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> … one of the other grad students just compared me to nomal O_o | <ferram4> I shall beat my problems to death with an engineer.
<egg|zzz|egg>
D: using rotating axes to express a velocity in an inertial frame D:
<rqou>
i guess???
<egg|zzz|egg>
D: Δ: Д: 刀:
<rqou>
and then the next step they do is because Rdot_{AB}R^{-1}_{AB} is skew-symmetric they undo the "hat" operator and replace it with a vector just for lulz
<rqou>
although i have no idea what it would be a vector _of_
<rqou>
but i guess it makes the "bag of numbers" smaller??? :P
<egg|zzz|egg>
that might just be the angular velocity of A wrt B multiplied by time or somesuch (back to the usual SO(3) and so(3) stuff, see that discussion last time)
<egg|zzz|egg>
they wrote that hat iirc
<rqou>
i thought the angular velocity is supposed to be v_q_a or v_q_b
<rqou>
i mean, it's called "v" after all??
<rqou>
hmm, and then the slides repeat the whole exercise again with SE(3) rather than SO(3)
<rqou>
and then all of a sudden there are circles in red and blue for some reason
<rqou>
and finally on slide 21/95 there is yet another overload of the term "adjoint" that can somehow convert between the two velocities
* egg|zzz|egg
goto zzz and leaves further egyptology to bofh
<rqou>
egg|zzz|egg: at some point i would really like if you can explain this all from scratch using tensors
<rqou>
and not whatever is happening here
<egg|zzz|egg>
I'd need some help from bofh there too, I'm not good at eggsplaining the universal property
<egg|zzz|egg>
(but there's more to this than tensors, it's full of Lie groups! you need differential geometry! :D)
<rqou>
meanwhile "machine learning people" just treat tensors as "this bag of numbers is bigger!"
<rqou>
:P
<bofh>
oh wow these slides are a mess :/
<rqou>
um, thanks?
<bofh>
like the way the material is conveyed is confusing to me, but that could just be the fact that I never understood this material well in the first place.
<rqou>
well, guess what? i don't understand it either :P :P
<rqou>
whelp, i'm going to get started on homework problem 1 because it turns out that you don't need to understand what's going on to solve that
<rqou>
you can just blindly crunch through some algebra
<rqou>
(yes, this is also a sign that the material isn't the best-designed)
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<SnoopJeDi>
bofh, even more mind-blowing to me is that ISR is probably why the US lost accelerator supremacy
<bofh>
SnoopJeDi: oh?
<SnoopJeDi>
I haven't really read into it that much, but the way my advisor tells it, nobody in power in the US gave enough credit to Carlo Rubbia's thoughts on stochastic cooling
<SnoopJeDi>
(which was first implemented at ISR)
<SnoopJeDi>
that's the first "writing on the wall" moment I'm really aware of for the US's lead in the field
<bofh>
Ahh. Yeah, that makes sense.
<bofh>
Also it's eerie how many of these $INSTITUTION loses lead in $field started out with "fairly remarkable discovery made and was never implemented due to higher-ups ignoring it"
<SnoopJeDi>
it's a rough pitch when the machines cost so much and create such bulky institutions :/
<Qboid>
SnoopJeDi: I added the explanation for this acronym.
<SnoopJeDi>
(world's first head-on pew-pew)
<bofh>
SnoopJeDi: that is true, I mean a typical particle accelerator prolly has costs *starting* in the low billions for manufacture.
<SnoopJeDi>
certainly a tip-top hadron collider, yea. finished cost of the LHC dipoles was $7B
<SnoopJeDi>
EIC is shaking out to be something like $300M I think? It's not super clear yet
<SnoopJeDi>
(and either concept relies on a lot of existing capital, since CEBAF and RHIC are already built)
* SnoopJeDi
glances at FCC field requirement
<Ellied>
does the LHC host x-ray physics experiments? my prof was talking about how x-ray physics was started by folks leeching off the x-rays from bending magnets (and later insertion devices) of machines mainly designed for high-energy experiments, and it was only much later that they finally went off and built their very own synchrotrons
<SnoopJeDi>
I don't think so Ellied but I couldn't say for sure
<SnoopJeDi>
There are a lot of dedicated synchrotrons by now, and then there's FEL sources too which are the new hotness
<SnoopJeDi>
SASE is all people want to talk about :)
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<Ellied>
FELs are great if you actually need the intensity and don't mind the low rep rate. A few people who spoke at my uni have talked about how those kinds of sources would take forever to collect any data compared to a synchrotron and would also probably blow up the sample without stupid amounts of filters in the way
<SnoopJeDi>
that's true, yea
<SnoopJeDi>
I don't think the stuff LHC is optimized for (i.e. it's all about luminosity) plays very well into x-ray needs
<Ellied>
yeah that makes sense
<Ellied>
big heavy things with not a lot of charge:mass, relatively speaking
<SnoopJeDi>
synchrotron damping definitely helps them out though
<SnoopJeDi>
...although coherent synchrotron radiation can induce instabilities so I guess it's a crapshoot
<kmath>
<gutenberg_new> New #ebook @gutenberg_org: The Genetic Effects of Radiation by Isaac Asimov and Theodosius Dobzhansky https://t.co/KekYvf4qkt
<FluffyFoxeh>
vorp
<Ellied>
god freenode/##linux is vitriolic right now
<Ellied>
came in to ask a question about syslogd (off to a bad start, I know) and it's a completely shameless nerd-slapfight feat. slurs and overt racism
<SnoopJeDi>
i-is it ever not vitriolic?
