Twin Faces of the Sky

[jseah]

I have been toying with the idea for some time about a setting where we have floating islands in the sky. Yes, yes, it's common. But I do what I always do and try to make a reason for floating islands to... well, stay floating. While the people on the island don't... float away.
I have seen many forms of magic or soft-science try to explain this, but the main problems I see with those always start with "what is an island" and other such weirdness.

So I have two main ways of explaining this "floating island syndrome", with different consequences. In any case, here they are, please shoot holes and ask questions to help develop these ideas!

The primary idea I liked is the one I call the title of this thread:
The world has normal gravity that points downwards. Matter in this world doesn't exert gravity, gravity is just fixed.
A small section of this field is sandwiched by two zones. These zones convert matter to its mirror form, which responds to gravity in the opposite direction. I'll call it minus-matter.

Basically, the islands will sit at the interface, being that half of the island is in the zone and has 'negative weight'. So the island's weight is zero and it doesn't fall away. People living on the island are above the zone (being on the top half) and so live with perfectly normal gravity.
Tada, floating island, perfectly normal people.

I note the problem that if too much matter falls off the island, the island becomes net negative weight... It can be solved by making the conversion wear off after some time, but having occasional "imbalanced island" disasters is fun and has some nice implications.
The process is slow in any case. You could toss a castle over the side and the mountain range isn't going to accelerate much because of the loss of a minus-castle worth of mass.

In any case, only big islands are stable for this reason. Tiny ones the size of a house can be destabilized by losing a pebble. Small ones the size of a hill might be stabilized if you drive a car off the edge. A couple of mountains would need something proportionally bigger.
Plus islands exist in flux anyway, since rain happens. (and it's not just water rain, see below) So all the small ones will get weeded out quick, and only the big big ones remain. Like mountain range big. Imagine less floating castle and more floating New Zealand.

The reverse problem isn't one because it solves itself. (more mass makes the island sink, which converts more to negative mass and cancels it out)

Note how this means that oceans don't exist unless it's an inland sea on a big island. Big balls of water sitting halfway in the zone might be net zero, but the negative half would squeeze through the positive half and fall into the sky (the positive half then falls into the zone and converts).
Big amounts of liquid water is kinda rare in this setting. Rivers all fall off the islands eventually and have to be rain or glacier driven and so are rather unreliable. Islands will not be tropical forests unless the water content of the air is really high, and if rain happens that often, erosion *will* destabilize even the biggest mountains eventually.
Perhaps large quantities of normal matter can make a mini deconversion zone to correct tiny instabilities over long periods; but feels like a cop-out

Of course, if you drop a rock over the edge, it'll fall down past the zone and convert to minus-matter. Now, to the rock, gravity just changed direction. It then comes back up and falls into the sky... where after some time, it reaches the *other* zone and converts back... and comes back down to repeat the process.
This is a good time to note that the other sky is identical and has floating islands too. Look up and squint really hard and you might just see it.

Note that the AIR does this, so does water vapour. If the zones are separate enough, clouds will exist in a complex dance around the middle, being a mixture of plus and minus matter.
Air doesn't escape the sandwich either, for obvious reasons. It will still exist inside the zones, the same way that air doesn't all drift off into space or collect near the ground (there's less and less air the deeper into the conversion zone you get, in fact, the distribution is identical to Earth's). So a person falling off would just disappear for a bit then you'll see him go flying up into the sky (this is probably not going to be healthy) or if your island (or him) was moving the right way, he'll land on the minus side of your island with (hopefully) nothing more than a broken leg.


This results in islands being occasionally impacted by escaped small stones, rain from the other side and whatever else that happens to come off an island. People too. Destabilized islands would accelerate slower and so won't hit like they'd been dropped from a plane, but they're massive and an island-island collision from the other sky would be a once-in-forever incident in any case.
Would be spectacular to watch... from a good long distance away in a speedy airship through a telescope. Don't expect much of anything to come of out it in once piece.
Most of them would miss and go sailing into the conversion zone, bouncing between the two until they slowed down enough to stop somewhere.

One could very easily build a craft that could be detached from the island. Mining for minus-matter is easy (just go down and grab some minus-rocks, might want to be careful to not turn into minus-people) and once you have some, you can make part of your ship with it and have instant airships. Whoever lives on these islands could build airships in the STONE age. Although not powered flight obviously.
For obvious reasons, you won't build airships out of normal matter and put it over the side of your island halfway into the zone. Unless you feel like destabilizing your island... =D

The second idea I don't like so much.
Basically, there are two gravity fields pointing towards each other. So down is towards the interface between the two gravity fields. Islands and everything else eventually get stuck in the middle.

Islands are double sided in this case and never destabilize in the way the above ones do. They wobble back and forth a bit and this motion can get quite significant and even destroy it if a big enough mass shift occurs.

Airships "sail" on the interface and everything occurs on the interface. If there's enough water, it'll spread out into a very thin sheet along the interface. Except clouds, those are normal, albeit existing on both sides and rain can come from below (it misses the island and arcs back).
's a weird world this one, part of the reason why I don't like it.

[sktarq]

A few things.
Firstly what kind of game do you want to run with this? dungeon delving? To you want dogfighting skyships? and if so do you want to have to worry about 3D movment? Is it more about explorers? Are you trying to promote highly civilized intrigue based ideas or a more isolationist feel cut off from outside help, limmited contact to crontrol otherwise unstable sittuation to plug adventures into. . .

