How do you measure time on a tidelocked planet?

[Aotrs Commander]

It's difficult to to know to put this question, so the for the sake of argument, I've put it here.

This is both a biomechanical and sociological question.

There is a planet. It orbits around a large star whose goldilocks zone is significantly far from the star that the orbit is measured in thousands of Earth-years¹. The planet is tide-locked². The planet is otherwise the same size and atmospheric content as Earth, but the life that developed is entirely alien.

So. Because the world is tide-locked, there is no day/night cycle and there are no seasons (the orbit cannot be erratic). So you can't measure time by the sun or the stars. In any case, as the plant remains largely habitable by the stabilising feedback of clould cover, the sky isn't always readily visible (and it's often raining). At ground level, there is a continuous stiff breeze coming from the dark side to the light side (again, part of the researched climatic conditons).

So how do you measure time, if you are a plant or a creature or a primitive neolithic tribe?

(Civilisations might make their own measures - I'd have to research into the history of who "invented" hours/minutes/seconds, but the larger question is more fundamental.)

This question arises as I contemplate, as I do on and off, a campign game in which the PCs are part of a neolithic tribe, who are forced on a migration by changing geological conditions. As I was thinking about it today about the mechanics of it, I considered "well, you could simplify food to be 1 unit per person per day, maybe half for young children under... five... Wait, hang on. How long is a 'day?' For that matter, how do you measure what's a 'young child?' How long, even, is a guard duty shift going to be...?"

This is a rather metric defining question, the more I think about it.

Athe most basic level, how does a plant know when to flower or seed? If it doesn't rely on insect-analgoue pollination, how do plants seed? They can't reliably use wind, since it for the majority only goes in one direction. Rhisomes are one obvious answer, but the other might be as interesting as like the Earth plants which shoot their seeds. But even then - what is the interval? In terrestrial jungles where there are no real seasons, trees of different species fruit at seemingly arbitrary periods, but even there, there is a day/night cycle to work off.

What is an animal's activity cycle going to be like? Again, on Earth, where there are places were day and night are both very long, they do change over. (I'm not even sure how long/when polar creatures sleep during the summer). Logically, one would assume that such creatures to have an functionally cathemerial cycle (i.e. for animals that vare active during both day and night), but even those are subject to the circadian rhythm which is absent here, so what instead defines the period?

For a primitive tribe, how would their society have developed to tell the passage of time? How often do they need to eat, when the basis is not a 24-hour circadian cycle? How do you tell how old someone is (and thus when they reach maturity)? Is there a specialias jon, like a time-keeper in the village whose sole job it is to measure time and how?

This is a very difficult question for me to answer, to the point I'm not even sure where to start looking. Thus, as inspiration (rare these days) has struck me to think about it, I have asked in a few places to see if anyone can offer any suggestions.



Now, in my earlier contemplation of this question, I did make one concession. There is a moon, a relatively late capture. This orbits once every six Earth-days, but though it appears about the same size in the sky as Luna to Earth, it's very small and low mass. (Tides is a difficult question, though it appears to impart about 94% of the acceleration Luna imparts to Earth, due to it's speed. It is assumed to be partly why the planet is not 100% completely tide-locked.) But that's nowhere near fundamental enough for the biology side of the question and aside from potential tides, the moon again won't be readily visible for an easy count even for a civilisation.



I can, of course, elaborate in more detail about the set-up, but I have tried to keep this down to the minimum required boundary conditions, else the question would likely be lost amid the rest of it.




¹There is a long and complicated explanation (in involved a lot of astrophysics maths, among other things) as to the set-up, but I have omitted it here for breivty and relevance to the question at hand.

²Strictly speaking, it's ins't 100%, but the day length is also in thousands of Earth-years at a minimum.

[a_flemish_guy]

seasons could be measured in how long it takes for crops to grow in
semi-nomadic herdsmen often sewed crops and moved on and came back when it was time for the harvest

an hour could be measured in the time it takes for a campfire to need new logs, later on candles could be used for more accurate measurements, even later things like waterclocks could be introduced

so people's ages would be recorded in seasons and activities would be measured in hours

sleep comes naturally after a while so days could be measured by the times you've slept (if you want to say a week from now then you'd say after we slept for 7 times), it'd be hard to accuratly pinpoint this however so this method can only be used if you live close to the person you're dealing with (edit: just saw your post about the moon, so yeah, weeks are 6 days and are depended on which stance the moon is in)

overall, quite an interesting question, need to think more about this

[King of Nowhere]

well, quite an interesting conundrum. I also assume that there are no satellites of the planet to give a natural clock

So how do you measure time, if you are a plant or a creature or a primitive neolithic tribe?

i'd say that you probably don't measure time at all. after all, measuring time is something needed in a planet where stuff is changing.
a plant certainly does not measure time. a plant on earth may measure time to ensure to release seeds in spring, so that they will find favorable growing conditions in the earliest, most vulnerable part of its life. but in a planet without season, why bother? a plant would release seed whenever it's ready.

(Civilisations might make their own measures - I'd have to research into the history of who "invented" hours/minutes/seconds, but the larger question is more fundamental.)

This question arises as I contemplate, as I do on and off, a campign game in which the PCs are part of a neolithic tribe, who are forced on a migration by changing geological conditions. As I was thinking about it today about the mechanics of it, I considered "well, you could simplify food to be 1 unit per person per day, maybe half for young children under... five... Wait, hang on. How long is a 'day?' For that matter, how do you measure what's a 'young child?' How long, even, is a guard duty shift going to be...?"

our culture depends on time, but i'd say a culture growing on that planet would develop differently from us. time is important for us, it probably wouldn't be for them. not until the industrial revolution, when you need to have everyone come to the factory at the same time to work. for an ancient society where people work mostly alone, if you work in your field while your neighboor is sleeping, does it matter? in our world people started working at dawn because they needed light to see, but in your case they have light all the time.
and there's going to be some advantages. you don't need a night guard or something, because there is always someone awake at any time.

people eat when they are hungry. sleep when they are tired. a young child is one who's in a certain phase of physical development. those are easy questions. how long are guard duty, or any other duties, they are likely to eyeball it. and there would be no guard duty because everyone sleeps differently.

or maybe a tribe would syncronize their rythm - they do need to walk together when moving, after all; hunter gatherers need to act together - just by consensus, or by leadership.
consensus: when enough people are awake, they wake up the others. when enough people go to sleep, the others follow.
leadership: when the chief goes to sleep, everybody does. when the chief wakes up, everybody does.

This is a rather metric defining question, the more I think about it.

Athe most basic level, how does a plant know when to flower or seed?

when they reached maturity and have gathered enough nutrient storages needed to produce seed. time is irrelevant. it's not like they have to wait spring to give their seed the highest chance of survival.

If it doesn't rely on insect-analgoue pollination, how do plants seed? They can't reliably use wind, since it for the majority only goes in one direction. Rhisomes are one obvious answer, but the other might be as interesting as like the Earth plants which shoot their seeds.

fruits are the easy answer. an animal eats them and carries the seed in every direction.
fruits are quite complex evolutionary, and ancient plants would not have them available.
you can also make seeds extra light so that they can fly on winds long enough to get raised and moved towards the night side (because the wind can't just blow in one directon forever. i assume in the higher atmosphere the wind blows in the opposite direction, forming a convection cell).
but yes, rhisomes are the easy answer.
making long limbs that drop heavy seeds may also be viable.
shooting seeds doesn't seem very effective; how far could they go?

But even then - what is the interval? In terrestrial jungles where there are no real seasons, trees of different species fruit at seemingly arbitrary periods, but even there, there is a day/night cycle to work off.

why would there even be an interval? we rely on time because on our planet we have reasons to do things at certain times, because some times are more favorable than others. in a planet where time is not relevant, the question wouldn't even make sense. that neolithic tribe may not even have a word for time, not on larger intervals. it certanly would not have words for days, weeks, years.

What is an animal's activity cycle going to be like? Again, on Earth, where there are places were day and night are both very long, they do change over. (I'm not even sure how long/when polar creatures sleep during the summer). Logically, one would assume that such creatures to have an functionally cathemerial cycle (i.e. for animals that vare active during both day and night), but even those are subject to the circadian rhythm which is absent here, so what instead defines the period?

creatures have a biological clock inside them. like, put you in a closed room, and you still have a rough idea of how much time has passed.
but it's not accurate. nor does it need to be. why would animals even have a circadian cycle in a planet without a day?

