The h Bar - 2014-09-30

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12:13 AM

@Waffle'sCrazyPeanut DO YOU HAVE ANY MORE INFORMATION REGARDING THE TESTICLES?

@DanielSank Mind filling me in on this??? lol

@Danu: Regarding the discussion I was having with David Z. There is absolutely nothing whatsoever in that question which explicitly asks "what does this physically mean?"

To interpret it in that way, one is projecting one's own interests/perceptions. This is natural and good. We should do this. My point here is that since we do this for some questions, we should be willing give the same benefit of the doubt to all questions where there is room for interpretation. The alternative self-consistent approach is to put all questions which lack an explicit well defined question on hold.

@Danu: And by "that question" I mean the one about the diverging integral.

You noted that the question turned out to have a positive influence and that you learned something. Note that this was due to a good answer which arose despite the fact that the question was not well worded (@DavidZ agrees with me that the question was not well formed).

The point here is that despite a poorly formed question, a good answer made it worth all our time. This supports the argument I made in the meta (meta.physics.stackexchange.com/questions/6135/…) that we should judge questions by whether or not we can expect a useful answer, not necessarly by whether the question fits exactly into the admittedly imperfect rules/policies.

hi

Hey @DanielSank - I have started aswering questions now

12:28 AM

@Omen: Hi. My gf says she doesn't know much about low wavelength CCD detection, but she pointed out that your SNR drop could actually just be lower signal, not more noise.

quite possibly so

@Danu: You are giving the diverging integral question the benefit of the doubt by assuming it's asking about a concept, and you should give the same benefit of the doubt to other similar questions.

@Danu: Regarding your other comment "mind filling me in on this??? lol"... what are you asking about?

hi @DavidZ!

@Danu I agree with that, my argument is that it's not clear what exactly it's asking.

hi @Danu!

12:30 AM

@Omen hey, actually I'm just stopping in briefly

@DavidZ no worries, have started answering questions

@DanielSank I don't have time to get into details now, but a brief counterpoint while this is fresh: our rules about questions need to be motivated by more than just which ones will accumulate useful answers. We need to encourage the kinds of questions that will set a good example for future askers, for instance.

hi @Swetank!

And bear in mind that the rules/policies are crafted as a response to what kinds of questions the community judges to be good for the site. They're not handed down from some higher authority. (Mostly. A few rules do come from SE but they're not the ones at issue here.)

@DavidZ: That's fine. I'm just pointing out that @Danu's argument is that 1) The question was asking about a concept. I maintain that it was not explicitly doing so and that users gave it the benefit of the doubt. 2) It's good because there was a good answer. By that logic we should allow other similarly ill-formed questions.

12:35 AM

@DanielSank gotcha, fair enough.

@DavidZ: Sure, we make the rules, but my perception at this point is that often people don't really defer to the rules but to their own inclinations, which is confusing.

@Danu in Soviet somewhere, testicles have information about you!

What's with the testicles thing?

yeah, who had the balls to start that?

o_O

12:36 AM

lol

had to get that pun in there...look at some of the starred comments -->

wahaha, "homework question downvote YOU!" Amazing.

had to put that somewhere

@Omen Hello!! What you guys are upto?

@Swetank i am sitting here in my pyjamas embracing the madness ... and posting questions and answers - what about you>

@Omen Ahh! I am stuck with a physics problem .. actually its mathematics .. its frustrating!

12:43 AM

@Omen: Ha! You're addicted. This is good. Feel the physics flowing through you.

@Swetank: What is it? I like math.

@DanielSank is that what it was?

@Swetank do tell!

@Omen: Is that what what was?

@DanielSank likes math

@DanielSank the physics flowing through me, I thought it was my pain medication... it felt fuzzy

@Omen I am preparing it .. wait a minute!

@Omen: Oh. Nah, that's physics. Trust me, I'm a doctor.

omg that's actually true now. Holy cow.

12:48 AM

hey, so am I! well a physics doctor.. and yes, the holiest of bovines

@Omen: Heh, indeed.

