log in or register to remove this ad

 

World building idea: Jupiter-sized Earth

Mercurius

Legend
This is actually an idea I'm playing with for a writing project, but thought the smart folks of ENWorld could offer good advice.

The basic idea--at least relevant to discussion here--is a Jupiter-sized world, but one that is inhabitable by humans.

Some questions:

*What are some basic factors I'd need to consider? Stuff like seasons, weather, climate, yearly and daily cycles, etc.

*Has anyone created a "mega-world" for their RPG?

*Any fiction or non-fiction books that explore this idea? The closest thing I can think of is the SF novel Orbitsville by Bob Shaw, although that's a Dyson Sphere.

*I did find a couple videos on Youtube, but any other resources?

Feel free to share whatever inspires you!

Thanks!
 

log in or register to remove this ad

GuyBoy

Adventurer
Wow....thinking big!

I’m a political historian, not a scientist, so I’ll leave mechanics, seasons, days etc to others, but one thing that strikes me is the question of trade and transport.
Depending on technology levels, trade distances will be so vast that mercantile trades could take a good percentage of somebody’s life (they could take months on our own little globe), so a solution to that, magical or otherwise, would be a priority perhaps?
Communication challenges would also be immense; Prior to the railways and telegaraph, it took around four months for the Tsar’s messages to be relayed on horseback from St Petersburg to Vladivostok. Large empires could be tricky?

You may have found a good basis for Points of Light, with tens of thousands of miles of Howling Wilderness in between.
 

Mercurius

Legend
Wow....thinking big!

I’m a political historian, not a scientist, so I’ll leave mechanics, seasons, days etc to others, but one thing that strikes me is the question of trade and transport.
Depending on technology levels, trade distances will be so vast that mercantile trades could take a good percentage of somebody’s life (they could take months on our own little globe), so a solution to that, magical or otherwise, would be a priority perhaps?
Communication challenges would also be immense; Prior to the railways and telegaraph, it took around four months for the Tsar’s messages to be relayed on horseback from St Petersburg to Vladivostok. Large empires could be tricky?

You may have found a good basis for Points of Light, with tens of thousands of miles of Howling Wilderness in between.
Part of the appeal is the idea that there could exist entirely separate "worlds" (or continents and island chains) that never interact with anywhere else, except through magic (or technology, if SF). Meaning, you could have literally dozens of unique micro-worlds/regions/continents that develop autonomously. That is, if the native species were Earth-like.

Another thought is a grid of magic portals that only an elite mage order controls, thereby controlling global politics and economics.
 


Tun Kai Poh

Adventurer
This is actually an idea I'm playing with for a writing project, but thought the smart folks of ENWorld could offer good advice.

The basic idea--at least relevant to discussion here--is a Jupiter-sized world, but one that is inhabitable by humans.

Some questions:

*What are some basic factors I'd need to consider? Stuff like seasons, weather, climate, yearly and daily cycles, etc.

*Has anyone created a "mega-world" for their RPG?

*Any fiction or non-fiction books that explore this idea? The closest thing I can think of is the SF novel Orbitsville by Bob Shaw, although that's a Dyson Sphere.

*I did find a couple videos on Youtube, but any other resources?

Feel free to share whatever inspires you!

Thanks!
The Warbirds RPG setting, by Steve and Cait Bergeron of Outrider Studios, has a Jupiter-sized world, but rather than solid, it has different gas layers, as well as floating islands which in the Warbirds timeline were mysteriously displaced from the Carribbean region of 1800AD Earth to this new environment. The default setting takes place centuries later, with skyships and air pirates battling it out over the skies of this region known as Azure.


Further revelations in Warbirds: The Space Age indicate that the humans of 1800 Earth, along with many other sapient species from across the galaxy, were all brought to the same galactic neighbourhood in order to start spacefaring civilizations in the same general vicinity and time, as if some powerful advanced power wanted to see them arise and compete...
 

TwoSix

Unserious gamer
I'm assuming a ton of magic is in play here, correct? Since a rocky planet the size of Jupiter is almost impossible, and would have a crushingly high gravity.
 

payn

Hero
You'd need to figure out gravity. A planet 11X the size of earth would explode your heart just trying to move. Though, people would be like the hulk if they could actual live there and then visit an Earth size planet!
 

