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s0meguy
05-28-2012, 11:22 PM
Hey there. I've been trying to figure out the climate for my planet before I fill it in with the appropriate environments. I have read a lot of advice on what an Earth sized planet should be like, but can't find any advice for planets that differ.

For example, my planet is about twice and a half the circumference of Earth (5 times its surface area) and it spins a lot faster. Also the gravity acting on the atmosphere is much stronger. Does this necessarily mean that because of the much stronger coriolis effect, there are a lot of hurricanes/cyclones compared to Earth? Maybe even some permanent ones, or an area that is constantly spewing out hurricanes. This might make some areas of the world uninhabitable. Maybe even a lot of the area around the tropics, where the wind would be the strongest? Maybe thunderstorms would be a lot more common at the equator.

Also, the Earth is divided in 2 horse latitudes and the ITCZ between them, with the winds flowing to the ITCZ and the polar regions from the horse latitudes. I have been trying to figure out if my planet would have more than 2 horse latitude-like bands that are progressively colder, because of its increased size?

Can you guys think of what other general climate differences there would be, because of a larger size, higher gravity, higher spinning speed? Maybe the fact that theres a lot more land and oceans on the planet also does something, and there are a lot more tectonic plates. Maybe there are even some climate/weather phenomenoms that are unseen on Earth! That would be interesting. But I am not knowledgable enough on climates to predict them.

Any thoughts?

Gidde
05-28-2012, 11:35 PM
Do you plan on having humans live on this super-earth? I ask because high-grav planets would be really hard to live on. The stress on the musculoskeletal system from weighing a lot more and the increased atmospheric pressure would make it almost impossible to breathe and to move around.

Sorry, I know this doesn't really answer your question, but it's something you ought to have an answer for when you start writing your story (or setting or whatnot), because your readers will wonder.

s0meguy
05-29-2012, 03:02 AM
There's an additional factor that probably will have an important effect: the atmosphere is twice the Earth's and it's chemical ratios are different. I wonder how higher and lower amounts of x types of gas would affect climates and weather?


Do you plan on having humans live on this super-earth? I ask because high-grav planets would be really hard to live on. The stress on the musculoskeletal system from weighing a lot more and the increased atmospheric pressure would make it almost impossible to breathe and to move around.

Sorry, I know this doesn't really answer your question, but it's something you ought to have an answer for when you start writing your story (or setting or whatnot), because your readers will wonder.

I considered that. I indeed would like humans to live on this planet, among other sentient creatures. But they are not from Earth, which doesn't exist in my universe. They evolved on this planet and thus adapted to its stronger gravity with a slightly different bone and muscular structure, among other things. A necessary and I think reasonable tradeoff as I wanted to make my world large because I don't think its very realistic for (for some, drastically) different sentient species to evolve on a planet the size of Earth. This way I can also make the world very varied climate and vegetation wise, and also politically varied, since it is much more difficult to maintain global empires when the planet is so large. At least, until the space age.

Gidde
05-29-2012, 09:48 AM
Cool! Sounds like a plausible backstory too. Carry on ;)

dlaporte7271
05-29-2012, 10:56 AM
You know...I don't know how much Sci-Fi you read, but are you familiar with Robert Silverberg's Majipoor? It's a gigantic world settled by humans....I think he got by the gravity thing by making the planet less dense: http://en.wikipedia.org/wiki/Majipoor_series

Just food for thought.

How about atmospheric density...if gravity acts more forcefully on the gasses (whatever their makeup) then they are under more pressure and will behave differently yes?

dlaporte

s0meguy
05-29-2012, 12:01 PM
You know...I don't know how much Sci-Fi you read, but are you familiar with Robert Silverberg's Majipoor? It's a gigantic world settled by humans....I think he got by the gravity thing by making the planet less dense: http://en.wikipedia.org/wiki/Majipoor_series

Just food for thought.

