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1851: "Magnetohydrodynamics"

Posted: Fri Jun 16, 2017 8:54 am UTC
by Raidri
Image

Title text: "Magnetohydrodyanmics combines the intuitive nature of Maxwell's equations with the easy solvability of the Navier-Stokes equations. It's so straightforward physicists add "relativistic" or "quantum" just to keep it from getting boring."

My physics study days are some years behind me, but I am fairly sure that is not how I thought at the time ...
But of course the computational models (and the computing power) should have gotten some upgrades in the meantime.

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 9:11 am UTC
by markfiend
Note the typo "Magnetohydrodyanmics" in the title text

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 9:18 am UTC
by rhomboidal
My brain does the same whenever I heard the word "economics."

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 11:06 am UTC
by cellocgw
rhomboidal wrote:My brain does the same whenever I heard the word "economics."


Economics is closer to fundamentalist religion than to (white) magic.

BTW, IAAP and heck, even gravity is topologically equivalent to magic. I mean, who ever heard of two things just pulling each other together? Fucking gravity: how does it work? :P

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 11:31 am UTC
by gd1
rhomboidal wrote:My brain does the same whenever I heard the word "economics."


Let me try my hand some economics magic...

If demand (price) goes up when supply goes down, why are wages low in certain sectors and people are saying there's high demand for labor in those sectors?

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 11:36 am UTC
by Flumble
cellocgw wrote:
rhomboidal wrote:My brain does the same whenever I heard the word "economics."


Economics is closer to fundamentalist religion than to (white) magic.

BTW, IAAP and heck, even gravity is topologically equivalent to magic. I mean, who ever heard of two things just pulling each other together? Fucking gravity: how does it work? :P

The apple falls and hits Newton's head. End of story.
Elementary, my dear Watt.

Now deep-fried butter, that is magic. It defies all laws of gastronomics, ethics and whatnot.

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 12:04 pm UTC
by pkcommando
cellocgw wrote:Fucking gravity: how does it work? :P

Quite well, really.

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 2:17 pm UTC
by gcgcgcgc
Magnetohydrodynamics: The Gathering.
Now there's a card game that never caught on.

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 4:02 pm UTC
by E_H
Look for my forthcoming paper: "Magnetohydrodynamic Topological Invariants of Quantum-Relativistic Neutron-Gluon Superplasmas in Supernova / Black Hole Transitions"

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 4:20 pm UTC
by cellocgw
E_H wrote:Look for my forthcoming paper: "Magnetohydrodynamic Topological Invariants of Quantum-Relativistic Neutron-Gluon Superplasmas in Supernova / Black Hole Transitions"


You left out "... on an N-brane"

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 4:44 pm UTC
by dtobias
Any mention of Maxwell's Equations gets a silly Beatles song about a silver hammer embedded in my head (the song, not the hammer)...

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 4:55 pm UTC
by Pfhorrest
cellocgw wrote:Fucking gravity: how does it work? :P


Funny enough, as I'm sure you know, the answer is the same as for magnets: relativity. (General instead of special in this case, but still).

What really gets me is "fucking electrostatic interaction, how does that work?" Mumble mumble sea of virtual photons somethingsomething?

gd1 wrote:If demand (price) goes up when supply goes down, why are wages low in certain sectors and people are saying there's high demand for labor in those sectors?

Simple: there's high demand for low-price labor, and too low (from the buyer's point of view) a supply of it, so they're calling for more people to come do those jobs for low prices so that the supply of cheap labor goes up and its prices goes (or stays) down.

The sleight-of-hand in your magic trick is "people are saying". If wages were low and demand was high, yeah that would be something weird going on. But people are saying demand is high so that supply will increase and wages will stay low (or get lower).

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 5:32 pm UTC
by Zylon
This just raises the question why he's hearing the word "magnetohydrodynamics" so often that he needs a substitution rule for it.

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 7:32 pm UTC
by fnostro
"Hunt for Red October"...noone? really?

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 8:10 pm UTC
by qvxb
Economics 101 Principles

"...the masters make the rules for the wise men and the fools ... ." - R. Zimmerman

"Money changes everything." - C. Lauper

"And there are no truths outside the gates of Eden." - B. Dylan

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 9:04 pm UTC
by Tomasin
I think its just a contraction:

Magnetohydrodynamics

So it's Mag'ic

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 9:08 pm UTC
by RCT Bob
Navier-Stokes equations are so weird in that they are basically just Newton's Laws of motion (time derivative of momentum equals force) applied to a gas, which is among the most elementary of all mechanics, yet combined with conservation of mass and energy they're coupled non-linear partial differential equations with chaotic solutions. Adding Maxwell's equations primarily adds some extra terms, like the electromagnetic force term and some energy terms.

Aerodynamics is one of those weird places where we add more equations and more unknowns to actually solve our problems faster with numerical systems, primarily in the Reynolds-Averaged Navier-Stokes equations. I think it has a certain kind of irony to it that one of the most difficult things to solve in all of engineering physics is just basically Newton's Second Law.

