Heavinly ones and feruchemical iron

[Sythrin]

We know heavinly ones can only themselfs ones but can basicly perpetually lash themselfs and never touch the ground.

Its not entirely clear how their power works, but they spend none or very little ammount of voidlight.

What would happen if one had access to feruchemical Iron and could change their weight?

Would they need to spend more voidlight when they weigh more or could they abuse this power and slam into things with their spear with much more force?

[Treamayne]

44 minutes ago, Sythrin said:

We know heavinly ones can only themselfs ones but can basicly perpetually lash themselfs and never touch the ground.

Its not entirely clear how their power works, but they spend none or very little ammount of voidlight.

All fused, not just Heavenly Ones have an Active and a Passive use of their Surge. The Passive use does not consume Stormlight, while the Active use does. For Heavenly Ones, this means that lashing themselves is Passive, while lashing objects or other people is Active. We do not know how that would interact with F-Iron, because it is possible that "investiture interfers with investiture" may apply and cause lashing themselves to become an active Lashing while also tapping Iron. I have not been able to find a WoB about Feruchemy interacting with Surges (Human, Singer or Fused), but here's the WoB about Active and Passive Surges:

Spoiler

Argent

I've been trying to figure out how the Fused and the Regals get their Voidlight. Heavenly Ones seem to be able to levitate indefinitely unless they heal, which presumably expends their Light. But then the Pursuer needs to go get spheres. And then there's the Song of Prayer, which I don't understand at all.

Brandon Sanderson

All of the Fused have an active and an inactive way to use their Voidlight. For some of them, one is way more dramatic than the other. So you should be watching for the different brands of Fused to each have that. If they don't use it actively, they get a passive effect. And if they do use it actively, it runs out. So watch for that with them.

They each only have one power, as opposed to Knights Radiant, but they have the staying power of consistency depending on what they are.

The Song of Prayer. Let's just say that Odium likes his Fused being reliant upon him. Does that make sense?

Argent

I think it does. My assumption has been that anyone can just sing the song and ask for Investiture.

Brandon Sanderson

Yes, this is true, because most of the time he's not going to be paying direct attention, and it's just going to... yeah.

JordanCon 2021 (July 17, 2021)

Hope that helps

[alder24]

1 hour ago, Sythrin said:

We know heavinly ones can only themselfs ones but can basicly perpetually lash themselfs and never touch the ground.

Its not entirely clear how their power works, but they spend none or very little ammount of voidlight.

What would happen if one had access to feruchemical Iron and could change their weight?

Would they need to spend more voidlight when they weigh more or could they abuse this power and slam into things with their spear with much more force?

There are 2 WoBs on that, but Lashings and Feruchemical iron are two separate, yet slightly connected effects. Lashing changes the gravitational acceleration, F-iron changes just mass. For acceleration to produce a force, you need mass, but because you can't store 100% of your mass with F-iron, you will always feel the same acceleration, no matter your mass. The only thing that will change is the amount of investiture needed to produce this acceleration, as with higher mass you will need more investiture (because more energy is required to move that mass).

But as Treamayne said, Fused passive effect allows them to Lash themselves without consuming investiture, so F-iron wouldn't change a lot for them. It could only increase their maneuverability and help them turn or decelerate faster, it would also work with conservation of momentum like it works for Wax - decreasing your mass while moving would increase your speed and vice versa. But it would have no effect on their acceleration and investiture consumption rate.

For a Radiant though, I suspect the effect would be based on intent. What I mean by this is that if they Lash themselves up with 1 g and then double their weight, the energy has to be conserved, so only two possibilities are viable. Either their Lashing would decrease to that of 0.5 g, but the consumption of Stormlight doesn't change (twice the mass requires twice the energy to lift), or your intent is to have a 1 g Lashing up and you would double the amount of Stormlight consumed to maintain that 1 g Lashing. But you can't increase your mass and maintain the same acceleration without consuming more Stormlight because the energy needed to accelerate this newly gained mass has to come from somewhere.

Spoiler

Bat_Mannington

If a Windrunner lashed Wax upwards, could he dump all of his weight into his metalminds and be unaffected or would the lashing affect his clothes and whatever else he had on him too?

Brandon Sanderson

Wax could mitigate the effect (unless he was in a vacuum) but not eliminate it completely.

faragorn

Vacuum or freefall?

It can be easy to confuse them in the context of surface to orbit.

Brandon Sanderson

I was talking about a Vacuum, but it's good to clarify. What I'm saying is that without wind resistance, his mass doesn't matter--and the books have established that what Wax does is a freakish transformation of his mass, not just his weight.

Kaladin changes how much gravity pulls on someone, and in what direction. Wax (basically, it's more complex than this) changes how much mass he has. The two, then, have some very distinctive effects.

Worldbuilders AMA (Dec. 5, 2015)

 

Spoiler

clyguy

If Wax were to go to Roshar, and--he's a Skimmer, right? So he can change his weight--if he got Lashed in a different direction if he Stored his weight would that nullify some of the Lashing?

