The Conundrum of Conjoiners: an Analysis of Navani's Airship

[+Oltux72]

53 minutes ago, Quantus said:

Im not sure what you mean here?

Suppose you are exerting a force on a part of a conjoiner isolated in a plain that pushes it out of that plane. The other half does not move, presumably, as it feels no force.

If you move only in the plane, they will act like normal conjoined fabrials.

Now assume a force vector that goes out of the plain at a 45 degree angle. Is the force vector redirected into the plain, that is does the magnitude of the force stay, or is the force diminished to the component with the plane?

53 minutes ago, Quantus said:

I propose that this is not a concern on Roshar, because as far as the collective consciousness of Roshar is concerned, the planet is a flat plane.  We know this by the topography of  teh Cognitive Realm, which surges generally do business with and which is literally the reflection of the collective idea of Reality.  All that to say that spanreeds are likely to operate using Cognitive Realm topography, where everything is projected onto a flat plane with (more) objective cardinal directions.  

Well, why then do we never hear about somebody aligning a spanreed north to south?

[Karger]

4 minutes ago, Oltux72 said:

Well, why then do we never hear about somebody aligning a spanreed north to south?

Why would we?  People must leave their spanreeds aligned.

[Quantus]

3 minutes ago, Oltux72 said:

Suppose you are exerting a force on a part of a conjoiner isolated in a plain that pushes it out of that plane. The other half does not move, presumably, as it feels no force.

If you move only in the plane, they will act like normal conjoined fabrials.

Now assume a force vector that goes out of the plain at a 45 degree angle. Is the force vector redirected into the plain, that is does the magnitude of the force stay, or is the force diminished to the component with the plane?

in the case of the method she mentions to isolate the link to a single plane, I think it would follow normal component force rules (below), so the vertical component would be transmitted through the fabrial link while the lateral force would not, and some force would be lost.  Navani implied that it was a separate breakthrough to Change the vector, and Im hoping to get a look a the actual aluminum shielding to figure out how the two apparently distinct effects are pulled off.  

https://www.physicsclassroom.com/class/vectors/Lesson-3/Resolution-of-Forces 

3 minutes ago, Oltux72 said:

Well, why then do we never hear about somebody aligning a spanreed north to south?

I thought we had, but I will have see if I can find an example before I could swear to it. 

[+Hoiditthroughthegrapevine]

5 hours ago, Jofwu said:

I don't quite follow on the shielding of the chulls. It seems like you're arguing that it enables them to keep the gems on and working as they make the turn, but doesn't the chapter specifically note that they don't do this? That they turn them off when they turn?

You're right, they do say they turn them off, but the effect would be the same. Building an Aluminum shed for the turn around would make it so they wouldn't need to switch off the x-axis conjoiners during the turn.

5 hours ago, Jofwu said:

I think this is the biggest thing that irks me. If spanreed board orientation (rotation around the Y axis) doesn't matter, then this second breakthrough seems irrelevant to me. I'm more in favor of saying it IS a breakthrough, and that spanreed board orientation did matter. But I guess we'll have to wait and see?

 

3 hours ago, Oltux72 said:

The problem is that we have no evidence for the tY-axis level. In fact we have evidence for the spanreed placed by hand

Your'e right, looking at my diagram why would an air bubble sit in the middle of a vertical column of water? Only the x and the z axes are set by leveling, and like Jowfu said, the alignment of the x and z axes between the relative framework of both sets of spanreeds would involve a rotation about the y axis of one relative coordinate system.

My supposition is that this coordinate translation is necessarily accomplished by the magic of the fabrials. The conventions of how the boards are setup aren’t mentioned much in text, but it is stated that the spanreeds are placed in a holder. With the spanreed oriented so it is perpendicular to the leveled x and z planes it is necessarily oriented along the y axis. I think we have to assume that the conjoining rubies are placed in a standardized position, and the distance from the ruby to the tip has also been standardized, and since this is a common relative displacement for the sake of simplicity we could say that the tip of the spanreed where it touches the x-z plane can said to be the origin for its relative 3 dimensional coordinate system. 