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 10:44 pm UTC
by Reka
This is one of those comics where I'm kind of afraid to go look at explainxkcd's description.

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 10:49 pm UTC
by rmsgrey
rhomboidal wrote:My brain does the same whenever I heard the word "economics."


Nah, for "economics" I always hear "voodoo"...

Re: 1851: Magnetohydrodynamics

Posted: Fri Jun 16, 2017 10:57 pm UTC
by Whizbang
Who do?

Re: 1851: Magnetohydrodynamics

Posted: Sat Jun 17, 2017 7:10 am UTC
by colonel_hack
Whizbang wrote:Who do?

You do.

Re: 1851: Magnetohydrodynamics

Posted: Sat Jun 17, 2017 7:16 am UTC
by xtifr
rmsgrey wrote:Nah, for "economics" I always hear "voodoo"...


A bit offensive to the people of Haiti, innit?

Re: 1851: Magnetohydrodynamics

Posted: Sat Jun 17, 2017 9:24 am UTC
by zjxs
Any sufficiently advanced sun is indistinguishable from magic.

Re: 1851: Magnetohydrodynamics

Posted: Sat Jun 17, 2017 9:46 am UTC
by orthogon
cellocgw wrote:
E_H wrote:Look for my forthcoming paper: "Magnetohydrodynamic Topological Invariants of Quantum-Relativistic Neutron-Gluon Superplasmas in Supernova / Black Hole Transitions"


You left out "... on an N-brane"


Insane in the N-brane.

Re: 1851: Magnetohydrodynamics

Posted: Sun Jun 18, 2017 2:27 am UTC
by gd1
orthogon wrote:Insane in the N-brane.


What is the name of the next rockstar band comprised entirely of engineers and physicists?

Pfhorrest wrote:The sleight-of-hand in your magic trick is "people are saying". If wages were low and demand was high, yeah that would be something weird going on. But people are saying demand is high so that supply will increase and wages will stay low (or get lower).


Reminds me a little of diamond cartels for some reason.

Re: 1851: Magnetohydrodynamics

Posted: Mon Jun 19, 2017 10:27 am UTC
by leafar
qvxb wrote:Economics 101 Principles

"...the masters make the rules for the wise men and the fools ... ." - R. Zimmerman

"Money changes everything." - C. Lauper

"And there are no truths outside the gates of Eden." - B. Dylan


Now I am really curious why the first quote is attributed to Zimmerman and the second one to Bobby D. Is this a way to increase the authority count on this post?

Re: 1851: Magnetohydrodynamics

Posted: Mon Jun 19, 2017 1:38 pm UTC
by drachefly
Pfhorrest wrote:What really gets me is "fucking electrostatic interaction, how does that work?" Mumble mumble sea of virtual photons somethingsomething?


Photons are a thing in the interaction picture. The interaction picture is the worst way of understanding statics.

The problem is, no one really works with the Schrodinger picture in QED because it doesn't mesh well with relativity (doesn't contradict it, but doesn't make things as simple as in the interaction or Heisenberg pictures).

Re: 1851: Magnetohydrodynamics

Posted: Mon Jun 19, 2017 3:10 pm UTC
by DanD
gd1 wrote:
rhomboidal wrote:My brain does the same whenever I heard the word "economics."


Let me try my hand some economics magic...

If demand (price) goes up when supply goes down, why are wages low in certain sectors and people are saying there's high demand for labor in those sectors?


Because there are multiple interacting supply and demand curves, and the demand for, say, tomatoes, drops off sharply if the cost rises noticeably. Therefore, there is a limit to how much can be paid for people to pick tomatoes where the farmer still makes a profit. Eventually, if the supply of workers remains consistently low, the number of acres planted in tomatoes will fall to meet the demand at the new, higher price, but in areas that iterate annually, or semiannually at best, that fall off is relatively slow. Alternatively, since the demand for cheap labor is high, someone will develop a method that reduces the demand by automating part of the process, but that is a complex issue.

Re: 1851: Magnetohydrodynamics

Posted: Tue Jun 20, 2017 5:36 pm UTC
by DennyMo
fnostro wrote:"Hunt for Red October"...noone? really?

+1 for the Caterpillar!

Re: 1851: "Magnetohydrodynamics"

Posted: Sun Aug 06, 2017 11:51 am UTC
by Anonymous37
Ah, magnetohydrodynamics. The topic of those chapters of Jackson's Classical Electrodynamics that I never got around to tackling, and now I'm too afraid to try.

Re: 1851: Magnetohydrodynamics

Posted: Sun Aug 06, 2017 12:04 pm UTC
by morriswalters
markfiend wrote:Note the typo "Magnetohydrodyanmics" in the title text
Randall evidently reads the board. He's trolling his readers with this. +1