Effects of an extended day/night cycle

[Xeviat]

A few things I think I can add. First off, I'm very impressed with the blend of fantasy and science fiction you seem to be going for. Although you're going in a very different direction than my setting, your quest for believability and a level of realism is similar.

Second off, I wouldn't worry about things being 100% accurate, just believable. An article from the D&D 4E designers brought up the issue of believability, and I've taken it as my mantle. IFM (It's F'en Magic) works to an extent, especially in big situations. There's a quote from someone about how people fall prey to a big lie more than a small one: just think about the way people believed the world worked in the past.

So here are some topics that I think are of importance:

Time: During the day, time is going to be measured by the position of the sun. I would have the main sentient race have an architectual tradition where there are many angles and beams in roof work, so people can use them as reference points. Clock towers could be tall towers with markers on them; to tell the time, you stand along the tower's shadow and look up at where the sun is. Even more simplistically, these clock towers could have courtyards around them with accurate times carved or tiled into the groundwork, showing specifics. I'd say that each "Day" would have 3 "weeks"; morning, noon, and evening, splitting the sky into thirds. Aside from the accurate clock towers (which I think should be infront of churches; the world is definately going to revere the sun and I believe the most powerful god has to be the Sun deity, though this depends on how your world's spiritual system works).

As for time at night, you could use the rings. They're going to be visible from all parts of the world except very close to the poles (but that's fine as I don't think the poles would be very habitable). I recommend having large objects in the rings (Saturn has protomoons and moons in its rings if I remember correctly). The ring would have its own rotational period, and I think this period should exist to help show the passing of "days". I also agree with the idea of a "glow in the dark" ring; then the level of light in the ring would determine the passage of time (though this would be harder to actually mark). I believe the ring has to rotate faster than the planet, though, for it to not fall in; I'm not certain though.

With the storms that would come with dawn and sunset, I think the Night should be represented by malevolent deity.

Plants: I don't think true plants would exist. I can see your world's plants being a fungus/plant mixture, using photosynthesis in the day to store sugars and feeding off those sugars in the night. With a half-month long day, I believe these plants would be able to store up considerable amounts of energy. But in addition to that, they would need to draw on energy from the soil as well.

I'm imagining the day having forests filled with broad leafed plants. As night falls, these plants soak up the water from the storms, their trunks and roots filling. They could even produce fruit at this time, which would provide food for creatures in the night and ensure dispersion of their seeds. When night falls, the plants would move all the water out of their leaves, causing them to shrink up. The plant would then feed off its sugar and water stores.

Additionally, as night falls the spores from nocturnal fungi would recieve enough water from the storms to grow. The forest would then be alive with massive mushrooms. I could see your world's trees actually being a communal relationship between a type of plant and a type of fungus, each providing each other during their lean times (there are many creatures on earth that do this). But it might be more fantastic to just splice them into the same organism.

I do like the idea of green plants in the day and mushrooms at night. Oh, and since the angle of the sun's rays doesn't change much, it might be possible and advantageous for plants to change color as the sun moves, one color for morning and evening when the sun is heavily angled, and one for noon when it is more straight on.

Races: First off, are you building this setting primarily for stories or for gaming? If you're building it for gaming, you're definately going to need a simply statted race with customization ("humans"). If you're building it for stories, you're going to want a race that people can easily identify with. I could be wrong, and I'm sure there are ways to get around this, but it just seems likely.

In another thread you said that sentience wasn't going to be evolutionary, that it is a gift from the gods. It seems that cold blooded creatures would either need to hybernate in the night or just wouldn't exist. Again, I'm not sure, so I'm just going off what makes sense to me (most of your readers or players are going to be reasonably clever; few are going to be experts in these fields).

I hope that something I said gets you thinking. Keep it coming, I definately have my eye on your work. If you are working on an RPG world, come to me if you need anything crunchy worked on.

