@AaronStevens I can't believe it's still like that. Hiding the close reasons from all other viewers is so obviously unhelpful for new users. SE logic lately has been a friggin mess.

@ACuriousMind I can understand.

@JMac Yeah, and they did it right after we had modified the close banner to say "answers to such questions will be deleted"

So that part is pretty much completely pointless now

Oh yeah, it was right after we spent time discussing it on meta. Perfect timing.

@ACuriousMind The umlaut o's are close to the l's on your keyboard I assume :P

@ACuriousMind Yes, I think I have observed that happen a few times. Shouldn't there be a spam-type filter for these posts? It might reduce the workload of human contributors.

Well, maybe the visibility for the close notice will come back. But I never really understood why it should be hidden in the first place

@Kb314 there was chat regarding this topic on one of s. E site.

@JMac Heh, yes, ö is to the right of l

@ACuriousMind I think something had been said about "privacy" or something? Maybe I am getting mixed up with some other dumb decision

I could begin to understand "privacy" arguments for hiding the close voters, but not the close notice, as it contains no user-specific information

@ACuriousMind may be an extra moderator can help.

oh yeah, I guess that is true. I think my presence on the closure of certain questions has made certain users dislike me in the past

@kb314 Well, if you can come up with a way to reliably identify these posts mechanically, we'd be happy to use it ;)

Which only work on this type of subjects.

Well, on an unrelated topic, how long do you guys think the markets will sustain the present level of slow-down caused by recent health concerns?

@ACuriousMind I'm basically all for removing or obscuring the identifying information about who voted for closure. That on it's own would have been a good change. I would have never suspected SE to screw that up! /s

Smokey already runs a lot of user-driven spam heuristics, I'm sure we could get them to run a HW-detection bot for us, but I don't see a good way to detect HW questions by patterns alone with a low false-positive rate

@ACuriousMind It might not be that challenging, if there is sufficient labeled data (which there is, from what we've been discussing). The issue is, whether incorrect predictions will increase the workload (of reviewing posts and justifying their spamming).

We'd really need a low (<0.1%) false positive rate here otherwise we'll be driving away new users that got their question closed by a bot.

@YuvrajSingh... Help with what? Moderator workload is very bearable currently.

@JMac @JMac, I disagree. If the close banner information is available to users, then I agree with your statement. Otherwise, as a new user who has issues with closures, there is no recourse other than posting on Physics Meta and hoping that the relevant voters would notice that question.

@ACuriousMind what I meant is a moderator who only work on such type of low quality questions.

@ACuriousMind Agreed. This is not so challenging, but mostly depends on the quality of labeled data.

@YuvrajSingh... Ok... seems like a well-discussed issue

@kb314 I'm not sure I understand. I was saying that if all users could see close banner information; but not the names of who closed it, that change would have made sense; but SE took it one step further and basically removed everything.

@JMac Oops. Sorry I misinterpreted the thread to read that you were suggesting that the OP whose post has been deleted should not be able to view the identity of the close voters.

@YuvrajSingh... I don't think we really need a moderator for that. We would need privileged users like me to spend time looking through the close vote review more often. I'm just lazy about that stuff and usually only look at some of the other reviews.

^that. Moderators don't scale, users do

@ACuriousMind Well, the moderator would be labeling data... so... literally training their better and faster replacement!

@kb314 That I'm on the fence about. I don't really see much reason why the user would have to know who closed it either. There's not really any way to directly contact a user if you know who closed it anyways; and making a generic meta question asking why it was closed seems more reasonable to me than trying to ask specific users why they closed it.

@JMac Agreed. But if you see them on chat, you could ask them directly and improve faster than awaiting answers (and reading long posts) from Meta.

@kb314 Isn't the data being labelled simply by the questions being closed as HW (or not) here? TBH I didn't really understand what Yuvraj thought this extra moderators should do.

@kb314 The vast majority of users does not use chat at all!

@ACuriousMind Not sure what @YuvrajSingh... meant either. But I'm suggesting that this hypothetical new moderator would, as you said, label data as homework-like or not.

