The h Bar - 2014-10-25

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3:21 AM

3

A: A force opposing Gravity

My knowledge is limited on the subject but matter is typically prevented from collapsing under the weight of extreme gravity by particle degeneracy. This is what keeps neutron stars from collapsing into black holes and is the result of particles resisting occupying the same quantum states. Ther...

does not seem like a useful answer, unless I'm missing something?

3:32 AM

hey David!

@DavidZ I agree with you

2 hours later…

5:33 AM

21

Q: Using Math.SE as a contest site

This isn't the usual issue about questions from contest competitions being posted here for assistance, but rather about the use of Math.SE as a venue for hosting a "contest" using a future bounty as prize. This recent Question asks for participation according to rules (the post lists seven of th...

interesting...

4 hours later…

10:00 AM

0

Q: “Mass in Special Relativity” misconception

“Unification of energy and mass ”, when explained carelessly, becomes one of the most dangerous heresies. Ī don’t point my finger to anybody, but many otherwise knowledgeable guys easily write a rubbish with roughly “Special Relativity abolished the difference between energy  and mass, hallelujah...

discussion answers reputation

1 hour later…

11:08 AM

@KyleKanos :'( 3.0

11:20 AM

@Jim Disgusting "old boys club" type stuff right here ;-)

(not being serious)

hey @Danu

Hi there!

actually got around to answering another one

Nice :) I really can't find the time or motivation, lately :\

one of the ones I noticed in previous readings physics.stackexchange.com/questions/92919/…

I joined the 2 English language sites earlier... nevr been so nitpicked... won't be going back to either

@Danu motivation has been difficult for me today as well

11:37 AM

Yeah... :\

I have some good-ish ideas for questions though

I have great ideas for questions too... but little motivation and less confidence to post them

So, I write answers

Um, I'm having some trouble getting a good experiment for my school project. Can anyone give me some suggestions?

I have an excellent idea, in fact

@Nick this video video.ias.edu/wam/2014/0516-TadashiTokieda

3

especially the part that starts at 47:00

it's deep

test it

do the experiment he mentions (varying width of the tube-shaped things)

see where the critical point is

it'll be glorious

@Nick what do you think?

11:53 AM

@Danu: Aww, this is really cool. I love it. I think I'll show these experiments to the kids I tutor. They seem very exciting... but academically speaking, I don't think I can make it into a consistent analytical project :(

@Nick ....but this is like... the easiest experiment ever?

you don't have to do the hardcore theory

@Danu: I know, but students in my stream are penalized for projects that do not obey a "standard mark"

aaah

@Nick the standard mark being...?

I have no idea. I missed a week of class and didn't know about the project till a few hours ago.

11:56 AM

so, what exactly do you think is wrong with this proposal?

Infact, my professor had given a list of projects to choose from during my absence from which students chose the best ones. There wasn't project left for me.

@Danu: Nothing. Infact I'd love to do it if my professor allows me to.

then do it! :D Just out of curiosity, do you have a few examples of projects that others will be doing?

um, no but something about potentiometers, capillary tubes and stuff. Just normal highschool lab experiments, you know.

Now, I think he's trying to blackmail me into doing a simple project that no one in my school has ever done before.

But this is exactly it! The physics here is much deeper than any of those other things, I'm fairly sure

and it's so simple to carry out

He's told me he'll give me extra credit for successfully calculating refractive index with a lense lense. I think I should do that. I'm currently on the phone with a few of my group members who are supposed to do the project with me and they've all decided to do it. :(

@Dan: Maybe I'll try some of your experiments for an upcoming science fair :D

12:03 PM

There's no serious physics there, at all (in my opinion). It sounds like the calibration tasks people carry out before they start doing their experiment.

:D Yes, that's exactly what I feel too.

Good ol' high school, crushing the spirit of science since always.

3

@Danu: I'm definitely going to put up an experiment from that video in an exhibit I've reserved at my school's science fair :D

It might spark a bit more interest in Physics :D

The rest of the video is also top notch, of course

@Danu: Btw, do you by chance know how to do that calibration thing?

12:07 PM

No, I'm a -10 at experimenting (and I don't care about calculation indices of reflection, to be honest)

The only relevant source I can find for that experiment is a cruddy youtube video

I haven't started studying optics yet. So, this will be different.

Do you know where I can find a paper on this topic?

@Danu not the way I teach it...

