The h Bar

0celo7

12:08 AM

@Semiclassical the seminar schedule is still wrong...

Semiclassical

:/

0celo7

@Semiclassical on the flip side, Curb Your Enthusiam's new season is great

Secret

3:39 AM

2

Q: Time reversal and Antilinear operators

I'm struggeling to solve this question. Can anyone help me please? Let us consider a generic quantum mechanical system governed by the Hamiltonian $\ H(t) $. In what follows we denote the evolution operator by $\ u(t, t_0) $. Hence, $\ |Ψ(t)> = u(t, t_0)|Ψ_0> $ satisfies the ti...

Not sure what physical system will involve antiunitary and time reversal, probably magnetic systems as magnetic fields break t symmetry

Fawad

4:03 AM

Hi. Can someone explain what’s happening here?

user84215

Hi.

Fawad

Hi.

0celo7

@Semiclassical A functional analyst is an analyst, first and foremost, and not a degenerate species of topologist. - Hille

0celo7

4:51 AM

@Slereah Ugh I'm back to Yvonne

I need to understand Sobolev metrics

Secret

Some thought:

It may seemed that we are given 24 hours, but in reality, in order to have a healthy body, and combined with the transportation time, we technically only have 13-15 hours per day (including 7 hours of sleep)

There's an insane amount of time wasted on just traveling from A to B as part of the routine (We are not talking about travelling in terms of relaxing or sighseeing like those in trips)

Sure, with the advert of mobiles and other electronic devices, we can try to squeeze some of that unutilised time, but there are still a lot of jobs that only a desktop computer can do and thus all tha…

Secret

5:06 AM

And that is why, I seriously want portable wormholes, imagine being able to fully utilised all that wasted time of travelling

Actually about wormholes, the mere ability to build one connecting two spacelike separated patches of spacetime, we will already be able to demonstrate retrocausality even if the mouths are not time dilated. The reasoning is as follows:

Consider a beam of light traveling from A to B without going through the wormhole vs a beam of light traveling from A to B through the wormhole. Suppose A and B are separated by 5 ls. Therefore it takes light 5s to reach from A to B or B to A. This means using relativity, since A and B are not time dilated wrt each other, from B's frame the information carried by the light beam from A is actually 5s earlier in the past, and vise versa. Now

suppose the light beam travel from A to B through the wormhole. Let's suppose the travel time through the wormhole is 0.2s, then the same light beam as seen from B is only 0.2s in the past.

So when A send two light beam signals to B, one via the wormhole and one does not, B will receive one of them TBC

Secret

5:34 AM

(cont.)

So when A send two light beam signals to B, one via the wormhole and one does not, then B is effectively receiving information from 0.2s and 5s in A's past, but is simultaneous in A's frame

Secret

6:20 AM

So now imagine A send out the signals with a delay of 1s, where the earlier one a travels to B not through the wormhole and the later one b travels to B through the wormhole, then in B's frame, b seemed to came from 5s in the past but arrived at 0.2s later, while a came from 6s in the past but arrived at 4-0.2s later than b, hence the causality is reversed by the wormhole travel

Abcd

Which physical chemistry book should I go for- Peter Atkins, Moore or Levine?

3.5

look at mcquarrie

i'd go for that

Abcd

@3.5 Is it good for high school?

3.5

none of those books you listed are high school

Abcd

@JohnRennie Please see if u have any suggestions.

3.5

6:24 AM

it's around the same level as those

why do you want to learn physical chem?

Abcd

@3.5 I don't have any good theory book for that but there's ample of physical chemistry in my syllabus. Also, I like reading chemistry from good books.

3.5

unless you're specifically planning to go into chemistry you'd be better off learning quantum mechanics, thermodynamics and kinetics stuff from a physics book and you'll assimilate all the physical chemistry stuff along the way but you'll have a deeper and more rigorous understanding of it.

@Abcd if it's for high school chemistry then don't read those books

those are advanced

you need to know multivariable calculus and differential equations to understand those books

read modern chemistry by oxtoby instead

it has physical chem sections too

that book is 1st year university level so it should be fine to read

Secret

Therefore, the past came "later" than the future of A. (More details later, it appears despite the reversal of causality, you cannot produce a grandfather paradox)

Abcd

@3.5 Are you sure it's worth it? We have kinetics, equilibrium, atomic structure, radioactivity, thermo, kinetics, etc etc in our syllabus.

Bernardo Meurer

@dmckee @JohnRennie Around?

