Flat world, or round?

[Mutazoia]

[Anonymouswizard]

Thank you, but I see enough of that one on Facebook

[Segev]

First time I saw a graphic put to it.

[raygun goth]

See all of these statements run on the assumption that the flattening of the world is the only thing that's changed. That's obviously pretty silly - a flat world requires, by necessity, a totally different set of physical laws and underlying principles. Lunar phases work fine if the moon is a giant, divine eye that slowly succumbs to exhaustion and sleeps for one night out of 29. Eclipses may not happen the regular way, but they can definitely happen when the sun does battle with the serpent of chaos. Night falls when the Sun reaches the Western edge of the sky, gets bored, and parties its way back East on foot. The seasons are the waxing and waning of the five planets, and their relative positions allow for navigation by night. I can go all day with this - the point is that just because a setting's underlying causes follow a mythopoetic logic instead of a more familiar one doesn't mean the setting is noticeably different in matters of day-to-day life.

Thus, my closing statement. Of course it requires a new set of physical laws. I'm a fantasy writer, I am more than familiar with this concept.

And yes, it is different. That's the whole point of making it different. If it isn't going to look different from the ground up, then why would you do it in the first place?

(Also, a bone to pick: trade between Classical Greece and India or China was indirect, not a basic component of everyday life. Yes, currency from one place would end up in the other, but that was because of trade routes, not because the two had any kind of relationship with one another.)

Oh, yes it was. Pepper, both black and red varieties, apples, citrons, almost all dye, cotton, glass, clay, paper, cinnamon, almost everything used as medicine, and tea came from the greater Asia area; contact with the Chinese, Africa, and India were established by the Greeks and almost never went away. It was nearly impossible to turn around in medieval Europe, even in districts full of commoners who'd never left their own street, without seeing something that came from a foreign land. That's not counting the huge influx of goods and information that started happening during the Crusades.

The Greeks had colonies in India; Greek's obsession with yogurt and dill is actually historically difficult to track because a large chunk of the base types of food in greater India and Greece are practically identical. The Greeks were eating miso and egg drop soup. India and South China statuary is based on Greek designs. The physical appearance of Buddha is based on Apollo. These routes continued to be active and regular throughout the Middle Ages. In 1200s Spain you'd be buying your damn silverware and discover "Made in China" stickers. Samurai were a feature of Iberia, because when Japan closed their borders, they wouldn't let an entire clan back in, and there are even people now in Spain with the family name "Japon."

[Xuc Xac]

Wait, do all things always fall at 9.81m/s², irregardless of their mass?

It seems like it. How are you proposing to find out to a more accurate degree than "It's 10ish or so m/s²"?

Also, if I keep teleporting higher, what goes on with the atmosphere? Does the air get thinner and thinner in line with the Standard Atmosphere model, until I'm in vacuum? Is it at constant density all the way up? How does that work?

Which Standard Atmosphere model? Despite the name, it's hardly "standard" because there are several different ones. I would say the air gets thinner as you go up, just like climbing a tall mountain. If you had sensitive enough instruments, you could see that gravity also gets weaker with increased altitude. If you get far enough above the ground, gravity is theoretically reduced to zero. This is probably why stars don't fall (unless they're attached to something up there, which is a competing theory).

Also, what keeps the world together and vaguely planar?

What keeps you together? Are you operating on the assumption that it has to be kept from flying apart like a rotating planet?

All forms of navigation that we know of are only usable if the world is round. Trigonometry with a sextant? Useless. Latitude and longitude? Useless. Planning flights over large distances becomes an enormous headache just due to timekeeping alone, not to mention the weird results this is going to have when anyone tries to chart anything.

All the forms of navigation that you know, not "we". Those examples only work on a round world because they are specific to a round world. You might as well complain that an underwater mermaid campaign wouldn't work because their boots wouldn't fit. In a standard medieval fantasy world, there is no longitude. It's a thing that exists in theory when mathematicians talk about globes, but nobody navigates with it because they can't measure it without really accurate clocks that don't get screwed up by being carrying on a ship that moves around. Nobody plans long distance flights! When is the last time anyone in a D&D game teleported a long distance and felt jet-lagged because the sun was suddenly in a different part of the sky? (If they had the technology to have regular passenger plane service, I'm sure flatworlders would just schedule things with clocks like we do, but it would be simpler because they don't have to deal with time zones.) On a round world, there are many difficulties in making maps and charts of large areas because we have to figure out how to project the round surface onto a flat map. On a flat world, it's easy because the world and the map are the same shape.

A lot of these complaints (time zones for example) seem like they would also apply to a round fantasy setting but the flat world is held to a stricter standard of scrutiny. The party teleports around the world? Nobody notices or cares that the sun just skipped forward or backward several hours. But travel across a flat world and suddenly it's all "but what about...?" It reminds me a lot of the objections to gunpowder in fantasy. "Oh, nobody would use gunpowder because one fireball would blow you up if you carried it!" and yet nobody ever asks if the archer snaps a bowstring no matter how many times he gets roasted by fireballs and dragon breath. When something is different than the usual standard, they look a lot more closely for problems. That doesn't mean there are really more problems. It just means that they are looking harder for them.

