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.
Snoozee is now known as Majiir
<Majiir>
!wpn egg|work|egg
* Qboid
gives egg|work|egg a molybdenum kitten-like sonic screwdriver
<Majiir>
A screwdriver could at least be used as a weapon
<SnoopJeDi>
Yea I'm helping a friend spitball a world they're building and she has some questions about a pair of moons she wants to influence her conlang
<SnoopJeDi>
oh my, it appears maybe @excitingbooks is creating some real fake books?
* UmbralRaptor
remains annoyed at not bookmarking the Amazon link for "Solutions to Improperly Posed Problems "
Majiir is now known as Snoozee
<UmbralRaptor>
(It's actually about some subset of math.)
<SnoopJeDi>
:D
<egg|zzz|egg>
!wpn UmbralRaptor
* Qboid
gives UmbralRaptor an average ferram4
<egg|zzz|egg>
!wpn Fiora
* Qboid
gives Fiora an entangled edge
<egg|zzz|egg>
!wpn whitequark
* Qboid
gives whitequark a Kozai ?
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* egg|phone|egg
potato harvest
egg|cell|egg has joined #kspacademia
egg|phone|egg has quit [Read error: Connection reset by peer]
<egg|zzz|egg>
!wpn -add:wpn potato
<Qboid>
egg|zzz|egg: Weapon already added!
egg|zzz|egg is now known as egg
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<egg>
bofh: wait, I should add Encke to the NewtonDelambreStørmerVerletLeapfrog identifier I think
* egg
pokes e_14159 with the title of that chapter :D
<egg>
e_14159: also it's full of apostrophes in the saxon genitives as if it were english
<egg>
the ß is written ſs which sort of makes sense
<APlayer>
egg: Are you a PhD or something?
<egg>
nah, I have a master's in math, but I'm not doing a PhD
<e_14159>
egg: Old language hurts sometimes.
<APlayer>
How do you have papers on everything?
<e_14159>
Let me quote the /topic
<e_14159>
Damn, somebody deleted it...
<e_14159>
Except it still is in the gist: "<UmbralRaptor> If it's not on arXiv, it doesn't really exist."
<UmbralRaptor>
:D
<APlayer>
No. I definitely saw things that were not on arxiv, but on paid sites.
<UmbralRaptor>
sci-hub is acceptable, but will be considered only as a preprint source.
<APlayer>
preprint?
<e_14159>
Searching through scholar sometimes gives you a pdf link. If that doesn't work, a university access usually helps (luckily, we get our internet access through the university computer centre)
<egg>
sadly I don't have university access anymore
<egg>
but in the meantime, sci-hub grew so :D
<e_14159>
What kind of access does google have?
<egg>
e_14159: iirc only compsci related stuff (maybe ACM or SIAM or that kind of stuff)
<UmbralRaptor>
egg: FWIW, Fundamentals of Astrodynamics also describes that Encke's method. Nothing on terms of scholarly publications, though.
<UmbralRaptor>
APlayer: preprints are late drafts of papers that have been submitted for publication, but may not have completed the editing process. Often hosted on places like ArXiv or the author's website, and publishing terms often do not restrict their distribution.
<egg>
UmbralRaptor: there are references to Encke's work in Moebius's (yes, that Moebius) in Die Elemente der Mechanik des Himmels
<egg>
, so it got in those kinds of "fundamentals" books quickly (Encke 1838, Moebius's book 1843)
<UmbralRaptor>
That Moebius as in the artist, or the mathematician?
<e_14159>
APlayer: There might be some fields where almost everything happens on Arxiv. Mine, for example :-)
<UmbralRaptor>
APlayer: note that depending on funding, some research results are public domain. So yoinking them from the publisher's website is not illegal (that way)!
<APlayer>
e_14159: And what's your field?
<e_14159>
And, lastly, just write an email to an author - usually, they reply quickly and send you a pdf.
<e_14159>
Machine Learning/Deep Learning
<UmbralRaptor>
Yeah, lots of physics, math, astronomy, and computer science happens on ArXiv.