But the utility of a conjoiner that transfers one dimensional force vectors along a specific plane is obvious I think, because the only thing that is linked between the two systems would be motion along one relative axis. The only thing each conjoiner cares about is the force being applied along its relative axis. The chull carried lattice has a realtive orientation where the conjoiners have a specific orientation for forward motion along the x axis. The coinjoiners embedded in the hull of the Fourth Bridge likewise have a relative orientation for what forward motion is. There is no need to align these vectors, forward motion in one system is transferred to the other system as forward motion, regardless of the orientation of either one.

I can envision a series of weights and conjoined fabrials that are activated by control systems that are likewise conjoined to the on deck control systems of the Fourth Bridge giving precise control over ascent/descent, and forward and retrograde motion. Pitch and yaw really aren't necessary to fly floating magical barges.

I think this is fun to speculate about, but these are the early days of Rosharan fabrial science for sure. My bet is that the future lies in heatrial powered steam engines, and if the ethics line up, using the surge of gravitation. All this at a distance stuff can and probably will go horribly wrong.

[+Oltux72]

8 hours ago, Karger said:

Why would we?  People must leave their spanreeds aligned.

They keep them with themselves while travelling and servants run around with them and they use arrangement with multiple reeds and one board.

If the coordinates are absolute they will need to realign their boards every evening when they make camp. And they would have to realign the spanreed itself with respect to north and south when they plave it on the board.
Worse, searching all three volumes I found no mention of a compass. In fact we have no idea whether magnets are known on Roshar.

8 hours ago, Quantus said:

in the case of the method she mentions to isolate the link to a single plane, I think it would follow normal component force rules (below), so the vertical component would be transmitted through the fabrial link while the lateral force would not, and some force would be lost.

That makes intuitive sense, but it means that the direction of the force is changed. But it is not the only interpretation. It is possible that the elements are no longer equal and that the one shrouded in aluminium indeed is isolated in a plane, but you must not move it in another direction or it will get stuck or something bad happens.

6 hours ago, hoiditthroughthegrapevine said:

Your'e right, looking at my diagram why would an air bubble sit in the middle of a vertical column of water?

Attach it to the reed and rotate it 90 degress. In fact add two or add a small board to press the reed against.

6 hours ago, hoiditthroughthegrapevine said:

Only the x and the z axes are set by leveling, and like Jowfu said, the alignment of the x and z axes between the relative framework of both sets of spanreeds would involve a rotation about the y axis of one relative coordinate system.

Well, no. Or rather if we are happy to look at translational movement only, that will be correct. Unfortunately we are not. You write with these things. They definitely transmit also rotational movement. That means you also need to align the orientation of the gem. A careful search of the text reveals that the gem is on the side of the reed. So you need to have your gem also point in the right direction.

6 hours ago, hoiditthroughthegrapevine said:

My supposition is that this coordinate translation is necessarily accomplished by the magic of the fabrials. The conventions of how the boards are setup aren’t mentioned much in text, but it is stated that the spanreeds are placed in a holder.

Well, no. Or rather for the purpose of watching them for flashes. When actually writing they are not held at all. Otherwise the scene with Shallan's reed hovering in free air becomes impossible to explain.

6 hours ago, hoiditthroughthegrapevine said:

With the spanreed oriented so it is perpendicular to the leveled x and z planes it is necessarily oriented along the y axis. I think we have to assume that the conjoining rubies are placed in a standardized position, and the distance from the ruby to the tip has also been standardized, and since this is a common relative displacement for the sake of simplicity we could say that the tip of the spanreed where it touches the x-z plane can said to be the origin for its relative 3 dimensional coordinate system.

But then why are they so pedantic about the board being level to the point of using levels? It would be enough for the reed to be orthogonal to the board, not upright in an absolute sense. It looks to me like spanreeds interact with gravity.

I thunk we need to look at a more complicated system. If I account for everything, I will land at a system I don't like myself

1. Basically, all else being equal coordinates are relative, not absolute
2. Except, gravity matters. You must align with respect to gravity
3. Spanreeds are not fully symmetric. They are symmetric with respect to translational movement. But the send/receive settings do something. Spanreeds are not symmetric with respect to rotational movements.

 

[+Bzhydack]

4 hours ago, Oltux72 said:

Worse, searching all three volumes I found no mention of a compass. In fact we have no idea whether magnets are known on Roshar.

They have Highstorm and practicly all is formed by it, from east to west. Orientation is smallest problem on Roshar.

All yours theories @hoiditthroughthegrapevine , @Oltux72, @Quantus are fascinating, but is one problem with them:

Why they need reversers?