For a primitive tribe, how would their society have developed to tell the passage of time?

for short time intervals; when you get hungry, when you need to pee, that sort of stuff. for longer times: when grandfather was young, before you were born. not that they'd be used often, because there's no reason to refer to long time intervals; maybe reserved for mythology.

How often do they need to eat, when the basis is not a 24-hour circadian cycle? How do you tell how old someone is (and thus when they reach maturity)? Is there a specialias jon, like a time-keeper in the village whose sole job it is to measure time and how?

you are still thinking in modern terms, where we make so much fuss about time - mostly because we depend on objective measures.
people do need to eat when they get hungry. if you were locked into a closed room with no clocks, would you be like "omg I don't know when I have to eat"? nope; at some point you'd grow hungry, and you'd eat. then you would not be hungry for another while.
and you certainly do not need a calendar to tell the difference between a child, a kid, a young adult, a mature adult, etc. in fact, even as late as the middle ages most people didn't knew the year they were born with precision. it just was not important. as for telling when someone is an adult, our society set 18 years old because we need an exactly written law. in ancient societies, mostly women were married as soon as adult - could be anywhere between 12 and 16 years of age, because they had to make children as soon as possible to compensate for a mortality rate that's inconceivable for modern standards. and males would have to undergo some sort of passage ritual, generally a show of strenght and bravery. and yes, without a calendar somebody would undertake that ritual when equivalent to 16 earth years, someone when 20, but again, does it matter for society? the important thing is that when that kid looks grown enough, we send him out to kill a lion, or to put his hand into a bowl of bullet ants, or whatever they use as ritual. and then the guy is an adult.

as for somebody whose job is to keep passge of time... it's not impossible, but my gut says they wouldn't even conceive passage of time as we do. they do not experience progress like we do. therefore, they wouldn't see time as a past and future. they'd see it as a static thing, where nothing ever changes really. there is the tribe, and before i was born there was the tribe, and after i'll die there will still be the tribe, and why should i care about the passage of time if nothing ever really changes?

This is a very difficult question for me to answer, to the point I'm not even sure where to start looking. Thus, as inspiration (rare these days) has struck me to think about it, I have asked in a few places to see if anyone can offer any suggestions.



Now, in my earlier contemplation of this question, I did make one concession. There is a moon, a relatively late capture. This orbits once every six Earth-days, but though it appears about the same size in the sky as Luna to Earth, it's very small and low mass. (Tides is a difficult question, though it appears to impart about 94% of the acceleration Luna imparts to Earth, due to it's speed. It is assumed to be partly why the planet is not 100% completely tide-locked.) But that's nowhere near fundamental enough for the biology side of the question and aside from potential tides, the moon again won't be readily visible for an easy count even for a civilisation.

ok, i missed that part earlier. so they will have "weeks", after all. could be useful to measure time in the middle ranges, like "to reach the pastures to the east, we have to march for two weeks". but it wouldn't be a big part of people's life.

it can be hard, but you have to get out of modern scientific accurate mentality to understand neolithics tribes.
once an anthropologist visiting such tribes in the real world asked how far was the nearest village, he was told "two rice cookings". as in, start walking, and in twice the time it takes to cook rice, you'll be there. this is also something that they could do on your planet.
and it's a terrible measure for us; it depends on whether you like your rice hard or soft, how fast you walk... but it's good enough for a society that does not have to wake up at 7 am sharp to take the bus.

[Palanan]

Originally Posted by Aotrs Commander
So you can't measure time by the sun or the stars.

Even if the planet is tide-locked, that only affects its own rotation; it continues orbiting around the star, and thus its view of more distant stars is constantly changing.

That will establish the planet’s year—but if that’s thousands of our years, then you’ll need another metric. If there are other planets in the system, their motions will help establishing a cycle.

Note also that a larger planet is likely to have a number of larger moons, and their motions would be complex but predictable, in the same way that we can measure the 4:2:1 resonance of orbital periods for the inner three Galilean satellites of Jupiter.

Originally Posted by Aotrs Commander
In terrestrial jungles where there are no real seasons, trees of different species fruit at seemingly arbitrary periods….

Not arbitrary at all. Equatorial forests do have seasons, just not ones involving snow. Often there’s a wet season and a much, much wetter season, and note also complexities such as ENSO. Also, the day/night ratio is key. Fruiting seasons are not arbitrary in the least; fruiting is metabolically expensive, and obviously vital to the plant’s reproduction, so its timing is carefully regulated.

Originally Posted by Aotrs Commander
There is a long and complicated explanation (in involved a lot of astrophysics maths, among other things)….

I’d be very interested in seeing more of this. My only sense of tidally locked planets is the born-of-a-red-dwarf variety, so I’m wondering how this is possible at +500 AU, or whatever distance you’re using.

Also, is there a real-world example you’re basing this on? And how is this planet warm enough to support vertebrate-analogue life?

Originally Posted by King of Nowhere
I also assume that there are no satellites of the planet to give a natural clock

Please note the OP’s thirteenth paragraph, which describes the planet's moon in some detail.

Originally Posted by King of Nowhere
once an anthropologist visiting such tribes in the real world asked how far was the nearest village, he was told "two rice cookings".

This sounds highly suspect and likely apocryphal. Do you have a citation?

[Aotrs Commander]

well, quite an interesting conundrum. I also assume that there are no satellites of the planet to give a natural clock


i'd say that you probably don't measure time at all. after all, measuring time is something needed in a planet where stuff is changing.
a plant certainly does not measure time. a plant on earth may measure time to ensure to release seeds in spring, so that they will find favorable growing conditions in the earliest, most vulnerable part of its life. but in a planet without season, why bother? a plant would release seed whenever it's ready.


our culture depends on time, but i'd say a culture growing on that planet would develop differently from us. time is important for us, it probably wouldn't be for them. not until the industrial revolution, when you need to have everyone come to the factory at the same time to work. for an ancient society where people work mostly alone, if you work in your field while your neighboor is sleeping, does it matter? in our world people started working at dawn because they needed light to see, but in your case they have light all the time.
and there's going to be some advantages. you don't need a night guard or something, because there is always someone awake at any time.

people eat when they are hungry. sleep when they are tired. a young child is one who's in a certain phase of physical development. those are easy questions. how long are guard duty, or any other duties, they are likely to eyeball it. and there would be no guard duty because everyone sleeps differently.

These are good points (I've not quoted everything) and simialr has been suggested on the other place - but here, at least, there are some interesting mechanical constraints to worry about. Specifically, if the PCs are leading a tribe and are resposnible for managing the resources... How do I track the usage and consumption of resources? As I said, it's fine to simply say "each tribesperson needs 1 food and 1 water per" but the problem now becomes how to determine what per what. Distance might be partly one answer, but then how do you measure it if they stop?

(Small stuff like durations of effects in rounds/minutes and such don't matter so much and I can just handwave them away as mechanical game effects, it;s the mid-and long-term units which are the problem.)

I am trying to avoid arbitatily assigning a "day" period "eats?", at least not without considerable thought. It might be necessary in the end, but dang it if I'm not trying to make an effort to give it as much investigation as possible beforehand.

as for somebody whose job is to keep passge of time... it's not impossible, but my gut says they wouldn't even conceive passage of time as we do. they do not experience progress like we do. therefore, they wouldn't see time as a past and future. they'd see it as a static thing, where nothing ever changes really. there is the tribe, and before i was born there was the tribe, and after i'll die there will still be the tribe, and why should i care about the passage of time if nothing ever really changes

The campaign - if it ever comes to be - would predicated, ironically, on a major change. My intention was that they would be essentially a fishing village on the edge of a large inland lake/swamp bordered by mountains. (There is a gas giant in the system in resonance, which creates some volanicity, so everything isn't flat.) The lake was blocked off from the sea by a deterioriting land wall, and would be finally breakign down and flooding the region, forcing said tribe to embark on an oddsessy through the mountains and out.

However, to go a bit deeper, the world acually changes quite a lot, is just the changes tend to happen on the lifecycle of civilisations, not people.