How about atmospheric density...if gravity acts more forcefully on the gasses (whatever their makeup) then they are under more pressure and will behave differently yes?

dlaporte

Yup, I did this. But I don't want it to be too low, since I want it to be a metal rich planet (metals are nice for many things, including life, they have plenty of functions in our bodies). I'm pretty sure that a low average planetary density indicates a metal poor planet. To add to that, huge planets (that are not gas planets, but rocky/terrestial ones), because of their large mass which increases their gravity and pull the planets mass more inwards, becoming more dense, will naturally assume a much higher density than a smaller planet. In other words, density increases exponentially with mass because of gravity, and a lot of mass is needed to make a large terrestial planet. I'm curious what the mass, diameter and density of the planet is that you refered to, its not in the wiki article. But you can only go so far down with the density until it becomes a gassy planet instead of a terrestial one.

And yup, the atmosphere's components, pressure and density would also have an effect. What, I'm not exactly sure... Perhaps the heavier the gas, less warmth they need to sink back to the Earth, thus creating more Hadley cells?

dlaporte7271
05-29-2012, 01:45 PM
Here's another link http://www.majipoor.com/majipoor/majipoor_geography.php

One of the other nifty elements of Majipoor was the size of some of the life...especially the sea dragons. You could imagine life on a larger planet being exponentially larger as well...

There are other factors that could contribute to weather patterns as...consider the internal heating system of the planet, the size and make up of the core and any related magnetic fields that could contribute to weather phenomena. I believe that one theory about why Mars lost it's atmosphere has to do with it's smaller core and lack of magnetic field. I've also seen discussion about weather on some of the outer planets and interesting theories about why there are weather patterns on planets that weren't expected to.

What about moons? Distance from the sun? Multiple suns? Gads...this could go on forever....fun exercise to be sure.

I'm actually creating a world, in my own campaign, that has unusual conditions that will affect weather...I will have to go through this exercise myself, just to get my head around all the potential factors so I can come up with something that makes sense.

I'm sure you may have done some of this but here are a couple of other links NASA discussion of weather on other planets:

http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=725 (brief talk about the weather in the solar system)
http://cseligman.com/text/planets/magnetism.htm (article about planetary cores and magnetic fields)

kermode
05-30-2012, 06:01 PM
Cyclones (hurricanes) are not caused by the Coriolis effect, but by low pressure gradients. An increased Coriolis effect might make cyclones form faster, but if the other components needed to make hurricanes (warm water and a pressure change, basically) are not there, no amount of spinning will make them form. Basically hurricanes form over warm water, so if your planet contains more warm water than Earth, then it will have more hurricanes.

And I think your ideas for extra horse bands/doldums are pretty good. I don't know exactly what would happen with all that, so making more bands seems like a pretty good idea. You seem to know your stuff! I hate it when people just draw random climates in random places with no knowledge of how climatology or plate tectonics work.

s0meguy
05-30-2012, 10:37 PM
Dlaporte, thanks for the links. They're very interesting. Especially for creating weird exo-planets. But this one has a more Earth-like climate. Yes, there are many important factors. Too many really to reliably know what they'd do. We have been wrong many times about the features of other planets in our own solar system, and while reading I came across quite a few phenomenon that defy explanation. There's just many things that we don't understand.

We're barely proficient at explaining climate features that we know are there, nevermind predicting hypothetical ones.


Cyclones (hurricanes) are not caused by the Coriolis effect, but by low pressure gradients. An increased Coriolis effect might make cyclones form faster, but if the other components needed to make hurricanes (warm water and a pressure change, basically) are not there, no amount of spinning will make them form. Basically hurricanes form over warm water, so if your planet contains more warm water than Earth, then it will have more hurricanes.

And I think your ideas for extra horse bands/doldums are pretty good. I don't know exactly what would happen with all that, so making more bands seems like a pretty good idea. You seem to know your stuff! I hate it when people just draw random climates in random places with no knowledge of how climatology or plate tectonics work.