If refference point of gem mouvment is gem itself, so to make reverse mouvment all what is needet is just turn one gem needet amount of degrees and we can have mouvment not only in oposite directions but in ANY direction. And we know that is not what happens. They need reversers and conjoiners. So answer is only one - refference point of gem orientation is Core of the planet.

This will explain why they need set chulls on Plains - they need really large space because to move ship in any direction they need to move chulls in the same direction.

And of course Spanreeds need to be oriented first, so why we dont read about this?

Because this is so obvious for Rosharans that they dont even think about it. Remember, they have very standarized everything in comparison to our world - one currency, two writing systems, just few languages.

So I think right after spanreeds spread, scholars and ardent standarized orientation. Maybe seting point of reed in upper left corner has also this function?

[+Oltux72]

2 hours ago, Bzhydack said:

They have Highstorm and practicly all is formed by it, from east to west. Orientation is smallest problem on Roshar.

Unfortunately no. Azure tried to operate a spanreed in a cave. If you need anything more than levels and a compass that would be impossible.

2 hours ago, Bzhydack said:

Why they need reversers?

If refference point of gem mouvment is gem itself, so to make reverse mouvment all what is needet is just turn one gem needet amount of degrees and we can have mouvment not only in oposite directions but in ANY direction. And we know that is not what happens. They need reversers and conjoiners. So answer is only one - refference point of gem orientation is Core of the planet.

Yes, but for all axes? It looks very much like down has to be down. But left and forward?

2 hours ago, Bzhydack said:

This will explain why they need set chulls on Plains - they need really large space because to move ship in any direction they need to move chulls in the same direction.

Well, if you need aluminium for turning there is no reason you could turn only 180 degrees. If you can rotate the gems, no need for full mobility either.

2 hours ago, Bzhydack said:

And of course Spanreeds need to be oriented first, so why we dont read about this?

Because this is so obvious for Rosharans that they dont even think about it. Remember, they have very standarized everything in comparison to our world - one currency, two writing systems, just few languages.

So I think right after spanreeds spread, scholars and ardent standarized orientation. Maybe seting point of reed in upper left corner has also this function?

We do read about checking the levels multiple times.

[Jofwu]

13 hours ago, hoiditthroughthegrapevine said:

it is necessarily oriented along the y axis.

I don't actually think that's necessary. It would be if everything is relative to the gemstone itself, but if you go that road it gets immediately into the idea that reversers are totally irrelevant. No need for a reverser when you can just flip one of your conjoiners upside down.

No, I think the rotation of the gem itself doesn't matter, until you turn them "on" and they are actively conjoined. At that point rotation and translation between both pens becomes locked. So... it doesn't really matter if our reed is a degree or two off from perfectly vertical. It's still going to move left/right/up/down across the page with it's twin. Just means the strokes might be slightly different since the reed makes contact with the paper at a slightly different angle? No big deal.

2 hours ago, Bzhydack said:

Why they need reversers?

Exactly. Bzhydack gets me.

@ Bzhydack, I believe the argument is that the science of a spanreed somehow doesn't apply to all applications. Like... maybe it only works with gems below a certain size or something, or... for gems that aren't stressed too much? There are certainly reasons we could make up to explain why this spanreed trick doesn't work in every application, making reversers valuable and (in the case of the Fourth Bridge) making aluminum important.

All of that said, I agree.

I think it's way more convoluted to say "hey, by the way, spanreeds work like this, but bigger devices can't use that technology for various reasons" than it is to say "they point their spanreed boards east and we just haven't talked about it."

Yes, there's the argument that reversers can reverse in all three axes at once. I think this is a very weak argument. It means they matter, true, but only for very niche purposes. This concept has been pointless in every application of reversers that we've seen so far.

7 hours ago, Oltux72 said:

They keep them with themselves while travelling and servants run around with them and they use arrangement with multiple reeds and one board.

If the coordinates are absolute they will need to realign their boards every evening when they make camp. And they would have to realign the spanreed itself with respect to north and south when they plave it on the board.
Worse, searching all three volumes I found no mention of a compass. In fact we have no idea whether magnets are known on Roshar.

