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dmckee
dmckee
1:30 AM
@Giskard42 No references, but if the drift speed of electrons in the post-arc field exceeds the thermal velocities in the post-arc gas then you would expect some long-lived residual ionization, no?
And for strongish fields and low-density gases you would expect quite substantial drift speeds.
Old paper that might cast some light on the matter: lartpc-docdb.fnal.gov/0005/000532/001/swan_pps_83_659_64.pdf
Show drift speeds near 1000 m/s even in liquid argon.
 
nitsua60
nitsua60
2:33 AM
@JakeRose plus anyone with 10K reputation or more, for many relevant purposes.
 
vzn
vzn
3:18 AM
@JakeRose are you studying physics? this one just popped up, the author has been the topic of past discussions in here, writes in the theme/ spirit of other top popsci physics books eg woit, & she has a free/ popular blog
 
Giskard42
Giskard42
3:39 AM
@dmckee That paper is awesome, thanks a lot! Looks like I've got some reading to do on electron drift...
Hahaha I just realized that I actually have video of this phenomenon occurring through an unrelated experiment
Reviewing the footage, the arc does indeed stay struck - once the plasma channel forms it remains, at least with whatever gas I was using at the time. Neat!
 
 
1 hour later…
bolbteppa
bolbteppa
5:10 AM
@vzn Lisi is one of the stars of that book, my god that is unbelievable
Obligatory:
@vzn Socrates corrupting the youth realms :p
 
vzn
vzn
5:30 AM
@bolbteppa !?! lol seriously doubt that o_O
 
Dawood ibn Kareem
Dawood ibn Kareem
5:55 AM
That's pretty much the politest thing I've ever seen from Luboš.
(Oh, except for the answer to my stack exchange question of course)
 
bolbteppa
bolbteppa
6:16 AM
You take what you can get :p
 
Secret
Secret
7:03 AM
 
Slereah
Slereah
7:22 AM
Morning
 
Sir Cumference
Sir Cumference
8:21 AM
Does supernovae and other space stuff count as nature?
 
Slereah
Slereah
no, supernovas are manmade
 
Mikhail
Mikhail
you're thinking of pulsars, which have been known for some time to be extraterrestrial beacons
 
Slereah
Slereah
superovas are alien bombs
obviously
 
Mikhail
Mikhail
dude, supernovas are just a conspiracy theory
 
ACuriousMind
ACuriousMind
9:08 AM
@SirCumference What do you mean by that? What's it relevant for?
 
djsmiley2k
djsmiley2k
It's 'natural', does that mean it's nature?
 
ACuriousMind
ACuriousMind
I mean, some people use "Nature" to mean biological nature, i.e. animals and plants, but others don't. So we need to know the intent behind the question to possibly answer it
 
djsmiley2k
djsmiley2k
9:39 AM
:)
 
Sir Cumference
Sir Cumference
10:05 AM
@ACuriousMind Just something that popped into my head while I was trying to sleep
 
 
1 hour later…
Slereah
Slereah
11:28 AM
@SirCumference More of a question for the philosophy SE
 
ACuriousMind
ACuriousMind
11:58 AM
So it's like a real life integer overflow? — htmlcoderexe 42 secs ago
I guess that's one way of looking at negative temperature :D
 
Secret
Secret
12:10 PM
[Random]
what is reality if it is not a simulation
Green route minibuses: Well defined and fixed routes with stops
Red route minibuses: Only the endpoints, route can vary but those who have tried it couple of times, they will find a usual route, thus route infomation is concealed from outsiders
Abstract the above observation further:
Let S be a configuration space
1. There are paths that are fixed and well defined
2. There are paths that are realist, except unknowable until it is tried. Even then, there is nonzero chance the paths are slightly different each time, as if it is an ensemble
Hong Kong however does not have a "QFT minibus" though, thus there is no such paths that are undetermined until it is invoked
... I wonder if I can generalise this idea chain further...
(I am looking for a "gray path", a path which its configuration is undeterminable, except that it connects two fixed endpoints)
How far can I push my brain to ponder about the unhuman and the unknown unknown. Ugh, I need fresh ideas, this human brain is too limiting!
 
