Wesnoth calendar

[Simons Mith]

Though, it's orbit did go eccentric at some point to produce the Long Dark.

No it didn't, the planetary rotation had a bit of a hiccup while the elves were on the night side.

[Cloud]

To bring this up again, but after a little number plugging I found 26 is a nice number of days in a lunar cycle. It completes 335 cycles every 24 years (or as near to 14 as dammit every year).

I'm currently trying to figure out an Elvish calender, though they might not care for months much, I was thinking of doing something similar to Celtic months, just with an extra tree to make it up to 14 so it can fit with the lunar cycles.

Spoiler:

Nominally working with - Birch, Rowan, Ash, Alder,Willow, Hawthorn, Oak, Holly, Apple (as the "extra" month, which won't exist every 14th and 24th year), Vine, Ivy, Reed and Elder.

Each Elvish year has 2 more days (364) than a normal solar cycle (362 11/12), except the 12th 14th and 24th which are 365, 338 and 339 days long respectively.

Even if my Lunar cycle idea is regected, I'll probably try to keep the elves with this calender, it's just their kinda thing .

[AI]

Note that you're basing this (at least partially) on statistics from earth. Irdya is similar, but probably not equal.

[Cloud]

Working on the Irdya year being 362 11/12 days long (see Simonds_Mith's post earlier in the topic). I know it's not definite, but if that is the case then it works, if not back to the drawing board with nothing lost apart from a little time.

[BGeek]

How many planets are in the Irdya system?

[Aethaeryn]

How many planets are in the Irdya system?

I don't think we should determine stuff like that (locations) until necessary. It's probably also why we don't know too much about geographical regions there are no campaigns in (south, southeast, east, northeast, and the old continent west of the Green Isle).

[solsword]

I know this thread is a bit stale, but it's clearly still in need of work...

I'd like to chip in on the whole binary star system debate. The explanation of Naia from UtBS:

./scenarios/10_Speaking_with_the_Fishes.cfg: message= _ "This will go much faster if you don't interrupt me. Now, as I was saying the Empire of Wesnoth was very learned in the magical arts and had vast repositories of knowledge. Back then there was only one sun in the sky, the sun you call Sela. But the king decreed that he would raise a second sun into the heavens, to lengthen their days and shorten the darkness. All the mages, sorcerers and wise men came together and cast a mountain into the sky and made it glow as bright as the sun. They sent this second sun, who you call Naia, hurling through the sky so that there was only a few hours of dark each night. Though some had called the attempt foolish, it was a resounding success and stood as a tribute to the power and might of the humans. The golden age glowed brighter than ever and the many believed that they had dispelled evil and darkness forever."

This quite clearly implies that the second sun is not an actual sun, but rather a glowing mountain, almost certainly orbiting close to Irdya (perhaps even closer than the moon?). Also, at that distance, it doesn't need to be nearly as bright as the sun in terms of raw energy (although the explanation for the brightness is "magic" anyways).

As to what is going on with the long dark:

message= _ "But with their prosperity and power, over the generations the humans grew arrogant. One day a young descendant of the original king decreed that darkness should be abolished altogether from the land, so that light and goodness would shine forth everywhere. But the people had grown lazy and complacent and the ranks of mages who still trained hard to harness the magical arts had decreased greatly. Still the king believed he was all-powerful and would not listen to the mages' protests. So, seeking to duplicate their ancestors' previous success, the mages tried to lift a second mountain into the sky. But a great evil befell them that day; their power failed and the mountain crashed down onto the humans capital, crushing all within it. In an instant the center of the Empire of Wesnoth was utterly destroyed."
[/message]

[message]
speaker=Melusand
message= _ "The king and his family were all killed, and soon petty warlords tore apart the empire as all the known lands fell into chaos. Elves and Dwarves were drawn into the conflicts, Orcs and Trolls spread forth from the dark places, and chaos and darkness swallowed the lands."
[/message]

[message]
speaker=Melusand
message= _ "The two suns, a monument to the power and hubris of the fallen Empire of Wesnoth, scorched the earth. The fields dried up, forests died, and swamps turned into mud-cracked plains. Since then the path of the second sun has shifted in the sky, creating the long dark that you are so familiar with every other night. And much evil has spread forth across the lands. The mages of the Empire of Wesnoth still haunt their domains as the undead lords that plague your sands. The surviving humans have descended into barbarity and squalor. Orcs cover the lands killing each other and any that fall into their grasp. The dwarves and trolls hide in their tunnels, in the dark, fighting an endless war. I do not mean to offend your friend, but the majority of them care little for the fate of the surface dwellers. And without their forests the elves have mostly died out, another victim of the chaos and evil that dominates our lands."

