How busted is compounding?

[alder24]

13 hours ago, Tamriel Wolfsbaine said:

As far as landing it should be EZPZ.  Double your weight and your speed cuts in half.  It doesn't take a bunch of weight to slow you down to next to nothing and at that point your body is magically enhanced to absorb the shock of falling at that weight.  

The problem with landing is that you still have the same momentum. Doubling your weight gives you greater mass, greater force on impact,  and greater potential energy E=mgh. Without changing your mass, you have greater speed, and this means greater kinetic energy E=(mv^2)/2. Energy is conserved. and that means landing would be hard no matter what you do. So you just break your bones. How about just  throwing a coin before landing and pushing it, like all coinshooters do?

[rabidhexley]

2 hours ago, alder24 said:

The problem with landing is that you still have the same momentum. Doubling your weight gives you greater mass, greater force on impact,  and greater potential energy E=mgh. Without changing your mass, you have greater speed, and this means greater kinetic energy E=(mv^2)/2. Energy is conserved. and that means landing would be hard no matter what you do. So you just break your bones. How about just  throwing a coin before landing and pushing it, like all coinshooters do?

The hypothetical is actually about a Skimmer (Iron Ferring only), and how they could possibly use weight manipulation in order to super jump. No steel push to save them on the way down unfortunately.

[alder24]

24 minutes ago, rabidhexley said:

The hypothetical is actually about a Skimmer (Iron Ferring only), and how they could possibly use weight manipulation in order to super jump. No steel push to save them on the way down unfortunately.

Yes, but I was responding to his idea about Wax:

17 hours ago, Tamriel Wolfsbaine said:

As for Wax... That is something I have been wishing brandon did more to show.  It happened in his conversation in BoM where he mentioned storing a going faster vs tapping and slowing down.  Conservation of momentum does say that if he doubled his size before a push off of the ground and then stored as much as he possibly could once airborn he would take off a bit like a rocket.  He should have the ability to double / triple / even more his speed based on how heavy he was when he pushes.  As for slowing down so many people get confused by the idea of becoming light as a feather but all he really needs to do is make himself two / three / or more times as heavy as he is falling to sap all of that speed and land safely with his feruchemically enhanced bone structure build to withstand those forces that come with being so heavy.  

I WoA Sazed jumps from high places while having his weight reduced to that of a feather, and can land safely due to air resistance. 

[Tamriel Wolfsbaine]

33 minutes ago, alder24 said:

Yes, but I was responding to his idea about Wax:

I WoA Sazed jumps from high places while having his weight reduced to that of a feather, and can land safely due to air resistance. 

 

1 hour ago, rabidhexley said:

The hypothetical is actually about a Skimmer (Iron Ferring only), and how they could possibly use weight manipulation in order to super jump. No steel push to save them on the way down unfortunately.

 

3 hours ago, alder24 said:

The problem with landing is that you still have the same momentum. Doubling your weight gives you greater mass, greater force on impact,  and greater potential energy E=mgh. Without changing your mass, you have greater speed, and this means greater kinetic energy E=(mv^2)/2. Energy is conserved. and that means landing would be hard no matter what you do. So you just break your bones. How about just  throwing a coin before landing and pushing it, like all coinshooters do?

The reason I think it works in without the steel pushing is that you are slowing down at a high rate... sure the momentum is conserved but you also have magically reinforced body that is built to not be decimated by itself.   If you jump at 200lbs and right as you are landing tap to being 2000 lbs you might keep all that momentum but it won't be enough to overcome the newly gained strength from being 10x that weight.  As well as slowing to a screeching halt before hitting the ground.  

You could slow yourself gradually or keep slowing yourself for the last yards before hitting the ground.  Double your weight to slow yourself by half, and then as gravity speeds you up again you can simply continue adding weight until you are so heavy and moving slow enough that the touchdown on the ground aided by your magically increased body structure keeps you safe.   

A Skimmer super jumper shouldn't need steel to survive impact.  

Sazed did featherfall and that is a viable option.  

It is not the only option.  You can very easily jump off a building at 10x your weight.  Store it all quickly and potentially speed up (unless storing is like dropping the ball in other examples) and then as you approach the ground start tapping again and land very slow and heavy and safely thanks to feruchemy protecting your body.  

[alder24]

3 minutes ago, Tamriel Wolfsbaine said:

The reason I think it works in without the steel pushing is that you are slowing down at a high rate... sure the momentum is conserved but you also have magically reinforced body that is built to not be decimated by itself. 

Your body is just strong enough to sustain new weight, but not to sustain more damage. If Wax pushes himself from a coin on top of the building and then just slamms into the ground, he would be dead. If he makes himself much heavier, he would still be dead, as the same force is acting on his body (F=ma), and it cannot survive that injury. It's not pewter. You increase mass, speed is decreased, deceleration on impact is also decreased, force is the same. Iron only makes you able to carry your new weight, its not giving you pewter-like strength.

9 minutes ago, Tamriel Wolfsbaine said:

If you jump at 200lbs and right as you are landing tap to being 2000 lbs you might keep all that momentum but it won't be enough to overcome the newly gained strength from being 10x that weight.  As well as slowing to a screeching halt before hitting the ground.  

You don't gain new strength. 3 law of motion also works here, for every action there is an equal and opposite reaction. You still have the same momentum, the same energy, the same force acting on your very same body. Everything is still the same. And when your body at regular weight can't survive that landing, gaining more weight won't change this.

13 minutes ago, Tamriel Wolfsbaine said:

You could slow yourself gradually or keep slowing yourself for the last yards before hitting the ground.  Double your weight to slow yourself by half, and then as gravity speeds you up again you can simply continue adding weight until you are so heavy and moving slow enough that the touchdown on the ground aided by your magically increased body structure keeps you safe.   

It's not the speed that matters. F=ma. That's what matters. With lower speed you just have lower deceleration "a", but you are increasing "m", force would still be the same. You are switching kinetic energy E=(mv^2)/2 for gravitational one E=mgh. Energy is conserved. You don't have pewter.

26 minutes ago, Tamriel Wolfsbaine said:

Sazed did featherfall and that is a viable option.  

It is not the only option.  You can very easily jump off a building at 10x your weight.  Store it all quickly and potentially speed up (unless storing is like dropping the ball in other examples) and then as you approach the ground start tapping again and land very slow and heavy and safely thanks to feruchemy protecting your body.  

There is a way to survive a jump from a building. First you store your weight, then you jump, and freefall. Decreasing your weight has no effect on air drag, but it does decrease your terminal velocity, it can go way down to speeds that don't cause injury to human body. That what Sazed did. Increasing your mass is a wrong way to go, as you are increasing your terminal velocity.

But if you jump with high mass or push yourself from a coin to add more speed, you now gain more energy. You store weight, gain more speed and can exceed new terminal velocity. Air drag will try to slow you down, but if the height of the fall is too short, you will still have too much energy, and won't survive the fall, as your speed did not decrease fast enough. Even if you start tapping your weight just before impact, you still have too much energy, as you transferring kinetic one to gravitational.

Tapping weight is the very opposite thing you want to do to survive a fall. You still get the same energy that is deadly in contact with the ground. You need to get rid of that energy, and air drag is the way - to do it, you need to decrease your weight to reduce your terminal velocity, and air will steal more energy from you, and that's how you would survive that fall - if you have enough time to slow down.

