Air travel on Roshar

[CosmereMaths]

In this post I’m gonna talk a little about the math of flying around Roshar. Firstly from Khriss’s annotation in arcanum unbounded “Roshar (the planet) is .7 cosmere  standard in gravitation and .9 in size”. I’m going to assume that “cosmere standard” is Earth (This also means Roshar is less dense than earth as a version of Earth at .9 size would have .93 Earth gravity). Additionally, the length of Roshar (the continent) is estimated at about 4000 miles wide and half as tall. I can’t tell how dense the atmosphere is compared to Earth but I would guess it less but since I don’t have much to go off off I will use earth atmospheric density. 
       Human beings fall on Earth with a terminal velocity of about 120 mph  or 54 m/s which they reach in 12 seconds of free fall. Atmospheric resistance is a function of speed cubed which means at .7 gravity with normal air density terminal velocity would fall to 107 mph or 48 m/s.

According to these numbers, Kaladin should be able to fall from Natanatan to Shinovar in 37 hours using a single lashing. A double lashing is not much better as then he would fly at 134 mph and make the trip in 29 hours. In fact if Kaladin is concerned with conserving stormlight he should actually fall at less than a full lashing.

All of this changes when we add Abrasion to the equation.  When Lift becomes awesome she has been seen to not only remove sliding friction but air resistance as well as everything brushes around her. So assuming a Windrunner or Skybreaker pair up with an Edgedancer or Dustbringer, then they can fall much farther. In fact with a single lashing completely frictionless Kaladin and Lift can fall from Natanatan to Shinovar in 22 minutes. Because distance would now function as a square of time traveling instead of linear with terminal velocity. This seems like a huge deal that the radiants should be taking advantage of.  
 

Side note: Kaladin at a double lashing can reach light speed in space in 8 months

Edited July 25, 2022 by Stoneshaper
Clearing up confusion on Roshar planet vs continent

[NameIess]

27 minutes ago, Stoneshaper said:

In this post I’m gonna talk a little about the math of flying around Roshar. Firstly from Khriss’s annotation in arcanum unbounded “Roshar is .7 cosmere  standard in gravitation and .9 in size”. I’m going to assume that “cosmere standard” is Earth (This also means Roshar is less dense than earth as a version of Earth at .9 size would have .93 Earth gravity). Additionally, the length of Roshar is estimated at about 4000 miles wide and half as tall. I can’t tell how dense the atmosphere is compared to Earth but I would guess it less but since I don’t have much to go off off I will use earth atmospheric density. 
       Human beings fall on Earth with a terminal velocity of about 120 mph  or 54 m/s which they reach in 12 seconds of free fall. Atmospheric resistance is a function of speed cubed which means at .7 gravity with normal air density terminal velocity would fall to 107 mph or 48 m/s.

According to these numbers, Kaladin should be able to fall from Natanatan to Shinovar in 37 hours using a single lashing. A double lashing is not much better as then he would fly at 134 mph and make the trip in 29 hours. In fact if Kaladin is concerned with conserving stormlight he should actually fall at less than a full lashing.

All of this changes when we add Abrasion to the equation.  When Lift becomes awesome she has been seen to not only remove sliding friction but air resistance as well as everything brushes around her. So assuming a Windrunner or Skybreaker pair up with an Edgedancer or Dustbringer, then they can fall much farther. In fact with a single lashing completely frictionless Kaladin and Lift can fall from Natanatan to Shinovar in 22 minutes. Because distance would now function as a square of time traveling instead of linear with terminal velocity. This seems like a huge deal that the radiants should be taking advantage of.  
 

Side note: Kaladin at a double lashing can reach light speed in space in 8 months

Eliminating friction, which is what Abrasion is supposed to do, shouldn't completely eliminate air resistance, as you still need to push the air out of the way.

[CosmereMaths]

1 hour ago, Nameless said:

Eliminating friction, which is what Abrasion is supposed to do, shouldn't completely eliminate air resistance, as you still need to push the air out of the way.