To whit: in addition to the very slow creeping shift of the day/night lines, every so often (and a semi-random interval), the star dims. (The idea is based on RCB variable stars, which change in brightness - not much change in the IR specturm, mostly just visible - but turned up to 11). So you have a world where civilisations develop and sometimes get quite far, and then are plunged into a literal dark age when the sun dims, leading to extinctions... Until the next time. But the periods are long enough that the successive lot generally doesn't even know it happened, basically. (Funnily enough, when nothign changes for a very long time, every tends to get fracked up when it changes rapidly.)

(Meaning a campaign world full of Stuff To Explore...)

Some of the inspiration from this comes from an old Doctor Who episode (3rd or 4th Doctor, I think?) wherein the Doctor and co visit a planet appearing to be suffering from a Horrible Mutant Plague, but it turns out their planet has a stupid long eccentric orbit or something, and every so [however long], the climate changes and their biology adapts and they, like, change into crab people or something for the harsher "winter" conditions. I.e., the biology (and that of the planet) is geared up for the change, but the civilisation ISN'T, queue panic.



BUT. In this specific case, taking what you say into account, one might observe that it could be a thing for the PCs to have to DEVELOP a method for keeping time, as they now require it as they have had to leave stasis behind, which is not something I'd previously considered. (Still means I have to know what the resource usage time limit, is though.)

(They were already intended to be in a position where, nevermind a bag of holding, a BAG is valuable treasure...! Though it is surprising what technology they DID have in the approximate period on Earth.)

ok, i missed that part earlier. so they will have "weeks", after all. could be useful to measure time in the middle ranges, like "to reach the pastures to the east, we have to march for two weeks". but it wouldn't be a big part of people's life.

it can be hard, but you have to get out of modern scientific accurate mentality to understand neolithics tribes.
once an anthropologist visiting such tribes in the real world asked how far was the nearest village, he was told "two rice cookings". as in, start walking, and in twice the time it takes to cook rice, you'll be there. this is also something that they could do on your planet.
and it's a terrible measure for us; it depends on whether you like your rice hard or soft, how fast you walk... but it's good enough for a society that does not have to wake up at 7 am sharp to take the bus.

I am wondering now, with the suggestions, perhaps adulthood might be a measure of two factors; size and, as suggested, the onset of "puberty" (or whatever passes for it). The second would be the primary determining factor, but with the proviso that this is not generally assumed until a creature is of a specific size. (Assuming it does not have a very evident juvenile stage, like birds or something. I have not ruled it out; currently, the species in question is not even fully realised yet, all I have is the image that their lower half has a stance like a geranuk standing...)

Even if the planet is tide-locked, that only affects its own rotation; it continues orbiting around the star, and thus its view of more distant stars is constantly changing.

That will establish the planet’s year—but if that’s thousands of our years, then you’ll need another metric. If there are other planets in the system, their motions will help establishing a cycle.

Note also that a larger planet is likely to have a number of larger moons, and their motions would be complex but predictable, in the same way that we can measure the 4:2:1 resonance of orbital periods for the inner three Galilean satellites of Jupiter.

The planetary year is 1197.15 earth-years, for the record.

There are other planets - one of them being a gas gaint whose mass in resonance means that there is still some volcanitiy on the tidelocked planet.

But again, the problem is that most of the time, the sky is overcast with clouds (see below).

I’d be very interested in seeing more of this. My only sense of tidally locked planets is the born-of-a-red-dwarf variety, so I’m wondering how this is possible at +500 AU, or whatever distance you’re using.

Also, is there a real-world example you’re basing this on? And how is this planet warm enough to support vertebrate-analogue life?

Tide locking is, fundamentally, a function of angular momentum. Most tide-lcoked bodies are ones that are close to a larger bodt and are decelerated by the forces imparted by said body. But fi the body doesn't have much momentum itslef, it doesn't take as much to slow down. (And planets have different angular momentum, as day length is not actually related to orbit length, for example.) This particular world formed with a low angular momentum, and probabaly had that been lowered even more by an early stellar impact at exactly the right angle. Statistically *unlikely*, but no impossible.

The planet Andorliane, is sitauted 130AU out from (as mentioned above) plot-fied RCB variable star of 0.8sol mass and 96 sol in diameter. At that distance, taking into account the albedo effect of stabilising cloud feedback, the stellar flux is 2300W/m² (Earth's is 1360W/m², meanign a planet about an average of 3.9K warmer. (Though the temperature range will be different.)

As fot the climate, one particular paper I was pointed to suggested that clouds would stabilisie the temperture by increasing the albedo. Thus, you would have a permenant tropical storm on the substellar point (the closest to the sun), drawing in air at ground level towards it and then expelling cloulds in the upper atmosphere, where they would go over the rest of the planet and fall. There is a large (temperature stabilising) sea on the night side as well. So the climate would actually be very wet on the light side and progressively drier and darker as you moved towards the night side.

(And hense the cloud cover.)

Andorlaine is thus otherwise almost clone of Earth in other respects, because moving further outside that boundary would invalidate what I had to work with.




The more pressing questions are how to get the star to LAST stable long enough to have life forms, and with the specific star in question and the set-up, the answer was fundamentally "we-don't-know-ism..." The worst question came when, having done all the calcs, it came to "how does the stellar wind not blow the atmosphere off to which (not even being able to calculate stellar wind of anything, really having to shrug and go "it just doesn't, okay! There's like, magic particles or something!" I don't object to using that sort of explanation, but I prefer not to have to lean on it unless I absolutely have to and otherwise stick within the "plausible but unlikely" area if I can.)



Edit: TenLongFingers on the speculative evolution reddit suggested the genuious idea of using "babyfeedings" as the base unit of time, i.e. the approximate period between when the baby has to be fed (which is your "hour"). Combined with gestation time and weaning (which would be akin "year" or something), it strikes me as much better and elegant solid temporary basis to work from that, like crop growth times or "how long until the meat rots." It makes a great deal of sense, too, for a primitive society still largely in the hunter/gather stages to be focuessed on that, as well. It simply never occurred to me to use that as a metric, but if seems to fit the best of anything suggested so far!

[Sneak Dog]

It is not unlikely a tribe has a specific plant or mushroom it values, a multi-purpose one it relies on. So the growth cycle of such a thing would be a natural timekeeper, as they'd revolve their daily lives around them. Alternatively an animal. Perhaps a nomadic one, traveling to acquire all the necessary things they need for their complex metabolism. Specific minerals like salt, specific plants that create weird poisons these creatures need or whatnot.
(Cue confusion when meeting new people with a different way of life.)

[Palanan]

Originally Posted by Aotrs Commander
…but it turns out their planet has a stupid long eccentric orbit or something, and every so [however long], the climate changes and their biology adapts and they, like, change into crab people or something for the harsher "winter" conditions.

Have you read A Deepness in the Sky by Vernor Vinge? Fascinating look at a civilization that’s developed around a variable star that occasionally plunges the entire planet into an unlivable ice age. Apart from being a phoenomenal book, you might also get some ideas for your setting here.

Originally Posted by Aotrs Commander
As fot the climate, one particular paper I was pointed to suggested that clouds would stabilisie the temperture by increasing the albedo.

Not sure if I follow this part. Increasing albedo means increasing the proportion of energy reflected away, so less gets through to heat the planet. This is why glacial periods can lead to a positive feedback that ends in a Snowball Earth scenario.

Do you happen to have a citation for that paper, or a direct link?

Originally Posted by Aotrs Commander
There is a large (temperature stabilising) sea on the night side as well. So the climate would actually be very wet on the light side and progressively drier and darker as you moved towards the night side.

Depending on the extent and volume of that night-side sea, it might be a major factor in countering the drying trend. Here in the US we have what’s called lake-effect snow from our Great Lakes, and your night-side sea might end up doing something similar.

Originally Posted by Aotrs Commander
My intention was that they would be essentially a fishing village on the edge of a large inland lake/swamp bordered by mountains.

For timekeeping in this scenario, I think your best bet is to go with lunar tides. People living by the water’s edge are highly observant of and sensitive to any changes to the water’s edge, so even minimal tides would make for a noticeable cycle, especially if it’s the only constant cycle they have to work with. They would likely have different terms for high, low, and slack tides, and that would be the best external way of keeping track of time.

