The h Bar

12:55 AM

@ICCQBE no

google the moment of inertia of an annulus

3:59 AM

@vzn fluid is an interesting field of physics anyway I am going to post a question on meta so let see what other site member think about it.

@JMac morning

M.N.Raia

Hi for everone! Goodmorning/evening/night too! Hope you're all ok, given the currently world-wide situation.

So, I have a doubbt but I'm scary to write a proper question and then receive downvotes haha. Well, it's a totally particular point of view to try to search something beyond well-stablish things like the Energy Conditions (EC). In my humble knowledge about General Relativity, I tend to say that if a Field theory didn't "respect" the energy conditions then this field theory isn't physical.

doubt*

Yuvraj Singh...

@M.N.Raia stress energy?

Energy condition

In relativistic classical field theories of gravitation, particularly general relativity, an energy condition is one of various alternative conditions which can be applied to the matter content of the theory, when it is either not possible or desirable to specify this content explicitly. The hope is then that any reasonable matter theory will satisfy this condition or at least will preserve the condition if it is satisfied by the starting conditions. Energy conditions are not physical constraints per se, but are rather mathematically imposed boundary conditions that attempt to capture a belief...

John Rennie

4:40 AM

@ICCQBE moments of inertia just add and subtract, so the MOI of your annulus is the MOI of the disk with radius $b$ minus the MOI of a disk with radius $a$. So you were almost right. It's $I=\frac{1}{2}M(b^2-a^2)$

perilousGourd

5:17 AM

Do you guys sooner read the word 'subset' to mean 'strictly not a strict subset' or 'strict subset'? / Is there a convention?

Slereah

6:11 AM

@M.N.Raia What do you mean by locally versus globally

PM 2Ring

Here's one for the Pink Floyd fans. Unfortunately, the key of this song doesn't really suit Danielle's voice, IMHO, but she still does ok, and her bass playing is excellent (as usual). Danielle Nicole Schnebelen is from Kansas City, Missouri, and she's an old friend of Samantha Fish. There are lots of clips of them performing together, of varying audio quality.

"Have A Cigar" Danielle Nicole Band @ The Beachland Ballroom 2/29/2020

►

geocalc33

I'm also afraid of getting downvotes so I'll ask here

Two isometric lorentzian submanifolds $M$ and $N.$ Lines of constant time and space intersect. Does this imply that $M$ and $N$ are transversal?

Does a diffeomorphism of a spacetime have anything to do with gravity?

PM 2Ring

Here's one of Danielle's own compositions, which does show off her amazing voice.

Danielle Nicole Band - Save Me - Don Odells Legends

►

geocalc33

Say you have infinitely many transversal spacetimes

Slereah

6:26 AM

What do you mean by transversal

geocalc33

Well I'm not going with the pure math definition

the white lines are lines of constant time

and represent two transversal spacetimes

two copies of isometric spacetimes (intersecting)

Slereah

The white lines can't represent lines of constant time because they intersect

That would imply that there are two timelike direction at those points

geocalc33

yeah...

there are

Slereah

Also what do you mean by "constant time"

Constant time requires a time function defined

geocalc33

because there are two copies of spacetime

Slereah

6:31 AM

You probably to write down in more details what you're doing

geocalc33

1

Q: How do you show that the Lorentz metric is preserved for $\zeta^{3,1}?$

The following is a visualisation of a Lorentz transformation: https://www.desmos.com/calculator/u5qpd135uc. The lines of constant time in Minkowski space, $\Bbb R^{1,1},$ are hyperbolas: $$ f_T(x)=\frac{T}{x}$$ Where $T$ generates the set of curves. $T=\{t^2:t\in \Bbb R \cap(0,\infty)\}.$ Th...

special-relativity

Slereah

"This question needs details or clarity."

geocalc33

so the diagram with white lines and black background is a representation of two copies of minkowski space. The lines of constant time are hyperbolas