Things with the first.....is their a limmit to how far this Minus mass flies away from the planet? I ask because if there is a limit (say is dimmiishes with distance faster than gravity) then your old destabilized islands go somewhere plot relevant. Say into orbit beyond the atmosphere or into the high atmosphere beyond where normal life can exist without magic. Where mutations can happen and where through impacts with other high up bodies or exposer to radiation or something they might come back down .... which could have interest plot effects-lost empire ruins to explore without erosion or the like to worry about and lots of aberattions. Invassions from the near stars etc. As per your normally described islands There does also exist the question of what life is life is like UNDER these. Are they stable? Do they move and if so what happens when they collide? and if they do collide wouldn't that just erode them and thus the total mass airbourne sine the smaller fragments produced would destabilize? If they don't move, or move very slowly what happens to plant life under something the size of new zealand or madagascar? What about the disolved soils that would drain from waterfalls comming off the islands? Also what about getting hit on the head by one of these water falls (and not just from the edge but from the base-stalagtite style)

On the second idea. . . why would this be any wierder than the first? Basically you are playing on a sheet of paper-both sides. Question comes up of what is below that level....how reflective is it since I'm going to assume there is not a sun down there- which would lead me to think that you could largly use things from the plane of shadow there. Sort of plane of shadow lite type stuff.

On combining the two. What if you have a special sort of material designation. I'll call it Alfa-X. Maybe its irradiated somehow. But you have Alfa Iron, Alfa Stone, Alfa water etc. Anything alfa has a driving force away from the centre of the planet as well as its gravitional attration-however they are proportional so there is a specific hieght that that it floats-an anolouge to your bi gravitational field level. There is less to worry about in terms of stability issues. Total elevation of an object would occur as the ratio of its Alpha to non alpha material and the Alpha horizion would very like the second option. Heck elevators or at least towers could be made all the way from the non alpha floor all the way to the horizon by slow incorperating more alpha material as it increases in height. And as a total off the top of my head visual image would mountains from the surface break through the horizion of the this kind of place. In the second scenario you described? I'm not sure if that is what you want but I wanted to show an example of how you could try to find what you want without tying yourself down too early.

[jseah]

I should explain things better.

For both ideas, there is NO planet. The only ground is on the floating islands.

For the first idea, the islands float in a uniform gravity field (it's just an infinite 1G gravity); because the bottom half of their mass is negative weight.

Somewhere further up there, where negative weight things go to, is another zone that converts negative weight things back to positive weight things. So things that go up, convert back, and come back down.

That zone has it's own set of islands, just upside down.

In fact, the direction of gravity depends on which side of the sky you're in. Both of them think "away from the island is up" and neither of them are right.


The reason why I don't like the 2nd idea so much is because I find it less cool. >.>

[sktarq]

Well this changes a few things.

Firstly if the the smaller islands are not stable as you put it small islands can switch between the two places on a highly regular basis. Some may even be used expressly for that purpose.

But that does lead to the question of how the islands interact with each other on their different surfaces. Do they float about bumping into each other or are they stabilized in thier map position some how. (It is all right if I give any given point a referece of X,Y and A/B with X,Y,A and X,Y,B being the same point exactly facing each other from these two planes of matter (say a Z value for any distance from the A or B plane?)?) Just to aid the conversation?

Next question-where do you get you light or solar energy in this system?.

Also so while if you drop stuff off the island from the + side and it will convert to - matter and head up the question becomes why not go off (or deep) and become -matter people and then live on the "outer" side of the island? Which would be pretty much what would happen to an island that switched sides anyway. What was the "inner" side (as in facing the other) now becomes the "outer" side. This seems to be a logical extention of what you are saying, but I'm not sure that it is what you want. Or it could be the last of my prescription meds talking.

[jseah]

Firstly if the the smaller islands are not stable as you put it small islands can switch between the two places on a highly regular basis. Some may even be used expressly for that purpose.
Good point! That's a pretty nice idea too.


But that does lead to the question of how the islands interact with each other on their different surfaces.
Well, firstly, even small islands are pretty massive. When you have nothing to push off, remember islands are just floating in air, how exactly are islands going to get moving in any direction other than up or down?

At any great speed that is.

I see most islands as relatively stationary and the giant ones, the stable ones that have the chance to have civilization, will be effectively stationary until well past rocket engines. Probably take a nuclear thermal thruster (or magic equivalent) to move one of those.

Island "maps" would probably be a bunch of points with bearings to each other and wind corridors.


Next question-where do you get you light or solar energy in this system?
That's currently an unresolved question. Have any nice ideas?

Looks like the Creator forgot to say "Light" this particular time.


Also so while if you drop stuff off the island from the + side and it will convert to - matter and head up the question becomes why not go off (or deep) and become -matter people and then live on the "outer" side of the island? Which would be pretty much what would happen to an island that switched sides anyway. What was the "inner" side (as in facing the other) now becomes the "outer" side. This seems to be a logical extention of what you are saying, but I'm not sure that it is what you want. Or it could be the last of my prescription meds talking.
Yeah, it was a possibility I considered. Minus people living on the minus side of the island. In fact, if extensive minus matter mining for airships occurs, you will inevitably get minus people.
Interestingly, people are not the minus things you have to worry about; if you are on the plus matter side and eat plus matter food, over a period of a few months, you'll gradually turn back into a plus matter person. Perhaps not your bones, that might take years, but people are not a long term problem.

You could bias the islands to live on the plus face by having the light source come from the center of the two faces. So its impossible to grow crops on the minus side. YMMV.