<APlayer>
Humm, never considered mailing authors. That sounds absolutely cool.
<UmbralRaptor>
I don't think Encke is a answering many emails.
<e_14159>
I mean, if you mail Volodymyr Mnih and ask for their nature paper, you probably will not receive an answer. But other than that...
* e_14159
works in a field where most authors are still alive
<APlayer>
Worth a shot, anyway.
<egg>
UmbralRaptor: probably have to send snail mail
<e_14159>
Or worm mail.
<UmbralRaptor>
Yeah, this is a job for the annelids, not gastropods.
<kmath>
<FakeUnicode> The infamous "Grimacing Face" is mostly negative, neutral to positive on Apple/Google. Samsung: "Dat Ass". https://t.co/hViwAX5tEq
<UmbralRaptor>
SnoopJeDi: ??? seem to cover entirely too many of my moods.
<SnoopJeDi>
!u ???
<Qboid>
U+1F62C GRIMACING FACE (?)
<Qboid>
U+1F632 ASTONISHED FACE (?)
<Qboid>
U+1F628 FEARFUL FACE (?)
<UmbralRaptor>
Also, all hail the Google blobs.
<SnoopJeDi>
? is timeless because of department Slack where it has completely replaced ?
<egg>
e_14159: he doesn't have vectors, so he has all his calculations of gravitational perturbations on three lines with x, y, z
<icefire>
they're apparently removing the google blobs and that makes me feel sad
<egg>
yeah :-/
<egg>
!wpn UmbralRaptor
* Qboid
gives UmbralRaptor a polonium anticommutator
<UmbralRaptor>
{polonium, polonium} = 0, but [polonium, polonium] ≠ 0?
<SnoopJeDi>
polonium always makes me think of Russia killing people in London and Mass Effect (in that order)
<UmbralRaptor>
!wpn egg
* Qboid
gives egg a constant
<UmbralRaptor>
A constant. c, \epsilon_0, \alpha? ¯\_(ツ)_/¯
<SnoopJeDi>
Graham's number?
<SnoopJeDi>
13?
<egg>
UmbralRaptor: the anticommutator always weirds me out
<egg>
UmbralRaptor: but, uh, the commutator with itself vanishes no matter what
<UmbralRaptor>
oops
<egg>
!wpn Fiora
* Qboid
gives Fiora a nefarious van with a register attachment
<Fiora>
wah
<Thomas>
!wpn egg
* Qboid
gives egg a hydrogen espresso
<Thomas>
...lol
* egg
wonders whether he should try out that atelier thing at some point
<egg>
Fiora: what do the bells look like once painted?
<Fiora>
reasons to play atelier: 1) you like rpgs that aren't about saving the world, 2) you like rpgs that are about girls' (not boys) coming of age stories, 3) you prefer crafting to combat, 4) you're okay with slow and calming stories rather than running away from explosions, 5) this article intrigues you https://medium.com/mammon-machine-zeal/be-gentle-if-you-know-how-to-be-gentle-57bd53ebd9f7
<egg>
Fiora: do the actual bells have clappers?
<Fiora>
the new ones don't. the old ones do ('cause they were just bells I painted). I've considered trying to add clappers to the new ones.
<Fiora>
I can't use my regular hammer though, because it's a bit too small of an object to be 3d printed well
<egg>
having bells ringing next to one's ears all the time must get annoying though
<Fiora>
that's..... actually something that surprised me, strangely
<Fiora>
i brought masking tape with me the first time i wore them at a con in case I wanted to tape the clackers off
<Fiora>
they never actually bothered me. and i am terribly neuroatypical and extremely noise-sensitive, and lack the ability to tune out noises/conversations.
<Fiora>
it remains a mystery.
<egg>
huh
<egg>
Fiora: well cows seem to not mind it either I guess
<egg>
(flying cows!)