 
1 hour later…
Sid
Sid
1:19 PM
Hey, @Balarka You there? I am kinda interested to know your opinions on India's fight of Terrorism
 
 
3 hours later…
enumaris
enumaris
3:59 PM
weez
 
Future Historian
Future Historian
So.....
Question: which is a more plausible concept?
This? ^
Or a creature that is 6 to 8 metres long, 1.5 metres in diameter, has eight jaws + four extra jaws that serve as tentacle-arms with hands and fingers in the tentacle-arm-jaws + spore sacs all over its body and has two pairs of eyes for visible AND infrared?
Oh and the species in the image above has similar eye function, is 1.5 metres tall and 1.2 metres long, has eight jaws, a spore release mechanism in its tail, spore sacs to store the spores, pretty strong/dense bones or muscles, and the one thing they both have in common is their life cycle being similar to that of a jellyfish.
And yes, I know, this is the Physics SE, not the Biology or Worldbuilding SE, but Worldbuilding SE is quiet and the Biology SE chat is very...inactive + they do not allow speculative questions like these.
So.....if we were to discover an intelligent, STL capable interstellar species, how would we expect them to look like?
In real life?
 
enumaris
enumaris
4:18 PM
I can't view images unfortunately =/
But I don't think there's any real expectations on how "interstellar species" should look
we have a sample size of 0 in that department
Since we ourselves are not even interstellar...nor have we discovered any interstellar species to date
 
Future Historian
Future Historian
Well, the thing is...how is it going to manipulate tools? How is it going to build spacecraft capable of traversing through the interstellar void for centuries or decades if they have nothing resembling appendages? How is it going to be able to get into space if every kg of mass counts up there?
And how is it going to communicate?
And why does it begin to develop civilisation and interstellar spacecraft in the first place?
 
enumaris
enumaris
yeah, as far as our own experiences go, communication and opposable thumbs to manipulate tools is essential
as well as an enlarged brain and higher brain mass - body mass ratio
longer gestation period...and much longer "child" phase
 
Future Historian
Future Historian
True.
Then again, this species (either version) does have one common feature short of radical life extension.
They can spam more of themselves AND have a somewhat decent lifespan.
Too bad that prior to becoming a civilisation, they would normally get eaten by huge predators on Kepler 442b.
Though they are pretty much almost extinct by the time they leave their home system.
@enumaris? So, which is more likely to evolve to become interstellar of the two proposed versions?
And NOTE: The latter version also has opposable thumbs, they just happen to be part of the tentacle-arm-jaws.
 
enumaris
enumaris
no idea...
 
Future Historian
Future Historian
Fair enough.
 
enumaris
enumaris
4:31 PM
I don't think there's a way to really specify probabilities in this case...
the larger the animal is, the more resources it probably needs to get to sustain itself
so maybe there's some bias towards smaller species...? But then again, Earth used to be ruled by Dinosaurs so...who knows
 
Future Historian
Future Historian
Except the dinosaurs had more oxygen to worry about.
By comparison, this species has a 1.28 Earth gee environment to deal with.
As in: if there is a higher O2 concentration there than on Earth, the higher gravity makes it worse.
Right?
 
enumaris
enumaris
there is the volume:surface area argument I guess
a larger species' volume and therefore weight grows by size^3 while it's bone's surface area and therefore (kinda) strength grows by size^2
so there's some maximum size...
 
Future Historian
Future Historian
So, the original version makes more sense for technological civilisation?
Since...in space, every kg of mass counts?
Because assuming it has a body density akin to water....
The latter version would have a mass of 14 tonnes and a weight of 18 tonnes on its planet.
 
ACuriousMind
ACuriousMind
@FutureHistorian I'm not sure this approach is useful. If this species happens to evolve with enough intelligence to create technology, then it's not going to not do it because a hypothetical different specific that doesn't exist would be better suited to use said technology.
 
enumaris
enumaris
There's just no good way to put probabilities on it imo
 
Future Historian
Future Historian
4:38 PM
Kepler-442b
Kepler-442b (also known by its Kepler Object of Interest designation KOI-4742.01) is a confirmed near-Earth-sized exoplanet, likely rocky, orbiting within the habitable zone of the K-type main-sequence star Kepler-442, about 1,120 light-years (342 parsecs, or nearly 1.0553×1016 km) from Earth in the constellation Lyra. The planet was discovered by NASA's Kepler spacecraft using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. NASA announced the confirmation of the exoplanet on 6 January 2015. == Characteristics == === M...
 
enumaris
enumaris
like what's the probability that humans evolved? Well it happened...so...1? Or...how do you interpret this kind of probability...
 