The calendar is borked; you have to invent a completely new calendar because seasons don't operate the same way anymore, either.

We live on the same planet with the same axial tilt. Guess how many calendars have been used in history. How many different calendars do you think are being used right now? On a flat world, maybe seasons work differently or maybe they do work the same way. They just don't have the same cause. Instead of axial tilt to the sun, it could be something mystical: "The far north is perpetually cold and frozen around the palace of the god of ice. To the far south, the land is scorched around the palace of the goddess of fire. They constantly struggle to force their dominance over the world. The ice lord pushes his power south, which causes winter, until he gets pushed back by the lady of fire in the spring. When she pushes farther north, it gets really hot for the summer, until the ice god forces her back in the autumn." I could make up mystical seasons all day and there's no reason to stick to summer/autumn/winter/spring cycles.

Basic, day to day life is effectively drastically altered. It should be remembered that even in the time of the Greeks, trade with China and India were basic components of daily life, and it should be so with a fantasy world, as well - no kingdom exists in a vacuum. It trades with its neighbors and even the far-flung reaches of the world. Are there potatoes? Tomatoes? Chili peppers of any kind? How did anyone navigate the damn ocean if stellar navigation doesn't work

If you mean the modern Greeks, they use GPS just like everyone else. If you're talking about the ancient Greeks, they didn't navigate the ocean. They sailed along coasts or sent caravans over land. Potatoes, tomatoes, and chili peppers have nothing to do with the shape of the world. They came from "somewhere else", but nothing about that "somewhere else" depends on the world being round. The ancient Greeks were big fans of bronze and used a lot of it. They got tin from Britain. Do you know how to find Britain from Greece by boat? Sail along the coast with the land on your right until you see the White Cliffs of Dover across the water on your left. To get back to Greece, just turn around and follow the coast back the way you came.

(moving away from an object in parallax on a flat surface results in varying angles of inclination of that object, you can't use any fixed points in the sky because there aren't any on a flat world)? You could also see the sun from anywhere on it, because there's nowhere for the sun to go, and solar inclination is another method by which navigators guide themselves and measure seasons.

Why would they not be fixed? On a round world, stars appear fixed relative to each other (planets are named "planets", meaning something like "wanderer", because they appear to move relative to the other stars. The field of stars appears to rise and set as the Earth rotates. On a flat world, there can still be stars in the sky but they probably won't rise and set. If the stars are really far away, you wouldn't be able to move far enough to get out from under the ones directly over head or change which ones are near the horizon. Instead of saying things like "when the sun goes down, watch for the dog star and mark the point where it rises, because that is East by Southeast", they could just say "the dog star is east by southeast" because stars don't rise and set in the sky.

How do you know there's nowhere for the sun to go? That's one of the questions that needs to be answered for a flat world. How does sunrise and sunset work? Is the world finite in size and the sun goes over it in the day and under it at night? If the world stretches out to infinity, how does the sun work? Does it rise out of a hole, travel across the sky for a day, then drop into another hole to travel back to the beginning? Is it always nighttime outside of that narrow path? Is the sun actually an endless series of suns that travel across the sky one day apart? It doesn't depend on the world being flat. The important thing is how big the world is and whether or not it has an edge.

If you can't use stars, you can still navigate by landmarks, which are a lot more useful on a flat world if there are mountains around. At sea, you could still use all of the Polynesian tricks that weren't based on stars. Some Polynesian techniques are very clever tricks, such as using hydrophobic birds as aerial spotters (if you let the bird go and it can see land from up in the sky, it will fly that way, otherwise it will land back on your boat). Other techniques just seem like sorcery, like recognizing places at sea by the shapes of the waves or recognizing distant islands by the color of the clouds floating over them. If you made that up for a work of fiction, people wouldn't believe it because it sounds too fantastic.

There are a lot of ways to navigate that don't rely on a simple coordinate system. I've seen medieval maps of Italy that were just shaped like a U, because they didn't map the shape of the country. They just listed which town is next if you move up or down the coast. A flat world version of medieval Italy would probably have much more accurate maps because they would be able to see the mountains as a landmark.

So should seasonal travel and religious holidays. These things are all affected and need to be accounted for.

Seasons aren't caused by roundness. You could have a round world with no axial tilt and a 413 day year, which would screw up the Gregorian calendar and have no seasons. Religious holidays might use an arbitrary calendar that doesn't care about seasons or leap years. Some churches in the real world still use the Julian calendar and celebrate Christmas in January because their leap years didn't accurately correct for the length of a solar year and they're now two weeks behind. I've lived in places with four distinct seasons and places with only two (and I've visited places that had three). All those places are on this same round planet.