[Nomadic]

Both Snarg and the Kapn' speak wise truths, listen and you will learn much (though ignore the Kapn's Freudian, slip funny as it was; cock towers... heh). In regards to the ring though...

Planetary rotation has little effect on whether a ring stays up, it's all gravity. The ring particles must maintain proper velocity in order to stay in an orbital pattern as close to 0 eccentricity as possible (they have to maintain a perigee that is higher than the atmosphere proper). However as this planet is rotating only once a month geosynchronous orbit isn't going to happen without crashing and burning (unless the planet is many magnitudes larger than earth and it's lighter gravity means it is in fact smaller). However that doesn't rule out telling time with them. They still have to rotate into the night side and depending on chemical makeup could indeed lose enough energy in that time to begin dimming as they approached the morning horizon.

Anyhow though, remember mister moonclaw's words. Verisimilitude always takes precedence over verifiable realism. Make things too complex and you will lose your players/readers. So listen to everything everyone has to say as it has real merit, but don't take things too far. Heh, you have to be really careful around me for that reason, I love all forms of science and real life simulation... so I sometimes forget that what's being designed is a game/story world... not a replica of reality.

Regardless though, best of luck. I will keep checking in and chucking in my two cents worth from time to time. Take or leave ideas as you desire. ;)

[Snargash Moonclaw]

After I got home something occurred to me re: the ring(s) - they could also be a living organism - plant or fungus like, perhaps interwoven vine strands, which would store solar energy and release it when it passes into the shadow. Sentience would be an interesting option to explore as well. If it has other beneficial effects upon the planet and/or its atmosphere this could in fact be the body of an unusual preserving deity.

To expand on the Solar/Night deity idea - that would be pretty Zoroastrian in flavor I think - such a deity would fit in well as a mitigating (or "neutral") entity. A different way to approach the dichotomy which might also be interesting would be to have both deities display different aspects - kind of like the Rada and Petro rites of Vodoun. The latter half of the day might well be oppressively hot and bright and the latter part of the night excessively cold and darker as the ring fades. Dawn and dusk would likewise have both positive and negative faces since they herald relief from either extreme but are also (perhaps even destructively) tempestuous. The ring could in a sense be the force that maintains the balance between the aspects of the other deities. They aren't exactly good/evil personalities, rather gentle and forceful - too much of either is detrimental.

Ring rotation that Kap'n mentions (re: it staying in orbit) would depend on how far from the planet it is and, of course, mass. If it's particulate it can be closer and slower than if it's solid since gravity is affecting the mass of each particle separately so it doesn't have to move as fast or as far out. The further away it is the slower it has to move to keep from breaking out of orbit. If it's solid however it could conceivably not have to rotate at all - it's own structural integrity prevents collapse into the planet. Gravity pulls on the whole thing equally and acts to make it stronger - much like the weight of a bridge structure pushing down on the supporting arches and making them even stronger.

Kap'n has made some good suggestions. (By the way Kap'n, I'm afraid you are quoting Hitler regarding one big vs. many small lies. . .) The menhir style clock towers'/giant sundials idea would work pretty well as long as you have no "wobbles" (Surviving remnants of such produced by ancient Earth cultures are no longer entirely accurate - recalibration is required  - but that is the result of many centuries' slight variations.) Another thing you could do based on his suggestion of plants changing color is to use that effect to tell time. Floral clocks were attempted in the 19th century using species of flowers which open at different times of the day. None have ever really been practical as time keeping, though it can make a garden constantly change through the day. Having species on your world that change in a variety of ways at different times can be as accurate (or not) as you wish. Night plants could likewise demonstrate visible changes through the course of the night, or timekeeping could occur by tracking temperature variance - a night that long would probably show a steady drop (even if remaining in a comfort zone throughout) which could be measured.