Like most of the surges, friction isn’t a real force. It only exists on the macro scale as an extrapolation of the electro magnetic force. Even if you covered someone in oil they wouldn’t slide perfectly over a surface. I only say abrasion surgebinders can eliminate air resistance because we’ve seen Lift do it on multiple occasions. Most notably the battle of Thaylen field we see Lift pass perfectly through air

[NameIess]

Just now, Stoneshaper said:

Like most of the surges, friction isn’t a real force. It only exists on the macro scale as an extrapolation of the electro magnetic force. Even if you covered someone in oil they wouldn’t slide perfectly over a surface. I only say abrasion surgebinders can eliminate air resistance because we’ve seen Lift do it on multiple occasions. Most notably the battle of Thaylen field we see Lift pass perfectly through air

Abrasion completely eliminating air resistance doesn't make sense given what we know it's supposed to do. reducing it noticeably (particularly at low speeds) does make sense, according to my admittedly limited understanding of physics.

[CosmereMaths]

1 hour ago, Nameless said:

Abrasion completely eliminating air resistance doesn't make sense given what we know it's supposed to do. reducing it noticeably (particularly at low speeds) does make sense, according to my admittedly limited understanding of physics.

Here’s a quote from Edgedancer Chapter 1:

“She set her jaw and stood up. Wyndle was still talking, but she ignored him, instead taking off across the deserted field, running as fast as she could, startling grass. She reached the top of a small hill, then jumped and coated her feet with power. She started slipping immediately. The air. The air she pushed against when moving was holding her back. Lift hiss then coated her entire self in power. She sliced through the wind, turning sideways as she skidded down the side of the hill. Air slid off her, as if it couldn’t find her. Even the sunlight seemed to melt of her skin. She was between places, here but not. No air, no ground. Just pure motion, so fast that she reached grass before it had time to pull away, it’s touch brushed aside by her power.”

 

[NameIess]

Just now, Stoneshaper said:

Here’s a quote from Edgedancer Chapter 1:

“She set her jaw and stood up. Wyndle was still talking, but she ignored him, instead taking off across the deserted field, running as fast as she could, startling grass. She reached the top of a small hill, then jumped and coated her feet with power. She started slipping immediately. The air. The air she pushed against when moving was holding her back. Lift hiss then coated her entire self in power. She sliced through the wind, turning sideways as she skidded down the side of the hill. Air slid off her, as if it couldn’t find her. Even the sunlight seemed to melt of her skin. She was between places, here but not. No air, no ground. Just pure motion, so fast that she reached grass before it had time to pull away, it’s touch brushed aside by her power.”

That never directly states that she eliminated air resistance completely.

[Frustration]

14 hours ago, Nameless said:

That never directly states that she eliminated air resistance completely.

But it doesn't even hint that it's still there. And I would say it goes even further than that.

[NameIess]

10 minutes ago, Frustration said:

But it doesn't even hint that it's still there. And I would say it goes even further than that.

If Abrasion pushes the air aside to eliminate air resistance, then it will also take massive amounts of Stormlight at high speeds. Still not all that useful. The only scenario in which an Edgedancer/Windrunner combo allows for uncapped flying speed with very little Stormlight is if Brandon decides to ignore physics.

[Frustration]

44 minutes ago, Nameless said:

If Abrasion pushes the air aside to eliminate air resistance, then it will also take massive amounts of Stormlight at high speeds. Still not all that useful. The only scenario in which an Edgedancer/Windrunner combo allows for uncapped flying speed with very little Stormlight is if Brandon decides to ignore physics.

Well gravity in a direction rather than towards an object already breaks physics, so I don't think that's a problem.

[NameIess]

20 minutes ago, Frustration said:

Well gravity in a direction rather than towards an object already breaks physics, so I don't think that's a problem.

No, Gravitation is an addition to physics. It takes a proportionate amount of energy from Investiture in order to change. At high velocities, pushing air aside to remove terminal velocity would take tons of energy, and would likely be just about as efficient as simply lashing yourself more.

[Frustration]

Just now, Nameless said:

No, Gravitation is an addition to physics. It takes a proportionate amount of energy from Investiture in order to change. At high velocities, pushing air aside to remove terminal velocity would take tons of energy, and would likely be just about as efficient as simply lashing yourself more.

