The h Bar

Emilio Pisanty

16:00

Hey, @JohnRennie, thank you very much for that bounty. I'm deeply honoured.

John Rennie

@EmilioPisanty you're welcome :-) I thought it was exactly the sort of answer that this site should be producing. Rigorous, but explained in a way accessible to even learner physicists. Why the OP accepted a vastly inferior answer totally escapes me!

heather

What was the answer @EmilioPisanty?

Emilio Pisanty

@JohnRennie I suspect OP is somehow allergic to engaging with anything I write, beyond comments on other people's posts.

43

A: Is there oscillating charge in a hydrogen atom?

In this specific instance you are correct. If you have a hydrogen atom that is completely isolated from the environment, and which has been prepared in a pure quantum state given by a superposition of the $1s$ and $2p$ states, then yes, the charge density of the electron (defined as the electron ...

There's a couple of foundational issues on that one that I think could still be improved.

heather

@EmilioPisanty wow, that must have taken a while =)

not that I understood much of it, to be honest =P

Emilio Pisanty

@heather that took about a couple of hours, I think

heather

16:05

@EmilioPisanty, to be absolutely honest, I'm not sure I've ever spent that much time on an answer

Emilio Pisanty

It looks jazzy but it's all material I know well and I have it fresh in my mind, so it's just writing it down that takes the time

@heather oh, it was totes worth it.

Writing a good answer is mostly its own reward.

heather

This is probably the answer I've spent the most time on:

4

A: Please explain entropy curve

For reference, the diagram is below. First, I'm just going to give a quick explanation of entropy. Before Boltzmann, people knew about entropy, they just didn't explain it correctly; namely, they thought of it as a measure of the uselessness of arrangements of gas. As an example, they thought t...

Emilio Pisanty

@heather ... although part of the hope was writing something that someone like you would be able to understand most of, so I guess I still need to do better ;-).

Out of curiosity, which parts do / don't you get?

John Rennie

@heather it's simpler than you think. Equations always look a bit fearsome when you write them down, but the underlying principle is very straightforward.

heather

@EmilioPisanty, I don't know much of anything about quantum mechanics, so I don't even really understand the question =P

Emilio Pisanty

16:08

@heather fair enough

and yeah, what @JR said. The equations look fearsome but they're fished straight out of Wikipedia

heather

I know there's a couple quantum numbers, s and p and two others, I think, and then they represent states, though I dunno exactly what 2s means, for instance, and then he's saying a superposition, so some kind of combination of the two, and then I dunno what oscillation means here. so. that's about where I'm at.

and then I don't know what exactly a wavefunction is. =)

I think it represents something about the probability a particle is at a certain position? not sure.

Emilio Pisanty

@heather yeah, that's fair enough

heather

=)

Emilio Pisanty

The wavefunction can be used to obtain the probability that the particle is at any given position, but it includes some more information too. It'd be nice to have a solid enough QM-for-beginners book to recommend but I'm not sure if it exists.

I read this one when I was sixteen or so

amazon.com/Quantum-Perplexed-Dr-Jim-Al-Khalili/dp/1841882380/…

but I haven't looked at it since I became a professional quantum mechanic, so I don't know how well I'll like it nowadays

heather

thanks for the book reference; I'll take a look

Emilio Pisanty

16:17

@heather give a shout if you like it ;-)

heather

@EmilioPisanty, will do =)

Emilio Pisanty

@heather The next thing up that I'd recommend is Griffiths

amazon.com/Introduction-Quantum-Mechanics-David-Griffiths/dp/…

but that's probably a bit too much for you at this stage

Mark Mitchison

@EmilioPisanty Thanks for the rep! :)

Emilio Pisanty

If you can get a copy (without paying too much) to have a look at, then you can decide if it's intelligible

@MarkMitchison no worries, dude

that's an awesome answer

plus I've got way too much of the stuff

Mark Mitchison

thanks. your bounty seemed to stimulate a lot of extra interest in that question as well, which is nice

Emilio Pisanty

16:20

and we need more folks like you on the >10k side

user3625380

Ah you're talking about QM. So can I sneak in a QM question of my own?

