The h Bar

Random thought: I do find the whole "Kung Fu isn't a good martial art as it's not realistic enough for street fights" thing quite amusing as, aside from all the other issues about whether or not that statement is true, everyone seems to have forgotten that it's mainly a martial art that actually heavily involves weapons, so it's obviously not all that relevant in a modern day 'street fight'

0ßelö7

I always have three weapon on me

Mithrandir24601

A maths textbook, a long and boring maths proof and the warning of opening said textbook to read out said proof :P

0ßelö7

12:24 AM

To quote one of my favorite people (John Duffield): "The map is not the territory." Curved spacetime is a model. You can't actually believe that spacetime is a smooth manifold. (What does that even mean?) "Gravity is spacetime curvature" is just a slogan for GR, it is not reality. — 0ßelö7 22 secs ago

Come at me

I just quoted John Duffield unironically

@JohnRennie

@Mithrandir24601 lol

why do you think I always have some measure theory on hand

if people come at me they get the Riesz representation theorem

skullpatrol

That'll knock'em out.

0ßelö7

Riesz–Markov–Kakutani representation theorem

In mathematics, the Riesz–Markov–Kakutani representation theorem relates linear functionals on spaces of continuous functions on a locally compact space to measures. The theorem is named for Frigyes Riesz (1909) who introduced it for continuous functions on the unit interval, Andrey Markov (1938) who extended the result to some non-compact spaces, and Shizuo Kakutani (1941) who extended the result to compact Hausdorff spaces. There are many closely related variations of the theorem, as the linear functionals can be complex, real, or positive, the space they are defined on may be the unit interval...

@Mithrandir24601 Or we go through the construction of Lebesgue measure by hand

I have several deadly techniques

Mithrandir24601

12:51 AM

@0ßelö7 Well, I'm going to bed now, so feel free to start whenever you feel like ;)

0ßelö7

@Mithrandir24601 HBO Go servers are down

too many people waiting for GoT

Mithrandir24601

@0ßelö7 Haha - I'll just wait a few hours until I get up

0ßelö7

@Mithrandir24601 Oh no, it works!!!!!!!!

GET HYPED

rob

If Game of Thrones is too mainstream, I'll be on the radio for a couple of hours. Listen along.

0ßelö7

@rob I don't see your name there

rob

1:00 AM

@0ßelö7 For the Harbison there were about 300 people on stage.

0ßelö7

is there a list of everyone playing?

rob

Not on the radio station's webpage. I'm not sure how good the symphony is about historical rosters.

But that piece was recorded for commercial release, and that album will have everyone's name.

0ßelö7

what do you play?

rob

I'm in the chorus.

0ßelö7

I can't even contain the hype

I'm watching it and am hyped

skullpatrol

1:22 AM

Thanks @rob I'll have a listen :-)

Rumplestillskin

5:13 AM

Hello all!! Is anyone familiar with obtaining the energy integral from Newton's second law?

Pritt Balagopal

7:44 AM

Hello @JohnRennie

John Rennie

Morning

Pritt Balagopal

Good afternoon!

John Rennie

How much QM have you done?

Have you learned the Schrodinger equation?

Pritt Balagopal

Basically, nothing.

Well, my school syllabus focused more on the Bohr model, and the Schrodinger Equation was just like "It exists" as far as my school goes.

John Rennie

In that case I think you're going to have to just accept that we can get stimulated emission. I don't think you can understand it without a basic grasp of QM.

Pritt Balagopal

7:46 AM

Now I'm in college, and my physics professor isn't really good. We are learning about lasers.

Hmmph, my college is so annoying.

They haven't even taught QM, and they're hopping off to lasers already.

John Rennie

You can still learn about lasers, but some things you're going to have to take on trust.

Slereah

Pew pew

I'm a laser

John Rennie

@Slereah Not a skunk?

Slereah

Pew is his name, not his signature sound

skullpatrol

Pepe?

Pritt Balagopal

7:49 AM

Yeah, so I just gotta believe that stimulated emission happens.

Hey @JohnRennie suppose I read QM from the basics for about an hour a day

John Rennie

@PrittBalagopal basically yes. If you haven't even studied the Schrodinger equation I don't know of any simple way to explain it.

Pritt Balagopal

How many days would it take me to understand Stimulated emission?

Oh ok, I'll check out the equation.