Galandris

Foggy Bottom Campaign Setting Fan
I wouldn't mind about gravity. Things fall because they are heavy and wet, not because they have this attracting mass nonsense. Once it's out of the way (and frankly, you can't have real life physics and human-like population on such a planet), let's focus on the story. Assuming you want a roughly Earth-like environment on the surface, seas would be immense. And the more sea there is, the more storms a ship is susceptible to meet. You could very well have continents totally out of reach of each others by conventional means. When you mention "cut off areas" on the surface, it's a thing to imagine cultures developping separately in isolation, but you can have that on a regular-sized planet (japan vs europe, say). It would be more varied to imagine whole ecosystems cut off for millions of years and having a totally different bestiary. And a few magically-travelling intelligent species. Perhaps reverting the usual setup of varied cultures and a largely invariant, earth-like fauna and flora, and have a few worldwide cultures (who recently managed to acquire continent-hoping magic) and confronted to adapting to extremely varied environment who evolved segregated for millions of years?
 

Umbran

Mod Squad
Staff member
Some questions:

*What are some basic factors I'd need to consider? Stuff like seasons, weather, climate, yearly and daily cycles, etc.

So, there's a lot to unpack there. What factors you need to consider depend on how much you care about real reality. In a fantasy work, you can just say, "The planet is friggin' huge, and everything else is exactly the same." and be done with it.

The biggest "science" issue is the planet density. Assume the planet is the size of Jupiter. Assume you want a surface gravity equal to that of Earth. Then the planet has to have about 10% the density of Earth, overall, or roughly 0.5 g/cc. Water is 1 g/cc.

So, you need a rocky world that is less dense than water. That's a hard thing to explain, in normal science.

*Any fiction or non-fiction books that explore this idea? The closest thing I can think of is the SF novel Orbitsville by Bob Shaw, although that's a Dyson Sphere.

Robert Silverberg wrote eight books set on the world of Majipoor, which generally fits the description.
 

Mallus

Legend
Read Lord Valentine's Castle for inspiration (the first Majipoor novel). It's fantastic.

Maybe the Big World is an ancient super-science construct; a metal shell with dirt & a biosphere over top.
 
Last edited:

Umbran

Mod Squad
Staff member
Assuming you want a roughly Earth-like environment on the surface, seas would be immense.

Not necessarily true. Your seas can be the same size as our seas. You just have more continents, the same size as our continents.

And the more sea there is, the more storms a ship is susceptible to meet.

If you have seas much larger than those found on Earth, shipping between continents becomes largely impossible without magic. The size of the vessels is limited by the building materials (in our case, wood - fantasy worlds generally lack the metallurgy to make metal-hulled ships). The crew size of a sailing vessel is determined by the ship size. The crew needs food and fresh water, and you reach a point where the ship cannot carry cargo, because the hold is taken up by the food and water the crew needs for the journey.

So, you'd have to either replace the crew with magic, power the ship by something much more potent than wind, or you need people on board who can Create Food and Water every day. They are the most important person on the ship, as everyone dies without them. End results - the captain of long-haul shipping needs to be able to create food and water for the entire crew, every day. If the captain can't do it, then the spellcaster who can will be able to lead mutiny with alarming success.

This issue goes away if you keep the size of the seas down to something Earth-like.

You get similar issues with super-big continents - their interiors are impassable desert.
 
Last edited:

MarkB

Legend
So, there's a lot to unpack there. What factors you need to consider depend on how much you care about real reality. In a fantasy work, you can just say, "The planet is friggin' huge, and everything else is exactly the same." and be done with it.

The biggest "science" issue is the planet density. Assume the planet is the size of Jupiter. Assume you want a surface gravity equal to that of Earth. Then the planet has to have about 10% the density of Earth, overall, or roughly 0.5 g/cc. Water is 1 g/cc.

So, you need a rocky world that is less dense than water. That's a hard thing to explain, in normal science.
A good excuse to include a Hollow World setting, though - again, if you don't mind using some magic to explain why it doesn't collapse.

One thing with a setting like this, you might have a lot more societies who believe the world is flat, because you'd need to get a lot further from it to see any curvature, and the horizon would be a lot further away at ground level.
 


Umbran

Mod Squad
Staff member
One thing with a setting like this, you might have a lot more societies who believe the world is flat, because you'd need to get a lot further from it to see any curvature, and the horizon would be a lot further away at ground level.