They absolutely have some means to tell direction. It's kind of hard to navigate and make high quality maps as they have without some means to do that. Being in a cave or inside rooms doesn't really matter... If you no the orientation outside it's not THAT hard to figure it out inside. And hey, if you ever get totally turned around you can do conjoin the two, put your pens in the middle of the page, and make a stroke in an agreed upon direction and you can easily get realigned. Not a big problem at all.

And there's really only been a handful of cases where the alignment of the board would ever need to be mentioned, if I'm not mistaken. Seems like most of the spanreed boards we see are fixed in place as permanent furnature. And when they're not, they're usually placed by someone else so there's no need for the PoV character to take particular note of how they orient it. (especially Dalinar)

Off the top of my head, I can only think of a few Shallan scenes where I might expect a detail like that to come up. And it's just not hard for me to imagine it isn't worth mentioning. Heck, we've only heard them mention the leveling requirements two or three times? And at least one of those was a case of a desk that was fixed in place. It's not the sort of detail that needs to be mentioned.

[Quantus]

7 hours ago, Oltux72 said:

They keep them with themselves while travelling and servants run around with them and they use arrangement with multiple reeds and one board.

If the coordinates are absolute they will need to realign their boards every evening when they make camp. And they would have to realign the spanreed itself with respect to north and south when they plave it on the board.
Worse, searching all three volumes I found no mention of a compass. In fact we have no idea whether magnets are known on Roshar.

Compasses arent particularly necessary for more navigation, historically.  They are arguably better than most other methods because they can be used day or night and in any weather condition, but they were not widely used for land navigation until the middle ages.  Celestial navigation, sunstones, etc, were entirely effective before that.  And on Roshar in particular, the Highstorm and crem deposits make direction immediately visible by literally any part of the landscape, with the way it always hits one side of a given structure and crem builds up more on the stormward side.  So in most places on Roshar you literally just need to glance around to instantly know Stormward and Leeward (East & West).  

[+Oltux72]

1 hour ago, Jofwu said:

I don't actually think that's necessary. It would be if everything is relative to the gemstone itself, but if you go that road it gets immediately into the idea that reversers are totally irrelevant. No need for a reverser when you can just flip one of your conjoiners upside down.

No. A reverser will keep the joining even while the halves are in motion towards each other. We are sure of that or Navani's platform would have failed as soon as it moved. Secondly, we have no idea how reversers deal with rotational movement.

 

1 hour ago, Jofwu said:

And there's really only been a handful of cases where the alignment of the board would ever need to be mentioned, if I'm not mistaken. Seems like most of the spanreed boards we see are fixed in place as permanent furnature. And when they're not, they're usually placed by someone else so there's no need for the PoV character to take particular note of how they orient it. (especially Dalinar)

Dalinar describe in meticulous detail how his scribe checks the levels and puts the reed into its place. No alignment north/south
 

 

[Jofwu]

3 hours ago, Oltux72 said:

No. A reverser will keep the joining even while the halves are in motion towards each other. We are sure of that or Navani's platform would have failed as soon as it moved.

Sorry, I'm not sure what you're saying there.

We don't know how rotational movement works, sure. I think it's reasonable to assume it works the same, considering everything we know suggests they are the same as conjoiners but in reverse. If they DO for some bizarre reason handle rotation differently it still isn't much of an argument, because we've never seen them employed to take advantage of that.

3 hours ago, Oltux72 said:

Dalinar describe in meticulous detail how his scribe checks the levels and puts the reed into its place. No alignment north/south

Right. Because that example was a piece of furniture that doesn't get moved. Its orientation doesn't change. No need to adjust it.

[+Oltux72]

1 hour ago, Jofwu said:

Sorry, I'm not sure what you're saying there.

Conjoiners must be at rest with respect to each other to join. Assuming absolute directions they will also stay at rest with respect to each other. (With the exception of down not being paralell)

Reversers however move in opposite directions. Hence they must develop a speed difference as soon as they are moved. There we have a fundamental difference.

1 hour ago, Jofwu said:

Right. Because that example was a piece of furniture that doesn't get moved. Its orientation doesn't change. No need to adjust it.

Then why recheck that the board is still absolutely horizontal? It is entirely plausible that they trust their furniture to be stationary. But then why recheck only something? Especially if you want to impress the boss with your dilligence.