Do I have to learn how to solve it was well?

John Rennie

Presumably your course will cover this at some point?

You might be better advised to wait until your course starts on it.

Pritt Balagopal

Yeah, that would be a better choice.

1

Q: Constraints with springs?

I want to find the acceleration of A in terms of the acceleration of B. But I don't know how to proceed because of the spring attached

This question is rather interesting.

Anonymous

9:31 AM

@PrittBalagopal The book "Quantum Physics for Dummies" is really good. I am learning QM from there. Also this website eng.famu.fsu.edu/~dommelen/quantum/style_a/index.html is great. If you wish to learn Linear Algebra required for QM then I can give you the link to a chat room where a SE user is teaching me LA. LA is very important for QM. Good luck. :)

CooperCape

10:49 AM

Helllo

user84215

Hello.

Kenshin

11:10 AM

Hello people

Let us discuss

Balarka Sen

Let us discuss discussion

Or, rather, let us discuss discussing discussion

Kenshin

what is important to discuss during a discussion?

Secret

[Time travel]

Kenshin

@BalarkaSen is seeking power and control an important human endeavour?

Secret

Discussing about the dynamics at the moment of triggering a grandfather paradox in time travel models where history rewrite is instantaneous

in The Factory Floor, 23 mins ago, by Bellerophon

If I am affected by my own changes to time then, assuming I have truly prevented and convinced my double not to enter the time machine, then I will probably be wiped from existence.

A limit calculation on some ordered set will be done later to check

Kenshin

11:15 AM

@Secret I disagree that time travel will ever result in existences being wiped out

Balarka Sen

@Kenshin youtube.com/watch?v=oVA1gf2jAFU

Secret

yeah, probably the time travel that will happen in our universe (if any) will completely prevent them from occurring in the first place

Kenshin

@Secret yes probably

closed timelike curves

alternatively when you travel back in time you enter a parallel universe

@Secret suppose a spin x particle goes through the gerlach experiment and comes out as z+. If you go back in time and observe the experiment again, could it come out as z-?

Secret

If you are not a superdeterminist, then I expect the probabilistic nature of measurement will mean it can come out as -z.

Kenshin

so this means that you are then in a parallel world

Secret

11:21 AM

Interestingly, it does seemed that in such scenario, where the electron spin will be pointing seemed to be somehow averaged out and give our observed present

Kenshin

but it might give a totally differentt macroscopic outcome

here is my second theory @Secret

when you measure the spin initially you become entangled with the outcome

so there is a (you measured spin+)(and spin was up) state and a (you measured spin-)(and spin was down) state and they are entangled

now when you go back in time

and perform the measurement again

because you are already entangled with the outcome

the outcome must be identical to what you saw intiially

and it is this that ensures the future works out exactly in line with how it happened originally

Secret

But that does raised the question: How can one be sure that there isn't any interaction during the time travel that breaks this entanglement and thus result in you (or more minimalistically, another measurement device) to no longer have correlated outcomes?

after all, entanglement is kinda fragile

Kenshin

if the entanglement is broken in such a scenario, this is merely equivelent to saying ur measurement was wrong

for example, when you make a measurement you observe spin + and you assume the outcome was also spin + (in line with the observation)

so you are entangled with the outcome

now to say this entanglement could be broken

is to say the outcome could well have been spin down, yet you measured spin up

so this just means you measured wrong

so I suppose in such a case it is possible that when you go back in time, your initial measurements become "fuzzy"

in which case you don't know what happened initially, so it's hard to compare the new future with what happened the first time around

Secret

That makes sense and kinda reminds of David Deusch's model of time travel in quantum mechanics, where the outcomes in the time interval where the time travel took place is described by some density matrix

Sir Cumference

11:41 AM

Morning

Kenshin

morning

Sir Cumference

11:57 AM

@Kenshin Did you see last week's eclipse, by the way? :)

Kenshin

na

only visible in the US wasn't it?

Sir Cumference

@Kenshin I somehow thought you were in the U.S...

Kenshin

the land down under mate

Anonymous

@JohnRennie I'm having trouble understanding LCAO method of combining orbitals. I don't understand what they mean by negative wavefunction. I thought the wavefunctions have no physical meaning. So it doesn't make much sense to add or subtract them to get the net wavefunction or something like that.