So the most likely scenario to my mind is that while raising the second fake sun, not only did their magic fail, but the second "sun" altered the original orbit of the first sun, before/while crashing down to earth. Presumably Naia (the first fake sun) emits magical heat as well as light, as this would neatly explain the "scorching" of the earth: its orbit is now lower (or perhaps just more elliptical, and thus lower at some points). I honestly don't have a good enough grasp of orbital mechanics to grasp how the short and long darks work, but I strongly suspect that there's no pair of natural orbits for a moon-like object and its planet around the sun such that things don't change drastically from day to day, especially when you throw in one or two original moons of the planet. Here's where the magic explanation comes in handy though: the creators of Naia wanted to reduce darkness, so they would have needed to cause Naia to be in-sync with the sun. So maybe they put it into a physically impossible (but magically possible) orbit that tracks the sun, and after the attempt at the second sun, this orbit was changed to a second sun-related but still physically impossible orbit.

[AI]

I honestly don't have a good enough grasp of orbital mechanics to grasp how the short and long darks work, but I strongly suspect that there's no pair of natural orbits for a moon-like object and its planet around the sun such that things don't change drastically from day to day, especially when you throw in one or two original moons of the planet. Here's where the magic explanation comes in handy though: the creators of Naia wanted to reduce darkness, so they would have needed to cause Naia to be in-sync with the sun. So maybe they put it into a physically impossible (but magically possible) orbit that tracks the sun, and after the attempt at the second sun, this orbit was changed to a second sun-related but still physically impossible orbit.

There is such an orbit, it's called sun-synchronous.

[solsword]

WARNING: Long rambling post with much math
WARNING: Minor stupidity ahead


Ah... excellent find. However, I'm pretty sure that Naia would have to be in a very specific sun-synchronous orbit: the orbit class described on that 'pedia page can have a variety of periods, and we know that Naia appears only twice a day (post-perturbation... I'm not going to try to speculate about pre-perturbation Naia). Approximating from the ToD images (of which there are 15, presumably each representing 1/15th of a day), we can see that Naia is visible in ~8 of them (and for about as many the first time we see it as the second). So Naia is visible twice a day, for approx. 4/15 * 24 =~6.4 hours each time. Now we have to take into account that for the precession to work out (see the Wikipedia page for details) the orbit *must* be retrograde (the opposite direction from the earth's rotation). Otherwise the short/long dark pattern wouldn't be able to hold up throughout the year, because the orbital plane would precess opposite the relative direction of the earth-sun line.

So with that knowledge, we can draw some simple conclusions:

First, if you're in a retrograde orbit and you pass above a particular point twice each day, that means that you've got the same period as that point (please correct me if I'm wrong, but as far as I can reason about this, anything faster or slower and you'll drift relative to that point, thus screwing up the short/long dark cycles in another way). So we can conclude that Naia's period is 24 hours (or it would be if it were orbiting Earth, which I'm going to work with here for simplicity), which I'll call "anti-geosynchronous." Now we've should be able to figure out the orbital radius in two ways: first directly from the period and next due to the dawn/dusk constraints (although this will give us an approximate answer).

*Without* taking into account the mass of Naia or the eccentricity of its orbit, the calculation from the period is straighforward ([1]). The period gives us an orbital velocity of 2π*r/(24*60*60) m/s where r is the orbital radius (from the center of the earth, not from the surface). The (highly simplified) equation for orbital velocity is v = sqrt(μ/r) where μ is the "standard gravitational constant" [2] and v is the velocity we just calculated. Plugging in and solving for r, we get r = cbrt(μ/C^2) where C is just 2π/(24*60*60). Note that we're working in km here, because that's what mew is given in on Wikipedia. That gives us r =~ 42 200 km, or about 35 900 km above Earth's surface. Oh, and if you look down the Wikipedia page [1], you'll see about the same value listed for a geostationary orbit (which we could have used in the first place ).