[Jofwu]

58 minutes ago, Oltux72 said:

Conjoiners must be at rest with respect to each other to join. Assuming absolute directions they will also stay at rest with respect to each other. (With the exception of down not being paralell)

We're apparently just not on the same page. The way some people are talking about spanreeds in here, the reed itself is somehow oriented relative to the board. (making the orientation of the board irrelevant)

That implies if two people sit facing one another with their spanreeds on, and the writer moves their reed up the page, the twin will also move up the page. Meaning they are both moving toward one another.

58 minutes ago, Oltux72 said:

Then why recheck that the board is still absolutely horizontal? It is entirely plausible that they trust their furniture to be stationary. But then why recheck only something? Especially if you want to impress the boss with your dilligence.

Furniture doesn't randomly become unlevel under normal use. Your kitchen table doesn't become less level and need adjusting from one day to the next. The only explanation I see is that the desk is adjustable and sometimes gets used for a different purpose where they don't want it level. I don't have to check the levelness of my kitchen desk right now to know it is exactly as level as it was yesterday. (or last year, for that matter)

Hm...

Okay, maybe a better explanation is that the spanreed board is mobile and they're sitting it up on some other desk. That would give more reason for them needing to level it, because it could have been used previously on a different surface or could have had the adjustments messed up while being transported.

But the orientation still wouldn't be very notable. The desk could easily face a known direction. And it doesn't need to be super precisely. The levelness matters, because if you're not level then the end of the pin might bear down too hard and let out too much ink to be legible OR it might not make contact. If you're board is askew by half a degree it just means the writing will be slanted on the page.

So... sure... if it works this way then the orientation could have been worth a mention (even if I disagree it was necessary). But it seems to me that it would have been already set prior to Dalinar entering the room. And I think it's a week argument if you think the orientation should have been mentioned but some full explanation of the fact that the board is mobile is not. I mean, come on... We're not getting every little detail when these things are used.

[+Bzhydack]

4 hours ago, Oltux72 said:

Then why recheck that the board is still absolutely horizontal? It is entirely plausible that they trust their furniture to be stationary. But then why recheck only something? Especially if you want to impress the boss with your dilligence.

You forget about one thing.

Highstorm.

This thing can throw giant rocks dozens or even hundreds feet into air, so can also generate small seismic shakes. Also wood is not as static as many think. Even walking people can generate shakes and disrupt horizontal setting - we can see this in our world on sensitive laboratory scales.

Also, seting reed on paper IS seting direction. Sender can correct paper position before start scribing, You have two refference points: position of inkwell and point in upper left corner of paper. Setting direction is here - first step after seing signal is seting Reed On, then checking levels, then dip reed into inkwell (first refference point, we can asuume reed on the other side is in inkwell) then set reed on point in upper left corner of paper (second refference point, sender reed will move the same way and should be in the same point, if is not, sender can correct his paper setings), then change seting on reed on "Recive".

[Quantus]

Stumbled across a relevant WOB, not sure if this has been mentioned yet.  Turns out spansreeds have always auto-corrected for planetary curvature and the positioning of the writing board.

 

Quote

 

gossypiboma

When communicating over spanreed, do you have to compensate for the curvature of the planet? For example, would communicating with someone on the other side of the planet result in upside down writing?

Brandon Sanderson

Spanreeds auto-compensate when you activate them. Meaning, once you tap them on, they will follow the same pattern in relation to the writing board as the other one.

/r/books AMA 2015 (June 12, 2015)

 

 

[+Oltux72]

11 hours ago, Quantus said:

Stumbled across a relevant WOB, not sure if this has been mentioned yet.  Turns out spansreeds have always auto-corrected for planetary curvature and the positioning of the writing board.

That means that directions are relative. The basic information is there. It means that while the fabrial is off, you can turn it around. Hence we can be sure that aluminium is not needed for that. It also means that we just cannot look at the reed alone. The board seems to be what you call the "cage" in conventional fabrials.

[StanLemon]

I think too many people here are assuming it's a simple task for the lattices to be turned off and on. Each lattice is described as a series of gems. It's probably much simpler and quicker to use aluminum than going through the process of shutting off and turning on the lattices. Keep in mind this is still very early development of this technology, it's probably safer to use the aluminum than turning them off and risking that they won't reconnect. 

Additionally, for those concerned about the curvature of the planet, that is fairly simple and I think people are over thinking things. The ship is still influenced by gravity, all the fabrial is doing is keeping the ship suspended a height relative to the distance that the lattice has moved.