For longer periods, something like a “thousand-tide” could work as a measure roughly equivalent to a year (assuming for the moment they use base 10), with even longer periods reckoned in multiples of thousand-tides. Combining tides with measurements of the nearby gas giant and its moons, they might eventually develop something as complex and mathematically sophisticated as the Mayan long-count calendar.

Note also that our own moon raises six-inch tides in the continental crust, so if your Andorlaine sentients are especially sensitive to the earth beneath them, they might use similar land tides as an adjunct for water-tides.

[King of Nowhere]

This sounds highly suspect and likely apocryphal. Do you have a citation?

how the hell do you expect someone to remember the source of something like that? what are the chances that anyone could provide sources on such an internet debate?

But I do.
jared diamond, guns steel and germs.
i remember it because it's the only book on such a topic i ever read, and it was quite controversial in its thesis. i have no reason to doubt such an anecdote, though.
and frankly, what would be suspect about it? would you expect a tribe that never advanced past stone tools to use kilometers or something? even as late as the middle age people didn't care for precise time measurements. people set appointments at noon, or at dusk, and then somebody would arrive one hour before the others, or something (alessandro barbero, famous italian history communicator, of whom i listened to dozens of hours of conferences. don't ask me from which one comes this specific bit, though).

How do I track the usage and consumption of resources? As I said, it's fine to simply say "each tribesperson needs 1 food and 1 water per" but the problem now becomes how to determine what per what. Distance might be partly one answer, but then how do you measure it if they stop?

(Small stuff like durations of effects in rounds/minutes and such don't matter so much and I can just handwave them away as mechanical game effects, it;s the mid-and long-term units which are the problem.)

I am trying to avoid arbitatily assigning a "day" period "eats?", at least not without considerable thought. It might be necessary in the end, but dang it if I'm not trying to make an effort to give it as much investigation as possible beforehand.

it may be inevitable as an abstraction. still a realistic one; just because people eat when they are hungry and not when the sun sits high in the sky, it doesn't mean they'd eat a different amount of food overall.
oh, fun fact: the main reason to stockpile food and count it was to survive winter. in summer you get plenty of food, more than you can eat, but in winter there is less foood. so you have to stockpile food for the winter, and you have to invent math to judge if you can support your population.
but without winter, none of this applies. of course, you'll still want food stockpiles, but it's no longer critical for immediate survival.

(There is a gas giant in the system in resonance, which creates some volanicity, so everything isn't flat.)

ah, that's an astrophysics mistake, but one that can be easily fixed.
a gas giant would not cause gravitational heating unless it was really, really close to your planet. it would need for your planet to be orbiting the gas giant itself, and very close, for it to have a significant effect; jupiter has 0 effect on us, except when it intercepts asteroids. and in this case, your planet would not be tidally locked to the star. how could a moon of a planet always show the same face to the star?
however, there's no need for tidal heating to justify tectonic activity. you get that on any planet, until the nucleus cools down too much. you can keep tectonic activity without any interloping gas giant.

To whit: in addition to the very slow creeping shift of the day/night lines, every so often (and a semi-random interval), the star dims. (The idea is based on RCB variable stars, which change in brightness - not much change in the IR specturm, mostly just visible - but turned up to 11). So you have a world where civilisations develop and sometimes get quite far, and then are plunged into a literal dark age when the sun dims, leading to extinctions... Until the next time. But the periods are long enough that the successive lot generally doesn't even know it happened, basically. (Funnily enough, when nothign changes for a very long time, every tends to get fracked up when it changes rapidly.)

(Meaning a campaign world full of Stuff To Explore...)

nice idea, i like that

The more pressing questions are how to get the star to LAST stable long enough to have life forms,

that's my main issue. a star so big must be a blue supergiant, and those last only a few tens of millions of years. but this level of detail, i'm generally willing to handwave

and with the specific star in question and the set-up, the answer was fundamentally "we-don't-know-ism..." The worst question came when, having done all the calcs, it came to "how does the stellar wind not blow the atmosphere off

that's actually not the main problem. i'm not sure how strong the solar wind from such a star would be, but the planet is also extremely far from it. it's got to be a lot less strong by the time it reaches the planet. in fact, chances of habitability are better than around a red dwarf.

[Mastikator]

Anyone on the twilight region of a tidally locked planet will notice the stars rotating in the sky as the year goes on. People on earth noticed how the stars moved throughout the year and that was with a day/night cycle interfering, they did this thousands of years ago, many cultures did it independently.

So a rotation is still a year.

[Aotrs Commander]

I have had an unpresedented amount of people replying to the places I posted this up, which is quite shocking (normally in the past, I tend to find I get one or two, but today I can barely keep up, so forgive me if I don't respond to everyone and everything as exhaustively as I normally do. Like, I went out for an hour or an came back and I've been typing up stuff for the past nearly hour, hour-and-a-half! Frack, I wish the lore guff I put out for the main stuff I do got this kind of interest...! Or, like, ANY interest...)

Have you read A Deepness in the Sky by Vernor Vinge? Fascinating look at a civilization that’s developed around a variable star that occasionally plunges the entire planet into an unlivable ice age. Apart from being a phoenomenal book, you might also get some ideas for your setting here.

Yes, actually, and I'm pretty sure it (and the other one in Zones of Thought) were suggested in previous dips into this topic.

Not sure if I follow this part. Increasing albedo means increasing the proportion of energy reflected away, so less gets through to heat the planet. This is why glacial periods can lead to a positive feedback that ends in a Snowball Earth scenario.

Do you happen to have a citation for that paper, or a direct link?

how the hell do you expect someone to remember the source of something like that? what are the chances that anyone could provide sources on such an internet debate?

Acually...!

I do, because I can find the thread where it was suggested to me!

Link

Here is the thread (from 2014) which got the ball rolling, if you're interested.

It's stabilisation; the star throws out a frasck-ton of stellar flux (because is has a luminoisity of 18818.09909), so the high albedo is needed to keep the planet from entirely boiling off as much as freezing.



I am definitely thinking that the suggestion of using the tribe's own procrastion/maturity duration is the best first yardstick to use (especially since i can ball-park it from similar-sized creatures from Earth).

It has been observed that, for the most part, it's likely that there would be defined no cycles for life as such. However, that said, intelligent creatures might well still need a period of "sleep" or equivalent to get rid of the neurochemical build-up in the brain; so I'm leaning towards the intelligent life (or at least some of it) requiring some form of rest perdioically.

that's actually not the main problem. i'm not sure how strong the solar wind from such a star would be, but the planet is also extremely far from it. it's got to be a lot less strong by the time it reaches the planet. in fact, chances of habitability are better than around a red dwarf.

At the time, I could find no information of stellar wind strength to be able to make any kind of calculations to make an attempt, so I had no basis to even get that sort of information you've just given me.

[King of Nowhere]

At the time, I could find no information of stellar wind strength to be able to make any kind of calculations to make an attempt, so I had no basis to even get that sort of information you've just given me.

I don't know if we even know how strong is the solar wind around other stars. I mean, we certainly have experimental data only for our own. I'm sure we have mathematical models, but good luck knowing them unless one works in the field.
that star is a lot hotter and brighter than the sun. it's got to also have a much stronger solar wind. however, its planet is also a lot farther away, so that in the end it gets roughly the same light as our own. from a layman perspective, assuming that at that distance you also get a similar amount of solar wind makes sense.
plus, solar wind takes billions of years to strip away an atmosphere. well, no, ok, it depends on the planet, its magnetic field, and the strenght of the solar wind. anyway, the only major problem - one requiring handwaving - is that a star such as you describe would only burn for a few tens of millions of years, not enough time to get life - not enough time even to make a stable planetary system.

[Mechalich]

one requiring handwaving - is that a star such as you describe would only burn for a few tens of millions of years, not enough time to get life - not enough time even to make a stable planetary system.

I think a captured rogue planet would work. A supergiant is certainly capable of that feat, and it might even explain the weird scenario of such a distant planet in a tidally locked state. Such a planet could have life sustained in areas heated by radioactive decay and/or volcanic processes that massively expanded and got bigger quickly in response to a dramatic increase in temperature. Size is a fairly plastic trait in evolution, so assuming relevant precursors existed things can get big fast.