Mark Mitchison

only 915 rep to go until mod privileges :)

Emilio Pisanty

@MarkMitchison well, yes and no

@MarkMitchison mod privileges are....

Mark Mitchison

@EmilioPisanty haha, yeah. the other new answer is a good one, though

Emilio Pisanty

slightly overestimated

there used to be a 10k flag queue but that's gone

you can vote to delete some stuff, but there isn't enough critical mass for that

you can see deleted posts, which can be quite handy

I think the most helpful ability is auditing the global review queue history

@MarkMitchison yeah, that one is nice

@user3625380 yeah, go ahead

terdon

16:24

@koolman you called?

user3625380

@EmilioPisanty Thanks. I posted this a few hours ago. I'm reading what I can about it, and have talked to some grad students, but we're a bit stumped. physics.stackexchange.com/questions/294349/…

Any insight would be great.

Emilio Pisanty

@user3625380 that's a pretty terminology-heavy post

what do you mean by $U$ there, exactly?

user3625380

Unitary operator

Emilio Pisanty

@user3625380 yeah, so say that

user3625380

Got it. Editing. Any other clarification?

Emilio Pisanty

16:27

compare with the Wikipedia explanation: en.wikipedia.org/wiki/Werner_state

Mark Mitchison

@user3625380 What's the symmetric and antisymmetric state/subspace etc... The lack of a definition for this is particularly weird since later you seem to imply that a singlet (i.e. totally antisymmetric state) is a symmetric state.

Emilio Pisanty

> A Werner state[1] is a d × d-dimensional bipartite quantum state density matrix that is invariant under all unitary operators of the form $U\otimes U$

@user3625380 is this just for two entangled qubits?

or some other system?

either way, you need to clarify

With something that is this involved, you need to be as rigorous and clear defining the framework as you would be in the introduction of a paper

heather

@EmilioPisanty, just found a copy of griffiths on the internet. it looks like I could plow through it once I learn more about classical mechanics (of which I know practically nothing) and multivariable calculus and differential equations (of which, again, I know practically nothing).

Emilio Pisanty

@heather yeah, that sounds like a good idea

keep it around and see which bits become accessible as and when your maths oomph increases

user3625380

@MarkMitchison I'm not sure, actually. I encountered the example with the singlet state somewhere and was as puzzled by it as you are. @EmilioPisanty I don't really have any more insight except what Wikipedia says because everywhere they are just defined like this. Mathematical equations, and the respective UxU vs UxU* invariance.

heather

16:32

@EmilioPisanty, okay, thank you

Emilio Pisanty

@heather also: multivariable calculus and (O/P)DEs are nice for QM, but the real essential is linear algebra

@user3625380 If you don't know what sort of Hilbert space your states live in, then it seems to me that you've got a fair bit of reading to do before you can produce a well-posed question.

user3625380

I need some physical insight intot he construction of each, why they're called the way they are. I picked up Werner's original paper too, but it just reiterates the math.

terdon

@koolman is there any particular reason you invited me here?

heather

@EmilioPisanty, I'd like to think I know enough linear algebra to tackle QM

Mark Mitchison

@user3625380 If you don't even know what the symbols mean here, you need to go back a step or two. What is the actual problem you are interested in?

Emilio Pisanty

16:34

@user3625380 ^ that

@heather from what you described earlier you probably do. But you can never really know too much linear algebra

:33690311 this is the physics chat room? or did I click into the wrong one today? :-P

heather

@EmilioPisanty, okay =) I do have a linear algebra textbook. Perhaps I'll investigate vector spaces a bit (when I first read about them I was more than a little confused).

user3625380

@MarkMitchison No, I understand the symbols. You didn't ask about the symbols except for what U is, which I've added. @EmilioPisanty I understand the Linear Algebra. I don't understand the physical interpretation, and why they're different.

