3 Lashes only use the Gravity Surge – Atmospheric Pressure Surge abilities are not in Ars Arcanum - WoR Updated

[KiManiak he/him]

I don't think this has been mentioned on the forums yet, so here we go:

 

 

As shown in the Ars Arcanum near the end of the Way of Kings, the 3 Lashes (Basic, Full and Reverse) for Windrunners  are described as:

 

1. Basic – Revoke object’s spiritual gravitational link to the planet below and temporarily link it to a different object or direction.  Believed to use Gravity Surge.

 

2. Full – Infuse objects with Stormlight, which would bind objects together as one.  Believed to use Atmospheric Pressure Surge.

 

3. Reverse – Infuse objects with Stormlight, give mental command and create a gravitational pull to the objects.  Believed to use Gravity Surge.

 

The narrator of the Ars Arcanum (who I’m leaning more towards being Jasnah, but that's probably another post) expresses that this is based off of research of various sources, but makes it clear that in no way do they feel their information is 100% accurate.

 

Up until now, it has been logical to assume that when Kaladin binds rocks or objects to walls, he is indeed using a Full Lashing, with the Atmospheric Pressure Surge facilitating the actual bonding.  However, the information given to us in Chapter 12 of Words of Radiance may have provided the reader with evidence that refutes that assumption, and the conclusions of the Ars Arcanum itself. 

 

After Kaladin has inhaled stormlight from the diamond chip, infused the stone and stuck it to the wall, Rock notices spren interacting with the bonded stone:

 

 

 

“Spren,” Rock said, pointing.  “They pull the stone against the wall.” (emphasis mine)

 

The word choice is noteworthy.  Pull against the wall, not push. It’s fair to say that the effect of Pressure is to push down on things, whereas the effect of Gravity is to pull on things.  

 

 

 

What could this mean?  Well, it could be explained at least a few ways:

 

1. Rock misspoke and meant “push” instead of “pull.”

 

2. Kaladin was using a Basic/Reverse Lashing and changed the gravitational pull on the stone.

 

3. Kaladin was using a Full Lashing, but Full Lashings are a function of the Gravity Surge and not the Pressure Surge.

 

Taking them in order:

 

(1) is possible, but Kaladin also looked and saw the spren interacting with the stone and did not correct Rock’s assessment.  Since Sigzil is testing and studying Kaladin’s abilities, it would be logical to assume that Kaladin would want the data Sigzil is using to be as accurate as possible. 

I would therefore submit that Rock was speaking accurately.

 

(2) is also possible, but switching the pull of Gravity from one direction (the floor) to another (the wall) does not mean that the other rules of Gravity are ignored.  A strong application of force should move the object along the wall, while still having the object be oriented towards that direction.  In other words, the stone should slide up or down the wall, just like it would slide along the floor if you were to push it with your foot.  Yet Rock hangs onto it (or at least, he did the first time) and the stone doesn’t budge. 

I would therefore submit that the spiritual gravitational link of the stone wasn’t shifted to the wall, the stone was bonded to the wall.

 

I think (3) is most likely.  The stone doesn’t move; it is bonded to the wall.  The spren are pulling the stone against the wall, and exert a strong enough pull that someone the size of Rock is unable to have the stone budge.  The pull of the Gravity Surge, in this case, is significantly stronger than normal and acts to bond an object to another object; the Pressure Surge is not active in this case.

 

 

If this is correct, then the 3 Lashes don’t use the Pressure Surge at all, yet we know that Windrunners use both Gravity and Pressure Surges.  Therefore, the 3 Lashes can’t be a complete list of all of the Windrunners’ abilities; there are likely at least 3 more that probably use the Pressure Surge in some form or fashion.

(I would not be surprised if the Force Push ability is one of them)

 

I welcome thoughts, criticism, etc.

[Awesomeness Summoned he/him]

I've actually been thinking this for a while, especially since the last excerpts, but hadn't had the time to break the theory down so up vote for saving me the trouble.

It always seemed to me that the three lashings couldn't possibly be all you could do with gravity and air pressure manipulation and sticking things together with air pressure seems like the least creative use of that ability, especially when you can conceivably do the same thing with gravity effects. The term lashing in itself suggests to me pulling on something, not pushing.