There ain't no moon phases no more.

That depends on several factors unrelated to the flatness of the world:
Is there a moon? What shape is it? The sun and moon can still be spheres that move around the flat world and eclipse each other. How is the moon illuminated? Does it reflect sunlight or does it produce its own light? Moon phases could be the result of a rotating spherical moon that only produces light on one half of its surface. When deciding the shape and size of the world, you also have to decide the shape and size of everything else. That's probably better quality world-building than just assuming there's a moon just like Earth's because you assume "everything is the same except magic".

Cultures living on a flat world, of course, would have "grown up" on it and might have answers to this, and if you're going to flatten the world, you should worry about this stuff.

You should worry about this stuff no matter what shape the world is.

I live in Florida. It cannot get any flatter than this. Kansas is straight up jagged compared to Florida. But we have a big sandbar structure running through the center of the peninsula. If I was in Clermont, I would be able to see Zephyrhills and Tampa on a flat Earth.

From Clermont, you could actually see the tops of the high rises in Tampa now on a round Earth if there weren't trees in the way. 100 North Tampa is tall enough that you could see 29 miles to the horizon from the top floor (if there were nothing blocking the view to the horizon) which is 7 miles past Clermont. You still can't see it from Clermont because there are trees between them. The trees are much shorter but they're also much closer and fill more of the field of view. If Clermont had highrises too, they could see each other.

Edit: No, that's wrong. I was thinking of Clermont to Orlando. Looking from Clermont to Tampa, the biggest building at 100 North Tampa would be just under 0.09 degrees. Big enough to see with the human eye but small enough that it would blend in with everything else on the horizon. You could probably see a bright beacon blinking on the top at night though.

If you're looking from a tall tower in our world you can probably already see cities roughly that far away. The main difference is that they do not disappear when you go down. I bet in a flat world you could find a spot on or close to the ground in the Netherlands where you could clearly see the cities of Amsterdam, The Hague, Rotterdam and Utrecht. Sure, those are only about 55 km apart, but it's still something you couldn't do today.

But then the fun starts. Objects a few hundred meters in size are visible from a few hundred kilometers away. The Ardennes mountain range in southern Belgium sits about 175 km from my house. I bet there would be at least one clear line of sight from my tenth floor window to those. I could see mountains from my house. (Mountains are a lot wider than they are tall of course, but similar to how you can't really see the great wall of China from space and how roundworms can be close to a millimeter in length but still invisible to the human eye, it's the smallest dimension that counts.) And on a very clear day it gets better, because to the side of the Ardennes, speaking from my view, sit the Alps. They're 550 km away, but they're also several kilometers high, meaning they're not just visible, but pretty clearly so. like a mouse at several meters away, rather than an ant. The Scottish Highlands sit around the same distance in the other direction, with a lot of the space in between being sea. I'd probably be able to see those, if I can find a north facing window to look out of.

You can see about 35km from the top of the Maastoren in Rotterdam. The tallest peak in the Alps is 4810m above sea level. If you were at sea level and had an unobstructed view of it from 550 km away, it would be half a degree of arc tall. That's about how big the sun and moon appear to be from Earth and about half the width of your little finger held out at arm's length. However, it's too far to see through the atmosphere. Rayleigh scattering (what makes the sky look blue) sets an upper limit of about 296 km through air. When you get close enough to see the Alps through the blue haze of the sky, the tallest peak would be close to 1 degree of arc. If you're within 3 km of a tree, you won't see the Alps over it at that distance. It doesn't take a lot to block the view, but looking across the sea would be impressive. In the real world, you can see across the narrow part of the English Channel. On a flat world, you could (just barely) see across the wide end too.

If you want to, you can calculate the apparent size of objects with trigonometry (or use an online calculator like http://www.1728.org/angsize.htm). Just find the angle between the top and bottom (or sides) of the object to see how much of your field of vision it would take up. The smallest things humans can see are about 0.02 degrees. Things get smaller with distance and disappear when they are smaller than 0.02 degrees (and they get really hard to see long before that). Everything disappears once it gets past the limit of light scattering in the air (296 km under ideal conditions and much less if the air is humid/dusty). Red light can travel further than blue so light sources that are bright enough to be seen from that distance will turn red before they vanish.

[pwykersotz]

Stuff

A magnificent post. Well said.