Anonymous

Uh...JR is gone :/

Secret

12:41 PM

While orbitals are probabilities, LCAO said that MOs are formed from linear combination of AOs, which like wavefunctions, can interfere with each other thus they have both positive and negative phases

Anonymous

@Secret Could you explain what "phase" means in this context?

Secret

The phase is not directly measurable, but relative phase is what allows you to have antibonding and bonding MOs

Anonymous

@Secret What do you mean by "phase"? I'm confused by that term. Could you please define it?

John Rennie

12:57 PM

@Blue any combination of solutions to the SE is also a solution to the SE

rob

@Blue The "complex phase" is a factor $\exp i\theta$ out front of an otherwise-real function. Since $\exp i\pi = -1$, a sign difference is a special case of a phase difference.

John Rennie

So if we have some solutions $\psi_i$ we can construct another solution: $$\Psi = a_0\psi_0 + a_1\psi_1 + ... $$ for any numbers $a_i$ subject to the whole thing being normalised.

And those $a_i$s can be negative as well as positive.

Anonymous

@JohnRennie Sure. But then I could add $30\psi_1+100000\psi_2$ (after normalizing) and say that it is the wavefunction of the combined orbitals.

Anonymous

There should be some reason as to why we take only $\psi_1-\psi_2$ and $\psi_1+\psi_2$

John Rennie

@Blue the $\psi_1$ and $\psi_2$ in your example are the solutions to the single atom SEs not the SE for the whole molecule.

@Blue symmetry

Very near the atom we expect the orbitals to look like the atomic orbitals.

Remember that the observable is $|\psi|^2$ so it doesn't matter if $\psi$ is negative.

Anyhow, I have to dash into town. I'll be around later if you're still curious about this.

Anonymous

1:02 PM

@JohnRennie Alright. Do you mean the SE when solved for the whole molecule gives $\psi_1+\psi_2$ and $\psi_1-\psi_2$ ? Then why don't we directly solve it for the whole molecule instead of giving vague reasons like addition and subtraction of atomic wavefunctions approximately gives the net wavefunction of the diatomic molecule. Is it because it is complicated to solve for for the whole molecule?

Anonymous

Oh, sure

Anonymous

We can continue this discussion later

Anonymous

@rob Umm, why should we take the phase difference of $\pi$ particularly ?

Anonymous

Any reason for that?

Anonymous

Does it have anything to do with electron spin? (I read that on the hyperphysics website....but it was too hand-wavy)

rob

1:06 PM

@Blue I haven't followed your whole discussion, but $\psi + e^{i\theta}\phi$ is the way to combine two wavefunctions so that they have equal probability.

The real combinations $\psi_1 \pm \psi_2$ have the additional feature of symmetry: if you swap particles 1 and 2, the total wavefunction is either unchanged (+) or flips sign (-).

Secret

That's what the field I am in is doing. Solving the SE for the whole molecule is very difficult and only hydrogen molecule and hydrogen like ions can be analytically solved. The field of computational and quantum chemistry is all about solving the molecular wavefunction numerically.

The LCAO is just an approximation of using atomic orbitals to the molecular wavefunction. IT works for most cases but once you have radicals, things start to get inaccurate

Anonymous

@rob Oh. That's the reason. It does make sense. Thanks!

rob

For identical particles, you must have the symmetry that the probabilities don't change if you re-label.

Secret

The electronic wavefunction is antisymmeric due to electrons being fermions (which then give rise to pauli exclusion), only the $\pm$ cominations (there are 4 of them) will preserve the antisymmetry

Anonymous

@Secret That's interesting. We have only the H atom in syllabus I guess. :P

Anonymous

1:10 PM

@rob Right. I get it now. :)

rob

There is an important (and nontrivial) result that identical bosons must have wavefunctions which are symmetric under exchange, while identical fermions must have wavefunctions that change sign under exchange.

@Blue Cool.

Anonymous

@rob Ah, is there any mathematical proof for that?

Anonymous

I'd be interested

rob

@Blue It's called the "spin-statistics theorem" and was proved in the 1940s. But I don't know of a good hand-wavy internet-chat-level proof.

Anonymous

@rob Thanks. Once I'm a bit more comfortable with QM, LA and statistics I'll perhaps go through that.

rob

1:14 PM

In one of the little books of transcribed Feynman lectures (perhaps "QED") he relates it to the fact that fermion wavefunctions change sign under a 360° rotation, and imagines a particle-antiparticle loop as a "rotation in spacetime."