Now using dawn/dusk constraints: We know that the relative angular velocity of Naia and any point on the earth's surface is going to be 2 rotations per day (they're each moving at 1 rotation per day, in opposite directions). That means that in 4/15ths of a day, they travel about 4π*4/15 =~ 3.35 radians. To get some upper/lower bounds for this, I'll use 3/15ths and 5/15ths: we'll constrain the distance to between 2.5 and 4.2 radians. This means that dawn/dusk occur at between 1.125 and 2.1 radians of relative angle. And now we get to use trigonometry to try to approximate the radius. With these numbers we won't be very exact, since we're working close to π/2 here, but let's see what we get. We'll make the assumption that dawn/dusk occur at tangent positions (that is, at dawn or dusk, your location is on a tangent line to the source of illumination) and that the radius of Naia is effectively 0 (if it's a mountain, this shouldn't be too bad, because were using this relative to the radius of the Earth). These assumptions give us simply a/r = cos θ (or more simply, r = a/cos θ), where a is the radius of the earth (6 378.137 km), r is the orbital radius, and θ is the dawn/dusk angle, so either 1.125 or 2.1. Solving for r, we get r=~14 800 for θ=1.125 and r=~-12 600 for θ=2.1. Wait what? -12 600?

Okay, so I should have realized the obvious back when I made the 5/15ths constraint: the dawn/dusk angle can't be larger than π/2. So the constraint actually operates the other way: we'll use the orbital distance from the first part to calculate theta, and see if that gives us enough time...

Solving the dawn/dusk equation in reverse, we get θ = arccos (a/r), and using 42 200 for r, we get 1.419 radians, doubled to 2.838 radians over the entire period of illumination. Accounting for the doubled relative angular velocity, we get (2.838 radians/illuminated period) * (1 day/4π radians) = 0.2258 days/illuminated period, or 5.42 hours/illuminated period (assuming 24 hours/day). This is somewhere between 3/15ths (0.2) and 4/15ths (0.2666...) of a day, and is pretty reasonable.

---

So we've concluded that Naia is in a retrograde orbit with a period of 24 hours at a distance of about 42 200 km from the center of Irdya. It provides illumination for roughly 5.4 hours every time it rises (twice a day). Next, let's plug these numbers into the equation given for a sun-synchronous orbit and see what pops out. Is sun-synchronous precession possible with these parameters?

The Wikipedia equation [3] is (a bit) ugly and complex, those who wish to check my math can do so for themselves (and someone probably should... in fact, I may well have made a mistake in the calculations so far, although some common sense checks indicate that they aren't too far off). I'm using the following known values:

ωp = 2π radians / 362.917 * 24 * 60 * 60 seconds
ω = 2π radians / 24*60*60 seconds
a = 6 378 137 m
r = 42 200 000 m
J2 = 0.001083 somethings (directly from the 'pedia page)

ι (the inclination of the orbit) is unknown, but we'd like it to be between about 3/4 and 5/4 of π, since Wesnoth doesn't seem to be equatorial, but gets to see Naia every time it passes. Solving for ι, we get... stuck. I've got ι = arccos(-74.3), which doesn't work. To put it another way: if I solve for the rate of precession ωp, using ι = π (an equatorial retrograde orbit), I get ωp = 2.7 * 10^-9. Using either 3/4 π or 5/4 π, I get 1.91 * 10^-9. If I multiply these numbers by seconds per year, I get either 0.085 or 0.060 radians/year. The gist of this result is that given it's speed and location, Naia couldn't process fast enough around Earth to track the sun. However, Irdya might be a different matter, and throw in a little magic and it's believable.