[Mechalich]

Look, it is entirely possible to build a setting with weird physics and to take those physics seriously. However, unless you are an actual physicist and a pretty darned careful you are likely to get something dramatically wrong and have left in a massive plothole. In a novel that's an 'oops!' in a TTRPG that's a potentially game-breaking problem. If you choose to have a crazy-wild set of physics in play, you're going to have to spend an immense amount of time working on them and trying to get them correct enough to maintain verisimilitude. There's two very substantial consequences to that: first, time spent on the physical world-building is time not spent on cultures, history, or themes. Second, the weirdness of your world-building has a tendency to overwhelm your storytelling, since it may require thousands of words to explain how the heck everything operates now. In a novel this can be derailing to the story. This is a common objection regarding the works of Greg Egan - who basically does weird physics as a career path - in that his stories devolve into weird math problems you, the reader, do not care about and that overwhelms the drama. In a TTRPG this can simply prevent your game from happening because the several pages of material needed to make the characters understand how your bizarre world works in the most basic way simply will not be read and if your game happens at all the players will not understand the implications. The test case here is Exalted. That game would be much better if Creation was simply a normal spherical world and the Wyld emerged in remote areas, it would be less complicated and not have stupidly huge ocean and desert distances and confusion about how seasonality works.

Having a flat world carries costs to any and all games set on it. The benefits it provides are minimal any story a TTRPG is capable of telling that takes world-building seriously. It is not worth it.

Important: that calculation is not the same as for narrative production. A truly bizarre backdrop that functions according to its own special rules might be essential for a particular narrative vision even as the world produced is remarkably ill-suited for a game. The Exalted example is once again telling. Tales from the Flat Earth is a particular set of novels invoking a particular form of mythic despair and horror. They make for worthy literature, but if you actually read them, thinking 'this would be a great setting for a game' is the last response that should come to mind.

[Milo v3]

The test case here is Exalted. That game would be much better if Creation was simply a normal spherical world and the Wyld emerged in remote areas, it would be less complicated and not have stupidly huge ocean and desert distances and confusion about how seasonality works.

I think many people would disagree with this (myself included).

[Max_Killjoy]

Look, it is entirely possible to build a setting with weird physics and to take those physics seriously. However, unless you are an actual physicist and a pretty darned careful you are likely to get something dramatically wrong and have left in a massive plothole. In a novel that's an 'oops!' in a TTRPG that's a potentially game-breaking problem. If you choose to have a crazy-wild set of physics in play, you're going to have to spend an immense amount of time working on them and trying to get them correct enough to maintain verisimilitude. There's two very substantial consequences to that: first, time spent on the physical world-building is time not spent on cultures, history, or themes. Second, the weirdness of your world-building has a tendency to overwhelm your storytelling, since it may require thousands of words to explain how the heck everything operates now. In a novel this can be derailing to the story. This is a common objection regarding the works of Greg Egan - who basically does weird physics as a career path - in that his stories devolve into weird math problems you, the reader, do not care about and that overwhelms the drama. In a TTRPG this can simply prevent your game from happening because the several pages of material needed to make the characters understand how your bizarre world works in the most basic way simply will not be read and if your game happens at all the players will not understand the implications. The test case here is Exalted. That game would be much better if Creation was simply a normal spherical world and the Wyld emerged in remote areas, it would be less complicated and not have stupidly huge ocean and desert distances and confusion about how seasonality works.

Having a flat world carries costs to any and all games set on it. The benefits it provides are minimal any story a TTRPG is capable of telling that takes world-building seriously. It is not worth it.

Important: that calculation is not the same as for narrative production. A truly bizarre backdrop that functions according to its own special rules might be essential for a particular narrative vision even as the world produced is remarkably ill-suited for a game. The Exalted example is once again telling. Tales from the Flat Earth is a particular set of novels invoking a particular form of mythic despair and horror. They make for worthy literature, but if you actually read them, thinking 'this would be a great setting for a game' is the last response that should come to mind.

If these forums EVER needed the ability to upvote posts, it's right now, for this post right here ^.

[Milo v3]

In a TTRPG this can simply prevent your game from happening because the several pages of material needed to make the characters understand how your bizarre world works in the most basic way simply will not be read and if your game happens at all the players will not understand the implications.

Wait, wouldn't that mean it'd take years to play something like any official D&D setting considering how basically everything in it goes against physics and biology and how everything in it is made from supernatural elements rather than real world ones, how life works is determined by positive energy rather than biological signs, how there is perpetual motion, how there are liquids like holy water which have negative weight, where there are solid objects made of Nothing, how giant lizards made of crystals with mind powers which can breath out "Cold Energy" can interbreed with a gelationous cube, forms of vision which require no actual light, where physical locations can be sentient, where the physics of other realms can overlap and take over, where time travel exists, where darkness is an actual thing rather than a lack of light, where there is whole planes of existence where basically everyone can teleport an infinite distance at their whim, where magic comes from special radiation called the weave, where Acid and Cold is a friggin energy, where bases are Acidic, where you can have creatures made from solid evil, etc.

The amount of magical stuff which should require an explanation in games like D&D is immense, and based on what you've said apparently attempting to play in such a world would require a massive amount of text to explain all of this away and then probably contradict itself because of how much it has to explain of it's own unique physics. But people all over the world are still able to play D&D.

