to stop working altogether, maybe the sun is the source of magical power. Or the sun is the source of certain magic powers, and when it is eclipsed those stop working and certain special other magic powers only work at this time - like the resurrection you talked about.

Maybe the eclipse allows the invisible world of spirits to be seen, which coexists alongside, on top of, the physical world - and for those thirty minutes people can see the spirits of the dead, or fairies, or all sorts of shadowy creatures - and also have the opportunity to gain information or travel to places within that window that is not possible otherwise.

LibraryOgre
2017-06-12, 10:52 AM
You might also see some wacky things happening with durations, or some odd effects on werecreatures. Something that has a duration of until the next eclipse shines on a person, or lycanthropes changing forms during the eclipse... so a werewolf might be stuck in wolf form for months, only able to change at the eclipse.

I also like the idea of it being a limnal time, where resurrection and such is easier/possible. Perhaps a bonus to creating undead, as well>

Lvl 2 Expert
2017-06-12, 11:00 AM
To be the nitpicker here: I don't think a gas planet slightly larger than the moon would stay intact. Venus still has its impressive atmosphere, but it is a pretty large rocky planet underneath and it does not orbit another body closely. There are at least 4 solutions:

1 Just use a rocky body.
2 A wizard did it These are not exactly our physics.
3 The solar system is still young, the gas moon, preferably with a rocky core, will dissipate eventually, but not this billion years.
4 What Thrudd said, the gas planet is larger than the body your story takes place on. That could give you some serious eclipses. (But maybe that's what you meant already.)

Lord Torath
2017-06-12, 11:23 AM
A strong magnetic field could protect the gas planet's atmosphere.

Yora
2017-06-12, 12:40 PM
In my specific case, it's not slightly larger than the moon, but twice the mass of the Earth. And the mass of the atmosphere adds to the planets overall gravity. The normal range for gas dwarves appears to be 1.7 to 4 Earth masses. These are very common in the universe, though I don't know how much at 1 AU from a sun-like star.
But these things do actually exist.

Aliquid
2017-06-12, 01:38 PM
In my specific case, it's not slightly larger than the moon, but twice the mass of the Earth. And the mass of the atmosphere adds to the planets overall gravity. The normal range for gas dwarves appears to be 1.7 to 4 Earth masses. These are very common in the universe, though I don't know how much at 1 AU from a sun-like star.
But these things do actually exist.I'm with Thrudd here... that sounds like your fantasy world is actually a moon orbiting the gas planet. Or maybe some sort of binary planet situation.

Not sure how much you want to go into the mechanics of this, but also consider the impact of this gas planet on the tides of your fantasy world. That much more gravity would make for some really big tidal action.

Yora
2017-06-12, 01:45 PM
At a mass ratio of 2:1 I'd go with a binary planet. But for the people in the terrestial planet, the gas dwarf is just like a moon in the sky. I actually worked this out in much more detail (http://spriggans-den.com/2017/06/10/thats-no-moon/), but I think it's irrelevant to the question at hand.

Thrudd
2017-06-12, 01:56 PM
In my specific case, it's not slightly larger than the moon, but twice the mass of the Earth. And the mass of the atmosphere adds to the planets overall gravity. The normal range for gas dwarves appears to be 1.7 to 4 Earth masses. These are very common in the universe, though I don't know how much at 1 AU from a sun-like star.
But these things do actually exist.

It could not exist at 1 AU from a star like our sun, not likely. The star would probably need to be a red dwarf, I think that is the sort of system where we have observed those gas dwarf planets.

So the inhabited body in your world is the moon of the gas planet - or is this a situation where two similar sized bodies are orbiting around each other? Is this meant to be an intelligent-design scenario, like super advanced civilization engineered the orbits and magnetic fields to work in equilibrium (aka magic)? Or just plain old magic - don't need any explanation at all. Spelljammer style spheres with their own local rules different from ours can work just as well.

It's a cool visual, that's for sure.

lunaticfringe
2017-06-12, 02:24 PM
Are Portals stationary or do they appear at random or both?

Is Astronomy a thing? Observing the heavens has been around for quite some time and earthlings never really had a pressing need.

I'd imagine organizations or peoples that could predict or defend against Spirit Invasions would have quite a bit of Social Capital in said world given their frequency. Stereotypical Dwarf Fortification builders would be in high demand, for example. Grey Wardens...

Can Spirits Possess bodies or interbreed with 'mortals'?

Religions are going to take this concept and run with it in all sorts of directions. The Resurrected are Evil Tainted Spirit Freaks. A cult who collects & preserves remains of heroes to Resurrect them in times of great peril. So on and so forth...

Aliquid
2017-06-12, 02:31 PM
At a mass ratio of 2:1 I'd go with a binary planet. But for the people in the terrestial planet, the gas dwarf is just like a moon in the sky. I actually worked this out in much more detail (http://spriggans-den.com/2017/06/10/thats-no-moon/), but I think it's irrelevant to the question at hand.Irrelevant as it may be... you are posting on a board frequented by curious geeks.