<Ellied>
I mean, I feel like it was often enough for me to get the idea that I could find answers there at some point in the past??
<awang>
SnoopJeDi: Wish I thought of that earlier... Too late now :(
<awang>
Not to mention idk what exactly I'd put in the write-up
<awang>
I didn't exactly find this in an interesting way
<SnoopJeDi>
I think there are probably plenty of people who would enjoy a simplified digest of ballistic capture along with a mission (I know I would!)
<SnoopJeDi>
But I guess the concept is a bit...mathematical in nature?
<awang>
I'll give it a shot next time
<awang>
Don't expect too much though :P
<SnoopJeDi>
:)
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<rqou>
woot i completed my problem set even though i don't understand a thing
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<egg|phone|egg>
Awang, what does it look like in the emb frame
<awang>
egg|phone|egg: idk
<awang>
Computer crashed, so can't pull it up at the moment :(
<egg|phone|egg>
Rotating frames are nice for transfers
<awang>
I'll have it in a bit
<awang>
I actually did this pretty much all in ECI and MCI
<awang>
ECI until I see something similar to the images in the paper
<awang>
MCI to fine-tune lunar apsides
<awang>
If I remember what I saw from the few times I took a look at EMB the path was really weird
<awang>
Lots of circles around the lunar orbit before intercepting the moon again
<awang>
I still need to learn how to do this properly
<awang>
Supposedly you should be able to get a 100km polar orbit for ~600 m/s
<awang>
But I ended up passing over the poles at over 2000 m/s
<awang>
I'll start KSP again after banging my head against this Principia SIGILL
<awang>
KSP doesn't like make -j 8 :(
<egg|phone|egg>
Also try ecsa or something since you're going to earth sun l1
<awang>
ECSA?
<egg|zzz|egg>
earth-centred sun aligned (couldn't come up with a decent name for that one)
<awang>
Oh, is that the bottom option?
<egg|zzz|egg>
awang: re that sigill, did you change the makefile? I still don't get how you get that while lamont's build works
<awang>
I was wondering what that was for
<awang>
egg|zzz|egg: I have changed it, but IIRC I get it even with a fresh checkout
<awang>
Hold on, let me try again
<awang>
Only difference I can think of is that lamont was building on 10.11 (I think?)
<awang>
I'm on 10.13
<awang>
Yep, SIGILL with clean git checkout
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<rqou>
egg|zzz|egg: so, i finally harassed the TA enough (and completed the problem set enough) that i vaguely understand what was happening in my robotics course
<rqou>
so now all i need is "how to think aobut this is a sane way"
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<kmath>
<astronomolly> MacFayden: what's more fun than solving the equations of hydrodynamics? Solving the equations of relativistic magne… https://t.co/9EOYg3NxI3
<SnoopJeDi>
‼fun‼
<Iskierka>
Given that atomic interactions are the electromagnetic force, aren't all hydrodynamics magnetohydrodynamics?
<SnoopJeDi>
fluids are a pretty poor model for anything atom-scale, although nuclear matter is amenable to that sort of model (a la the liquid drop model of the nucleus)
<SnoopJeDi>
(plasma vs generally-neutral matter blah blah)
<Iskierka>
but viscosity *is* fundamentally an electromagnetic effect
<rqou>
egg|nomz|egg: now that i've figured out the hieroglyphics, when might you have time to explain to me what is "actually happening" in my lecture notes i showed you?
<rqou>
because now i understand all the notation and mechanical operations
<rqou>
just not any actual idea about what is happening
<rqou>
also, thanks Qboid for just giving a plain old triangle
<rqou>
how boring
<UmbralRaptor>
hieroglyphics as in the writing system with 40+ birds?
<rqou>
hieroglyphics as in "this course abuses notation and makes egg|nomz|egg very stabbity"
<UmbralRaptor>
These are not mutually exclusive.
<bofh>
I'unno, notation with 40+ birds sounds like it'd be clearer than some things I've seen in the past.
<kmath>
<FioraAeterna> who the heck called it "replacing all existing computer arithmetic with a single universal number format" and not "e pluribus unum"
<UmbralRaptor>
egg: I thought that was a mystery cult?
<UmbralRaptor>
>_>;;
<UmbralRaptor>
Also, why do a bunch of default icons now have giant white borders?
<egg|nomz|egg>
!wpn Fiora
* Qboid
gives Fiora a venetian lavatory
<egg|nomz|egg>
!wpn UmbralRaptor
* Qboid
gives UmbralRaptor an avalanche light-emitting katana
egg|nomz|egg is now known as egg|zzz|egg
<egg|zzz|egg>
<bofh> I'unno, notation with 40+ birds sounds like it'd be clearer than some things I've seen in the past. << I want that
<UmbralRaptor>
… am I an RPG character now?