[golentan]

It's a game. There's a measurable cost to using real world physics too vigorously, even in straight sci fi games like my beloved traveller. That's what caused the catgirls meme in the first place, and a quick perusal of various optimization or weirdness discussions for games will reveal the idiotic things you can do through the application of real world monatomic substances or engineering or what have you.

Damage is measured not in kinetic energy, or in permanent organ degradation and scar tissue, it is measured in dice, and applied by weapons and removed by various healing methods, the most mundane of which cause my medical soul to growl with envy at their effectiveness.

It is a game. It requires some amount of suspension of disbelief, and some amount of opt-in on the game being played, and some amount of agreement not to break it. The real world's rules are not special, not somehow immune to requiring suspension of belief when translated into a game governed by dice and minds.

And I disagree creation would be better as a globe.

[CharonsHelper]

Wait, wouldn't that mean it'd take years to play something like any official D&D setting considering how basically everything in it goes against physics and biology and how everything in it is made from supernatural elements rather than real world ones, how life works is determined by positive energy rather than biological signs, how there is perpetual motion, how there are liquids like holy water which have negative weight, where there are solid...

Those aren't different rules of physics.

Physics works pretty much the same as in our world, there are just a lot of different magic things which can break those rules. Because magic!

[Cluedrew]

You know I just don't understand why people say that the physics have to be worked out so much to avoid plot holes. The idea has been forwarded several times but I don't think it has ever been explained. If someone has a good explanation for it please share it.

As I see it, it is unlikely to matter. If you are playing a game about scientists in a sci-fi or modern setting it might matter. But a lot of times, society doesn't understand the inner workings of the universe well enough for them to actually be knowable by the characters anyways, and if they are the characters probably haven't studied them that well anyways.

So that leaves only the day-to-day interactions, the surface, open for observation. That's all that should have to hold up. Even if the "laws of physics" behind them would be involve 10 fundamental forces, properties of matter that change due to sub-atomic changes and a boat load of special cases on top of that what does it matter?

Is the game suddenly not fun when you haven't named every turtle in the stack? Anything beyond what will come up in the game (maybe a bit beyond that for safety or for fun) shouldn't be detailed, because it will never come up and hence, how could it matter?

[2D8HP]

All forms of navigation that we know of are only usable if the world is round. Trigonometry with a sextant? Useless. Latitude and longitude? Useless. Planning flights over large distances becomes an enormous headache just due to timekeeping alone, not to mention the weird results this is going to have when anyone tries to chart anything...

Since getting lost is an adventure, lack of ability to navigate sounds more like a feature than a bug.

Let me try and take my DM horned helmet off, and think like a player

.....

Didn't work.

I just don't think "shenanigan" enough.

I just don't try to act out Lest Darkness Fall scenarios.

I know there's precedents in fantasy literature (Fafhrd putting rockets on his skies in The Snow Women), and definitely in RPG's, but the kind of inventiveness of say @Anonymous Wizard just doesn't come to me.

So a flat world just doesn't bug me.

I seek wonder in the setting, I don't wonder how to break the setting.

Not that there's anything wrong with that.

Fantastic worldbuilding is so much more easier, fun, and interesting than realistic worldbuilding

[Xuc Xac]

Look, it is entirely possible to build a setting with weird physics and to take those physics seriously. However, unless you are an actual physicist and a pretty darned careful you are likely to get something dramatically wrong and have left in a massive plothole.

That's not a "flat world" problem, that's just a "world" problem. I remember someone once asked in a forum post "How much would a gem of this size and weight be worth? I just made it up for my players to find but now they want to sell it." The answer turned out to be "It isn't worth anything because at that size and weight, it's apparently made of styrofoam." Even G.R.R. Martin was apparently shocked when he saw the set design for "Game of Thrones" and realized that he had made the wall much too big.

On the other side of the GM screen, players who don't think things through might think something is a plot hole when it isn't.

Since getting lost is an adventure, lack of ability to navigate sounds more like a feature than a bug.

Yes. The downside to things like teleportation, air ships, or really good sea navigation tools and charts is that you can go straight from point A to point D without having to adventure your way through B and stop to ask directions in C. All that cool geography stops being important.

[LordCdrMilitant]

It seems like it. How are you proposing to find out to a more accurate degree than "It's 10ish or so m/s²"?

Which Standard Atmosphere model? Despite the name, it's hardly "standard" because there are several different ones. I would say the air gets thinner as you go up, just like climbing a tall mountain. If you had sensitive enough instruments, you could see that gravity also gets weaker with increased altitude. If you get far enough above the ground, gravity is theoretically reduced to zero. This is probably why stars don't fall (unless they're attached to something up there, which is a competing theory).

What keeps you together? Are you operating on the assumption that it has to be kept from flying apart like a rotating planet?

By teleporting high enough. Greater Teleport has no maximum range and no error chance, and Planar Adaptation can specifically allow me to survive in vacuum, so I can determine at the very least that gravity does, in fact, fall off with altitude. Then, I can bring with me an immovable rod of known length, and measure the time it takes for objects of known mass to travel the length of the immovable rod, thus allowing me to determine their net acceleration. There will be some minor error due to air friction, but it is fairly negligible over the low speeds and distances.

