egg|nomz|egg 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.
<kmath>
<mountain_ghosts> pretty naïve of you not to support unicode
<bofh>
iximeow: welcome
<bofh>
!wpn iximeow
* Qboid
gives iximeow a CJKV tagged muon
<iximeow>
!wpn Qboid
* Qboid
gives Qboid a Renesas eraser
* UmbralRaptor
pokes SIMBAD with 72 stars in the derived properties.
<UmbralRaptor>
Bleah, the crossmatch page is so slow, I may as well download the catalogs and use TOPCAT.
<bofh>
SIMBAD?
<Qboid>
bofh: [SIMBAD] => Set of Identifications, Measurements, and Bibliography for Astronomical Data
<bofh>
ah.
<UmbralRaptor>
Confusingly, the acronym is not in French.
<bofh>
TOPCAT?
<Qboid>
bofh: [TOPCAT] => Tool for OPerations on Catalogues And Tables
<bofh>
oh, RIGHT.
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<SnoopJeDi>
awang, I like to include a link of some kind in the weekly email, and I offer a free drink to anyone who sends in a link that I then include
<SnoopJeDi>
trading a few bucks worth of beer/liquor for esprit de corps :)
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<SnoopJeDi>
also usually gives us a go-to conversation topic
* UmbralRaptor
🔪 MNRAS with IOP
<UmbralRaptor>
!acr -add:IOP Institute Of Physics
<Qboid>
UmbralRaptor: I added the explanation for this acronym.
<awang>
SnoopJeDi: That sounds like a good idea
<awang>
If I ever get in a position where I can do that without reprecussions, I'm stealing that idea
<SnoopJeDi>
by all means!
<SnoopJeDi>
reprecussions?
<awang>
A severe frown from a supervisor for some reason or another
<kmath>
<kbatygin> Saddened to learn that Yoshihide Kozai has passed. In his honor, the subject of today's lecture will be the Kozai-L… https://t.co/ZU9jU966Xg
<egg|work|egg>
(via UmbralRaptor)
<egg|work|egg>
UmbralRaptor: you should write that test in principia
<kmath>
<iximeow> @valarauca1 i like how you know TZ is unnecessary because UTC is the only time zone
<egg|work|egg>
(there's also UT1 elsewhere in that file)
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<egg|work|egg>
!u జ్ఞా
<Qboid>
U+0C1C TELUGU LETTER JA (జ)
<Qboid>
U+0C4D TELUGU SIGN VIRAMA (◌్)
<Qboid>
U+0C1E TELUGU LETTER NYA (ఞ)
<Qboid>
U+200C ZERO WIDTH NON-JOINER ()
<Qboid>
U+0C3E TELUGU VOWEL SIGN AA (◌ా)
<egg|work|egg>
ah yes I can confirm that attempting to paste this on my mac makes things unhappy
* egg|work|egg
wonders whether awang is still there
* awang
is definitely not still here
<egg|work|egg>
!wpn awang
* Qboid
gives awang a seismic hydrochlorofluorocarbon
<awang>
And yeah, pasting that into Chrome results in a crash
<awang>
!wpn egg|work|egg
* Qboid
gives egg|work|egg an associative explosion
<awang>
And kills spotlight
<awang>
But not my terminal
<egg|work|egg>
awang: yeah it kills everything
<egg|work|egg>
awang: cat, and then paste it
<egg|work|egg>
awang: do not mkdir it, it apparently crashloops finder persistently through reboot
<awang>
Just how many of these are people going to find
<awang>
This what, the third time someone found a Unicode character sequence that breaks {mac,i}OS?
<awang>
"abort() called; Invalid pointer dequeued from free list"
<awang>
Interesting crash message
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<egg|work|egg>
VizieR?
<egg|work|egg>
does this stand for anything or is it just the strasbourg folks being silly
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<APlayer>
Uh, guys, I might have some trouble. Running Chrome 63 on Windows 7, I am used to just rebooting my computer (without explicitly closing Chrome) and all my browsing data is restored when I open it again. However, this time (and I suspect it might be caused by some flash scripts (I think) which were running and usually do not), when I opened chrome after this procedure, it would not open. The straightforward
<APlayer>
way would be a fresh install of Chrome, however, I'd like to keep my browsing session if possible. Any advice?
