UmbralRaptor changed the topic of #kspacademia to: https://gist.github.com/pdn4kd/164b9b85435d87afbec0c3a7e69d3e6d | Dogs are cats. Spiders are cat interferometers. | Космизм сегодня! | Document well, for tomorrow you may get mauled by a ネコバス. | <UmbralRaptor> egg|nomz|egg: generally if your eyes are dewing over, that's not the weather. | <ferram4> I shall beat my problems to death with an engineer. | We can haz pdf
<mofh>
egg: egg|cell|egg: finally back
* egg
chews mofh
* egg
chews the netsplits too
* egg
vomits mofh on the carpet and jumps onto the sink
<mofh>
so what happened is I decided that given that I no longer *had* to run this laptop over a random leboncoin charger connected over bodge wire given I had a proper DC-DC cable, to replace it. fib insisted on also cleaning the laptop, and then we discovered a cascading failure *had* happened, but not on the laptop: the wires on the power brick started arcing this time. So we had to find a spare of those.
<galois>
title: Shared album - Patrick N - Google Photos
<UmbralRaptop>
mofh: only qual I got on the first attempt was classical >_<
<UmbralRaptop>
!8 Am I good enough to have impostor syndrome?
<galois>
UmbralRaptop: no
* UmbralRaptop
🔪 galois
<mofh>
UmbralRaptop: E&M took me 3 tries
<mofh>
classical I barely made, apparently
<UmbralRaptop>
hrm
<egg>
what boundary conditions does the problem statement imply for E?
* egg
has forgotten everything about eleggtromagnetism, not that he ever knew more than whatever was in first year physics...
<UmbralRaptop>
We don't care about E below the plane because the mirror charge isn't real
<UmbralRaptop>
So boundary would typically be z ≥ 0
<egg>
oh right the mirror charge thing is a thing
<egg>
how the fuck did I forget so much stuff
<egg>
how the fuck was it so long ago, too
<UmbralRaptop>
hahahah *sob*
<egg>
apparently last time I had physics lectures (as opposed to mathematical methods of physics) was physics III in late 2012
<UmbralRaptop>
literally my first semester at UMKC o_O
<egg>
(my first semester at ETHZ was autumn 2011)
<egg>
UmbralRaptop: so the mirror charge thingy tells us that this is like having two antiparallel dipoles 2d apart?
<UmbralRaptop>
yes
<egg>
hm
<egg>
UmbralRaptop: I wonder if things would look nicer if you did it in polar coordinates around the centre?
<UmbralRaptop>
So it's *just* taking the right derivatives and products
<egg>
UmbralRaptop: yeah, but as you point out that potential looks tedious to derive
<egg>
unless there's an obvious simplification...
<UmbralRaptop>
Part of the problem is dipoles being dipoles, I have that cos(θ) that is centered on each
<egg>
yeah
<egg>
but precisely, geometry might help
<egg>
the only thing there is to life etc.
<egg>
then again perhaps that's not useful here
<egg>
UmbralRaptop: wait, I have a question about what you wrote
<egg>
that θ
<egg>
it lies in the xz plane?
<UmbralRaptop>
yes
<egg>
but there's nothing xzish about the field of the individual dipole
<egg>
there's something xish
<egg>
but not xzish
<egg>
that V for an individual dipole is not symmetric in rotation around x
<egg>
that's no dipole
<UmbralRaptop>
bleh, need more y then
<egg>
UmbralRaptop: but wait; draw those cos θ on the diagram
<egg>
or r cos θ rather
<egg>
r cos θ = x, for both 1 and 2, right?
<egg>
thus cos θ = x/r
<UmbralRaptop>
yeah
<egg>
x/(r-dipole position) rather
<egg>
and we have an r squared term at the denominator, so that becomes an r cubed term but other than that we're good
<egg>
the denominators in z are thus going to be (x^2+y^2+(z-d)^2)^(3/2) and (x^2+y^2+(z+d)^2)^(3/2) I think?
<UmbralRaptop>
yep
<egg>
(not sure if that's an improvement in terms of niceness to derive)
<UmbralRaptop>
technically yes
<egg>
UmbralRaptop: you could try working in cylindrical coordinates around the z axis to make it a bit more palatable
<egg>
denominators become (r^2 + (z±d)^2)^(3/2), you get a trig function in the denomoinator and of course you need to dig up/rederive the gradient in cylindrial coordinates, but it might be marginally nicer; probably a matter of taste at that point
<egg>
s/denomoinator/numerators/
<galois>
egg meant to say: denominators become (r^2 + (z±d)^2)^(3/2), you get a trig function in the numerators and of course you need to dig up/rederive the gradient in cylindrial coordinates, but it might be marginally nicer; probably a matter of taste at that point
<egg>
UmbralRaptop: does that sort things out?