A couple of decent references that I've found helpful are the World Builder's Guidebook (old 2nd ed. pub. from 96 - not system specific tho and still available via Amazon. This is especially useful for mapping - comes with a number of blank map formats. Also the free excerpt from Expeditious Retreat Press' A Magical Society: Ecology and Culture, A Magical Society: Guide to Mapping. The City Guide is also excellent - I've been finding it very helpful (along with the city section of World Builder's . . .) in developing Salis Freeport. I haven't picked up the two books they're taken from but may well end up doing so.

Example maps from WBG:

[Xeviat]

Hah, wow, that's a typo. Thanks for pointing it out Nomadic; I blame it on my pain killers.

[Nomadic]

Ring rotation that Kap'n mentions (re: it staying in orbit) would depend on how far from the planet it is...

http://www.traipse.com/earth_and_moon/earth_and_moon.gif[/img]

Of course remember that as long as it seems realistic the old "a wizard did it" is perfectly fine. Anyhow I will stop babbling on.

[Pellanor]

Wow, lot's of great replies over the weekend.
I'll start by trying to answer a number of the questions that I've seen pop up.

I just want to be sure I understand the statement correctly as meaning the time span of a single axial rotation; from sunrise to sunrise = 24 x (28 to 30) hours with 24 x 12,13 hours daylight and equal night?
That sounds about right.

Next - how long is a year in strict terms of planetary orbit around the sun?
As long as it needs to be. Since there's very little planetary tilt the "year" will have next to no affect on game play. I'll just end up figuring this number out at the end as a bit of "trivia", based on whatever other requirments we need.

By "thick atmosphere" are you referring to atmospheric depth? Or do you mean gases of greater density?
Hmmm... I'm not totally sure. You know how the air is "thinner" up at the top of Mt Everest compared to sea level? Well I want the air at sea level in my game to be that same amount of difference again.
ie.
Everest: 0.3 atm
Sea Level: 1 atm
Sea level my planet: 3.4 atm

So this could be made up in part by having greater atmospheric depth or greater density, or a bit of both.
The mainreason I'm looking for the thicker atmosphere is to make flight easier, and allow more oxygen for cool stuff to evolve.

Or are you referring to denser cloud cover?
This world will likely end up with thicker cloud cover as well. It'll be less massive, so probably closer to the sun than earth. I think that the denser cloud cover should help to reflect some of the light, and insulate the planet at the same time.

In all of the above one major influence will be how much of the planet's surface is covered with water.
The planet will likely be apx 50-60% water, though with less huge ocean and much more small scattered seas.

First off, are you building this setting primarily for stories or for gaming?
Gaming. The human-like race that's easy to play is something I'm keeping in mind.

Anyway, I'm going to do some work putting together a bit of a summary of what I like best, and areas where I think we still need more work. I'll post it later today (hopefully).

[Pellanor]

Planet Details
Name: ??? (I hate coming up with names. Any suggestions?)

Mass: 57.6% that of earth [3.4408×10^24]
Size (radius): 80% that of earth. [5,096 km]
Density: 112.5% that of earth. [6.205 gm/cm^3]
Gravity: 90% that of earth. [8.83 m/s^2](feel free to double check my math)
Sidereal rotation period: 3278.9% that of earth [32.7 d]
Equatorial rotation velocity: 2.5% that of earth [11.33m/s]
Surface pressure: 340% that of earth [344.42 kPa]
Surface area covered by water: 60%

Albedo: ?

Surface temp in Kelvin:
   min: ?
   mean: 10 K warmer than earth (297 K)
   max: ?

Celestial Properties
No moons.
Large rings around the center of the planet shade the equator and provide illumination at night. Likely phosphorescent and possibly magical in origin.

Geology
I have no idea what the make up of the planet should be. Probably fairly similar to earth, with a large molten iron core.
Since it is more dense, I'll probably introduce some more "heavy metals" like adamentine, and other such fun fantasy stuffs.

Topography
Since there are no tectonic plates the topography is very different than that of earth.