[+Bzhydack]

7 hours ago, Oltux72 said:

That means that directions are relative.

Not necesserly. If Spanreed moves in relation to the core of the planet (center of gravity), it will automaticly correct curvature.

8 hours ago, Oltux72 said:

The board seems to be what you call the "cage" in conventional fabrials.

We know that board is interchageable, so  no.

[Quantus]

13 hours ago, Oltux72 said:

That means that directions are relative. The basic information is there. It means that while the fabrial is off, you can turn it around. Hence we can be sure that aluminium is not needed for that. It also means that we just cannot look at the reed alone. The board seems to be what you call the "cage" in conventional fabrials.

 

5 hours ago, Bzhydack said:

Not necesserly. If Spanreed moves in relation to the core of the planet (center of gravity), it will automaticly correct curvature.

We know that board is interchageable, so  no.

With confirmation that they align to the board on activation, I think the explanation can be pretty mundane: we know there is a standard socket on the board for the spanreed to sit in and be returned to when control is passed, and this is how they align the inkwells and things.  All we have to assume is that the standard socket is not a symmetrical shape, then each time it is placed in the socket it would align the reed to the relative rotation as well as the vertical axis, letting it always find the inkwell and things like that.

Going from there, the sequence of the subsequent breakthough's makes some logical sense.  They first discovered how to reverse a single plane of motion, but still had to deal with an all or nothing Connection.  Then they learned how to suppress individual axis entirely, which taken to the logical next step lets them isolate motion to a single axis.  Then once they started playing with single-vector fabrial's they learned how to actually redirect that vector.  

These are the sorts of incremental advances that you see in early exploratory development, not unlike the sorts of early electrical devices academics played with in the 18th and 19th centuries.  And WOB says he introduced the term fabrials specifically to become a generic Cosmere term for Mechanical Investiture Device, which by Era4 where the cultures are mixing will likely operate on some mix of the 4 main magics (Gem Fabrials, Medallion/Ettmetal Tech, Aon's Etc, Awakened Devices).  By then the level of complexity will almost certainly be comparable to the gap between those early Layden Jar and static generator systems and modern electronics.  Which is to say barely recognizable and basically Magic compared to the early "technology".  

Edited August 21, 2020 by Quantus
Awful spelling...

[Chiberty]

I think I've found a pretty simple solution that, as far as I can tell, fits with the functions of conjoiners and reversers that we have seen, along with Navani's explanations. One of the points brought up was how the spanreeds might take into account cardinal directions, since if direction was only dependent on the rotation of the gemstone, the archer tower designs would not be very practical, since that would mean that they could have pulled gemstones to the side to make the archers go up. However, involving cardinal directions also has issues, not only because spanreed boards are not noted to all face the same direction, but also because it would lead to very odd behavior, especially closer to the poles.

The simplest explanation I could think of that solves both of these is that lateral movement is dependent on the rotation of the gemstones, while vertical movement is always relative to the net gravitational force on the fabrial. This way, the only way to move a conjoined gemstone up or down would be to move its corresponding gemstone up or down, solving the issue with the archer towers. This would also allow spanreed boards to be oriented any direction as long as they are level.

The other main issue pointed out has been that if the lateral movement of the gemstones was just related to rotation, the Fourth Bridge chull lattice operators could just disconnect their gemstones and turn them around if they wanted to go the ther direction, without any need for aluminum. However, that is not exactly true. If the chull drivers wanted to turn off their gemstones, the pulley operator would have to turn theirs on for a moment, holding the weight of the Fourth Bridge until the chulls were all turned around and reconnected. While that would still work, it would mean that there would be an extended pause in the ship's movement every once in a while. This issue actually solves a different one. Navani talks about how using "aluminum to isolate motion along a plane" was somehow connected to the method by which the chull-pulled gemstones could be temporarily disjoined. While those two things don't seem to be related, the issue that I just pointed out means that it can be. If they are able to confine a gemstone's reaction to vertical movement, the ship can still be held up while the chulls are changing direction, without having to pause and wait for the pulley operators to switch with them in bearing the ship's load. The pulley operators would just be able to bear the load the whole time, and the the two lattices being alternated would only need to take place when they want to change the ship's vertical position, so the chulls don't get lifted into the sky.

