Apologies if this doesn’t fit here, not sure where else to post something like this on lemmy
I think having gravity act like weather might be an interesting concept for a fantasy world, where each country has its own gravity patterns, some tend to be heavier some tend to be lighter, some are all over the place
For a few examples, there could be a desert with gravity so high you can get dragged down into the sand
Could be a country with gravity so low everyone uses personal aircraft that work like bicycles instead of land vehicles
Animals in higher gravity areas would have less dense bones, more muscle, etc and lower gravity would have far larger animals because they can support more weight
In a really high gravity area people might need exoskeletons to prevent long term damage
Instead of wind mills, you could have gravity mills. Pump water into a higher-altitude reservoir on low-gravity days, and let it flow down – turning a turbine – on high gravity days. At least electricity would be cheap.
Or if it varies by region, pump water horizontally (or let it flow slightly downward) from a high gravity region to a low one. Then pump the water upwards there, then horizontally again to the high gravity region. Then let it fall down to turn a turbine that runs all the pumps – perpetual motion (ish)!
Predicting tides becomes hard. Everything is going to be really windy all the time, as the atmosphere expands in low-gravity regions and contracts in high gravity ones. This makes tall buildings impractical, as they would also have to be built for some maximum gravity rating on top of the constant gravity storms.
The oceans would be weird, and violent. Hurricanes might get far more powerful than what we deal with, if the right gravity conditions occur.
For any sort of civilization to emerge, gravity would have to change/vary really slowly. I don’t even want to think of orbits. Kerbal Space Program would be like, really hard in that universe.
Oh man I didn’t even think about atmospheric pressure, could giant windbreakers not potentially be constructed to lessen the effect of this wind?
Or maybe in this fantasy world as it has formed originally with these gravity differences there are lots of natural windbreakers, raised areas and lowered areas, mountains etc due to earth getting compacted to different levels
I would imagine the gravity variance within an area would be fairly mild by comparison to the differences between areas - like how you tend to get warmer temperatures near the equator but can still get variances in temp around that
Oceans may become terrifying but it may be easier to travel by air anyway, instead of trying to travel by ocean you could attempt to plot a course through lower gravity areas and avoid the higher ones Could even spawn some badass hardened sea captains that are required to make certain journeys as they are impossible by air
Well if we are going for science…
Giant constructions will have a lot of wear and tear under varying gravity. On top of that, high winds and frequent storms are likely to weather geographical features a lot, making them more flat. In a fantasy world, you can just magic things away, so that’s fine :)
I don’t know about you, but I would find constant high winds fairly terrifying for air travel. Perhaps they are high enough to permit wheeled sailboats on land? That would be creative!
Wheeled sailboats would be very cool, for air travel could have an airbender-like group, a bunch of monks who dedicate their lives to studying the way the wind changes who can instinctively navigate it and use it to their advantage
Aircraft could essentially just be a hang glider with various mechanisms for steering and best catching the wind
I think if I were writing this as a book I’d have to conveniently ignore/find a way to explain away the wind problem though as it would turn the world from a kind of whimsical interesting place to a deadly, unforgiving one.
I also quite like the idea of low gravs having low tech man-powered aircraft instead of land vehicles and wild wind would make that rather impossible
I quite like the idea of wild wind over the ocean for those air nomad people but that might be a case of wanting my cake and eating it too
I guess if I were going the magical route there could be a group of wizards in every town or city maintaining some kind of force field to keep the wind out, taking it in shifts. Could be a major terrorist threat if someone were able to take them down
I suppose wheeled boats are just… cars with sails? Sailcars? Wind chariots?
Hm, one thing I didn’t think about was magma, if the variations are not so small. Going to have more volcanic eruptions, as fluids get pressed out of high-gravity regions and into low-gravity ones (creating big mountains that grow and tumble into the high gravity wells like some sort of horizontal convection?). Earthquakes too, as the high gravity regions sink and the low gravity ones rise creating shear force. I bet the planet would be more “lumpy” than your run-of-the-mill oblong spheroid. I wonder what continental drift would be like?
With that much irregular magma flow, I bet the magnetic field would be weird if it could sustain one at all. Maybe as ‘cells’ where the eruptions occur in low gravity regions, then gets pulled into high gravity regions where it compresses, heats due to radioactive decay, melts and is pushed back out into low-gravity regions. So maybe you’d have ‘local north’ for the cell? Or a very weak magnetic field overall (yay radiation)? I don’t really know on this point.
Oh and exceptionally high-precision clocks won’t be useful except locally, because of the effect of gravity on spacetime, but that doesn’t seem so bad. Low precision clocks based on pendulums won’t be useful at all! Spring escapements should be fine though.
Maybe it would be better to live underwater?
Wow all of that, and home ownership still seems more accessible there than here. I bet real estate prices are a bargain!
