World building idea: Jupiter-sized Earth

[Marc_C]

"What is Jupiter's gravity compared to Earth?

Although Jupiter is a great deal larger in size, its surface gravity is just 2.4 times that of the surface gravity of Earth. This is because Jupiter is mostly made up of gases. If you weigh 100 pounds on Earth, you would weigh 240 pounds on Jupiter (assuming you could find someplace to, well, stand)."

Exosuits or augmented bone, muscles and biology. I recall an old sci-fi story in which aliens who evolved in Jupiter are crocodile-like because of gravity. They don't walk upright. They walk on four legs.

 

[dragoner]

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.

Dr Who also had an episode with a pirate planet that teleported around other planets, and stripped them.

 

[MarkB]

"What is Jupiter's gravity compared to Earth?

Although Jupiter is a great deal larger in size, its surface gravity is just 2.4 times that of the surface gravity of Earth. This is because Jupiter is mostly made up of gases. If you weigh 100 pounds on Earth, you would weigh 240 pounds on Jupiter (assuming you could find someplace to, well, stand)."

Exosuits or augmented bone, muscles and biology. I recall an old sci-fi story in which aliens who evolved in Jupiter are crocodile-like because of gravity. They don't walk upright. They walk on four legs.

Yeah, but as stated in your quote, that's because Jupiter is mostly gas. A solid planet the size of Jupiter would have much higher gravity.

 

[Umbran]

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.

This has a major advantage over a Dyson Sphere - gravity.

In a modern Dyson sphere, you have a star (or similar object) in the center, and people living on the inside of a sphereical shell around it. This leaves a big question as to why people (and, say, atomsphere) sticks to the inside of the shell, and not pulled into the star. You need big honkin' gravity generators or something to make it work.

A shell world, however, has people livign on the outside, which makes more gravitational sense.

A shell world, however, is extremely vulnerable to impacts. One biggish asteroid puncturing the shell, and your sea empties into the shell.

 

[Marc_C]

Yeah, but as stated in your quote, that's because Jupiter is mostly gas. A solid planet the size of Jupiter would have much higher gravity.

Correct Captain Obvious.

 

[aco175]

You also need to figure out the cycles of the day. A 24 hour day like Earth may be a problem with things like wind speed and storms being able to travel longer while picking up speed. Typical storms may be hurricane-like. This may be cool to have air ships that are able to ride the wind and transport faster than ground or water shipping.

My 1/day recharge power or slow healing rate would suck.

 

[Mercurius]

Lots of good replies, thanks. I'll re-read them to tease out ideas and considerations.

I think a lot of it comes down to where on the spectrum of scientific realism I want to place myself, with the major demarcations being hard sf, soft sf, and fantasy (with lots of gradations in-between). For my purposes, I'm looking at somewhere between soft sf and fantasy, so issues around gravity, planetary density, etc, don't matter--or at least don't have to be explained (still fun to think about, though).

Actually, this brings up a tangential--but related--issue, which is the question around, what approach to big questions do I want to take? Hard sf tends to take the approach of trying to scientifically explain how something that we normally wouldn't understand works, given our current scientific paradigm. Much of it is written by professional scientists, and all of it by the scientifically literate. For them, the joy is answering those questions, if only speculatively and theoretically.

My preferred approach is more about exploring the mystery, and using it as a context for story. We could call this the "Terra Incognita approach": there are always places on the map that are unexplored and unknown, or cannot be explained by our current tools of cognition, and perhaps imply places off the map. I mean, the horizon always recedes. This is not to say that I don't like coming up with explanations, but that I don't feel beholden to scientific canon, circa 2021.

That said, whatever approach I take, a lot of the same questions can considered. How does the world work? Hard sf, soft sf, and fantasy all have different requirements, yet all do require certain things: internal consistency and some degree of verisimilitude.

For instance, Jupiter has 120x the surface area of Earth. Would the world have continents and oceans that are proportionally the same, or from orbit would it look like countless smaller landmasses and islands? Meaning, would it still have about six major landmasses, three larger than the rest, that are a hundred times as large as our continents, or would it have hundreds of such continents? Or, my likely answer, a bit of both?

And what about life? Would this world have flora and fauna similar in size to Earth, or would it have a wider range, with perhaps gargantuan trees like the theory that the Devil's Tower is actually a primeval petrified tree stump?