That's the closest thing I know to an "intuitive" proof, but it requires quite a bit of background information.

ACuriousMind

@rob The problem is that it's hard to have a hand-wavy "proof" that really conveys how the actual proof works - the actual proof fails in two dimension, where there are anyons, but I've never heard a good non-technical statement of spin-statistics that would have made the relevance of the dimension clear.

0ßelö7

Oh @ACuriousMind loves

Lives

ACuriousMind

Yup, still comparatively busy, though. Normal activity will resume next week, most likely

Anonymous

1

Q: How to plot the nature of the E-k graph manually ?

I'm trying to plot the nature of a graph from a certain equation manually. The equation is $$P\frac{\sin(\alpha a)}{\alpha a}+\cos(\alpha a)=\cos(ka)$$ where $P$ is a constant. Here, $\alpha^2=\frac{2m}{\hbar^2}E$ where $\frac{2m}{\hbar^2}$ is a constant, say $C$. Hence, $\alpha^2=CE$. I need ...

graphing-functions

Anonymous

In case someone is interested ^ :P

0ßelö7

1:23 PM

@ACuriousMind getting a PhD position?

Anonymous

Anonymous

How is the $E$ negative for valence band? I don't understand

Anonymous

The second diagram shows the E-k plot for a semiconductor and E seems to positive from the Kronig-Penney model

Anonymous

Irrespective of whether the electron is in the C.B or V.B

Anonymous

1:28 PM

There seems to be a discrepancy between the two images

Anonymous

@rob Any idea?

Anonymous

Even if we take the reduced k space for the second image...it doesn't match with the first image

Anonymous

I'm surely missing something

Xasel

2:12 PM

hello everybody !

I was going through Biot-Savart law and I wonder why the the infinitesimal element of current is always perpendicular to the r vector

googled a lot, everybody states it but no ones explains why?

I am talking about this in reference to finding magnetic field at the axis of circular loop

NormalsNotFar

@ACuriousMind You say that the spin-statistics theorem fails in two dimensions where there are anyons. Since there are also anyons in three dimensions does the spin statistics theorem still apply?

Anonymous

@Xasel $d\vec{B}$ was found to be perpendicular to both $d\vec{L}$ and $\vec{r}$

Anonymous

As far as I know that was discovered experimentally

ACuriousMind

@NormalsNotFar I know of no anyons in 3 dimensions.

Anonymous

2:16 PM

There might be some "proof" which I'm not aware of.

Xasel

Well google proves no help too, I am going to ask it on PhysSE

ACuriousMind

@Xasel See physics.stackexchange.com/q/302553/50583

The B-S law is a consequence of Maxwell's equations

If you want something other than "here's how to derive it from Maxwell's equations" as an explanation, you'll have to be more specific about what you want to know

Xasel

@ACurious mind: Well thank you that's an interesting post ,but that not waht uI am concerned about, my question is:

why that <vec>a<vec> vector is taken perpendicular to the current elemt dl?

I can't see how that is perepndicular to dl?

Secret

@NormalsNotFar I also heard of no anyons in 3+1 dimensions, do you have any reference for me to have a read?

NormalsNotFar

@AcuriousMind What about this paper journals.aps.org/prd/abstract/10.1103/PhysRevD.43.1933 or did I misinterpret the whole paper ?

Xasel

2:18 PM

but every derivation in the book assumes such ?

NormalsNotFar

Oh sorry I was meaning 2+1 dimensions

Xasel

wwhen deriving expression for magnetic field at the axis of circular loop

Anonymous

@Xasel Oh! You need to imagine in 3D :P

NormalsNotFar

So you were saying the spin-statistics theorem does not apply in 2+1 dimensions. Hmm ok, well I guess that answers one of my questions in my most recent post lol

Anonymous

Get a circular wheel or loop or something

Anonymous

2:20 PM

And a stick or something like

Anonymous

And try to make that arragement

Xasel

tried but still couldn't see how <vec>a<vec> is perpendicular to dl (it does make sense to me when the point is situated at the centre of circle) .for <vec>a<vec> to be perpendicular to dl it should be parallel to x-axis?a

Anonymous

I can't understand what you're saying...

Anonymous

Why should it be parallel to x axis....

Anonymous

Anyhow, I got to go.