@Omen: Do you have a minute to talk about our lord and saviour Bessie the cow?

lol, I think I ate her

@Omen: I hope it was worth it.

tasted like chicken

Schrodingers chicken... either it tastes or does not taste like chicken...

I wonder what would happen if you taste it in a rotated basis.

12:56 AM

quantum chickens!!!

@Omen Here you go: docs.google.com/drawings/d/…

@Swetank looking now :)

@Omen take your time :)

are you wondring why the answer is 0.987 rather than 1.013?

oh wait, are you asking why the necessity to invert the answer in the first place?

1:12 AM

@Omen Yes, but also the ratio should be of Kalka / Simla ? at first why its inversed Simla / Kalka?

it is odd that they did that - i just did the calculation for Kalka/Simla from the start and got 0.987

the reason they did that could be the way the question is worded, with Simla mentioned first

@Swetank does what i said make sense?

I too did for Kalka / Simla but answer is nowhere around what you got.

hhmmm lets me see again

Mine for Kalka / SImla : 1.246

yeeks!

it should be a case of just inverting all the values in the working out step

1:18 AM

I did (76 * 288) / (308 * 72) = 1.246 which is Kalka / Simla

@Omen didn't get you!

@Swetank I did that also.... (76 * 288)/(308 * 72) = 21888/22176 = 0.987

@DanielSank can you confirm my calculations?

@Omen Its correct.. I had confused it with my calculations.

no problems, I do that all the time

the trick with that question is how it is worded - note they mention Simla first, then Kalka, then when they ask for the calculation, they switch the order

Its late and i am all screwed up.. I should take some rest! :)

@Swetank good question though

@Swetank there is no harm in clarifying! Sounds like you have been working hard!

1:27 AM

@Omen THank you! for support! I appreciate it.

@Swetank anytime at all! am very happy to been of help

@Omen Its a long journey .. never ending purpose and process! :) Thank you!

@Swetank and a heck of a lot of fun too! am still on that journey myself - loving it

you should get some rest!

@Omen What are you upto? I am clearing my high school. Definitely it fun!

@Omen: Yeah, one second.

1:32 AM

@Swetank I have recently finished my PhD in physics (atmospheric radiation monitoring)

but for my day job, I am a school teacher

@Omen Yeah packing up my work! have to keep things arranged .. so that I can find them easily when wanted. :)

it is indeed an excellent habit to be organised.... my desk, however, looks like a herd of marauding camels have performed a strange ritualistic dance on it

3

@Omen: Oh, that's awesome. Teachers are the best. I dedicated my thesis to teachers.

Ok, so: $\rho_A / \rho_B = (P_A T_B)/(T_A P_B)$

@Omen that really sounds cool!Atmospheric radiation monitoring. That's really interesting!

@DanielSank I try to be one of those teachers who always gos the extra mile - giving up my lunchtimes for tutorials

1:34 AM

@Omen Sharping up skill is a good thing! :)

Why doesn't math show up right for me.

?

@DanielSank that's cool, we got it sorted - such is our power

@DanielSank doesn't show for me as well - i blame the chickens

@Omen, @Swetank: I got 0.987, in confirmation of Omen.

@Omen Hahah..! Often i am upto that category!

@Swetank I think the camels are still on my desk...watching me...

1:37 AM

@Omen: Camels are awesome.

@DanielSank Finally case solved!

@Omen: Giant feet so they can walk on soft sand without sinking. Also really long legs to keep their bodies away from the hot ground.

@DanielSank they are indeed, even if they are dancing on my desk

@Omen: In Lawrence of Arabia, there is a scene in which the Arabs charge at Aqaba. When filming that scene, Peter O'Tool fell off his camel.

@DanielSank evolution wise, they are indeed remarkable creatures

1:38 AM

@Omen: The camel stopped and stood over him to protect him and prevent him from being trampled.

they are intelligent and protective creatures too

i like that story, probably because I really like the movie :)

@Om

@Omen @DanielSank Thank you guys once again for helping out! I hope you have a great day! Finally my pillow is waiting for me.. Good Night! :) Pray, so I got dreams of camels. :)

@Swetank happy to help! Have a great and well-earned nights rest!