Slereah

apparently not enough details :p

geocalc33

yeah

I'm lazy

:/

been working on that tho

these are the lines of constant time

in the light cone

$xy=t^2$ mapped via nonlinear map

to get...$\ln(x)\ln(y)=t^2$

Slereah

6:36 AM

I still don't know what you're going on about

You should probably start off from basic Minkowski space

geocalc33

but it's easier this way

Slereah

Then why do you ask

If this is $\mathbb{R}^{(1,1)}$, these are not lines of constant time

Since they intersect, which is cooridinate invariant

Also you've been asking about that stuff for weeks now, so obviously you're not getting much back

geocalc33

yeah I'm not

I think people find it hard to wrap their heads around it

Slereah

I'd advise you formulate your question in a coordinate-independent fashion

What are you trying to do

geocalc33

Okay I will write that down in my notebook

Slereah

6:42 AM

If you're doing products of Minkowski space in weird coordinates, write those down, and specify why you're using those coordinates

also write down the coordinates

You keep using $x,y,t$ but I have no idea what those are

geocalc33

okay by products you mean

convolution?

Slereah

They can't be coordinates of $\mathbb{R}^{1,1}$ because that's three of them

geocalc33

yeah I'll work on conforming more to standard notatino

the red is the convolution of the green and the blue

and what I'm trying to do is understand the red

Slereah

My points still stand :p

geocalc33

yeah I know but it's so difficult!

Slereah

6:48 AM

well how did you even get here in the first place

none of this looks like standard coordinates on Minkowski space

just retrace your steps

geocalc33

it's funny how I got here actually..

I was working with functions and I realized they were nonlinear hyperbolas lol

geocalc33

7:01 AM

I wonder if the red are geodesics or something

JingleBells

@PM2Ring damn, how are those people not famous..

PM 2Ring

@JingleBells Commercial music is a tough world. Danielle's friend Samantha Fish is getting a bit more attention these days, but blues and blues-rock isn't all that popular these days. But the fans of that kind of music are pretty loyal & dedicated.

@JingleBells Oh. You didn't previously mention that this was for Arduino. Anyway, 128×160 is a pretty small display. It's hard to do good looking text at that resolution. Most fonts look like rubbish at the small point sized required, unless you're using speculially designed bitmap fonts. You can use some vector fonts if they aren't too fancy, and your font rendering engine is very good at antialiasing.

FWIW, about 10 years ago, I created a poor man's e-book reader from a mini photoframe. I can't remember the resolution off hand, but I think it might be the same as your Arduino display. I wrote Python software to do the text rendering, at the pixel level (from plain ASCII text files), saving the result as BMP frames (the photo-frame only accepts a few formats). It worked ok, until I got a real e-reader (just a cheap one from ALDI).

If you want a good graphics library with good font handling, I recommend Cairo. But I haven't used it for several years, so I'm a little rusty, and I guess it may have changed a little. The GTK library uses Cairo for its font stuff, but Cairo does a lot more than just text. And it can render to a variety of file formats.

satan 29

7:25 AM

1

Q: Confusion regading Defining Angular velocity about a point and an axis

My textbook, and Wikipedia: Both state that angular velocity is defined about a point. $\omega$ of a point particle relative to a point $o$, is related to the velocity relative to point $0$, $\vec{V}$, as $\vec{V}$=$\vec{\omega}$ $\times$ $\vec{r}$, where $\vec{r}$ denotes the position vector of...

homework-and-exercises reference-frames rotational-kinematics angular-velocity

I have edited the question as I was told to do by the people who closed it..

How do i try to reinstate it back?

@AaronStevens

Madame Akira

apparently StackOverflow has got dark mode. hmm

PM 2Ring

8:08 AM

@satan29 Your question has been sent to the reopen review queue. But give it a few hours. People in Europe are just starting their working day, and it's still before dawn in the USA. In the mean time, see if you can do anything more to trim down and consolidate your question. A lot of people won't even bother reading the whole thing because it rambles on for so long. ;)

Ok, maybe it's not that long. But it does have a couple of images of text, which a lot of people hate reading, and which are strongly discouraged on this site, and on most sites across the Stack Exchange network.