Anonymous

2:24 PM

Hope someone helps you out.

Xasel

2:40 PM

Aha ! finally got it

Thankyou Blue and AcuriousMind

0ßelö7

3:08 PM

@ACuriousMind I am citing HE, who write "space-time," but I write it as "spacetime." Do I cite it as "spacetime" or "space-time?"

ACuriousMind

3:19 PM

@0ßelö7 The latter, I'd say

skullpatrol

Use the citation of the source.

Emilio Pisanty

4:29 PM

The division between "natural" and "artificial" is pretty artificial. Obviously, humans are the dominant natural process that leads to the occurence of lasers. — ACuriousMind ♦ Aug 22 '15 at 16:44

2

@ACuriousMind ↑ that's a fantastic way to put things

imma steal that formulation

Secret

5:24 PM

in Mathematics, 37 secs ago, by Secret

[Chemistry] The 4 stage script is finally working. First 3 out of 40 batches calculations were submitted. Expect to finish them within 3-5 days

If all goes well, all 13400 calculations will be done in 5 days

dmckee

@0ßelö7 Are you citing or quoting?

If you are quoting then you use the original text (and you might add [sic] if the quote(s) is(are) the only instance(s) in paper that use the hyphenated spelling.

If you are siting then you remain consistent with the style guide you are using. You readers understand that the spelling of that compound-word/phrase varies between sources.

DanielSank

Hi, everybody.

skullpatrol

Hi

CooperCape

5:50 PM

I can't not see things in indices now...

specially when things look like $a^i$ or $a_i$

0ßelö7

6:01 PM

@dmckee putting a book title in a bibliography

Physics Meta

6:43 PM

Recent Questions - Physics Meta Stack Exchange: Visual demonstration of a properly asked question

posted on August 28, 2017 by Countto10

Is there much work involved in amending the physics SE "Ask Question" box to include a link to a well asked question? I appreciate this proposal is a dead duck if it can only be applied to all of SE, but can physics SE alone include a line/link to the effect: "Here is an example of an question that received a good response". It's also a dead duck if the concensu…

dmckee

6:57 PM

@0ßelö7 Then you write the title as it is.

0ßelö7

7:36 PM

@dmckee @rob I have a professor whom I've known since the first day of school and am now writing a paper with. I still call him Dr., but he signs all of his emails to me with just his first name. Is that implying I should call him by his first name? He's never actually said anything about it.

dmckee

@0ßelö7 What do his grad students call him? If they use a title then you should too. If they use his given name then you might on safe ground doing so as well.

0ßelö7

@dmckee His grad students are all in their last years, I hardly see them.

dmckee

The only way to be sure is to ask him. Second best is experimenting—try it and observe his reaction closely—or asking one of his grad students.

0ßelö7

I was told one of them hates undergrads and I've never talked to the other about the professor.

dmckee

Well, that shoot my good ideas down in flames.

0ßelö7

7:41 PM

@dmckee I don't think math people (at least at my school) have group meetings like the physicists or engineers do

dmckee

For what it's worth I'm OK with my undergrad research students calling me by my given name to my face, but would like them to use my title when talking about me with other students.

0ßelö7

@dmckee That's how it is with most engineering professors

there are some guys I know through my work whom I call by their first names in that setting, but in class they are Dr. --

DanielSank

Hi, everybody.

dmckee

Hola.

DanielSank

@DawoodibnKareem Dude, if you're willing to be insulted by people on the internet tossing around ideas like that, you're going to have a bad time.

@dmckee Que pasa?

Hey someone make me understand path integrals.

0ßelö7

7:47 PM

@DanielSank I thought you said you understood path integrals

DanielSank

Negative.

0ßelö7

And then gave a rudimentary account of integration

Anonymous

@dmckee It seems to be quite common in the West to call professors by their name. Here professors usually get offended if students don't address them as Sir/Ma'am. :P

0ßelö7

Mar 6 at 18:47, by DanielSank

You basically define the path integral to give the answer you want in some "known case" and then define everything else in a reasonable way using linear combinations.

DanielSank

Yes yes I understand that much.

Let me rephrase: someone make me know how to compute stuff with path integrals.

dmckee

7:51 PM

@Blue Calling professors you work closely with by their given names was ubiquitous at the grad school I attended. And some invited all grad students to use the familiar address, while only a few insisted on formal address from all students.