Teft mentions rumors of KR flying and they play that off as just fanciful tales but that would be easy to accomplish with Kaladin's surges. An airplane flies due to lower air pressure above the wing than below creating lift. Reduce the gravity on yourself, place some air pressure behind you as well and flight is easy. I also picture kaladin blasting people away from him with surges of air pressure expanding out from him

I'll take the theory a little further even to suggest Szeth might only have access to the gravity surge. If a full lashing is only gravity, then he hasn't shown the ability to use any of the air pressure surges. He seems extraordinarily versed in the lashes so why would he have no knowledge of how to use the pressure surges as well if he can in fact access them.?

Edit: adding to your descriptions from the book on when people were lashed to the wall, in order for air pressure to be holding them there as strongly as described, they would have been feeling an enormous amount of force on their chests. They likely wouldn't have been able to breath. Instead they act like nothing is different except their back being stuck to the wall. Chapter 12 paints a pretty clear picture that air pressure is not used for the full lashing

Edited January 31, 2014 by aWESomeness summoned

[Ness]

I don't agree that the pressure surge can only push.  If there is a difference in pressure between two areas, it is totally possible for the difference in pressure to pull on something.

 

There is an experiment where you put a hard boiled egg on the top of an open coke bottle which has a candle inside.  The candle will heat the air until there is no oxygen, then the fire will go out.  The air will then cool again, creating a difference in pressure, causing the egg to get sucked into the bottle.  Clearly, the egg is PULLED into the bottle, not pushed.

 

(You can see videos of what I am describing on youtube.)

[DefiantBurrito]

Couldn't you actually use "Pressure" to pull the rock against the wall using suction?  The spren between the rock and the wall could actually be removing air, causing a suction effect to occur.  So I don't think this is really solid proof.

 

That said, I like the idea.  It does seem like Gravity alone *could* explain all three of the Lashings, and the combination of Gravity and Pressure seems like it could be able to do a lot more than what we've seen so far.

[Aether he/him]

(I would not be surprised if the Force Push ability is one of them)

I feel flattered that you remembered my Thread on this (similar) subject. I hadn't considered the possibility a Full Lashing might not even be using the Pressure Surge at all, though, though considering it now, it does seem possibly, if not that likely. We do agree, however, that the Three Lashings seem unlikely to be the extent of a Windrunner's power.

 

I don't agree that the pressure surge can only push.  If there is a difference in pressure between two areas, it is totally possible for the difference in pressure to pull on something.

 

There is an experiment where you put a hard boiled egg on the top of an open coke bottle which has a candle inside.  The candle will heat the air until there is no oxygen, then the fire will go out.  The air will then cool again, creating a difference in pressure, causing the egg to get sucked into the bottle.  Clearly, the egg is PULLED into the bottle, not pushed.

 

(You can see videos of what I am describing on youtube.)

There has some discussion on the nature of the Full Lashing, and it has been suggested that it is technically creating a vacuum between the objects, which provides the adhesive nature of it. I cannot remember in what Thread this was discussed, though.

EDIT: Come to think of it, the thing about vacuum might have come up in my own Thread, which KiManiak linked to. I haven't reread it lately, though.

 

EDIT 2: A quick word search for "vacuum" in my Force Push Thread provided these two posts. I seem to remember a more extensive discussion on this particular point, though, so it is likely that there is another and more extensive Thread where this came up.

 

EDIT 3: Another more general word search provided this Thread. I've just barely skimmed it, but it does seem to be the one I was referring too.

Edited January 31, 2014 by Aether

[Awesomeness Summoned he/him]

I don't agree that the pressure surge can only push.  If there is a difference in pressure between two areas, it is totally possible for the difference in pressure to pull on something.

 

There is an experiment where you put a hard boiled egg on the top of an open coke bottle which has a candle inside.  The candle will heat the air until there is no oxygen, then the fire will go out.  The air will then cool again, creating a difference in pressure, causing the egg to get sucked into the bottle.  Clearly, the egg is PULLED into the bottle, not pushed.

 

(You can see videos of what I am describing on youtube.)

I'm not so sure you can say it is CLEARLY pulling not pushing. That force being created is because the molecules want to reach equilibrium. Things are more dense and at higher pressure outside the bottle so those extra molecules outside want to force their way inside. The egg blocks them from entering and in turn is held in place by their mad rush to get to the area of least density (inside). But you are right, that vacuum effect does not create a huge amount of "pushing" force on the outside of the egg so my assumption that Lopen would have difficulties breathing is likely not correct even if it's air pressure creating it. I'll admit I'm not a physics major so I could be off on the process but that's how I understand that vacuum effect to be working

[el_warko he/him]

Disclaimer, I ain't no pysicist so maybe overlooking things, this is a laymans take.