[sktarq]

Okay terminology time since the + side and minus side of gravity matter etc is starting to confuse me. Both the explain the terminology and see if understand this whole thing..a cross section of the setting would have a gravitational source "Alpha" then a plane "A" on which there are a bunch of islands a space a plane "B" and then a gravitational source "Beta". Matter that crosses plane "A" becomes attracted to "Beta" and matter that crosses plane "B" becomes attracted to "Alpha". If I got that wrong please explain. Also if you are mining (minus matter wouldn't one have to cross the boundry of the plane that causes people to switch as they are made of matter?

As for the outser sides lacking light etc. I could see it but there becomes a problem if the whole things switches planes because what was the outer facing side would now be faceing inwards. Which could get complex. Or it could be a good source of ruins -abandoned cities to explore etc. Millitary bases, wizard research that must face the outer cosmos or that can't work when exposed the "Solar film" that exists between the "A" and "B" and produces the light to grow crops.


As for movement it would be a chain reaction. Small Island gets unbalenced and shifted latterally slightly so when it crosses space from A to B it hits an island there. This spins the island slightly and de stabilizes it as it knocks a mountain off the edge. The spinning now means when the larger island crosses from B to A it hits something which sends mountain sized fragments flying out laterally from the impact point one of which hits another island and breaks that island in two which start drifting away from each other one of which is unstable..... Give it a few thousand years and whole place will be shaking spinning etc and eroding each other at high rates.

As for light how about a diffuse glow that cycles from "Alpha" to "Beta" over the day?

[jseah]

The thing is that islands are kinda rare. If they weren't, it wouldn't really be Islands in the Sky but more like Hollow Planet.

Rare islands also damp any chain reaction. A destabilized island isn't likely to hit anything more than clouds.

------------------------------------------------------------------

Physics:
Gravity points down.

Plus matter reacts to gravity like we would expect. Minus matter reacts oppositely (it falls upwards against gravity's direction instead of down)

The world exists between two "faces". Crossing out of the world and into one of the "face"s converts you to the opposite type of matter.
The "bottom" face (as seen by gravity direction) will convert plus matter to minus matter. The "top" face will convert minus matter to plus matter.

I can draw a diagram if that will help?

------------------------------------------------------------------

I'm gonna steal the idea for the diffuse light and modify it. More on that when I'm done thinking.

[jseah]

A few things.
Firstly what kind of game do you want to run with this? dungeon delving? To you want dogfighting skyships? and if so do you want to have to worry about 3D movment? Is it more about explorers? Are you trying to promote highly civilized intrigue based ideas or a more isolationist feel cut off from outside help, limmited contact to crontrol otherwise unstable sittuation to plug adventures into. . .
Sorry I missed this. I don't actually build settings with a "kind of game" in mind. I just have an idea and build them.

Presumably I'll eventually start a story with this setting.

Probably involves alot airships and birds. Because fantasy stories in the sky... there is no because, they just have to! =D
A fantasy story in the sky without airships or bird would be Wrong. =P

[sktarq]

The thing is that islands are kinda rare. If they weren't, it wouldn't really be Islands in the Sky but more like Hollow Planet.

Rare islands also damp any chain reaction. A destabilized island isn't likely to hit anything more than clouds.

Physics:
Gravity points down.

Plus matter reacts to gravity like we would expect. Minus matter reacts oppositely (it falls upwards against gravity's direction instead of down)

The world exists between two "faces". Crossing out of the world and into one of the "face"s converts you to the opposite type of matter.
The "bottom" face (as seen by gravity direction) will convert plus matter to minus matter. The "top" face will convert minus matter to plus matter.

I can draw a diagram if that will help?


Rare Islands slows down the chain reaction but by no means stops it. Perhaps the "world" is young?

as for your description of physics...it works great for looking at one island at one moment but when I back off and look at the system trying to describe a point on an island and how it interacts possibly with a point where gravity is reversed is becomeing hard to describe, especially over time and various possition and gravity switches. Down becomes localized in both space and time. if you go below the "down" down switches and becomes up. down and up seem subjective to the person depending on where they are in the system. The thing is I'm 95% sure I get it but talking about it on a descriptive systimatic level is complicated.

[jseah]

Rare Islands slows down the chain reaction but by no means stops it. Perhaps the "world" is young?
While islands moving up and down between the layers will take very long to stop, sideways motion will be slowed by air resistance quite quickly.

Essentially, gravity will drive the islands falling to the other side (this is slower than one thinks because islands will destabilize long before they get any kind of "fast" acceleration).
But nothing drives the islands to go from side to side, at least not consistently.

Eventually, you get islands that drift up and down regularly, but not across.


Wind will push islands around, but only very slowly and will move all the islands in an area roughly equally.


Down becomes localized in both space and time. if you go below the "down" down switches and becomes up. down and up seem subjective to the person depending on where they are in the system.

Actually, this is correct and fully intended. Both sides regard the other side to be "up".

[sktarq]

[/QUOTE]While islands moving up and down between the layers will take very long to stop, sideways motion will be slowed by air resistance quite quickly.

Essentially, gravity will drive the islands falling to the other side (this is slower than one thinks because islands will destabilize long before they get any kind of "fast" acceleration).
But nothing drives the islands to go from side to side, at least not consistently.

Eventually, you get islands that drift up and down regularly, but not across.