Regarding the time issue note that life on Earth does just fine in environments with constant conditions and no visible cycles, notably the abyssal zones of the oceans. Ecosystems can handle this scenario just fine. Sapient beings might struggle a bit more, but, of course, if environmental conditions are more or less constant there is far less urgency to everything, because events are either continuous (ex. marine snow rates) or random (ex. whalefalls), not cyclical, and therefore matching timing to exploit cyclical resources is unnecessary.

[Mutazoia]

[Duff]

Animals (including people) on this world are unlikely to have a sleep cycle, given sleep seems to have evolved mainly as a way to keep animals out of trouble when the light/temperature conditions are wrong for them (according to a New Scientist article I read years ago.
It has since been put to other uses such as assimilating memories etc and we need it now. But if there's no reason to develop a "shut down mode" then there's no reason to find a use for it.

And if there is no predictable seasons, as noted, there is no time for seasonal things to happen. That probably means plants that want to cross pollinate will always have some flowers and some fruit.
Animals will also not have a breeding season.
Though there is likely to be a level of "After it rains" or "when it's hot"

But maybe some strange animal develops a mysterious way to synchronise their cycle; such as detecting a galactic magnetic field.
This would be very strange. In a world where every day is very similar, for some reason suddenly all the turtleducks everywhere have babies.

So how do you measure time for rations?
I'd go the lunar week. I think the only other common time would be breaths. "I'm going to hide behind that tree. Count a hundred breaths, then chase the deer toward me"
Others might be used, but I think they'd be rare because it seems likely, as others have said, that the whole concept of time would be too abstract. But some that could be used are:
The length of time a single flower/fruit/leaf lasts. "When that individual fruit is ripe". "When a Flower that has opened today falls" The terms used would be based on the plants in the area.
There might be phenomena in specific places that also give a measure of time like "Old Faithful" the geyser in some places.

Maybe there's an island where there's a plant that flowers in the full moon and people there have "days" of the week. Bud day, Flower day, drop day (for when the flowers drop), swelling day, green day and ripe day. Maybe lots of plants do this. It wouldn't have to be the same flower doing everything in the 6 days. "Swell day" might simply be when the newest fruit start growing. But they might take a week or 5 to actually be the almost ripe ones on Green day. Or maybe they are small berries that really do cycle through that fast. These people who have a concept of time are considered weird by others

Tribes may migrate to avoid hunting/harvesting out an area, but the time to move on is "When the food runs low" rather than any specific time of year. Two neighboring groups that get along well might travel along the area where their territories border* in opposite directions to maximise the chance of meeting up. Maybe these meetings become the festivals, but they may never come up with the idea of trying to "synch up" because it's impossible. The whole concept isn't there.
Though, for example, a volcano that erupts reasonably often might be an event marker. "When The Mountain starts to smoke we gather in the far valley for a festival" might work. This could be variable. The bigger the smoke, the more tribes come

Geography wouldn't have the north south divide. The primary directions are "Sunward" and "Darkward". Then secondary directions might be "Left" and "Right" when you face the sun. Or Moonward and "Antimoonward".
Depending on whether the moon is orbiting in the same plane as the planet or at an angle, it will either define where the equator is or define a direction relative to the twilight ring. You walk with the moon or you walk opposite to it.

* Exact borders are a relatively new idea on earth. I don't see why this would be different

[VonKaiserstein]

Even in the absence of a light cycle, natural rhythms would evolve, though they may be driven by stimuli we don't understand. Look at your real world equivalents. Cave dwelling creatures develop activity/rest cycles, even if their eyes have become vestigial. These cave fish keep a 47 hour day. https://www.livescience.com/15923-bl...n-rhythms.html . Though much harder to study, I'd look at really deep sea creatures as well. Below a certain depth, conditions are relatively uniform at all times. There are others that have broken free of all of our terrestrial timekeeping- cicadas, and their emergence every 13 or 17 years. What stimuli caused that evolution?

For all of that- our own full night's sleep isn't really biologically motivated. In the absence of a clock, most humans will trend toward biphasic sleep- https://www.bbc.com/future/article/2...biphasic-sleep .

With neolithic hunter gatherers, I suspect you'll have a leader setting the pace for the tribe. Likely a horn or drum to awaken everyone and get them going. Other than cooperative tasks, there isn't nearly as much need in that sort of society to be 'on time' in the way we think of it. It's not like tribesmen are coming back to the village for lunch, or you can't just wake Joe up if you need to barter with him urgently for some reason. What would be the need for time in a neolithic culture? You have to eat, you have to find shelter, you have to do all the survival tasks, but does it matter if you do them in 5 days, or 7 days? There's a definite, and often fatal window of going too slowly about your tasks... but otherwise, you're just a hard worker who can have the chance to catch some more fish, or plant another row of crops, as opposed to your next hut neighbor who's just getting by and sleeps more.

[Palanan]

Originally Posted by Mechalich
Regarding the time issue note that life on Earth does just fine in environments with constant conditions and no visible cycles, notably the abyssal zones of the oceans.

We know so little about the deep pelagic regions that it’s unwise to make any sweeping claims about what might or might not be going on. As noted with the cave fish, organisms often have complex and unexpected cycles, and the deep pelagic regions are simply too poorly explored to say they don't have something similar. They may be uniformly dark with regards to sunlight, but they're not isolated and they're definitely not unchanging.

Originally Posted by VonKaiserstein
There are others that have broken free of all of our terrestrial timekeeping- cicadas, and their emergence every 13 or 17 years. What stimuli caused that evolution?

Periodical cicadas have not “broken free” of the annual cycle—in fact it’s the opposite, as their name itself will tell you. Their survival is dependent on their being precisely attuned to the passage of years.

It’s no accident that 13 and 17 are prime numbers, and the broods emerge on that schedule en masse to overwhelm their predators. Their emergences are staggered throughout their range, and the prime-number timing helps to prevent predators from evolving a similar pattern.

Most cicadas are not periodical, but they’re still closely tied to the seasons, and the species in a given area will have a reliable sequence of emergence, from late spring through late summer. This is most likely a form of niche partitioning. Whether annual or periodical, cicadas are an excellent example of a species group finely calibrated to the solar year.

Originally Posted by VonKaisterstein
With neolithic hunter gatherers, I suspect you'll have a leader setting the pace for the tribe. Likely a horn or drum to awaken everyone and get them going.

Any “leader” who tried that wouldn’t stay leader for long. People living close to the earth usually wake with the sun without much need for outside help. To say nothing of help from the rest of their environment when dawn arrives, from domesticated roosters to the entire dawn chorus of birds.

[Pauly]

This sounds highly suspect and likely apocryphal. Do you have a citation?

As a young pup growing up in the outback of Oz, we measured the distance between towns in “beers”. If a town was 6 beers away you could drink 6 beers on your way to it.

Citation: me

[Pauly]

A couple of people have mentioned sleep. Life on Earth has evolved to sleep, and sleep is an essential brain function, but it shouldn't be confused with rest, which is physical recuperation.
Organisms on Earth have evolved to sleep primarily at night or in the day depending on when it is safest for them to sleep.

In a tide locked situation there is no ‘safe’ time to sleep, so it is highly likely that organisms there don’t sleep as we do on Earth. Maybe they just don’t sleep at all, only rest when they’re tired. Maybe they sleep like dolphins, half a brain at a time, during which time they’re semi-dormant but capable of going fully active in an instant.

The basic timekeeping units in human history are days based on the Earth’s rotation, month based on the moon’s orbit and years based on the earth’s orbit around the sun. Seasons are not standardly measured across cultures/locations, but act as a subdivision of years, weeks are a subdivision of months and morning/midday/afternoon a subdivision of days.

There is a moon in the OP, but one that is not easily or reliably observable to the populace. In the absence of an easily observable effect it makes it difficult to see it becoming a basic time keeping unit.

For something ti become a basic time keeping unit it has to be reliably observable, constant, and widespread.
Some suggestions.
1) time it takes for a seed to sprout.
2) the time it takes to travel a standard distance, although that would start as a local measure of time which would then be standardized later by a civilization.
3) the time it takes to cook a basic food type. I’m thinking specifically of boiled rice which is cooked at a constant temperature.