<Fiora>
perhaps one theory is that cons are already sensory overload so bells don't make it worse
<egg>
Fiora: well it's easy to test, wear the bells on a day-to-day basis
<Fiora>
lmao
<Ellied>
cool, adding coupling capacitors and offset-adjusting potentiometers didn't fuck everything up
<Ellied>
you can never be sure about that when you're in the 10s of MHz and running solder traces less than a mm apart, hah
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<bofh>
egg: okay, seems possibly legitimate, just skimmed the reference and yeah adding Encke there seems valid.
<egg>
(mind the demented notation and weird spelling of german)
<bofh>
Okay, but it doesn't appear to be an independent discovery on the part of Encke?
<egg>
bofh: well he doesn't seem to be crediting, er, I guess Delambre
<egg>
(or Newton)
<egg>
bofh: that is, he ended up having an ODE on the perturbation term, and found this way of mechanically integrating it
<bofh>
Well Newton seems to have not publicized his discovery well, given how often it was reinvented :P
<egg>
bofh: he uses it as a device in the proof of a theorem, rather than to compute thing :D
<egg>
s/thing/things
<Qboid>
egg meant to say: bofh: he uses it as a device in the proof of a theorem, rather than to compute things :D
<bofh>
well I'm not sure running NewtonDelambreStørmerEnckeVerletLeapfrog by hand is very fun
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<egg>
so others reinvented it for the purpose of mechanical calculation (in fact Ueber die Berechnung der speciellen Stoerungen follows Ueber die mechanische Quadratur in the first of these Jahrbuecher)
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<egg>
bofh: well Encke might have done it mechanically, but Delambre certainly didn't
<egg>
and he was an astronomer, so he really integrated things
<egg>
bofh: frankly even with a mechanical calculator it must be a PITA
<bofh>
my condolences to Delambre
<bofh>
Oh, definetly.
<egg>
Størmer's work sounds awful
<bofh>
Am reminded of running RK4 and DFTs by hand, neither of which were fun in the slightest.
<egg>
(that's the thing on corpuscules chargés or whatever)
<bofh>
Yeah, auroral magnetodynamics and shit
<bofh>
(not to be confused with running DFT by hand, which I hope to never have to do, Hartree-Fock by hand was enough)
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<UmbralRaptor>
…
<UmbralRaptor>
People have run DFT by hand? o_O
<egg>
bofh: other advantage of putting Encke in that identifier (and the preceding comments), a source in German! to complement Newton's latin, Delambre and Størmer's french, and Verlet's english
<egg>
bofh: Delambre and Encke are the only ones to write in their language in that mess :D
<egg>
admittedly the Jahrbuecher are weird and hard to find
<egg>
(weird as in they're Jahrbuecher der Astronomie: mostly giant astronomical tables and then a blurb about computing perturbations that says "and we'll continue this computation in next year's edition")
<egg>
(and some more tables)
<egg>
bofh: I kid you not, in the 1837 edition the section Ueber die Berechnung der speciellen Stoerungen ends with (Die Fortsetzung folgt im nächsten Bande des Jahrbuchs.)
<egg>
and indeed it continues in the 1838 edition, and starts by referring to equation (21) from the previous edition :D
<bofh>
Oh huh, so he was.
<bofh>
LOL THAT'S AMAZING
<bofh>
I wonder if Jahrbuecher der Astronomie has been digitized... 1837 is quite old.
<egg>
bofh: it has been, those Google books links are just that
<egg>
well at least those two volumes
<bofh>
Ooh, *reads*
<SnoopJeDi>
Gutenberg is digitizing Galileo's Dialogue now, I just got a copy to help proof :D
<SnoopJeDi>
Archivists ?
<egg>
bofh: I found them because the titles of the sections were cited by Moebius (yes, that Moebius) in Die Elemente der Mechanik des Himmels
<bofh>
now I'm peeved at the time I needed something out of a 1950s math journal for a talk and that *wasn't* digitized so I had to get zeno from efnet #math to scan the fucking thing for me.
<SnoopJeDi>
so much stuff needs digitizing ð?