<APlayer>
Would not open means some cryptic error about an invalid Side-by.Side configuration
<APlayer>
Side-by-Side*
<APlayer>
Alrighty, sorry for bothering. Chrome once more outperformed itself, a new install (without removing the broken one) fixed the error /and/ restored the browsing session.
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<egg|work|egg>
!wpn awang
* Qboid
gives awang a Norgg
<egg|work|egg>
!wpn Norgg
* Qboid
gives Norgg a cinematic hydromatic homomorphism
<awang>
Fun fact: Apparently chrome sometimes keeps running for a bit after pasting that into the search bar
<awang>
!wpn egg|work|egg
* Qboid
gives egg|work|egg a sub-calibre spider
<awang>
!wpn -add:adj calibrated
<Qboid>
awang: Adjective already added!
<awang>
!wpn -add:wpn caliper
<Qboid>
awang: Weapon added!
<awang>
!wpn -add:wpn slide rule
<Qboid>
awang: Weapon added!
<APlayer>
So, we have a Norgg weapon, but do we also have an egg weapon?
<awang>
!wpn -add:wpn egg
<Qboid>
awang: Weapon already added!
<awang>
APlayer: Yep!
* APlayer
wants to see that in action
<awang>
!wpn -stats
<Qboid>
awang: Total weapons: 887. Total adjectives: 1067. Total possible combinations: 3587280125315.
<awang>
APlayer: Might take a while :P
<egg|work|egg>
egg collector problem
<APlayer>
Chance is 1/887, so...
<awang>
Still might take a while, unless !wpn spam is alright
<egg|work|egg>
there's #bottorture if you want to spam
<APlayer>
I'd simply /query Qboid if I actually intended to do this
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<awang>
!u u+1f12f
<Qboid>
U+1F12F (🄯)
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<UmbralRaptor>
Does setting my phone to a Wi-Fi hotspot named "జ్ఞా" make me a bad person?
<UmbralRaptor>
egg: I need to block out some time for that.
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<kmath>
<mhoye> FYI: uBlock Origin includes a "resource abuse" section, to which you can add the NoCoin list available here: https://t.co/jsoXltcA2t
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<egg>
!wpn UmbralRaptor
* Qboid
gives UmbralRaptor a charm turbine
<UmbralRaptor>
The turbine rapidly decays. Perhaps a strange one would do better?
<APlayer>
Have you fed it? That might be the issue
<UmbralRaptor>
uh
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<UmbralRaptor>
;8ball Are turbines cats?
<kmath>
UmbralRaptor: Yes definitely
<APlayer>
UmbralRaptor: If it is hissing loudly, it might be malfunctioning :P
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<APlayer>
Ellied: If you have some time, do you mind explaining what an inductor is and how it works? I am somewhat confused about these
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<Ellied>
Yeah, so basically an inductor is what you get when you take a capacitor and switch all the current terms with voltage and all the voltage terms with current.
<Ellied>
An inductor stores energy in the form of a magnetic field, and is charged by getting a current going in it; when the voltage is removed, it attempts to keep the current moving by transferring energy from the field back into current.
<APlayer>
But a current is flowing electrons. How can you keep moving electrons if, say, a switch was opened (causing the initial current to cease, and the inductor to attempt to keep the current up)?
<SnoopJeDi>
APlayer, current will flow between regions of unequal potential, if it can
<Ellied>
You can think of it as a pump attached to a flywheel in the water pipe analogy. It takes sustained applied pressure (voltage) to get it going, and then exerts its own pressure after it's spinning to keep the flow rate from changing.
<SnoopJeDi>
The LC circuit is a great way to understand inductors as circuit elements
<SnoopJeDi>
But all you 'really' need to understand is that they resist changes in current (di/dt) because of Faraday's law
<Ellied>
yeah, in the LC circuit, the capacitor is kind of the equivalent of a spring in the mass-spring oscillator, and the inductor is like the mass.
<APlayer>
But consider the flow stopped because I shut a valve. How can the pump keep shoving more water (or electrons) if they have nowhere to go? It creates a voltage?
<Ellied>
yes
<Ellied>
if you give it nowhere to go, the voltage will spike way up
<SnoopJeDi>
APlayer, if you insist on the fluid analogy, then voltage is pressure
<SnoopJeDi>
(it's not a very useful analogy beyond a very coarse qualitative sense imo)
<Ellied>
it'll charge the small parasitic capacitance of the wires until the voltage gets so high that either it arcs somewhere or it forces the inductor to allow current back the other way
<SnoopJeDi>
APlayer, do you understand what *inductance* is?