0ßelö7

I've never called anyone Sir/Ma'am and I never plan to.

DanielSank

bah

dmckee

Though 'formal' meant "Hey, Dr Whosit, when you assigned problem 4, did you mean both parts or just 4a?" rather than Sir/Maam.

Anonymous

@0ßelö7 Westerners get freaked out when called Sir/Ma'am. Atleast that's what I've noticed. Someone named Alon Amit (on Quora) wrote a long post on that.

0ßelö7

@dmckee My grad QM prof told everyone in the class to call him by his first name

DanielSank

7:52 PM

I'm surprised by "Dr" instead of "Prof".

0ßelö7

@dmckee Right, but that might be an American thing. We say our names a lot.

dmckee

And I believe something similar occurred at my undergraduate institution. But professors there preferring informal address from undergrads was much rarer.

Anonymous

@dmckee Oh, using Dr. to address professors is quite rare over here.

Anonymous

(even though they might be having a PhD)

0ßelö7

@dmckee I was an undergrad taking a grad class and had the best grades. Why would I be treated worse than anyone else?

dmckee

7:54 PM

@Blue They are used fairly interchangable at my current place, and I don't actually remember what was preferred when I was an undergrad.

0ßelö7

@Blue I also refuse to refer to people by "Professor"

No one says it anyway, so it works out for me

Anonymous

Is it usual to call parents and grandparents by their first name in the US?

0ßelö7

god no

that's a good way to get your ass beat

Anonymous

Oh, I had a wrong impression then :P

dmckee

@Blue I've known more than a few families where it was 'Grandma Marion' and 'Grandma Phylis', say, to keep them distinct. But not just their name.

0ßelö7

7:58 PM

^ that's how it is in my family

same with uncles and aunts

dmckee

For some reason I had 'Grandma and Grandpa' on one side and 'Granddad and Grandmother' on the other.

0ßelö7

with my godparents I'm on a strict first-name basis now, although my dad still revers to them as Aunt, etc.

Emilio Pisanty

I swear, sometimes I'm tempted to post a thread on meta titled "I would like to solve poorly-posed homework problems set by help vampires and the one I liked got closed. Where can I find similar questions?" and port all the answers from here.

David Z

Well I suppose the question with other site recommendations is the diplomatic way of posting exactly that ;-)

I deleted that (non-)answer BTW

Anonymous

Other than physics forums most of the other sites (in that list) are useless. Even physics forums has lost its shine now.

Emilio Pisanty

8:17 PM

@DavidZ I saw

I wanted to downvote but couldn't

@Blue physicsforums had shine?

Anonymous

@EmilioPisanty In the earlier days the activity used to be much higher

Anonymous

Many knowledgeable users have left

Emilio Pisanty

@Blue =|

I don't recall ever looking at a PF thread and thinking "gosh, that's a useful page!"

Anonymous

Well, it did help me a few times. Those were mostly pre-2012 posts.

0ßelö7

8:40 PM

@dmckee So how would me trying his first name go, approximately?

dmckee

Well, that's the tricky part, isn't it.

Certainly chose a time when you don't have an audience, are working together, and have the attention to space for his face.

But asking just him might be less awkward than a failed trial balloon.

0ßelö7

@dmckee Attention to space for his face?

dmckee

s/space/spare/

You need to be able to watch his reaction.

0ßelö7

Oh.

David Z

@EmilioPisanty I suppose you wouldn't. Forums tend to be more useful to the people actively involved in the discussion and much less so to people who stumble across it afterwards.

at least that's my experience, but I'd imagine it generalizes

DanielSank

8:52 PM

@DavidZ Forums are generally terrible.

3

Chronology is not a good basis for organizing information.

I wasted months and hundreds of dollars because of an error in a mead-making forum that cannot be fixed because the forum doesn't support edits.

Abcd

9:06 PM

Why does the body remain in equilibrium when it's suspended from its centre of mass?

Research effort: Googled and found this When an object is supported at its centre of mass there is no net torque acting on the body and it will remain in static equilibrium.. Similar content is written in my books. I want to know "how" is this possible?

How is net torque zero?

please ping me if you reply to my question above. Thanks and bye.

David Z

9:33 PM

@DanielSank Forums are decent at what they were designed to do, which is facilitating back-and-forth discussion. It's when they're repurposed as an archive of information that they become terrible.