Emilio Pisanty

@heather what LA textbook have you got, that neglects to mention vector spaces?

@user3625380 If you understand the linear algebra, then you can answer my earlier question - is this for qubits or something more sophisticated?

@heather I really loved this one in undergrad

amazon.com/Linear-Algebra-4th-Stephen-Friedberg/dp/B003YNXP7U/…

user3625380

@EmilioPisanty any bipartite system. They can be qudits as well. There are certain constraints on the parameters that classify them as separable states, bound entangled, or disstillable.

heather

@EmilioPisanty, no, it does mention vector spaces, I mean that when I read about them it didn't make sense. I'll look at that book

Mark Mitchison

16:37

@user3625380 I asked what is the symmetric and antisymmetric subspace, and you said you don't know...?

John Rennie

@heather just don't tell Daniel you're reading Griffiths. He hates that book :-)

heather

@JohnRennie, seriously? Why?

user3625380

@MarkMitchison Not physically, no. Physical interpretation is what I want.

Emilio Pisanty

@heather from a certain perspective it often feels like QM for kids

heather

(::starts to question Griffiths::)

@EmilioPisanty, oh, I am a kid =P That's perfect then =)

Emilio Pisanty

16:39

and it does tend to oversimplify some things

heather

well teenager

but whatever

John Rennie

@heather Have a look through this search of Daniel's posts on the subject of Griffiths

Emilio Pisanty

If you do pick it up, then keep in mind that it's an intentionally simplified picture of QM, and that there's plenty of subtleties that he doesn't go into.

@JohnRennie yeah, but when he says things like

Sep 16 at 19:28, by DanielSank

@AdityaDev My first book was Griffiths. It is bad. Then I read Shankar and actually understood things.

I can't really recommend Shankar to heather

Mark Mitchison

@user3625380 OK, well I suggest that you provide at least the mathematical definition of these symbols

Emilio Pisanty

I would be interested in what @DanielSank would recommend at, or slightly below, the level of Griffiths

heather

16:42

@JohnRennie, lol

@EmilioPisanty, huh, I've been recommended Shankar by a lot of people

which again I was saving for after classical mechanics and more math

user3625380

Shankar is really good, but it may be a little advanced for a first timer.

It shouldn't scare you away. But it's awesome.

Emilio Pisanty

@heather Oh, it's a plenty solid textbook. I just don't think you've got enough maths to digest it yet, and having a go at that one before it's time will leave you a bad taste for no good reason.

Hiro

I know this is unrelated to physics, but the math chat seems to be really focused on a complex problem that they don't have time to look at mine, so I'll go ahead and ask mine: Compute $$\sum_{k=2}^{+\infty} (k-2){8\over 6^k}$$ I am not sure how to approach this =/

user3625380

You can try Modern Physics by Arthur Beiser

heather

@EmilioPisanty, oh, I see. I know I don't have enough math for anything formal in QM just yet =)

or at least, that's what it seems like.

Emilio Pisanty

16:45

@user3625380 I was going to say - I was given Beiser in my intro course and I found it pretty harmful

user3625380

@heather Arthur Beiser or even the Feynman Lectures.

@EmilioPisanty Shankar in the intro course? Haha, I can imagine!

Emilio Pisanty

but then there's two Beiser books so I'm trying to see which one it was

heather

modern physics, okay

my dad has a copy of the feynman lectures, I've been starting to read through those

user3625380

@EmilioPisanty, really?

This one? amazon.com/Concepts-Modern-Physics-Beiser-Arthur/dp/0072448482/…

DanielSank

@MarkMitchison hello, sir.

heather

16:49

@DanielSank, hello =)

user3625380

@MarkMitchison updated the question, btw.