PM 2Ring

8:35 AM

in Python on Stack Overflow Chat, Jan 22 '17 at 15:18, by PM 2Ring

From https://en.wikipedia.org/wiki/Program_optimization#When_to_optimize "We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%" -- Donald Knuth

Yuvraj Singh...

9:08 AM

@PM2Ring hi sir how are you?

Physics Meta

10:08 AM

0

Q: ease in policy for some topics

At physics StackExchange, we discuss almost all type of physics topics some get more attention and some get less, but it depends upon various facts including our site policy, our policy is the same for each topic since many years which I feel is not right for the topic who is not a famous topic a...

discussion bug suggested-edits

user434058

10:24 AM

user434058

I swear I didn't do any kind of tampering with the HTML code, but really... 3 views and 6 downvotes :D That's 200% disapproval!

user434058

And all this was within 30 seconds O_O

Zlelik

10:42 AM

Hello,
You closed my question today about electric current in Gravitational field, because it is homework question. I do not think it is home work. Could you please clarify why do you think it is homework question?

This question: physics.stackexchange.com/questions/549094/…

John Rennie

@Zlelik yes, I agree. I have voted to reopen. @DavidZ could you take a second look?

@Zlelik the electrons won't fall at different speeds because the electrons behave like an incompressible fluid i.e. the number of electrons per cubic metre of the metal cannot change.

If the electrons fell at different speeds that would mean the density of electrons had to decrease as you went down the wire.

Zlelik

Thanks. Is it about electron degeneracy pressure?

or can you give me a few keywords for future reading?

John Rennie

10:59 AM

@Zlelik It's because the charge of electrons is balanced out by the charge of the atom nuclei. The atoms are fixed in place, so it you reduced the electron density you would end up with a net positive charge from the nuclei.

That net positive charge pulls the electrons back again.

satan 29

Hello John :)

Theres a 90% chance my latest question will get closed, So would you mind suggesting an alternative route to get an answer?

geocalc33

11:39 AM

I don't understand how to calculate boundary entropy

Secret

11:54 AM

MissingNo.'s Glitchy Appearance Explained

►

So... 2nd law of themodynamics as an algorithm:

1. Read physical state

2. Read probabilities to move somewhere for every particle

3. Apply axiom "higher probability = more likely"

4. Evolve the physical state into a new one

This algorithm is perfectly fine accepting inputs that looks ordered or disordered, and then spits out the most likely outcome, which can potentially be anything. This thus explains why entropy increase can lead to more ordered states or more disordered states and anything in between

So... in theory, in order to "glitch" the 2nd Law of themodynamics so that you get a perpetual motion generator, it is not the input that is the issue, but the algorithm itself, which as far we are aware, is unchangeable

geocalc33

I almost proved that space times time is information entropy!

ICCQBE

1:07 PM

@JohnRennie There is a issue with the solution I think.

The mass $M$ is only the mass of that gray area.

If the inner disc had mass $M$ same as the outer disc's mass, then we could simply say $I(\text{inner})=\frac{1}{2}Ma^2$ and $I(\text{outer})=\frac{1}{2}Mb^2$

Then we would easily substract them, so $I=I(\text{outer})-I(\text{inner})=\frac{1}{2}M(b^2-a^2)$

But in my question, there is no information about the inner disc's mass.

So we have to first find out what is mass of the inner disc

$M_i=A_i\rho=\pi a^2\rho=\pi a^2\frac{M}{\pi b^2-\pi a^2}=a^2\frac{M}{b^2-a^2}$

Then the result comes with the integration.