[Frustration]

56 minutes ago, Tamriel Wolfsbaine said:

If you jump at 200lbs and right as you are landing tap to being 2000 lbs you might keep all that momentum but it won't be enough to overcome the newly gained strength from being 10x that weight.

Actually there is a conservation of momentum, so if you tapped a whole bunch you would slow down.

[Tamriel Wolfsbaine]

3 hours ago, alder24 said:

Your body is just strong enough to sustain new weight, but not to sustain more damage. If Wax pushes himself from a coin on top of the building and then just slamms into the ground, he would be dead. If he makes himself much heavier, he would still be dead, as the same force is acting on his body (F=ma), and it cannot survive that injury. It's not pewter. You increase mass, speed is decreased, deceleration on impact is also decreased, force is the same. Iron only makes you able to carry your new weight, its not giving you pewter-like strength.

You don't gain new strength. 3 law of motion also works here, for every action there is an equal and opposite reaction. You still have the same momentum, the same energy, the same force acting on your very same body. Everything is still the same. And when your body at regular weight can't survive that landing, gaining more weight won't change this.

It's not the speed that matters. F=ma. That's what matters. With lower speed you just have lower deceleration "a", but you are increasing "m", force would still be the same. You are switching kinetic energy E=(mv^2)/2 for gravitational one E=mgh. Energy is conserved. You don't have pewter.

There is a way to survive a jump from a building. First you store your weight, then you jump, and freefall. Decreasing your weight has no effect on air drag, but it does decrease your terminal velocity, it can go way down to speeds that don't cause injury to human body. That what Sazed did. Increasing your mass is a wrong way to go, as you are increasing your terminal velocity.

But if you jump with high mass or push yourself from a coin to add more speed, you now gain more energy. You store weight, gain more speed and can exceed new terminal velocity. Air drag will try to slow you down, but if the height of the fall is too short, you will still have too much energy, and won't survive the fall, as your speed did not decrease fast enough. Even if you start tapping your weight just before impact, you still have too much energy, as you transferring kinetic one to gravitational.

Tapping weight is the very opposite thing you want to do to survive a fall. You still get the same energy that is deadly in contact with the ground. You need to get rid of that energy, and air drag is the way - to do it, you need to decrease your weight to reduce your terminal velocity, and air will steal more energy from you, and that's how you would survive that fall - if you have enough time to slow down.

So if you are falling at 120mph (roughly terminal velocity) and you weigh 200lbs you die... That is 176ft/sec that is quick.  

That 200 lbs turns to 16,000 lbs and you are suddenly only traveling at 2.2 ft/sec or 1.5mph.  

2 hours ago, Frustration said:

Actually there is a conservation of momentum, so if you tapped a whole bunch you would slow down.

My thought is that momentum being conserved says that a normal sized man falling suddenly tapping all of his weight can slow down (near instantaneously mind you) to a fall of just 1.5mph and inches away from the ground.   The changes that happen to allow your body to survive at that weight would be plenty to absorb what is essentially the same force as a normal foot fall for a person walking at 1.5mph at that same size.  Easily survivable with the feruchemical padding.  

Other things to consider about why you don't have to start feather light... 

The inverse to the conservation of momentum is true.  If a 16000lb man were jumping at a speed of 1.5mph and then he stopped tapping he should suddenly be traveling 120mph.   We don't see this.   I believe others in the thread have pointed out the idea that it only conserves momentum when being added to.  Evidence by Wax not yet sending himself into orbit or becoming a pancake after his metalminds ran out when crushing a building...

If momentum is only conserved when drawing weight from a metalmind and it instead acts like letting go of the falling ball from other examples when storing then we actually can argue that skimmers can free fall more safely than just relying on the magic of being 16000 lbs to stop their fall.  

You could step off of a building and fall as fast as you wish only to tap and slow yourself to a desired speed and then start storing again immediately after to take your new 1.5mph decent into that nice feather fall world.  

You don't have to start as light as a feather when skimming to survive a free fall.  

And you could store all of the weight required to play this game over and over by storing during the elevator ride up to the top of whatever building you enjoy jumping off of.  

 

[alder24]

1 hour ago, Tamriel Wolfsbaine said:

So if you are falling at 120mph (roughly terminal velocity) and you weigh 200lbs you die... That is 176ft/sec that is quick.  

That 200 lbs turns to 16,000 lbs and you are suddenly only traveling at 2.2 ft/sec or 1.5mph.  

It's not just the speed that matters. It's the energy! You still have that energy when impacting! Force is there. Your impact would be still very forceful. It's still deadly. 

1 hour ago, Tamriel Wolfsbaine said:

My thought is that momentum being conserved says that a normal sized man falling suddenly tapping all of his weight can slow down (near instantaneously mind you) to a fall of just 1.5mph and inches away from the ground.   The changes that happen to allow your body to survive at that weight would be plenty to absorb what is essentially the same force as a normal foot fall for a person walking at 1.5mph at that same size.  Easily survivable with the feruchemical padding.  

Conservation of energy must also be fulfilled. Where did that energy that he already accumulated by falling went? Disappeared? It can't. Energy can't be destroyed. Where is that energy, which determines if impact with ground is deadly or survivable? This is what is important. It can't just go away. It's still with him.

 

Edit

Also tricky thing, with near instantaneous changes of speed, G forces should be involved. But this is weird physics, as falling objects in our world can't just change mass to change its speed like a Skimmer can. Deceleration is happening here - kind of. So I don't know if G forces are applied here, but if they are, G forces alone would kill him, when changing mass that drastically.

Edited January 11, 2023 by alder24

[Tamriel Wolfsbaine]

16 hours ago, alder24 said:

It's not just the speed that matters. It's the energy! You still have that energy when impacting! Force is there. Your impact would be still very forceful. It's still deadly. 

Conservation of energy must also be fulfilled. Where did that energy that he already accumulated by falling went? Disappeared? It can't. Energy can't be destroyed. Where is that energy, which determines if impact with ground is deadly or survivable? This is what is important. It can't just go away. It's still with him.

 

Edit

Also tricky thing, with near instantaneous changes of speed, G forces should be involved. But this is weird physics, as falling objects in our world can't just change mass to change its speed like a Skimmer can. Deceleration is happening here - kind of. So I don't know if G forces are applied here, but if they are, G forces alone would kill him, when changing mass that drastically.

You are right that the energy is still there.  You are wrong that it would kill him.  

It would kill a 200lb man.  It might kill a 2000 lb man. But if you tap so much weight that that energy is no longer a factor to your body then it is fine.   

The powder charge from my 45-70 generates so much energy that the 400 grain projectile it shoots will destroy any dangerous game you put in front of it.  That same powder charge wouldn't be able to clear a 6lb cannonball out of that cannon.  With zero resistance on it you would be lucky to see it roll at all.  

We see that Wax wasn't killed by the strain that is making himself so heavy that his push is crushing buildings.  We saw Sazed capable of not dying when he moved and pressed his weight against the door.  

We don't see Bleeder and Marasi blackout or run into anything she doesn't want because their minds are sped up enough to process moving past the speed of sound.  

Feruchemy changes your body to withstand the magic that is effecting it so it doesn't kill you.  

A multi million lb Wax was not crushed by the weight it took to collapse a building.   A multimillion lb Wax did not die instantly when he landed after breaking through the floor in his house to escape an explosion.  

Ferucheny changes your body to withstand the magic that is effecting it so it doesn't kill you.  

If a 16000 lb Skimmer is able to withstand the force and energy generated by walking a mere 1.5miles per hour then... 