@kb314 Sure, but some users don't really like that. It could actually encourage people not to vote to close; worried that they might get pinged in chat to explain something that they don't feel like explaining in more detail; or just making users angry at them. I've seen plenty of posts where people assume negative things about others, just because of how often they vote to close off-topic questions.

@ACuriousMind Woe be them. Seems like a cool $\bar{h}$ place to hangout.

@JMac I guess it feels personal because of the lack of transparency. I am not alleging an intentional obscurity, but how would users know what exactly are desired and non-desired questions on the forum without any introductory orientation?

Through the time-honored tradition of lurking ;)

@JMac Just to be clear, I did not think so... But just takes a few posts to understand what the community is all about

But sure, we don't really hold it against new users when they ask an off-topic question. Closing a question is not a value judgement of the asker!

@ACuriousMind A well-deserved honor :)

But some take it as a judgement of themselves, and that's where it gets personal.

@ACuriousMind Agreed.

what is the mathematical explination of why a top does not fall?

@kb314 The site does give you the tour, along with links to the help center. The close vote reason typically also has a link that explains that type of closure in detail. All of that education can be done without telling you who voted to close your question; which is why I think that part isn't necessary.

@ACuriousMind I guess every online community has the necessary evils of social-media behaviors.

@JMac What ever could you be talking about?

@kb314 Honestly, I didn't find it that hard to figure out how the site worked either. I read things for awhile before I participated, and everything went fine for me. I've also seen quite a few new users get a very negative opinion about this place. Those are what I worry about.

@AaronStevens Just a totally hypothetical situation...

I'm struggling to come up with a good mainstream dictatorship joke

Apparently I am the dictator here :P

@JMac A lot of students who posted homework questions would have such an opinion. Instead of closing the question with stock reasons, my suggestion would be to present an example of how a homework question can be re-worded.

@JMac Quite non-pc these days I guess.

@kb314 The close banner gives examples on how to do that though

@AaronStevens got it.

@kb314 There are links to that, and ACM mentioned the other issue. For a lot of those situations, even knowing what is acceptable and what isn't doesn't necessarily help them; because they specifically do want help with a solution to their homework, not with any underlying conceptual issue.

At that point they really should be seeing a tutor or their instructor

@MadSpaceMemer This might help.

@AaronStevens Trying to drum up some more work for yourself?

Which makes sense. Instructors assign problems for specific reasons. So they would be the best to go to in terms of getting what they want you to get out of it

@JMac Yeah I was just about to post my contact information :P

@AaronStevens how much $$?

@kb314 The tutoring site I work through does roughly $15 per hour

Depends on the subject though

Calculus based physics is a little more than algebra based physics

And higher level math subjects are more money of course

@AaronStevens Whoa! I thought this was a joke. Well, nice... That's a pretty good rate considering what TAs get...

@kb314 A lot of tutoring I do is online and the institution pays for the service

@AaronStevens I wonder how fast the bots or mods would pick up on you if you responded to every closed HW question with "Please note that homework type questions are off topic here. If you would like some assistance, please contact me at aaronstevens@myemail.com where I offer tutoring services".

So it usually isn't the student paying that much

But that is how much I get paid

@AaronStevens, I see.

@JMac I love it haha

@JMac We'd probably advise against it shortly after you suggested it in chat, because you probably shouldn't do that.

The "spam" mood message includes the phrase "our advertising rates are quite reasonable."

@bolbteppa it looks like he was on a quixotic quest at the 2nd ~½ of his life, thats conventional wisdom by top experts. however, some quests are valid but remain unfinished. some quests span decades long after their originators/ initiators/ early but visionary dreamers. it is the conventional approaches that are increasingly looking quixotic and demonstrably/ undeniably hitting dead ends...

Opinions required: off-topic or just not a very good question?

AC Corona sounds like a football club.

@bolbteppa a fluid is new paradigm and therefore better than a field which is old paradigm

duh

@Loong Going by the news, would be a fitting name for several of them right now :P

heh

@ACM you mean: they are infectious?

or their fans are rabid?