Secret

1:28 PM

Hypercentric optics: A camera lens that can see behind objects

►

When GR is not strange enough

abhas_RewCie

@Secret okai

ACuriousMind

2:34 PM

@PM2Ring The longer I code the more weary I grow of optimizations introduced before even knowing whether that part of the code is performance-critical at all. I can't count the number of times I've hunted a bug only to find a badly programmed memoization or a search algorithm that wasn't quite as clever as its creator thought as the root cause.

skullpatrol

2:54 PM

I believe it is your duty, as a programmer, to hunt down this reference:

> Knuth, Donald (December 1974). "Structured Programming with go to Statements". ACM Computing Surveys. 6 (4): 268. CiteSeerX 10.1.1.103.6084. doi:10.1145/356635.356640.

John Rennie

@ICCQBE ah yes, oops.

Though it's not that hard as the mass of the inner disk can simply calculated from the mass of the ring.

skullpatrol

Hi Sir @JohnRennie

John Rennie

If $M$ is the mass of the ring and $a$ and $b$ the inner and outer radii then the areal density is $\frac{M}{\pi b^2 - \pi a^2}$. Multiply that by $\pi a^2$ and $\pi b^2$ to get the masses of the large and small disks respectively.

@skullpatrol hi :-)

skullpatrol

Not going for a bike ride today?

:-)

John Rennie

I've just returned!

skullpatrol

3:01 PM

coolio

John Rennie

I combine my bike rides with going to the shops, and I'm just about to eat the food I bought. Bacon and egg pastries!

skullpatrol

Sounds yummy.

I find bacon a bit too salty for my tastes, but it's good for an occasional treat.

\o @SirCumference

Sir Cumference

ey how's life

skullpatrol

still kicking, how are you pal

Sir Cumference

all right, just trying to finish up my semester

skullpatrol

3:09 PM

on line?

Sir Cumference

yeah

Dvij D.C.

Hi

Can anyone suggest me a reference where the issue of unitarity is discussed in the context of cutoff regularization?

Naive googling doesn't take me much far. I am trying to understand as to why cutoff regularization is not unitary. I understand that we are leaving out higher momenta modes of the field but why can't I consider the smaller Hilbert space spanned by the modes that we are taking into account as my Hilbert space and argue that unitarity would be preserved within that new small Hilbert space.

I guess if I look at a proper calculation of how the unitarity of S matrix is violated by an explicit cutoff, I will be able to reverse engineer the reasoning in terms of leaving out parts of Hilbert space.

ACuriousMind

3:27 PM

@DvijD.C. If the restricted dynamics were unitary, this would mean that there are no dynamics that turn low modes into high modes, i.e. the smaller Hilbert space would have to form a superselection sector of the theory. This is clearly not true for any non-free theory.

Gyromagnetic

Hallo, any astronomers around?

abhas_RewCie

@Gyromagnetic Will Astrologers work? I predict astronomy answers by looking at hands

Gyromagnetic

unfortunately no, lol

abhas_RewCie

Okay.... Question?

ACuriousMind

@Gyromagnetic Just ask your question, if someone comes by that can and wants to answer it, they will

abhas_RewCie

3:34 PM

Why so silence?

Dvij D.C.

@ACuriousMind I see that the matrix element of the Hamiltonian <high momenta mode | H | low momenta mode> wouldn't be zero but when we put a cutoff, we won't anymore have the entries <high momenta mode | H | low momenta mode> (and its complex conjugate entry). The way I am visualizing it is that we are cutting off the Hamiltonian matrix in a way that is symmetric about the diagonal. So, why wouldn't the resulting matrix still be Hermitian (and thus the propagator unitary).

Gyromagnetic

Well, I'd be more interested in having a conversation with one but whatevs... Im looking for a survey of galaxies/clusters that includes ang. momentum, DM content and residual magnetic field

2

Dvij D.C.

