[Space] Adapting to long days and other implications of a generated system
 

I've been working on a world to use as a setting for an upcoming campaign, and I decided that I would work out the world's entire system with the Space rules.

I had decided that I wanted a double world, with two standard garden worlds orbiting each other, but all other details of the system I determined randomly.

Random generation came up with the following:
My world-pair consists of two worlds, which I'll call A and B.
A is practically a twin of earth (a result which I predetermined), except that it has only 50% hydrographics and it has a Warm (304K) climate.
B is a less-dense world, but with almost the same diameter; as a result, is has lower gravity (0.76 G), a Very Thin atmosphere and a Chilly climate (267K). It is also 80% ocean.

These worlds orbit each other closely, at a distance of only about 127000 km, and are tidelocked to each other, giving them a 98-hour day.

These worlds orbit a G6 star, with a luminosity of 0.61, and so have quite a short year (270 days, 66 local days).

In addition, the primary star has a relatively close compion, an M0 star (luminosity 0.091), which orbits at a distance of 6 AU (12.4yrs to orbit). Its orbit, however, has an excentricity of .5, so its distance to the primary star varies from 3 AU to 9 AU.

I want to use this as a setting for a fairly standard fantasy setting, but would like to see if the system as it stands offers any opportunities for interesting color or unanticipated difficulties. Specifically:

I intend there to be an established TL3+magic civilisation on planet A, which is the primary campaign world. Would it be feasible for this civilisation to have set up colonies on world B (a powerful empire in the past would have had the resource to teleport and/or set up gates to there)? I figure that their greatest problem would be the low air-pressure, but how well could a TL3 society be able to manage under those conditions?

Also, how hard would it be for normal humans to adapt to the 98-hour (four-DAY) days on such a world? Humans would have arrived on this world from Earth in a Banestormish way about 2000 years ago.
How well would humans arriving from modern Earth be able to adapt?

Since planet B is about 10x the diameter of the full moon as seen from A, I would think that in those parts of the world where B was visible, nights would be much brighter, but I don't know to which extent.

Another source of light would be the companion star. I don't know that much about astronomy, so I don't know how much difference it would make in the level of light during the day or night.

Are there any other interesting implications of this setting that I've missed?

Thanks in advance,

Indigar

Re: [Space] Adapting to long days and other implications of a generated system
 

This star is 1 tenth as bright as the sun and 3 to 9 times further away. The brightness decreases by the inverse square law so it will be 90 to 810 times less bright than the sun.

The star will be barely noticeable in my opinion, though I haven't had enough time to figure out the full maths. (If I get the time I'll figure it out exactly for you).

Re: [Space] Adapting to long days and other implications of a generated system
 

Since the worlds are orbiting each other, there will be a Long Night (approx 48 hours) and a Short Night (around maybe 10 hours?) caused by the daily eclipses by its companion. Those with better math might be able to come up with the exact number of hours, but it will have an effect on the society's rhythms.

Next question: how would a 49 hour night followed by a 20 hour day followed by a 10 hour night and then another 20 hour day affect circadian rhythms? Would it be synced to the day/night cycle, or would it be something totally separate, and not linked to day and night at all?

If there are good light sources (or good night vision) it may not matter as much.

Another note: Only the half of the world facing its companion will have this cycle. The other side of the primary world will never see the companion, and won't have the Short Nights.

Re: [Space] Adapting to long days and other implications of a generated system
 

Assuming they are on a plane with the sun yes, but they might not be.
If they are on a plane you will also have the bright night, the dark night followed by bright night as the companion planet is eclipsed by the main planet for 10 hours during the night.

Also clouds are very reflective so depending on how much cloud formation there is on the ice planet I would list the bright-night as giving only -1 or -2 in vision penalties due to darkness. Doing some back of the envelope math shows the ice planet reflecting so much light that it would be roughly 400 lux equivalent to a brightly lit office. Of course I was assuming the sun for that.

Wheather (and the seasons) on the other planet will affect how much light there is during the night, because clouds are very reflective. The planets could also function as weather satelites for each other and so I assume weather forcasting on the sides of the planets facing each other will be more advanced. Weather forecasting is very valuable to farmers, and for a TL3 society most people are farmers, but taking advantage of the good vantage point to observe clouds from above will require observers to work together. probably some form of guild or government department.