Or what about the length of the day? And the range of climate? Etc etc.

p.s. After posting the OP, I did remember Jack Vance Big Planet and Robert Silverberg's Majipoor books.

 

[Mustrum_Ridcully]

This has a major advantage over a Dyson Sphere - gravity.

In a modern Dyson sphere, you have a star (or similar object) in the center, and people living on the inside of a sphereical shell around it. This leaves a big question as to why people (and, say, atomsphere) sticks to the inside of the shell, and not pulled into the star. You need big honkin' gravity generators or something to make it work.

A shell world, however, has people livign on the outside, which makes more gravitational sense.

A shell world, however, is extremely vulnerable to impacts. One biggish asteroid puncturing the shell, and your sea empties into the shell.

A shell world doesn't really sound like somethin that occurs "naturally", so I think some magic or unusual non-realistic physics are bound to exist - maybe there simply are no asteroids like that in this universe, or something that protects the world - maybe the Gods, or some other, more alien supernatural or technological beings.

Maybe one time that protection was broken, and so an asteroid crashed, and there is actually a sea that's slowly but inevitably being drained. Which could be the cause of a big struggle and/or migration. That could be something that's ongoing, or somehting that happened in the past. Maybe someone intervened - gods, mages, engineers - to close the hole again and stop the drain. But in the mean time, land bridges opened up that enabled contact between groups that never had contact before.

I am kinda partial over all to keep the oceans and continents as large as on Earth, I think. That means they are not unsurmountable obstacles by non-magical means, but still really challenging. The different oceans would be seperated from each other (so you could feasibly have a few drained).

Empires spanning multiple continents would still be impractical, unless you have reliable means of magical communication or transportation, since otherwise a revolution on another continent has alread exchanged continental leadership before the leaders of the other continent could respond.

But an interesting question - assuming human migration patterns as they were, but Earth was 11 times larger, but with continents and oceans the same size as now - how far could we have spread until, say, the 5th century or the 15th century? WOuld we have probably populated all continents, or would still some be left alone? How long ago could they have been settled by some humans? Maybe the humanoid species all hail from the first settlers and changed due to the continents they live (be it by evolution, genetic manipulation or magic?). A drain event could be the cause for some recently increased contact between groups that had no contact before.

 

[Marc_C]

But an interesting question - assuming human migration patterns as they were, but Earth was 11 times larger, but with continents and oceans the same size as now - how far could we have spread until, say, the 5th century or the 15th century? WOuld we have probably populated all continents, or would still some be left alone? How long ago could they have been settled by some humans? Maybe the humanoid species all hail from the first settlers and changed due to the continents they live (be it by evolution, genetic manipulation or magic?). A drain event could be the cause for some recently increased contact between groups that had no contact before.

With such a set up another sentient race could have evolved separately from Homo sapiens like in the novel West of Eden by Harry Harrison. Direct descendants of dinosaurs survived and evolved into a bipedal intelligent specie.

West of Eden - Wikipedia

en.wikipedia.org

 

[doctorbadwolf]

This has a major advantage over a Dyson Sphere - gravity.

In a modern Dyson sphere, you have a star (or similar object) in the center, and people living on the inside of a sphereical shell around it. This leaves a big question as to why people (and, say, atomsphere) sticks to the inside of the shell, and not pulled into the star. You need big honkin' gravity generators or something to make it work.

A shell world, however, has people livign on the outside, which makes more gravitational sense.

A shell world, however, is extremely vulnerable to impacts. One biggish asteroid puncturing the shell, and your sea empties into the shell.

Yeah definitely need some kinda solve for that.

Interestingly, IIRC Halo rings from Halo are really good models for Dyson sphere style habitations, because thier spin can evenly and reliable simulate gravity, although stuff will still fall “up” toward the thing you’re in orbit around, so some sort of secondary structure to catch things and people that get yeeted would be a good idea. Theoretically you don’t even have to enclose the ring, but you might as well since you need stuff to not get yeeted into the sun or space, and you’re a bit safer against impacts.

but none of that fixes our eggshell world problem.

is there any gas that water would sit on top of? If such a gas was what fills the inside, you could float seas on it, making a sea that the depths of are a gas that you prolly can’t breath. Scary stuff, but also it’s a fantasy world so what lives in the core?