So basically, Naia's post-perturbation orbit seems theoretically possible, and it's almost certainly an "anti-geosynchronous" orbit (a retrograde orbit with a period of 1 day) with some special magic or different orbital dynamics thrown in so that it can also be a sun-synchronous orbit. There's just one gaping hole in this argument: The UtbS night/day schedule has Naia and Sela visible together during *both* day periods. This implies that the entire schedule covers what used to be two days, which throws a major wrench in the works. And even more disturbing is that Naia and Sela are both visible at the same time during both a longer and shorter day. The only way that I can imagine that is for Naia to be in a non-retrograde orbit that's got a period of two days. During the first day, Naia would rise in the afternoon and set sometime during the night (effectively making the day longer). During the second true day, Naia would rise before dawn, but set around noon, lengthening the day a bit, but not as much. This would make the long dark longer than the short dark, but it wouldn't make it longer than a normal night (before Naia existed). Either the cataclysm slowed Irdya's rotation to make normal (long-dark) nights longer, or people were just so used to the extremely short Naia-regulated nights that they find the long dark to be particularly long.

Of course, placing Naia in a non-retrograde orbit like that is inconsistent with it being in a sun-synchronous orbit unless one of :

A. Irdya's rotation is opposite that of Earth's (Note that sunrise and sunset relative to North could be preserved by reversing the naming of the poles ). That would make no difference in terms of precession (I'm pretty sure), because precession is based on earth's eccentricity, not its spin, but would make an (Earth-relative) retrograde (and thus sun-synchronicity-preserving) orbit actually be non-retrograde relative to Irdya.

B. Irdya has eccentricity in the opposite sense from Earth. Correct me if I'm wrong here, but reversing the eccentricity should cause the direction of precession relative to the direction of orbit to be reversed. However, it would be kinda crazy, and might have other far-reaching effects (which might then have to be explained with magic)

C. Magic.

Oh, and I forgot:

D. No-one cares.

Anyways, I've spent enough time writing this post already... the last issue is that the ToD drawing times are a bit inconsistent, with this theory, because instead of one of the bright periods being longer (giving rise to a shorter dark period and a longer dark period), one of the *dark* periods is longer, and the bright periods are the same length. As far as I can tell, this is fundamentally inconsistent with normal orbital mechanics... but oh well.

[1] http://en.wikipedia.org/wiki/Orbital_speed
[2] http://en.wikipedia.org/wiki/Standard_g ... _parameter
[3] http://en.wikipedia.org/wiki/Sun-synchronous_orbit

[uzytkownik]

Personally I see different races using different calenders.

Elves - One of the oldest races of Wesnoth and with their longer lifespan I can see them having a more complex calender (i.e. one which repeats every 7-12 years or along those lines). Perhaps something linked to plants or lifecycles, something elaborate, elegant and frustratingly confusing for outsiders.

Dwarves - Another of the oldrer races, but being a predomonantly subteranian race. Lower units of time (like an hour) would probably be measuers by the burning of candles - potentially something humans could 'borrowed' when they met the dwarves. A calender I can see being simple and somewhat inaccurate.

Drakes - Unknown age, possible longer than the above. Probably based around the movements of the sun.

Saurians - Unknown age, middling to old. Lunar based obviously. Possible geometrical based on their maths.

Wose - Old, possible just a knowledge for how old related to the rings of a tree.

rings of a tree -> seasons -> sun calendar

Orcs and Goblins - Middling. Very little need for a calender to begin with, but when they begin to work with humans they could possible take a simplified version just so they understand the dates humans talk of.

I guess orcs & goblins so as savage as 'savage' people on Earth. I.e. 'savage' == 'long spoken tradition' (sorry I don't have this Pratchett so I cannot quote correctly).

Undead - Have no need or desire for a calender (who'd want to know how long they had been enslaved after their death for?)

I guess Liches uses the same calendar as the use when they were alive.

Gryphons - Knowledge of season but nothing written.

Mermen/maids - Something related to tides?

Nagas - Tidal but different to Mermen?

Tidal - i.e. moon-based.