Brandon Sanderson

Okay, you're going to make me think through this. *laughter* So Wax actually changes mass. And the Lashing only affects gravitational pull. So the answer is no because different things with different masses fall at the same speed.

Shadows of Self release party (Oct. 5, 2015)

 

[Sythrin]

7 hours ago, Treamayne said:

All fused, not just Heavenly Ones have an Active and a Passive use of their Surge. The Passive use does not consume Stormlight, while the Active use does. For Heavenly Ones, this means that lashing themselves is Passive, while lashing objects or other people is Active. We do not know how that would interact with F-Iron, because it is possible that "investiture interfers with investiture" may apply and cause lashing themselves to become an active Lashing while also tapping Iron. I have not been able to find a WoB about Feruchemy interacting with Surges (Human, Singer or Fused), but here's the WoB about Active and Passive Surges

Its so bad we have barely seen other fused in action. The devastating ones we have yet to see. And from most fused we have only seen the passive ability. I ask my self for the teleporting ones, what their passive is, as their teleporting obviously uses voidlight.

[Heilven he/him]

On 7/17/2025 at 8:14 AM, alder24 said:

For a Radiant though, I suspect the effect would be based on intent. What I mean by this is that if they Lash themselves up with 1 g and then double their weight, the energy has to be conserved, so only two possibilities are viable. Either their Lashing would decrease to that of 0.5 g, but the consumption of Stormlight doesn't change (twice the mass requires twice the energy to lift), or your intent is to have a 1 g Lashing up and you would double the amount of Stormlight consumed to maintain that 1 g Lashing. But you can't increase your mass and maintain the same acceleration without consuming more Stormlight because the energy needed to accelerate this newly gained mass has to come from somewhere.

I actually disagree, for two separate reasons.

Firstly, I believe that most of the surges don't actually use investiture as their fuel source. If I am explicitly wrong about this then I'm easily disproven on this point. Regardless, I think that the investiture involved in the surges is necessary to impose a change in the cognitive or spiritual essence of a target. The energy required for this would therefore come from the environment, which is why I believe frost so often appears when radiants do something particularly spectacular. There are certainly notable exceptions for this rule, but it is rather consistent with most radiant abilities. In this framework if one were to be lashed, then change their mass, no extra investiture should be necessary. There is a lot of room for interpretation here though, as I'm not certain if it is known whether the variation in investiture required to lash an object is tied to mass explicitly. It certainly makes sense, but I could also see volume, as the target's cognitive perception of its own size is likely the most important culprit. Regardless, I doubt that an object which sees itself as lashed upward would change its perception without running out of the investiture involved in the lashing.

 

Secondly, lashings are supposed to work like gravity, and thus a lashing shouldn't impart momentum or energy into the target. We know that depictions of g-force or forces due to lashings are due to the underlying mechanics not being fully thought out (to the general relativistic level that is. That's pretty far to think something out). So there's an issue here in whether we consider all of the evidence for lashings as a force as canon, or something to be ignored. I have my hand firmly in both camps, so I don't really care if Sanderson retcons this or not. If he does, then this point exists. If lashings are considered to be forces, then this point is moot. I do personally believe that most of the whoopsys could be written off as your cognitive self reacting as it thinks it should, rather than reality, but it's totally up to Sandy.

[DoctaDajman]

On 7/17/2025 at 5:56 AM, Treamayne said:

All fused, not just Heavenly Ones have an Active and a Passive use of their Surge. The Passive use does not consume Stormlight, while the Active use does. For Heavenly Ones, this means that lashing themselves is Passive, while lashing objects or other people is Active. We do not know how that would interact with F-Iron, because it is possible that "investiture interfers with investiture" may apply and cause lashing themselves to become an active Lashing while also tapping Iron. I have not been able to find a WoB about Feruchemy interacting with Surges (Human, Singer or Fused), but here's the WoB about Active and Passive Surges:

  Reveal hidden contents

Argent

I've been trying to figure out how the Fused and the Regals get their Voidlight. Heavenly Ones seem to be able to levitate indefinitely unless they heal, which presumably expends their Light. But then the Pursuer needs to go get spheres. And then there's the Song of Prayer, which I don't understand at all.

Brandon Sanderson

All of the Fused have an active and an inactive way to use their Voidlight. For some of them, one is way more dramatic than the other. So you should be watching for the different brands of Fused to each have that. If they don't use it actively, they get a passive effect. And if they do use it actively, it runs out. So watch for that with them.

They each only have one power, as opposed to Knights Radiant, but they have the staying power of consistency depending on what they are.

The Song of Prayer. Let's just say that Odium likes his Fused being reliant upon him. Does that make sense?

Argent

I think it does. My assumption has been that anyone can just sing the song and ask for Investiture.