[gbaji]

Not sure if others have commented fully on this (saw a couple points, but seemed to be going in a different direction. But I do have some questions about these bits:

So. Because the world is tide-locked, there is no day/night cycle and there are no seasons (the orbit cannot be erratic). So you can't measure time by the sun or the stars. In any case, as the plant remains largely habitable by the stabilising feedback of clould cover, the sky isn't always readily visible (and it's often raining). At ground level, there is a continuous stiff breeze coming from the dark side to the light side (again, part of the researched climatic conditons).

...

²Strictly speaking, it's ins't 100%, but the day length is also in thousands of Earth-years at a minimum.

To whit: in addition to the very slow creeping shift of the day/night lines, every so often (and a semi-random interval), the star dims. (The idea is based on RCB variable stars, which change in brightness - not much change in the IR specturm, mostly just visible - but turned up to 11). So you have a world where civilisations develop and sometimes get quite far, and then are plunged into a literal dark age when the sun dims, leading to extinctions... Until the next time. But the periods are long enough that the successive lot generally doesn't even know it happened, basically. (Funnily enough, when nothign changes for a very long time, every tends to get fracked up when it changes rapidly.)

You declared this to be "tidally locked", but it doesn't look like you are describing that. A tidally locked planet is "locked" with the exact same point on the planet pointing directly at whatever it is orbiting around (the star in this case). It has no day or night at all, with one side always facing the star, and the other side always facing away. In this situation, there is no movement of a day/night line at all (not even super slow), and no "constant wind" (because how does the air get back to the other side?).

What you seem to be descrbing is not that. You mention a "day" being thousands of years, and the "slow creeping shift of the day/night lines". This suggests that the planet is not actually tidally locked, but doesn't rotate at all. It's always oriented the same way relative to the stars outside the system, and therefore actually has a "day" that is the same period as an orbit around its star. So the inhabitants wouuld not see the stars change at all (always facing the same direction), but over time, the star would shift (but very slowly). I mean, you can refer to that as one rotation of the planet (from a stellar point of view), but it would not be seen as a "day" from the point of view of people living on it.

I'm not sure it's actually physically possible for a planet to maintain that sort of alignment (would assume it would either spin on its own, or gradually become locked, not just stay facing one direction like that). Planets form by spinning collections of stellar "bits", that due to gravity gradually must form and spin wherever there's an imbalance in matter distribution (do some research on formation of objects in an "almost perfectly evenly distributed mass cloud", and this is what has to happen). They will always have their own spin (and there's actually some formulas for determining what that spin would have to be based on the makeup of materials in the body itself). The spin will only ever stop if there's something else pulling it in a given direction. So a spinning top stops always leaning "down" towards the surface due to gravity. Same deal with planets/moons (any orbiting body). They should only ever "stop spinning" because of an imbalance in mass density on the planet itself which "stops" facing the body it's orbiting.

It should either spin much faster than that *or* always face the same side to the star. At least that's my understanding of the physics involved. The only thing that I can think of that would cause it to behave the way you are descrbing is some sort of gyroscopic effect, which I'm also scratching my head over because that requires spin too (and is what actually causes spining planets to maintain their axial angles).

[Lord Torath]

Further on that, the recently-captured moon will drag on the planet, causing it to spin. Don't suppose you've got What If by Randall Munroe? One of the questions is about what would happen if the Earth suddenly stopping rotating (day = year). The moon would slowly kick it back into gear. But we can pretend that it wouldn't since that's the set-up you want.

Anyone on the twilight region of a tidally locked planet will notice the stars rotating in the sky as the year goes on. People on earth noticed how the stars moved throughout the year and that was with a day/night cycle interfering, they did this thousands of years ago, many cultures did it independently.

So a rotation is still a year.

Well, keep in mind that a year is 1150-ish Earth Years, so roughly 23 paleolithic lifetimes (assuming a 50-year stone-age lifespan, which may or may not be accurate).


So first, we need clarification on whether the planet is tidally-locked to its star (regardless of the fact that it's too far away to be affected that way - tidal forces fall off at the rate of one over the distance cubed, so Earth feels 2.2 million times stronger tidal force from the sun than this planet would clear out at 130 AU), or whether it is... let's call it gyroscopically locked... with respect to the rest of the universe (it's probably not spinning nearly quickly enough to be a gyroscope, but I'm proceeding on the basis that your set up works for whatever reason). In either case, the stars/terminator would move much too slowly to be noticed in one person's lifetime.

I would expect most plants would be dependent on animals to spread their seeds. You might run into the situation in KungFu Panda, though, where the peach tree has both fruit and flowers on it at the same time.

Daily time/distances could be measured in "rests", since, as was mentioned above, people still need breaks from physical activity, even if they never actually sleep. As others have mentioned, shorter times might be measured by the life of quick-blooming flowers, or how long a decent-sized branch needs to burn down. I like the "breaths" as a unit of time as well.

If the moon is visible (and I'm not certain why it wouldn't be visible, if it's still 1/2 a degree across as viewed from the surface of the planet), then 6-earth-day Months would almost certainly be a thing. So distances could also be measured in months of travel.

People would probably measure their age in... Ages. The first Age might be when they're around 5-6 in Earth years, and are old enough to have made it through the various child-hood diseases/predators that might regularly claim the young. Second Age might be puberty. Third Age when they've hit full growth. Fourth Age when they're no longer fertile and/or vision starts going. Fifth Age when their teeth are worn down.
There might be earlier ages based on walking/weaning, I don't know.

Regarding the solar wind, it'll be about 16,900 times weaker than it would be at 1 AU, since it drops off by one over the distance squared.

Radioactive elements in the crust, mantel and core will keep plate tectonics going, as well as providing a magnetic field to protect against solar wind/cosmic rays. Of course, if the core is rotating, that would tend to impart a rotation to the rest of the planet, which could conceivably be balanced by the moon if the moon is rotating in the opposite direction.

[gbaji]

I suppose we could speculate that this is a universe not bound by Newtonian physics, but actually has some sort of "clockwork heavens" system in place. The planet is actually stuck in a band of "ether", and is held in place, moving along its path, but always facing the same direction (relative to an external POV). All other objects are as well.

You could make it work, of course, but it would not follow the rules of orbital bodies. Doesn't need to though!

[Palanan]

Originally Posted by Aotrs Commander
There are other planets - one of them being a gas gaint whose mass in resonance means that there is still some [volcanism] on the tidelocked planet.

Not sure if this will be feasible. In order for the gas giant to have enough of an effect to contribute to heating, it’ll need to be close—close enough that it will likely perturb Andorlaine’s orbit. But if Andorlaine has a thousand-year orbit, then the gas giant will only swing by on roughly the same timeframe. (If it orbits faster, then it’ll be closer to the star and won’t have any appreciable effect.)

In our system, Io is so volcanic because it’s being constantly pulled and counterpulled. But if Andorlaine’s jovian neighbor only comes by roughly once a thousand years, that’s nearly a thousand years for the crust to cool off between visits. I can’t see that having any significant heating effect.

Originally Posted by Duff
…I think the only other common time would be breaths. "I'm going to hide behind that tree. Count a hundred breaths, then chase the deer toward me"

If Aotrs doesn’t want to work with tides, then this is probably the easiest and most natural way to go for the building blocks of time measurement.

—Assuming that these sapients breathe the way we do, and don’t use qorii-tendrils to pull oxygen from their llyrx-pouches.

Originally Posted by gbaji
I mean, you can refer to that as one rotation of the planet (from a stellar point of view), but it would not be seen as a "day" from the point of view of people living on it.

This is something like the situation on Mercury, where the “day” is longer than the orbital period. On Mercury this causes some rather unusual sunrises and sunsets, with the sun pausing and reversing before reversing itself again.

What this seems to mean for Andorlaine is that over centuries or millennia, the former dayside will eventually become the nightside, and slowly back again. That right there could give you a slow rise and fall of civilizations, since cultures that develop around specific resources or geophysical features would eventually need to migrate when those resources and features went through the twilight band into the opposite side.

I could see the evolution of two sharply different realms of flora and fauna, each adapted for either dayside or nightside conditions. As the planet slowly turns, biomes adapted for the dayside would need to find some way of ensuring that their propagules could survive a long passage through the nightside—while at the same time, long-dormant seeds and eggs of nightside biota would be reawakening after thousands of years of quiescence during dayside conditions.