@Omen: Thank you for being a teacher.

1:51 AM

I appreciate that!

@Omen: We're trying to "contract" some of our machining work out to a local high school which has a surprisingly awesome machine shop. I hope it works.

I hope that works too - any industry/university collaboratons with schools are the best

I am hoping to get an Engineering collaborative elective running - Middle Years + 1st year students

hmmm tempted to search and write my 2nd answer

hello @KyleKanos!

Hi

how are you?

Doing well. Yourself?

2:03 AM

pretty good - have a day spare, so are scouring the site answering what I can

what do you do, @KyleKanos?

Don't be afraid to answer questions with answers

Sometimes new insight is better than rep

@Omen I'm a computational astrophysicist, specializing in supernova remnant evolution

@KyleKanos that sounds epic!

@KyleKanos that is very true

I like the mental challenge of researching and answering questions

Plus there's people who watch the main page for new questions (shows Community bumped Q's plus any edits or updates to any question), rather than the /questions page.

@KyleKanos by the way, I am an atmospheric radiation physicist (and a school teacher to pay the bills and recruit more physcists)

@Omen: Yes, if they can be turned, they will be great assets...

2:11 AM

@DanielSank I still do research for the university, but as an independent researcher - I rope the students, their parents and even the principal into the experiments

@Omen: That is good. Hands-on experience is severely undervalued in my country.

same here

i get no funding - so my research is self funded and lets just say the hardware stor knows me very well

@Omen: One thing I think a lot of people don't understand is that the 12 years of schooling you get is almost entirely theoretical in nature. I don't just mean in science. Everything is from the book. It's important that people build things.

@Omen: Wow, good for you for doing that.

@Omen Wait...did you change your name from something else?

Why does everyone keep asking him that?

2:14 AM

@DanielSank Because there was someone here a few months back who has the same exact background...

@KyleKanos nope, am new - but as I explained to another member earlier, I am a friend/colleague of someone who used to be a member

we are within the same research group, several of us are teachers

The guy I knew asked this question:

11

Q: What is the current physical theory of what causes the 'Morning Glory' roll cloud over Northern Australia?

The Morning Glory roll cloud (pictured below): from this Wikipedia page, which briefly describes the landform and meteorological causes, but states The Morning Glory cloud is not clearly understood because their rarity means they have little significance in terms of rainfall or climate i...

atmospheric-science

@KyleKanos: Ah.

and we are all self-funded for the most part

Didn't realize he left though

2:16 AM

nice question

he went through a very rough time, but is okay now - stationed out in the desert - he suggested I join

I see

Well tell him that I said Hi

will do so!

@KyleKanos, I see on your profile, you are finishing your PhD - how long do you have to go?

I'll be done in May

Actually, hopefully before then

But I'd do the walking then

it has got to be a good feeling almost being done

I'll feel better when it's all over

2:23 AM

I know that feeling - once it is done, the feeling is unprecedented releief

I am currently teaching myself about the indirect bandgap and similar properties of silicon

@KyleKanos: note that after you turn in your thesis and you think you're all done, you will get an annoying email from some bureaucrat asking you to fix some stupid margins somewhere. Note also that there is a LaTeX stackexchange.

My university has a Latex CLS

If I have to correct some margin error, I'm going to tell them it's not what the CLS says

I had a paragraph stating the importance of a semi colon instead f a full stop

@KyleKanos: My university "has" that too. It was a total nightmare and I didn't use it. Have you tried it? Also, reasoning with bureaucrats doesn't work.

My draft is using it

Looks like what other people turned in

And my officemate just graduated in August, she didn't have any issues using it either

2:37 AM

that is good news

@KyleKanos: That is excellent.

here in Australia, we don't do a defense, we get our thesis peer reviewed - do you have that as well?

I have to defend it before my committee.

@Omen: Not really. We have a committee which "reads" the thesis. We then give an oral presentation after and during which the committee can ask questions and make us feel stupid.

that has got to be unnerving

2:40 AM

@Omen: For me it wasn't actually. The one thing I'm comfortable saying I do well is give talks (and know what the hell I'm talking about).