Brandon Sanderson

Yes, this is true, because most of the time he's not going to be paying direct attention, and it's just going to... yeah.

JordanCon 2021 (July 17, 2021)

Hope that helps

The passive flight makes F-iron insane on them. You could store nearly 100% of your weight at all times if you are moving around via lashings. 

Honestly they are already insanely mobile and adept at flying. If you added on the ability to manipulate speed via conservation of momentum on top of that... completely bonkers the results they could achieve. Even if their passive use is limited in the amount of lashings they can use. 

The added weight would not damage any of the environment around them and so they could make themselves magnitudes heavier as they start their lashing only to cut down and boost acceleration even more. 

Now I am curious how quickly lashings can stop someone from falling... if you started at 100,000 lbs to rocket yourself forward by dropping your weight to nothing in the first moments of a lashing how hard would it be to negate all of the inertia when you want to slow down?  I guess you could always tap another 100,000 lbs to come to a near dead stop instantly. 

[Treamayne]

58 minutes ago, DoctaDajman said:

The passive flight makes F-iron insane on them. You could store nearly 100% of your weight at all times if you are moving around via lashings. 

Honestly they are already insanely mobile and adept at flying. If you added on the ability to manipulate speed via conservation of momentum on top of that... completely bonkers the results they could achieve. Even if their passive use is limited in the amount of lashings they can use. 

The added weight would not damage any of the environment around them and so they could make themselves magnitudes heavier as they start their lashing only to cut down and boost acceleration even more. 

Now I am curious how quickly lashings can stop someone from falling... if you started at 100,000 lbs to rocket yourself forward by dropping your weight to nothing in the first moments of a lashing how hard would it be to negate all of the inertia when you want to slow down?  I guess you could always tap another 100,000 lbs to come to a near dead stop instantly. 

Interesting theory - but it is just a theory.

We do not know that the MoIs interact like that - afterall, gravity affects a 1kg ingot and a 100kg ingot the same, they fall at the same rate with the same terminal velocity (excepting other factors like friction and wind resistance, of course). It could be that Sanderson will treat F-Iron as a Nonbo with the Surge of Gravitation. We do not yet have enough information to determine at this point. 

Edit: Duh Me

Edited August 19, 2025 by Treamayne
SPAG

[Heilven he/him]

35 minutes ago, Treamayne said:

Interesting theory - but it is just a theory.

We do not know that the MoIs interact like that - afterall, gravity affects a 1kg ingot and a 100kg ingot the same, they fall at the same rate with the same terminal velocity (excepting other factors like friction and wind resistance, of course). It could be that Sanderson will treat F-Iron as a Nonbo with the Surge of Gravitation. We do not yet have enough information to determine at this point. 

They do not fall at the same rate with the same terminal velocity. In fact if you neglect "other factors like friction and wind resistance" there will be no terminal velocity at all. Terminal velocity is achieved when the force due to gravity is equal to the resistance forces which oppose motion. A 100kg ingot has a higher terminal velocity because gravity pulls on heavier things more. Two objects with different masses in the absence of wind resistance will fall at the same rate, because the heavier object resists acceleration in such a way that the extra force cancels.

But I get what you mean.

[Treamayne]

6 minutes ago, Heilven said:

They do not fall at the same rate with the same terminal velocity. In fact if you neglect "other factors like friction and wind resistance" there will be no terminal velocity at all. Terminal velocity is achieved when the force due to gravity is equal to the resistance forces which oppose motion. A 100kg ingot has a higher terminal velocity because gravity pulls on heavier things more. Two objects with different masses in the absence of wind resistance will fall at the same rate, because the heavier object resists acceleration in such a way that the extra force cancels.

But I get what you mean.

Thank you - I meant gravitational acceleration and misspoke about terminal velocity. 

Spoiler

TOW: 

• In physics, gravitational acceleration is the acceleration of an object in free fall within a vacuum (and thus without experiencing drag). This is the steady gain in speed caused exclusively by gravitational attraction. All bodies accelerate in vacuum at the same rate, regardless of the masses or compositions of the bodies

My Apologies.

[DoctaDajman]

59 minutes ago, Treamayne said:

Thank you - I meant gravitational acceleration and misspoke about terminal velocity. 

  Hide contents

TOW: 

• In physics, gravitational acceleration is the acceleration of an object in free fall within a vacuum (and thus without experiencing drag). This is the steady gain in speed caused exclusively by gravitational attraction. All bodies accelerate in vacuum at the same rate, regardless of the masses or compositions of the bodies

My Apologies.

So outside of a vacuum this should all work? I would still think that at 1 lashing the speed of acceleration from gravity is the standard 9meters per second per second. I assume that cutting weight in half would simply double the speed the person is currently moving... if you did it at 1 second it would only double you from 9 meters per second to 18. 

Really the idea is that you could drastically reduce the time to terminal velocity which takes ~10 seconds to reach at 1 lashing. But this still would not accelerate you in the way that a coinshot would accelerate from a push. I think gravity just takes a while to ramp up flight speed. Anything to speed that up would be beneficial. 