<egg>
bofh: the 50s are awful for that
<egg>
like, specifically the 50s and early 60s
<bofh>
why then specifically? increase in printing but too far from when cheap scanning was a thing?
<egg>
bofh: because there you have a plethora of journals so they don't get digitized (whereas 18th century proceedings of the academy of sciences of st petersburg in latin are scanned, there are only so many proceedings at the time), and it's not recent enough that it's all digital to start with
<bofh>
Ahh, so it is a relative volume issue.
<egg>
bofh: for my MSc. thesis I had no trouble digging up refs from the 19th century, I managed to find a scan of the proceedings of the academy of sciences of st petersburg with Segner's stuff (18th century), Euler's letter to Goldbach, a buch of modern papers of course, and never managed to get my eyes on a paper by Tamari (1962)
<egg>
because nobody digitized old stuff from Nieuw Arch. Wiskunde
<egg>
whereas 19th century articles in J Math. Pures Appl. are of course readily available
<egg>
or Mémoires de la Classe des Sciences de l'Académie royale de Belgique or whatever
<bofh>
Yeah, I suppose the volume of stuff from the 18th/19th century is much smaller, plus there's only a few that are notably important in any given field so far.
<egg>
or the congresses of the Association française pour l'avancement des sciences,
<egg>
fusionnée avec l'association scientifique de France (fondée par Le~Verrier en 1864) :-p
<egg>
yes I have silly things in my bibliography :D
<egg>
Emploi de l'échiquier pour la résolution de divers problèmes de probabilité is just an retired officer who does elementary mathematics and rererereinvents the Catalan numbers by using weirdly-shaped chessboards to solve probability problems
<bofh>
LOL this reminds me of the time I convinced someone to cite Legendre's "Recherches sur l'attraction des sphéroïdes homogènes" for an undergraduate PDEs project.
<bofh>
also that's pretty cool.
<bofh>
Like that's an interesting way to derive Catalan Numbers.
<egg>
bofh: might be the Catalan triangle actually (the one that Catalan has nothing to do with)
<egg>
bofh: but iirc in my video I briefly mention it (rook paths in a triangular chessboard :D)
<bofh>
oh, right.
<bofh>
I should rewatch that video, I think I missed a few details the first time I saw it (I am horrible at learning from video)
<egg>
bofh: I made that video after doing my MSc thesis, because frankly the Fibonacci numbers get all the screentime and the Catalan numbers are *everywhere* too :-p
<egg>
and yes, everyone reinvents them (or the triangles related to them)
<bofh>
So in my experience the binomial numbers (or w/e you call Pascal's Triangle) are even more common.
<egg>
yeah
<bofh>
Tho that could just be my experience.
<egg>
but everyone knows that
<egg>
whereas the Catalan numbers are kind of less known
<egg>
bofh: so Catalan proves that the Catalan numbers count the bracketings of a product, and Tamari 1962 (the elusive paper) proves that they count well-formed bracket expressions
<egg>
bofh: the bijection is not actually trivial
<bofh>
Define "well-formed"
<egg>
balanced, doesn't close unopened brackets
<bofh>
Ahh.
<egg>
bofh: I never found out who made up the name "Catalan numbers" btw
<egg>
bofh: can you find the off-by-one in equation (23) though
<bofh>
So I'm used to (23) being in terms of C_{n} on the left and C_{n-i-1} on the far right
<egg>
bofh: yeah and here X isn't indexed like C anyway
<egg>
bofh: but what happens in the sum for i = 0 :-p
<bofh>
Yeah, it's indexed slightly insanely.
<bofh>
...fuck. Yeah, that's a problem.
<egg>
bofh: the text is correct though, it says i runs from 1 to n-1
<egg>
bofh: in fact X_1 isn't something you want to touch either, he starts by defining X_2
<bofh>
I think I kind of am understanding the French now.
<bofh>
(Annoyedly I used to be able to at least read it quite well thanks to compulsory Canadian curriculum)
* egg
mildly unclear on what languages bofh understands/speaks/uses to telepathically communicate with cats
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<lamont>
egg: how fast should a 185x185 orbit get modified by principia?