The surface is relatively flat, with fewer great mountain peaks and ocean depths.
3% - Mountain peaks > 2000m above sea level.
12% - Highland plateaus 500m to 2000m above sea level (3-4 "mini continents").
25% - Archipelagos less than 500m above sea level.
15% - Shallow seas of depth <= 200m
20% - Ocean of depth 200m to 500m
20% - Ocean of depth 500m to 1000m
5% - Ocean of depth > 1000m

Climate
There are a few major climate belts.

The Equator is a fairly small region in continual shade due to the rings. This causes the average temperature to be slightly cooler during the day then the neighbouring tropical belts. Also being directly under the rings this area is the best illuminated at night, providing the least change from day to night of any of the climate zones, outside of the poles. Most life in this region is adapted to the low light, with few plants relying on Photosynthesis.

The tropics are the areas near the Equator that are not shaded by the rings. These are the hottest parts of the world, which receive the most sunlight during the day and a large amount of illumination during the night.
Tropic Archipelagos are typically rain forests which have evolved to absorb the most sunlight during the day, and rain at night. These broad leaf trees can reach heights much greater than those found on earth.

I'm not really sure what the other climate areas would be like... I like the idea Cloud forests along with some highland Savanna, though I'm not sure how those would work with the geology.

Flora
Mycorrhiza will be very important in sustaining plant life.
It looks like most forests would be Broad Leaf during the day and Fungi at night.

How would Plains and Savanna work here? I think we could certainly find plenty of grasses, since they can grow in practically any climate. Also since they often grow in areas with only occasional rainy seasons, or in areas where they spend months buried under snow, they should be able to adapt fine to the longer day/night cycle.

I think a lot of the flora would have to grow in spurts as well. I imagine there could be a lot of really cool flowers that follow the sun and what not.

I also need to think of what could grow in Water. The Coral Reefs might be too sensitive to temperature change (A rise in temperature of 1-2 degrees Celsius for 5-10 weeks or a decline in temperature of 3-5 degrees Celsius for 5-10 days has resulted in a coral bleaching event. source) to do well, which is disappointing.

Fauna
There's going to be a wide variety of animal life on this world.

Any Cold-Blooded creatures are going to be on a very short lifespan cycle, probably only ever living for a single day. They will be born with the warmth of dawn, and lay their eggs as the sun sets, and die out during the cold of night. Hmm... I wonder if it would be possible to have these guys go the entire day without sleeping, and how big they would be able to get. They could be a rather entertaining pest if there's enough of them and they can grow big enough.

Warm-Blooded creatures will need to be able to feed both during the day and at night, or be able to hibernate. This means almost all of them will be adapted to the low light of nighttime. Of course they'll also need to be able to function during the day, so we'll need to avoid traits such as overly sensitive eyes that would be overloaded by full sunlight. Many creature will likely evolve Tapetum_lucidum so that they can see better in the lower light night time environment, though this has the downside of reducing the overall quality of eyesight in bright light conditions. Echolocation, along with heightened sense of hearing, smell and touch (ie. whiskers) will all be important in functioning both at day and during night.
Hibernating creatures will fall into two categories, diurnal and nocturnal. Both will need to be more adapted to their respective light conditions than most creatures, to make up for the extra vulnerability of hibernation. These creatures will also
need to be smaller so that they can more easily conceal themselves for their period of hibernation. Another possibility might be heavily defended creatures like Armadillo.

Insects are going to be huge, both in numbers and in size. I'm thinking that I'll want a few Superorganisms, probably one of which will be sentient (though certainly not a player race!)

I think Dinosaurs and Birds would both fit very well into this ecosystem. I'll probably have Dinos as the big herd animals of the world, roaming the highland plateaus. The carnivores will mostly have evolved into birds of prey. There will be many sea birds that live in the high cliffs of the plateaus.

I'm not sure what kind of marine life there will be on this planet either.

There's also going to be a variety of Dragons. See my other topic for more details on them.