<APlayer>
And, the other way, if there is no current and you try to apply one, an inductor will have a resistance?
<SnoopJeDi>
If not, you should study that for a bit before you try to get your head around inductors as circuit elements
<Ellied>
if you put a perfect zero-impedance constant voltage across an inductor, you'll get a current through it that starts at zero and increases linearly forever.
<APlayer>
I've seen a bunch of formulas on inductance, but it's not as easily "grabbable" as capacitance, it seems
<APlayer>
Can't picture what exactly happens to the electrons
<Ellied>
yeah it's kinda weird
<SnoopJeDi>
well I'm talking about inductance completely outside the context of electronics
<SnoopJeDi>
creating a current in a loop of wire by moving a permanent magnet near it, say
<SnoopJeDi>
or how a generator works
<APlayer>
I know these as effects of the Lorentz Force, if that's how you call it in English
<SnoopJeDi>
ehhh related but no not really
<Ellied>
very practically speaking, inductance is what creates sparks when you disconnect a wire carrying a lot of current. for instance, 9 volts create almost no sparks if it's really that, but a motor attached to a 9-volt battery will make sparks when you disconnect it because inductance rams the voltage up as it tries to keep the current flowing.
<APlayer>
Can I imagine it as some sort of inertia?
<Ellied>
yes
<Ellied>
it's a lot like inertia
<SnoopJeDi>
hence the analogy to the spring-mass system
<APlayer>
Well, a spring-mass analogy could also be drawn to a capacitor, haha
<SnoopJeDi>
not by itself
<SnoopJeDi>
both are required to properly form the analogy, although you can soooorta shoehorn some damped arguments with a single element
<APlayer>
Well, you "shove" electrons into the metal (or whatever) and when you release your "force", they "spring" back
<SnoopJeDi>
yea, that's all way too hand-wavy
<SnoopJeDi>
if there's a single piece of practical knowledge to know APlayer it's v = L * di/dt
<Ellied>
wire-coil inductors generally have a lot of parasitic capacitance between the windings, so they can often form pretty good resonators on their own. That's most of how a Tesla coil works.
<SnoopJeDi>
i.e. the inductance L is how much voltage (v) comes about when change in current (di/dt) arises
<APlayer>
Well, formulas are important for quantifying things, but I currently (no pun intended) try to intuitively understand what's going on
<SnoopJeDi>
that's what such simple formulae are for, but you have to *translate* them
<SnoopJeDi>
inductance is a proportionality constant that tells us how much a circuit element responds to changes in current
<SnoopJeDi>
(viewed from a strictly electronic point of view, that is)
<SnoopJeDi>
if you really want to think about the microphysics of the individual electrons, you need to think about the electrons interacting with their partners in the "next coil over," like in a transformer
<SnoopJeDi>
that's a real pain in the ass, which is...why it's a really bad way to try and understand it
<SnoopJeDi>
but if you think about an incompressible fluid, if you very rapidly increase the rate of flow at one end of a pipe, there will be a pretty significant pressure build-up. If you increase the rate of flow gradually, there's less resistance to this change
<APlayer>
That's inertia, isn't it?
<SnoopJeDi>
you're mixing your analogies
<SnoopJeDi>
the inertia analogy is best understood if you look at F = m * dv/dt
<APlayer>
No, I mean the actual physical cause for the pressure build-up in an incompressible fluid is inertia, isn't it?
<SnoopJeDi>
The term m plays exactly the same proportionality role as the term L in the above formula (although the causality is a little mixed up because forces cause acceleration and not the other way around)
<SnoopJeDi>
APlayer, the physical reason is because you put more stuff in the same volume
<SnoopJeDi>
fluids don't equalize instantaneously
<SnoopJeDi>
(and neither do electrons)
<APlayer>
Uh, okay
<APlayer>
I never wondered why that is so, though
<APlayer>
Now I do, haha
<SnoopJeDi>
why it's not instantaneous, you mean?
<APlayer>
Yeah. I'd guess it is inertia, but I also know pressure propagates at the speed of sound, and the speed of sound depends on more things than inertia
<APlayer>
So it can't be "just" inertia
<SnoopJeDi>
yea, inertia certainly has something to do with it, but it's not the direct cause
<SnoopJeDi>
inertia influences how fast pile-up would happen, if you want to think about it that way
<APlayer>
pile-up?