<lamont>
after 30 mins (minus the launch time so closer to 20-ish mins) in orbit i’m in a 179x199 orbit now
<egg>
lamont: so that's just the osculating orbit lying to you, it should average out over an orbit
<lamont>
ah okay
<egg>
what you will see is precession, but if it's circular it will stay so
<egg>
precession you can estimate by looking up the equations for J2-induced precession on Wikipedia
<bofh>
egg: I'm from Canada, we have compulsory French education up to the end of high school.
<egg>
bofh: huh, I thought you were from DE from some reason (didn't you use to have a hostname from there or something)
<bofh>
My VPS that I'm IRCing from is in Frankfurt, yes.
<egg>
aha
tfool is now known as tfafk
<bofh>
augh accidentally got my resonant filters to self-oscillate
<lamont>
i wonder if over millions/billions of years a space faring race could start having issues with all their gravity assist maneuvers messing up the orbits of their planets…
<Iskierka>
short answer: not really
<Iskierka>
planets are big and if you're using slingshots one way you're gonna use them on the way back and approximately equal the change you did. Even if you did not, the planets interacting with each other is a far greater effect
<Iskierka>
the orbits *will* mess up over such periods, but due entirely to natural chaotic motion
<Iskierka>
(if "mess up" is taken to mean "be slightly adjusted around")
<egg>
oh I think they can actually mess up too?
<egg>
paging UmbralRaptor
<Iskierka>
I think it's probably the case that most systems that manage the few billion years to a spacefaring civ are probably metastable enough to manage a few billion more
<Iskierka>
but it probably is possible for them to suddenly hit a tipping point
<lamont>
maybe start with a solar system that doesn’t have a jupiter and is already somewhat unstable
<Iskierka>
plus they might occasionally get another star visiting. That'll be what messes up anything
<Iskierka>
... I don't think jupiter is resonant with any inner planets so isn't really stabilising it?
<Iskierka>
I vaguely recall it may have a resonance with saturn but not sure about any other outer body
<egg>
also beware the misconception about resonances, a whole lot of the time they mainly have the effect of destabilizing things
<egg>
something something Nice model
<egg>
(I feel like Fiora should make puns about the Nice model)
<Iskierka>
3:2 ratios seem to be nice and stable. 2:1 and 4:1 and such are the scary ones
<Iskierka>
The 3/2 (I think) is the one where asteroids are being sheperded by Jupiter in orbits that appear triangular when viewing all the instantaneous positions
<Iskierka>
granted that's not much of an orbit for planets
<egg>
well they are triangular, in the rotating frame
<Iskierka>
Yeah, those, and it was 3:2. Shouldn't have questioned it :p
<bofh>
so for an example, Voyager 1 gained 17km/sec from the Jupiter grav assist. In comparison, Jupiter was slowed down by 1m every 3 trillion years due to conservation of angular momentum.
<Iskierka>
and in a spacefaring society presumably whatever takes an assist out probably wants to come back as it's a transport to a mine or something, so it'll put most of that 0.33m/TYa back
<kmath>
<stephentyrone> @kittenpies3 In cases where sub-ulp accuracy is the goal, you sometimes do a lattice search on the rounded coeffici… https://t.co/YokVnpdqa0
<bofh>
Oh yuck. That stuff really is madness.
<egg>
bofh: sub-ulp is Fun
<egg>
bofh: I mean, anyone can do a faithfully rounded trig function, it's impossible to do a correctly rounded one, now the interesting part is minimizing (and estimating) the number of cases where it falls on the wrong side :D
<bofh>
<shrug> faithfully rounded AND fast is a pain in the arse since just the Taylor polynomial, even on [0,pi/2] will fail that sometimes iirc.