<egg>
(a brief attempt at plotting the gradient of that with mathematica yields a field that's not obviously wrong so there's that)
<galois>
title: Shared album - Patrick N - Google Photos
* UmbralRaptop
pokes the E field with a kitten
<egg>
hmm
<egg>
where did the terms with a 3/2 in the denominator go in the derivative
<egg>
did 5=3 at some point
<UmbralRaptop>
oops
<UmbralRaptop>
note to self: 5≠3
<egg>
UmbralRaptop: well
<egg>
UmbralRaptop: in characteristic other than 2, it is
<egg>
UmbralRaptop: I guess that's a reminder to try to write not necessarily well, but with distinguishable glyphs
<egg>
if 5 looks like 3, it will be equal to 3 somewhere down the page
<UmbralRaptop>
glyphs are distinguishable, though >_<
<egg>
yeah
<egg>
UmbralRaptop: it's ballpoint?
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<UmbralRaptop>
yes, why?
<UmbralRaptop>
!wpn e_14159_
* galois
gives e_14159_ a blue Debye herpolhode
<egg>
I absolutely hate writing with ballpoint pens, so looking at things written with that make me feel like it must have been uncomfortable to write; but I guess your mileage may vary
<egg>
(do use something with which writing is comfortable, whatever that is for you, because, well, algebraic manipulations tend to involve a lot of it)
e_14159 has quit [Ping timeout: 378 seconds]
* egg
pokes mofh with the dipoles
<egg>
!wpn
* galois
gives egg a 猫
* egg
stabs mofh with a 猫
<egg>
simplified kitty
<UmbralRaptop>
!choose traditional kitty | simplified kitty
<galois>
UmbralRaptop: Your options: traditional kitty , simplified kitty . My choice: traditional kitty
<e_14159_>
!wpn UmbralRaptop
* galois
gives UmbralRaptop a cathodic frustrating gonad
<UmbralRaptop>
uhm
<e_14159_>
Yes, the choice is quite interesting
<e_14159_>
(The only reason I'm currently awake is because coughing is keeping me so. I'll be off to bed again soon, perchance to sleep)
<egg>
speaking of sleep I should do that
<UmbralRaptop>
!choose sleep | don't sleep
<galois>
UmbralRaptop: Your options: sleep , don't sleep . My choice: sleep
<egg>
UmbralRaptop: does the rest of the eleggtromagnetic question sort itself out from there?
<mofh>
egg: ?
<UmbralRaptop>
well, how to write the p vector (p \hat x?)
* egg
pokes with UmbralRaptop
* egg
pokes mofh with UmbralRaptop
egg|laptop|egg has joined #kspacademia
* egg|laptop|egg
zzz
<egg|laptop|egg>
mofh: please take over the deconfusing of the raptor
egg|laptop|egg has quit [Remote host closed the connection]
* UmbralRaptop
hurt themself in their confusion!
<mofh>
egg: so I'm still confused at all of these E&M questions
<mofh>
been trying to refresh my memory but I think I might be of more use on, well, any other qual :/
<UmbralRaptop>
blarg
<UmbralRaptop>
uh, I can grab some QM questions later
<mofh>
I'l be around, reading thru my copy of Griffiths atm
* egg|cell|egg
meows at whitequark
<egg|cell|egg>
UmbralRaptor what do you mean by the vector p and why do you want to write it
<galois>
[WIKIPEDIA] Soviet space dogs#Bobik and ZIB | "During the 1950s and 1960s the Soviet space program used dogs for sub-orbital and orbital space flights to determine whether human spaceflight was feasible. In this period, the Soviet Union launched missions with passenger slots for at least 57 dogs. The number of dogs in space is smaller, as some dogs..."
<galois>
[WIKIPEDIA] Félicette | "Félicette (French pronunciation: [fe.liː.sɛt]) was the first cat launched into space, on 18 October 1963 as part of the French space program. Félicette was one of 14 female cats trained for spaceflight. The cats had electrodes implanted onto their skulls so their neurological activity could be monitored..."