<SnoopJeDi>
anyway, the fact that the rate of change (di/dt) influences the response means that inductors let slowly-varying signals through without much in the way of resistance
<SnoopJeDi>
(and capacitors do just the opposite)
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<UmbralRaptor>
VASIMR?
<SnoopJeDi>
huh, apparently the word for that effect is "inertance", TIL
<SnoopJeDi>
don't get too hung up on the analogy if you can help it APlayer
<UmbralRaptor>
Water analogies get iffy once magnetic fields are involved.
<SnoopJeDi>
it can be helpful, but it's no substitute for looking at an (ideal) inductor as a bunch of rings near each other obeying Faraday's law
<Ellied>
Step 1: RF magic. Step 2: Heavy gas. 3: ??????? mumble mumble something about helicons 4. Δv
<APlayer>
SnoopJeDi: Well, currently my "best guess analogy" is inertia
<SnoopJeDi>
inductors *do* act a little like inertial mass, but inertia has nothing to do with why
<UmbralRaptor>
Or to more closely follow the actual acronym: VAporware Solution Inefficient Magnetoplasma Rocket
<APlayer>
This apparently works to predict the effect, but not quite to understand it
<UmbralRaptor>
APlayer: ultimately, things like ∇xE = -∂B/∂t
<SnoopJeDi>
^
<SnoopJeDi>
you don't really *need* the math, though
<APlayer>
Alrighty, let's pretend I know what this means and continue with the next step
<SnoopJeDi>
If you accept on faith that things with this property "inductance" generate voltage when exposed to changes in magnetic flux, that's all that's necessary
<APlayer>
I do accept it, but of course I want to understand why
<SnoopJeDi>
(and in fact, this is precisely what Michael Faraday did: his notebooks contain no formulae AFAIK)
<SnoopJeDi>
dude didn't know calculus ¯\_(ツ)_/¯
<UmbralRaptor>
Professorships were much easier to get 200 years ago. >_>;;
<SnoopJeDi>
APlayer, perhaps you'd like the proof offered on the wikipedia page for Faraday's Law, which relates the generated EMF to the Lorentz force law. The calculus bits are a little convoluted, but it's another way to look at it
<SnoopJeDi>
...and also it requires you to take Maxwell's equations as a starting point so heh.
<egg>
!wpn UmbralRaptor
* Qboid
gives UmbralRaptor a strict archive
<SnoopJeDi>
You gotta pick a point where you don't want to open any more black boxes, or you end up in string theory at some point and that's a deep fate :)
<SnoopJeDi>
(or worse: set theory)
<SnoopJeDi>
egg, is that like arxiv with stricter review?
<Ellied>
(apologies for those of you who saw that display in #bottorture, by the way. >_> )
<UmbralRaptor>
Pre publication, publication, *and* post publication review.
<APlayer>
UmbralRaptor: Biannual peer-viewing?
<UmbralRaptor>
Something like that.
<APlayer>
Alright, thank you SnoopJeDi and Ellied for explaining it to me, I guess I'll stick with the inertia analogy until I am ready to actually understand what's going on
<APlayer>
Will also play around with falstad or so to try to understand inductors from the EE point of view
<SnoopJeDi>
You'll cause yourself quite a lot fewer headaches if you abandon the analogy :)
<SnoopJeDi>
It's useful, but at some point you're basically trying to wrap the real world's physics around the way you *want* to understand it, which is...problematic.
<SnoopJeDi>
(file under: Herr Planck)
<APlayer>
I.e. just say that all changes in current are resisted without any explanation?
<SnoopJeDi>
no...the explanation is Faraday's law
<APlayer>
Alright
<SnoopJeDi>
Which is not a huge thing to accept on faith, it's *easily* tested as an empirical law
<SnoopJeDi>
one of the easiest physics demos to run in terms of how impressive it looks, too
<SnoopJeDi>
APlayer, that's Faraday's law yep (the negative sign expresses the direction of the potential, and is due to Lenz, so we frequently call it Lenz's law)
<SnoopJeDi>
(Faraday explained only that an emf was generated AFAIK)
<SnoopJeDi>
and as far as understanding inductors, just know that inductance tells us what the response to di/dt is
<APlayer>
So... I was aware of this braking effect, but I never knew it can stop a pendulum just like that
<APlayer>
I also was aware of thoughts to exploit the reverse effect to generate electricity from car brakes, but always assumed the generated amount would be minuscle
<APlayer>
Don't think so anymore
<APlayer>
Alright, thank you once more, and I am off for today
<APlayer>
See you tomorrow, though!