Slereah

0

Q: How hot was the jet fuel at WTC?

http://911research.wtc7.net/mirrors/guardian2/wtc/how-hot.htm Excerpt: That is, we need to calculate the energy needed to raise: 39,857 kilograms of water vapor to the temperature T° C, 97,429 kilograms of carbon dioxide to the temperature T° C, 349,680 kilograms of nitrogen to the temp...

thermodynamics

heather

@user3625380, thanks for the beiser recommendation - it looks very interesting!

user3625380

@heather Enjoy :)

DanielSank

@EmilioPisanty wow. I guess I'm consistent.

@heather hi

John Rennie

16:54

@Hiro Rearrange it into: $$\frac{8}{6^2}\sum nx^n$$ where $x = 1/6$

heather

darn

Emilio Pisanty

^ and use the fact that $\left[x\frac{d}{dx}\right]x^n=nx^n$

heather

I got recommended a good starter classical physics book by Mew, but the company's in australia and I can't figure out how much shipping is

and it's probably way too much

DanielSank

@heather I dislike it because it teaches a very specific, mathematically difficult part of quantum mechanics.

For the first two(?) chapters, the book focuses on solving the Schrödinger equation in the position basis. This requires partial differential equations.

Emilio Pisanty

@user3625380 You also need to clarify what you mean by $U^*$. From your question it reads like the hermitian conjugate, but quantiki puts it as the complex conjugate quantiki.org/wiki/isotropic-state

the difference between the two is huge

starting with the fact that the complex conjugate is not basis invariant

... so, if your question does not refer to some specific basis as canonical, ...

user3625380

17:07

@EmilioPisanty It IS the complex conjugate. * is always used to denote complex conjugate. the dagger is used for Hermitian.

I don't know why you think I meant Hermitian...?

Emilio Pisanty

@user3625380 No. Plenty of mathematicians use $^*$ for hermitian conjugate. You need to be specific.

Particularly because the complex conjugate is not a natural structure

user3625380

They only use it for Hermitian operators, when the two are interchangeable. :)

Emilio Pisanty

(in the sense that there isn't one unique complex conjugate, or one unique transpose, and on different bases the operations will differ)

@user3625380 that's not true. The only thing that happens is that for hermitian operators in a given basis the complex conjugate and the transpose coincide

@user3625380 As a trivial example, consider the matrix $\begin{pmatrix}0&1 \\ 1& 0\end{pmatrix}$ on a given basis $\{e_1,e_2\}$ (equal to its transpose and to its complex conjugate), and the matrix for the same map in the basis $\{e_1',e_2'\} = \{e_1,ie_2\}$.

you get $\begin{pmatrix}0&i \\ -i& 0\end{pmatrix}$, which is equal to its hermitian conjugate, but gets a sign flip under the transpose and complex conjugation.

See the sort of fragile structure that you're assuming is rock-solid?

user3625380

Obviously it's in a given basis. :p Anyway, respectfully, I think that only someone in theoretical QI who already works with these states and already knows the definition would be able to answer since I guess they'd know the physical interpretation rather than just the math like you and me. I'll leave now, getting late, but thanks a ton for the suggestions, I've made edits accordingly. Have a good night, guys (well, it's night here). Cheers. :)

Emilio Pisanty

@user3625380 It is up to you what sort of audience you want to reach. If you're looking for someone that's directly steeped in exactly the notation you're using, then go ahead. However, the criterion of the site is that the questions need to be useful for future visitors, whom an ill-posed and ill-explained question (like the current form of yours) won't help very much.

ACuriousMind

17:21

@DanielSank Well done, you, then!

DanielSank

@heather kleppner and kolenkow is a very good first classical mechanics book.

@ACuriousMind Yes. It's aging now. I expect good things.