I have a strong feeling I am completely misunderstanding this whole thing xD

abhas_RewCie

okay

ACuriousMind

@Gyromagnetic Unfortunately we don't have many astronomers that visit chat regularly, but I've starred your message in case one comes by :)

@DvijD.C. I think it depends on how exactly you define your regularization and your S-matrix. Unfortunately it's common for physicists to just say "and then unitarity is lost" even if they mean a far more specific problem :P

Dvij D.C.

3:39 PM

I am imagining something like this. If the full matrix is Hermitian, the black part after removing the orange high momenta modes would also be Hermitian.

ACuriousMind

Yes, I agree with that. The question is whether "cutting off stuff from the Hamiltonian" is the definition of the regularization procedure used by the people who say that unitarity is lost here

Dvij D.C.

Ok, sorry I messed up. Assume the graphics is 4 by 4 by ignoring the bottom row xD

Ah, I see.

abhas_RewCie

Physics = imagination

ACuriousMind

E.g. if you try to cut off not the Hamiltonian, the exponentiate, but you first exponentiate the full thing and then cut off the resulting time evolution operator, then that's not necessarily unitary

abhas_RewCie

Bad me: It took me a month to realize why Instagram Explore button is so strange one.

skullpatrol

3:45 PM

Stay away from social media, Luke.

Gyromagnetic

@ACuriousMind Thanks!

abhas_RewCie

@skullpatrol Yap. Instagram doesn't interests me either.

skullpatrol

Too many Instagram models there.

abhas_RewCie

@skullpatrol lol. Too much editing too.

skullpatrol

::knods::

Dvij D.C.

3:48 PM

@ACuriousMind Ah, that clarifies a lot. I suppose in the path integral approach, simply using the cutoff regularization in the integrals at the end of doing everything would amount to cutting off the exponentiation without first cutting off the Hamiltonian.

abhas_RewCie

:Knods back:

Dude, just another question, How y'all are doing without haircut in lockdown? My heard and hair have covered whole face.

PM 2Ring

@ACuriousMind Understood. I wanted to give the full Knuth quote, since a lot of people don't mention the 97% part. I strongly believe in making code behave correctly first, and then going back & tightening it up, where necessary. OTOH, that doesn't mean we should code without having some awareness of the speed of the core language features and of common algorithms we use.

user434058

4:08 PM

Yo! I can edit instantaneously! :)

PM 2Ring

I mostly code in Python these days, so the goal is to optimize the time it takes to write (& read) the code, not run it. And Python can be a bit weird in terms of its running speed, if you're coming from a fully compiled language, as I mentioned here:

The relative execution speeds of algorithms implemented in CPython may be different to what one would expect from a simple analysis of the algorithms, and from experience with other languages. That's because Python provides many powerful functions and methods implemented in C that can operate on lists and other collections at close to the speed one would get in a fully-compiled language, so those operations run much faster than equivalent algorithms implemented "manually" with Python code.

abhas_RewCie

@FakeMod Instagramming Instantaneously!

PM 2Ring

@FakeMod Congratulations!

John Rennie

@FakeMod 2000 rep? :-)

user434058

@PM2Ring Thanks! :)

user434058

4:12 PM

@JohnRennie yup! (Though I might even lose the privilege if few of my edited questions are deleted and I lose my 2 rep, so I am currently on the borderline :)

user434058

@abhas_RewCie hehe :D

John Rennie

I don't think you lose the privilege once it has been granted, even if your rep dips down again.

abhas_RewCie

yep

ACuriousMind

@JohnRennie On the contrary, it does:

29

A: Can you lose an ability if your reputation falls below a threshold?

Can you lose an ability if your reputation falls below a threshold? Yes.

user434058

59

Q: Loss of reputation and loss of privileges: should they always be connected?