[Darker_Dreams]

I have to say all the discussion of the second sun seems strongly like putting the cart before the horse. Whatever calender is used in the "post fall" world is likely to be derived from the pre-fall calenders. Meanwhile, reading the thread, the entire discussion of the physical possibility of something already in the game seems to have done little but derail the thread.
That said;

Cloud; your idea of using trees for month names is interesting, but I'm not sure how you/they would choose which tree to which month. Perhaps something more seasonal, like herbs, would still fit the elven mentality and tie to the monthly rotation better. I (for one) like the suggestion that elves might have a longer-view element of time, akin to decades but possibly less mathematically defined and more commonly used (trying to increase clarity, that should read; more like a 7 day week than a 10 day group of years). I'd suggest using tree-names to delineate the years of a cycle, possibly with the year-names being when a tree planted at the beginning of a cycle should first flower/bear fruit/something. Thus, while humans might track that their 1 YW is 6751 KE elves would track it as being in 482 (keeping your 14 name cycle), and view the count of 6751 like we would view someone who gave the date terms of months (example; in the US you reach majority at your 218th month...). This also gives a convenient place to have collected "leap days" for a festival. This is simpler for bookkeeping than your proposal, but keeps a level of complexity and drives back to the elvish longevity and nature-flavoring.
Personally, I'd have this calender shared between the elves and the Woses partially to provide some extra fluff showing their long-term entanglements and partially because the two cultures would be pretty parallel in thinking.

Ironically, with the comments about saurians being astronomers and the like, I'd do the special 14/24/etc year shifts in their calender, but I'd probably also tie that to the cycles of the other celestial bodies. Speaking of, in the main continuity there's 2 moons- the "main" moon is being proposed at a 26 day cycle (I'm taking the math on faith), do we have a proposal for the lesser moon? Another project I'm involved in (which coincidentally also has a greater/lesser moon arrangement) we used the greater moon as the month cycle and the lesser moon as a week marker. It's convenient, but physics suggests that may be inadvisable if you want realism (in that project it was both convenient and useful enough we decided to go with RoC), but if you're ok with a close enough, fast enough orbit and a long-ish week it works. A 14 day cycle, and thus saurian "week," would dovetail with some of the math stuff for Drakes nicely (totally not going back to my notes to check the physics right now, so someone can completely rip this on that level). It'd mean a 26 day month would have 2 and a fraction weeks, and would probably be used by no one else (possibly their close allies the drakes). For an astrological society it should mark something though. Beyond that, to develop the saurian calender as that of a a truly astronomically advanced race probably requires sorting out the solar system even beyond what most of the other races would know in-game.

As for the dwarfish calender, I like the idea of it being shorter-term and non-astronomical immensely- mostly because it is wildly different than most mundane calenders. If there's any culture that would have a partial-second it seems like it'd be the dwarves. I can see great fantastical clocks of all types- and potential craziness like measuring "days" that have nothing to do with the solar cycle. A race that emerged from the depths with unknown origin and able to function fine without light wouldn't be tied to the astronomical cycle and could have a circadian rhythm that did anything...
I do have to ask, do dwarves have a similar lifespan to elves? That's fairly typical, but reading the page on the dwarvish race I didn't see any commentary on life-cycle right off.


as a final note; While many campaigns ignore seasonal variations some, such as DiD, do use it and suggest significant seasons.

[AI]

According to SoF, "dwarves live longer than men", though that doesn't say too much.

[Darker_Dreams]

putting some feet to my suggestion of herbal names for months, here's a list of about 20 herbs I've found. The most obviously ridiculous herb-names have been weeded out (cabbage is counted as a herb by some apparently...) and I've verified that there's something in every season (sage a thyme as the heart of winter seem appropriate).

Spoiler:

Kale
Kohlrabi
Chicory
Endive
Mizuna
Tatsoi
Mint
Chirvil
Sage
Thyme
Hyssop
Yarrow
Wormwood
Hawthorne/Crataegus
Quince
Digitalis
Feaverfew
Valerian
Mullein
Goldenseal

I keep thinking about the dwarven calender, because it is open to such a novel approach... being tied to their own view of the world, in which the sun isn't automatically central, allows for a much different psychological space and allows their counting system to be very indicative of that, and their calender to be a raw expression of it unmodified by external seasons or cycles. The problem is, what's wanted in that space? Generally I see it as being something very rigid and ordered, but even that leaves a lot of room; a decimal system (base 10 or otherwise), a system of halves, some other system of counting based on geological or mineralogical features?