Edited August 21, 2020 by Chiberty

[Quantus]

On 8/21/2020 at 10:43 AM, Chiberty said:

The other main issue pointed out has been that if the lateral movement of the gemstones was just related to rotation, the Fourth Bridge chull lattice operators could just disconnect their gemstones and turn them around if they wanted to go the ther direction, without any need for aluminum. However, that is not exactly true. If the chull drivers wanted to turn off their gemstones, the pulley operator would have to turn theirs on for a moment, holding the weight of the Fourth Bridge until the chulls were all turned around and reconnected. While that would still work, it would mean that there would be an extended pause in the ship's movement every once in a while. This issue actually solves a different one. Navani talks about how using "aluminum to isolate motion along a plane" was somehow connected to the method by which the chull-pulled gemstones could be temporarily disjoined. While those two things don't seem to be related, the issue that I just pointed out means that it can be. If they are able to confine a gemstone's reaction to vertical movement, the ship can still be held up while the chulls are changing direction, without having to pause and wait for the pulley operators to switch with them in bearing the ship's load. The pulley operators would just be able to bear the load the whole time, and the the two lattices being alternated would only need to take place when they want to change the ship's vertical position, so the chulls don't get lifted into the sky.

Precisely.  The tower-side pulley system is always on and supporting the vertical weight of the Forth Bridge, that is never the chull's job.  The whole point of the isolation breakthrough was that it let them have two separate latices that both effect different planes of motion at the same time: the tower pulley supports the full weight of the bridge, refugees, and supplies while the chull system is just there to provide lateral motion in the the way they would pulling a wagon.   

Though I think the whole point is that the chulls will never see any of the vertical motion, so being lifted is not an issue.  From what I can tell they only ever disconnect the chulls to reset their walking laps, and never disable the vertical support at all.  

Edited August 24, 2020 by Quantus

[+Oltux72]

On 21/08/2020 at 4:43 PM, Chiberty said:

This would also allow spanreed boards to be oriented any direction as long as they are level.

Raising the question why they need to be level.

On 21/08/2020 at 4:43 PM, Chiberty said:

Navani talks about how using "aluminum to isolate motion along a plane" was somehow connected to the method by which the chull-pulled gemstones could be temporarily disjoined. While those two things don't seem to be related, the issue that I just pointed out means that it can be. If they are able to confine a gemstone's reaction to vertical movement, the ship can still be held up while the chulls are changing direction, without having to pause and wait for the pulley operators to switch with them in bearing the ship's load. The pulley operators would just be able to bear the load the whole time, and the the two lattices being alternated would only need to take place when they want to change the ship's vertical position, so the chulls don't get lifted into the sky.

Yet it raises another questions. Why do they need chulls at all? You could do the lateral movement with a pulley, too.

It looks to me like we need to conclude that conjoiners react to gravity and you cannot rotate with respect to it.

[Chiberty]

4 hours ago, Oltux72 said:

It looks to me like we need to conclude that conjoiners react to gravity and you cannot rotate with respect to it.

I agree--that's one of the points I made.

[Pagerunner]

Dawnshard update:

Spoiler

Looking back at the Brandon's progress bar updates, the first draft of the novella was completed in late August. I wonder if Brandon and his team were aware of this thread and added some content specifically for us, since there's some very detailed info on conjoiners and reversers.

We've got the "frame of reference" being a perception issue:

Quote

“But when the ship goes down,” Rysn said, pointing
at the other ring, “shouldn’t it go up?”
“Yes, theoretically,” Rushu said. “But it doesn’t.
Only your movements affect it. We believe this has to
do with the frame of reference, as applied to the person
moving the hoop. Spren, it should be noted, have
a curious relationship to our perception of them and
their motions. You see both of these hoops in the same
frame of reference, so they act together. It’s why the
motion and curve of the planet don’t influence spanreeds.
“It’s proven impossible for someone on a ship with a
spanreed to see themselves in the same frame of reference
as the person receiving the communication. Perhaps
there is a way to train ourselves, but no one has
discovered it. Indeed, even the size of the ship can
influence these things. If you tried this experiment on
a rowboat, for example, the results could be different.”