I think the idea is that at the point you're defending, you ought to be expert enough in the field to answer the questions easily enough

@KyleKanos: Bingo. If you fail your defence something is wrong. No adviser wants that.

that's a very good point

how long from defense to completion?

@KyleKanos: But you'd be surprised. Some people really get stuck on some questions. People are generally not good at thinking on their feet. It's just not a thing humans are good at.

@Omen: ?

"completion"?

well, completion of the degree

2:42 AM

Typically the defense is in the semester you graduate

So the Dissertation is submitted to the committee a week or two in advance of the defense

Then you defend & graduate whenever is bureaucratically allowed

@Omen: At least! Most people want more time than that, even though they don't actually read it.

@Omen: Yeah, while KyleKanos said.

*what

excellent- with peer review it took up to 3 months to get feedback and then do the fixups (as one would for a peer reviewed paper), then the Dean of Research gives his nod to it and then it gets bound... then 6 months later you graduate

@Omen: Ack!

@KyleKanos sounds far quicker than the peer-review method

It does sound much quicker

2:45 AM

and I have to say, the waiting for the feedback was insane

I am thinking of an analogy to ripping abandaid off

Defense sounds like a quick, relatively painless and efficient procedure

wheres peer review dragged on

@Omen: yeah, it was painless and very fast.

dang, I wish I had the defense - waiting for peer review sent me crazy

@Omen: You seem to have recovered.

yes, for the most part - a bit worrying about the dancing camels and quantum chooks

@Omen: Chooks?

Whazzat?

2:50 AM

chooks =chickens

too many syllables

2 hours later…

4:51 AM

0

Q: Kinematics is much more difficult than it should be

Just to clarify, this is not a homework problem. I'm using this for some code I'm writing for a simulation: I'm trying to find a point at which I should switch from a positive acceleration of a certain magnitude to a negative acceleration of the same magnitude, given an initial velocity. Basicall...

Off topic? I think it might be, but the lack of close votes gives me pause.

@DavidZ: Definitely not off topic IMHO. At least, not when compared to other acceptable questions on the site.

It's as much a physics question as all the stuff asking about how to work some particular interaction term in a field theory, etc.

BTW, isn't allowing the presence/absence of close votes to influence your own votes kind of not good?

@DanielSank don't compare it to other questions on the site, the issue is, is this question off topic on its own merits? (for being low-effort homework-like, by the way - of course it's about physics)

Oh, for low effort...

@DanielSank not when you're a moderator

@DavidZ: Oh. so you can only close or not close? No voting?

4:57 AM

Yep

Since mod close votes are binding, if I'm only 40% sure a question should be closed, I'll want to wait until 3 other people have voted to close. In a manner of speaking.

@DavidZ: Ah. Well anyway, it's not like super high effort, but it's not that bad either. I mean, it depends on where we're setting the bar.

If not for that, then sure, I'd vote to close without regard to how many other close votes there are.

@DanielSank yeah, that's why I put it here to bring it to people's attention

So when I referred to other questions I do that because the written law isn't really clear. It seems better to me to compare to existing cases. You know, precedence and all that.

@DavidZ: Look, if the close/hold message were more useful I would say put it on hold. The problem (as I mentioned before) is that it just kind of says "this doesn't show enough effort." That reminds me of when I used to lose credit for not showing enough work.

It's like, well what the heck do you want me to show?

You know, I just had an idea.

Is it possible to require that at least one person writes a comment before a question is held/closed?

It's possible in that the SE team could implement it, but you'd have a tough time convincing them to do so

Ah.

5:01 AM

Incidentally, the whole reason these site-specific close reasons exist is that we used to leave comments when closing questions, but they wound up being the same few comments 95% of the time

That might be a useful practice despite not being required by the system.

Right, I get that.

Most of us usually do that when it seems like the OP might take an interest in salvaging the question.

The issue is that it probably leaves some folks mystified. Might be nice to get at least one specific recommendation on how to improve.

Ok, if that's really true then that's great.