The benefit to being an iron ferring and a heavenly one is that you could store millions and millions of lbs each day since you are floating anyways. 

You can cut a million in half a bunch of times to build ludicrous momentum with a single second of falling. 

[alder24]

16 hours ago, Heilven said:

Firstly, I believe that most of the surges don't actually use investiture as their fuel source. If I am explicitly wrong about this then I'm easily disproven on this point. Regardless, I think that the investiture involved in the surges is necessary to impose a change in the cognitive or spiritual essence of a target. The energy required for this would therefore come from the environment, which is why I believe frost so often appears when radiants do something particularly spectacular. 

This is wrong. All Surges use investiture as a fuel. Kaladin's Lashings consume his Stormlight, Shallan's Lightweaving also needs Stormlight and Shallan often binds it to a sphere that will feed it. Soulcasting consumes lots of Stormlight and all other Surges need a Radiant to have Stormlight with them otherwise Surges simply stop functioning. 

The frost appearing is mostly due to condensation and phase transition of investiture. There is only a very trace amount of investiture present in the environment, too little for even a Radiant to detect it and use it. 

Spoiler

Questioner

Why does Stormlight make things cold?

Brandon Sanderson

It’s not the Stormlight, it’s condensation because something is going directly from a gas into a solid. The coldness is caused by that, it’s not necessarily that the Stormlight is making things cold, but that the Shardblade is condensing.

Boskone 54 (Feb. 17, 2017)

 

16 hours ago, Heilven said:

Secondly, lashings are supposed to work like gravity, and thus a lashing shouldn't impart momentum or energy into the target. We know that depictions of g-force or forces due to lashings are due to the underlying mechanics not being fully thought out (to the general relativistic level that is. That's pretty far to think something out). So there's an issue here in whether we consider all of the evidence for lashings as a force as canon, or something to be ignored. I have my hand firmly in both camps, so I don't really care if Sanderson retcons this or not. If he does, then this point exists. If lashings are considered to be forces, then this point is moot. I do personally believe that most of the whoopsys could be written off as your cognitive self reacting as it thinks it should, rather than reality, but it's totally up to Sandy.

Matter is energy and in Cosmere it's also investiture. No matter if you describe gravity as a force or as a curvature of spacetime, you need energy to create this effect. Brandon also confirmed that laws of conservation of energy are working in Cosmere. Lashings were shown time and time again in books to feed on Stormlight, which is energy. Consequences of those things are quite simple - if you apply a Lashing on yourself and then change your mass, you will either change the rate of Stormlight consumption, or change the strength of your Lashing. Those are two only options, but we don't know which one is correct. 

 

8 hours ago, DoctaDajman said:

The passive flight makes F-iron insane on them. You could store nearly 100% of your weight at all times if you are moving around via lashings. 

Keep in mind that Lashings just change the direction in which you fall. Terminal velocity will play a massive role here and it depends on both the mass and cross-section area. If you drop your mass to almost 0, then your terminal velocity will be very low, so you'll be as fast as a slug, no matter how many Lashings you apply. But using conservation of momentum to your advantage will work, just like in Wax's case.

[Heilven he/him]

12 hours ago, alder24 said:

This is wrong. All Surges use investiture as a fuel. Kaladin's Lashings consume his Stormlight, Shallan's Lightweaving also needs Stormlight and Shallan often binds it to a sphere that will feed it. Soulcasting consumes lots of Stormlight and all other Surges need a Radiant to have Stormlight with them otherwise Surges simply stop functioning. 

The frost appearing is mostly due to condensation and phase transition of investiture. There is only a very trace amount of investiture present in the environment, too little for even a Radiant to detect it and use it. 

  Hide contents

Questioner

Why does Stormlight make things cold?

Brandon Sanderson

It’s not the Stormlight, it’s condensation because something is going directly from a gas into a solid. The coldness is caused by that, it’s not necessarily that the Stormlight is making things cold, but that the Shardblade is condensing.

Boskone 54 (Feb. 17, 2017)

 

Matter is energy and in Cosmere it's also investiture. No matter if you describe gravity as a force or as a curvature of spacetime, you need energy to create this effect. Brandon also confirmed that laws of conservation of energy are working in Cosmere. Lashings were shown time and time again in books to feed on Stormlight, which is energy. Consequences of those things are quite simple - if you apply a Lashing on yourself and then change your mass, you will either change the rate of Stormlight consumption, or change the strength of your Lashing. Those are two only options, but we don't know which one is correct. 

 

Keep in mind that Lashings just change the direction in which you fall. Terminal velocity will play a massive role here and it depends on both the mass and cross-section area. If you drop your mass to almost 0, then your terminal velocity will be very low, so you'll be as fast as a slug, no matter how many Lashings you apply. But using conservation of momentum to your advantage will work, just like in Wax's case.