<egg|zzz|egg>
bofh: use the ox head hieroglyph as the universal quantifier, it's the right side up too
<egg|zzz|egg>
UmbralRaptor: ?
<UmbralRaptor>
egg|zzz|egg: with the light-emitting avalanche katana.
* egg|zzz|egg
doesn't get it
<bofh>
egg|zzz|egg: so a friend once (no joke) used Eye of Horus as an identifier in an intro to linalg lecture he gave.
<bofh>
something something ran out of letters.
<UmbralRaptor>
egg|zzz|egg: glowing swords, and swords with weird effects are a thing in some RPGs.
<icefire>
guess I need to make a script to convert mobile to desktop links
<egg|zzz|egg>
!u ʕಠᴥಠʔ
<Qboid>
U+0295 LATIN LETTER PHARYNGEAL VOICED FRICATIVE (ʕ)
<Qboid>
U+0CA0 KANNADA LETTER TTHA (ಠ)
<Qboid>
U+1D25 LATIN LETTER AIN (ᴥ)
<Qboid>
U+0CA0 KANNADA LETTER TTHA (ಠ)
<Qboid>
U+0294 LATIN LETTER GLOTTAL STOP (ʔ)
<bofh>
icefire: I use mobile twitter on desktop b/c it uses about 10% the RAM of full twitter IME.
<icefire>
thats fine
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<egg|zzz|egg>
icefire: yeah that converter would be a useful feature
<egg|zzz|egg>
Iskierka: maybe make kmath do that
<icefire>
well I was just going to make it a hexchat script for myself >_>
<icefire>
it would get a little spammy with kmath converting the link and printing the tweet
<egg|zzz|egg>
well it could do both in one message
* egg|zzz|egg
is getting annoyed at hexchat for having shitty input method support
* egg|zzz|egg
should go hunting for IRC clients again
<icefire>
yeah its IME support is kind of bad.
<Iskierka>
pretty sure IRC packet size is such that even with a twitter link + 280 character message + username + media link you could list the whole thing
<icefire>
I could but that doesn't mean it wouldn't be a long ugly message
<icefire>
max length in this server is 512 bytes
* egg|zzz|egg
stares at котяpics
<bofh>
I think the spec mandates 512 (or 768, not sure).
<egg|zzz|egg>
cute cat is cute
<bofh>
Mind you, that's 512 for the whole thing, incl. the "PRIVMSG #kspacademia :" bit
<Iskierka>
that would only be hittable with a 280 tweet using unicode for most or all of it
<bofh>
actually I think a 280 tweet might be able to exceed that on its own if it's entirely comprised of unicode chars that decompose to utf-8 sequences of 3 or 4 bytes.
<icefire>
sounds like a p99 imo. Don't think a lot of people will be spewing max length 日本語 tweets any time soon
<bofh>
I *believe* that 280 is still arbitrarily restricted to anything below U+1200 or something (or rather, "CJKV" counts as double, inexplicably).
<Iskierka>
bofh: it still holds that a 140 would struggle to at best :p
<icefire>
I'll cut the length down to make sure kmath doesn't upset the server though
<bofh>
icefire: ehh, it'll just get clipped.
<icefire>
well the bot framework im using actually splits it into multiple messages
<icefire>
I don't want that to happen though
<Iskierka>
will the framework let you convert into bytes that you can count the length of for truncation?
<icefire>
no the language can do that
<bofh>
icefire: I run into this issue all the time b/c of my habit of typing really long, overly verbose lines, to the point where I actually have a script that splits such messages over multiple lines. And yeah, if your bot framework does that, you *might* want to clip those then. Tho I honestly think that dumping the full tweet over two lines might still be beneficial - I know it's saved me from having to
<Iskierka>
more or less what I meant
<bofh>
actually bother clicking a good amount of the time.
<Iskierka>
hexchat does that automatically
<icefire>
what client are you using that doesn't break up those messages for you?
<bofh>
irssi requires a script to do so but the script is pretty damn trivial. :P
<icefire>
mmm
<Iskierka>
I don't know why I didn't expect the "running on FreeBSD" part
<bofh>
Also while we're on that topic, thoughts on upon paste of a link that is not twitter or youtube or w/e, that you grab the page and print whatever's in the <title></title> part of the returned html? I know other channels that have bots that do this and it does seem fairly handy, but perhaps others'd find that annoying?
<egg|zzz|egg>
we tend to like bots (#bottorture is a nice place to test them)
<kmath>
<kenklippenstein> Computer, find the most grotesque reminder possible that we live in an unmitigated dystopia https://t.co/GuIjqCwY7F
<icefire>
I don't think I want kmath printing link headers
<icefire>
it certainly wouldn't be popular in some other channels its in
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<bofh>
fair, tho I'd expect that turning parts of its capabilities on and off per-channel should be possible?
<icefire>
it's possible, I don't have a generalized framework for it. Should probably get around to that, two other plugins for the bot have their own implementations