@Omen :) I hope you're successful in doing it right, although I have thought about these things enough to realize how hard it is - balancing the interests of the many vs. those of the interested, etc...

my classes encourage individual enquiry

we're all not that bad

Indeed good @Omen

12:21 PM

recently, 3 of m former students got their PhD

in what?

microbiology, genetics and astrophysics

nice

18 more are on their way

how do you encourage individual enquiry?

12:30 PM

questoning, within a contextual framework (keeps the state happy), providing training in the scientific method...

The only teacher that ever talked about the scientific method was my philosophy teacher.

I am not the only teacher who teaches in this way...

I don't doubt it, I'm just saying you are not the norm in my experience ;)

ironically, we are maligned more though

Who maligns you? Other teachers?

12:36 PM

we are maligned by the public and students for the perception mentioned in this chat, and we are maligned by some other staff and our bosses for being 'renegade'

most leave teaching within 5 years.... I have been doing this for 15 years

but I am burning out fast

use this web site as your refueling station my friend :-)

it does have potential

@IceBoy Exactly :) Here, you can vent and/or talk about more interesting stuff!

Well, that's how society works. Sometimes people can be frustrating.

teaching is my 'bread and butter' - I do try as a teacher - but like just about every teacher, we are lowlives

Also, it's quite exceptional to find a high school teacher who is also actively publishing original research

3

12:40 PM

But they can be amazing if given a chance

@Omen: You are a teacher, not a lawyer.

@Danu: Indeed it is.

I have to admit that I, personally, would never teach high school kids - sorry!

I am a high school teacher and a practicing atmospheric radiation physicist

@Danu: Because of the tiresome work which bears little fruit, right?

@Omen: ... the atmosphere is radiating something? whoa.

@Nick I have never felt fulfilled nor respected as a teacher, not even close

@Nick UV radiation in the atmosphere

@Omen That's exactly what I am afraid of...

I just don't think there's a lot of fun in (1) the social situation @ high schools (for teachers) and (2) force-feeding a lot of utterly disinterested kids some physics knowledge

The only joy is, presumably, in that one student who really cares

...but from personal experience I know that those are rare, and hard to spot

12:48 PM

I've accepted the fact that regardless of the effort I do, as a teacher I am scum to students, to admin and to the public

Perhaps it's different in your school, but in my school, the good teachers were actually respected by most students and parents.

@Omen: I may not know what real teaching work may feel like but I do teach a bunch of kids some basic lessons on science and maths and from my experience, I can honestly say, kids will never understand something entirely during a class.

I am aware that not everyone understands everything in class... I give up all lunchtimes and have morning tutorials

@Omen: Why do you feel not respected? Are you one of those happy go lucky lecturers who ignore the noise in the back and remain silent when a monkey child sits on your head?

Students tend to don't tell the teachers how good the lessons they give are, though

12:50 PM

@ACuriousMind Are you sure you're not coming from a biased point of view? There are always some people who see the value of a good teacher, but I'm very skeptical about the question whether this set is dense ;-)

In fact, I'd venture to conjecture that the set of people appreciating high school teachers is of measure zero.

3

I am a strict teacher, but not over the top -I do not yell, nor lecture - but the students know the rules, they also know that I will do everything I can to help

In my experience - even neutral recognition is rare

being told what we do wrong is very very common

@Danu Of course I am coming from a biased point of view, I was that one student. :D But, for example, we had two low-level math courses, which were obligatory for those who didn't want to take the upper-level course. They had two different teachers - one was an unfriendly incompetent idiot and the other was one of the best math teachers I ever had. The people from the former always complained about the lessons. The people from the latter never complained about the teacher himself.

@Omen: Different societies, different kids, different minds, different attitudes. Maybe you've been vegetating in the same patch of garden for too long? Is that a possibility?

nope, have worked in two countries, and in 9 schools in different environments

you can't please all the people all the time

12:54 PM

@Omen A true veteran

@ACuriousMind: No matter how much you think you were interested during a lecture, there will always be someone more talented and more skilled than you who is capable of being more interested if put into your shoes.

@Nick LOL - but this is not really the point

@Danu: Nah, the point is biased, blind and part of a delusion.

@Danu just a teacher aka lowlife to too many

I am working to leave the profession

@Omen but do you sometimes encounter some student who does appreciate your efforts?

12:57 PM

@Danu not really

@Omen: Sometimes helpful people are the ones that get stomped on. You are just too nice or maybe you're too strict.

@Omen ...then it sounds like maybe it's a good thing that you're considering to stop doing it. The joy has got to come from somewhere, else it's just not worth it

Or most likely, it's not your fault at all

@Danu: The purpouse of life is not to be happy, it is to be useful.