I looked it up. You're right. I should've known that.

I concluded that nobody really knows for sure about what the climate system would be like on a large planet - even weather forecasts on our own planet are notoriously unreliable over more than a few days.

Veldehar
05-30-2012, 11:07 PM
Yeah you've wandered into the hypothetical realm that a NASA scientist couldn't 100% answer... likely not close to 100%. Being Earth-like, but bigger, one suggestion I would make is that the increased Coriolis effect you imagine wouldn't necessarily increase wind speeds at the equator, as Earth doesn't have that effect. Rather, storms and basic wind patterns would track more directly east-west, like I think they do on Jupiter... I think, LOL.

Speaking of things we don't fully understand... think tectonics on a planet moving extra fast and being that large... what effects there?

My suggestion is to be a bit like me... in my world I ask if magic did this, what would be the real world effects? Then make an educated guess that seems plausible and stick with it! Thinking too much will drive you crazy... not that I wasn't there already. LOL.

s0meguy
05-31-2012, 03:14 AM
Yeah you've wandered into the hypothetical realm that a NASA scientist couldn't 100% answer... likely not close to 100%. Being Earth-like, but bigger, one suggestion I would make is that the increased Coriolis effect you imagine wouldn't necessarily increase wind speeds at the equator, as Earth doesn't have that effect. Rather, storms and basic wind patterns would track more directly east-west, like I think they do on Jupiter... I think, LOL.

Speaking of things we don't fully understand... think tectonics on a planet moving extra fast and being that large... what effects there?

My suggestion is to be a bit like me... in my world I ask if magic did this, what would be the real world effects? Then make an educated guess that seems plausible and stick with it! Thinking too much will drive you crazy... not that I wasn't there already. LOL.

The winds flow differently on my planet than on Earth, creating some zones of extreme weather, which is how I liked it.

I couldn't find too much about the effects of tectonics on climate, except that they change the climate by moving landmasses around and create volcanoes that have an effect on the environment, and mountain ranges that hoard rain and in turn create rivers, that fertilize huge areas. Faster and stronger tectonics could mean more of all that and more expansive mountain ranges. I suppose the pressure on tectonic plates would be higher on a larger planet, as the amount and size of plates pressing on each other is higher, and the plates are thicker and gravity is stronger. Creating higher mountain ranges. More earthquakes, volcanic eruptions, underwater volcanic eruptions that fertilize the water and foster underwater biodiversity, increasing ocean foodchains that in turn increases abovewater foodchains (and biodiversity) which interact with the underwater ones, and cause tsunamis that cause extinctions, in turn leaving space for further evolution of creatures to fill in the void. That influence the environment themselves. The chain of cause and effect goes on for a long time. You can apply the same to mountain creation->river creation->...

I agree. I've spent way too much time reading every little piece of information I could find and obsessing over what its effect would be, and then trying to predict its effect with a gazillion other factors. And there's an unknown large amount of factors that we don't even understand. So I figure that we can venture anywhere with our worldbuilding as long as it obeys the basic and important advanced principles of nature as we know them. Who knows what other effects could be at work. We can even think of some of our own factors. I've been thinking about altering the periodic table for my universe, giving some of the rare elements that don't really have an important function (that can't be replaced by another) some more interesting properties. And expanding the periodic table, giving some of the higher useless elements that have halflives that can be measured in nanoseconds in our universe, a function. It's part of the beauty of designing a fictional universe that your imagination (and will) is the only limit, I think.

Magic is an interesting subject too. I want there to be magic, that is seen as a natural force instead of "magic", seen that way by both the people in my universe and readers. Kind of like how eezo's effects are seen in the mass effect universe. But at the same time I want it to have more of the mystery and flexibility surrounding magic in the fantasy genre. But it's harder to implement that than it might seem. I'm taking my planet through the primitive age to beyond the spage age, so it should be compatible both with a fantasy setting and a sci-fi setting.