@Abcd I'd suggest taking an example or two of the situation you describe and calculating the torque. I think you will see why it's zero.

dmckee

10:11 PM

@Abcd Strictly speaking is should be "center of gravity", though the two are often coincident.

0ßelö7

@dmckee So seriously, how do I ask without sounding like a complete you know what

this seems very awkward no matter how i do it

dmckee

@0ßelö7 I don't know. I really don't.

Personally I have always been very conservative about that: I've waited until the evidence was stacked pretty high that it would be acceptable.

But I'm a bit of a social dunce some of the time and it makes me risk averse.

0ßelö7

@dmckee so him signing emails with his first name doesn't mean anything?

dmckee

@0ßelö7 It might mean something if he's put that in his signature file (I'd guess that it does and count that as evidence). It probably or even likely means something if he writes each signature himself (stronger evidence).

0ßelö7

@dmckee Hmm

So I've taken three of his classes, and when he sent emails to everyone he used his full name

David Z

10:41 PM

Is this what you're talking about?

23

Q: Is it OK to call a professor by his first name when he/she signs emails by only first name?

If a professor in a North American country presents his- or herself by his/her first name in email messages, does this mean that students can refer to him/her by his/her first name? Or is this generally not a good idea, unless the professor has explicitly mentioned that he/she can be referred to ...

etiquette professors

0ßelö7

@DavidZ Yes, but it has nothing to do with me being foreign

the answers are not applicable

David Z

No, the answers are applicable - just ignore the fact that they're talking about a foreigner. This is not something where being a foreigner or not makes any significant difference. I'm not sure why some of the answers focus on that case specifically.

0ßelö7

"Address him as he addresses you"

what a terrible answer

DanielSank

@DavidZ yeah

Mithrandir24601

@0ßelö7 I'm maybe not the best person to give advice on this (my CS director of studies had us calling him by his first name from day 1 and he's a really senior professor), but the things I've gone with are: anything less than a lecturer is first name, whether or not to call them by first name scales with their seniority (read: size of their office) and inversely with how well you know them and your level (although it does also depend on the person), so personally, I'd probably go with:

if it's related to grad classes, depending on how senior he is, address him by his first name (if everyone else is, anyway). If it's something you've got in relation to being an undergrad, then it's maybe safer (in the meantime) to use Dr. foo

0ßelö7

10:50 PM

I've known him for 2 years now and we're writing a paper. He's senior faculty

No students address him by his first name

No students besides myself and a few others even like him (I think he's great)

So what i think would be weird is suddenly trying to call him by his first name after knowing him for 2 years

> Can I ask the professor what he/she likes to be called? NO. Do not ask him/her about his/her preference. Why? Imagine that you are a medical doctor. You're been in school for many years, trained hard and despite all odds, succeeded in getting your medical degree. You of course will expect all patients, colleagues, interns, residents and others in the workplace to call you "Dr. Lastname."

> It would be odd for one of them to ask you if it's ok to call you something else. If you wanted to be called something else, you would probably say something.

academia.stackexchange.com/questions/45323/…

Why isn't the comment one-boxing?

What's up with the undergrad hate?

Mithrandir24601

@0ßelö7 No-one hates undergrads, it's just that most of them aren't actually all that interested a lot of the time

(although it is nice during summer when things are a lot more quiet :P )

0ßelö7

@Mithrandir24601 I'm one of the undergrads who are around in the summer doing work

I don't understand why there's this magical thing that happens when you're a grad student

I know plenty of them, there's nothing magical

Mithrandir24601

11:06 PM

@0ßelö7 Pretty much agree with this...

It's not 'being a grad student' that makes the difference between first name basis and not, but rather the level you're working at. Personally, I don't see why all students can't call all researchers/lecturers/readers/profs by first name, but that's the way things seem to be

0ßelö7

I'm afraid I'm completely misreading the situation and I'll get some question like "why would you want to call me that"

He likes psychological questions like that

@Mithrandir24601 did you watch got?

@ACuriousMind Is your absence a true absence? This algebra is killing me

Mithrandir24601

@0ßelö7 Yep :)

0ßelö7

@Mithrandir24601 the ending was more explosive than I had expected

Mithrandir24601

Nothing particularly surprising happened, but it was still a good episode :)

@0ßelö7 It's a pretty good way to end the season