Wind will push islands around, but only very slowly and will move all the islands in an area roughly equally.
[/QUOTE]
In which case islands will grind together and erode or break or push an island when it hits it switching sides. I fully accounted for that.

air resistance-good issue since the gravity will pull air to once gravity plane or another. so air in between would be very thin and possibly not breathable. Plus you have this issue of momentum momentum would carry an island slightly past the point of balence as the former "top" now "bottom" of the island passes through the plane or field that converts matter to antimatter and starts to provide a countering acceleration. The slower the transition between planes the less this has an effect but at some speed it would counter air resistance and plunge enough through the convertion plane to totally destabilize at its new position-and cycle back and forth as on the end of a spring. at a slightly higher initial displacement where it compleatly overcomes air resistance (as in it will gain net energy in falling) it would build up enough energy during the fall to give it enough newly vectored GPE that it will pretty much forever bounce back and forth. As long as it hits terminal velocity it will hit it again on the next trip-the friction from air countered by the never ending acceleration. As matter of the island passes through the convertion plane it gain gravitational potential energy but doesn't loose the kenetic energy it already has. -Now I could only see small islands fragments broken off from collisions that start with a good amount of either GPE or KE to begin with and are totaly antimater/matter unbalenced anyway.

[/QUOTE]Actually, this is correct and fully intended. Both sides regard the other side to be "up".[/QUOTE]
Except that depending on which side of an island you are on "up" is different as well as what gravity plane. You have four sides. The antimatter people's functional up and the gravitational up you've described overall don't match up.
And all of that is fine speeking locally but having a way to describe things in the overall system would be good. "UP" is a good local term but does not seem to be a good global term in how you haved described things.

[jseah]

In which case islands will grind together and erode or break or push an island when it hits it switching sides. I fully accounted for that.
Uh, no? Islands don't grind together if there's nothing to grind against. It just floats upwards.
There's nothing to hit on the other side most of the time. Just the other side of the sky (empty air).

The point about islands bouncing back and forth is correct, perhaps an oversight. If your island is big enough and starts with enough energy, it will never stabilize.
But all sideways drift will eventually cease.
Some way of dampening the "bouncing" might be needed, or it might not. You could just get rogue islands that drift up and down with some predictable cycle. It might not necessarily be destructive.
(remember that an island even 51% minus matter and 49% plus matter would be unstable. The net acceleration would be roughly 2% of 1g = 2 cm per second squared, and the terminal velocity could be surprisingly low...)


Also, I never intended the two sides to be too far away from each other that the air would be thin. Recall that Earth has an atmosphere? If the sides are only about 15km or so apart, each side's air will be dominated by the plus/minus air for that side but the whole volume will be filled with air.
And the pressure won't drop much below something that you'll find halfway up Everest.

(Our hypothetical unstable island, even if it was falling through total vacuum, by the time it crossed the other barrier, it would travelling at only ~25 meters per second and making the crossing in an hour. Air resistance, especially when the island is big, would be a major factor)


And all of that is fine speeking locally but having a way to describe things in the overall system would be good. "UP" is a good local term but does not seem to be a good global term in how you haved described things.
I just used it globally because it's easier to fix a frame of reference. It makes things easier to describe if you come from one perspective.

Just remember that the other perspective (upside down) is equally valid.

The main reason why I liked this Twin Faces version rather than the second one was because of this. There IS no global reference for which way is up, nothing differentiates one side from the other (other than their island maps and so on)

[TheWombatOfDoom]

I like the first idea! I've read some of the discussion...and I have a few questions.

Do the occupants of the islands effect the overall mass of one side or the other? As in, would stepping onto an unstable island be enough to stablize it? I assume their constructed dwellings would as well. If an island became over populated, would it cause it to becaome unstable?

If it an unstable island was circling "up and down" in the "above and below" spin that might cause a centrifical force if it spun fast enough, correct?

What happens to a person when they go into the anti matter zone?

What causes wind?

[sktarq]

Uh, no? ...There's nothing to hit on the other side most of the time. ...But all sideways drift will eventually cease.
Some way of dampening the "bouncing" might be needed, or it might not. You could just get rogue islands that drift up and down with some predictable cycle. It might not necessarily be destructive.
(remember that an island even 51% minus matter and 49% plus matter would be unstable. The net acceleration would be roughly 2% of 1g = 2 cm per second squared, and the terminal velocity could be surprisingly low...)
A few things. In the first part two phrases jump out at me "most of the time" and "eventually cease" that's true but over geologic time even rare events add up quickly. Since some islands are new zealand sized (more on that later) a small island that destabilises accross from it would ram into it-and unless this new zealand sized island is quite thick break it up-but even if it doesn't it will bounce and grind into it allot-it probably is only barely unstate and so would bounce along the surface of the larger island-grinding away as it does so. Also asuming your light/heat source is directional and cyclical (as in you have night and day) you will have wind. No if the general wind currents go in one direction in this particular area the an island upwind, if properly shaped, could catch up to an bump into another island on the same gravity plane. once contact is made the upwind isle would act as a shield for the leeward one and thus the upwind isle would push and grind into the leeward one. Eventaully sliding past or breaking up one or both of the islands. Now this process might take a few hundred years but would still happen...I'd again recomend making the world geologically young-as in under 1 million years.
On a related note the gravity convertion planes seem as if they would be covered in a fine layer of peables, grit, sand and dust. All the cast offs of the islands erosion from all sorces, from the rain that pours over the side carrying tiny flecks of minerals the dust from plowing and mining. Lots of these would be highly unstable and fly back and forth before getting lucky and hitting the right balence before being hit by another tiny fragment and producing more dust particles and more bouncing gravel. Actually all this boucing gravel and sand is going to do a serious number on the erosion of exposed regions-sandstorms from above can melt softer stone.
Also on the gravity plane-water seeps from the island. Basically rain from one side would try to fill aquifers in the island-and it would keep going down until the pressure pushing back was enough to stop it. Even if rain only fell on one side and an gravity from one side basically pumped water up the gravity well of the far side of the island (changing gravitational but not absolute direction) eventaully the pressure balence would sit on the gravity plane itself and the water would have only one place to go-sideways. Due to the large surface area the water would evaporate quite quickly but would be an odd effect. It would be a VERY THIN strip of water measured on the axis pertendicular to the gravitational planes