Veldehar
05-31-2012, 09:36 AM
The development of a magical philosophy and its interaction with nature slowly lead to developing an entirely new game in order to fit item creation etc. it wasn't the only reason, but it was a catalyst. Effectively I altered the periodic chart, without bothering to actually do so. Once I finish my book on elemental metallurgy... LOL. Okay, the full system for that would be best suited for an MMO.

s0meguy
05-31-2012, 03:36 PM
Something else I thought of - with a larger atmosphere, there is more warm air and thus has more capacity to absorb and carry moisture, and where the air at a high latitude is really moist, carrying part of it over large mountain ranges more than could happen on Earth, negating the dry areas that would exist behind mountain ranges on Earth.

cfds
06-01-2012, 05:52 AM
I just want to add that on a larger planet mountains are lower than on smaller ones since the higher gravity prevents the "growth" of them.

s0meguy
06-01-2012, 08:15 AM
I just want to add that on a larger planet mountains are lower than on smaller ones since the higher gravity prevents the "growth" of them.

But the forces that cause the formation of mountains would be exponentially stronger.

dlaporte7271
06-01-2012, 11:28 AM
I just want to add that on a larger planet mountains are lower than on smaller ones since the higher gravity prevents the "growth" of them.

I don't know that you can really make the claim about plate tectonics, mountain height, and planet size...at the moment, we only have one example of plate tectonics in action...and that's the earth. Anything after that is all hypothetical and theoretical. Earth is the largest rocky planet in our solar system and none of the other planets exhibit any evidence (so far) of plate tectonics...the rest are 'uniplate' planets...here's a link to a brief conversation on the topic
http://www.geolsoc.org.uk/gsl/pid/6580;jsessionid=177F58FC3890392BBCFE790B169879E6

There are certainly much larger mountains on other planets...created by other forces...mostly volcanic activity (Olympus Mons on Mars). We just don't have any examples of rocky planets, larger than the earth, to know...so it's all speculation.

It seems that the question of plate tectonics comes down to a definition of the planetary core. So if you want to go into this level of detail, what's your core made of? How big is it? What's happening down there to create movement? Why can't there be forces at work in the core that could overcome gravity enough to force a mountain higher? Maybe the planet has a thin, and therefore, lighter crust?

thekonkoe
06-03-2012, 01:16 AM
I would suggest looking at the atmosphere of Venus as a starting point. There was a Nature article recently drawing some parallels between that atmosphere and ours. Etxrapolating from that might help. Food for thought, It seems likely that Venus has roughly the same number of volatiles as we do despite its much thicker atmosphere. Earth just stores a greater portion in its ocean and crust. So you don't absolutely need a thicker atmosphere, i.e. if you wanted to you could get a more Earth like pressure.

I am fairly knowledgeable about atmospheric chemistry and have some experience with planetary formation. I'm hoping to study exoplanet atmospheres if I can get funding. I might post more later, but if you have specific questions you can pm me. Particularly with UV shields and sulfur chemistry in atmospheres.

cfds
06-04-2012, 03:10 AM
The maximum height of mountains is determined by two factors: the surface gravity and the amount of energy needed to melt a given quantity of the material the mountain is made of. The mechanism of the creation does not play a role.
On Earth the maximum height for a granite block with constant crosssection is about 10 km, on Mars it would be close to 30km. A planet with the double surface gravity of Earth could have mountains half as high.
IF mountains reach this height depends on the relative effectiveness of erosion and uplifting.

s0meguy
06-04-2012, 12:47 PM
The maximum height of mountains is determined by two factors: the surface gravity and the amount of energy needed to melt a given quantity of the material the mountain is made of. The mechanism of the creation does not play a role.
On Earth the maximum height for a granite block with constant crosssection is about 10 km, on Mars it would be close to 30km. A planet with the double surface gravity of Earth could have mountains half as high.
IF mountains reach this height depends on the relative effectiveness of erosion and uplifting.