Future Historian
Future Historian
This is the home planet.
 
ACuriousMind
ACuriousMind
You're approaching this like a designer, thinking about what feature you might want in a spacefaring creature. But that's not how evolution works. Evolution is blind and driven by constraints entirely different than "should be able to do well as an astronaut".
 
Future Historian
Future Historian
True.
The question is...would four jaws serving as tentacle-arms with opposable thumbs REALLY be that plausible?
In addition to the eight jaws it already has?
 
enumaris
enumaris
well, I dunno any animals with more than 1 jaw
that's all I can say for that question
lol
 
Future Historian
Future Historian
4:40 PM
Do humans not have two jaws?
As in: upper and lower jaw?
 
enumaris
enumaris
o.o
 
Future Historian
Future Historian
Just imagine four outer jaws and four inner jaws for grabbing small prey (think mice) and eating respectively.
 
enumaris
enumaris
afaik, the "jaw" is just the lower portion...at least colloquially...
 
Future Historian
Future Historian
And then in the latter version, picture four extra jaws serving as tentacle-arms with opposable thumbs.
 
ACuriousMind
ACuriousMind
@FutureHistorian How are we to say what's plausible? Have you seen some of the absurd-looking creatures that walk, swim or crawl around here on earth already?
 
enumaris
enumaris
4:41 PM
I don't know if the biological definition is different
 
Future Historian
Future Historian
Because I want to know what features could a species have if it is to develop technological capabilities, especially STL interstellar travel?
How is it going to communicate? Make tools? Observe its surroundings? Etc.?
 
ACuriousMind
ACuriousMind
The result of evolution is just "whatever works", regardless of what we deem plausible. Unless you plan to give a detailed evolutionary history on your aliens, I don't see how anyone would even be tempted to judge "plausibility"
 
Future Historian
Future Historian
Plus, why does it become a civilisation in the first place?
Actually, I kind of am.
So, yes. I may do this evolutionary history as a side thing to the main content (basically Earth getting attacked by either version of these bastards).
 
ACuriousMind
ACuriousMind
So, can you give such a history and "plausibility" explanation for humans? Because then you can just pick specific points in your exposition of humans and imagine how they could have gone differently
 
Future Historian
Future Historian
So....depending on either version, how did they go from a bunch of regular ET animals to an STL technological civilisation?
Well, actually.....I kind of can.
Think about it. Australopithecus did not leave the trees and evolve into Homo Sapiens Sapiens for no reason.
Basically, they were some type of primate that used to live in the forests in Ethiopia, they dried out, and had to start walking on two legs and get smart just to survive.
Over time, as humans spread into the rest of the world, we had to adapt to the conditions elsewhere on the planet, and as various other hominids started to become extinct, Homo Sapiens Sapiens soon became the dominant hominid species of Earth.
 
ACuriousMind
ACuriousMind
4:46 PM
@FutureHistorian Well...kinda by definition, they indeed did so without reason. Again, evolution is blind and not purposeful. They didn't "get smart" in order to survive, those that didn't get smart simply died out. There is no particular reason we were lucky to get the "get smart" mutation in time.
 
Future Historian
Future Historian
And...well, the rest, as they say, is history.
Or rather...pre-history.
Get it?
drums play in the background
 
enumaris
enumaris
get smart
Get Smart
Get Smart is an American comedy television series that satirizes the secret agent genre that was popular at the time. It was created by Mel Brooks with Buck Henry and had its television premiere on NBC on September 18, 1965. The show stars Don Adams (who also worked as a director on the series) as agent Maxwell Smart, a.k.a. Agent 86, Barbara Feldon as Agent 99, and Edward Platt as Thaddeus, the Chief. Henry said that they created the show at the request of Daniel Melnick to capitalize on "the two biggest things in the entertainment world today": James Bond and Inspector Clouseau. Brooks said:...
 