ISA.

[Mechalich]

That's not a "flat world" problem, that's just a "world" problem. I remember someone once asked in a forum post "How much would a gem of this size and weight be worth? I just made it up for my players to find but now they want to sell it." The answer turned out to be "It isn't worth anything because at that size and weight, it's apparently made of styrofoam." Even G.R.R. Martin was apparently shocked when he saw the set design for "Game of Thrones" and realized that he had made the wall much too big.

On the other side of the GM screen, players who don't think things through might think something is a plot hole when it isn't.

G.R.R. Martin is bad at math and a bunch of other things. That the wall was way to big was obvious to many readers (myself included) from the get-go. More relevantly: snow causes crop failure, ergo, 'summer snows' mean the North is incapable of supporting an agrarian society.

The thing is, the level of changes Martin introduces at the world scale were small, extremely long seasons (highly plausible) and seasonal irregularity (less so) are small change in the scale of potential weirdness, much smaller scale than the kind of changes your talking about if you go for a flat world.

Committing to a flat world means that, as a world-builder, you are saying 'I'm going to make a fantasy world that behaves massively different from the Earth from first principles and when I run into any trouble I cannot default back to baseline conditions at all.' That's a Nintendo Hard problem.

You're never going to get everything right in world building, nobody's perfect, and readers and players will be required to mind caulk together a set of rationalizations to plaster over the errors. However, the more changes you make and the more bizarre your setup is, the less likely it will be for that mind caulk to hold together, especially across multiple tables. Committing to a flat world means taking on a massive additional burden in this regard for minimal benefit.

Note: this doesn't apply if your setting is not intended to retain verisimilitude at all and has gone full-on surrealist. That's certainly a thing you can do and it can be awesome, but doing that has its own set of consequences.

[Xuc Xac]

Then, I can bring with me an immovable rod of known length, and measure the time it takes for objects of known mass to travel the length of the immovable rod, thus allowing me to determine their net acceleration. There will be some minor error due to air friction, but it is fairly negligible over the low speeds and distances.

Here's your clock:


It has an hour hand. I don't think air resistance over the length of your immovable rod will be the biggest source of error.

[5a Violista]

Here's your clock:


It has an hour hand. I don't think air resistance over the length of your immovable rod will be the biggest source of error.

So you're basically saying that hourglasses, magically-regulated time-keepers (Many spells do last for an exact multiple of 6 seconds in certain interpretations of D&D, after all), pocketwatches, pendulums, springs attached to gears, mental clocks that allow people to count out time, etc are all incapable of existing in flat worlds? Or are they merely desynchronized whenever they go through some sort of teleporting spell?

Because if teleporting messes up all timekeeping equipment, that would be pretty neat and have interesting cosmological implications.

[ImNotTrevor]

This all assumes a world that runs on Realworld Scientific Principals and that can be explained through such.

I usually get around this by giving answers that actively oppose one another when people start poking, or observations that could not possibly exist. Or I just stare at them and tell them to put away the physics textbook so we can play.

A world that runs on Mythopoetic theory functions just fine so long as it is internally consistent in its logic, flatworld or no.

Allow me to worldbuild real quick:

Tyr is a great disk floating in Void, one of many such disks that fill Void. Around the disk moves Tuva, known also as The Father Star. His wife, Lyrian, also moves around the disk as Mother Moon. The two gods give life to Tyr as it tumbles through Void.

Tyr is a disk because Creation, at his birth, had only so much clay to give. So he shaped his worlds into disks and cast them into Void. With each disk, Creation left a touch of himself upon it. Tuva, Father Star, is a Son of Creation.

Tuva looked down upon his great clay disk and decreed that it should be beautiful. So he set forth to shape it, pulling up mountains and pushing down riverbeds and canyons. His salty sweat became the oceans and rivers. The blood of his blisters became the mud and soil. The broken pieces of his toiling fingernails and tools became the ores in the earth. He allowed Tyr to thrive for a time, but became lonely. He made himself a bride. From the softest petals he made her lips. From the most precious sapphires he made her eyes. From the north wind came her breath, and her skin woven from the finest silk. And as he gave her the spark of his life, he spoke her name: Lyrian.

----

I could go on but I needn't. This world runs on Myth, not Logic. The answers to its questions will come in the form of parables and tales.
"The sky is blue because old Mata the trickster painted it that way to fool his brother Kingat."
And that's why.

For pretty much any question of how a thing works, there is probably a story about it. And the stories may not be consistent (Myths rarely are. Vocal tradition, etc) but the consistency lies in that natural phenomena are, 99% of the time, the result of gods or demigods screwing around.

To quote a part of Moana, "I killed an eel, buried its guts, then grew a tree now you've got coconuts."
That's where coconuts come from. Maui killed an eel, buried its guts, and a coconut palm grew. Because that's what happened.