Going from 200 lbs falling at 120mph (terminal velocity ish) to 16000lbs a foot away from the ground would slow him and turn that energy into the same energy as him moving a whopping 1.5miles per hour.  

Speed absolutely matters when discussing the potential damage that body would take even if the energy never goes anywhere.  

The same energy used to kill a 2000lb bison with a 400grain bullet being used to push a 6lb bullet wouldn't move it enough to make that bison take a step.  Same energy. Just that the speed would be so low that it can't do anything.  

And if, skimming works in such a way that storing weight actually just drops the weight and doesn't change your speed (again all the evidence points to this given we don't see wax taking off into orbit or falling past the speed of sound or faster after his metalminds wear off) then we can say the Skimmer is safer than that even.  

What Wax does comment on is that his gaining weight changes his flying.... because he is slowing down when he taps a bunch.  He never speeds up when he stores though.  

So you could jump off a building at millions of lbs. store all of that weight and not speed up, hit terminal velocity and tap to millions of lbs again to slow down to next to nothing, store it all again a second later and not speed up and then featherfall to the ground.  

It is stated that conservation of momentum is a thing with skimming but we don't actually see it work both ways.  In the books it is only demonstrated in this manner.  

Something happens in the spiritual realm to shed the energy and momentum when you store weight but conserve it when you tap.  

And again.  Because its feruchemy we see the skimming on screen protect the user from all of that weight and energy.  If they can take a step at 16000 lbs without dying then they can safely land after tapping up to 16000lbs in the last few feet of their decent at terminal velocity.  

[alder24]

4 hours ago, Tamriel Wolfsbaine said:

It would kill a 200lb man.  It might kill a 2000 lb man. But if you tap so much weight that that energy is no longer a factor to your body then it is fine.   

The powder charge from my 45-70 generates so much energy that the 400 grain projectile it shoots will destroy any dangerous game you put in front of it.  That same powder charge wouldn't be able to clear a 6lb cannonball out of that cannon.  With zero resistance on it you would be lucky to see it roll at all.  

Because of the density. But Skimmer DOESN'T change his density, bullets affect him as normal. The only thing that changes is his weight and ability to uphold that weight. Not strength, not endurance, not density.

Spoiler

Brandon Sanderson

Chapter Six

The fight in the ballroom

From the early days of the Mistborn books, I'd been planning how an Allomantic gunfight would go down. I felt it the next evolution in what has been stylistically a big part of these books.

There is a fine line to walk in a lot of these sequences. I've made something of a name for myself in the fantasy world by attempting to mix some scientific reasoning with my magic systems. At the same time, Allomancy was designed precisely with action sequences in mind. I wanted them to be powerful and cinematic—and a cinematic fight sequence is often at odds with realism. (Watch two people who really know what they're doing fight with swords sometime, then watch any fight sequence in a film. Most of the time, the film sequences stray far from what would really happen.)

So, as I said, I walk a line. Sometimes, there are things I just can't do because they violate what I've set up as the rules of the world. Other times, I design the setting and nature of the fight specifically to allow for certain types of cinematic sequences. One thing I like a lot about Wax’s abilities is the power he has to manipulate his weight. There's some realism to what he does—for example, increasing his weight doesn't make him fall more quickly, but it allows him to do some powerful things while falling. Destroying the chandeliers is an example.

At the same time, I acknowledge that the weight manipulation aspect of Feruchemy is one of its more baffling powers, scientifically. Is he changing his mass? If so, he should become more dense, which I don't actually make the case when it plays out in fights. (Otherwise, increasing his weight enough would make him impervious to bullets.) So, if it's not mass manipulation, is it gravity manipulation, like Szeth and Kaladin do? Well, again, not really—as when his weight increases, his strength and ability to uphold that weight increase as well. Beyond that, Wax can't make himself so light that he has no weight at all.

So . . . well, at this point, the ability to explain it scientifically breaks down. I do like what it does, but I have to set its boundaries and stick to them—and accept that some of what's going on is irrational. (And don't get me started on what should really be happening scientifically when Wayne speeds up time.)

Footnote: Brandon has stated that iron Feruchemy works by manipulating the Higgs field.
The Alloy of Law Annotations (March 14, 2014)

 

4 hours ago, Tamriel Wolfsbaine said:

If a 16000 lb Skimmer is able to withstand the force and energy generated by walking a mere 1.5miles per hour then... 

Going from 200 lbs falling at 120mph (terminal velocity ish) to 16000lbs a foot away from the ground would slow him and turn that energy into the same energy as him moving a whopping 1.5miles per hour.  

Stop telling me about speed, and start about ENERGY! That is what kills people, not a speed. People falling transfers potential energy into kinetic energy. Skimmer falling from a sky has a lot of energy in him - where does that energy go? It can't disappear - 1st Law of Thermodynamics - Energy cannot be created or destroyed. The energy that Skimmer accumulated during fall can't just simply disappear, when he changes his mass. What is happening to conservation of energy? It MUST be conserved. 

4 hours ago, Tamriel Wolfsbaine said:

Speed absolutely matters when discussing the potential damage that body would take even if the energy never goes anywhere.  

That's right. If energy doesn't go anywhere, the falling Skimmer has still the same energy, as falling human. Even with mass maniupulation, the energy is still the same. If that energy is able to kill a human, it also will kill a Skimmer, even if he will be having mass of 1mil kg. It's not a speed that kills, it's energy. And Skimmer doesn't have pewter. He's still as vulnerable as normal human, he can just uphold his body with more mass.

4 hours ago, Tamriel Wolfsbaine said:

The same energy used to kill a 2000lb bison with a 400grain bullet being used to push a 6lb bullet wouldn't move it enough to make that bison take a step.  Same energy. Just that the speed would be so low that it can't do anything.  

We're talking about falling people, this has nothing to do with it...

btw, did you know that when you drop an elephant from a skyscraper, it explodes in contact with the ground, while a squirrel just walks away like nothing has happened?

4 hours ago, Tamriel Wolfsbaine said:

He never speeds up when he stores though.  

He does, he talks about it with Kriss - The Bands of Mourning chapter 12. He tells her that when he decreases his weight to half, his speed doubles.

4 hours ago, Tamriel Wolfsbaine said:

If they can take a step at 16000 lbs without dying then they can safely land after tapping up to 16000lbs in the last few feet of their decent at terminal velocity.  

Not when they have been previously falling with terminal velocity, and accumulated a crap ton of energy due to that fall - it can't disappear, it must be still with him. And if it's with him, then he will be dead when he impacts the ground, even if it's with lower speed.

 

How about we do some math to prove my point? Can you?

Spoiler

M1=80kg, M2=8000kg, H=500m, g=9.81m/s2

Free falling normal 80kg from 500m

Ep=M1gH=80*9.81*500=392 400J - this is the potential energy that will be transferred during the fall into kinetic energy. Some of it will get lost to air resistance 

But it's physics so lets ignore air resistance and therefore no terminal velocity. I don't know how to calculate with drag, and google is not helpful. All of that Ep is fully transferred into Ek when the fall ends.

Ek=Ep=mv^2/2 - from this we can calculate speed on impact.

v=Sqrt(2Ep/m)=99m/s - this is the speed during impact (almost 2x terminal velocity) (yes, I know there is an equasion for speed in free fall, without m/m)

 

We've got the energy when he impacts the ground. Now let's release a Skimmer from 500m with 80kg, he will tap metalminds to 8000kg just 1m above ground.