@Danu ever since I was punched in the face by a parent, teaching is just a pay cheque

@Omen: And why did that incident occur, if you don't mind me inquiring?

12:59 PM

@Nick Hah! And you speak of delusions?!

@Danu: I never said I was Delusin-free. I'm just saying we all live in a delusion but the best thing is we can choose what that delusion is :D

@Nick I was accused of teaching the wrong course

@Omen OMG! did you sue?

and 'stomping on their child's dreams'

@Nick I choose to remain in the one where happiness is what one strives for.

@Omen Ouch! Did you fail the kid on some test?

1:01 PM

@Nick That is the most horrible statement I have ever heard.

@Omen: What the cuss?

@Danu no, they earned B and above

@ACuriousMind Quite reminiscent of some literature on dystopian regimes, in fact :D

@ACuriousMind: I make a lot of horrible statements. You have to be specific.

that student graduated as dux of the school and has completed their PhD

1:02 PM

@Omen but... what was wrong, then?

@Danu the father admitted he thought of teachers as scum

and the child disliked having to do homework (that they turned out to enjoy)

@Omen ...wait, was this the incident where you got punched? I don't get it... it doesn't sound worth punching someone over?

@Nick I linked to it: "The purpose of life is not to be happy, but to be useful" It runs counter to everything I believe makes life worthwhile. If you find joy in being useful, then be useful. If you find joy in living in a barrel off the scaps of others, then do it. As long as you respect your fellow creatures, the pursuit of happiness is the only thing that makes life worth living.

@Nick By the way, by pressing on the little arrow next to the statement of someone's reply to a comment of yours, you can see which comment of yours he was replying to, exactly

Oh... @ACuriousMind beat me to it

@Danu: ah, sorry, I never got used to that feature :D

1:05 PM

@Danu it is just a case of people hating teachers

people hate cops too

(sorry if that sounds like trolling)

yes, but cops have a lot of respect too, teachers do not

my dad was a cop

because they have guns

@Omen In my book, teachers >>>>> cops

@ACuriousMind: I stand by what you say :D I was just trying to make a point that happiness, as we often see it, isn't what life should surmount to. If you want to be happy, try injecting some serotonin and dopamine into your body.

1:08 PM

@Danu in my experience, dog crap >>>>>>>>>>>>>>>>>>>>>>>>> teachers

...I somehow feel like some countries have a very unhealthy tendency to idolize people associated with militarism (soliders, cops, ...)

@Omen: No, do not bring a gun into the classroom, sir. Big no no!

@Nick of course I would never do that

@Nick No, because that doesn't work - happiness is mostly a mental thing. You'll feel like crap about doing that soon enough, so it'll achieve the opposite. The crux is that you must keep yourself content

@Omen Ah, come on. Don't get yourself down like that. You're being a little too extreme

so, at the moment - teaching is a pay cheque (still will do my best), research continues in my own time and self-funded

1:09 PM

@Danu: Mentality is a chemical thing. Have you never noticed how people change drastically when they're dehydrated?

@Danu it is as my experience

@Nick `Yes, but one cannot afford to continuously inject chemicals, or is that what you're suggesting?

@Omen why not teach college?

@IceBoy not that simple

@Omen: Firstly, I know a lot of teachers who get students pouring down in front of them asking for blessings. $Parents \equiv Teachers \equiv God$

1:11 PM

community college students would be more respectful

i'm not saying apply to the ivy league :D

not possible where I am

@Qmechanic hey! Did that trackback feature indeed get added? I think I just saw a trackback on this paper from physics.SE!

@Omen: That's society's view of teachers, btw. You cannot be made down by a few crackpots who had bad experiences with their teachers in childhood. If you are affected, others are affected.

@Danu That's the old trackback from TP.SE before it was closed

@Omen move to where it is possible

1:14 PM

in Australia, getting into a University to teach is extremely difficult

PhD won't cut it

you will be happier at a community college

community colleges don't exist in Australia

@IceBoy That's a US thing

how about technical institutes?

need a different qualification here for that

1:17 PM

work towards getting that qualification

@ACuriousMind Scheisse!

LOL

@Omen Mostly, you should do whatever you want

You're missing the ß, though ;)

As I'm sure you're aware, a negative attitude towards your job is quite unlikely to improve the situation!

