How Anchors Work

[IvoryRoad]

Okay. When an allomancer burns iron or steel, he/she can push or pull on a metal source. The force is directed straight through the allomancer's center of gravity. This we know.

But how does this principle apply to anchors?

The center of gravity is a single point in the metal source, right? Allomantic indicator lines (let's call them AILs), I would imagine, connect the allomancer's center of gravity with the anchor's, giving them a visual frame of reference to know where they're going to fly when they burn. The AILs are always described as straight lines, never wedge-like or any other shape. Some are thicker, indicative of the anchor's strength, but I don't think they ever get super wide - this is a detail that Brandon would mention, I think.

Essentially, the sum of these facts is that a single push or a pull against one given anchor should have only ONE possible direction of motion, along the vector denoted by the AIL. A principle like this is easy to ignore, since with small anchors, there's never enough distance between the anchor's center of gravity and its boundaries to be noticable. Coins and window latches will all move basically the same.

The confusion I have is when a longer anchor comes into play. Think of a spire on Kredik Shaw. Vin and the Inquisitors use them as anchors many times in the trilogy, both for pushing and pulling. But, despite their larger size compared to a coin or latch, shouldn't the metal spire only have one center of gravity to push or pull against? I could imagine a long line of points along the spire's "axis" of gravity, straight up the middle, but the result of this would be an AIL that begins at the allomancer's COG and expands in a wedge shape, a continuous triangle, from the top of the spire to the bottom. Come to think of it, though, in the universe, all planets are round. A spire or elongated object, given time, will eventually collapse inward, until its shape roughly reflects an equal gravitational pull from all angles toward one COG.

So how can an allomancer pull him/herself to the top of a spire, or to any point they please, when there is only one COG to interact with?

The idea crops up again, somewhat, in AoL, when Wax pushes himself along the rail lines. He describes his actions as a "continuous" push behind him - but against what COG? I suppose a railway track is actually a bunch of linked pieces of metal, not a continuous chunk, and Wax could simply be pushing against individual pieces of the rail.

Regardless of the explanation for the incident in AoL, this leads us to an interesting thought experiment:

Imagine a really long cylinder of metal laying on flat ground. Say five miles long. It is continuous - that is, there are no seams or individual parts to the cylinder. An allomancer in the exact center pushes himself along the pole, from the COG. At what point - if any - will the allomancer stop moving? Can he push on a point that is not the COG? If he was at the end of the cylinder, out of range of the central COG, could he allomantically interact with the cylinder at all? This would be rather contradictory, IMO.

I'm open to anyone with a better understanding of physics or allomancy than I to submit a possible solution to my confusion. Sorry if the post seems a little bit rambling; I had some thoughts in the middle of writing them down.

[Vortaan]

I seem to recall Kelsier Pushing on end and Pulling on the other end of a bar of steel in order to make it spin. This leads me to believe that with greater concentration you can Push or Pull anywhere on a piece of metal, but you will instinctively Push or Pull on the COG.

[fyodor]

Can you cite to wherever it says that that pulls can only be attached to an object's center of mass? I know that it is drawn to the Lurcher's center of mass, but I'm not familiar with where the books say that an object can only be Pulled from its center of mass.

[IvoryRoad]

Can you cite to wherever it says that that pulls can only be attached to an object's center of mass? I know that it is drawn to the Lurcher's center of mass, but I'm not familiar with where the books say that an object can only be Pulled from its center of mass.

See, that's what I'm wondering. It's clear from the books that a push or pull is possible outside the point indicated by the AIL's location, but how is that location determined? I think it would lend a certain symmetry to allomancy if the line simply connects the burner's COG to the anchor's. But when the burner chooses to push on the edge of a bar, rather than against the AIL, he can do this as well. The question is, at what point does this leave the instinctual realm and require specific focus? I think Vortaan hit it right on the head, actually. Against a cluster of coins, a "blanket push" will interact along the AIL, toward the COG, requiring minimal concentration. But when more specific pushes are desired, pushes and pulls can be manipulated at will.

Which rather defeats the purpose of my OP. I feel rather foolish, all of a sudden. Thanks for the input, folks. Nothing to see here.

EDIT: actually, I just thought of something rather interesting. Why isn't it possible,then, for an allomancer to funnel his push or pull through a part of his body that is not the COG? Seems rather unfair that it can be done to anchors, but not the burner himself.

Edited December 27, 2011 by IvoryRoad

[ReaderAt2046]

Maybe it can, but nobody's figured this out yet.

[IvoryRoad]

Maybe it can, but nobody's figured this out yet.

Seems like the kind of thing one would experiment with. In fact, I think it might be occurring instinctively, anyway; Wax uses steel to enhance his shots often, and pushing on a bullet that is not perfectly lined up - even by a hair's breadth - with his COG would throw the shot off substantially. It's impractical in combat to take the time to line up shots with such precision.

[ReaderAt2046]

It's also possible that the rules apply differently to humans as opposed to anything else.

Kind of like how humans are just about the only thing on Roshar that doesn't have a spren, or that balefire vaporises an entire human (or Trolloc or Myrdraal, who are the same as humans for my current purpose) but cuts through inanimate matter.

[IvoryRoad]

It's also possible that the rules apply differently to humans as opposed to anything else.

Kind of like how humans are just about the only thing on Roshar that doesn't have a spren, or that balefire vaporises an entire human (or Trolloc or Myrdraal, who are the same as humans for my current purpose) but cuts through inanimate matter.

This still doesn't explain the accuracy problems associated with pushing.

[Vortaan]

This may be part of being an Iron/Steel savant. Kelsier is probably the most skilled Pusher/Puller we see that doesn't use Hemalurgy, and it's safe to say he burned both enough to get to savant level. Maybe Coinshot Savants have instinctual ability to Push where they need to. Also, Wax seems to have a very good eye for trajectories, it's possible he overshoots and compensates for his Pushes when he fires.

[ReaderAt2046]

This still doesn't explain the accuracy problems associated with pushing.

Of course not. We know already that with sufficient practice you can vary the point on which you push at the anchor end. this is only specluation as to why you can't do the same to yourself.