Anyway, I wouldn't close this one. I would put a comment pushing the OP to elaborate.

well... but pushing the OP to elaborate is exactly the reason closing exists (and the reason it's now called putting "on hold").

Yeah, but the message doesn't give the OP any advice on how to do better.

I get what you're saying.

5:05 AM

It does, though - the homework policy gives a lot of guidance about how to improve a homework-like question

I mean, while there's no explicit question, it is really obvious what he's asking.

How the heck do I type math in here?

user54412

@DanielSank use $ signs like on the main site, but it's not supported natively - you need a plugin

user54412

78

A: Should chat have TeX support?

I will leave the original post for historical reference, but as mentioned in the Update below, all four bookmarks are located on this installation page. There are four bookmarks: start ChatJax installs MathJax and starts a loop that renders $\LaTeX$ as needed. This is intended for use in chat, ...

user54412

maybe?

yeah, I read that. How does this work, I go to the link?

That question gives four links...

user54412

5:08 AM

I lot of regulars here have it installed, but I don't so I can't really help :/

$\int$

This sentence: "Essentially, I'm trying to find $p_{\text{switch}}$ in terms of $p_i$, $v_i$, a, and $p_{\text{tar}}$, given that $v_f$ is 0" is a pretty clear (albeit implicit) question.

I commented telling the OP the explicit is better than implicit.

@DanielSank go to the installation page and follow the instructions there. Basically you drag each of the links to your bookmarks bar.

(actually you only really need the "start ChatJax" one)

Right, I did that and it sort of works.

then you have to click it after you load the chat room

could i ask if I have written this reply physics.stackexchange.com/questions/81658/… to an acceptable standard?

5:12 AM

@Omen: Nah, it's terrible.

@Omen: Joking. It's extremely well written.

lol

i am becoming a bit of a perfectionist with my entries

@Omen: That is a good thing. I'm glad you're a teacher.

user54412

@Omen Can I ask (while being lazy - I haven't yet read the links) is "solar tide" just any regular forcing or does it really mean the tidal effect of the sun's gravity?

it appears to be a tidal effect

user54412

When I hear "tide" I think gravity, but as the pressure variations seem to be driven by the sun I feel like I'm missing something

user54412

5:15 AM

like, the moon's gravitational tidal effect is stronger than the sun's

user54412

like, if they were driven by the sun's gravity, there would be an even larger semidiurnal component driven by the moon's gravity

the references refer to it as a 'thermal tide'

@ChrisWhite precisely my thought when I started to read up about it

user54412

(side rant: am I wrong to think the poor soul here is going to end up way in over his head? or at the very least is going to miss out on all the wonders of physics because he was told there are no physics books worth reading not written by mathematicians?)

he should get into some experimentation and derive the proofs himself!

In Soviet somewhere, experiments prove YOU

@ChrisWhite: The only thing that can save him is something like Shankar's quantum book which blends math and physics really well. That and actually doing some hands-on experiments.

user54412

5:22 AM

@DanielSank I used Shankar - not too bad (and I generally have a very low opinion of all textbooks)

@ChrisWhite: Hee hee, I know what you mean. Shankar is probably the best intro level book I know of.

I like that the first ~100 pages contain no quantum mechanics.

user54412

Also, I definitely remember my sophomore lab courses as being some of the best classes I've ever taken or even heard of

textbooks are very good for holding up a crooked table leg

@ChrisWhite: Ah, lucky you. The lab courses at my uni were aweful.

*awful

user54412

@DanielSank you can edit messages for a short while you know ;)

5:24 AM

@ChrisWhite: Ah! Didn't realize that. Thanks.

user54412

just click the arrow to the left that appears when you hover

yeah, I see that now.

user54412

My undergrad was big on theory, and the physics department was full of mathematicians who aced every class because honestly undergrad theory can be done by blind symbol manipulation.

@Omen: Textbooks can be wonderful things. I learned so much from Reif's thermo / stat. mech book. It changed the way I think about more than just thermo and stat mech. The same is true of a particular math book I once read...

user54412

But the labs weeded out the true physicists -- even the theorists - from the symbol manipulators

5:26 AM

@ChrisWhite: That's awesome. Lucky you.