Better telescopes too because you can use the planet to spy down on the other one. you would need a good one to see armies on the march and such, though campfires should be easy to spot at night.

it's going to mess up day-night rythms something fierce but for humans at least the system is very dependent on light, which is why electric lightbulbs have messed it up so much for modern man. Try living without electric lights for 2 weeks, it makes an amazing difference.

Re: [Space] Adapting to long days and other implications of a generated system
 

the sun gives on average about 50'000 lux, divide by 1000, 50 lux is around the light in the family living room.

I'd say that's noticable alright.

Re: [Space] Adapting to long days and other implications of a generated system
 

Astronomical magnitude is a logarithmic scale with a factor of about 2.5x brightness for each step. (The fifth root of 100, if you want to be exact.) 0 magnitude was historically Polaris, then Vega, then just a defined value for flux. High numbers are more dim; very bright objects have negative magnitude.

The sun is magnitude -26.7 (449,000 times brighter than the full moon). The full moon is -12.6.

-4 is barely visible during the day. Planets range from about -2 to -3. Visible stars in the night sky are typically 0 to 6.

1/90th the brightness of the sun is about magnitude -22. 1/1000th the brightness of the sun is about magnitude -20, both still far brighter than the full moon. Or to look at it another way, the companion is about as far away as Jupiter, but a million times brighter.

The companion probably casts its own shadows during the daytime.

Re: [Space] Adapting to long days and other implications of a generated system
 

Eclipses don't last that long. It wouldn't really be all that difficult over a couple of thousand years for humans to adopt a 32 hour awake/16 hour asleep cycle, maybe with a nap in the middle. Of course most of the time the night will be fairly well lit what with the giant moon and the close stellar companion. In fact the moon will be reflecting so much light that there would probably be noticeably less difference between day and night temperatures.

As for the very thin atmosphere, it would be...difficult to colonise it without actively modifying humans to fit using something like magic biotech. Just about impossible. It doesn't help that 80% hydrosphere means their sea level is comparitively high. On the other hand if somewhere in there they have a super-Grand Canyon, something that goes really really deep at the bottom they might get up to Thin Atmosphere there. But I can't imagine how to keep it from filling up with water.

Re: [Space] Adapting to long days and other implications of a generated system
 

No, surely the sun is no brighter than a firefly...

Uhhh, yeah. What I said before was pretty dumb. Don't know what I was thinking. Been a bit off my game tonight.

Re: [Space] Adapting to long days and other implications of a generated system
 

Hey all!
I've been away from my computer for a while so I haven't been able to respond, but I have been continued working on this setting.
I'll respond to posts by several posters in this post.

Thanks. I've checked, and the axial tilt of these planets is only 9 degrees.
(I've assumed that the strong tidal forces that have tidelocked these worlds have also locked their axial tilts to be equal to their orbital inclination, so that they rotate and revolve in the same plane. Is this right?)
This means that the planets are very close to being in line with the sun, so I assume there will be frequent, probable even daily, eclipses.

Since the apparent diameter of these planets from their companions' surface is about 10x the diameter of the moon, they're about 5 arcseconds wide. I believe that makes such an eclipse 5"/360 deg* 98hrs (day length) = about 15 minutes. This doesn't fit with your figure of 10 hours; have I miscalculated?
If I'm correct, these daily eclipses are not going to have a significant effect on day/night rythms, so we're back to a difficult-to-adapt-to 48 hrs each of day and (quite bright) night.

Ah, thanks. So you think there would not be much of a difference in activity between day and night? Just 32hrs awake/16 asleep twice per day/night cycle?
this is indeed doable if nights would indeed be as bright as normal office lighting...
I'm wondering what kind of effect this would have... I envision different cities' wake/sleep cycles drifting out of phase is they weren't in constant contact; in fact a different time zone for each somewhat-isolated area! That could be a fun detail.