Also, I never intended the two sides to be too far away from each other that the air would be thin. Recall that Earth has an atmosphere? If the sides are only about 15km or so apart, each side's air will be dominated by the plus/minus air for that side but the whole volume will be filled with air.
And the pressure won't drop much below something that you'll find halfway up Everest.

(Our hypothetical unstable island, even if it was falling through total vacuum, by the time it crossed the other barrier, it would travelling at only ~25 meters per second and making the crossing in an hour. Air resistance, especially when the island is big, would be a major factor)
Actaully I think you just solved your issue of how to get people to only live on the inside faces of the islands. For those people on the "outside faces" of the island there would be very little air. The air on that side of the island would be gravitationally pulled to the FAR gravity plane and thus the effective altitude of the people on that side of the island would be the distance between the planes plus the depth of the island beyond the near gravity plane. Effectivly 16-18km high. Do realize though that if a land mass is directly opposing an island a viewer is on they won't have to squint to see it-it will be clear as day and rather detailed. 15 KM (less since the islands themselves both have depth) is nothing for the human eye if we are not trying to look at something else on the same altitude here on earth. Go up a mountain an pick out towns and how they are set out 60km away on a clear day for a fun time-(it's a hobby and easy in S Cal). But this also may lead to issues of your water cycle. Rain flowing off an island has already collected into a stream and that stream would pass the convertion plane switch vertical direction (but not horizontal) an head to the other gravity plane-no most smaller streams etc would turn into tiny droplets and the huge surface area would promote evaporation till it just fizzles out in a cloud but with only a15KM between it would be possible accross from the major rivers of the largest, NewZealand sized, islands to get a river falling from the sky-beautiful destructive etc-which may well turn back around and get halfway back before fissling out. It's an odd visual.



I just used it globally because it's easier to fix a frame of reference. It makes things easier to describe if you come from one perspective...There IS no global reference for which way is up, nothing differentiates one side from the other (other than their island maps and so on)
I understand the concept fine but explaining events that are not tied to one frame of reference or another is getting long winded and precision is difficult as without global reference there is an easy chance of confusion and being misspeaking. There is an absolute direction but up and down do not describe it very well as those are largly defined as the direction thing fall-I understand that you are trying to play with this notion for effect but there is a different type of direction. There is from plane A towards plane B (a direction that exists both inside and outside the space between A and B) and It's reverse B towards A. This ignores any changes in gravity, perception etc to allow for simpler systematic discussion as it is a global direction but not "up" or "down". It's not nessesarily somthing that would come up in play. To be honest I've being thinking about the two planes sideways with gravity acting as a left/right force since you said there was no planet-which helps keep track of things very easily. Sure people wouldn't experience it that way but it sure makes it easier to look at the water cycle and the issues of a lack of a geologic cycle (sedimentary buildup, volcanoes, subduction etc) may bring up.
Also how quickly do the planes convert "matter" to "negitive" matter? Does it happen at the picosecond it crosses? I sorta would think so otherwise by the time countergravitiional effects work in an island would be so far accros the conversion plane that it would overconvert and be tosses right back across (as if it had a large degree of momentum). However you mentioned that unless one spent years on the other side people would not convert (or take years via reach the bones etc) -unless you ment getting food from the far side of the island and eating it on the opposite side of the island it was grown....and remember plants are made up mostly of the local air and so the "place" it is grown matters more than the soil. Otherwise you have people digging all the way through the island and flying off into space away from the setting in toto. (Not good for fun gameplay-frustrations of supermario bros bottomless pits comes to mind)

One other thing-how "thick" are these islands? I ask because I was looking at what would happen if a resonably unbalenced island hit it in the middle. Stone can be pretty inflexible and brittle at times so if it is 200 km in diameter but only 1 km thick and something pushed it in the middle It could crack pretty easily. You make the stone more resiliant in your world on this kind of scale to deal with it or it could set up cities that climb down the cracks formed for easier access to the resources of the far side or ass an esapre route if

[sktarq]

Sorry I missed this. I don't actually build settings with a "kind of game" in mind. I just have an idea and build them.

Presumably I'll eventually start a story with this setting.

Probably involves alot airships and birds. Because fantasy stories in the sky... there is no because, they just have to! =D
A fantasy story in the sky without airships or bird would be Wrong. =P

Well this is kind of important as you use the former (what kind of game you want) to make the world support more of the types of game you want to run.....
Some examples-
Exploration: Promotes the idea of highly mobile islands laterally-lost islands reappear-tiny islands that can be pushed around-things that allow for long distance travel are promoted or allowed
Dungeon delving-History and whatnot to create things to explore-make switching sides cause to abandon things without packing up leaving lots of goodies to find and or lots of good reasons too abandon your +2 longsword somewhere that while you deal with something else.
If you don't want to deal with 3D movment of dogfighting airships then tweak physics to promote co-planar air travel and use different effects for plane to plane travel.
Politics and War: Invoke scarcity-make population matter to stability-be harsher about how disruptive this world's water cycle would be to make agricultre difficult etc to drive inter island conflict.