I don't think your arguments disprove my theory. Yes, all of the surges consume Stormlight. I theorize that the Stormlight is not converted into energy as part of most surges, rather the Stormlight is used to change the cognitive or spiritual aspect of a target. The continuous cost would be from Stormlight leaking. Soulcasting is both my best and worst evidence for this, as it has been shown numerous times that Soulcasting something into a more dense form requires more of the initial substance(and vice versa), implying that the Stormlight does not become the substance. At the same time there are other energy problems involved and whether it is conservation of mass or energy which is involved is somewhat speculative. 

As for the frost, I think this is the only real explanation for most instances of frost besides the surges just really liking to aura farm. In the case of the Shardblade WOB, I'm honestly really confused about what he means by that. When a gas phase transitions to a solid, it releases energy. This could potentially be the opposite for investiture, where solid investiture is actually a higher energy state, which seems to contradict what we know about solid investiture. Regardless, it doesn't explain any of the other times where frost appears during large uses of surges.

Yes, investiture is frequently stated to be "feeding" uses of surges. It was also frequently stated that there were 10 allomantic metals. I am not denying that there is a constant need for Investiture, just that for most (and perhaps all) uses of the surges, Investiture does not provide the source of energy. I could absolutely be wrong, but given the fact that we know that as you advance in the orders your Stormlight stretches further, it seems like decent evidence. It is also very thematically consistent with Roshar's deep ties to the cognitive realm.

On the topic of the actual energy consumption of lashings, I think I need to make my argument more clearly. If lashings are a true force, they would need no energy to create, but would do work via W = Integral (Force vector dot displacement vector d(displacement)). This introduces a mess of potential energies, and ultimately requires something to do the pulling to be in any way internally consistent. Without an equal and opposite force we have some pretty terrible violations of conservation of momentum. If lashings are some sort of large fluctuations in spacetime which only affect specific things, then the situation is likely even more complicated. I can't pretend to know the details of how this would work, but it would probably require upfront energy. In this conceptual framework there is no transfer of momentum and thus no continuous energy requirement.

Ultimately, Sanderson has all of the power to pick and choose any set of explanations and make them work together consistently while still explaining what happens in the text. I'm mostly looking for the minimum viable theory to explain all that is happening. Sanderson can always add on a thousand different pieces to choose whatever explanation is best, and as such it really could be anything. If we get concrete proof that the energy source for the surges is the Stormlight itself, I won't be bothered. I just think that my theory is a more concise explanation in the meantime.

[Treamayne]

27 minutes ago, Heilven said:

As for the frost, I think this is the only real explanation for most instances of frost besides the surges just really liking to aura farm. In the case of the Shardblade WOB, I'm honestly really confused about what he means by that. When a gas phase transitions to a solid, it releases energy.

Loses energy would likely be more accurate - TOW:

Quote

For deposition to occur, thermal energy must be removed from a gas.

In the Cosmere, Investiture based Deposition occus because Thermal Energy is converted to Investiture - no heat is released at all, and the resulting Solid is Cold. If you have read Mistborn, you may have also noticed that the forming Shard first appears as gas (or Mist. . . ) before assuming a Godmetal Solid. Likewise, Energy transfer occurs with Cadmium and Bendalloy bubbles, and that is how they avoid Redshift and Blueshift - as enregy transfers directly to<->from the Spiritual Realm converting investiture for investiture realmatic conversions. 

While the Surge of Transformation does primary change the Spiritual Identity of an object (though that object's Cognitive Lens; much like Forgery) - most Surges act directly on the Physical Realm. When they do not, you get different effects (like a Bondsmith's Spiritual Adhesion - the Surge of Adhesion applied to Spiritual Realm Connection). 

WoB:

Spoiler

BipedSnowman

In theory, could you create weird structures or even alloys [with Forgery]?

Two scenarios: using Forging how you might use Soulcasting, such as turning something into wood, bending and carving it to make a new shape, then breaking the seal so it turns back into the original material without changing shape.

Second: Forging one metal into another, and forming an alloy to reduce operation costs. For example, tungsten has a melting point of about 3.5k C, but it's useful as part of a steel alloy for certain applications. Could you Forge it into, say, zinc, which has a melting point of about 500 C, create the steel, then turn it back into tungsten? Presumably the investiture would adjust the molecular structure so it acts as if it has been alloyed with tungsten originally too, otherwise the same process happening with food could be deadly.

Brandon Sanderson

Yes, this is in theory similar to Soulcasting. The difference is that a Forged object, upon "Forgetting" the rewriting to its spiritual nature is going to try to snap back and match what it "thinks" it should be like--which isn't going to lead to as much stability as Soulcasting, where the actual soul is changed. The object is going to try to get back to the way it "should" be, with varying results.

The reason the Lord Ruler aged hyper-quickly is related to this as well.