3.5

6:28 AM

@Abcd what do you mean "worth it"?

yes oxtoby's book is probably more similar to what you are learning than those books you listed

John Rennie

@BernardoMeurer I'm about to start checking servers. Is it a long question?

Bernardo Meurer

@JohnRennie I assume not: Will I gain any considerable speed by implementing Merge Sort with concurrency

3.5

@Abcd these are very basic topics and any freshman chemistry textbook will cover them in detail.

Bernardo Meurer

(i.e. spawn merge sort on a new thread with every split)

Abcd

@3.5 Okay, thanks. I'll buy it then...

3.5

6:30 AM

@Abcd don't buy it yet

look at the pdf and see if it's the right level for you

Abcd

okay.

John Rennie

@BernardoMeurer can you use multiple threads for a merge sort?

3.5

it uses calculus so it might be too difficult if you haven't learned calculus yet

@Abcd if it was too difficult for you then use zumdahl's chemistry book

that's also a very good book for your level

Abcd

@3.5 We will be learning calculus extensively from january so that's not a problem. Presently, I know basic calculus.

3.5

okay then oxtoby should be fine, but supplement it with zumdahl

those books should be the best combination for you to learn what you want.

Abcd

6:33 AM

Okay, sure. Thanks a lot for the suggestions.

3.5

np. good luck

also if you're reading zumdahl do all the "challenge problems" at the end of the chapter

ignore the basic ones because they're easy. but the challenge problems in zumdahl as difficult, more than oxtoby.

Abcd

Zumdahl isn't available in my country. I would have to use it's pdf :(..

@3.5 Ok.

3.5

what country?

are you sure you're looking at the right book?

he has more than one chemistry book

Abcd

yes.

@3.5 What's the exact name?

3.5

it's just called "chemistry"

he also has one called "chemical principles" but that is a tiny bit more advanced (oxtoby level)

you can read that one too if you want

it's also a good book

Abcd

6:39 AM

amazon.in/Principles-Modern-Chemistry-David-Oxtoby/dp/…

Is this one correct^?

3.5

oxtoby yes

Abcd

Is the print black and white only?

3.5

no

I have a physical copy

mine is international edition but it's printed in high quality colour.

so it should be fine

Abcd

Oh, I bought LG wade's organic chemistry. Got a black and white edition and it sucks!

3.5

lol why would you read wade?

that is a bad book

Abcd

6:42 AM

People recommended that to me.

3.5

you should read either mcmurry or clayden's book

Abcd

@3.5 I also have Morrison Boyd for organic chemistry.

3.5

idk that book

all I know is that mcmurry and clayden are the best books for learning IChO level chemistry

because the profs at the training camp recommended it

(5 years ago)

Abcd

@3.5:

amazon.in/Chemistry-Textbook-Cd-Steven-Zumdahl/dp/0618638199/…

Is this the correct zumdahl book?

3.5

yes but that's an old version

it should be fine though

that's probably the version that i used

Abcd

6:50 AM

@3.5 this one's coloured too?

3.5

i have the real version of that so i don't know

the real version is

but it should be

i just checked @Abcd it is coloured

don't worry :p

Abcd

@3.5 the latest edition is 9th and this is 6th :(

3.5

so?

I learned from the older version and it was fine.

in these kinds of popular textbooks they release a new edition every year and only make tiny changes that don't effect it

they are all basically the same

you'll be fine, don't worry so much about things like this and start reading/learning. i wish someone gave me that advice back then.

Abcd

Ok, sure.

3.5

btw @Abcd if you want to do some really nice and difficult chemistry problems look at these and do all of them. it's the ones I did and I found them really good for getting a deep understanding of the chemistry concepts and prepare you for more advanced stuff.

@0celo7 why are you awake?

I thought you were normal in terms of sleeping.

Bernardo Meurer

7:10 AM

@JohnRennie Sorry, I had a stroke

Yes

I imagined that when I split the structure I would spawn a new thread to work on each half of it

Rumplestillskin

7:52 AM

Hey guys! Does anyone know how to reference a dataset obtained from the JPL Horizons site?

John Rennie

9:03 AM

"Hanging Around" by The Stranglers is currently playing on the radio. Happy memories :-)

Anonymous

10:50 AM

@JohnRennie Any idea what a sequence of elements in a metric space means? Suppose $M$ is the unit circle in $\Bbb R^2$. They say that a sequence of elements ${x_n}_{n=1}^{n=\infty}$ of a metric space $\<M,d\>$ is said to converge if $d(x,x_n)\to 0$ as $n\to\infty$. I'm not sure what the sequence of elements of elements of an unit circle would be. We can suppose $d$ is the ordinary 2D distance function here.