The point is to have fun the physics should help that - unless this is more a cool thought experiment.

[jseah]

Do the occupants of the islands effect the overall mass of one side or the other? As in, would stepping onto an unstable island be enough to stablize it? I assume their constructed dwellings would as well. If an island became over populated, would it cause it to becaome unstable?
If you came from the outside, you have a very good chance of destabilizing an island if it's a small island. Well, more like "big rock" than "island".

For huge mountain sized islands, they won't move much or at all for a few people.

People growing or building on the island won't do anything to it since all the material comes from the island itself.


If it an unstable island was circling "up and down" in the "above and below" spin that might cause a centrifical force if it spun fast enough, correct?
Yes, if an island was spun like a top, it would be... like a giant spinning disk. The speed you'll have to get up to to actually make much difference (in terms of stability or making people fly off it) should tear the rock apart however.


What happens to a person when they go into the anti matter zone?
They turn into people made of minus matter. Then they walk on ceilings or fall into the sky.

If they eat normal plus matter food for a bit, they'll eventually turn mostly back into plus matter people. They'll be weighing rather little for a good few months at least and their bones will take years to replace.


What causes wind?
Same reason as in RL. Temperature differences drive winds.

Islands are a main cause. Because clouds reflect light and empty air doesn't absorb much, most of the empty sky is quite cold (somewhere around freezing?)
But islands absorb light very well. They will heat up the air around them and this will exchange with the cold air around the island. So there's a continuous "sea breeze" of cold air coming from around the island's edges onto the island and rising from the center towards the "sky".

Big islands would tend to generate their own rain system this way. Far from an island, there might be a few snowy clouds, but there wouldn't be much water. (unless I just randomly fiat more humidity)


A few things. In the first part two phrases jump out at me "most of the time" and "eventually cease" that's true but over geologic time even rare events add up quickly.
<...>
One other thing-how "thick" are these islands?
Now, I think we are misunderstanding each other. Let me tell you what I "see" in the setting. I have a sketch of a plot worked out already, should do pretty well for an extended campaign, although I will probably turn it into a story.
See below. But essentially, the major habitable islands are freaking huge (400km diameter or so and perhaps four or five km thick in the middle?) and are so far apart that collisions between them are essentially non-existent. Minor collisions of barely stable rocks or hill-sized islands would go like you mentioned.

The setting is rather large, to accomodate the fast travel that early airships would allow. The average distance between habitable islands is roughly the size of the Indian Ocean. Even by air, travel time between islands can take weeks.
Of course, searching an area that big for an island won't take nearly as long as we did. Being that most of it is empty sky, you can see maybe even 100 km before the air and snow blur everything.


On a related note the gravity convertion planes seem as if they would be covered in a fine layer of peables, grit, sand and dust.
Nah, those would get destabilized by wind. They'll never stabilize and will eventually hit an island. It's probably how the islands get big.
Once an island gets big enough to take these hits and not destabilize, it will just accrete more and more dirt. After all, the random impacts from dirt is essentially a random bombardment from all sides, therefore half is minus matter and would roughly balance out.


the issues of a lack of a geologic cycle (sedimentary buildup, volcanoes, subduction etc) may bring up.
I've been thinking about this.
No magma, which means no igneous rock. Eventually every bit of rock is sedimentary in nature. No tectonics means no volcanos or earthquakes, which I can live without since those would be incredibly destructive for an island.
Iron gets a bit easier to find since, there's nowhere for it to sink to (most of Earth's iron sunk to the core).


I understand the concept fine but explaining events that are not tied to one frame of reference or another is getting long winded and precision is difficult as without global reference there is an easy chance of confusion and being misspeaking.
You can just use the frame of your "home" island? That would be a pretty natural evolution for the islanders, which is really all that matters.

Plus matter is what your island's top side is made of. Down is what down is to your home island, etc. etc.


Also how quickly do the planes convert "matter" to "negitive" matter? Does it happen at the picosecond it crosses?
Yeah, that's how it works. You convert the moment you cross.

The mentioning of bones and years was about people converting BACK to plus matter.
If you eat and drink plus matter while you are made of minus matter, eventually your body will slowly convert to plus matter. I think the full turnover time for humans is... what, 20 years? Mostly the bones that take forever.


Well this is kind of important as you use the former (what kind of game you want) to make the world support more of the types of game you want to run.....
So, I have a sketch of a plot, like I said:
The capital island of the *insert country name here* is a large island roughly the size of Borneo. It contains three mountains near the center and the tallest is over two kilometers high. The other side of the island is a rough scraggly mess of hard rock, the weaker rock has since been eroded by the freezing wind and hail (rain that misses the island eventually comes back up, usually as hail). The island is roughly four kilometers thick, although it obviously gets rather thin along the edges. The mountain height is calculated as height above the "ground level". So the top of the tallest mountain has nearly reached the negative atmosphere.
The big mountain has a very interesting "negative waterfall". Frozen water that hits the other side builds up as snow and ice, collects in underground rivers and finds it way along an extensive cave system up into the mountain. It eventually finds an exit near the top (although not quite at the peak) and falls into the sky. The island can be easily spotted by air due to the many kilometers high spray of minus-water that shines in daylight.