I didn't learn to physics until I got to grad school.

@DanielSank admittedly I am thinking of writing my own textbook

...and it was rough because I was so ill prepared for the lab.

@Omen: Haha! Yes. Turn to the dark side.

mine will have so many bad puns

user54412

@DanielSank I ended up TAing that lab as an upperclassman. It was a lot of fun, because we gave students plenty of attention. Me and my co-TA got to grill each one individually for half an hour every week, asking them about the lab they were about to do. I even added a "defend your lab report before I give it a final grade" component.

@ChrisWhite: You, sir, are a scholar and a gentleman.

5:29 AM

@ChrisWhite oooh I ike that!

@ChrisWhite: I TA'd an analog electronics course in grad school. THAT was fun

Also a digital one. That was cool too because FPGAs.

user54412

I wish I were better at electronics. I'm the type of person who will spend 15 minutes wondering why my diode doesn't work before realizing I hooked it up wrong.

lol

@ChrisWhite: Don't wish. Build something.

@ChrisWhite: You play guitar?

user54412

I wish I had time to build something. Or learn a(nother) instrument.

5:32 AM

@ChrisWhite: Well, I was just going to say that if you find a reason to use electronics you'll learn it.

@ChrisWhite: Like anything else.

user54412

that's true

user54412

My highest priority actually is to build my own telescope

very cool!

@ChrisWhite: That's really cool. you could always connect it to a motorized stand so that it rotates at a fixed rate for long exposures...

@ChrisWhite: You gunna make the lenses?

user54412

the instructor for that same lab course showed me some old books on the topic, the kind that just aren't written anymore ("you can purchase silver nitrate from your corner druggist")

user54412

5:34 AM

mirrors - lens grinding is far harder

@ChrisWhite: Yeah, I know. That's why I asked.

user54412

but a skilled hand can make decent size mirrors that are about as perfect as one needs to get

@ChrisWhite: There was a course at uni where people made telescopes, lenses and all. I was in a machining course next door and remember them grinding those things for like two months.

not every day, of course.

5:49 AM

0

Q: Why shouldn't a question be on hold? (no, really, I'm curious)

A little while ago this question was posted to Meta, highlighting an apparent inconsistency between the handling of these two main site questions: (A) How is the method of Lagrange multipliers used for multiple constraints of multiple variables? was closed under our homework policy, specificall...

discussion specific-question vote-to-close

6:07 AM

@DavidZ: I think you worded that well and got to the heart of it.

2 hours later…

8:33 AM

@DanielSank Hey Daniel! You can see which comment I was replying to by pressing the little arrow right next to it. I was asking you about what you said about the Fourier transform ;) I read something to the same effect on math.se one time, but I don't quite get it still...

@DanielSank Okay... Upon rereading the question I see that you're right.

@Omen sorry for not replying, I'd already gone to bed (first day of uni-related activities today!)

@Omen Well... This fact is not restricted to the (ex-)Soviet Union - my father's testicles provide a great example ;)

(oh god, I hope people don't take this out of context...)

9:08 AM

@Danu too late...lol

9:18 AM

@Danu: Regarding Fourier transform: a function is like a vector where the value of the function at each point is like the coefficient of the vector expanded in a particular basis. In other words, think of a function $f(x)$ as a sum of delta functions $\sum_{x_0}f(x_0)\delta(x-x_0)$

There must be other bases!

One such basis is the set of vectors which, when expressed in the $x$ basis, would have coefficients $\exp[i x k]$.

To find the dot product between two vectors, you multiply their coefficients and sum. Therefore, the dot product between two functions $f$ and $g$ is $\int_x f(x)^*g(x)\,dx$

The $^*$ is there because I'm covering the case where the functions could be complex.

So, to find the component of a function $f$ along one of the $\exp[ikx]$ vectors, we'd do:

$\int_x f(x)e^{-ikx}\,dx$, which is the Fourier transform.

Why is this a good idea? It's because in the $\exp[ikx]$ basis, the derivative $d/dx$ is diagonal.