Anonymous

I also don't think they mean set of elements in the unit circle instead of sequence.

Anonymous

Basically I'm confused about what they mean by sequence of elements of a metric space

John Rennie

@Blue no idea, sorry :-(

Anonymous

Alright. No probs. :)

Anonymous

Perhaps @0celo7 would know

John Rennie

10:56 AM

@Blue Some Googling later I think I have at least a partial answer for you ...

Anonymous

Which one?

John Rennie

what a sequence of elements in a metric space means

Anonymous

Yes, I'm looking through MSE

John Rennie

I found a good description here

Anonymous

Did you find any good answer?

Anonymous

10:57 AM

Oh, checking

Anonymous

11:08 AM

I think I get it! Say, we have a sequence of elements in the metric space $x^2+y^2=1$ like $x_1,x_2,x_3,...$. Suppose $x_1$ is the point $(\cos(\pi/2),\sin(\pi/2))$. $x_2$ is the point $(\cos(\pi/4),\sin(\pi/4))$ and so on, such that $x_n=(\cos(\pi/2n),\sin(\pi/2n))$. As $n\to\infty$, the sequence converges to the point $(\cos(0),\sin(0))=(1,0)$ which is an element of the metric space $x^2+y^2=1$.

Anonymous

Thanks @JohnRennie!

0celo7

12:05 PM

It's the same thing as in R

A function N --> X

Secret

[Random]

(0,1)(1,2)(2,3)(3,$\pi$)(4,6)(5,7)(6,8.5)(9,$\sqrt{82}$)

thatsmathematics.com/mathgen/…

ACuriousMind

@Secret Of what significance is that string of numbers supposed to be to anyone but you?

Secret

ok I admit I am just bored this time

Living on the opposite hemisphere most of you are sleeping and the internet is too quiet

In fact, ever since Kaumudi no longer visits the room recently, the peak hour of the chat seemed to be shifted closer to the morning periods of australia, which means SE itself is very quiet during most of the time I am awake

ACuriousMind

@Secret No need to rely on your impression - the room info has a graph of when activity is highest/lowest throughout the day.

Secret

12:22 PM

hmm, the activity graph in terms of week seems very spiky, but the graph in terms of day has a broad base. I am not sure, cause I don't have in store the activity graphs back in 2-3 month ago

Current peak hour does lies somewhere at 6:00 am sydney time according to the graph, while in the past I don't need to stay awake til 5:00 to chat. But yesterday the chat section goes from 2:00-3:something, so perhaps the activity does not really shifted

0celo7

@ACuriousMind watch the new season of Curb

the premise is amazing

ACuriousMind

What's Curb?

0celo7

your enthusiasm

Secret

en.wikipedia.org/wiki/Curb_Your_Enthusiasm.

ACuriousMind

@0celo7 Never seen it

That is, I was not consciously aware of its existence until right now

0celo7

12:31 PM

@ACuriousMind I remember very clearly talking to you about it

are you a clone?

Dec 29 '15 at 14:13, by ACuriousMind

@0celo7 Carlin yes, CK no, never heard of David

hmm

@ACuriousMind well watch it anyway

you need to watch the first 8 in preparation tho

they're all amazing

ACuriousMind

Ah, well, something for a hungover Sunday :P

0celo7

@ACuriousMind not if you're in pain. Laughing will just make it hurt more

ACuriousMind

If my hungovers ever make laughing hurt, it may be time to stop drinking that much, I think...

uhoh

12:48 PM

10

Q: Parker Solar Probe passing extremely close to the Sun; what relativistic effects will it experience and how large will they be?

note: This is a question about relativistic effects. I've included some detail about the spacecraft and its orbit for background, but the question is about relativistic effects and their observability. When the Parker Solar Probe passes within 8.5 solar radii of the Sun, it will be moving rea...

relativity sun space-travel space-mission

This shouldn't be too hard for someone with a bit of GR familiarity.

0celo7

@3.5 When my phone is on chat and I put it to sleep, it refreshes and makes my pic show up

Semiclassical

hi chat

ACuriousMind

I'm afraid the chat system has not yet achieved the necessary level of sentience to answer you

Semiclassical

worth a try

Here's a (likely silly) question.

Suppose I want to create pairs of entangled particles. What ways do we have experimentally of doing that?