Another thing I want is some kinda critter that can feed off the extreme "spirit energy" that sentient beings have. Possibly something that can form a symbiotic bond with other creatures as well.

Oh yeah, and I love symbiots, so if anybody has any cool symbiot ideas, let me know :)




Well I think that's a fairly good summary for now. I'll need to spend more time polishing everything, of course, as well as add some of your suggestions that I liked but didn't get around to including.

[snakefing]

Well, start with Flora, since this is largely the basis of the food chain. (You might also consider algae-based food chain too.)

The ultimate energy source for the food chain is usually sunlight. (Even here on earth, there are some ecosystems fed entirely by geothermal, though.) So you'll probably want photosynthetic plants. But they'll face a problem - very low light for earth-weeks at a time. So they'll need adaptations to this.

First, you might have some night-plants. They'd need to spread huge leaves out to capture enough of the diffuse light, but they'd have the advantage of lower competition since most plants would be day-plants. So they might grow as vines on tree-like day-plants, and when the day-plants go dormant at night, the night-plants sprout out big delicate tendrils that gather the diffuse ring-light to fuel their own growth.

Second, the day-plants would probably need some large root networks or pods in which they store nutrients derived from the sun during the long day. Then they'd go dormant (possibly even retracting underground) during the night. (Being fungal at night doesn't really help, because they generally exist by consuming the detritus of photosynthetic plants. So you still need the photosynthetic plants at the base of the food chain.)

Some plants could grow very quickly in the day, only to drop all their leaves every night.

If plants are generally not growing at night, they'd probably be at risk to herbivores during that time. So they'd probably evolve some pretty hefty defenses. Fronds might retract into hard, protective husks. They might evolve chemical defenses like potent alkaloids. Or they might end up in symbiotic relationships with fungi, insects, or the like that protect them during the long night.

Photosynthetic algae would face similar issues, but the range of solutions might be quite a bit wider. You could have big underwater aquatic "plants" that exist symbiotically with giant algae mats - at night the plant harbors a few of the algae, which are released in morning to spread and multiply into the giant mats, and at night the mats die out, feeding the plant that gives them refuge. Some algae could form spores of some kind to last out the darkness. They could drift the seas, following the sun or just blooming whenever the sun touches them.

The animals that feed on these plants could be even more bizarre, but that is a topic for another day.

[Nomadic]

Sidereal rotation period[/url]: 3278.9% that of earth [32.7 d]
Equatorial rotation velocity: 2.5% that of earth [11.33m/s]
Surface pressure: 340% that of earth [344.42 kPa]
Surface area covered by water: 60%

Albedo: ?

Surface temp in Kelvin:
   min: ?
   mean: 10 K warmer than earth (297 K)
   max: ?

Celestial Properties
No moons.
Large rings around the center of the planet shade the equator and provide illumination at night. Likely phosphorescent and possibly magical in origin.

Topography
Since there are no tectonic plates the topography is very different than that of earth.

The surface is relatively flat, with fewer great mountain peaks and ocean depths.
3% - Mountain peaks > 2000m above sea level.
12% - Highland plateaus 500m to 2000m above sea level (3-4 "mini continents").
25% - Archipelagos less than 500m above sea level.
15% - Shallow seas of depth <= 200m
20% - Ocean of depth 200m to 500m
20% - Ocean of depth 500m to 1000m
5% - Ocean of depth > 1000m
[/quote]Photosynthesis[/url].

The tropics are the areas near the Equator that are not shaded by the rings. These are the hottest parts of the world, which receive the most sunlight during the day and a large amount of illumination during the night.
Tropic Archipelagos are typically rain forests which have evolved to absorb the most sunlight during the day, and rain at night. These broad leaf trees can reach heights much greater than those found on earth.

I'm not really sure what the other climate areas would be like... I like the idea Cloud forests along with some highland Savanna, though I'm not sure how those would work with the geology.
[/quote]Mycorrhiza[/url] will be very important in sustaining plant life.
It looks like most forests would be Broad Leaf during the day and Fungi at night.