I recently got the Edit Questions and Answers privilege in Stack Overflow. I had exactly 2,000 rep. I decided to spend some time in reviewing and I found a post that, in my opinion, required a downvote. As I applied the downvote I realized that I had lost the just acquired privilege, since my re...

discussion reputation privileges

user434058

4:14 PM

This might be me, lol

JMac

I'm pretty sure I gained the close vote ability for like a day, then lost it for like a week when a user was deleted.

user434058

Anyways, I am just gonna reduce the activity slowly (I hope that I do so :P ), some other tasks are ready for me to pay more attention to them.

user434058

In my current rep distribution, its literally one answer responsible for 25% of my rep. We might as well see the 80:20 phenomenon here :)

PM 2Ring

@FakeMod Speaking of edits, there's a word missing from the title of this question you recently edited. physics.stackexchange.com/q/549139/123208 You should probably fix that... if you can guess what word the OP left out. ;)

user434058

@PM2Ring Ah, my bad :)

user434058

4:22 PM

So should I re-edit?

PM 2Ring

@FakeMod Yes.

user434058

And FWIW, someone's really set on making me lose the privilege ;P, coz I just got a downvote on my, previously, zero downvoted and highly upvoted answer :)

user434058

But I don't really mind...

user434058

@PM2Ring did it

PM 2Ring

@FakeMod I could've done that edit myself, but I like to encourage people to fix all the stuff they can when they do an edit. ;) Of course, it's always possible to simply not notice missing words. :D

user434058

4:27 PM

@PM2Ring That happens when you do stuff while listening to music ;)

PM 2Ring

@FakeMod Brains are good at filling in missing information so that we aren't consciously aware of all the gaps in the data pouring in through our senses. So it can be hard to overcome that when we want to spot gaps, like proof-reading, or debugging code.

user434058

@PM2Ring Hmmm... Brains(or psychology) are interesting.

John Rennie

Tasty too

Madame Akira

4:44 PM

@JohnRennie sir ! what might me your reputation rank over whole SE network cause 300K that's behemoth.

John Rennie

@MadameAkira hi :-)

Madame Akira

oh
Hi :-)

Emilio Pisanty

-2

Q: On the Bell's theorem, why is the magnetic correlation function a scalar product of hidden variable and the measurements?

Since the relation between Magnetic Force (as the effect) and Magnetic Field (as the cause) is non-associative ($F=q V \times B$ or $\tau=\mu\times B$ where $\mu=\gamma mr\times V$) in Bell's Theorem when calculating the correlation between measurements, I was expecting to see a cross product b...

quantum-mechanics magnetic-fields quantum-spin magnetic-moment bells-inequality

oooooffff

thoughts?

CC @ACuriousMind @Qmechanic

also from review

Hi Gaurav Kochar, and welcome to Physics Stack Exchange! It's against our rules to post images of text you want to quote. Please type it out instead so it can be indexed by search engines. For formulas, use MathJax. — David Z ♦ 9 hours ago

@DavidZ I'm not very happy about that use of "against our rules".

I don't think it's a particularly friendly way to nudge users into the behaviour we want to encourage

my canned comment is

> Please do not post images of texts you want to quote, but type it out instead so it is readable for all users and so that it can be indexed by search engines. For formulae, use MathJax instead.

with a link to meta

ACuriousMind

@EmilioPisanty Looks like ~~unclear what you're asking~~ needs details or clarity to me

Emilio Pisanty

@ACuriousMind does it?

to me it's pretty clear that OP is bonkers

ACuriousMind

4:53 PM

The spectrum of opinions covered by that close reason does entail "This doesn't make any sense".

I'm more worried that no one yet voted to close that question.

Emilio Pisanty

didn't they?

it's on the close review, I skipped it because it wasn't obvious to me

ACuriousMind

It hung around in the close review with 1 LO vote and no close vote for a week, apparently.