Future Historian
Future Historian
@ACuriousMind. Actually, humans have always been a rather curious species. We always need to ensure that there are more mates in order to transfer our genetics, and teaching useful skills to our children, in addition to passing on genetics, is kind of a necessity when you need to work in groups.
Especially when food is scarce and you cannot survive on your own.
That and humans became curious about their environment over time.
Then again, humans are not the only creatures capable of toolmaking.
Our primate cousins also make tools.
And dolphins are very smart, they just cannot make tools underwater, since there is no practical way of doing so short of hydrothermal vents.
But even then, technological capacity is limited underwater.
 
ACuriousMind
ACuriousMind
I'm not sure what point you are trying to make at this point, I'm afraid
 
enumaris
enumaris
just make whatever species is cooler
 
ACuriousMind
ACuriousMind
4:51 PM
@enumaris A time-honored tradition in SciFi :)
 
enumaris
enumaris
ain't nobody gonna be like "dam, this author is crazy, his species has 8 jaws! Is he insane? 4 jaws would be much more plausible!"
o.o
16 fingers? That's 3% less likely than 14 fingers. Therefore this book is crap. - said nobody ever.
 
Future Historian
Future Historian
Actually....
I think I know what to do.
>:)
The snake-like version could be more of an ancestor to the one in the image above.
 
enumaris
enumaris
sounds good
 
ACuriousMind
ACuriousMind
@enumaris Well, it depends - suspension of disbelief is a curious thing, and sometimes minor implausibilities can be the straw that broke the camel's back
 
Future Historian
Future Historian
Either that or they both evolve at the same time from a common ancestor.
If you ever played Stellaris and had that syncretic evolution civic in the game, this is a similar thing.
 
ACuriousMind
ACuriousMind
4:57 PM
These implausibilities are then not the root cause of the problem, but they're what people latch on to.
 
Future Historian
Future Historian
So, what if they both exist?
They are both intelligent, and two possibilities go from here: either they coexist in the same civilisation OR one becomes extinct and the other becomes the technological civilisation that would later attack Earth in the Visitor series.
 
enumaris
enumaris
@ACuriousMind well yeah, but my point is only nobody is doing a "plausibility factor" analysis on these things...more like just a general feeling
hence the 4 jaws vs 8 jaws
or 16 fingers vs 14 fingers
 
Future Historian
Future Historian
@enumaris. Correction: eight jaws vs twelve jaws.
Four of those twelve jaws serve as tentacle-arms with opposable thumbs.
 
enumaris
enumaris
right...
 
ACuriousMind
ACuriousMind
lol
 
Future Historian
Future Historian
5:00 PM
Anyway, I am going to use both concepts as separate species with a common ancestor.
After that, I either kill one off into the fossil record or have both coexist in the same world as a civilisation (or civilisations, depending on how things go).
 
enumaris
enumaris
sounds good
 
enumaris
enumaris
5:55 PM
0
Q: When plane crashes

QuantumCasanovaCould it be true that when the plane is falling to crash, one should start to jump. If the moment the plane crashes, you are in the air then, you are not affected by the momentum. That is very unlikely to happen. Is it true or what do you suggest to do?

newtonian-mechanics classical-mechanics aerodynamics aircraft
O___O
 
CooperCape
CooperCape
To be fair I remember a time when I was convinced jumping in a falling lift would mean you survived and why didn't those fools jump anyways.
 
enumaris
enumaris
hmmm
is this a common thing...
 
Sid
Sid
I found out the hardest task in the world: "Making round chapatis"
 
enumaris
enumaris
what's a chapatis
 
Sid
Sid
 
enumaris
enumaris
6:08 PM
ah...
how is it different than a nan?
naan?
 
Sid
Sid
this link might help you
 
dmckee
dmckee
@CooperCape Even for cases where you might make a difference (relatively low speed fall) how will you know when to jump? You need timing precision on order of $10\,\mathrm{ms}$ or better...
 
Sid
Sid
@dmckee Trust God. :P
 
dmckee
dmckee
Might be better to use the Schwartz.
 