 

Your arguments are sound (and I agree with your assessment) but WRT to 2) above, your argument is only valid if the force level of gravity imbued in the stone is of a less than the force level of Rock's pull towards Roshar. In round numbers, say Rock has a mass of 100kg (220lbs) and the stone 453g (1lb) give you a bit of volume (167cm³, 10in³) to hang off (assuming Quartz (or varient (SG:2.7)).

 

Roshars gravity is 0.8 of earth, therefore, std gravity has a value of 7.84ms^-2 (26.5fts^-2). Therefore the force pulling Rock towards Roshar, his weight is 784Nm (578ftlbs). If the gravitiational force imbued in the stone excedes that, it should hold him, nominally >221G.  Which admittedly is a lot.

[Ness]

I'm not so sure you can say it is CLEARLY pulling not pushing.

 

True, I could expand on this.  Think of pressing your hands tightly together, forcing the air out of your palms. If you start to move your hands apart, your palms stick together, this is because a difference in pressure.  While your palms resist being pulled apart, you don't feel anything on the back of your hands pushing them together, you feel a force on your palms pulling them together.

 

Thus, the pressure surge should be able to have pulling forces, so it makes sense for a full lashing to use the pressure surge. I agree with the idea that there should be much more you can do with pressure and gravity surges though

[Aether he/him]

Disclaimer, I ain't no pysicist so maybe overlooking things, this is a laymans take.

 

Your arguments are sound (and I agree with your assessment) but WRT to 2) above, your argument is only valid if the force level of gravity imbued in the stone is of a less than the force level of Rock's pull towards Roshar. In round numbers, say Rock has a mass of 100kg (220lbs) and the stone 453g (1lb) give you a bit of volume (167cm³, 10in³) to hang off (assuming Quartz (or varient (SG:2.7)).

 

Roshars gravity is 0.8 of earth, therefore, std gravity has a value of 7.84ms^-2 (26.5fts^-2). Therefore the force pulling Rock towards Roshar, his weight is 784Nm (578ftlbs). If the gravitiational force imbued in the stone excedes that, it should hold him, nominally >221G.  Which admittedly is a lot.

Even if the pull (push, whatever) towards the wall is stronger than Rock's push (pull, whatever) towards the ground, this should still allow it to slide downwards on the wall (if a bit slowly) as long as the friction between the wall and the rock isn't too excessive.

 

Unless a Full Lashing is just a Simple Lashing to a specific point on the wall, and not just its general direction.

Edited January 31, 2014 by Aether

[KiManiak he/him]

I like this; I hadn’t considered the potential suction-like aspect of the egg example referenced above when considering the Atmospheric Pressure Surge’s role in a Full Lashing.  It is something to consider.

 

 

 

 

I freely admit my grasp of physics is not exceptionally strong (I only studied it in high school and that was decades ago) so I won’t be able to argue too much of the scientific specifics.  But I will try to argue with just a layperson’s reasoning.

 

 

There is an experiment where you put a hard boiled egg on the top of an open coke bottle which has a candle inside.  The candle will heat the air until there is no oxygen, then the fire will go out.  The air will then cool again, creating a difference in pressure, causing the egg to get sucked into the bottle.  Clearly, the egg is PULLED into the bottle, not pushed.

 

The problem I have with the egg example is that there is some form of air/atmosphere that is pulling/sucking the egg into the bottle.  The egg isn’t sticking to anything after it goes through the bottle, correct?

 

Couldn't you actually use "Pressure" to pull the rock against the wall using suction?  The spren between the rock and the wall could actually be removing air, causing a suction effect to occur.  So I don't think this is really solid proof.

 

This suction argument seems like a decent possibility and I admit my grasp of suction alone isn't all that strong (ba dum bum). I guess my response to this would be that according to Rock the spren appeared to be pulling the stone against the wall, not necessarily removing air from the wall.  But would Rock even be able to comprehend and recognize if the spren were pulling the air out, as opposed to pulling the stone towards the wall?  This is a weak counterargument; I fully admit that. I don't have anything stronger at this time. Upvote to you.