@EmilioPisanty You mean my canned comment, which I graciously provided to you free of charge ;)

user434058

7

Q: Song 3 by Mr Physicson

Mr Physicson has been programming some nuclear reactor results filtering program. So, when he returned home tonight, he incorporated a bit of this new knowledge when he was singing to his son: x=person:property(("small sized"&&"black skin")|("small sized"&&"red skin")|"good deeds") set x_count=1...

wordplay music

user434058

Mr Physicson would be such a boring dad :P

sbak

5:22 PM

Hi, anybody have idea on Ruby on Rails?

sbak

5:53 PM

Ping me

ACuriousMind

@sbak This is the chatroom for physics.SE; while there are some programmers here their expertise is typically not in web frameworks...

David Z

6:31 PM

@EmilioPisanty yeah I've been thinking about changing that. That being said I've noticed a few people using your (ACM's) version but I'mnnot wholly satisfied with that one either, so I haven't quite figured out what I want to change it to.

Emilio Pisanty

@DavidZ sure. whatever works for you. But the current version looks rather too aggressive to me.

it's hardly a 'rule' as such, and to the extent that it is, telling new users that it is just makes us look like we're fixated on irrelevant details

not to say that we're not...

... but they don't have to find out immediately upon joining =P

David Z

Eh I'd say it is kind of a rule. I mean, I do want to give the impression that posting images of text is Not Okay and is something that justifies negative consequences to the question, not just a minor preference on our part.

David Z

6:57 PM

@JohnRennie I'm not asserting that the question actually comes from a homework assignment, but it did look like a question of an educational nature.

I guess I can vote to reopen but let me try to make a slight edit first to clarify it.

PM 2Ring

7:12 PM

@DavidZ There are also some posts on MSE explaining why images of text are not welcome on the network, eg meta.stackexchange.com/q/320052/334566 Images of text on Physic.SE annoy me, but I rarely downvote them, unless they're very hard to read, or sideways, or they comprise the bulk of the question body. Of course, they often occur in homework dumps, which I VTC, but is there a valud close reason for questions containing images of text if they aren't homework dumps?

David Z

Thanks for pointing out the link

I don't think we generally consider images of text to be a reason to close a question. At least, that's the current state of things, although I don't know if I quite agree that that's the way it should be.

I suppose you can always enter a custom close reason. But it probably does make more sense to do that when the post consists almost entirely of images, and less sense when it contains plenty of text and there just happens to be an image included that contains some more text.

PM 2Ring

FWIW, I developed my hatred of text images on SO, where it's vital for answerers to be able to copy & paste the OP's code and input & output data. At least on Physics.SE that's less of an issue, apart from when we want to quote part of the question, especially equations. OTOH, the OPs who post images of equations probably don't know MathJax anyway...

@DavidZ I think the best we can do is to strongly discourage posting images of text. Physics.SE already has a reputation for being rather harsh, due to the strict homework policy. Making text images off-topic would not help with that. ;)

David Z

Oh they're definitely not off topic.

What I had in mind was a form of putting questions on hold not because they are off topic but because they're really in need of editing.

PM 2Ring

@DavidZ Oh, ok. That could work. And I think it'd fit with the forthcoming changes to the close process that were announced a little while ago on MSE (or maybe MSO).

David Z

Yeah. The fact that they've already changed "off topic" to "community specific reason" is a step in the right direction for that.

PM 2Ring

7:29 PM

When I created i.stack.imgur.com/R1znn.png and posted it in the Python room a few years ago, it was met with general approval (and got 6 stars), but an SO mod (who also happens to be an excellent Python coder) asked me to not link to it in comments, and that such comments would likely be deleted as non-constructive.

ACuriousMind

@PM2Ring Well, I'd say it's kinda like lmgtfy links - they make their point, but it can come across a bit more hostile than necessary

PM 2Ring

True. It was intended to be a bit of light-hearted snark. But snark was a lot more common on SO back then, before the Welcoming Wagon initiative.

vzn

8:02 PM

electrons as incompressible fluid? cool idea :) Hydrodynamics of Euler incompressible fluid and the fractional quantum Hall effect journals.aps.org/prb/abstract/10.1103/PhysRevB.88.241305 / Incompressible electrons phys.org/news/2015-11-incompressible-electrons.html (etc)...