CooperCape
CooperCape
C'mon tho who doesn't have 10ms precision.
Nubs
 
Abcd
Abcd
6:12 PM
How to prove the condition of a wheatstone bridge for capacitors?
 
enumaris
enumaris
I quite like naan
and spicy indian curry is pretty good...but I'm apparently allergic to some ingredient in Indian cooking cus Indian food always upsets my stomach lol
 
Sid
Sid
@enumaris Yeah. Same. Restaurant food tends to not go down very well with my body either.
@Abcd Does simple charge distribution and KVL not work?
 
enumaris
enumaris
yeah...O.O
 
Abcd
Abcd
@Sid never mind. I proved it myself. (w/out KVL)
 
dmckee
dmckee
6:39 PM
Curries are a little time consuming but not at all difficult. Well, tuning the spices is an art, but there are a lot of good recipes out there to start from.
Making your own would allow you to know what ingredients are present so that you can find the offending substance and banish it from your kitchen posthaste.
 
enumaris
enumaris
hmmm sounds like a plan
but also means I have to do it by trial and error lol
 
dmckee
dmckee
Well, you probably know of some spices which you are OK with: cumin, ginger, turmeric and all usually present. How are you with those?
 
enumaris
enumaris
I'm good with cumin and ginger I think
turmeric I dunno
it's not an exact science...and the response is delayed obviously. But it just seems like I eat indian food -> my stomach becomes upset
 
Jake Rose
Jake Rose
7:14 PM
Could somebody explain why $P=G\omega$
Where P = power
G= torque and $\omega$ is angular velocity
Because from a vector standpoint I dont understand it

$P=rxF\omega$
$=vxF$
Which isnt equal to F dot v
 
Joe Stavitsky
Joe Stavitsky
What is the physical interpretation of saying that a line integral can have a different value depending on the direction it is evaluated in?
 
Jake Rose
Jake Rose
@JoeStavitsky Vector fields can have different values in different directions thus it is certainly possible to get different values
E.g. line integral upwards in a gravitational field is different to going downwards
 
Joe Stavitsky
Joe Stavitsky
@JakeRose ty
 
Jake Rose
Jake Rose
welcs
 
enumaris
enumaris
7:54 PM
@JakeRose be careful equating $v=\omega r$. Remember that the velocity is at right angles to $r$.
Go back and check which quantities are you using the magnitude of and which quantities are you treating as vectors
 
CooperCape
CooperCape
8:07 PM
Glad my phone is blocking wolfram alpha due to the fact the server might be pretending to be wolfram alpha.
Good one.
 
enumaris
enumaris
sounds legit
 
CooperCape
CooperCape
And so is my laptop.
Prolly my wifi ugh.
Do I look like I do my own integrals goddamnit.
 
Sid
Sid
@CooperCape Use integral-calculator?
 
Novalium Company
Novalium Company
Guys, life is so unfair. I wanted a quantum computer for my birthday but instead I got a ferrari...
 
enumaris
enumaris
did you yell at your parents?
 
Novalium Company
Novalium Company
8:19 PM
Yes, I was very angry.
 
Sid
Sid
Hmm... I am trying to figure out if all this is Sarcasm or serious
 
Novalium Company
Novalium Company
Hah, it sarcasm don't worry :D
I must be Elon Musk's kid in order to get a quantum computer or a ferrari :D
I can barely afford a sandwitch :D
 
CooperCape
CooperCape
8:32 PM
@Sid I was... partially joking. Was just a simple substitution but it’s nice to check my answers.
 
Jake Rose
Jake Rose
9:15 PM
@vzn Yeah Im a first year undergad but I quite enjoy reading from a popular science perspective. Easy on the brain ygm
Thanks btw @vzn will give it a look
 
Emilio Pisanty
Emilio Pisanty
0
Q: Electromagnetic field with direction in quantum theory

B. D.Could the electromagnetic field be described as the wave-like motion such as with frequency and wavelength? Because the electricity has positive and negative signs while the waves only have different direction to travel with, I wonder could it be described as the wave-like motion with different s...

quantum-mechanics
goodness
@JohnRennie maybe you want to have a go?
 
Captain Bohemian
Captain Bohemian
@NovaliumCompany some parents never celebrate birthdays for their children.
 
Joe Stavitsky
Joe Stavitsky
10:00 PM
If x is a line integral of f(t),g(t), how do I know which way t is increasing? Is it in the way f(t) and g(t) are written, or the interval definition of t, or the expression of the line integral?
 
 
1 hour later…
enumaris
enumaris
11:07 PM
what's the comma operator?
 

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