How would Plains and Savanna work here? I think we could certainly find plenty of grasses, since they can grow in practically any climate. Also since they often grow in areas with only occasional rainy seasons, or in areas where they spend months buried under snow, they should be able to adapt fine to the longer day/night cycle.

I think a lot of the flora would have to grow in spurts as well. I imagine there could be a lot of really cool flowers that follow the sun and what not.

I also need to think of what could grow in Water. The Coral Reefs might be too sensitive to temperature change (A rise in temperature of 1-2 degrees Celsius for 5-10 weeks or a decline in temperature of 3-5 degrees Celsius for 5-10 days has resulted in a coral bleaching event. source) to do well, which is disappointing.
[/quote]Cold-Blooded[/url] creatures are going to be on a very short lifespan cycle, probably only ever living for a single day. They will be born with the warmth of dawn, and lay their eggs as the sun sets, and die out during the cold of night. Hmm... I wonder if it would be possible to have these guys go the entire day without sleeping, and how big they would be able to get. They could be a rather entertaining pest if there's enough of them and they can grow big enough.

Warm-Blooded creatures will need to be able to feed both during the day and at night, or be able to hibernate. This means almost all of them will be adapted to the low light of nighttime. Of course they'll also need to be able to function during the day, so we'll need to avoid traits such as overly sensitive eyes that would be overloaded by full sunlight. Many creature will likely evolve Tapetum_lucidum so that they can see better in the lower light night time environment, though this has the downside of reducing the overall quality of eyesight in bright light conditions. Echolocation, along with heightened sense of hearing, smell and touch (ie. whiskers) will all be important in functioning both at day and during night.
Hibernating creatures will fall into two categories, diurnal and nocturnal. Both will need to be more adapted to their respective light conditions than most creatures, to make up for the extra vulnerability of hibernation. These creatures will also
need to be smaller so that they can more easily conceal themselves for their period of hibernation. Another possibility might be heavily defended creatures like Armadillo.

Insects are going to be huge, both in numbers and in size. I'm thinking that I'll want a few Superorganisms, probably one of which will be sentient (though certainly not a player race!)

I think Dinosaurs and Birds would both fit very well into this ecosystem. I'll probably have Dinos as the big herd animals of the world, roaming the highland plateaus. The carnivores will mostly have evolved into birds of prey. There will be many sea birds that live in the high cliffs of the plateaus.

I'm not sure what kind of marine life there will be on this planet either.

There's also going to be a variety of Dragons. See my other topic for more details on them.

Another thing I want is some kinda critter that can feed off the extreme "spirit energy" that sentient beings have. Possibly something that can form a symbiotic bond with other creatures as well.

Oh yeah, and I love symbiots, so if anybody has any cool symbiot ideas, let me know :)
[/quote]

All cool ideas. However remember that cold-blooded creatures could survive just fine here. The thicker atmosphere that makes your poles less severe means it takes longer to cool down. So instead of a reptile losing heat and being forced into hibernation at the onset of night, it could probably keep going for several days (possibly as long as 5-10) before it got too cold and it had to slow down. Even then the temperatures wouldn't be cold enough to stop a reptile dead. At worst they would have to hibernate out the last 2-3 "days" of night, waking up after the first or second "day" of light warmed the place up enough for them.

Symbionts are also a very good idea here. The trees being a good example (as well as snakefing's plankton/algae combo). This works for either plants or animals of course. You could have creatures that thrive in the day but are helpless at night that protect and are protected by something that the opposite is true for.

Giving an example perhaps you have a snake like creature that thrives in the daylight but goes dormant very quickly with temperature shift. It's body is home to a type of fungus that is helpless in the day as the heat messes with its ability to produce defensive chemicals. So during the day the snake protects it by letting it hitch a ride on its back (and letting it harvest its energy from the excess the snake has). During the night the snake goes dormant and the fungus it able to use starlight/ringlight to synthesize enough energy for itself. This means it becomes highly poisonous. The toxins of the fungus protect the snake while it sleeps. And so the cycle continues...