With photons it seems to be by taking advantage of how lasers work (spontaneous downconversion etc)

And with pairs electrons it should just amount to creating singlet states, which seems straightforward enough.

I imagine these aren't the only ways, but I'm ignorant of what the other routes would be.

Mithrandir24601

1:03 PM

@Semiclassical $\left(H\otimes I\right)\text{CNOT}_{0\rightarrow 1}$ or variants thereof

i.e. any 2 qubit system that allows for CNOT is a good starting point (to my mind)

Semiclassical

hmm. is that a restatement of what I'm after?

feels like it

Mithrandir24601

@Semiclassical Sort of... It won't get you all the systems that you can use to generate entanglement, but it might be easier to find?

Semiclassical

hmm

fair enough.

I think that switches the question to what kinds of two-qubit systems have actually been realized experimentally.

Mithrandir24601

Well then, how about "what systems theoretically allow for CNOT gates"?

It's pretty broad to say the least...

Semiclassical

Maybe it is, but I don’t actually knoe

Mithrandir24601

1:12 PM

Feels like a question for the quantum computing proposal :P

Or maybe I'm just detracting away from the actual problem

Semiclassical

The examples I know are 1) electrons in quantum dots, and 2) lasers as sources of entangled photons

But those can’t be the only examples

0celo7

@ACuriousMind task manager has GPU stats now

Mithrandir24601

@Semiclassical OK, systems include: electrons, holes, nuclei, molecules, ions, neutral atoms, dots, photons, superconducting qubits

So, yeah, more or less anything that's small enough to be quantum

Balarka Sen

1:30 PM

@Blue A sequence of elements in $(M, d)$ is just a collection of (countable number of) points $x_1, x_2, \cdots$ such that each $x_i \in M$.

There's no much ambiguity in the terminology :)

@0celo7 I learnt what I believe you would accept as analysis today

Semiclassical

I think that’s probably right, but the details are what I’m after

0celo7

@BalarkaSen metric spaces are M in your mind?

Balarka Sen

No, X

0celo7

1:45 PM

X for metriX

@BalarkaSen I accept lots of things as Analysis

Balarka Sen

@0celo7 How about this

pretty damn dank isn't it

0celo7

Christ

I thought you were allergic to inequalities

Balarka Sen

@0celo7 I chugged some cetrizines down

user929304

@JohnRennie Dear John, thx for getting back to me. Let me know when we could chat briefly.

John Rennie

2:01 PM

@user929304 Hi. I'm about to make lunch, but I'll be around for a couple of hours or so. Give me 15 minutes to get lunch on.

0celo7

@BalarkaSen I need to learn surgery theory. Can you teach me topology

Balarka Sen

I don't know surgery theory

user929304

@JohnRennie sure, awesome!

0celo7

@BalarkaSen I need to learn some homotopy theory

Balarka Sen

Ok?

what do you want to know

0celo7

2:09 PM

@BalarkaSen I don't know. I just know I have two surgery papers I need to read. I should probably start and then figure out exactly what I need

user929304

@ACuriousMind Hi, thanks a lot for the very pertinent comments on that post. Luckiliy, you are there to catch these kinds of mistakes :-) Would you be kindly interested in writing an answer from your perspective? (because you seem to have a much firmer knowledge on the essence of the matter). It would definitely be a positive addition to the existing answers.

ACuriousMind

@user929304 I'm afraid I don't really understand what your question is angling for. Regarding whether one can put magnetic and electric charges on equal footing, see this answer of mine, regarding whether or not the magnetic field is "fundamental" see this question about deriving EM purely from electrostatics (Coulomb's law) + special relativity

Detecting wrong answers is often easier than writing a good correct one ;)

John Rennie

@user929304 right, lunch is on (chicken pilaf) and I have about 25 minutes to chat

BTW what time zone are you in?

0celo7

@BalarkaSen I think what I'm missing is a good understanding of relative homology.

It shows up really often in manifold topology

Balarka Sen

relative homology is pretty good

Semiclassical

2:20 PM

@0celo7 FYI, baymax in the math chat was asking if I know any FORTRAN (I’ve helped him out with stuff before)

But I don’t FORTRAN

I know you have some understanding of it, though. So just in case you’re interested

John Rennie

@user929304 re your question about books, I'm sadly out of touch with modern books - I last studied this stuff in 1981 :-) Have you seen our book recommendations master question?

Physics Meta

-1

Q: Why has my question been put "On Hold"?

