Mission of Gravity -- Rapidly Spinning World

[Peter Toth]

Hi Guild!

I've been working on this new project since the beginning of the year and have made some decent progress (or not, depending on your perspective, lol). The maps below represent a conworld that spins in a period of just over 5 hours, as well as exhibits its own unique orbital and rotational elements, much like the world in Hal Clement's "Mission of Gravity" novel. I've decided to use this setting to create a large wall poster documenting a nearly impossible journey undertaken by a few inhabitants of this planet to "save the world" from destruction by a formidable foe. That formidable foe is something I haven't yet decided on; however, I'll update you when that detail has been finalized. The story's main premise is a gravitational gradient: as the characters travel towards the pole, gravity gradually intensifies (and climate becomes more frigid with gusty winds), making the journey more perilous than an equivalent journey on the earth.

Initially, I wasn't intending to post until after the final copy was complete, but realized this way I could get some feedback regarding the plausibility of my tectonics and geological features. I'm quite certain my map is riddled with features that are geologically implausible or just plain erroneous. Please point them out to me.

I've modelled the climate using Clima-Sim and calculated the ice lines for perihelion (red) and aphelion (blue). (The world has less than 5 degrees of obliquity but a highly eccentric orbit.) The graticules and atmospheric circulation cells are modelled from Nikolai's Worldbuilding Pasta, to which I owe a great deal of credit for both informing me and inspiring me. Thank you so much, Nikolai, and as soon as I reformat my Linux partition, I'll reinstall ExoPlaSim to see how differently it renders the ice lines and other climactic details. (And I'll buy you that exotic coffee as well!)






As you can see, the planet itself is quite oblate with flattening value of almost 0.1, compared to the earth's measly 0.0034. I've calculated a water bulge measuring over 1300 metres at the equator. (Will have to render that later.)

As you may have guessed, I'm attempting to render everything on this planet very accurately in terms of hard physics, so if you have any ideas or suggestions about what aspects to consider to make this project "complete," I'd like to hear them. By the way, does anyone know why the kinematic viscosity of air is inversely proportional to its density; i.e. denser air is less viscous? This doesn't make sense to me, but I need this figure to determine my atmospheric circulation pattern.

And one final note: some continents haven't yet been fully processed in Wilbur and look somewhat "poor quality," so please ignore that for now. Later on, I'll be creating some realistic terrain on every continent besides the main one.

At any rate, I hope you all enjoy these maps; it is my absolute pleasure to render them!

Peter

[Naima]

The PRoject looks interesting and overall looks good, I am wondering if you had a preliminary tectonic study though as the mountain ranges seem pretty random noise distribution to me rather than based on tectonic movements? Nothing wrong with that anyway .
As for Kinematic Viscosity is defined as the ratio of dynamic viscosity to density.
It represents the fluid's resistance to flow while considering its density, which is important when comparing the flow characteristics of fluids with different densities.
ν = μ / ρ

In this equation, ν represents kinematic viscosity, μ represents dynamic viscosity, and ρ represents density. Kinematic viscosity is obtained by dividing dynamic viscosity by the density of the fluid.

[Peter Toth]

Hi Naima,

Thank you for your response and critique. Unfortunately, unlike some of my other projects, I didn't do a detailed modelling of tectonic plate motion to determine mountain ranges; I merely placed them in logical places based on a quick study. I did, however, get a bit hasty and dropped some ranges on other continents not relevant to my story, so everything except the two ranges in my first map (above) will probably be reworked into something more plausible.

I don't understand why, according to your definition of kinematic viscosity, that thicker, higher-density air should be less viscous than thin air. It's ludicrous. I do, however, need to derive a value for my atmosphere's kinematic viscosity to determine the circulation regime, as shown by this graphic:



As you can see, the red dot represents my current regime at 1.8 atmospheres, consisting of axisymmetric circulation. This regime doesn't allow any wave/eddy disturbances that may evolve into cyclones and anticyclones, and therefore undermines the plot of my story, so I've simply determined the threshold pressure at which I'd be in the "multiple jet" regime (green dot). This corresponds to about 2.4 atmospheres, so I'll have to dial down the oxygen and CO2 percentages to maintain the desired partial pressures. Other than that, 2.4 atmospheres seems workable.

Do my calculations look correct?

I've used the following equations to derive the frictional Taylor number (x-axis) and the thermal Rossby number (y-axis):



I don't know if anyone has any expertise to offer, but if you know about this phenomenon, I'd like to hear your opinion.

Thanks in advance.