[Snargash Moonclaw]

Hmm - there are actually a lot of problems cropping up here that will pretty much necessitate establishing a magical field displaying some consistent "natural laws or properties" to counter those of physics - or you will result in something alien to the point of being nearly incomprehensible (at least for anyone attempting to play it). If you back up a little while to a relatively simple model which behaves as you describe and then gradually looking at the effects of other factors in the model, this shouldn't be insurmountable - there are just some inherent contradictions which will have to be "counterspelled" as you go (and a few of them you may be able to simply eliminate from the initial physical model before waving the divine magic wand).

One of the basic factors is mass itself. If you want a planet which is smaller in volume (not including atmospheric volume here - just the size of the solid/liquid ball itself) than Earth and more dense you can't also have a lower mass. Mass and density are functions of the overall atomic make-up of the planet. This will later effect atmospheric pressure (but the atomic/molecular content of that atmosphere will then come into play) but for now we're basically determining the amount of gravity the ball can exert. Overall (sum total of) atomic mass present determines how much gravitational force it exerts (size doesn't matter unless the gods have issues of inadequacy). So - if mass is 57%, gravity is as well - but still only referring to the ball (as if no atmosphere). Overall mass and gravity of the planet exerted upon the material of the orbiting ring = solid ball + atmosphere (and that much gas does have a lot of mass to consider later). Density of the ball is likewise a direct result of atomic composition. If it's more dense than the Earth, regardless of size and mass, as this is proportional, it is generally made up of denser (atomic) material. You actually need an overall composition that is stepping up your "average" on the periodic table. The good news is that this can't possibly be reasonably calculated - ballpark percentages of iron, etc. could be massaged a bit but you don't in fact need to do more than that - simply state that there's more X (denser element) and less Y and call it good. Eyeballing the table and assuming you want to keep the planetary core similar then I would suggest substituting some of that iron with molybdenum and tungsten in the molten core and perhaps even in the solid ores - essentially adding rather uncommon to rare metals (Earthwise) used to create ferrous alloys - on your planet more common and even needing to be refined out of the ore somewhat (moly-steel uses only a slight amount of the metal to make steel incredibly tough).

NB - sorry, but tectonic plates are an unavoidable physical effect of the molten core. The molten core is essential to planetary spin. You might consider solidifying it - I don't know the effect this would have on spin but you need a rational to slow it down anyway - magic would almost certainly need to fill in here - the question is how much.

What we are producing here however ultimately becomes much greater mass and gravity compared to Earth when we add an atmospheric layer - total gravitational force of the planet exerted on the ring (and the sun - this actually does effect the calculation in reality - not enough to bother with here - just realize that whenever something exerts a gravitational pull upon an object, that object, no matter how miniscule, also exerts a gravitational pull upon the first object).

Looking at atmospheric pressure then - this = weight of the perpendicular (to planetary surface) column of gas (= molecular mass of constituent elements x gravity) at the particular point and altitude where the measurement is being taken. There are two significant factors to consider here. Not only are there more molecules in the column at lower altitudes, but the additional molecules are also themselves heavier - both of these I think you were aware of when you answered my question about atmospheric density with regard to altitude. The question I have for you now however, is actually regarding the elemental makeup of the atmosphere. Again, comparing to Earth we have to look at the necessity of the oxygen/nitrogen content as well as the O2/CO2 exchange effect of photosynthesis. (If you step away from that process with regard to storing sunlight as calories in plants and play with other biology, you still need to look at oxygen exchange before doing so I'm afraid.) Going back to the Periodic Table we run into other problems producing a heavier/denser atmosphere. A Chlorine (Cl2) atmosphere will be about twice the surface pressure at sea level - and toxic. Beyond that you have to look at Noble gases - nonreactive (so they can't offer any sort of respiration to a biological organism) and monatomic - a molecule consists of a single atom only - so you need an atmosphere containing a lot of Krypton. Of course if the organisms are simply unaffected by this then it won't (being a noble gas) interfere with the respiration of any O2 and CO2 present - you could have your heavy/dense sea level atmosphere, I just have no idea what effect the presence of that much krypton gas actually would have on your life forms. (Personally, I'd be more inclined to fiddle with this than a chlorine atmoshpere. . .)