If the word fluid is replaced with the word field, which is likely what is meant everytime it's brought up, everything becomes establishment physics :p

@ZeroTheHero Unless I've already started hallucinating, there have been several prominent cases of football players contracting the corona virus

But I guess that's very European news and perhaps not as prominent in the US

They all stopped playing anyway.

@ACuriousMind ah the players not the FCs..

"If you suspect that you suck, you will probably suck. This is called the self-fulfilling prophecy. If you suspect you are great, you will probably suck. This is called the Dunning-Kruger effect. There’s an obvious deduction to be made here, but you probably missed it."

@Slereah You can't suck if you don't suspect anything!

You can also reverse this by using impostor syndrome and self-fulfilling prophecy

hmm i'm curious, can you set a variable to 1 using natural units?

it'd probably screw up a lot of other things but maybe it could make something easier

@SirCumference ...you'll have to be a bit more specific :P

In slightly imprecise usage, lots of people say that natural units set e.g. $c = 1$

well like, say i've got a force $F=g\cos{t}$

where $g$ is standard gravity

i wonder if I can define a unit such that $F=1$ at all time

and if that kind of thing would ever be useful in a computation

no, you can't, units do not vary with time

but could they

i mean the biggest use of natural units i've seen is to reduce computations and expressions

I'm sure you can work out some sort of system where your units are allowed to vary with time but it would be a collossal waste of time :P

That is, whatever you're doing is so unlike what we ordinarily mean by "unit" that using the same word is rather misleading :P

eh who knows. in high school i wrote off non-cartesian coords as overcomplicated and a waste of time till i realized they simplified things a lot

maybe there's some analogy between swapping coordinates and using natural units

i'm tired tho so I might just be writing nonsense

Hello everybody!

I got a very basic and simple question that I can even guess the answer but I want to be sure.

In talking about the conversation of angular momentum, is the conversation of angular momentum means that the $\vec{J}$ (angular momentum vector) should be $\vec{0}$ or the change of angular momentum by the time should be $0$?

I think the $\dot{\vec{J}}=\frac{d\vec{J}}{dt}$ must equal to $0$

Am I right?

Change should be zero, so that $\vec{J}$ is a constant vector as time changes

Alright. Thank you.

Now I have another question about the conservation of angular momentum

I just want to prove that the rotating body's linear velocity will increase as it's distance to the orbiting mass (the mass that the rotating object is rotating around it) decrease in an eliptical orbit.

I thought that if I select the constant point as the center of the orbiting mass and take two different moment on the system I can prove it.

First moment, when the rotating mass' velocity vector is perpendicular to the position vector $\vec{r}$ but magnitude of the position vector $r$ is the smallest possible value.

Second moment is the same as the first one, but the position vector's magnitude is greatest possible value.

So, if I select a cartesian coordinate system that the x-axis as horizontal, y-axis as vertical and z-axis is to perpendicular to the plane that is created by x and y axes.

So, if I select a cartesian coordinate system that the x-axis as horizontal, y-axis as vertical and z-axis is to perpendicular to the plane that is created by x and y axes.

The $\vec{r}_1=a\hat{y}$, $\vec{v}_1=v_1\hat{x}$ and $vec{r}_2=b\hat{x}$, $\vec{v}_2=v_2\hat{y}$

As the conservation of the angular momentum due to the gravitational force is a conserved force.

$\vec{J}_1=\vec{J}_2$

$\vec{J}_1=\vec{r}_1\cross{m}\vec{v}_1=m{r_1}{v_1}(\hat{y}\cross\hat{x})=m{r_1}{v_1}(-\hat{z})$

$\vec{J}_2=\vec{r}_2\cross{m}\vec{v}_2=m{r_2}{v_2}(\hat{x}\cross-\hat{y})=m{r_2}{v_2}(-\hat{z})$

$\vec{J}_1=\vec{J}_2 \Rightarrow m{r_1}{v_1}=m{r_2}{v_2}$

${r_1}{v_1}={r_2}{v_2}$

Here, $r_1$ is smaller than $r_2$

As, the $r_1$ decreasing $v_1$ is increasing.

So, I think I've proved it.

Is my method correct?

If It's not correct the accurate or efficiency way to prove it, please give me tips. Not the solution, I would like solve it on my own.