Physics Meta

10:19 PM

0

Q: I have seen something weird today And please help me to understand this

I have a refrigerator, that's not weird. What happened inside is I put an ice tray to make some ice, now I have a different kind of ice tray it's like two way ice tray. Now what is two way ice tray it's like i can use it from both sides, once on side frozen i can fill the second side and again ma...

discussion

JMac

10:41 PM

Does it seem right to reject edits on closed questions, where the edit comes after the close and is only adding a bit of mathjax formatting? I personally think they are bad edits because it can bump the post and put it in the reopen queue without really adding anything; but I don't know if there's a policy on that.

PM 2Ring

10:52 PM

@JMac Yes! Please reject such edits. They're evil. If the question is fixable, the OP ought to get the opportunity to fix it before it's sent to the Reopen review queue. And if the post isn't fixable, then it's a waste of everyone's time to approve the edit & review the question, especially when the edit is merely cosmetic and doesn't actually make the question worth opening.

JMac

@PM2Ring physics.meta.stackexchange.com/a/12605/127931 I had just read this post (that I had read before) that was already on the same page as me. I did wind up rejecting it. The person did several edits in a row like that (one also completely changing some values while mathjax-ing it)

PM 2Ring

Note that only the 1st edit after closing sends the question to the Reopen queue. And that includes an edit that was made prior to closing but approved after closing.

JMac

Yeah I remember we were talking about that with FakeMod. I'm also much less sympathetic when the posts were from like 5+ days ago and not bumped since.

PM 2Ring

@JMac :) There's probably posts about this on MSE (or at least MSO).

@JMac Well, at least if it's been closed for 5 days it's not stealing the OP's chance to fix it. But it's still wasting reviewers' time.

JMac

So I'm looking through the persons edit history like a creeper, and so far I've seen several of those edits that are getting approved, all closed 5+ days ago with just some mathjax -_-

PM 2Ring

11:01 PM

There's a prolific <2k editor who's been doing a lot of this. I put comments on 2 of them in the last few days, but he hasn't replied to me yet. You can ping the editor with @username but the username doesn't autocomplete.

That doesn't work if the edit wasn't approved, though.

JMac

Yeah creeping through your comments I think we're talking about the same person. People seem to be approving them easily. Even the one that changed some values had one accept vote before it got 2 rejects.

PM 2Ring

:facepalm: Looks like those reviewers need educating, as well as the over-enthusiastic editor.

Physics Meta

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Q: Introducing the possibility of creating folders in the favorites section

It is my first question on meta, and I am not sure if this is the right place for this. I tried to see if it is possible to create folders in the section of favorites, to organise the related question in different topics. Personally I have saved different questions because I still can't understa...

feature-request

JMac

"JMac has approved 80 edit suggestions and rejected 179 edit suggestions and improved 19 edit suggestions" I'm definitely somewhat critical when I review edits.

PM 2Ring

There's an old saying that got an added twist a decade or so ago. "You can't polish a turd". The added twist is "But you can roll it in glitter". In the Python room, some of us in that room use the term "glitter-roll" and to refer to edits to unfixable questions. ;)

@JMac You have to be critical. Robo-reviewers are a real problem, though I guess it's not quite as bad on Physics.SE compared to SO. Partly the motivation is for badges, but I think part of it is the new reviewers just graduated themselves from needing their edits approved, and they want to make the approval process smooth for the <2k people.

JMac

11:14 PM

The weird thing is, a lot of the times I see something and think "You accepted that?" it's people who seem to have a lot of reviews, so I almost suspect it isn't people getting the badge. It seems like they just kinda skim through it to approve mathjax (and other edits obviously)

PM 2Ring

11:34 PM

I agree it's weird, but I have no idea how to fix it. Hopefully, the upcoming changes to the review system will make a difference, since they will give reviewers more info about what they're supposed to be doing.

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