Make it doubly fun by letting players who make high knowledge rolls tell their own little story about who or what made the thing how it is. (At least, I would find that really fun.)

There's no reason you can't have a world that runs on this logic, so long as everyone agrees that Mythopoetic explanations are just as fun as Emprical ones, just for different reasons. (And yes, I have a world with enough gods and demigods to make this a reality and have their behaviors be consistent with their characters.)

[Xuc Xac]

So you're basically saying that hourglasses, magically-regulated time-keepers (Many spells do last for an exact multiple of 6 seconds in certain interpretations of D&D, after all), pocketwatches, pendulums, springs attached to gears, mental clocks that allow people to count out time, etc are all incapable of existing in flat worlds?

They do exist. That's how you measure as accurately as "it's about 10". My question was how he planned to get a more accurate measurement than that. By the way, pocket watches also lack a minute hand until well into the modern period. If you want to play medieval scientist, you get medieval tools.

[LordCdrMilitant]

They do exist. That's how you measure as accurately as "it's about 10". My question was how he planned to get a more accurate measurement than that. By the way, pocket watches also lack a minute hand until well into the modern period. If you want to play medieval scientist, you get medieval tools.

That clock is good enough to tell me gravitational acceleration is less at ten-thouand kilometers altitude than it is at ten kilometers altitude.

[Fiery Diamond]

You know what I don't get? "The game world is assumed to be as our world except plus fantasy as noted." That... isn't even remotely how I handle fantasy worlds. "The world is assumed to RESEMBLE our world except as noted (or assumed) to function differently for reasons including magic and ease of playing." That's my starting point. Any fantasy world isn't assumed to have "real-world physics, except as noted," it's not even assumed to have "a different set of physics." It's assumed that physics, as we understand it, does not exist. The world may resemble ours in various ways, but the underlying reasons it functions that way are assumed to be NOT THE SAME as our world, and furthermore, those underlying reasons are assumed to not matter unless they're relevant to characters or story.

So the whole "a flat world would function in a specific way" bit is completely nonsensical from that standpoint. Why are you even assuming vision works by reflected light rather than, say, something in our eyes going out and seeing things (an actual historical theory) or something even more fantastical?

I would never game with someone who started from a different starting assumption.

ANYWAY...

I gamed with a world a made that was a cylinder. The game map was the surface of the cylinder. The "ends" of the cylinder were special locations where time and space got all wonky and no-one ever returned after voyaging to. Embedded in the crust of the world were "climate nodes" that controlled the local weather. The interior of the cylinder was a distorted space that made up the elemental planes. The cylinder spun around with the sun stationary on one side (and actually was its own plane of the sun god) with the moon (also a plane of existence) on the other. Gravity on the cylinder was always defined as "toward the nearest point of contact with the elemental planes" (which was always what the people would see as straight down). Seasons existed because of the climate nodes, so some places had all four seasons, some had fewer, some had wonky seasons that went through multiple irregular cycles within a year, and so forth.

[Mutazoia]

You know what I don't get? "The game world is assumed to be as our world except plus fantasy as noted." That... isn't even remotely how I handle fantasy worlds. "The world is assumed to RESEMBLE our world except as noted (or assumed) to function differently for reasons including magic and ease of playing." That's my starting point. Any fantasy world isn't assumed to have "real-world physics, except as noted," it's not even assumed to have "a different set of physics." It's assumed that physics, as we understand it, does not exist. The world may resemble ours in various ways, but the underlying reasons it functions that way are assumed to be NOT THE SAME as our world, and furthermore, those underlying reasons are assumed to not matter unless they're relevant to characters or story.

Except that you do assume that the standard laws of physics (except as noted) apply in a fantasy world. Do you REALLY want to have to sit down to pick and choose what laws apply and what laws do not? We can assume gravity works just like it does in the real world, unless you specifically want to play in a world that has zero-g year 'round. Then you specifically note that there is no gravity.

We assume up is up and down is down, that fire is hot, that we need light to see (unless you have Infra-vision or other specially noted vision mode), that when we swing a sword, it's not going to crumple like tin-foil, when you drop something, it falls down, not up or at an angle (unless you drop it mid swing, then the laws of physics apply again) or dances a jig....I could go on, but I'm sure you get the point.

Even magic follows the laws of physics. Cast a 30' radius fire ball in a 10 x 10 x 30 corridor, and see what the rules say happen...yup, the blast follows the laws of physics. How the blast is generated is an exception as noted, but the end result still obeys the laws of physics. The speed of magical flight is still governed by weight and speed restrictions...

Very few magical effects are immune to the natural laws of physics in some way (Teleport with out error being the first that springs to mind).

[BeerMug Paladin]

I hate to mention this, because I suspect it will become a massive derail, but I have to ask.