 

Starting potential energy is still the same, but 1m above the ground he still has this energy:

Ep1=m1g*1m=784,8 - this is the potential energy remaining 1m above the ground, rest of Ep=392 400J is converted into kinetic one 

Ek=Ep-Ep1=391 615,2J - this is the kinetic energy he has 1m above the ground. From this we can calculate speed he reached before tapping his metalminds

v=Sqrt(2Ek/m)=98,9~99m/s - almost the same speed, that was expected. 

 

Now he taps metalminds, increasing his weight to 8000kg. From conservation of momentum we calculate his new speed.

m1v1=m2v2  v2=m1v1/m2=0,99~1m/s - this is his new speed. 

Now let's calculate his new potential energy on 1m high fall 

Ep2=m2*g=78 480 - this is new potential energy.

But wait a minute, this is 100x bigger than with his 80km mass (784,8J). New energy was added to the system. And here we start to break physics. This energy will all be transferred into kinetic one, and thus we can calculate speed on impact:

v=Sqrt(2Ep2/m2)+1m/s=5,4m/s - this is his new speed when impacting the ground. Yes, he gained 5x speed in 1 meter (3 feet) fall.

But wait a minute! Didn't you see a problem? We start to consider this as a free fall from 1m with 8000kg, ignoring all 499m of fall with 80kg previously. But till this point he already got 391 615,2J of kinetic energy in him. Where did this go? Where does it disappear? If he still has it as kinetic energy, then he can't change its speed (with normal physics). But energy can't be destroyed, only change forms. If some of this energy was transferred back into potential energy when mass was changed:

391 615,2-(78 480-784,8)=313 920J

He still should have 313 920J of kinetic energy! Where did it go? It still has to be in the system, it can't disappear. Let's consider two only available options:

1. It's still there in the falling person, and can be added to new energy from new mass - Ep2 
   
   Total energy then is 313 920+78 480=392 400J - this would be total energy on impact with the speed of 5,4m/s. It's the same energy of impact of normal free fall without mass change. No extra energy was added to the system, no energy was destroyed - 1st Law of Thermodynamics is fulfield. This means energy is conserved. Physics is only a little broken, as the impact speed does not correspond to its kinetic energy, but it's a must to conserve energy, which takes priority. With this we were able to conserve both energy and momentum.
    
2. The energy disappears.
   
   In this case the energy on impact is the energy of impact from a 1m fall of 8000kg person - 78 480J with 5,4m/s - which would be survivable, as a normal person can survive a fall from 1m. But this breaks physics completely, as it breaks the Law of conservation of energy. 313 920J literally disappeared. It's gone. Where? It doesn't make sense. Skimmer took energy in form of investiture, from his metalminds, so it should mean that his total energy, if wouldn't remain the same, would increase - yet it somehow decreased almost 5x. This scenerio, which is survivable, fully breaks law of conservation of energy and 1st Law of Thermodynamics. There is no explanation where this energy from falling 500m goes. It can't just disappear.

Because these are the only two options, I can't accept that energy just disappears. If momentum is conserved in Cosmere, then energy also must be. It can't disappear. We know from WoBs that laws of physics still works the same as in our Universe. Logically, we can't consider a 500 meters fall a 1 meter fall just because Skimmer changes his weight. It can't make all his previous fall nonexistent. It's not like making a step, he was falling for 500 meters and then what? Changed his weight and started falling again like he wasn't just falling? It doesn't make sense. We need to consider his fall in its entirety, not just the ending. We need to look at all of the energy that he had from the beginning, not just the energy that he would have with 1m/s speed, 1m above the ground.

 

That's it. This is the math. Feel free to check it out.

Edited January 12, 2023 by alder24

[Tamriel Wolfsbaine]

17 minutes ago, alder24 said:

Because of the density. But Skimmer DON'T change his density, bullets affect him as normal. The only thing that changes is his weight and ability to uphold that weight. Not strength, not endurance, not density.

  Hide contents

Brandon Sanderson

Chapter Six

The fight in the ballroom

From the early days of the Mistborn books, I'd been planning how an Allomantic gunfight would go down. I felt it the next evolution in what has been stylistically a big part of these books.

There is a fine line to walk in a lot of these sequences. I've made something of a name for myself in the fantasy world by attempting to mix some scientific reasoning with my magic systems. At the same time, Allomancy was designed precisely with action sequences in mind. I wanted them to be powerful and cinematic—and a cinematic fight sequence is often at odds with realism. (Watch two people who really know what they're doing fight with swords sometime, then watch any fight sequence in a film. Most of the time, the film sequences stray far from what would really happen.)

So, as I said, I walk a line. Sometimes, there are things I just can't do because they violate what I've set up as the rules of the world. Other times, I design the setting and nature of the fight specifically to allow for certain types of cinematic sequences. One thing I like a lot about Wax’s abilities is the power he has to manipulate his weight. There's some realism to what he does—for example, increasing his weight doesn't make him fall more quickly, but it allows him to do some powerful things while falling. Destroying the chandeliers is an example.

At the same time, I acknowledge that the weight manipulation aspect of Feruchemy is one of its more baffling powers, scientifically. Is he changing his mass? If so, he should become more dense, which I don't actually make the case when it plays out in fights. (Otherwise, increasing his weight enough would make him impervious to bullets.) So, if it's not mass manipulation, is it gravity manipulation, like Szeth and Kaladin do? Well, again, not really—as when his weight increases, his strength and ability to uphold that weight increase as well. Beyond that, Wax can't make himself so light that he has no weight at all.

So . . . well, at this point, the ability to explain it scientifically breaks down. I do like what it does, but I have to set its boundaries and stick to them—and accept that some of what's going on is irrational. (And don't get me started on what should really be happening scientifically when Wayne speeds up time.)

Footnote: Brandon has stated that iron Feruchemy works by manipulating the Higgs field.
The Alloy of Law Annotations (March 14, 2014)

 

Stop telling me about speed, and start about ENERGY! That is what kills people, not a speed. People falling transfers potential energy into kinetic energy. Skimmer falling from a sky has a lot of energy in him - where does that energy go? It can't disappear - 1st Law of Thermodynamics - Energy cannot be created or destroyed. The energy that Skimmer accumulated during fall can't just simply disappear, when he changes his mass. What is happening to conservation of energy? It MUST be conserved. 

That's right. If energy doesn't go anywhere, the falling Skimmer has still the same energy, as falling human. Even with mass maniupulation, the energy is still the same. If that energy is able to kill a human, it also will kill a Skimmer, even if he will be having mass of 1mil kg. It's not a speed that kills, it's energy. And Skimmer doesn't have pewter. He's still as vulnerable as normal human, he can just uphold his body with more mass.

We're talking about falling people, this has nothing to do with it...

btw, did you know that when you drop an elephant from a skyscraper, it explodes in contact with the ground, while a squirrel just walks away like nothing has happened?

He does, he talks about it with Kriss - The Bands of Mourning chapter 12. He tells her that when he decreases his weight to half, his speed doubles.

Not when they were previously falling with terminal velocity, and accumulated a crap ton of energy due to that fall - it can't disappear, it must be still with him. And if it's with him, then he will be dead when he impacts the ground, even if it's with lower speed.

 

How about we do some math to prove my point? Can you?