This statement seems to me not to make much sense. Even if the mechanism of creation doesn't play a role, the maximum height of mountains would be relative to the core of the planet, and not to whatever height inhabitants of the planet decide to call "zero". Which would probably depend on the amount of water on the planet, the more the planet is filled with water the higher up the inhabitants have to live, the "shorter" the mountains would be. The closer the inhabitants live to the core of the planet, the higher the mountains are from their perspective. So you can't just say that mountains would be less tall than those on Earth without knowing at which height the inhabitants live.

dlaporte7271
06-04-2012, 06:34 PM
The maximum height of mountains is determined by two factors: the surface gravity and the amount of energy needed to melt a given quantity of the material the mountain is made of. The mechanism of the creation does not play a role.
On Earth the maximum height for a granite block with constant crosssection is about 10 km, on Mars it would be close to 30km. A planet with the double surface gravity of Earth could have mountains half as high.
IF mountains reach this height depends on the relative effectiveness of erosion and uplifting.


Can you point to some sources about mountain creation that back that up? I'm genuinely curious....what about a mountain made of volcanic rock?

cfds
06-06-2012, 07:09 AM
Just imagine a (prismatic) block of material with crosssection A in a homogeneous gravitational field (so that the potential is m*g*h). It does not matter how it got there. If this blocks "moves down" by delta_h it releases the energy M*g*delta_h(1), where M is the mass of the total block, M=A*h*density(*). The question is now: is that released energy enough to melt the delta_h hight base layer of the block? It is if the energy equals H_m*A*delta_h*density(2), where H_m is the melting enthalpy of the material the block is made from and A*delta_h*density the mass of the layer that has to be melted. Equate (1) and (2) (and substitute (*) into (1)) and get: g*h=H_m. So, for h>H_m/g the lowest layer of the mountain melts away (and gets squeezed out) until the mountain reaches the critical height.
The equation (*) depends on the geometry of the mountain, it would be M=A*h*density/3 for a cone.
The height is measured in relation to the (floating) tectonic plate.

dlaporte7271
06-06-2012, 10:29 AM
So what you're basically saying is that a big heavy mountain of material will eventually get so heavy that it's weight will generate enough energy in the form of heat to melt the base layer, thereby reducing the overall potential height?...So even with a lower density material...the melting point might be lower and could 'even things out' vs a higher density material with a higher melting point?

(love this kind of stuff...hope you're ok with my lay-mans description...I am a lay man after all) I'm assuming cfds that you are either a geologist(or related science)...or you found this on wikipedia (grin) and doing a good job of faking it.;)

cfds
06-08-2012, 02:49 AM
Yes that is what I meant to say.

And I am a physicist, this "mountain height thing" is one of our favorite exercises in "impress people by using simple assumptions and algebra" :)

dlaporte7271
06-08-2012, 11:19 AM
Cool...Now I know where to go with all my physics related questions (grin). I suspect that, while really interesting, this may amount to a level of detail that goes beyond the scope of s0meguy's original intent. I can say, for myself, that my world building project won't require this level of detail. In fact...I know my imaginary planet defies all kinds of 'laws of physics'. I'm using lots of divine intervention to justify things. Trying to mix a certain degree of realism with your fantasy can be a tricky balancing act.

s0meguy
06-08-2012, 03:18 PM
I care a lot about realism. If something I put in my universe is something that could not physically exist, it will bug me until I have somehow justified it or removed it. But when creating a fictional universe, realism is flexible. There is no reason that another (even real) universe can't have different constants that cause elements to have different properties, and for particles to behave differently. But anyway, assuming our universe's rules:

So, the higher the melting point of the material at the core of the mountain, the higher it can become? Melting points are pretty variable between different elements, so if for some reason large deposits of rare metals accumulated there, the max height of the mountain could be a lot higher?

I wonder on what timescale mountain ranges "melt away" using those processes. Giant mountains could still be young ones.