The odd thing about using atmospheric mass to raise your total so as to keep the mass of the ball itself low is that your atmospheric layer becomes thinner in terms of miles above the surface. When the (solid) planetary mass is reduced it is then unable to retain the less massive gases composing the outer layers of the atmosphere - all the gasses composing the atmosphere of course tend to settle - hence the "thinness" of air at high altitude. Less pressure due to shorter column but more to the point, more lighter gases and less oxygen. Avogadro's Number is a constant after all - the two factors just mean the atoms aren't packed so tightly. The part that really matters here is that heat exciting the molecules (Atoms really - at high altitudes we're dealing w/noble gases) causes them to move at escape velocity much more readily if the solid planet below is unable to exert sufficient gravity to hold them! If your planet is less massive/lower surface gravity than earth than your atmosphere will contain significantly less amounts of lighter gases - and consequently extend far less from the planets surface. Massaging these various factors can certainly help produce a world in which flight is quite common however.

[Xeviat]

A couple of things. First off, making a solid core will eliminate your magnetosphere, meaning the planet will be bombarded by bad radiation. You'll need something to shield this.

As for sleep cycles, look into how deep sea creatures and cave dwellers who never leave sleep. i'm sure there's research on that.

[Snargash Moonclaw]

A couple of things. First off, making a solid core will eliminate your magnetosphere, meaning the planet will be bombarded by bad radiation. You'll need something to shield this.

Interesting - I wasn't aware of that factor, assuming the magnetosphere to be pretty much entirely the result of the solid deposits creating the magnetic poles. (It may be unrelated to that phenomenon entirely, I don't know. . .) If it weren't for the oddity of declination I would expect that the deposits and the molten iron core are not coincidental, but have basically assumed them to be so. (I haven't given significant thought yet to such polarity, but need to look at it in Panisadore as well with regard to navigation at the very least.) Can you give a thumbnail explanation of how this works?

[Nomadic]

Yea the Kapn is right. The magnetic field of a planet with an earth like core draws its power from the liquid outer core's generation of electrical currents (the Earth is basically a giant electromagnet... tons of molten metal spinning around at high speed.... yada yada... you get the point). The heat of the core surpasses the point at which iron loses it's magnetic properties (Curie point I think it was). Thus the magnetism cannot be drawn simply from having a magnetic material.

In theory you could have a solid core that could pull it off. However that is a highly theoretical one and I cannot think of any way to do it without magic.

[Snargash Moonclaw]

So the magnetic polls don't actually have anything to do with the Earth's electromagnetic field since that's caused by the motion in the core - separate cause of separate effect; evidently the field so produced likewise has no effect on the magnetic polarity either, or does this establish the polar directions of the flow of that electormagnetic field?

[snakefing]

The spinning of the core produces a dynamo effect that generates the magnetic field of the earth. The magnetic poles just show how the dynamo is oriented. The location of the magnetic poles is not fixed - they wander about quite a bit on geologic scales.

In fact, there have been occasions where the dynamo has reversed itself and the magnetic polarity of the earth has flipped 180 degrees. This can be seen, for example, in the alignment of magnetic crystals in the sea floor that crystallized from lava at different times.

Now, in a fantasy world, you may not have any magnetic fields, no cosmic radiation, etc. Or the fields could be the residue of demonic energy. Or whatever you want. These kind of things can fairly easily be hand-waved away. It just depends on what you want, what you want your players to pay attention to, and how much you want these things to be consistent with each other.