Originally Posted by Lord Torath
…as well as providing a magnetic field to protect against solar wind/cosmic rays. Of course, if the core is rotating, that would tend to impart a rotation to the rest of the planet….

This is a real kicker. You need a spinning molten core to generate the magnetic field, which prevents your atmo from sputtering away and thus prevents your oceans from evaporating off. But the spinning core will have an effect on your planet’s overall spin, and I’m not sure if the moon can counteract that.

Originally Posted by Aotrs Commander
There is a planet. It orbits around a large star whose goldilocks zone is significantly far from the star that the orbit is measured in thousands of Earth-years¹. The planet is tide-locked².

…Because the world is tide-locked, there is no day/night cycle and there are no seasons (the orbit cannot be erratic).

Given the issues with the not-quite-tidal-lock, the long-duration “day” and the complex impacts on biota and cultures, plus many of the other things mentioned here, what about your underlying concept is most important to you?

A world with a thousand-year orbital period is a great concept; a tidally locked world is another one. But combining the two is proving to be a real bear, and I have to wonder if it’s this combination which is central to your concept, or if there’s some other way to approach what you’re interested in.

[Mechalich]

A world with a thousand-year orbital period is a great concept; a tidally locked world is another one. But combining the two is proving to be a real bear, and I have to wonder if it’s this combination which is central to your concept, or if there’s some other way to approach what you’re interested in.

A better combination is probably a planet like Uranus. It has a long orbital period and because of its extreme axial tilt, the poles face either toward or away from the sun and experience half the orbital period as continual light and half as continual darkness. Assuming a 1000 year orbital period, that would be 500 years, which is probably long enough.

This would also eliminate the timekeeping issue, because the planet is still rotating in reasonably rapid fashion that could be measured against the starfield or any moons, it simply wouldn't influence the day/night cycle.

[Duff]

I'm not sure it's actually physically possible for a planet to maintain that sort of alignment

It could be in the late stages of becoming tidally locked.

Or, I think it would be possible for the newly arrived moon to have just slightly "unlocked" it

And a suggestion for keeping tabs on rations.
For game purposes, have a standard food bag.
A bag of food is both an amount of food, and the time it takes to consume it. You could call them days if you want.

You have 6 bags of food in the warehouse. You harvest 5 bags from the potato field in the time it takes for 1 person to eat a bag of food. It takes 5 people to run the potato field.
The potato field just breaks even on food
If it takes 7 footbags of time to improve the potato field, the community is going to need to build better reserves

[GuzWaatensen]

Hi that’s quite an interesting discussion and I just want to throw a couple of points into the arena for your consideration.

1. As others have pointed out an aeon-orbit tidal locked planet doesn’t make a lot of sense based on our current (admittedly limited) understanding of exoplanets. As the tidal lock itself already removes the day night cycle I don’t know why the long orbital period is necessary to your setup. A tidally locked planet much closer to the sun could be just as interesting. You‘ll always have to explain why there‘s an atmosphere either way, if you want to not just hand wave it of course.

2. How life would measure time is an interesting conundrum. I disagree with some of the statements that this might be irrelevant, there’s likely always a need to coordinate cycles between different plant and animal life. This could of course be done through other means than celestial time givers. One interesting proposal could be a large macroorganism spanning almost the entire habitable side beneath the surface. It’s bodily functions could cause periodic tremors, eruptions or other phenomena that act as time giver for other lifeforms to base their cycles on.
And such an organism would add a third interesting trope into your fantasy world…

[Palanan]

Originally Posted by Mechalich
A better combination is probably a planet like Uranus. It has a long orbital period and because of its extreme axial tilt, the poles face either toward or away from the sun and experience half the orbital period as continual light and half as continual darkness. Assuming a 1000 year orbital period, that would be 500 years, which is probably long enough.

This would also eliminate the timekeeping issue, because the planet is still rotating in reasonably rapid fashion that could be measured against the starfield or any moons, it simply wouldn't influence the day/night cycle.

This is a good fix and could make for a really interesting setting, if applied to a terran or superterran world. Between the rotation and the potential for moons the timekeeping issue would be taken care of, and there’s plenty else to work with in the dynamics.

There’s still the issue of the inverse-square reduction in stellar output over distance, which makes it trickier to justify the extreme orbital period, but there are plenty of ways to approach that, including simply using a brighter star.

Originally Posted by GuzWaatensen
I disagree with some of the statements that this might be irrelevant, there’s likely always a need to coordinate cycles between different plant and animal life.

Very much agreed, I’d been meaning to comment on this point earlier.

Even in a setting without obvious natural cycles, species wouldn’t be likely to exist in some sort of unhurried stasis or otherwise be able to ignore time, because predation pressure will be a constant and that will drive the evolution of form and behavior. Reproducing at a constant low rate will only spoon-feed the predators unless there’s some other set of defenses involved. As with the periodical cicadas, some species might evolve mass reproduction to overwhelm predators and ensure that at least some progeny will survive.

And of course, the more complex the ecosystems the more complex the interactions and their timing. Note also that seeds have predators as surely as anything else, even if we tend to gloss over the distinction with general terms like “herbivores.” This means that seed predators will be exerting strong selective effects on the species they’re targeting.

Originally Posted by GuzWaatensen
One interesting proposal could be a large macroorganism spanning almost the entire habitable side beneath the surface.

This reminds me of the Amoebic Sea from Wayne Barlowe’s original Expedition. But whether surface or subsurface, the metabolism of a planetary organism could contribute significantly to local temperatures, which might help offset some of the issues from a wide orbit.

[Chronos]

I think you're going about it backwards. It's not "how many units of food do you eat in a day"; rather, they'd take some standard unit of food, and measure day-ish timespans by how many of those standard units you eat. Age wouldn't be measured in years, but in milestones. Even today, in some parts of the world where record-keeping isn't so great, people measure when a child is old enough to start school by the relative sizes of their arms and head: When you can reach over the top of your head to touch the ear on the opposite side, you're old enough. You wouldn't say "I'll be gone on this journey for over a decade"; you'd say "By the time I return, this newborn will have grown enough to have gone on his first hunt".

[gbaji]

A better combination is probably a planet like Uranus. It has a long orbital period and because of its extreme axial tilt, the poles face either toward or away from the sun and experience half the orbital period as continual light and half as continual darkness. Assuming a 1000 year orbital period, that would be 500 years, which is probably long enough.

I really like this idea. Allows for a more "normal" rotating planet (which eliminates some of the issues with air/wind), while retaining the "very very long day" concept. Unless, of course, the entire point is to have a planet with no (or very little) motions which would cause normal cycles to occur.

It could be in the late stages of becoming tidally locked.

Or, I think it would be possible for the newly arrived moon to have just slightly "unlocked" it

Yeah. Either could work. Another thing to remember is that orbital objects that have any influence on eachother gravitationally cannot have a stable orbital rate that is an exact multiple or factor of any other orbital object (the regular cycle will push/pull one or both slightly out of sync over time, or result in massive shifts throwing one of them off in a different direction). May not be relevant at all to people living on the planet and the presumed scale of any game setting you may choose to deposit there in a relevant time frame though (actually probably not).

The "recently arrived moon" concept is interesting, since we could assume a world that was much less vibrant/active (life form wise anyway) prior to its arrival (and "recent" in astrophysics terms can be 10s of millions of years or longer). Said moon could have actually kickstarted growth of more advanced life forms just as a result of "shaking things up". Could create some interesting cosmology angles there, depending on what kind of setting you are going for.