  Reveal hidden contents

M1=80kg, M2=8000kg, H=500m, g=9.81m/s2

Free falling normal 80kg from 500m

Ep=M1gH=80*9.81*500=392 400J - this is the potential energy that will be transferred during the fall into kinetic energy. Some of it will get lost to air resistance 

But it's physics so lets ignore air resistance and therefore no terminal velocity. I don't know how to calculate with drag, and google is not helpful. All of that Ep is fully transferred into Ek when the fall ends.

Ek=Ep=mv^2/2 - from this we can calculate speed on impact.

v=Sqrt(2Ep/m)=99m/s - this is the speed during impact (almost 2x terminal velocity) (yes, I know there is an equasion for speed in free fall, without m/m)

 

We've got the energy when he impacts the ground. Now let's release a Skimmer from 500m with 80kg, he will tap metalminds to 8000kg just 1m above ground.

 

Starting potential energy is still the same, but 1m above the ground he still has this energy:

Ep1=m1g*1m=784,8 - this is the potential energy remaining 1m above the ground, rest of Ep=392 400J is converted into kinetic one 

Ek=Ep-Ep1=391 615,2J - this is the kinetic energy he has 1m above the ground. From this we can calculate speed he reached before tapping his metalminds

v=Sqrt(2Ek/m)=98,9~99m/s - almost the same speed, that was expected. 

 

Now he taps metalminds, increasing his weight to 8000kg. From conservation of momentum we calculate his new speed.

m1v1=m2v2  v2=m1v1/m2=0,99~1m/s - this is his new speed. 

Now let's calculate his new potential energy on 1m high fall 

Ep2=m2*g=78 480 - this is new potential energy.

But wait a minute, this is 100x bigger than with his 80km mass. New energy was added to the system. And here we start to break physics. This energy will all be

transferred into kinetic one, and thus we can calculate speed on impact:

v=Sqrt(2Ep2/m2)+1m/s=5,4m/s - this is his new speed when impacting the ground. Yes, he gained 5x speed in 1 meter (3 feet) fall.

But wait a minute! Didn't you see a problem? We start to consider this as a free fall from 1m with 8000kg, ignoring all 499m of fall with 80kg previously. But till this point he already got 391 615,2J of kinetic energy in him. Where did this go? Where does it disappear? If he still has it as kinetic energy, then he can't change its speed (with normal physics). But energy can't be destroyed, only change forms. If some of this energy was transferred back into potential energy when mass was changed:

391 615,2-(78 480-784,8)=313 920J

We still should have 313 920J of kinetic energy! Where did it go? It still has to be in the system, it can't disappear. Let's consider two only available options:

1. It's still there in the falling person, and can be added to new energy from new mass - Ep2 
   
   Total energy then is 313 920+78 480=392 400J - this would be total energy on impact with the speed of 5,4m/s. It's the same energy of impact of normal free fall without mass change. No extra energy was added to the system, no energy was destroyed - 1st Law of Thermodynamics is fulfield. This means energy is conserved. Physics is only a little broken, as the impact speed does not correspond to its kinetic energy, but it's a must to conserve energy, which takes priority. With this we were able to conserve both energy and momentum.
    
2. The energy disappears.
   
   In this case the energy on impact is the energy of impact from a 1m fall of 8000kg person - 78 480J with 5,4m/s - which would be survivable, as a normal person can survive a fall from 1m. But this breaks physics completely, as it breaks the Law of conservation of energy. 313 920J literally disappeared. It's gone. Where? It doesn't make sense. Skimmer took energy in form of investiture, from his metalminds, so it should mean that his total energy, if wouldn't remain the same, would increase - yet it somehow decreased almost 5x. This scenerio, which is survivable, fully breaks law of conservation of energy and 1st Law of Thermodynamics. There is no explanation where this energy from falling 500m goes. It can't just disappear.

Because those are two options, I can't accept that energy just disappears. If momentum is conserved in Cosmere, then energy also must be. It can't disappear. We know from WoBs that laws of physics still works the same as in our Universe. Logically, we can't consider a 500 meters fall a 1 meter fall just because Skimmer changes his weight. It can't make all his previous fall nonexistent. It's not like making a step, he was falling for 500 meters and then what? Changed his weight and started falling again like he wasn't just falling? It doesn't make sense. We need to consider his fall in its entirety, not just the ending. We need to look at all of the energy that he had from the beginning, not just the energy that he would have with 1m/s speed, 1m above the ground.

 

That's it. This is the math. Feel free to check it out.

You aren't taking all examples from the books into consideration.   

If Wax or Vin or any other mistborn falls from 500 meters and uses steel to suddenly push a coin and not hit the ground how is that any different than hitting the ground?  If a Lurcher is about to hit the ground and suddenly pulls on an anchor from above what happens to that energy?  

The magic fixes it.  

I have tried hard to math out iron feruchemy but it has never worked without accepting that magic fixes it.  

When Wax weighs enough to break through the ceiling how much energy was there?   If he speeds up when storing part way through a jump why then didn't he suddenly eccelerate to a ridiculous speed when he fell through the ceiling and ran all of his metalminds dry?  

When he crushes the building why didn't he rocket off right after that weight fell off and he was still pushing?

If I shoot my shotgun and it is braced against my shoulder it does nothing to me.  If I am not holding it tightly against my shoulder it bruises it.  How is this possible if damage dealt is such a simple energy ratio?   Because your ability to absorb the impact changes.   

If Wax's timing is perfect enough in all examples to not die then why could another Skimmer not be able to pull off the same feats?  

If I tap weight so much that I completely stop my decent via conservation of momentum then how is it that that energy can do anything?   Is the idea that as soon as I touch anything I will be the exploded elephant on the pavement?  (I believe the books and their examples show it is momentum that is conserved not necessarily all of the energy).   

If Wax is 80kg and spends all day storing 25% of that he is walking around at 60kg all day long.  Over the course of 24 hours he stores 1,728,000 kg.  

There is a breakpoint with the math that takes that movement from the fall from something that is deadly to something that is survivable.  How many jumps you can make and survive is up to the math but the examples in text show that the magic makes up the rest for everything else.  

You aren't just increasing weight 10 or 20 times.  You can increase weight 21,600 times every day you spend your day storing at 75%.  

Iron feruchemy breaks the rules pretty hard and the answer is magic.  The math will never work perfectly but given the examples in the book I think the safest route to go down is that the Skimmer would live or die depending solely on what Brandon wants to happen for the story.

The magic helps to absorb the energy from every foot fall or the anatomical structures are strengthened to fix it.  

I have read some responses that state iron allows your weight to be felt by everything in the world but you act like your weight is its normal bit.  That would explain a lot but it would make skimmers so dangerous and have no need for weapons.  A punch at 1 million lbs while your body treats it like a normal boxing match would be devastating.  

Wax likes to be 75%of his normal weight because he feels like he can move around easier and he feels lighter on his feet.  Sazed has to drop his fists on his enemies because he can't exactly throw hands.  These are great examples of your body not treating itself as normal and outline some limitations.  But the opposites happen when we see Wax become so heavy to break through his floor without snapping every bone in his body.  We don't see him jellyfy when he becomes large enough to destroy a building.  

Interestingly we don't see Wax being more prone to injury at lighter weights either.  He says he doubles speed when he gets twice as light but outside of that conversation specifically we don't see it.  In theory he should be able to use a single push off of the ground at a high weight and be able to send himself into orbit.  So long as the planet is larger than he is he is the one to move in a steel push.  Shoving a building down and it suddenly buckles then he is now millions of lbs potentially and he is moving.  Certainly there is more energy in half a second of falling or pushing up at millions of lbs than what we see.  He runs out of weight at that point.  If he fell even half an inch at millions of lbs how fast should be be falling when he suddenly only weights 80kg again?   If he pushed and it buckled and he moved up half an inch before running out how fast should he now be flying at 80kg?  