Gravitation breaks physics as much or more than completely removing air resistance.

The planets gravity is overridden by a half lashing, but you still maintain your position relative to the planet. You are affected by gravity nothing else is. You have the affect of gravity equal to the planet without any interference from the planet. Etc.

[NameIess]

Just now, Frustration said:

Gravitation breaks physics as much or more than completely removing air resistance.

The planets gravity is overridden by a half lashing, but you still maintain your position relative to the planet. You are affected by gravity nothing else is. You have the affect of gravity equal to the planet without any interference from the planet. Etc.

And it takes a proportionate amount of energy to do so. If Abrasion took a proportionate amount of energy to remove air resistance, it would use too much to be practical at high speeds.

[Frustration]

47 minutes ago, Nameless said:

And it takes a proportionate amount of energy to do so. If Abrasion took a proportionate amount of energy to remove air resistance, it would use too much to be practical at high speeds.

Unless storm light is more energy dense than black holes it really doesn't. It is only possible with use of the three realms, something I assume would be at work with Abrasion as well.

[NameIess]

37 minutes ago, Frustration said:

Unless storm light is more energy dense than black holes it really doesn't. It is only possible with use of the three realms, something I assume would be at work with Abrasion as well.

Surges work by using Stormlight to do something. In the case of Gravitation, Stormlight is converted into kinetic energy. In order for Abrasion to push air out of the way and completely eliminate air resistance, it would have to do the same. Just as using a bunch of lashings to move something takes a bunch of Stormlight, so too would using Abrasion to move air out of the way while at incredibly high speeds. Unless you have some more energy-efficient way for Abrasion to eliminate air resistance, that is even slightly related to how Abrasion is stated to work?

[Frustration]

1 hour ago, Nameless said:

Surges work by using Stormlight to do something. In the case of Gravitation, Stormlight is converted into kinetic energy.

No, it is used to override the spiritual gravitation of the planet and generate a new gravitational body that will only affect the user. I can't link the WoB right now, but I'll try and get around to it.

1 hour ago, Nameless said:

Unless you have some more energy-efficient way for Abrasion to eliminate air resistance, that is even slightly related to how Abrasion is stated to work?

I'll use coding terms because that's the best way I can describe it, but basically you turn collisions off.

[NameIess]

1 minute ago, Frustration said:

No, it is used to override the spiritual gravitation of the planet and generate a new gravitational body that will only affect the user. I can't link the WoB right now, but I'll try and get around to it.

Yeah, it does that. And the end result is kinetic energy.

3 minutes ago, Frustration said:

I'll use coding terms because that's the best way I can describe it, but basically you turn collisions off.

So they phase?

[CosmereMaths]

4 hours ago, Nameless said:

If Abrasion pushes the air aside to eliminate air resistance, then it will also take massive amounts of Stormlight at high speeds. Still not all that useful. The only scenario in which an Edgedancer/Windrunner combo allows for uncapped flying speed with very little Stormlight is if Brandon decides to ignore physics.

That’s something I hadn’t considered, I don’t know if we have anything in the books to imply that Edgedancer or Dustbringers burn more stormlight while going faster. I view them slicking their bodies” as similar to a light weaving in that once it’s done it take little stormlight to maintain; however given that’s it’s never explicitly described in the books it’s open to interpretation.

[NameIess]

1 minute ago, Stoneshaper said:

That’s something I hadn’t considered, I don’t know if we have anything in the books to imply that Edgedancer or Dustbringers burn more stormlight while going faster. I view them slicking their bodies” as similar to a light weaving in that once it’s done it take little stormlight to maintain; however given that’s it’s never explicitly described in the books it’s open to interpretation.

Well, eliminating friction will always take the same amount of Stormlight. However, actively pushing the air away, which is required to completely eliminate air resistance will require a ton of energy, which can't just come from nowhere unless Brandon's breaking the rules that he's established.

[CosmereMaths]

26 minutes ago, Frustration said:

No, it is used to override the spiritual gravitation of the planet and generate a new gravitational body that will only affect the user. I can't link the WoB right now, but I'll try and get around to it.

I'll use coding terms because that's the best way I can describe it, but basically you turn collisions off.