Being the biggest island in the whole setting, it can support the largest and most advanced population. This makes it very powerful militarily and it is a bit of a bully in the international landscape. It's power is mostly curbed due to the large distances between islands and that wind corridors are not very reliable (sailing airships go astray more than one time in twenty and take forever to get anywhere).
Of course, like any other island in the setting, water is quite the precious commodity. Despite its size, the nation doesn't support a population anywhere near as dense or high as in RL. The Romans would probably have more population than they do, so most of their island is not inhabited and the cave systems in particular are nearly impossible to transverse or chart. Plenty of opportunities to hide as an outlaw or smuggle.

Airships have only gained powered flight somewhere in the last 20 years due to advances in magic, although due to some long-winded history I'm patching in from another older setting, magic is sort of frowned on.

Basically, the plot involves a major artifact from a past civilization that is the largest fragment of magic technology left over from then; an artifact that is the most powerful type of all, a magical library compressed into a large diamond (diamonds are kinda rare in this setting due to no volcanic activity).
*insert mysterious mage here* has it and is on the run from all and sundry and joins up with a band of airship pirates (more like privateers) from a different country. Cue intrigue, airship battles, a chase all around the setting, blah blah.

[sktarq]

Same reason as in RL. Temperature differences drive winds.

Islands are a main cause. Because clouds reflect light and empty air doesn't absorb much, most of the empty sky is quite cold (somewhere around freezing?)
But islands absorb light very well. They will heat up the air around them and this will exchange with the cold air around the island. So there's a continuous "sea breeze" of cold air coming from around the island's edges onto the island and rising from the center towards the "sky".

Big islands would tend to generate their own rain system this way. Far from an island, there might be a few snowy clouds, but there wouldn't be much water. (unless I just randomly fiat more humidity)
A few issues. Firstly since you lack water between islands corrolis forces etc and since you are saying that islands themselves are rather rare than lateral wind movment is going to be rather rare. Each island would make its own wind effects and a sort of wind/turbulence bubble but it would fade over distance. There would be quite allot of vertical air motion both from islands heating effects and converting air changing direction and pushing towards its new "down"



Now, I think we are misunderstanding each other. Let me tell you what I "see" in the setting. I have a sketch of a plot worked out already, should do pretty well for an extended campaign, although I will probably turn it into a story.
See below. But essentially, the major habitable islands are freaking huge (400km diameter or so and perhaps four or five km thick in the middle?) and are so far apart that collisions between them are essentially non-existent. Minor collisions of barely stable rocks or hill-sized islands would go like you mentioned.

The setting is rather large, to accomodate the fast travel that early airships would allow. The average distance between habitable islands is roughly the size of the Indian Ocean. Even by air, travel time between islands can take weeks.
Of course, searching an area that big for an island won't take nearly as long as we did. Being that most of it is empty sky, you can see maybe even 100 km before the air and snow blur everything.
Okay two things. May point still holds about the collisions etc. Island density has nothing to do with the fact that the world you describe is unstable and will eventually be a bunch of hot dust. It simply changes the rate at which it gets there. As for being unstable that's not a knock on the system-earth is unstable, it will eventaully tidally lock with the sun, loose it's magnetic field and atmosphere and be enveloped by the expanding red giant our sun is destined to become.....but there are lots of good stories to be had in the meantime.

Also in terms of "the nearest habitable island" how big is a "habitable" island? Long Island? Manhatten? Easter island? Tasmania? Jamacia? Isle of Man? Or do you mean it is that far until an island of comparable size (if smaller) such as say Tasmania, Cuba, Ceylon, Formosa, Ireland or Java. Because living on places the size the Isle of Wight, or even Manhattan would be possible for villages etc. And I would think that small islands would vastly outnumber large islands say 6 of the Sciliy, Hinian, Hispaniola class for every Ireland or Tierra del Fuego, Which would lead to 36 of the Jamacia, Tonga, Puerto Rico, Sky, size Islands which gives you a couple hundred the size of Bali, Long Island etc. Which gives you say 1000 of the Manhattan, Staten Island, Isle of Man, Singapore, Aruba, type. So about 1250 Islands that would be "habitable" (I'm being generous since even a 160 acre island in the pacific has a permanent long term population. over an area roughly the size of the surface of planet earth-twice if you count both gravity planes. and several thousand smaller ones. Even counting the gravity planes as "one" surface of the earth equivilant that is still around 1% of the area.
Also being htat spread out-effects on flora and fauna.....how do animals and plants spread-including people? Since powered flight is rather new how did these places become colonized? Did the gods hit the "populate" button? more powerful race of long ago?

Also thought experiment. A pytoplankton from a pond gets spashed with a drop of water off his island hits the conversion plane and starts to fall to the other side. Halfway there that drop hits a drop of "minus water" and they mix. Being small the surface tension of the water is strong enough to hold the drop together long enough for the plankton to absorb a fair amount of minus water into itself which slows its fall and the process repeats until the plankton is neutral. . . lets say it survives the loss of the rest of the droplet by forming a cell wall-basically algae. Now its not a huge jump to say that a bacteria could evolve a way of dumping positive or negitive matter water selectivly and would eventually keeps its ballence. It divides and some insect evolves somewhere to eat these things and only these. Since it is eating a gravitationally balenced diet it will eventaully gain a balenced trait itself and float away. You see where I'm going with this? Dust particles would that are falling back and forth provide minerals for these life forms. They would eventaully form the basis onf an ecosystem. . . Some strange combo of aquatic and Gas giant fantasy type ecosystem. . . anyway it's an Idea and a food source for birds and things island hopping.