Would it be more doable if I declared there to be a much higher percentage of oxygen? Since the atmospheric pressure is about 0.46 atm, could I simply double the oxygen percentage to 40%, or would that cause other effects.
I'm wondering why a high sea level would matter. Wouldn't the pressure that Space gave me simply be the sea-level pressure?

Anyway, thanks for the help so far everyone.
I'll think about this some more and post more later about what I come up with.

Re: [Space] Adapting to long days and other implications of a generated system
 

I'm not sure what other effects there might be, but that would bring the partial pressure of oxygen up to a level that humans can work with, yes. I'd be concerned about the eyes in the cold, thin, and dry air however; aviator goggles or something like a ski-mask or inuit snow-blindess goggles might be in order.

How this would affect combustion, I have NO idea. A magical society may be using Create Air and Heat spells inside buildings, however, just to make them more comfortable. Weather Dome and Atmosphere Dome will still likely be VERY popular, even if humans can live unaided outside. I imagine their mages would rapidly develop a permanent, enchantment form of Atmosphere Dome which would likely be popular with rich people for their sleeping chambers.

Re: [Space] Adapting to long days and other implications of a generated system
 

Actually, why not give locals Low-Pressure Lungs. Instant solution.

Re: [Space] Adapting to long days and other implications of a generated system
 

Actually, if the two planets are tidally locked, each planet will have a permanent tidal bulge facing its twin, and another on the far side, with relatively shallow seas in between.

Re: [Space] Adapting to long days and other implications of a generated system
 

My number was a WAG based on feel more than actual mathematics. :-) But, as it turns out, I had forgotten that these two worlds are spinning around each other 7 times faster than the Earth/Moon system. So I was even more wrong than I had thought.

15 minutes is probably correct. A lunar eclipse can last up to 107 minutes, and when you divide that by 7 you end up with...15 minutes. (Kind of too bad, really, I kind of liked the "long night/short night" concept, but obviously it's just too wrong to work :-)

Re: [Space] Adapting to long days and other implications of a generated system
 

Well, they'd need a siesta in the day and a waking period in the night. Or they can arrange a cycle with four sleeps per day. That's not a problem.

You have a bigger problem with daily temperature variation. The days will warm up more, and the nights cool down more. This will be uncomfortable to animal, dangerous to plants, and will drive strong diurnal winds (onshore and anabatic during the day, offshore and catabatic during the night). On the other hand slow rotation means low Coriolis forces, so cyclonic winds will be weaker.

Speaking of plants, the long day-night cycle will challenge the physiology of plants from Earth. The light half and the dark half of their respiratory cycle are adapted to a twelve-hour duration. I don't know how much trouble this will be.

Summary: in his classic Habitable Planets for Man, Stephen Dole assumed that the upper limit on the daylength for habitability by Man was 96 hours, because of diurnal temperature variation killing plants.

Incidentally, don't forget that because each planet is tide-locked to the other, each is in synchronous orbit about the other. That means that, seen from each planet the other holds a fixed position in the sky. That means that it is visible (always in the same place) from one half, and is never visible from the other.

Re: [Space] Adapting to long days and other implications of a generated system
 

The inhabitants of one side of the planet have a pantheon of wandering gods associated with the visible planets, while dismissing as ludricrous heathen myth rumors of the monotheistic religion of the antipodes between the pair, with their one all-powerful god with a few attendants.

Re: [Space] Adapting to long days and other implications of a generated system
 

I dimly recall a psych study involving locking a test subject in a habitat that lacked clocks or other discrete time measures. The subject was encouraged to follow whatever cycle was comfortable, with the aim of extending it if possible. I believe that they found subjects could adapt in time to a 32-hour awake, 16-hour asleep cycle.

In this situation, it sounds like the secondary is going to be a significant source of light, anyway. So probably the inhabitants of the system will develop thick window shades and a complex mechanism for charting time based on the movements of the primary, the secondary, and their eclipses by the partner. Day and night cycles may either become relatively meaningless or a source of religious ritual and mystic belief.