The examples in the books just don't support any real world physics without accepting that the spiritual realm is making up for things in the favor of the protagonist in each moment.  

To drop and be traveling 120mph at 80kg and then tapping to 1million kgs in the last moment then you are slowing yourself to 0.0096mph.  Your body is now what?  You aren't jelly from the weight because magic allows you to keep breathing and working when you are that heavy.  Your bones aren't breaking and shattering from the weight because the magic solves it.  

 

There are too many examples of iron F proving and disproving the real world physics to say you are dying when being 1000000kg and taking a step or landing moving that slow.  If it didn't then Sazeds hands would have exploded everytime he dropped them on Koloss.  

If physics worked right in world steel pushing and iron pulling would be deadly everytime you land given that they work more like a gunshot than they do a nice gental push.  

Magic exists in the world and it is usually shown as being sparing to the user in that you don't kill yourself with it when the laws of physics say you should die. 

What we know is it protects you and that momentum is conserved (sometimes except in the case of becoming a rocket).  We haven't had the energy issue explained entirely and its a bummer trying to balance it.  

 

[alder24]

1 hour ago, Tamriel Wolfsbaine said:

If Wax or Vin or any other mistborn falls from 500 meters and uses steel to suddenly push a coin and not hit the ground how is that any different than hitting the ground?

They create upward force that over time decelerates their fall. It's not instantaneous, it's happening over time. And there is no 500m tall buildings in Elendel.

1 hour ago, Tamriel Wolfsbaine said:

If a Lurcher is about to hit the ground and suddenly pulls on an anchor from above what happens to that energy?

He creates an upward force, that over time decelerates his fall.  

All of this is consistent with physics. The energy is still there, but it's used to decelerate the fall, it's working towards other direction. Up this time, not down. There is nothing that magic needs to fix, this's simple force vectors.

1 hour ago, Tamriel Wolfsbaine said:

If he speeds up when storing part way through a jump why then didn't he suddenly eccelerate to a ridiculous speed when he fell through the ceiling and ran all of his metalminds dry?  

Because, there is air, there is drag, there is terminal velocity. That's why.
When he fell through the ceilings, he did accelerate. You know, gravity? 9,81m/s2? there was like 2m between floors, how fast would he go? 10m/s? And he was stationary, 0m/s for starting speed. And what's more, mass has no effect on gravitational acceleration. That's basic physics. It also doesn't affect drag force, only terminal velocity. Him changing mass, doesn’t change his rate of acceleration.

1 hour ago, Tamriel Wolfsbaine said:

If Wax is 80kg and spends all day storing 25% of that he is walking around at 60kg all day long.  Over the course of 24 hours he stores 1,728,000 kg.  

He stores that per what? Hour? Minute? Second? Millisecond? Picosecond? It's important to evaluate how much you get. And I don't think we know the ratio of storing exept X kg per time unit - as this is the only way it was explained - your number doesn't work that way.

1 hour ago, Tamriel Wolfsbaine said:

You aren't just increasing weight 10 or 20 times.  You can increase weight 21,600 times every day you spend your day storing at 75%.  

Diminishing returns (or what it's called when you tapping more than you store ratio was) will cut this number to a fraction of what it was, and that would only work for a moment, not time period, meaning, your speed would not get affected as the moment is not continuous, it's a point.

1 hour ago, Tamriel Wolfsbaine said:

He runs out of weight at that point.  If he fell even half an inch at millions of lbs how fast should be be falling when he suddenly only weights 80kg again?

Was he falling or was he stationary after reaching the top of his ascent and having 0 m/s speed? Or, what I said above, he used all of his mass instantly - instant isn't time period, instant doesn't last in time, it's a point in time. Therefore it's not affecting his speed, as in given time frame, his mass didn't change.

Edit:

I was right, in AoL when he destroyed a building with Steris (ch 19), he did it, after first reducing weight midair to gain speed, and after reaching top point in his arch with 0m/s speed, he took all the weight and used it in the moment.

1 hour ago, Tamriel Wolfsbaine said:

Interestingly we don't see Wax being more prone to injury at lighter weights either.  He says he doubles speed when he gets twice as light but outside of that conversation specifically we don't see it. In theory he should be able to use a single push off of the ground at a high weight and be able to send himself into orbit.

He said it's happening, and I remember him using that principle (I think) somewhere in the books, but because he didn't launch himself into space and burn in process for no reason, you deny it? Why would he go into space?

Edit - He reduced weight to gain speed when he rescued Steris in AoL.

1 hour ago, Tamriel Wolfsbaine said:

To drop and be traveling 120mph at 80kg and then tapping to 1million kgs in the last moment then you are slowing yourself to 0.0096mph.  Your body is now what?  You aren't jelly from the weight because magic allows you to keep breathing and working when you are that heavy.  Your bones aren't breaking and shattering from the weight because the magic solves it.  

How many time do I have to say, that iron is not pewter? You're not gaining any strength, you not gaining any endurance, durability, resistance. The only thing you gain is the ability to uphold your own weight. It's not pewter.

1 hour ago, Tamriel Wolfsbaine said:

If it didn't then Sazeds hands would have exploded everytime he dropped them on Koloss.  

No, because I'm saying if a regular person is able to do it without harm, then increased weight won't matter, it's still the same action. The ratio of "energy absorption per 1kg" or whatever didn't change.  It's still the same energy per every kilogram he has. The additional energy that he absorbs is solely provided by his mass, and won't absorb any more energy that was there before changing mass - like in the falling scenario.

1 hour ago, Tamriel Wolfsbaine said:

If physics worked right in world steel pushing and iron pulling would be deadly everytime you land given that they work more like a gunshot than they do a nice gental push.

No, because they provide force F, that works over time T and gives you acceleration A. Like real life physics. If a coinshooter starts pushing on a coin just before impact - he's dead. Nobody in the books did that ever. They all push far away to gradually decelerate and lose energy. Like it should work.

And we know from WoBs that our physics still works like it should work in Cosmere. Energy can't disappear. The 1st law of thermodynamics exists. Conservation of momentum works. Conservation of energy also must work, and this is more important than momentum. And we know that IRON IS NOT PEWTER!

 

This is the end for me. I've shown you the math. I've shown you the energy problem. I gave you an explanation that conserves both momentum and energy without breaking 1st Law of Thermodynamics. If this can't convince you, I'm just wasting more time trying to explain why you can't have 1m fall after falling for 499m.

Edited January 12, 2023 by alder24

[Tamriel Wolfsbaine]

7 hours ago, alder24 said:

They create upward force that over time decelerates their fall. It's not instantaneous, it's happening over time. And there is no 500m tall buildings in Elendel.

He creates an upward force, that over time decelerates his fall.  

All of this is consistent with physics. The energy is still there, but it's used to decelerate the fall, it's working towards other direction. Up this time, not down. There is nothing that magic needs to fix, this's simple force vectors.

Because, there is air, there is drag, there is terminal velocity. That's why.
When he fell through the ceilings, he did accelerate. You know, gravity? 9,81m/s2? there was like 2m between floors, how fast would he go? 10m/s? And he was stationary, 0m/s for starting speed. And what's more, mass has no effect on gravitational acceleration. That's basic physics. It also doesn't affect drag force, only terminal velocity. Him changing mass, doesn’t change his rate of acceleration.