 

I feel flattered that you remembered my Thread on this (similar) subject. I hadn't considered the possibility a Full Lashing might not even be using the Pressure Surge at all, though, though considering it now, it does seem possibly, if not that likely. We do agree, however, that the Three Lashings seem unlikely to be the extent of a Windrunner's power.

 

There has some discussion on the nature of the Full Lashing, and it has been suggested that it is technically creating a vacuum between the objects, which provides the adhesive nature of it. I cannot remember in what Thread this was discussed, though.

EDIT: Come to think of it, the thing about vacuum might have come up in my own Thread, which KiManiak linked to. I haven't reread it lately, though.

 

EDIT 2: A quick word search for "vacuum" in my Force Push Thread provided these two posts. I seem to remember a more extensive discussion on this particular point, though, so it is likely that there is another and more extensive Thread where this came up.

 

EDIT 3: Another more general word search provided this Thread. I've just barely skimmed it, but it does seem to be the one I was referring too.

 

Yeah, I definitely remembered that post when you did it. I see you edited this post since I initially read it, so I haven't had the opportunity to review the posts you linked.  I'll check them out.

 

True, I could expand on this.  Think of pressing your hands tightly together, forcing the air out of your palms. If you start to move your hands apart, your palms stick together, this is because a difference in pressure.  While your palms resist being pulled apart, you don't feel anything on the back of your hands pushing them together, you feel a force on your palms pulling them together.

 

Thus, the pressure surge should be able to have pulling forces, so it makes sense for a full lashing to use the pressure surge. I agree with the idea that there should be much more you can do with pressure and gravity surges though

 

The hand example is an interesting one.  I tried it a few times, and my palms did stick together somewhat when I tried to pull them apart.  Assuming this is purely the work of pressure and not that of friction or some other agent (like the sweat/epithelial cells facilitating the sticky feeling), then that’s an interesting example of pressure.  Could this type of pressure be strong enough to resist a rather strong application of force attempting to separate the two objects?  Similar to a big Horneater like Rock placing all of his dead weight against it?  And it not budge at all?

 

Even if the pull (push, whatever) towards the wall is stronger than Rock's push (pull, whatever) towards the ground, this should still allow it to slide downwards on the wall (if a bit slowly) as long as the friction between the wall and the rock isn't too excessive.

 

Unless a Full Lashing is just a Simple Lashing to a specific point on the wall, and not just its general direction.

 

Full Lashing be a Basic Lashing to a specific point of the wall, and not a general direction?  That’s an interesting possibility as well.  If it were a Basic Lashing to a specific point, lashed several times over, I could see that potentially working. 

 

 

I don’t know; it seems like it would be easier for the Full Lashing to work if it were a function of the Gravity Surge than if it were one of the Pressure Surge.  That, along with the evidence of the spren pulling the stone towards the rock, and the fact that the other 2 Lashes are clearly demonstrations of the Gravity Surge lead me to theorize that the Full Lashing is more likely to be due to Gravity then Pressure.

 

But I do admit that I no longer think it is as rock solid as I did when I wrote this a little bit ago.

 

 

Edit To Add: Yeah, I can see after skimming some of those posts Aether linked to, that "sticking my big fat toe" into this arena would probably require a far greater understanding of physics/pressure/friction/"microscopic supercells of vacuum" (and other terms that I'm only vaguely familiar with) than I currently have. 

 

But if others still have more to say about this matter, I welcome the discussion.  

Edited January 31, 2014 by KiManiak

[vikorr]

A few thoughts :

 

- suction pressure (ie. the pressure of a vacuum), like what happened to the egg, or what happens to a plumbers suction cup etc. - requires a seal. Without a seal it simply doesn't work. So atmospheric pressure to 'bind' one object to another, almost always has to push.

 

- If you use pressure to bind A to B - A would exert pressure on B...and if B isn't rooted in the ground or stable...A could move B...unless pressure was applied to both sides. In this latter case, both objects could feel 'squeezed'

 

- you could use gravity to bind A to B - the most effective way would be to lash A to B and B to A. In this latter case, the two objects would feel attracted to each other.

 

- you could combine both the gravitational surge and the pressure surge, to combine all the above...I don't think anything will move after that.