I don't imagine, even with a high partial pressure of O2 that the companion planet is going to be comfortable for long-term human habitation without significant magical or technological help. But I'm not sure that this is a bad thing. Maybe the companion is the home of the sorcerous elite, ruling over the lesser mundanes. Or maybe the companion is a place rarely or never visited, a location of myth and wonder. Ever since the Great Exodus, no one has gone there and lived to tell about it...

Re: [Space] Adapting to long days and other implications of a generated system
 

Nope. The water in the oceans will conform to the tidal bulge for the same reason the bulk of the planet does. You do recall that sea water is affected by the tides, don't you?

So the planets will be somewhat prolate (elongated) with their axes pointing at each other. But the pattern of land and water will be spread out all over their surfaces.

Re: [Space] Adapting to long days and other implications of a generated system
 

That's what I meant; the oceans inline with the other planet will be at a permanent high tide. Any oceans on the orthogonal meridians will be shallower. And since the planets are larger and nearer to each other than the moon, they'll be very large tidal forces.

Re: [Space] Adapting to long days and other implications of a generated system
 

The water will deform more and faster than the planets main mass will, so it's still going to be deeper on the side of the planet facing the partner, shallower on the sides, and then deeper again (but not as deep) on the far side of the planet.

Re: [Space] Adapting to long days and other implications of a generated system
 

Relatively speaking. The depth is more to do with underlying geography - where the mountain ranges and the trenches are.

Re: [Space] Adapting to long days and other implications of a generated system
 

Yes, but the bulk of the planet will be at permanent high tide there too. And since it is permanent in geological terms, the mantle material will have the necessary tens of thousand of years to conform fully to the tidal equipotential. The water and the rock will be distorted to the same extent, they will conform to the same geoid. So the oceans will be about the same depth all over. Slightly deeper where the net effective gravity is lower, perhaps, but not enough so to produce vast oceans around sub-lunar point and its antipode and vast continents on the orthogonals.

Re: [Space] Adapting to long days and other implications of a generated system
 

It doesn't matter that the mantle material deforms more slowly than the water, because the tidal bulge never moves. It stays in exactly the same spot for millions and millions of years, whereas it only takes tens of thousands for mantle deformation to reach equilibrium.

Slower deformation doesn't mean less deformation. Both rock and water reach equilibrium in a geologically brief time, and it is the same equilibrium for both.

Re: [Space] Adapting to long days and other implications of a generated system
 

OK, your replies have given me some more food for thought.
I've been doing some more number crunching, and have worked out some of the social details and such.

Firstly, because the planet's axial tilt is so low, seasonal variations will be very mild. I checked whether the companion star's large orbital excentricity, and thus the large difference in distance to the planets during its orbit would cause seasons, but even at closest approach its contribution to the planets' temperature is negligable.

So, I've come up with the following:
The calendar is based on a year of 66 days; this is devided into the four seasons/months: Spring of 17 days, Summer of 16, Autumn of 17 and winter of 16; every 10th year is a leap year, when the last day of Winter is dropped, and once every 40th year, when this day is _not_ dropped.

Longer-duration temporal cycles are based on the orbit of the companion star (which takes 16.76 local years):
The years are grouped into Cycles of 17 or 16 years: Three cycles of 17 years followed by one of 16 years; four of these cycles make a Great Cycle of 67 years.
And, 25 Great Cycles make a Grand Cycle; the last Cycle of the last Great Cycle of a Grand Cycle is once again 17 years instead of 16. Thus, a Grand Cycle is 1676 years.
The current dominant society does not count the Grand Cycles; the counting of years begins at the beginning of the current Grand Cycle, when, according to tradition, the Voice of the Gods began his ministry (This is counted as the beginning of the dominant religion).
At the beginning of the campaign, it is the 13th day of Spring of the 1321st year, or as it is usually described, the 13th of Spring of the 14th year of the 3rd Cycle of the 20th Great Cycle since the Proclamation of the Gods (Short form 13 Spring 14:3:20).

I think this is a system that is simple enough, but also different enough to give the flavor of a different world.