Indeed - in fact for many practical purposes, the world IS flat.

When the world gets very large, you probably don't see to the physical horizon. While air is mostly transparent for short distances, eventually the haze of atmosphere will obstruct vision.
 

Galandris

Foggy Bottom Campaign Setting Fan
So, you'd have to either replace the crew with magic, power the ship by something much more potent than wind, or you need people on board who can Create Food and Water every day. They are the most important person on the ship, as everyone dies without them. End results - the captain of long-haul shipping needs to be able to create food and water for the entire crew, every day. If the captain can't do it, then the spellcaster who can will be able to lead mutiny with alarming success.

This issue goes away if you keep the size of the seas down to something Earth-like.

What you see as issues, I see as great opportunities for storytelling something really idiosyncratic to the settings' assumptions. If I was designing something like "jupiter world" I'd want this characteristic to permeate the world. Nearly impassable huge seas, where trade for exotic supplies is contested between the Astronomer's guild who operate magical portals, maybe keyed to moon magic (there are so many of them after all), so they locate where they appear and not create them) and the intrepid Mariner's guild, who know the secret of calling forth miraculous food, sounds... fun.
 

Umbran

Mod Squad
Staff member
A good excuse to include a Hollow World setting, though - again, if you don't mind using some magic to explain why it doesn't collapse.

So, pumice stone is less dense than water. However, it isn't known for its structural integrity or resistance to erosion. Yoru seas would quickly (on geological timescales, anyway) erode their way down into the interior of the planet.

You could imagine a world that's got a core of ice, but that's not sufficiently less dense to explain the world, and gravity pressure would tend to heat the ice, causing melting, and collapse.

So something indistinguishable of magic is probably required.
 

Umbran

Mod Squad
Staff member
What you see as issues,...

You are mis-characterizing my point.

These are issues FOR NORMAL SHIPPING, not for the general concept of the world. As in, "if you use normal Renaissance-Earth-like shipping on a world with giant seas, one of your players is apt to see holes in it." I am making an argument for the need for novel shipping solutions, if you have those huge seas.

I would suggest NOT having any one solution that could reliably span the actual entire world, because that leads to gigantic power-bases by those who control that one solution, and the domination of their culture over the world, which is defeating the point..
 

dragoner

Dying in Chargen
This is actually an idea I'm playing with for a writing project, but thought the smart folks of ENWorld could offer good advice.

The basic idea--at least relevant to discussion here--is a Jupiter-sized world, but one that is inhabitable by humans.

Some questions:

*What are some basic factors I'd need to consider? Stuff like seasons, weather, climate, yearly and daily cycles, etc.

*Has anyone created a "mega-world" for their RPG?

*Any fiction or non-fiction books that explore this idea? The closest thing I can think of is the SF novel Orbitsville by Bob Shaw, although that's a Dyson Sphere.

*I did find a couple videos on Youtube, but any other resources?

Feel free to share whatever inspires you!

Thanks!
Vance's "Big World" and Banks' "Matter" both have larger planets, Vance's is less density (metal poor iirc), while Banks' is a Shellworld, which to me is the better idea: Shellworld - Wikipedia

However, there is the idea of a small dyson sphere built around a white dwarf, which is also interesting, as it is powered, and warmed from the inside, and would have acceptable gravity on the outside: [1503.04376] Dyson Spheres around White Dwarfs
 

doctorbadwolf

Heretic of The Seventh Circle
I'm assuming a ton of magic is in play here, correct? Since a rocky planet the size of Jupiter is almost impossible, and would have a crushingly high gravity.
Well, it might simply not be very dense. That still requires a rather unique framework, but it’s possible.
 

doctorbadwolf

Heretic of The Seventh Circle
Vance's "Big World" and Banks' "Matter" both have larger planets, Vance's is less density (metal poor iirc), while Banks' is a Shellworld, which to me is the better idea: Shellworld - Wikipedia

However, there is the idea of a small dyson sphere built around a white dwarf, which is also interesting, as it is powered, and warmed from the inside, and would have acceptable gravity on the outside: [1503.04376] Dyson Spheres around White Dwarfs
The hollow shell world is what I was thinking. Gaseous core supporting a solid exterior, with seas that are deep from a human perspective but not in comparison to Earth.
 

Level Up!

An Advertisement

Advertisement4

Top