<SnoopJeDi>
Yep, regenerative braking is quite good actually.
<SnoopJeDi>
Faraday's law with a bicycle drive is also a beloved demo here, we leave ours out in the lobby for any visitors
<kmath>
<tamuphysicsfest> Do you know how much power it actually takes to light a lightbulb? more about cool physics demos:… https://t.co/leSnytQIDn
<APlayer>
Ah
<APlayer>
Got it
<SnoopJeDi>
Also a really cool demonstration of exactly how much energy (99%+) is wasted with incandescent bulbs
<SnoopJeDi>
if you crank it up and turn on the CFL it will wind down slowly, but if you click on the incandescent it brakes *incredibly* quickly and loudly because of the energy required by the bulb
<APlayer>
Joung me was wondering if you could power a light bulb off a PV cell that generated from a light bulb
<SnoopJeDi>
I had the same thoughts as a kid :)
<bofh>
Likewise. I'm pretty sure it's a common one.
<kmath>
YouTube - Kinect Star Wars "I'm Han Solo" Dancing
<APlayer>
Anyway, I am off for real now
<APlayer>
Many thanks for lots of new thought material, will be back tomorrow. See you!
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<SnoopJeDi>
bofh, it breaks my heart how easily people look down their noses at those who struggle with perpetual energy etc.
<SnoopJeDi>
like yea those people are *super* wrong but we also as a rule play directly into the myth of the ivory tower and make it real :(
<bofh>
SnoopJeDi: like this is a thing that I find is a perfect starting point for explaining basic thermodynamics, which honestly can be done at a level that is understandable by educated laypeople.
<SnoopJeDi>
Yea!
<SnoopJeDi>
"Ooh, that's an interesting thought! But, let's introduce a little inefficiency in here because [reality] and aw shucks, no good. TANSTAAFL"
<SnoopJeDi>
and then that opens a lot of fruitful ground for talking about how to minimize inefficiency or even how to talk about theoretical maximum efficiencies (the fact that the Carnot limit is not universally known is an educational crime imo)
<egg>
!wpn bofh
* Qboid
gives bofh a subnormal equality
<bofh>
SnoopJeDi: yep, indeed!
<bofh>
!wpn egg
* Qboid
gives egg an iodine ristretto
<egg>
hm
<egg>
should I drink it
<SnoopJeDi>
;8ball
<SnoopJeDi>
oh huh didn't realize that wouldn't work without a question
* SnoopJeDi
is rapidly turning into one of *those* rat people
<egg|phone|egg>
Bofh: isn't that [mju] in en though
<bofh>
egg|phone|egg: yase, but what? :P
<egg|phone|egg>
[my]
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* UmbralRaptor
🔪 buses. Specifically ones not running past 20:10 meaning that it makes sense to take one home, then drive to a bar right next to campus just to hang out with other students.
<soundnfury>
buses that haven't run for seven and a bit years?
<soundnfury>
oh wait, there's a :
<soundnfury>
!wpn UmbralRaptor
* Qboid
gives UmbralRaptor a gatling Hodge-Arakelov checker
<SnoopJeDi>
hehe, a gatling checker
<SnoopJeDi>
I have a mental image of someone wielding such a thing on their todo list
<UmbralRaptor>
soundnfury: I explicitly included a ":" to prevent that. =S
<soundnfury>
UmbralRaptor: :)
<UmbralRaptor>
SnoopJeDi: capable of filing over 3000 bug reports per minute!
<soundnfury>
I was imagining it was the eBPF verifier after someone made it threadsafe/re-entrant
<soundnfury>
but that's probably because I've been working on the verifier all day
<SnoopJeDi>
UmbralRaptor, probably easier to just mark the software that works as intended
<SnoopJeDi>
aaaand done
<UmbralRaptor>
SnoopJeDi: Yes, but _gatling_
<soundnfury>
SnoopJeDi: earlier today I described a piece of code as being "Broken as designed".