The excerpt I shared seems to show lift “phasing” almost especially the part about not feeling even the sunlight, however she still hits a tree and collapses right after, so she’s not phasing perfectly. Like all cosmere magic I think it has to do with perception, in fact I believe if an Edgedancer or Dustbringer thought about the normal force(which on earth comes from electrons repelling electrically but who knows in the cosmere) as friction then they could probably phase through anything. Or perhaps they would need to convince all of most humans (or sentient species) on Roshar. Then they only thing stopping lift from phasing through trees is a physics lesson.
Abrasion is one of the more complicated surges. Actually gravitation is the only physical one that really makes sense in that it obviously makes no sense at all but can be thought about pretty clearly. And transportation, light weaving, and soulcasting are so far from reality and more just magic that basically anything goes. In reality there are at most 4 known forces, gravity, electromagnetism, strong nuclear, weak nuclear. ( which I think makes coinshots and lurchers surgebinders). 
Wyndle at one point tells Lift that if she uses progression and grows food, then eats it and converts the back into investiture she would lose energy some in the process or at best break even if nothing was lost; that the cosmere version of conservation of energy. This however seems to fall apart under scrutiny. Soulcasting objects should cost stormlight according to the changed energy of the soulcast. (Chemical potential, gravitational potential, nuclear potential?? or perhaps axial potential) but which should cost way more stormlight when increasing mass then every Windrunner and there squires flying around the world at a quadruple lashing a hundred times. Unless I assumed to Roshar system is far from any supermassive objects like being in a galaxy or something. And that the axial forces are really weak. 

[CosmereMaths]

14 minutes ago, Nameless said:

Well, eliminating friction will always take the same amount of Stormlight. However, actively pushing the air away, which is required to completely eliminate air resistance will require a ton of energy, which can't just come from nowhere unless Brandon's breaking the rules that he's established.

Then removing ground friction should require more stormlight at higher speeds too. Although the force of friction does not change with velocity, the change in energy when encountering ground friction increases at higher speeds because of the relation between speed and energy

[NameIess]

1 minute ago, Stoneshaper said:

Then removing ground friction should require more stormlight at higher speeds too. Although the force of friction does not change with velocity, the change in energy when encountering ground friction increases at higher speeds because of the relation between speed and energy

If you remove friction completely, then it won't matter how fast you move, because no friction means there'll still be no energy exerted against you.

[CosmereMaths]

8 minutes ago, Stoneshaper said:
Wyndle at one point tells Lift that if she uses progression and grows food, then eats it and converts the back into investiture she would lose energy some in the process or at best break even if nothing was lost; that the cosmere version of conservation of energy. This however seems to fall apart under scrutiny. Soulcasting objects should cost stormlight according to the changed energy of the soulcast. (Chemical potential, gravitational potential, nuclear potential?? or perhaps axial potential) but which should cost way more stormlight when increasing mass then every Windrunner and there squires flying around the world at a quadruple lashing a hundred times. Unless I assumed to Roshar system is far from any supermassive objects like being in a galaxy or something. And that the axial forces are really weak. 

Ever since I read that quote from Wyndle I’ve wondered how all cosmere magics or energy neutral. I don’t even know what powers awakening but it seems like awakened objects can move forever 

[Frustration]

52 minutes ago, Nameless said:

So they phase?

Phasing is not quite the term I would use, but "Drifts slightly between the realms so as to change their interaction with matter in a way that breaks physics about as much as Iron feruchemy" doesn't have quite the same ring to it.

Basically yes.

[NameIess]

3 minutes ago, Frustration said:

Phasing is not quite the term I would use, but "Drifts slightly between the realms so as to change their interaction with matter in a way that breaks physics about as much as Iron feruchemy" doesn't have quite the same ring to it.

Basically yes.

Then why does it only work for air?

[CosmereMaths]

4 minutes ago, Nameless said:

Then why does it only work for air?

Best answer: cause of perception stuff. The surges are what people believe the forces of nature to be. Air restistance and friction and the fact that cups don’t fall through the table when you put them down are all the same force but people view them differently. Best I can tell Rosharans consider air resistance and ground friction as abrasive forces but not the normal force