1:19 PM

@Danu need money to do that - teaching pays... research, at this atage, does not

@ACuriousMind Nah, I'm anti-special-letters ;-)

I have heard that time and time again

@Danu I've gathered a lot of weird looks for saying that at times - it seems doing what you want is a things hippies and dreamers do :P

Also, let me just say that this is by far the most interesting chat session in a long time!! :D

it is fun :D thanks for coming @Omen

1:21 PM

@ACuriousMind Many Germans seem to be misguide in this respect, at least the theoretical physicists

...it's probably just the theoretical physicists :P

??

@Omen ...the implication being you make the chat interesting

@Omen How are you able to do research at all in your situation? Do you have a lab to use? Or do you not need that much?

@Danu Nah, it's society. Be a nice little cog in the machinery! Don't you dare thinking that the world can be changed, and don't you dare being unhappy with all that you have!

(Especially the last one. "Uns geht es doch gut" is the one sentence I have learned to loathe)

@Omen how about teaching elementary school students? i'm sure when they are that young they respect their teachers :P

@Danu hmmm, I see

@ACuriousMind self funded and my work is field work - any equipment I either borrow or build

1:26 PM

@IceBoy They fear them. Or they love them. It's different with little children.

@IceBoy would need a separate qualification to be allowed to do this

icic

@ACuriousMind It's not at all like that where I'm from

@Danu not sure how to take that...

@Omen In a good way :D We all love people complaining about their jobs ;-)

1:32 PM

i see

@Omen More seriously, it's nice to have a discussion about these serious issues (teachers etc etc)

56 mins ago, by Ice Boy

use this web site as your refueling station my friend :-)

To relax, I research and answer questions - it makes me feel marginally less useless

answers like physics.stackexchange.com/questions/92919/…

you certainly have given me some interesting food for thought...

that and the research that I do (got published again recently)

1:39 PM

@Omen Man, it's gotta be so awesome to have something published!! I can't wait till I manage to do something original for the first time in my life!

@Danu this was no. 8

@Omen :) :)

This question deserves a long and rigorous answer, but I'm not comfortable or motivated enough to write one.

Hah, dat timing, @ACuriousMind

@Danu ...he said seconds before I posted a short and non-rigorous answer :D

@ACuriousMind yeah... I would like to see a more thorough discussion

I'm interested how well the 'usual' argument invoking Heisenberg holds up under close scrutiny

I feel it is not worthwhile to discuss virtual particles "rigorously" - they are artifacts of perturbation theory, and I cannot see how discussing them contributes anything other than confusion about what is measurable (and hence existent) and what is not.

1:44 PM

@ACuriousMind I feel like they are, precisely because they are so well-known, also outside the small circle of actual scientists.

This would be a candidate for the canonical answer category that I was on about a month or so ago

[I feel terrible for not following up on that, but I just don't have the energy]

tough to answer to "a middle-school student"...

...10-13 years old?

Essentially, all that happens when people talk about virtual particles is that they forget that Feynman diagrams are just diagrammatic ways to write down integrals. That they have been popularized above all else is a failure of science journalism

@IceBoy Keep in mind, the OP is not the (only) reason you're (supposed to be) answering a question

@ACuriousMind What has always made me wonder about it, though, is that it seems that Feynman himself was also fond of using this method of explanation

What could have been his reasons for this?

@Danu true, but I'm no Feynman :(

@IceBoy I mean to say that one should not be afraid of answering a 'basic' question with a high-level, technical answer if you feel it is a good way of adressing the question.

1:51 PM

icic

btw, I saw that the Feynman Lectures have been redone in the original audio :D

@IceBoy Audio?! Where?!?!?!

at the caltech site

Link?

let me search...

Speaking of Feynman lectures...

1:57 PM

My greatest pride ;D i.stack.imgur.com/RPrIb.png

5

@Danu You corrected the Feynman :D

Fuck yeah! An original error too, not even a printing mistake! :D

Even if it was only a sign error, I still feel like a boss (plus I'm on the contributor list!)

nice!

@IceBoy ah... it's not open access :\

2:03 PM

:/

itunes.apple.com/us/book/six-easy-pieces/id572144556?mt=13

2 hours later…

3:46 PM

@ACuriousMind ah, I'll delete that part of the question - it's too easy I think

@Danu Have you seen the explicit calculation that shows that $D(p_0^\dagger)$ is bigger than $D(p_0)$?

Yeah

I deleted that part of the question

I somehow mustered some hope that there is a physical reason why this happens

but that is probably not a well-defined question

however, the second part remains interesting... (right?)