I can’t imagine living under water would be much fun either, I imagine the bottom of the ocean in high grav would be absolutely unlivable due to the pressure
Also, I’m not entirely sure how it works but divers have to come out of the water really slowly and carefully so they don’t get the bends, imagine that where the water pressure keeps changing
Infact imagine any underwater structure where the pressure continuously changes dramatically
Also also the tides would be going absolutely crazy overhead
All that said that would make it even cooler to have some kind of hermit character, maybe a powerful wizard living under the sea despite all the hazards and difficulties
As a mercenary science hermit, I approve.
If the gravity variation was controlled by a super dense material responding to magnetic fields in a weird way then you might have stable-ish conditions at the magnetic poles.
Could lean into the conspiracy theories and say the poles are off limits to regular people and have it as the headquarters for a super elite shadow organisation
Sorry if someone else pointed to this already, but this could be relevant for your story:
“Unlike a body circling a single star, a planet orbiting a pair of stars would have to contend with two gravitational fields. And because the stars themselves orbit each other, the strength of the gravitational forces would constantly change.”
Ooooh and just when I’d kinda given up on a scientific explanation that works rather well
Good idea there
I’m so glad i could help!!
You wouldn’t notice any difference on the surface of the planet, though. The effects of the moon’s gravity on Earth are extreme in comparison.
Wow that would be bound to have some cool side effects. I wonder what the trees would look like
Sounds pretty heavy.
There’s that word again heavy.
Is there something wrong with the earth’s gravitational field?
I think I read your title differently - as in, gravity would ebb and flow like wind or rain or barometric pressure or temperature. In normal days the gravity might be mostly constant, or may fluctuate a few percent as the day goes on, rising and falling over the diurnal cycle. But at times a gravity storm could blow through, causing wild fluctuations from just a few percent (or even reversing!) to a couple hundred percent, causing travelers to lose their un-secured cargo or to be pinned in place until the storm subsides. Locals would know the dangers and have things easily tied down, or beds for riding a gravity storm in relative comfort, but any huge storms people would evacuate, praying that the fluctuations wouldn’t destroy their homes or farms. (And now I’m imagining the end of O Brother Where Art Thou with the cow on the roof)
You read it correctly, that’s what I meant. Both different areas with different gravity patterns but also slight variations day to day like the weather with occasional freak occurances
I think reversal would be rare and restricted to very specific areas
Custom gravity beds would be cool. Personally I’d imagine they’d involve being immersed in some kind of ultra buoyant liquid designed not to cause problems with sustained skin contact
Ergonomic chairs, beds etc would be a must too
I think having people travel between them could be pretty weird. John Carter on Mars showed how going to a low gravity place would have some benefits (he could jump around like a flea). The people living on Mars though thought there gravity was “normal” because they’d always experienced it, however they did have simpler flying machines.
But if a creature traveled to a higher gravity zone they’d just be crushed like a human on the sea floor. Would all these monsters creep from the high gravity places and destroy low gravity civilizations?
Would the borders be sharp? What’s driving the differences? Dense unground metal deposits? Wizards?
I don’t think it’s horrible but there’s a lot to be worked out.
I like the underground ore deposit idea but it doesn’t account for gravity changing
I would imagine the gravity change would be gradual rather than sharp, so you wouldn’t just step over a border and be instantly crushed, they’d have fair warning to turn back
Though I imagine it would be an issue similar to how drastic temperature changes are an issue (for example if someone from Finland went to live in Texas and couldn’t deal with the heat or vice versa)
The animals from higher gravity areas would likely be dangerous, however their bodies would likely have evolved to be far less dense, bones could be broken more easily, they could be pushed around more easily/flung into the air and wouldn’t be well equipped to deal with that
Also, guns would still exist, creatures still wouldn’t be able to easily cross oceans so I imagine to a modern society they wouldn’t be too much of a threat in the same way that gorillas are pretty scary up close but aren’t really a problem realistically
Definitely are a lot of finer technical points to work out which is kind of the point of this post, just interested to explore the possibilities
https://gpg.geosci.xyz/content/gravity/gravity_basics.html
If for some reason the whole planet were made of a less dense material except underneath my house was a massive deposit of gold or lead or something, yes, in reality, that variation in gravity can be measured.
https://bigthink.com/strange-maps/indian-ocean-gravity-hole/
Further reading.
Obviously in your fictional world there has to be a reason tiny anomalies are amped up to eleven. But yes, geology drives gravity variations.
I think the way I’d do it if I were writing a story about this world would be to just not mention the technicalities
Either it’s a medieval level fantasy world where they don’t understand how it works and it’s equivalent to how the sun works or weather works
Or it’s modern day and people generally don’t talk about the finer technicalities the same way people don’t go around casually discussing in detail what causes wind to blow or temperatures to rise and fall
Also, it’s fantasy so it could also just be it works that way because all poweful space cthulu decided that’s how it works
I don’t think your readers would just except that gravity is just smudged across the planet. Sure, some fantasy has iffy rules and little explanation, but something like this smacks more of high fantasy or even scifi.