He stores that per what? Hour? Minute? Second? Millisecond? Picosecond? It's important to evaluate how much you get. And I don't think we know the ratio of storing exept X kg per time unit - as this is the only way it was explained - your number doesn't work that way.

Diminishing returns (or what it's called when you tapping more than you store ratio was) will cut this number to a fraction of what it was, and that would only work for a moment, not time period, meaning, your speed would not get affected as the moment is not continuous, it's a point.

Was he falling or was he stationary after reaching the top of his ascent and having 0 m/s speed? Or, what I said above, he used all of his mass instantly - instant isn't time period, instant doesn't last in time, it's a point in time. Therefore it's not affecting his speed, as in given time frame, his mass didn't change.

Edit:

I was right, in AoL when he destroyed a building with Steris (ch 19), he did it, after first reducing weight midair to gain speed, and after reaching top point in his arch with 0m/s speed, he took all the weight and used it in the moment.

He said it's happening, and I remember him using that principle (I think) somewhere in the books, but because he didn't launch himself into space and burn in process for no reason, you deny it? Why would he go into space?

Edit - He reduced weight to gain speed when he rescued Steris in AoL.

How many time do I have to say, that iron is not pewter? You're not gaining any strength, you not gaining any endurance, durability, resistance. The only thing you gain is the ability to uphold your own weight. It's not pewter.

No, because I'm saying if a regular person is able to do it without harm, then increased weight won't matter, it's still the same action. The ratio of "energy absorption per 1kg" or whatever didn't change.  It's still the same energy per every kilogram he has. The additional energy that he absorbs is solely provided by his mass, and won't absorb any more energy that was there before changing mass - like in the falling scenario.

No, because they provide force F, that works over time T and gives you acceleration A. Like real life physics. If a coinshooter starts pushing on a coin just before impact - he's dead. Nobody in the books did that ever. They all push far away to gradually decelerate and lose energy. Like it should work.

And we know from WoBs that our physics still works like it should work in Cosmere. Energy can't disappear. The 1st law of thermodynamics exists. Conservation of momentum works. Conservation of energy also must work, and this is more important than momentum. And we know that IRON IS NOT PEWTER!

 

This is the end for me. I've shown you the math. I've shown you the energy problem. I gave you an explanation that conserves both momentum and energy without breaking 1st Law of Thermodynamics. If this can't convince you, I'm just wasting more time trying to explain why you can't have 1m fall after falling for 499m.

So I don't really need to argue the math.  And I am not trying to come off as contentious.  I do know that conservation of momentum is intentional in iron feruchemy.  That simply states that you slow as you get heavier and you speed up as you get lighter.  Wax certainly doesn't need to take off into orbit to demonstrate that it is possible.  As for energy... WoB specifically states potential energy is shed with iron feruchemy but momentum is preserved.  

I know pewter is pewter and iron isn't pewter.  However WoB clearly states that you get stronger relative to your weight.  It has its own diminishing returns as well but this is why Wax and Sazed don't crush themselves when they increase weight by a ton.  

I don't want to draw out a huge discussion on the math.  Iron feruchemy has gotten me spicey a few times because I want all logical math to work for it.  Again WoB explains that it is a tricky part of the magic and even Brandon had to surrender to "because magic" to make some things work.  

No math in these spoilers just the Word of the cosmere god.  Take it for what its worth.  

This WoB is where he says they conserve momentum but are breaking the laws of potential energy.  All of the others are really icing on the cake and very eye opening to what is one of the more challenging powers to explain and understand.  

I have had to eat a lot of crow on iron feruchemy and I'm not trying to feed crow here.  Just showing that certain laws of physics are trying to be kept in feruchemical iron where others are very specifically not being worried about.  I'm not a physicist. I just breathe for people and see a lot of traumas (see my cadmium posts and that is where my passion and desire for scientific accuracy is found).  Again, even there, I just need to accept that sometimes the magic in the books will break laws so we can have a cool story.  Purely flying as a ferring would work.  This example is specific to a winged suit and would be more like a bird flying.  Following the logic in these WoBs a ferring could survive a free fall.  

Spoiler

Brainless

You've always said that your favorite sort of magic was being a Coinshot or being a Windrunner because you really want to fly. So I thought that iron Feruchemy you can fly using just iron Feruchemy. So if you had a paraglider and a place to jump off of, you're paragliding, go downwards, your momentum increases, you increase your weight when you're going downwards. You pull upward and then you decrease your weight. Your velocity will increase and you'll go up--

Brandon Sanderson

We have thought about that. I'm not sure if the math-- Like, we're trying to conserve momentum. We're trying to follow the math of that. So the question is, would that work? It probably would, but I'd have to look at the math. Because I tried to make very clear in the Wax and Wayne books that we conserve momentum...

Really what we're doing is, we're breaking potential energy, right, when we're doing this. Because iron Feruchemy is just the weirdest of all of them. Because we're breaking potential energy, what you just said probably works, doesn't it.

Brainless

That was in context with the thing I was saying yesterday, about Feruchemical savants. If you did that every day for years, would you potentially get to the point where you could potentially make one side of your body heavier than the other side?

Brandon Sanderson

...There are many people in the cosmere who would think this idea has merit and they would want to test it.

MisCon 2018 (May 26, 2018)

Spoiler

Brandon Sanderson

Chapter Six

The fight in the ballroom

From the early days of the Mistborn books, I'd been planning how an Allomantic gunfight would go down. I felt it the next evolution in what has been stylistically a big part of these books.

There is a fine line to walk in a lot of these sequences. I've made something of a name for myself in the fantasy world by attempting to mix some scientific reasoning with my magic systems. At the same time, Allomancy was designed precisely with action sequences in mind. I wanted them to be powerful and cinematic—and a cinematic fight sequence is often at odds with realism. (Watch two people who really know what they're doing fight with swords sometime, then watch any fight sequence in a film. Most of the time, the film sequences stray far from what would really happen.)

So, as I said, I walk a line. Sometimes, there are things I just can't do because they violate what I've set up as the rules of the world. Other times, I design the setting and nature of the fight specifically to allow for certain types of cinematic sequences. One thing I like a lot about Wax’s abilities is the power he has to manipulate his weight. There's some realism to what he does—for example, increasing his weight doesn't make him fall more quickly, but it allows him to do some powerful things while falling. Destroying the chandeliers is an example.

At the same time, I acknowledge that the weight manipulation aspect of Feruchemy is one of its more baffling powers, scientifically. Is he changing his mass? If so, he should become more dense, which I don't actually make the case when it plays out in fights. (Otherwise, increasing his weight enough would make him impervious to bullets.) So, if it's not mass manipulation, is it gravity manipulation, like Szeth and Kaladin do? Well, again, not really—as when his weight increases, his strength and ability to uphold that weight increase as well. Beyond that, Wax can't make himself so light that he has no weight at all.

So . . . well, at this point, the ability to explain it scientifically breaks down. I do like what it does, but I have to set its boundaries and stick to them—and accept that some of what's going on is irrational. (And don't get me started on what should really be happening scientifically when Wayne speeds up time.)