Peter

[Naima]

Hi Naima,

Thank you for your response and critique. Unfortunately, unlike some of my other projects, I didn't do a detailed modelling of tectonic plate motion to determine mountain ranges; I merely placed them in logical places based on a quick study. I did, however, get a bit hasty and dropped some ranges on other continents not relevant to my story, so everything except the two ranges in my first map (above) will probably be reworked into something more plausible.

I don't understand why, according to your definition of kinematic viscosity, that thicker, higher-density air should be less viscous than thin air. It's ludicrous. I do, however, need to derive a value for my atmosphere's kinematic viscosity to determine the circulation regime, as shown by this graphic:



As you can see, the red dot represents my current regime at 1.8 atmospheres, consisting of axisymmetric circulation. This regime doesn't allow any wave/eddy disturbances that may evolve into cyclones and anticyclones, and therefore undermines the plot of my story, so I've simply determined the threshold pressure at which I'd be in the "multiple jet" regime (green dot). This corresponds to about 2.4 atmospheres, so I'll have to dial down the oxygen and CO2 percentages to maintain the desired partial pressures. Other than that, 2.4 atmospheres seems workable.

Do my calculations look correct?

I've used the following equations to derive the frictional Taylor number (x-axis) and the thermal Rossby number (y-axis):



I don't know if anyone has any expertise to offer, but if you know about this phenomenon, I'd like to hear your opinion.

Thanks in advance.

Peter

May be you are confusing Kinematic viscosity with dynamic viscosity
Dynamic viscosity (also known as absolute viscosity) measures the fluid's internal resistance to flow
Kinematic viscosity measures the fluid's resistance to flow under the influence of gravity.
When the density of the fluid increases, for the same amount of dynamic viscosity , the kinematic viscosity decreases because you're dividing by a larger number. This indicates that denser fluids have lower kinematic viscosities when their dynamic viscosity remains constant.Conversely, if the density decreases, the kinematic viscosity increases, assuming the dynamic viscosity stays the same. This shows that less dense fluids spread or flow more easily under the influence of gravity alone.In summary, dynamic viscosity is a measure of a fluid's inherent resistance to flow due to its internal friction, independent of its density. In contrast, kinematic viscosity considers the fluid's density and provides insight into how the fluid flows under gravity.

That said , why you do even need that ? If your scope is calculate gravity , just consider masses, densities and define core elements.

[Peter Toth]

Thank you for the lucid explanation Naima; I believe I can now visualize the difference between the two terms. Because kinematic viscosity decreases for air at a higher density, it flows more easily under the influence of gravity. Thus, you've essentially answered my question about whether my calculations are correct regarding the derivation of the frictional Taylor number.

I need this data because I'm also trying to decide the atmospheric circulation regime for my planet, with a preference for "multiple jets" which features eddies that mature into cyclones vs. asymmetric circulation which precludes jets and eddies from forming in the first place. Essentially I want a planet that features unpredictable weather dominated by cyclones, which can only occur at about 2.3 atmospheres on my planet factoring in its (extreme) rotation rate.

By discussing this topic with enthusiasm, I was also hoping to generate interest, and therefore membership applications, for Cartographer's Guild. I notice that 4,500 individuals have viewed my map as of 7 PM on February the 6th. If even one in 1,000 of those viewers had any expertise or previous interest on this topic, that could potentially generate 4 or 5 new members who could support Cartographer's Guild and join the discussion, especially for conworld submissions, which I consider the "less popular" type of map.

Again, thank you, Naima, for your expertise in explaining the difference between dynamic viscosity and kinematic viscosity; I'm now one step closer to a finished project here.

And for those other members who are interested in this kind of map, I'll update you as soon as I have more material.

Thanks.

Peter

[Naima]

Thank you for the lucid explanation Naima; I believe I can now visualize the difference between the two terms. Because kinematic viscosity decreases for air at a higher density, it flows more easily under the influence of gravity. Thus, you've essentially answered my question about whether my calculations are correct regarding the derivation of the frictional Taylor number.

I need this data because I'm also trying to decide the atmospheric circulation regime for my planet, with a preference for "multiple jets" which features eddies that mature into cyclones vs. asymmetric circulation which precludes jets and eddies from forming in the first place. Essentially I want a planet that features unpredictable weather dominated by cyclones, which can only occur at about 2.3 atmospheres on my planet factoring in its (extreme) rotation rate.

By discussing this topic with enthusiasm, I was also hoping to generate interest, and therefore membership applications, for Cartographer's Guild. I notice that 4,500 individuals have viewed my map as of 7 PM on February the 6th. If even one in 1,000 of those viewers had any expertise or previous interest on this topic, that could potentially generate 4 or 5 new members who could support Cartographer's Guild and join the discussion, especially for conworld submissions, which I consider the "less popular" type of map.