 

- in terms of spren - if they are attracted to pressure - one would think they would end up on the top side of the object where the push is, but the bind spren are always on the bottom. Then again, maybe they like physical contact - who knows.

[Punter]

When I first read atmospheric pressure I had always thought it would be something to do with the highstorms, like riding them or something similar.

 

I think it interesting to note thought that Syl acting in a capacity identified as a windspren has a tendency to stick things together, if that is behaviour of a windspren then you'd think that would lead more credence to an atmospheric surge acting in a way we don't full understand as opposed to a gravity surge (or alternatively that Syl was just using abilities greater than that of a typical windspren).

[Moogle]

I disagree with the OP here.

 

1. What Rock says has is irrelevant. Pressure could easily creature a vacuum (which it probably does) by pushing air out of the way. This results in a 'pull'.

 

2. Gravity works on whole objects in the Cosmere, not part-objects. Szeth has not shown it is possible to Lash half an arrow one way and half an arrow another way, breaking it apart.

 

3. You're proposing Szeth and Kaladin have both never used the Pressure Surge if this theory is true. (Kaladin may have used a pressure wave against the Parshendi.) Somewhat farfetched for Szeth.

 

4. There is an order named Bondsmiths who most likely have the Pressure Surge. Hence their name. You'll need to propose a Surge that isn't Gravity for them to have to allow for bonds and say Bondsmiths are Order 8.

Edited January 31, 2014 by Moogle

[Chlehrma]

I always thought atmospheric pressure was referring to the passage where the storm father tells Kaladin that people no longer "rode" the storms.

[TomR]

3. You're proposing Szeth and Kaladin have both never used the Pressure Surge if this theory is true. (Kaladin may have used a pressure wave against the Parshendi.) Somewhat farfetched for Szeth.

I agree.  The only way I can see this with Szeth is if Honorblades/Heralds only have access to one Surge each.

[bartbug he/him]

That could work, because there's ten surges...

[The Rooster he/him]

It's interesting that the identification of the surge needed to be further distinguished from "Pressure" to "Atmospheric Pressure". As an Engineer I think the distinction is unnecessary as pressure is pressure. I think more specifically they are talking about air pressure (the force which makes Rock call everyone else Airsick lowlanders) to make it easier for most people to conceptualize.   Because they've made the distinction I think we've seen all of the surges, we just have yet to see the lengths and creativity to which Kaladin can elevate it.  I'd love to see more but I'm assuming the full lashing is caused by a vaccum between objects and the spren are just bondspren attracted to the bond (Though this is a conversation Syl has with Kaladin in WoK, are the spren attracted by the bond or causing ... blah blah etc. etc.). 

Edited January 31, 2014 by AG Rooster

[Aminar]

Suction needs a seal, but gravity needs a massive object. Stormlight allows for both. Gravity is more indiscriminant. I think that if gravity were part of the binding two objects together it would attract more objects, not just seal them together.

In addition the binding causes spren, something gravity has not done so far. Suction hasn't been seen as much, and it makes more sense to have suction spren than gravity spren.

[Shardlet he/him]

Suction is an illusion.  Similar to darkness and coldness.  Darkness is an absence of light.  Coldness is an absence of heat.  With suction, the force is applied due to a pressure gradient between a low pressure area (such as a vacuum or partial vacuum) and a higher pressure area.  With a suction cup, a low pressure area is created when a fluid is expelled from the cavity, between the suction cup and the surface the suction cup is adhered to, and the suction cup mechanically springs back to it's original shape.  However, the pressure difference between the fluid external to the suction cup and the cavity is what causes the suction cup to hold. The higher fluid pressure external to the suction cup pushes on the outer surface of the cup and prevents the cup from returning to it's natural shape.  It is an equilibrium condition.

 

With a vacuum cleaner, a fan creates a lower pressure area by pushing air from one place to another.  The "suction" is a result of the interaction of the higher pressure area outside of the tube with the low pressure area inside the vacuum cleaner.  The force is applied by the higher pressure,not the lower pressure.  Similarly, if you are in space and a hole forms in the hull of your spacecraft, you are blown into space, not sucked.  The air moving from the pressurized area to the vacuum carries loose materials with it like leaves picked up by the wind.

[WhiskeyJackDaniels he/him]

I've always imagined a full lashing is effectively the same as doing the same thing as reverse lashing two objects together simultaneously, so they are constantly pulling at each other. It definitely seems like a gravitation surge ability.