<bofh>
(or [-pi/4,pi/4] if you prefer that interval)
<egg>
well yes
<egg>
you have to be better than just Taylor
<egg>
but it's doable (with the usual whatever polynomials)
<egg>
(I didn't feel like copy-pasting his name, I should add a cyrillic layout for that and whitequark's cats)
<egg>
bofh: so clearly now we should acknowledge Riordan's mistake, and call them Euler-Segner numbers; which means that Shapiro's naming of the Catalan triangle makes no sense, so we should call that the Arbogast-Errera-Delannoy-Shapiro triangle
<bofh>
LOL. Clearly. But why not Arbogast-Errera-Delannoy-Euler-Segner, since Shapiro explicitly didn't want to use his own name there and instead named it after the relevant sequence? :P
<egg>
:D
<bofh>
egg: so you don't want Чебышёв polynomials technically (those minimize the L^2 norm as @stephentyrone said), you want to use those to initalize something that then computes the coefficients minimizing the L^{\infty} norm.
<egg>
yeah
<bofh>
hence my Remez Exchange comment. still can't get over how accurate of a description "works everytime, 60% of the time" is for that algo tho.
<egg>
bofh: yes also it's slooooooow
<egg>
(or at least was when phl was working on his libs)
<egg>
bofh: then again in his libs speed was probably generally shitty, he had to write a division in software because they had to be portable and SPARC
<bofh>
I thought that SPARC only lacked *integer* division.
<bofh>
And fwiw I have a software division routine and it's often as fast as idiv on x86_64 in many cases.
<bofh>
(mostly b/c idiv is slow even on Broadwell - not sure about Skylake+)
<egg>
hm, maybe it's just the integer division then, not sure
<egg>
yeah, fdivs, fdivd
<egg>
bofh: iirc he also had some fun stuff where he did his bigints (Ada has bigints at compile time, because Universal_Real and Universal_Integer) on the FPU because that was faster :D
<bofh>
<shrug> double precision multiply can be faster than mul32x32 on some shoddy systems.
* UmbralRaptor
is belatedly paged.
* egg
gives UmbralRaptor a two-ell telescope
* UmbralRaptor
focuses sunlight to set goblin metrologists on fire.
<UmbralRaptor>
egg: about planet orbits changing from gravity assists or natural perturbations?
<egg>
natural perturbations
<UmbralRaptor>
For the latter, some people have done simulations. Best guess is that there's a ~1% chance of Mercury's eccentricity getting large enough to have a catastrophic encounter with Venus in the next 5e9 years.
<egg>
yeah I recall Mercury being the silly one there
<egg>
(I mean not MERCURY6, we know that one is silly, also it moos)
<UmbralRaptor>
I want to say that there's a few orders of magnitude smaller chance of Mars getting involved and the inner system going very bad.
<UmbralRaptor>
The outer system (ignoring some icy debris) is stable.
<UmbralRaptor>
No bets on what happens after Sol enters the red giant branch.
<UmbralRaptor>
The mass loss alters orbits, though.
<UmbralRaptor>
Note eg: all those metal polluted white dwarfs.
<egg>
UmbralRaptor: well the mass loss would alter the orbits by making them wider if anything?
<UmbralRaptor>
Yeah. But possibly in a complicated way.
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<UmbralRaptor>
~30% of white dwarfs have spectra consistent with accreting asteroids/comets/planets in the past few 10s of thousands of years.
<Iskierka>
in newtonian physics it shouldn't alter orbits until the mass ejected is above the orbit in question, so it would possibly be non-linear? and relativity probably has more to say about distributed mass
<Fiora>
bofh: oh so a fun thing
<Fiora>
keep an eye out for 53-bit multiply instructions in future chips.
<UmbralRaptor>
This should be a (mostly) Newtonian regime. I suppose nonlinearities like that might do it for the thermal pulses?
<Fiora>
(you can guess why it's 53-bit)
<egg>
hah
<egg>
(@fiora)
<egg>
Fiora: why isn't that 52 though?
<Fiora>
floating point iirc has more "hidden bits" due to the guard bits? not sure why it comes out to 53
<Fiora>
but I know that e.g. the PPC750CL uses a 56x28-bit multiplier
<egg>
Fiora: well you have the implicit bit, but an integer wouldn't have that