We've got aluminum as an explicit part of the conjoiner cage:

Quote

“Lopen,” Huio said in Herdazian. “This aluminum
has fascinating properties; I believe the captive spren
are reacting to its presence, almost like prey react to a
predator. When I touch this foil to the stone, they
push to the other side of their confines. I hypothesize
that the aluminum interferes with their ability to
sense not only my thoughts of them, but the thoughts
of their conjoined half.”
“You know, cuz,” Lopen

And we've got the partial decoupling (which I'll admit I thought wasn't necessary for Fourth Bridge operation, although I think I hedged my bets earlier in the thread and said I was expecting to see it eventually):

Quote

“Well, maybe not all things,” Rushu said. “But yes.
This is important. Rysn, the aluminum is interfering
with the mechanism, making the conjoinment uneven.
The paired rubies still transfer vertical movement,
but not lateral movement. So you will go up and
down with the motion of the anchor, but then can
move laterally in any direction you want.”

...

“Hmmm,” Rushu said. “You had to turn the anchor
to spin. The mechanism must still have rotation conjoined;
perhaps by experimenting with the aluminum
we can fix that. At any rate, this is an amazing development.”

This still does not explain the mechanism for the temporary disjoining phenomenon required to reorient the chulls' lattice, and why nothing fancy is needed for cardinal orientation of spanreeds.

 

[Jofwu]

I loved what Dawnshard gave us on all this, but it definitely didn't clear things up for me...

Spoiler

I don't love it, but I can accept the perception explanation. It's a soft, flexible answer that makes sense. I'm still not clear on the deeper issues here though. I feel like there's a subconsious level of perception involved, because I don't think you can merely "try hard enough" to pretend you're not on a ship and suddenly your spanreed works like it's not on a ship. You need some god-tier mental control to pull that off I imagine, if it's possible at all.

I did notice a mention of Rysn "orienting" her spanreed and board. However, the meaning of that is somewhat ambiguous and this all definitely leaves me FEELING like cardinal directions don't matter. I can orient my board in any direction and "forward for me" is "forward for you" no matter what our compass headings say. My primary issue with this came down to the idea that you could make Reversers effectively irrelevant with such flimsy use of perception. I mentioned a simple thought experiment: we put two spanreeds in adjacent rooms with their boards pointed opposite directions, start using them, then we lower the partition. Have we created a Reverser? I think this application of perception says not. The fabrials are objectively not Reversers, so I think when the partition is lowered, and SOMEONE perceives what's actually happening, they will no longer work as they did. I could live with that.

It does leave some ambiguity though, which I don't love. Spanreeds have an obvious orientation for their usage. What if I put a Conjoiner hanging from the middle of a rope and have two groups play tug of war? Which way is forward and which backward? Or what if I accidentally drop a Conjoiner's pair somewhere in the middle of an empty field, and after a long walk I take out my Conjoiner and move it "forward"? What direction does the pair move, with no human there to perceive a frame of reference? The only explanation I can think of is that it falls back on cardinal directions in such cases, with those being generally perceived by the local sapient beings as a deeper, more fundamental frame of reference.

I dunno, it's just not entirely clear to me.

Now, the usage of aluminum was MUCH more clear I think. Applying aluminum in a certain way simply blocks the conveyance of movement in that direction. Wrap a spanreed with aluminum to block X-direction movement and the pair only moves in the YZ-plane. I have to assume we can extrapolate this to block a second direction such that the pair only moves along a single axis. And we can do these same things with the rotational compoenent as well. This all seems very straightforward...

Until I look back at the Fourth Bridge. Because now I don't at all understand what their problem was. Plains Lattice would have vertical movement blocked. Urithiru Lattice would have horizontal movements blocked. Easy. Now the Fourth Bridge can go up without affecting the Plains Lattice and it can go sideways without affecting the Urithiru lattice. Can even make both of these movements simultaneously, right?

And then there was the whole bit about needing aluminum for the turnaround. Why not just turn the Plains Lattice off, turn the chulls around, and keep going "forward"? Is it just because the combined perception of all the people (and chulls?) involved says "we're going the other way now" which makes the Fourth Bridge go backwards? And aluminum somehow allows them (in a totally distinct application) to circumvent the perception? Or is it really just a matter of them wanting the Fourth Bridge to be constantly moving, so they need aluminum to turn around without making the Fourth Bridge turn around. (that is, they just want the "forward" component and can't be troubled to stop the ship every few once in a while.)