<egg|laptop|egg>
> The other nine cats were decommissioned at the end of the program
<_whitenotifier-d13c>
[Principia] eggrobin opened pull request #2438: Symmetric bilinear forms on bivectors and the anticommutator form - https://git.io/Jvf6p
<galois>
title: tef ebooks on Twitter: "what i really want is to build a product out of tiny undocumented compilers written by an undergrad, powerful enough to write any code as long as it doesn't use infix notation"
<egg|laptop|egg>
O_o why does googling [blade dril] give me a result whose title starts with wint на Твитеру
<egg|laptop|egg>
(it's the right tweet, but why the ru title, when I'm using google in fr)
<egg|laptop|egg>
something something the three human languages I guess
<egg|laptop|egg>
винт
<whitequark>
"на Твитеру" isn't russian
<whitequark>
sounds like ua or be perhaps
<whitequark>
serbian?
<whitequark>
yeah, all hits i get are serbian
<egg|laptop|egg>
lol
<egg|laptop|egg>
most powerful compiler in the world, howeve,r it is so fragile as to ICE when handled by any force other than the delicate touch of reverse polish notation .
<egg|laptop|egg>
whitequark: how would you say that in ru?
<egg|laptop|egg>
whitequark: by the way FYI, ua isn't an ISO 639 code, I think you meant uk
<egg|laptop|egg>
(more confusing situations exist, e.g. SV *is* an ISO 3166 code, for a place that doesn't really speak sv, and la *is* an ISO 639, but not for a language of LA)
<egg|laptop|egg>
git commit -am "~Long Long Line~"
<_whitenotifier-d13c>
[Principia] eggrobin synchronize pull request #2438: Symmetric bilinear forms on bivectors and the anticommutator form - https://git.io/Jvf6p
<galois>
title: Symmetric bilinear forms on bivectors and the anticommutator form by eggrobin · Pull Request #2438 · mockingbirdnest/Principia · GitHub
<galois>
title: Principia/symmetric_bilinear_form_test.cpp at 81c95cc9c9850eb74ad505a8c5faac3cffe4ebff · mockingbirdnest/Principia · GitHub
<egg|laptop|egg>
wait why am I expecting the same thing on two consecutive lines
<_whitenotifier-d13c>
[Principia] eggrobin unlabeled pull request #2440: Add the word "template" in a few places - https://git.io/Jvf1n
<_whitenotifier-d13c>
[Principia] eggrobin labeled pull request #2440: Add the word "template" in a few places - https://git.io/Jvf1n
<_whitenotifier-d13c>
[Principia] eggrobin synchronize pull request #2438: Symmetric bilinear forms on bivectors and the anticommutator form - https://git.io/Jvf6p
* egg|laptop|egg
stabs mofh with NomalRaptor and NomalRaptor with a dipole
<NomalRaptor>
yeah. Or between the dipole and the ghostly (?) E field
<egg|laptop|egg>
NomalRaptor: well the E field we have, it's as real as it gets
<egg|laptop|egg>
NomalRaptor: what formulae do you know that pertain to dipoles?
<egg|laptop|egg>
(I have never interacted with dipoles in what little eleggtromagnetism I had in the physics classes I had, but I suppose you have some things, otherwise the exams wouldn't talk about dipoles)
<galois>
[WIKIPEDIA] Method of image charges#Electric dipole moments | "The method of image charges (also known as the method of images and method of mirror charges) is a basic problem-solving tool in electrostatics. The name originates from the replacement of certain elements in the original layout with imaginary charges, which replicates the boundary conditions of the..."
<NomalRaptor>
why are method of images and method of image charges separate pages?
<galois>
[WIKIPEDIA] Dipôle électrostatique#Dipôle passif | "Un dipôle électrostatique se définit par une répartition de charges électriques de somme nulle telles que le barycentre des charges positives ne coïncide pas avec celui des charges négatives. Le dipôle le plus simple est donc un couple de deux charges de signe opposé distantes d'une longueur a non nulle…"
<egg|laptop|egg>
NomalRaptor: try computing the gradient of inner product (p, E) where the dipole is, and seeing whether you get that F
<NomalRaptor>
je ne dire pas français >_>;;
<egg|laptop|egg>
NomalRaptor: you need not to say french
<egg|laptop|egg>
NomalRaptor: merely read the eggspression for F
<egg|laptop|egg>
or what I wrote in the preceding message, which is the same)