General Reddit 2018 (Aug. 27, 2018)

Hope that helps

[Heilven he/him]

17 minutes ago, Treamayne said:

In the Cosmere, Investiture based Deposition occus because Thermal Energy is converted to Investiture - no heat is released at all, and the resulting Solid is Cold. If you have read Mistborn, you may have also noticed that the forming Shard first appears as gas (or Mist. . . ) before assuming a Godmetal Solid. Likewise, Energy transfer occurs with Cadmium and Bendalloy bubbles, and that is how they avoid Redshift and Blueshift - as enregy transfers directly to<->from the Spiritual Realm converting investiture for investiture realmatic conversions. 

While the Surge of Transformation does primary change the Spiritual Identity of an object (though that object's Cognitive Lens; much like Forgery) - most Surges act directly on the Physical Realm. When they do not, you get different effects (like a Bondsmith's Spiritual Adhesion - the Surge of Adhesion applied to Spiritual Realm Connection). 

Is there actual evidence for these claims? My explanation for the frost forming on Shardblades is due to this effect, I just didn't know if this is supported by anything more than what we see in the text. As for the surges, I think that relegating most surges to be only physical is a deep disconnect with the themes of Roshar itself. I don't have my books on me so I can't check, but I believe it has been stated that lashings are connecting something to a far away point, or convincing something that gravity is pointed in a different direction. In WAT I believe it is described that when Szeth uses division, he is causing something to believe it is now many things. Truthwatchers can use illumination and progression together to access Fortune. Lightweavers are able to give life to their illusions, even causing them to react to outside stimuli. And that's not just Shallan being Shallan, making an illusion which can walk realistically up stairs is something which takes considerable mental effort to create, but requires comparatively little to maintain. While I am not certain in my theory that Investiture is not used as an energy source for most of the surges, I am quite certain that the surges are impacting things on a cognitive and spiritual level, where the physical effects are the results of changes in the other realms. In fact(WOB):

Quote

Zmann966

So, in Oathbringer, we see the Surge of Adhesion used in an interesting way, Spiritual Adhesion. Do all the Surges have non-Physical manifestations like that?

Brandon Sanderson

All the Surges do, slightly, in fact, but none of them, I would say, are as Spiritual as that. 

Zmann966

What about like, Shallan in Words of Radiance with her mercenaries? So, like, a Spiritual Transformation? 

Brandon Sanderson

I wouldn't say Transformation, she is seeing a little bit, glimpsing a little bit, does that make sense? 

Oathbringer Chicago signing (Nov. 21, 2017)

 

[DrPhysics he/him]

On 7/17/2025 at 7:14 AM, alder24 said:

But as Treamayne said, Fused passive effect allows them to Lash themselves without consuming investiture, so F-iron wouldn't change a lot for them. It could only increase their maneuverability and help them turn or decelerate faster ... But it would have no effect on their acceleration and investiture consumption rate.

Maneuverability and deceleration are also accelerations and would not be affected by changing mass. You could make an argument where decreasing mass might help you slow down faster by reducing your terminal velocity and air resistance, but there's a trade-off with momentum temporarily speeding you up. It definitely won't help with turning, because drag forces only act in the direction opposite travel.

 

On 8/18/2025 at 12:03 PM, Heilven said:

We know that depictions of g-force or forces due to lashings are due to the underlying mechanics not being fully thought out (to the general relativistic level that is. That's pretty far to think something out).

The depictions we see are wrong with good old Newtonian gravity as well. It's unclear whether that was a mistake by Sanderson or done for audience expectations, but the g-force effects only apply when something resists the pull of gravity.

 

Put a hole in the bottom of a water bottle and drop it. While in free-fall, no water will come out because there is no pressure build up due to the container holding up the water.

[Treamayne]

23 hours ago, DrPhysics said:

It's unclear whether that was a mistake by Sanderson or done for audience expectations

Sanderson has said that it was Audience Expectation. WoB:

Spoiler

shinarit?

There is that scene where Kaladin takes a sharp turn at high speeds and he almost blacks out. That is normal for jet pilots, since they experience high G forces when their airplane tries to accelerate them by their backs and bottoms.

But Lashing doesn't work that way, it generates fake gravity. Accelerating your whole body shouldn't cause you anything, you can't even feel it.

Is this something that is an admitted physics hiccup or I misunderstood this kind of Investiture usage?

Brandon Sanderson

This one is actually in the process of flux, as I do more research on the effects of acceleration (including interviews with fighter pilots, which has been fun.) Basically, I realized I needed to beef up my understanding of all this, and then make some decisions on exactly how this all works, because I've been relying on instinct too much in some of these sequences.

So...that's a RAFO, I'm afraid. More because I'm still tweaking some of the little details of how I want this all to work. (In ways that become increasingly relevant as I look forward toward things like Windrunners in space.)

There are a ton of details to consider, even if I eventually hand-wave some of it with the magic. (For example, the heart pumping blood in a high-g environment. How does that interact, if at all, with stormlight? And the direct oxygenation of the brain implied by not needing to breathe while holding stormlight...)