I have a question about my Physics Stack Exchange post: Could you help me please with mathematical model of the soil freezing process? I got it (I fix my question) Why is it "On Hold"?

discussion support specific-question close-reasons review

Fawad

😤

user929304

@JohnRennie Great :) Central European Time

@JohnRennie alrighty, fair enough :), I will check out that link, thanks.

@JohnRennie do you recall that post you had written on the common GR misconceptions? more precisely, the wrong picture of imagining a sheet being curved for explaining curved spacetime.

John Rennie

@user929304 I asked about the time because I'm usually in the chat from about 5 a.m. to lunch UK time (I work an early shift) and that's the best time to chat to me, while I'm still fresh :-)

user929304

2:28 PM

@ACuriousMind thanks a lot for the links, very relevant for me at the moment. Haha that s true :)

John Rennie

@user929304 I don't remember - I've written hundreds, literally, of answers on GR. But anyhow, what did you want to ask?

user929304

@JohnRennie ahh I see, very good to know.

Emilio Pisanty

@JohnRennie presumably @user929304 means this one?

-1

Q: How is gravity proportional to space-time curvature in the rubber-sheet analogy?

In General Relativity, Einstein established that gravity is due to the curvature produced by objects in space. We all know that gravity is proportional to mass. The picture Einstein painted looks like this: The bigger the object, the bigger the curvature and hence the stronger gravity. Let's sa...

general-relativity gravity mass curvature

John Rennie

@user929304 BTW you can click the little triangle next to a post and choose Reply to this message to indicate which post you're responding to:

user929304

@JohnRennie yeah that s also why I couldnt find it again anymore haha, I just remembered that you had given very strong arguments for why it s wrong and also provided the more correct way of understanding these things in GR. I will look for it again and let you know once I ve found it. Regarding the gravitational waves discussion, (the comments), would you consider writing a post here on "What gravitational waves are?" In the spirit of your posts on for instance "What is time dilation?"

@EmilioPisanty Hi Emilio, good find, this is definitely along the lines we were looking for, but that s no the one, because I recall that answer was just a big bulk of text without equations.

John Rennie

2:34 PM

@user929304 I doubt the account of gravitational waves you're looking for exists.

The trouble is that GR describes gravitational waves - well gravity in general - but you have to understand that it's just a description and no-one is claiming that's what actually happens.

Newcomers to physics have a tendency to ask yes, but what's actually going on but that question is one for the philosophers.

ACuriousMind

@user929304 It always helps to contrast this with "easier" topics - what would your answer to "what is an electromagnetic wave?" be?

Usually people tend to ask these "yes, but what it is really" questions about phenomena that seem outlandish, but they're actually equally unanswerable for more familiar phenomena

John Rennie

There are attempts to explain the origin of the Einstein equation in more fundamental terms but they are highly speculative. String theory is one obvious candidate, as is Verlinde's entropic gravity idea, but right now all we can say is that GR works so we use it.

user929304

@JohnRennie Indeed, I guess it s rather common problem as to what is just the mathematics and the physics, not that necessarily there ought to be clear distinction in modern physics. For instance, how there are tons of discussions always on the "physicality " of wave functions in QM, that they're not physical waves in the sense of EM waves.

In analogy I guess, my confusion is: on the one hand, we say spacetime doesnt have a fabric (or it even has to rethought because of QM and Heisenberg uncertainty), but then we measure physically perturbations in spacetime (call them GWs), so I don't see how to marry these ideas in a coherent way.

Semiclassical

Math.

0celo7

Math is unreasonably effective.

John Rennie

2:41 PM

@user929304 Spacetime is a concept in relativity and it is a purely geometric concept. When I talk about spacetime I'm always referring to its definition in GR, mainly because I have no idea what it really is :-)

ACuriousMind

@0celo7 Wigner :)

Semiclassical

(Which is really shorthand for: It may be difficult to reconcile these things, but you’re not going to get anywhere unless you can actually calculate things)

user929304

@ACuriousMind totally agree, that's fair to say. I guess for EM waves, people generally ponder less about, just because they associate light, EM radiation, the same understanding they associate to classical sound waves, with which we have close experience in daily life, constantly being told: this is this form of energy being propagated in this medium. And the latter kinds of statements, is harder to make for GW's, does that make sense?

0celo7

@ACuriousMind don't tell people I'm stealing quotes from an algebraist!

ACuriousMind

@user929304 Ah, but what "is" energy?

It's just a word we made up, a number we assign arbitrarily but consistently to physical processes and pretend it "explains" them

You can't point to any thing and say "that is energy"

0celo7

2:44 PM

Have you seen energy in the night sky?