$(d/dx)e^{ikx} = ike^{ikx}$

@Danu: That was a terrible explanation. Sorry. It's hard here because I can't easily type matrices to illustrate what I mean by "diagonal". Anyway, what did you mean by "Upon rereading the question I see that you're right"?

9:39 AM

@Danu: I'd be beyond happy to explain the Fourier transform thing to you with more clarity. I guess you could ask about it in a question or I could send you a 40pg document I wrote about it geared toward explaining it from scratch.

5 hours later…

3:04 PM

@DanielSank That's actually one of the best "Fourier transform in a nutshell"-explanations I've read.

4:00 PM

@ACuriousMind: Why, thank you. I have nice little 40 pg document I wrote up which starts with a discussion of linear algebra finite dimensions and then sort of tricks you into understanding the Fourier transform from the same point of view.

4:25 PM

I think they call this functional analysis. At least, the analysts do.

1 hour later…

5:32 PM

In the LQP review queue there is an auto-comment option for "this is a link only answer, and not spam", but when flagging a post, there is no similar option - I'm looking at "not an answer" or "low quality". I think I should be using LQ here, can anyone (mod?) confirm this?

Do both "not an answer" and "low quality" get sent into the LQ review queue?

that's a more concise version of my question ;)

5:49 PM

@FaheemMitha: Yes, sort of. Although my experience with math textbooks and courses is that they are often not designed to convey useful information into your brain. Well, this is a problem in other fields too...

6:09 PM

@DanielSank Depends on the book. And the course.

But yes, lots of books and courses suck. it's that 99% crud rule.

Sturgeon's revelation, commonly referred to as Sturgeon's law, is an adage commonly cited as "ninety percent of everything is crap." It is derived from quotations by Theodore Sturgeon, an American science fiction author and critic: while Sturgeon coined another adage that he termed "Sturgeon's law", it is his "revelation" that is usually referred to by that term. The phrase was derived from Sturgeon's observation that while science fiction was often derided for its low quality by critics, it could be noted that the majority of examples of works in other fields could equally be seen to be of low...

90%, actually. I think that is too conservative, actually.

1 hour later…

7:30 PM

@Kyle no, LQ is for basically gibberish. Link-only answers should be flagged as "not an answer"

@ACuriousMind this answer suggests that they do

3 hours later…

10:43 PM

hello?

Hola?

hey @Danu - is there anything with my answer here physics.stackexchange.com/questions/138075/…?

@DanielSank It's actually perfectly clear, thanks

@Omen anything with it... in what sense?

oops, I mean anything wrong with it

You're asking me about spectrometry?

10:53 PM

well, as an answer

I don't know the first thing about spectrometry, but I think it looks OK as far as being an answer etc.

why are you asking?

i am close to deleting the answer

oh... why?

don't know if it would be well received

I really don't think you have to worry about it

You'll notice soon enough if it gets negative feedback. Then you always delete it

10:58 PM

hmmm ok, i'll leave it for now.... gotta go to the gym

11:30 PM

@Omen: I get the feeling you're trolling. You post really good answers and then ask if they are good enough to not delete. Come on, dude! :)

Hi DanielSank! I was hoping to continue discussing my question on the definition of pressure.

If you could elaborate on what part of my comment you don't understand, I'd appreciate it.

Are you here?

@millsmess: Hello.

gimme a sec...

Sure.

@millsmess: You point out that as $A$ increases, sometimes F goes up, and sometimes F goes down. Then you said "the size of $dA$ doesn't matter in this case'.

I don't get that. It sounds like you're explaining why the size of $dA$ does matter.

11:47 PM

Okay.

The point is that if the force field in the region that the surface is extended to is zero at every point, then no additional force is applied to the surface, regardless of the size of the surface extension.

Indeed.

In contrast, if the force field was nonzero in some region and we extend A to that region, then additional force is applied to the surface, again regardless of the size of the surface extension.

So, different amounts of force are added to the surface, regardless of the size of the surface extension, depending on how the surface is extended.

So the size of dA does not matter.

Is this clearer to you?

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