We have several very large math-ish projects going on behind the scenes.

Phoenixdown

I think it depends on if lashing independently impacts each atom within your body simultaneously, or if it is only a subset.

Brandon Sanderson

There's one important fact you're not considering, but which is vital: reader expectation.

One of the questions I have to ask myself is this: What will the reader expect to happen? How will they expect to feel? Granted, none of us have ever flown like this before--but we generally imagine similar things, similar feelings.

As a writer, one thing I need to balance is when I go against reader expectations and when I don't. Going against the expectations can be interesting, but often takes a large burden of words and explanation to keep reminding them something is not how they'd imagine it to be.

For example, it took a relatively large amount of reader attention (and explanation) to keep reminding people in Mistborn that plants weren't green and the sky wasn't blue. In many ways, making something new (like a chull) is easier on readers than making something familiar into something strange (like the horses in Dragonsteel, which were smaller than Earth horses--and kept causing confusion problems in my alpha readers.)

As annoying as this example can me, this is why Lucas had sound, fire, gravity, etc in space. Starships banking in formation felt real to the viewers, even if it didn't make sense in context. I hope to not go that far, but these questions are something in my mind.

I try to be careful not to remove the sensations of magic, in order to keep the movements of characters grounded. Windrunning has left me having to decide how far I want to go with things like this, in order to preserve the visceral feelings for the reader.

General Reddit 2018 (June 6, 2018)

Of course, part of the Handwavium is likely to be "Kaladin felt these things because his Intent expected him to feel these things" (as a consequence of his initial Lurches when first learning to Lash in the Chasms and experiencing the disorientation of changed gravitational perceptions) which would help transition to people more trained on the powers and what should happen, rather than self-training and possibly not having the full picture. 

Edited August 21, 2025 by Treamayne
SPAG

[Rorzikel]

There is one other wob from Dragonsteel 2023 where Brandon mulls it over and says that he thinks that the Lashing will run out faster if used on a Feruchemist.

Quote

Questioner

In a battle versus a Feruchemist and a Windrunner, if the Feruchemist were lashed directly upward, would increasing his weight cancel that lashing out?

Brandon Sanderson

The way that lashings work are by rewriting your body's interaction with gravity. That's very weird. It's very, very weird. The way that Feruchemy works, it is kind of the same way. I play loose and free with this one (this is the one that drives everybody else mad). It is actually changing, so would it... what would it do?

So, part of me wants to say you would fall upward faster. But that's not how gravity works, so that wouldn't happen. But would it counteract the lashing? I think that the lashing would incorporate it, and nothing would change. That is my best guess, but your lashing, then, probably runs out faster. That's my off-the-cuff answer; I'd have to really look at the mechanics of that. But you can take that for now. I'll have to consult with the arcanists to make sure I'm not going crazy on that.

Dragonsteel 2023 (Nov. 21, 2023)

 

[Kfish]

On 8/18/2025 at 8:47 PM, DoctaDajman said:

The passive flight makes F-iron insane on them. You could store nearly 100% of your weight at all times if you are moving around via lashings. 

Honestly they are already insanely mobile and adept at flying. If you added on the ability to manipulate speed via conservation of momentum on top of that... completely bonkers the results they could achieve. Even if their passive use is limited in the amount of lashings they can use. 

The added weight would not damage any of the environment around them and so they could make themselves magnitudes heavier as they start their lashing only to cut down and boost acceleration even more. 

Now I am curious how quickly lashings can stop someone from falling... if you started at 100,000 lbs to rocket yourself forward by dropping your weight to nothing in the first moments of a lashing how hard would it be to negate all of the inertia when you want to slow down?  I guess you could always tap another 100,000 lbs to come to a near dead stop instantly. 

Lashing affects gravity. Weight is a measure of gravity's pull on you (roughly).  If they stored 100%, ofntheir weight, I think their lashing would be less effective because it would reduce the pull their lashing is having on them. 

[Kfish]

Little equation I just wrote up

 

# Cosmere "gravity math": Lashings (L) × Feruchemical Iron (I)

 

# Definitions

# m = true mass (baseline)

# g = normal gravitational acceleration

# L = Lashing multiplier on g (1 = 1g, 2 = 2g, etc.)

# I = Feruchemical iron multiplier on effective weight/inertia

# W = weight (force due to gravity)

# a = resulting acceleration

 

# Step 1 — Baseline weight

W = m * g

 

# Step 2 — Apply a Lashing (modifies gravitational acceleration)

g' = L * g

W_L = m * g' = m * (L * g)

 

# Step 3 — Apply Feruchemical Iron (scales effective weight/inertia)

W_LI = I * W_L = I * m * (L * g)

 

# Step 4 — Newton’s 2nd Law (equate total force to m * a)

F = m * a

 

# Step 5 — Set gravitational/Invested force equal to m * a

m * a = I * m * (L * g)