Footnote: Brandon has stated that iron Feruchemy works by manipulating the Higgs field.
The Alloy of Law Annotations (March 14, 2014)

Spoiler

XMikethetrikeX

A question regaurding Feruchemical iron:

So, while Sazed was guarding one of the gates to Luthadel, he tapped weight to compensate, he had to tap pewter as well. Also, when he was climbing a tree, his strength to weght ratio rised, making it easier for him to climb it. Wax doesn't have to do this- when fighting Miles on the train, he's fine without any sort of muscular enhancement, and when he is climbing in the sets base, he notes that he does not make himself lighter because it would simply decrease his weight and strength equally (in contrast to Sazed climbing the tree).

So, is this difference for the same reason people can push/ pull on atium, being the you hadn't fully developed your idea for the cosmere yet? Or is it some other reason?

Brandon Sanderson

Hmm. I think the mistake is more on me writing the Wax scene than in the original. (For him climbing, specifically.) I'll put Peter on this and see if it's a continuity error we want to fix.

Skyward Pre-Release AMA (Nov. 3, 2018)

Spoiler

Calderis

I recently got the opportunity to ask you a question about Feruchemical steel and if it was a temporal effect and you told me to define that better. When tapping steel, the mind of the Feruchemist is sped up and physics affects their actions normally. When storing, their mind is not slowed and the effect seems tortuously difficult to amass. Storing generally seems to be the more dangerous/difficult option in Feruchemy, so does [Feruchemical steel] alter a person's personal relationship to the flow of time, with the disconnect between the Physical and Cognitive as a drawback of storing?

Brandon Sanderson

I see what you're asking. The mind-altering effects of [Feruchemical steel] are similar to the slight strength you gain from [Feruchemical iron]--it is your Spiritual nature adapting to the new influx of an attribute that it's not really expecting, and siphoning some of that investiture to make you capable of actually using it. So there is a slight temporal effect here, but nothing as big as I think you're looking for.

Footnote: This question is a follow-up to this question.
Skyward Pre-Release AMA (Oct. 31, 2018)

Spoiler

Seonid

I noticed that you-- Was that a retcon on the way iron Feruchemy works?

Brandon Sanderson

What do you mean?

Seonid

There's a researcher who talks to Wax, asking him about whether he's changing his mass of whether he's changing whether the planet perceives him-- affecting his gravity.

Brandon Sanderson

Right. It's more a re-- Defining something I didn't pin down strongly enough. I wouldn't call it a retcon because it's something that nobody really did until Wax, really, in the series. The only one really capable of doing that in the original trilogy would have been the Lord Ruler, maybe some of the Inquisitors, but we don't have viewpoints from them. So I wouldn't call it a retcon I would just say it’s something that didn't come up in the first series that now I have to make sure is clear.

Seonid

So is it Higgs field stuff going on?

Brandon Sanderson

Yeah. Mmhmm.

Seonid

My idea was right.

Brandon Sanderson

Mmhmm.

Bands of Mourning release party (Jan. 25, 2016)

Spoiler

Questioner

How effective would pewter Allomancy and iron Feruchemy be in a Twinborn?

Brandon Sanderson

That would do some really cool stuff. Some really cool stuff.

JordanCon 2016 (April 23, 2016)

Spoiler

Phantine

I actually asked Peter Ahlstrom (who tends to handle math and magic system interactions with physics for Team Sanderson) about this a little while ago

A couple of friends and I are discussing if the iron feruchemy causing changes in speed is a retcon (since there's a mention in AoL that "increasing his weight manyfold would not affect his motion"), or if the effect is just more complicated (like only causing an instant change in speed if Wax changes weight while actively pushing on something).

Are you willing to weigh in on that, or is it just something we shouldn't be thinking too hard about?

Thanks

And his response was

I just don't know the answer to this question.

So I personally think the explanation is either 'Brandon thought it would be cooler for shifting your weight to change your velocity, and forgot he had mentioned it a couple times' or 'this is Wax's twinborn perk'. I'm leaning towards the latter, since the person who writes the magic system summaries at the end of the book specifically interrogated Wax about the effects, and mentioned she specifically was interested in his very unusual power combination.

As for the density thing, there is an explicit mention that you appear to get stronger when tapping, but only to the extent that you can still stand up and walk around - you still have more difficulty moving around overall. So (to pull out random numbers), if you're at 200% normal mass, you have 180% normal strength, and at 50% mass you have 60% normal strength. That means Wax habitually going around at 75% weight so he's 'light on his feet' makes sense - even if he's weaker overall, he's proportionally stronger.

The way I personally think about things for bullets or whatever, anything 'inside' the body (where 'inside' is defined in the same way that pushing/pulling metal 'inside' the body uses it) interacts with your body as if it were normal. So tapping iron doesn't cause your ultra-massive blood to be impossible for your heart to pump, but it also doesn't prevent a bullet from passing through your flesh. That seems to be consistent with how it's portrayed in the books.

Brandon Sanderson

Just a note: in the quote of mine above, I was trying (I believe) to find a way for Wax to indicate that weight doesn't influence the rate at which he falls. IE, acceleration in regards to gravity. It's tough, and I made the call (perhaps incorrectly) not to use modern physics terminology in the W&W books. It has been very hard then to explain:

1). Wax changing his weight doesn't change the pull of gravity on him, or the rate at which he falls. 2) He DOES follow the laws of conservation of momentum.

My talking around these things has let me to tie a few paragraphs in knots.

General Reddit 2016 (Feb. 19, 2016)

I know my look at the physics is ignoring parts of it.  I get hung up on conservation of momentum and the speed changes while not paying as much attention to the energy because that is what has been evident in what iron does anyways.  The laws of energy are WoB confirmed to be broken with iron feruchemy where conserving momentum is specifically said to be followed.

As for all of my other metaphors and examples they are because I am a simple man.  I have seen many broken bodies beyond the point of help.  I like shooting and cosmere novels and thinking up nerdy character concepts for head cannon cosmere games. No hard feelings at all.  I enjoy the firey math posts because I can always learn.  

Edited January 13, 2023 by Tamriel Wolfsbaine

[alder24]

5 hours ago, Tamriel Wolfsbaine said:

 No hard feelings at all.  I enjoy the firey math posts because I can always learn.  

No problem, no hard feelings on my side as well. I enjoyed this discussion with you, I had fun doing math.

5 hours ago, Tamriel Wolfsbaine said:

I know my look at the physics is ignoring parts of it.  I get hung up on conservation of momentum and the speed changes while not paying as much attention to the energy because that is what has been evident in what iron does anyways. 

When you look at the math, the conservation of momentum is just a small moment in the whole problem which is resolved with the conservation of energy. They are issues with energy, but they can be "resolved" without breaking any laws and the discussed problem still remains logical. 

5 hours ago, Tamriel Wolfsbaine said:

The laws of energy are WoB confirmed to be broken with iron feruchemy where conserving momentum is specifically said to be followed.

Yes they are broken, as seen in the math. However Cosmere has its own laws of conservation of energy and thermodynamics that aren't broken in this scenario. 

Also look again at WoBs you provided. It's stated multiple times that F-Iron provides only strength to uphold your new weight, not muscle strength or more endurance. This is the whole point. The only reason that Sazed or Wax is able to punch harder or withstand being punched is because the force is greater (F=Ma), Newton's 3rd law of dynamics, and inertia. They gain no strength, but because they are more massive, they are able to punch harder or be punched without being moved by it. But this doesn't apply to free fall.

 

Overall it was fun to have this discussion with you, even if we didn't reach an agreement in the end.