You don’t need to have a geologist character boring your characters, but some level of lore explaining folke reasons for the variation is going to color your world and sell it.
It will absolutely help to have some hint at an explanation
But if the world is not at the the technological level required to figure it out then it wouldn’t make any sense for them to explain it scientifically
They could perhaps explain it as it is this way because the gods made it this way, or because it’s fantasy it actually could be because the gods made it that way (hence my magic space cthulu comment)
If entering lower gravity areas causes bones and muscle to become less dense, then entering higher gravity areas causes bones and muscle to become more dense. Just look at what happens to those on the ISS after long expose to low g forces. The animals from high gravity areas would likely be shorter, but stronger in musclemass and bone density and/or structure. Higher gravity would also mean higher air density. So maybe the air would be more soupy and difficult to travel through. So perhaps the animals would be more aerodynamic. A stiff beeze would ruin your day!
Ooh interesting point, imagine you go on holiday to a higher gravity area and not only does it become difficult to hold yourself up (might need some kind of protective suit or exoskeleton for tourists to take some of the weight and prevent injury) but also get battered by the wind as you try to move
Would all these monsters creep from the high gravity places and destroy low gravity civilizations?
You’ve just reminded me of a book series I started reading a few years ago. I think it was caused by the Earth having much higher gravity than other planets, but the story was basically humans were super strong. Because of this, they could jump long distances and punch through walls.
I’m going to have to start reading it again, if I can remember what it was called.
Looks like one more reason to read the 3 body problem by Liu Cixin, which is a masterpiece of Chinese sci-fi. I am not gonna tell you anything more, as it’s a spoiler book sci-fi/cycle, and I advise you against reading anything about-it, just read-it
We would have different bones/muscles/joints.
What kinds of differences are you thinking? I’d have thought existing joints would be reinforced, limbs shorter, bigger muscles for high grav or the opposite for low
The dwarves live in high gravity, elves live in low gravity. :O
Lmao yeees would explain why the elves live longer too because their bodies are under less strain
Idk, humans couldnt survive gravity changing all the time. Probably have bones filled with material that changes density with gravity fluctuations.
yeah any sort of large change would kill us in our current form, like less oxygen in the atmosphere killing off a number of larger species in Earth’s past. this world would have to have adaptions like you mentioned.
The expanse goes into some interesting generational changes between people who live on earth, Mars, and in the asteroid belt. Belters are tall and scrawny and when they go to earth they can’t stand and the gravity crushes their bones, extremely painful. The only way they can be there comfortably is in water. I’d imagine different areas with different "weather " would have different types of adaptations and travel wouldn’t be as common/easy.
We already experience this on earth to a degree. The moon causes the tides and shore dwelling ocean creatures have to contend with surviving during the high and low tidal periods. Not really weather per se, but it’s something.
Gravity is also inconsistent across the earth, but to a very limited degree.
Good point, and the tidal currents do affect the weather to a degree. But a massive moon (or four) could be used to explain seasonal or even daily changes in gravity.
Really cool concept, this is like an extreme version of our planet; Earth’s gravity is not uniform, there are variations in the gravitational field due to uneven mass distribution.
Was this planet artificially created? I think a hollow, planet sized structure with a small black hole inside that is off-center could give a very noticeable variation in gravity.
In real world terms it doesn’t really make sense, so you’ll need to dial up the “fantastic” when explaining/handwaving it. Ever read Sanderson? Because he does both “reasonably realistic except X” and “this wind is basically a God, whatever, fuck you” and makes both work pretty well.
Oh yeah I do like a good Sanderson book
My thinking was definitely not a realistic/ sci fi world where everything has an explanation, it was just “gravity is like this because it is” and leaving it at that
Just brainstorming a semi-plausible explanations here. What if the variation is due to massive portals/wormholes to other planets? If you’re standing near one that goes to a place with much higher gravity when it opens up, it could cause you to be pulled toward it, or increase gravity around that area. If these portals are kept secret, the gravity fluctuations as they open and close might appear to be as random as weather patterns.
Could be an interesting plot point too, if your story includes races that have secretly come through these portals. Their existence could be discovered by triangulating the gravity changes during an event. Lots of interesting possibilities.
This actually a real phenomenon.
However, gravity isn’t the same everywhere on Earth. Gravity is slightly stronger over places with more mass underground than over places with less mass. NASA uses two spacecraft to measure these variations in Earth’s gravity. These spacecraft are part of the Gravity Recovery and Climate Experiment (GRACE) mission.