 

# Step 6 — Cancel m (m ≠ 0) and solve for a

a = I * L * g

Taken further to introduce drag:

 

# From Iron+Lashing → adding aerodynamic drag (step-by-step)

 

# GIVEN DEFINITIONS

# m = true mass

# g0 = baseline gravity

# L = Lashing multiplier on gravity (1 = 1g, 2 = 2g, etc.)

# I = Feruchemical iron multiplier (I<1 storing; I>1 tapping)

# ρ = air density

# Cd = drag coefficient

# A = reference area

# k = 0.5 * ρ * Cd * A (drag constant)

# v = speed along the acceleration direction

 

# 1) Lashings only (no iron, no drag)

# a = L * g0

 

# 2) Include Feruchemical iron as an external force multiplier

# F_total = I * m * (L * g0)

# Using F = m * a:

# m * a = I * m * (L * g0)

# a = I * L * g0

# (This is our previously derived endpoint.)

 

# 3) Introduce quadratic drag opposing motion

# F_drag = k * v^2 (opposite direction)

 

# 4) Write Newton’s 2nd Law with drag

# m * dv/dt = I * m * (L * g0) - k * v^2

 

# 5) Divide by m to get the acceleration ODE

# dv/dt = I * L * g0 - (k/m) * v^2

 

# 6) Terminal velocity (dv/dt = 0)

# 0 = I * L * g0 - (k/m) * v_t^2

# (k/m) * v_t^2 = I * L * g0

# v_t = sqrt( (I * L * g0 * m) / k )

# = sqrt( (2 * I * L * g0 * m) / (ρ * Cd * A) )

 

# 7) Optional variant if you treat iron as scaling inertia too:

# Let m_eff = I * m, so:

# (I * m) * dv/dt = I * m * (L * g0) - k * v^2

# dv/dt = L * g0 - (k / (I * m)) * v^2

# Terminal velocity (dv/dt = 0):

# v_t = sqrt( (I * L * g0 * m) / k ) # same result as Step 6

 

 Summary

# ODE with drag (standard form):

# dv/dt = I * L * g0 - (k/m) * v^2 # (or L * g0 - k/(I m) * v^2 if inertia scales)

# Terminal velocity:

# v_t = sqrt( (2 * I * L * g0 * m) / (ρ * Cd * A) )

Edited August 29, 2025 by Kfish

[alder24]

23 minutes ago, Kfish said:

Lashing affects gravity. Weight is a measure of gravity's pull on you (roughly).  If they stored 100%, ofntheir weight, I think their lashing would be less effective because it would reduce the pull their lashing is having on them. 

F-iron stores mass, not weight and it can never store 100% of it. Lashings change gravitational acceleration and all things fall at the same rate if you ignore air resistance, no matter their mass. But air resistance can't be ignored so manipulating mass via F-iron will also affect your terminal velocity and speed (due to conservation of momentum). Even if you store most of your mass and apply 100 Lashings on yourself, you will move very slowly because you will hit your terminal velocity almost immediately.

You should avoid double posting, it's against the forum's policy. You can always edit your previous post.

[DoctaDajman]

28 minutes ago, Kfish said:

Lashing affects gravity. Weight is a measure of gravity's pull on you (roughly).  If they stored 100%, ofntheir weight, I think their lashing would be less effective because it would reduce the pull their lashing is having on them. 

If flying is a passive ability that does not cost the heavenly ones anything, and they are moving via fall, then what does it matter if they are falling at a feathers pace or not? Instead of titrating their lashing amount to speed up or slow down they can titrate their weight. 

The point is that they can be storing all of their weight and still be mobile because they move around for free at the speed of a fall. Wind resistance may make them slower the lighter they are, but the fact stands that they can still be mobile. 

That isn't even talking about the fact that they will never become boyant because they will still be wearing metalminds which will always have weight. 

I dont know how much heavenly ones way but the Fused are usually depicted as a good deal larger than humans and they are covered in heavy natural chitin armoring which I imagine makes them far denser and heavier than their human counter parts. If a heavenly ones weighs 400lbs and stored even 90% of their weight they would still have enough mass to move around via lashings. If they aren't in a hurry they could probably store closer to 100%. But even at only 90% storage just 1 hour of storing would leave them 1.3million pounds to play with later. 

And again, because their flight is their passive free mobility, that adds up really really fast. They can manipulate their flight in ways that kaladin or the lord ruler could only dream of.  

Give a heavenly one iron feruchemy and you will make the most maneuverable, and dangerous flier in the entire cosmere bar none. 

Add onto that their own armoring and and a healing source and you have mini nukes flying around. 

They could reach dangerous levels of acceleration and if they swap their massive aluminum spears out for something more dense like tungsten (which they could lash with them to make it nearly weightless in their hands as it would be falling in the same direction as themselves). Then they could reach speeds in a dive bombing run and let that puppy fly unlike anything we have seen.