For those who critique the idea of a flat world because it would "require" changing all the laws of physics and demand player participation mostly to center around studying physics for the game...

Is the only acceptable setting for 3.5 D&D the Tippyverse? Because that is the logical result of that player behavior as applied to the core magic system. If this isn't the only acceptable setting, why does this aspect of the game have a hands-off exception to it, but a flat world setting does not?

I'm genuinely curious, here.

[Mechalich]

I hate to mention this, because I suspect it will become a massive derail, but I have to ask.

For those who critique the idea of a flat world because it would "require" changing all the laws of physics and demand player participation mostly to center around studying physics for the game...

Is the only acceptable setting for 3.5 D&D the Tippyverse? Because that is the logical result of that player behavior as applied to the core magic system. If this isn't the only acceptable setting, why does this aspect of the game have a hands-off exception to it, but a flat world setting does not?

I'm genuinely curious, here.

Personally, yes, if you play 3.X D&D or Pathfinder with the full implications of the rules in play then yes, your world evolves into the Tippyverse (or some other hyper-magic insanity or possibly the wightocalypse or whatever but ultimately in no way resembles the kind of fantasy world that gets written up in setting books) if no other actions are taken. Ed Greenwood put a sidebar in the FRCS that flat-out admitted to this very early on when he basically said 'please don't have Elminster and co. break the world, even though they totally can.' The 3.X/PF rule set is deeply flawed and the game breaks down completely starting with Teleport and going from there. At even a moderate level of optimization everything from levels 15 onward might as well be tossed int he trash can (and the epic level handbook is a giant waste of space). So yeah, building a world according to strict 3.X mechanics is something you shouldn't do, because it won't work. Worth noting, OOTS has departed by ever greater degrees from said mechanics (and has incredibly low-op builds in play) as the party members have gone up in level in order to make things remain workable.

That being said, it is relatively easy to house rule in some limits that prevent Tippyverse-style shenanigans and many of the other craziness that starts sprouting when high-level spells get throne around. Chain-gating efreet, mass planar binding, demiplane abuse and any number of other issues can be blocked - and let's be honest were never intended to be possible in the first place - by someone paying any real attention. Or you can just cap levels - which PFS did and which playable alternatives like E6 also do.

Also, with the partial exception of Eberron, none of the main D&D settings where designed to accommodate 3.X rules, they were built considerably earlier and no one changed them accordingly because that would both anger the fanbases and because none of the designers really fully realized what they had done when 3e was released (and in some ways until a lot of the options books emerged a lot of the high-op stuff wasn't so viable, Core-only is much more manageable).

[Cluedrew]

Committing to a flat world means that, as a world-builder, you are saying 'I'm going to make a fantasy world that behaves massively different from the Earth from first principles and when I run into any trouble I cannot default back to baseline conditions at all.' That's a Nintendo Hard problem.

Nintendo Hard?

Honestly, people operated completely fine (mostly) for hundreds or thousands of years on completely wrong ideas about how the world operated. I still don't understand how changing the underlying explanations that people often don't know and clearly don't need to get along on a day-to-day basis, causes problems.

That clock is good enough to tell me gravitational acceleration is less at ten-thouand kilometers altitude than it is at ten kilometers altitude.

Cool. How is that setting breaking?

Also, what is your in-character reason for trying this? Is it just a what if?

[2D8HP]

....Is the only acceptable setting for 3.5 D&D the Tippyverse?...

With the very big caveat of my never playing 3.x (0e/1e years ago, and a little B/X and a bit more 5e recently), I think the standard D&D 'verse is a post-apocalyptic "Tippyverse" (all those Dark age scale villages and giant magic item filled ruins).

[Max_Killjoy]

Nintendo Hard?

Honestly, people operated completely fine (mostly) for hundreds or thousands of years on completely wrong ideas about how the world operated. I still don't understand how changing the underlying explanations that people often don't know and clearly don't need to get along on a day-to-day basis, causes problems.

Because if you change the way the world operates, if you change the underlying "explanations", then you change what it's like to live in that world -- the more you change the former, the more you change the latter.

The changes needed to make a flat world work at all, drastically alter the nature of the world.

[D+1]

As DM I tend to think of my game worlds as flat, but it ultimately doesn't matter because unless the PC's spontaneously decide to just march in a straight line until they die, get back to where they started, or fall off the edge they'll never, EVER know and there's no reason they should even be curious. IF I ever did let them get out to where MY map ends then I'd have to make a choice whether the world is a globe, or if there's an edge - or to just continue to dodge the question by expanding the map. If one of them just gets a bee in their bonnet and has to know the answer to this unsolved mystery I would finally actually make a choice based on the likelihood of the answer making a difference at any future point and what kind of adventures I might want to run based on that answer. But likely it STILL wouldn't make a difference because even if they start adventuring on other planes, the adventures on the prime material plane are almost certainly going to remain within a practical circle on the map, regardless of whether it's a map of part of a sphere or part of a flat disc.