But it’s practically unnoticeable on earth in real terms.
So there could be some sort of super dense mineral in some places. Or basically hollow earth in others.
This isn’t realistic really but you said it doesn’t need to be 100%
The problem with that is it doesn’t account for changing gravity patterns. I think as soon as you explain part of it realistically people ask questions about the rest and that becomes a whole scientific discussion
I’m more interested in the effect it’d have on society, evolution, etc rather than the practicalities of how it could happen in the first place personally
Changing gravity could certainly be explained by super dense mineral clusters. Once you get below the mantel the Earth is essentially a liquid… it isn’t so beyond belief to imagine a world where mantel temperatures are higher and everything below the thin outer crust is fluid… if we then imagine pockets of super dense material with weird magnetic properties it’d be possible for large clumps of that to float through the mantel and cause interesting variations in gravity. Gravity follows the inverse square law so a super density fluid traveling through the upper mantel would potentially cause some really odd effects.
You should read The Three Body Problem by Cixin Liu
Probably pretty dead since you couldn’t have planets with stable orbits.
Variable gravity means its not our universe, So anything is possible.
Maybe the world is on the back of a turtle etc.
I was thinking exactly the same thing, discworld absolutely came to mind thinking about how space might work in this world
Excuse me? Starfield tells me that gravity drives are just around the corner…
If we don’t know what gravity does in this other universe, than talking about variable gravity would pointless.
It is called fiction. They are making it up, the only rules are the ones they decide work for the story.
It can be whatever they want.
See Star wars fighters flying in space like ww2 fighter planes flying in atmosphere.
It can be whatever they want
In fantasy sure. Doesn’t work that well for science-fiction, at least if you want it to be good.
Ah, A Critic!
And one who can judge without actually reading the story.
Impressive skill…
that well for science-fiction
Is Star Wars SF or Fantasy in your world?
I did literally state it was fantasy in the post
Lumpy.
Of course, if this is a fantasy world you’re under no obligation to go with a world held together by self-gravitation, and you can even ignore the weight of air. Believable water is going to want to follow gravity as usual, though, so you need to figure out some sort of crazy hydraulic system to move it around. It could be a backstory for some cool canyons and things depending on what you decide.
More interesting questions might be related to how the residents adapt. I imagine lower gravity areas would be favoured, with groups living in the high gravity areas being specialised. Maybe unpredictable gravity could serve as an energy source for whatever civilisations are in your setting - you balance a very large weight somehow (against a non-gravitational force or a weight somewhere else), and have it work machinery as it adjusts to a new equilibrium. If it changes rapidly enough it might even be useful at small scales, like on vehicles.
More interesting questions might be related to how the residents adapt. I imagine lower gravity areas would be favoured, with groups living in the high gravity areas being specialised.
You could go with the low gravity areas being sought after, and mostly owned by the rich. Homes are much larger, with ‘floating’ rooms, where you can float around in the low gravity, similar to a private pool. The high gravity areas would be for poor people and manual workers, where everything is blocky and small to compensate.
On the other hand, the high gravity areas could be the most popular, as physical strength is valued, and the people living in the high gravity areas have underdeveloped muscles, so need support suits to be able to visit other areas, and are looked down on for it.
If OP could give other basic information about the setting that would be good. I was assuming there’s multiple people groups involved here, but if it’s all one society then yeah, gravity could be connected with class. The exoskeleton thing makes me think they’re leaning more futuristic.
On the other hand, the high gravity areas could be the most popular, as physical strength is valued, and the people living in the high gravity areas have underdeveloped muscles, so need support suits to be able to visit other areas, and are looked down on for it.
Usually culture follows necessity. I think it probably comes down to if the residents of heavy areas are a ruling military elite, or there’s a great deal of civilian mobility between areas which allows a civilian elite to migrate to easier conditions, and leave the dirty work for others.
Low gravity + strong winds sounds like it would wreck everything and everyone. Hurricanes would turn into a disaster situation rather than a mild annoyance. Imagine cars flying around and ramming buildings.
Ooof yeah natural disasters could be way worse.
There could be entirely gravity based natural disasters too, imagine a gravity quake where gravity rapidly changes between high and low and the havoc that could wreak on structures and people’s bodies
Imagine a rare event like asteroid impact rare where a gravity inversion happens over water. A massive volume of water could rise up, arc over, drop onto a densely populated area. Imagine a small ocean falling from the sky onto a city.
In areas where that could happen they may need to build waterproof bunkers/homes
Mechanically, I’d modify the weather table in the DMG:
d20 Gravity
1-14 normal for the season/location
15-17 1d4 × 10 percent lighter than normal
18-20 1d4 × 10 percent heavier than normal
Example: a location that is 200% of normal (all weights doubled) could vary from 160% of normal to 240% of normal.
