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[EuchreJack]

Well, that was !!FUN!!

Money isn't exclusive to so-called "Capitalist" societies, and Communists need Banks too.

And money is basically an abstract for wealth.

[King Zultan]

if you understand the future

How can you understand something that hasn't happened yet?

[Scoops Novel]

My point is (for example - and wait. I'm going to say this twice. For example) it's the man with the gun that runs the show, not the guy with the money.

Banks don't have the necessary skillset for a proficient, ambitious, 2022 shadow government.

[dragdeler]

https://m.youtube.com/watch?v=1XFw1jRKRwQ

[McTraveller]

...because [[banks]] should have been able to tell he was up to no good by looking at the various transactions, and can (as well as should!) act accordingly.

No, There Be Dragons that way.  Banks should only and exclusively store money, give people that money back (possibly with interest), and make sure money is transferred between parties at their request.  Checking of "shady behavior" should be wholly the purview of law enforcement, not banks.  Giving banks the responsibility to "monitor for bad behavior" is how you get nasty systemic problems.

I'd also argue this goes for things like content moderation: as soon as you require forums to watch for Bad Stuff, things can go off the rails quickly.

[scriver]

A touch ironic that the name is now used to refer to shadowy authoritarians guiding the world toward a future for their own ends, don’t you think?

I feel like I made my "burghers literally tore society, community, and people apart for profit and we peasants had it better under kings and nobility than under them" schpiel too recently to do it again here, so I'll just say that taking the 19th century in account, no, it's really not ironic at all.

[EuchreJack]

My point is (for example - and wait. I'm going to say this twice. For example) it's the man with the gun that runs the show, not the guy with the money.

Banks don't have the necessary skillset for a proficient, ambitious, 2022 shadow government.

How many people can you control with a single firearm? Or even a single tank?
Vs.
What percentage of the World's population could you control with large sums of money?

Guns don't do crap without people holding them. And those people don't do crap without motivation. And money is a mostly universal motivator.

[King Zultan]

There's a reason people say money makes the world go round.

[hector13]

There's a reason people say money makes the world go round.

The engines are coin-operated.


Scene: Sol 3 Engine Room, a number of shadowy figures tend to various flashing displays, the sound of a large bank of engines can be heard in the background.

*engines wind down*

Secret Society Member 1: throwing down the clipboard they were reading, “Oh for fu-“

They walk over to the power display, read it for a few moments, frowning.

Secret Society Member 1: turning to the other figures in the room, “Whose turn was it to keep the meter going today?”

The sound of awkward fidgeting is heard as the other people in the room look around at each other.

SSM 1: “If they don’t own up we’ll have to do a whip round.”

The other figures all look around at SSM 2.

SSM 2: sheepishly: “Well you see, the thing is, all those investments we had to make in order to bankrupt the *engine sputters over the words, making them inaudible* corporation and bribing the various government officials to look the other way have left me a little short this week. I don’t quite have enough to cover it…”

The others all groan and complain to one another, as though this happens a lot when itms SSM 2’s turn.

SSM 1 stares at SSM 2 for a few uncomfortable moments, as SSM 2 looks at their shoes. SSM 1 sighs and digs their hand into their pockets, followed by the sound of everyone else in the room counting change.

SSM 1 grabs a nearby plastic bucket, upends a few used tissues and candy wrappers onto the floor, and walks around the room collecting change from the other members. A few hushed whispers of “you need to sort this out boss, we can’t keep doing this.” are heard as he passes by some of their more unhappy cohorts.

Finally they approach a coin slot and begin feeding coins in, until the engines fire back to life. A panel is read, and a few more coins inserted, before the bucket is placed on a counter nearby. SSM 1 approaches SSM 2, placing a hand on their shoulder. The conversation unheard over the sound of the engines, but SSM2 looks at the floor, nodding briefly, before being lead to the door by SSM 1, the door sliding noiselessly into the frame. After SSM2 passes through it slides closed. SSM 1 shakes their head, and returns to their clipboard and resumes perusing it, as the image pans away.