[hoser he/him]

Eh, needs more toadhandwavium.

[Sirscott13 he/him]

I agree with the theory that all the lashings have been seen. The ars ancarnum shows that the author assume it works with atmospheric pressure. It's possible it was misnamed.

Secondly pressure can force two objects together if the lashing is sprayed on the floor, it creates a bond when you step on it because the lashing forces the foot to be more suceptable to the normal atmosphere pressure. The pressure seems silly but think about how small changes can affect objects. An experiment done with a basket ball lowered into the mid Atlantic trench resulted in it imploding and becoming one of the hardest materials discovered. The pressure was just to much. This could act the same way, maybe the lashing just creates a huge pressure difference and the bound objects aren't affected by suction or even force, but by sheer force per square inch between the two.

Thirdly one could ride the winds by controlling gravity. Also airplanes fly simply by using air pressure differences (I'm an aviation major). But I still believe they rode the winds by manipulating their own gravity and flying/falling how ever they wanted.

Fourthly, the pressure surge makes sense because the bondsmiths share the surge. Their name is BONDsmith and the surge causes things to become bound.

Fifth lay as stated above, wind Spren can bind things briefly, wind Spren or air Spren aka pressure Spren.

Sixth, I think the kaladin pressure explosion came because of how he was able to access stormlight more and the energy being released like a damnation being destroyed resulted in a shockwave of energy that was a one time thing

And lastly it would make sense that the Honor blade Szeth has would have the full wind runner surges to represent leading the wind runners

[Kurkistan he/him]

My apologies if someone in the thread already mentioned this, but I just thought I'd drop in some WoB: The full Lashing "does have to do with pressure."

[FingerstyleFunk he/him]

To those who continue to insist that the Full lashing makes more sense as a gravitational effect than an atmospheric one, I think the problem is mainly that your insticts about how much force atmospheric pressure exerts are probably way off.

 

Below is a graph (original source, which also has a pretty good general explanation of how suction cups carry load) of load bearing capacity for suction cups, based on -0.6 bars of pressure within cup. That's -8.7psi, relative to atmospheric pressure, which on Earth at sea level is 14.7psi.

 

Even if Rock is truly huge (150kg) that only translates to a 350mm suction cup (250mm if he's hanging from a horizontal surface, allowing us to ignore friction), with approximately a half vacuum. Assuming that the magic/handwavium involved can create something closer to a pure vacuum even between irregular surfaces, it looks very plausible for this to be what's holding the stone/Rock up.

 

In contrast, for it to be gravitational force... let's say the stone they're using is 10kg and Kal's gravitationally attaching it to hang from a horizontal surface. That means he needs to put 15 Gs on it just to match Rock's theoretical weight. More if it's attaching to a vertical surface and relying on friction to hold the load. Note that Szeth always mentions specifically when he's doing a multiple Basic lashing, so it's less likely to be something Kal is doing instinctually.

 

Edit: And of course WoB makes the analysis irrelevant... but I'll leave it just for the sake of helping people gain better instincts about the mechanics of the world around us.

Edited January 31, 2014 by FingerstyleFunk

[KiManiak he/him]

My apologies if someone in the thread already mentioned this, but I just thought I'd drop in some WoB: The full Lashing "does have to do with pressure."

 

Word of Brandon is Word of Brandon.  So be it; Full Lashings use Pressure.  Thanks for the reference.

 

To those who continue to insist that the Full lashing makes more sense as a gravitational effect than an atmospheric one, I think the problem is mainly that your insticts about how much force atmospheric pressure exerts are probably way off.

...

Even if Rock is truly huge (150kg) that only translates to a 350mm suction cup (250mm if he's hanging from a horizontal surface, allowing us to ignore friction), with approximately a half vacuum. Assuming that the magic/handwavium involved can create something closer to a pure vacuum even between irregular surfaces, it looks very plausible for this to be what's holding the stone/Rock up.

 

In contrast, for it to be gravitational force... let's say the stone they're using is 10kg and Kal's gravitationally attaching it to hang from a horizontal surface. That means he needs to put 15 Gs on it just to match Rock's theoretical weight. More if it's attaching to a vertical surface and relying on friction to hold the load. 

 

Cool.  I appreciate the information, explanation and visualization!