Again, thank you, Naima, for your expertise in explaining the difference between dynamic viscosity and kinematic viscosity; I'm now one step closer to a finished project here.

And for those other members who are interested in this kind of map, I'll update you as soon as I have more material.

Thanks.

Peter

Considering your goal of creating a planet dominated by unpredictable weather and frequent cyclones, I am not sure if you really need to delve into complex atmospheric calculations, I suggest more simply to envision a world with an extremely fast rotation rate and a thick, dense atmosphere. These characteristics naturally lead to the formation of multiple jet streams and the frequent development of powerful storms. The rapid rotation and atmospheric density would contribute to a dynamic climate system, where the interaction between the planet's varied topography and atmospheric dynamics creates ideal conditions for cyclone formation. This setup could allow for a narrative where the inhabitants and ecosystems have uniquely adapted to these extreme conditions, with societies developing innovative ways to cope with or predict the stormy weather. Grounding your world in these broader scientific principles enables you to achieve your desired atmospheric conditions, adding depth to your world-building without the necessity of detailed calculations. But of course its a fantasy world and depending on your goals I doubt anyone would come to check your calculations behind , but if your goal is to provide a scientific brainstorming then its another matter. I am not that versed in planetary science apart the things I need for my worldbuilding scopes usually.
That said how did you see 4500 viewed your map ?

[- JO -]

You two have completely lost me!
I'm unable to follow your scientific reasoning, which I find fascinating!
All I can say is that the story you're writing sounds very promising!
In any case, the basic idea, with the crucial role played by the environment, is really interesting!

[Peter Toth]

Hello Guild,

Due to immense struggles in taming the ExoPlaSim program, I've accomplished relatively little since my previous post. Despite about 30 hours of tinkering with the program, I couldn't properly simulate the temperature data for my world's topography, although the default Earth map ran nicely using my world's parameters. Thus, all I had to do was extrapolate the temperatures and then the climate.

I owe a great deal of credit to Nikolai's (worldbuilding pasta) helpful and prompt technical advice for ExoPlaSim, without which I couldn't have accomplished this level of detail. As Frodo--my world--is strikingly dissimilar from the Earth, I don't think that Azelor's climate tutorial would have accurately produced the temperature and climate data.

If you're interested, Frodo has a 5 hour day, a 785 earth-day year, a larger diameter and mass, over 2 times greater atmospheric pressure, a negligible obliquity, but a considerable eccentricity.

Here's a temperature map for Frodo, shortly after perihelion, when temperatures have attained a maximum. Notice that the land is hotter than the oceans at about 30 degrees, but then colder poleward.



Then shortly after aphelion, Frodo looks like this. Notice how the land is everywhere colder than the ocean.



And then here is a crude Koppen map:



As you can see, Frodo consists of primarily desert terrain and no tropical rainforests due to very minimal precipitation, in turn due to a higher atmospheric pressure and a lower level of average insolation. (Water evaporates less readily in dense air). Notice how rapidly the climate transitions from temperate oceanic (Cfb) to tundra climate (ET). Worldbuilding pasta mentioned this phenomenon in his blog, which was a huge source of inspiration for me.

Does anyone know why my parameters work beautifully on Earth topography, but start giving me very cold climates once I've dialed Frodo's topography into ExoPlaSim? I initially thought that maybe the CO2 was condensing at the poles due to the unusually low temperatures (-95 C), until I got rid of mountains and terrain in general past 60 degrees north and south.

Incidentally, I've discovered that Frodo would not have cyclones below a threshold of about 2.1 atmospheres; hence my reasoning for ramping up the pressure. The results of this situation, a "desert world with cyclones," will form a beautiful backdrop for the plot I have in mind.

Next I'll be working on precipitation. I hope to have figured out ExoPlaSim by then!

Cheers,

Peter

[Naima]

It looks very good, but as a sugestion , I messed around with Exoplasim and other climatic simlation tools and none so far beats the logic in my opinion , and also manual work, apply some logic and you can get a climatic map that is accurate and more relieable in my umble opinion than wasting days on forcing data into complex tools.
Artifexian docet in my opinion and more than enough.

[MrBragg]

apply some logic and you can get a climatic map that is accurate and more relieable

Eh, I don't know, for something this esoteric I think "logic" is kind of hard to apply without a very strong background in atmospheric physics that I doubt many people have. Even if the computer output simply serves as a guide for further manual refinement--which it almost certainly should, given the limitations of the model--it seems like a valuable addition to what we might intuitively think should be the case.

Peter, what errors / crashes were you getting with EPS? And what resolution were you working with?