[McTraveller]

Calling all physicists:

Consider:

The Biot-Savart law defines how an infinitesimal magnetic field is generated by infinitesimal elements of current: the magnetic field is perpendicular to the current element that generated it and the line from the current element to the point of interest.

The Lorentz force law says the force due to a magnetic field on a line element of current is perpendicular to both the direction of current and the magnetic field.

Conservation of linear momentum says that forces between two entities acting on each other must be equal and opposite.

Now look at two small elements of current which are perpendicular to each other.  The result I get is that the force between them is not equal and opposite; a force perpendicular to one wire is parallel to the other wire.  So the forces are equal in magnitude, but their directions are perpendicular, just like the wires, not antiparallel...

My question is: Where's the missing force that conserves the linear momentum?

[Il Palazzo]

For disclosure, I flunked my physics degree twenty years ago and I've always hated magnetism.

Can you draw the basic setup in paint or smthg? I'm getting opposing torque around the midpoint on each wire, acting to align them in parallel without linear displacement. But maybe I'm thinking of some other arrangement (two infinite wires crossing like axes in a rectangular coordinate system?).

[McTraveller]

So the blue and red current elements are coincident with the x and y axes, respectively.  The component of B field generated by the blue current element at the red element is only in the positive z direction; the component of B field generated by the red current at the blue element is in the negative z direction.

Force of blue on red is: i(red) cross B(blue) is in the plus X direction (since +y cross +z = +x);
Force of red on blue is: i(blue) cross B (red) = +y (+x cross -z = +y)

So while yes, if you extend the currents out to infinite length, the red wire would have a -z torque (want to twist clockwise) and blue would have a +z torque (want to twist counterclockwise), with zero net force - but that is "in aggregate".

My question is - shouldn't conservation hold for every microscopic element individually, not just in aggregate? What's missing from the model?

[Il Palazzo]

So I'm very much not sure this is it, but it's the one coherent thought I've got. I'm thinking, since each of the two wire elements would momentarily start moving in the direction of the forces shown, then we'd have another case of moving charges that needs to be taken into account. With the red element moving along +x, and the blue one towards +y, we get the same direction of the induced magnetic field as before, but the additional Lorentz forces are now directed towards -y and -x respectively. The resultant nett force should point along a line connecting the two wires, thus conserving momentum.
I.e. the charges are not actually moving perpendicular to each other, but in parallel (unless we constrain the wires, which eliminates the issue).

This kinda relies on the new forces being of the right magnitude, though. Dunno if there's an argument that they must be so, other than actually calculating an example.

[McTraveller]

If the wires are rigid they wouldn't "move" - they would just experience a force. Think about an electric motor that you're holding tight - you feel the torque, but nothing's moving.

I was even thinking of a simpler version of this - if you change one of the current elements literally to a single point charge, then you get the "easy" Lorentz F = qv x B on the charge, which is unquestionably correct. But if the B field is created by a wire element, that force on the charge is parallel to the wire element... so what is the reaction force on the wire element? It can't be magnetic, because a magnetic force cannot be parallel to current.

If it's not magnetic, it must be an electric field... but I can't figure out how to include one in the model since the magnetic fields should be static; I can't find a dE/dt term.

I have, while trying to figure this out, learned that while momentum (and forces) is conserved in any given frame, it's not conserved across frames - forces in one frame are not necessarily equal to those in another arbitrary frame.  Sadly that doesn't help much...

EDIT: ok my searching has finally resulted in finding this, which I need to read, as it sounds similar...

EDIT-EDIT: Ah dangit, yes, the momentum stored in the fields themselves...

[Il Palazzo]

If the wires are rigid they wouldn't "move" - they would just experience a force. Think about an electric motor that you're holding tight - you feel the torque, but nothing's moving.

When they're rigid and not moving, then there's no problem as stated, as momentum is conserved. You could restate it as a violation of Newton's 3rd (i.e. where are the missing reaction forces?). But in that case, whatever is constraining the wires supplies the reaction force on each wire.

ed: reading you link now.