2. How life would measure time is an interesting conundrum. I disagree with some of the statements that this might be irrelevant, there’s likely always a need to coordinate cycles between different plant and animal life. This could of course be done through other means than celestial time givers. One interesting proposal could be a large macroorganism spanning almost the entire habitable side beneath the surface. It’s bodily functions could cause periodic tremors, eruptions or other phenomena that act as time giver for other lifeforms to base their cycles on.
And such an organism would add a third interesting trope into your fantasy world…

And also this. If you want to go all the way with "there's no planetary/tidal/seasonal time" bits, creating some sort of life that makes it own time in some way seems like a great idea as well. Some large macroorganism that manages this, perhaps on a planetary basis, and thus provides life cycling to all other creatures can also create a great backdrop depending on what setting is chosen (and frankly can support any number of them). Think like Pandora if you want, or something like that, but perhaps without the unobtainium (or maybe with it?). Could create a lot of interesting concepts.


if you do go with "extremely long day", one thing to consider is the concept that everything just moves along with the terminator. If we're talking around 1000 years for a single cycle, this is quite manageable, and could represent the concept that this one area would always be where life could survive easiest/best. People could form into nomadic tribes, who have travelled various routes (always going "east" or whatever), picking up every year or so and moving to the next valley. It could also provide an interesting game setting, since, assuming humans (or whatever) have been around for quite some time, there's the potential for building structures over time as well, and then settling and resettling into the same structures over and over as they move. And the potential for discovery. So maybe our humans are traveling along, as they always have through their history and come across something "different". Maybe a thousand years ago, their great ancestors developed more technology/magic/whatever, and now they're rediscovering that as they come across the long abandoned ruins of the last time they were there. Maybe some people tried to stay through the long night. What happened to them? Maybe other "things" are left from that age as well, which maybe ought not to re-awaken...

[Aotrs Commander]

You declared this to be "tidally locked", but it doesn't look like you are describing that. A tidally locked planet is "locked" with the exact same point on the planet pointing directly at whatever it is orbiting around (the star in this case). It has no day or night at all, with one side always facing the star, and the other side always facing away. In this situation, there is no movement of a day/night line at all (not even super slow), and no "constant wind" (because how does the air get back to the other side?).

According to the research, the substellar point forms a permanent storm, which heats the air and blows it out in the upper atmosphere (creating the semi-permenant cloud-cover), while drawing in the colder air at ground level (from the night side), in a giant atmosphere cell.

What you seem to be descrbing is not that. You mention a "day" being thousands of years, and the "slow creeping shift of the day/night lines". This suggests that the planet is not actually tidally locked, but doesn't rotate at all. It's always oriented the same way relative to the stars outside the system, and therefore actually has a "day" that is the same period as an orbit around its star. So the inhabitants wouuld not see the stars change at all (always facing the same direction), but over time, the star would shift (but very slowly). I mean, you can refer to that as one rotation of the planet (from a stellar point of view), but it would not be seen as a "day" from the point of view of people living on it.

The difference between 100% tide-locked and "maybe moves a fraction of a millimetre every few centuries" is largely academic, I feel.

Given even the (relatively limited) force the moon exerts, it would be logically impossible for Andorlaine to be 100% tide-locked... But the acceleration is so tiny as to be laregly unnoticable. Andorlaine is tidelocked bar the shouting.

For reference, my orignal look at it.

In short, the day length increase from acceleration from the moon is likely to be on the order on about 1 millisecond every century, assuming tidal forces equal to Luna on Earth. To get up from stationary to a sidereal day of 24 hours from a completely tide-locked planet would take three trillion years - well past the point the recent-capture moon either crashed into the planet or sods off into the void in mere few million years. (It is wasn't the moon would have been discarded.)

So, as a ball park figure, speed of earth's surafce at the equator over 24 hours is 460m/s. Proportionally, after a century of acceleration from an assumed complete stop, that gives us a speed of an approximate speed that would be 1/(24 x 60 x 60 x 1000)th of that, or 0.000005324m/s (i.e. 0.005mm/s). So the rotational speed will be increasing by an estimated 1mm every 20000 years. On a geological and civilisation scale, I think that's small enough to effectively not be a major concern, considering actual plate tectonics will be faster.

I'm not sure it's actually physically possible for a planet to maintain that sort of alignment (would assume it would either spin on its own, or gradually become locked, not just stay facing one direction like that). Planets form by spinning collections of stellar "bits", that due to gravity gradually must form and spin wherever there's an imbalance in matter distribution (do some research on formation of objects in an "almost perfectly evenly distributed mass cloud", and this is what has to happen). They will always have their own spin (and there's actually some formulas for determining what that spin would have to be based on the makeup of materials in the body itself). The spin will only ever stop if there's something else pulling it in a given direction. So a spinning top stops always leaning "down" towards the surface due to gravity. Same deal with planets/moons (any orbiting body). They should only ever "stop spinning" because of an imbalance in mass density on the planet itself which "stops" facing the body it's orbiting.

It should either spin much faster than that *or* always face the same side to the star. At least that's my understanding of the physics involved. The only thing that I can think of that would cause it to behave the way you are descrbing is some sort of gyroscopic effect, which I'm also scratching my head over because that requires spin too (and is what actually causes spining planets to maintain their axial angles).

Again, from the gentleman of the physics forum thread:

The thing is, the amount of angular momentum a planetary body ends up with after most of the protoplanetary debris had been cleared during the formation of the system can be almost anything, especially for smaller bodies(i.e., not gas giants). So you could conceivably have a planet that never really had much of angular momentum to shed, so it eventually did get tidally locked to the distant star, especially if given a lot of time.

I am not an astrophysicist myself, so I can only go with what people who actually know what the maths are tell me.

So, low natural angular momentum, followed by an early collision that hit exactly right to slow the rotation further is the assumed reason.

(It's actually 105 AU, not 130, that was me mis-remembering, not that it significantly makes a difference.)

Not sure if this will be feasible. In order for the gas giant to have enough of an effect to contribute to heating, it’ll need to be close—close enough that it will likely perturb Andorlaine’s orbit. But if Andorlaine has a thousand-year orbit, then the gas giant will only swing by on roughly the same timeframe. (If it orbits faster, then it’ll be closer to the star and won’t have any appreciable effect.)

In our system, Io is so volcanic because it’s being constantly pulled and counterpulled. But if Andorlaine’s jovian neighbor only comes by roughly once a thousand years, that’s nearly a thousand years for the crust to cool off between visits. I can’t see that having any significant heating effect.

On the one hand, going with what I was told and the gentleman was clearly thinking of Io's tidal heating.

On the other hand, a quick google search of the topic indicated that actually, Earth's volancity is powered primarily by isotope decay, residual formation heat and frictinal heating, so, actually, there's nothing stopping Andorliane having an active mantle at all (it is not significantly older than Earth), though it's fair to say the effect might be less that Earth's; but ti would still have plate tectonics.

This is a real kicker. You need a spinning molten core to generate the magnetic field, which prevents your atmo from sputtering away and thus prevents your oceans from evaporating off. But the spinning core will have an effect on your planet’s overall spin, and I’m not sure if the moon can counteract that.

I did look at that, and decided it was simply unworkable. Without being able to even ballpark the stellar wind (which as noted we don't even understand), I did resort of hand-wavium at that point. (As with "how has the star that should only last a few million years doing what it does lasted a few billion plus?")

(Still, whatever else, you cannot say I did not give this whole an absurd amount of consideration, compared to what most sane people would do.)

Given the issues with the not-quite-tidal-lock, the long-duration “day” and the complex impacts on biota and cultures, plus many of the other things mentioned here, what about your underlying concept is most important to you?

A world with a thousand-year orbital period is a great concept; a tidally locked world is another one. But combining the two is proving to be a real bear, and I have to wonder if it’s this combination which is central to your concept, or if there’s some other way to approach what you’re interested in.

It is, yes, in combination with the whole "the sun goes dim" thing. The changes happen, but belong the lifetime of civilisations.



(It's also worth noting that this is within the same universe which was retrocasually probability engineered to the point of duplicate planets appearing, so extremely implausible but statistically possible events¹ (like the low momentum of Andorlaine) are by comparison, potential run-off.)



¹By comparison, in Rolemaster a hobbit with a bent knife could theorhetically beat Morgoth in single combat, the but the probability makes it impossible on a practical level.

[Lord Torath]

How about a large cloud of dust that is at, say, 85-ish AU in a resonant orbit, and it blocks out the sun every couple-thousand years? Maybe a planet that was recently (a few million years ago) pulverized by a rogue planet from outside the system? I'm just spitballing here, so I don't know how much mass the cloud would need to block out the sun from 20 AU away, nor how long it would take to coalesce back into something that would no longer block the sun. It might not work out. On the other hand, from 105 AU, our sun is little more than a bright star in a background of dimmer stars. It's practically a pin-point as opposed to a circle. So it might not take an absurdly huge cloud to dim it, assuming the cloud and Andorlaine both orbit on the same plane.