Actually, the argument that we saw was not quite an explicit calculation IIRC

The argument I have seen is the following:

With "explicit" I mean that you use integration by parts to conclude that $D(p_0^\dagger) = \{\psi \in \mathcal{H} \vert \psi' \in \mathcal{H}\}$.

let $\mathcal D(p)=\{\psi\in\mathcal H \,|\, \psi'\in \mathcal H\}$

we can show that $p$ is closed and that $p_0=p^\star$

Yeah, probably we're talking about the same thing

3:51 PM

...and then it follows

But the point about the square well is interesting - it seems we must admit non-physical boundary conditions to get physical momentum

because $p_0\subset p=\overline{p}=\overline{p}^{\star\star}=p_0^\star$

but $p$ is a true extension of $p_0$, so $p_0\neq p_0^\star$

@ACuriousMind Right..? It seems so strange! Especially since this is the canonical example of how to use QM...

(corrected typos in earlier messages)

btw you may consider deleting the comment on my question

@Danu I already did :)

Btw, who favorites like... almost every question?

@ACuriousMind do you know of a way to track down which comments of mine received many votes? I found this thing which allows me to see how many comments with how many upvotes I have, but I want to know which are the popular ones!

@Danu Nah, got nothing for that except going through them by hand

4:05 PM

brrr

I've got several hundreds of them.

@Danu That I wonder, too - and often, they don't even vote the question up

@ACuriousMind my best guess is that some people use it to 'bookmark' a question if they want to look at it later...

Hm...I fail at SQL

I seem to have created a query that lists all my comments scores, but not the comment text :D

I have a comment with 38 upvotes, but I don't know which it is

That's already done by the link I provided!

I have 2 with 13 upvotes, 1 with 10

I'm curious!!!

@Danu try this one

4:17 PM

@ACuriousMind Even more agonizing! It displays the first part, but not the entire comment!

Oh, actually switching to the 'graph' tab fixes this

You can also use the PostID to visit the post and read the comment in context

Thanks :D

There's probably a much better way to do this, but it works :D

@ACuriousMind How do I find the post, using the ID?

@Danu "Just" put the number behind physics.stackexchange.com/questions/

4:21 PM

Nice

This question was a goldmine for my Pundit progress :D

1 hour later…

5:37 PM

...why would anyone downvote my question??

Also, damn, I'm really dominating the starred-comments bar right now :D

(secretly) proud

6:19 PM

Hm, it seems I'll run out of close votes again today. Are fewer people voting these days, or are there more questions coming in?

6:53 PM

@ACuriousMind there are a lot of questions, I feel

Aaargh! I have fallen victim to 'user removed' :(

That guy gets us all sometimes

Inescapable, like death and taxes

1 hour later…

8:06 PM

Do you guys know of any good resources on dimensional analysis (applied math). I'm mostly searching for problem sets and some explanation of how to reduce PDEs to ODEs?

8:27 PM

I wasn't aware that being Socrates is a bad thing now...

1 hour later…

9:49 PM

@picaposo Dimensional analysis is quite elementary; you will not find textbooks dedicated to this technique, which can be taught in a few pages of text without much effort.

roflmao

Hello people

-3

Q: How to find the moments of A and B

1) A 4.5m beam of weight is 1200N, supported by two points pivots A and B. A is x metres(m). Determine x, given that B is twice A

homework statics equilibrium

You should really upvote that one back to 0. The comments need to be saved. Hilarious :)

(Community bot will clean up -3 and lower questions after ~1 week)

Hah! That's great...or terrible. Or both.

we already pinned/starred that in WordPress.StackExchange chat. Makes may day - every day :D

ok, have a nice evening!

Hmmm...let it be deleted and another reason to reach 10k ;)

@Danu Uhhh...why would one go and ask physics questions on the internet if one is still too angry about a football match to reason calmly?

10:11 PM

@Danu Yeah I kind of picked up on that. Do you know of a good set of lecture notes then that I could make use of?

10:32 PM

@picaposo Not really, to be honest. It seems to be something one picks up 'on the fly' over the years...

11:27 PM

@kaiser not to worry, I have a screenshot

hehe

wow, that is hilarious!

Terry Bollinger

11:50 PM

@Danu, from earlier, I think it would be safe to say that Feynman didn't just use virtual particles, he really did think that way. It was mainly Dyson who later cleaned it all up for Feynman and made it mathematically rigorous. Feynman did not think in integrals.

(Terry likes to talk to people he knows are not here, heh!)

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