Nah, those would get destabilized by wind. They'll never stabilize and will eventually hit an island. It's probably how the islands get big.
Once an island gets big enough to take these hits and not
Accrete...really? Ok dust, pebbles, sand etc would no accrete in the island like system you describe if it worked like dust, sand, etc does on earth. If you want to make these things more "sticky" in you fantasy world in order for your description to happen that's fine but it is something you should be ready to explain to players that see the flying sand kicked up in mining the far side of the world and think "sand-blaster effects should have wiped out this city long ago" Islands will naturally want to shrink over time due to erosion as there is no force pushing the sand/dust particles together. Pressure from stuff on top? nope they will slide out allong the conversion plane before turning into stone (at least at the edges-which would expose new edges-repeat).


I've been thinking about this.
No magma, which means no igneous rock. Eventually every bit of rock is sedimentary in nature. No tectonics means no volcanos or earthquakes, which I can live without since those would be incredibly destructive for an island.
Iron gets a bit easier to find since, there's nowhere for it to sink to (most of Earth's iron sunk to the core).
Then again so did most of the world's Uranium and Thorium-but I don't recomend keeping that stuff around as it would render many islands totally unlivable. :smallwink:



You can just use the frame of your "home" island? ...Down is what down is to your home island, etc. etc.
It would be a natural evolution for the locals but once you leave the island it would be useless. It is even more difficult when dicussing fluids that have no "home" island. It is about finding objects that do interesting things figuring out their POV on up/down contrasting it to your players POV on up/down to produce the most interesting game play and to track things like weather, dust, mobile islands etc. Much cleaner not to have a "home island" and in fact seems limmiting. Plus since down is not down to my home island but to only half of my home island so for those on the "outer" side making even a single island not a good baseline. Hence my systematic urge.


on plot-good stuff....you do know that diamonds couldn't be formed on this world though. Volcanoes don't make diamonds they just carry them from deap within the earth where they are made in the upper mantle. - Magic perhaps?

EDIT: Thought: What about your dieties in this setting? You could have a "maker" type god. Some kind of god who collects the dust and makes new islands? Earth mother sort? Father figure on the order of a Ra instead? . . . Some sort of dancing rain god? He is happy you get water he is angry get sand and dust falling on your crops in sandsotrm. . . . Also what about a pair of gods each represeneted by the gravity planes? Two sisters who are always trying to steal islands from each other? Would lead to the temples on the outer sides being dark agressive places ripe for adventure.
Also What system are you useing - 3.5? I don't know if you have clerics come to think of it.

[jseah]

Hmm, I have spotted a flaw.

If you drop a pebble down, it will just go straight into the zone and fall back up. And then it hits the other side and goes into that zone and comes back down, ad infinitum.

This is because if you start with 100% plus matter, it won't be able to stop in time to stabilize. Even the really huge objects, like mountains, if they are destabilized too much, can't be stopped and will convert more than half the difference (which destabilizes them further)...


There needs to be a damping mechanic or it won't work.

Perhaps conversion could kill momentum... Hrm...

[Q. Flestrin]

Hi, I'm a bit of a noob here, but ...
I have an alternate solution that gets around the whole gravity fields thing. I've been working on a world like this, although not for D&D, and here's the basic makeup of the world. At the center, there's this small core Which is one of the few sources of magic in the world and a major plot point. that is very dense, which keeps the shards (my term for the islands) orbiting and allowing the world to act like a typical planet. (I realize that jseah's world has no core, but the core could probably be remade into a spherical gravity field.) Then you have to go through about three miles of sky to get to the lowest shard, and there's about a two-mile variation in shard height. The shards, however, contain a mineral that I call "levitas" that is repelled by the core. All shards have at the very least an amount of levitas proportional to their mass, which allows them to be attracted to and repelled by the core in equal measure, like they're resting on some sort of invisible floor (which also allows for normal precipitation). Additional levitas will cause the shard to float higher. The mining of levitas is frowned upon because it causes the shard to sink. The airships here float using tanks of hydrogen-producing microorganisms, but that's less relevant.
So that's my solution. You can use it, tweak it, or whatever, so long as you don't call the mineral levitas.

[jseah]

Well, for one thing, levitas repulsion needs to be inversely proportional to the distance to the core. Relying on equal repulsion makes you run into the same problem as I had about island stability.

[Q. Flestrin]

Ohhh... can't believe I didn't think of that, especially with people living on the shards. Thanks for pointing that out. I guess then that levitas allows the shards to ignore gravity, and that a larger amount of levitas is proportional to a larger potential to ignore gravity. If that makes any sense.

[jseah]

Uh, no, that's the same as the problematic one. The moment anyone steps onto an island, the mass per levitas increases and the island will start to sink and never stop.

What you need is a way that levitas close to the core is repelled MORE than the same amount of levitas further away. So that sinking islands would gradually experience more repulsion and so eventually stop sinking.
(And rising islands from levitas excess would experience less and less repulsion as they rose and eventually stop rising)


There is also a matter of rotation to consider. >.>
If the levitas is biased to one side of an island or the island was imbalanced in some fashion, the island would rotate until it was balanced (average center of levitas is directly above the island's average mass)
While that itself is not a problem for the island, one would think it could get a mite uncomfortable for the inhabitants.

[Q. Flestrin]

Okay, I can easily handwave levitas repelling more when closer to the core than when farther away.
I think that a fix for the rotation issue would be that levitas does not naturally accrete, and this would explain why levitas hasn't been mined.