Yora
2017-06-12, 02:39 PM
It really is just a giant blue and beige moon, as far as people in the world are concerned. Which happens to go through all its phases every 16 days.

Portals to the Spiritworld are both fixed and variable. It's both possible to seek out a known stable portal to get to the Spiritworld, and to accidentally walk through a temporary one without noticing it at first. By the time you notice and go back the way you came, it can already be gone. So I guess an eclipse greatly increases the frequency of temporary portals that last until the sun comes back.

Since eclipses can only happen during a new moon and the setting uses a lunar calendar, it's very easy to predict the days on which an eclipse might happen, which is always the last day of the month. It would make a lot of sense that people don't go on long journeys at the end of the month to be safe that they don't end up being caught on the road or sea when it happens. Being in a settlement which is already being warded against hostile spirits all the time is much safer.
Of course, this does not apply to adventurers. :smallamused:

Lord Torath
2017-06-12, 03:17 PM
Since eclipses can only happen during a new moon and the setting uses a lunar calendar, it's very easy to predict the days on which an eclipse might happen, which is always the last day of the month. It would make a lot of sense that people don't go on long journeys at the end of the month to be safe that they don't end up being caught on the road or sea when it happens. Being in a settlement which is already being warded against hostile spirits all the time is much safer.This will tend to make exploration a slow process, and will especially curtail ocean exploration. Land explorers might be able to find semi-friendly tribes of humans/demihumans/humanoids out in the wilderness, willing to let them take shelter during the eclipse. Coasters might be able to skirt the shore, and take shelter at the appropriate time of the month. But ocean-going vessels will probably not exist. Unless there's some way to ward a ship? It's more substantial than a tent. What exactly is involved in the warding process? Could you ward the interior of the ship, and then hide there during the eclipse and the "troublesome" time period? Which also brings up the idea of Gypsies with warded wagons.

How closely does the moon's orbital period match the 16-day month? Is it exactly 16 solar days? (A solar day is the time it takes for the world to rotate from "noon" at one location to the next "noon" at the same location, which is more than 360 degrees on Earth, but could be less if your planet spins in the opposite direction it orbits its sun.) If so, then some parts of the planet will never see a solar eclipse (it will always be night in those locations when it happens), while other parts will never see a lunar eclipse (always on the day side of the planet at the time).

Also, eclipses are generally not planet-wide. OK, on Earth they are definitely not planet wide. Just a small spot from the moon's shadow traces across the Earth (https://epic.gsfc.nasa.gov/galleries/2016/solar_eclipse). Lunar eclipses are different, but are frequently only partial eclipses. What does a lunar eclipse look like in your world? Is the disc of the moon fully covered by the world's shadow? Or does the world's shadow show up as a small dot on the moon? You're moon has 8 times the apparent diameter of our moon, right? So presumably, its shadow on the world during an eclipse will also be eight times larger, which is still not large enough to cover the whole planet. Actually, looking at the DISCOVR satellite images, the partial eclipse might be planet wide, with only a small portion getting a total solar eclipse.

OK, I've rambled on enough. Hopefully I've given you some things to think about.

Yora
2017-06-13, 09:58 AM
The apparent (and actual) diameter of the gas planet is 8 times greater than the Moon. Which leads to 72 times the apparent surface. That's going to be a really big shadow being cast on the terrestial planet and in turn a lunar eclipse will probably look like a dark spot on the surface of the gas planet.

The month is not exactly 16 days, but close enough so that I don't worry about leap days. But it means that solar eclipses happen at different times of the day for any given point on the planet. This could be calculated quite exactly pretty easily, but I am happy enoug with there simply being a 50% chance of an eclipse happening at an arbitrarily chosen time of the 16th day of the month.

Lord Torath
2017-06-13, 10:57 AM
The apparent (and actual) diameter of the gas planet is 8 times greater than the Moon. Which leads to 72 times the apparent surface. That's going to be a really big shadow being cast on the terrestial planet and in turn a lunar eclipse will probably look like a dark spot on the surface of the gas planet.Should that not be 64 times the apparent surface? 82 = 64. Or is there some other mechanic at work?

Have you done the math to calculate just how big the moon's shadow on the world will be? Both the umbra and the penumbra? I presume the sun is roughly the same size and distance as ours? So the sun is about 1.4 Gm across, and 150 Gm away. The moon is 4 degrees across, and still 385 Mm away? Luna is 3.5 Mm in diameter, so your moon will be roughly 28 Mm across. Here's a website that might help: http://mathscinotes.com/2010/10/solar-eclipse-math/. I'm still working through the math myself.

Here's another interesting link: https://www.timeanddate.com/eclipse/shadows.html

Edit: I'm getting an Umbral diameter of 24,662 km, which is roughly double the diameter of the Earth (using a moon diameter of 13,904 km, which is 8 times the diameter of our moon). -> World-wide total eclipse! :smalleek:

On the other side, I'm getting an umbral diameter of 9650 km in the case of a "lunar" eclipse, compared to your moon diameter of roughly 28,000 km.

Yora
2017-06-13, 11:29 AM
Have you done the math to calculate just how big the moon's shadow on the world will be?

No. I really don't care.