John Rennie

@user929304 I have to confess that I too think of electric fields as somehow real while the metric tensor seems awfully abstract. But this is just because we grow up used to electrical phenomena. Once you start looking closely even electric fields become remarkably evasive things.

Semiclassical

The Noether charge associated with invariance of theories under time evolution :3

user929304

@ACuriousMind I know I know, we re reaching the philosophical grounds where no real physics answer can be given, reminds of the Feynman bit, saying when people ask "why", there s always a problem that to what depth of explanation they will be satisfied. :)

0celo7

@Semiclassical ugh I'm having PTSD from my bundle adventures over the weekend

Semiclassical

Lol

0celo7

2:45 PM

I can do without Noether for a while

ACuriousMind

@user929304 My point is less that there is no "real physics answer" but that these are not "real physics questions" in the first place ;)

Semiclassical

No to Noether

Slereah

The GR book I ordered has been shipped but still not MTW

user929304

@ACuriousMind Indeed, and I personally always avoid those kinds of questions, because I know they tend to be more philosophical in nature. to clarify a bit, what is one ought to say to people who say "but EM waves are more physical whereas wave picture of QM is purely mathematical?"

Semiclassical

If it’s not a question about stuff you can actually measure, it’s probably not s physics question

0celo7

2:47 PM

@Slereah should I order MTW...

user929304

@ACuriousMind ahh, yes that's a good way of seeing it :)

Semiclassical

It’s a question of metaphysics. And I don’t necessarily mind that

ACuriousMind

The "real physics answer" to "What is energy?" is what Semiclassical said: The Noether charge of time translation. The "real physics answer" to "What are electromagnetic waves?" is: Something approximating a solution to the vacuum maxwell equations, i.e. wave equations. The "real physics answer" to "What are gravitational waves?" is: A certain kind of solutions to the Einstein equations.

user929304

@JohnRennie Indeed. before you leave may I ask one more concrete and very naive question? what do we mean in physics when we say this is a dipolar field, or a quadrupolar field? does it say something about the source that generated the field?

Emilio Pisanty

@user929304 yes. it says that the source is dipolar or quadrupolar, (& so on)

Semiclassical

2:50 PM

A light gloss on that is whether we can characterize that field in terms of a vector

Eg the dipole magnetic field has a preferred direction: the earths magnetic poles

user929304

@EmilioPisanty alright, is the analogy in the increasing number of poles, similar to how we characterize: scalars, vectors, tensors ...?

Semiclassical

With a monopole field, that’s not possible because it looks the same in all directions

user929304

@Semiclassical ahhh I see

Semiclassical

With a quadrupole field, there’s some kind of ‘directionality’ there, but it can’t be categorized using just a vector

Instead, you need a rank-2 tensor to describe what’s going on

user929304

@ACuriousMind fair enough, one should try and not lose objectivity. Indeed I wish all physicists saw things similarly :)

Semiclassical

2:54 PM

If you want an octopole field, you’ll need a rank-3 tensor. And so on

ACuriousMind

@user929304 To be fair, I should point out that I'm sort of extreme in that viewpoint - many think one should not eschew ontology that consistently.

user929304

@Semiclassical I see, that clarifies a lot already. So do we say that electric fields are monopoles? as in there s not discerning direction?

0celo7

@user929304 that's because he's a mttaaician

Semiclassical

Well, one has to be careful with the terminology here

John Rennie

@user929304 electric charges are monopoles. Electric fields aren't monopoles.

user929304

2:56 PM

@ACuriousMind I know, it has come across to me through your answers in general, but I like that.

ACuriousMind

(as evidenced e.g. by the large amount of different quantum interpretations, and the rather small fraction of physicists who truly subscribe to shutting up and calculating)

@0celo7 A what?

Semiclassical

@ACuriousMind I prefer “shut-up-while-you-calculate” :3

ACuriousMind

@Semiclassical No, I always mutter under my breath when calculating something :)

6

user929304

@JohnRennie oh, that s true. I guess Im still confused as to what it means when a field is "polar"

Semiclassical

On the one hand, the electric field is described as a vector field in the sense that it’s a vector-valued function of position

user929304

2:59 PM

@ACuriousMind hahahaha

Semiclassical

But that’s different from the mono/di/quadrupolar aspect

John Rennie

@user929304 any random field can be expressed as the sum of a field from a monopole, the field from a dipole, the field from a quadrupole and so one. But we wouldn't say the field is monopolar, diploar or whatever.

Transcript for