Other stuff:
The day is divided into 100 local hours, each of which is slightly shorter than an Earth hour. Hour 0 or 100 is at sunrise.
In the area in which the campaign begins, the Sister planet is above the horizon. This means that, each day about 10 hours before sunset, there is an eclipse of the sun lasting about 10 minutes, and an eclipse of the Sister about 10 hours before sunrise. In addition, there is an eclipse of the Companion star, the time of which depends on the progress of the current cycle; currently, it falls about 10 hours before midnight.
The normal sleep cycle is 33 hours awake, 17 asleep; therefore, there is one full sleep/wake cycle during each of night and day. By tradition, people go to bed around the time of the eclipses of the Sun and the Sister.

In mythology, the Sun is the Mother Goddess, and stands for life, fertility, etc. The Companion is the Father God, and stands for law, order, civilisation, etc. The Sister is the literal Sister of the world, and is said to have angered the Father and the Mother shortly after Creation; because of this, it receives only little warmth from the Mother. During the fallen Empire attempts were made to colonise it (over the objections of the Church), but there is no longer any contact with it. (It is still inhabited, but only sparsely, and its TL has fallen to 2).
The dominant religion recognises two gods, the Mother and the Father. Each of these has its own seperate Church (the Mother church ordains mostly women, the Father church mostly men), but these are closely allied (though they do not always agree on all issues), together forming the Joined Church.

Well, that was what I've written down so far. It's mostly random thoughts that I've worked out about this system, but I'll develop it some more later.

Any further comments?

Re: [Space] Adapting to long days and other implications of a generated system
 

Did you check whether the eccentricity of the twin planets' orbit around their primary induces seasonal effects? I find that the GURPS Space star system generation sequence gives planets's orbits such high eccentricities that it is worth calculating surface temperature at perihelion and aphelion.

Re: [Space] Adapting to long days and other implications of a generated system
 

I didn't think to check this, since I thought an eccentricity of 0.05 was pretty low. I now see that Earth's eccentricity is 0.017, so that is indeed quite a bit higher.
I get a difference in BB temp of 14K due to excentricity, but I have no idea what effect this would have in real-world terms. I get 4K for Earth's variation, but I don't know how much difference 6 degree tilt versus Earth's 23 degree tilt makes; would this mean that this planet's seasons are more or less extreme than Earth's (assuming a point on the surface where tilt-seasons and eccentricity-seasons combined)?

Re: [Space] Adapting to long days and other implications of a generated system
 

The higher the percentage of oxygen, the easier things burn even if the partial pressure of oxygen is kept the same. At 40% oxygen, there's not likely to be much land life, with the land scoured by wildfires when even moderate amounts of biomass build up.

Luke

Re: [Space] Adapting to long days and other implications of a generated system
 

You know, GURPS abhors randomly generated characters - why would you randomly generate your world? I like the system you have, but you should certainly feel free to adjust it any way that pleases you - you have to live with it, after all. Does Space allow you to work backwards? Eg, I want dual planets, how does that change other factors?

Re: [Space] Adapting to long days and other implications of a generated system
 

Or plants evolve to use it to procreate the way some trees do on earth.
Or plants evolve fire resistant coatings, so only dead brush blazes.
Animals evolve to run... the... h*ll away.
Animals evolve to dig deep fireproofe tunnels, seal the entrances, and go into suspended animation.

Re: [Space] Adapting to long days and other implications of a generated system
 

Yes. It won't let you work backwards from tides or anything that is causally "downwind" from tides, such as day-length. But it will otherwise.

Re: [Space] Adapting to long days and other implications of a generated system
 

Average temperature variation for 6 degrees tilt is probably only 1 or 2 degrees (sunlight per unit area should be proportional to [1/cos tilt-angle] squared and 6 degrees tilt gives about [edit] a sixteenth of the variation that 23 degrees tilt does at the equator and about a 24th outside the tropics)

So including the 14 degrees for eccentricity you are looking at perhaps 16 degrees overall average annual temperature variation.

Its seasons will be more extreme near the equator than Earth's but less extreme overall. Earth's equator only sees the temperatures vary by single digit degrees. Whereas Earth's poles see something like a 30 degree variation over the year.

Earth does get a theoretical 4 degree temperature variation with it being warmest at perihelion around 4th January each year (southern hemisphere summer), though the oceans buffer the rise.