John Rennie

@ACuriousMind: assuming your presence in the chat room means you have some free time, please will you cast your eye over this proposed answer

and say if you you think it's worth posting or whether the physics world is better off without it

ACuriousMind

Let me catch up with comments and flags first, then I'll have a look

John Rennie

@ACuriousMind no urgency, any time in the next 60 seconds will be fine :-)

ACuriousMind

@JohnRennie If you emphasize the point in your last paragraph about this not being special to the number operator a bit more (i.e. this happens whenever the vacuum is not an eigenstate of the observable measured) then it's good to go, I'd say.

Mark Mitchison

17:30

@DanielSank Hey :)

DanielSank

@JohnRennie I

John Rennie

@DanielSank I left the answer deleted so I could make sure it made sense before anyone saw it. I'll undelete it now if you want a look.

ACuriousMind

I think Daniel can see deleted posts

"I" means he either didn't finish typing or it's a very cryptic message ;)

John Rennie

I thought you had to have 20k rep?

ACuriousMind

nope, 10k for seeing deleted posts

20k gives...access to a better analytics page and slightly expanded deletion rights, I think

John Rennie

17:35

OK, so Daniel is adopting the Zen approach to chatting :-)

DanielSank

@JohnRennie I can see deleted things.

@JohnRennie no, my phone is being annoying.

John Rennie

I cited one of your favourite papers in my answer!

DanielSank

@JohnRennie eh?

John Rennie

@DanielSank Observation of Zero-Point Fluctuations in a Resistively Shunted Josephson Tunnel Junction

DanielSank

Oh, Koch's paper!

Yay

John Rennie

17:40

Indeed. You suggested I read it when I first started asking about vacuum fluctuations, and very interesting it was too.

ffahim

Hlw everyone...

DanielSank

@ACuriousMind @JohnRennie I think it would be good to point out that a single mode in the ground state has vacuum fluctuations in e.g. X, and then go on to fluctuations in n.

Vacuum fluctuations in particle number is the "advanced" case.

I think John's answer is very good.

Probably the best one we have on vacuum fluctuations.

John Rennie

@DanielSank it's your and ACM's answer really. I just edited it :-)

ffahim

I had a question in my school xm... if t=0 and u apply 15 N force on an object having 10 kg, will there be any acceleration though the object is at rest.... ?

DanielSank

@JohnRennie eh?

In any case, I think that last paragraph is important.

John Rennie

17:46

@DanielSank I've discussed vacuum fluctuations with the two of you several times over the last couple of months, and I just pulled everything from those discussions together to make that answer.

ffahim

@JohnRennie. @DanielSank... or anyone else... pls help me...

DanielSank

Could help to even draw a ground state wave function is something. ::Shrugs::

John Rennie

@ffahim please don't randomly ping people

Anonymous

@ffahim Yes, it starts accelerating. F=ma ....

John Rennie

Acceleration is given by Newton's second law $F = ma$ rearranged as $a = F/m$. You are given $F$ and $m$ so you can calculate $a$.

Whoa, I just got a serial downvote!!

ACuriousMind

17:50

@JohnRennie Uh, looks to me as if it's 8 hours old

John Rennie

Yes.

ACuriousMind

That's not "just" :P

DanielSank

@JohnRennie a serial downvote?

John Rennie

Eight of my answers have been downvoted, and apparently randomly since the answers span a range of subjects.

I wonder if I was rude to someone 8 hours ago ...

Anonymous

@JohnRennie Maybe, someone is angry at you. It once happened to me on Math SE :-P.

DanielSank

17:53

Pfff, n00bs.

Anonymous

I lost 200 reps in 1 hour

DanielSank

I was accused of being a psychopathic monster for trying to explain signal processing to someone.

ACuriousMind

@JohnRennie Just wait for the script to catch that, seems pretty blatant. I think it runs at 3 am UTC each day.

John Rennie

@S007 I'm sometimes less polite than I should be when criticising someone's posts. This isn't deliberate, it tends to be if I'm reviewing first thing in the morning (at 5 a.m.!) and I'm a bit tired and emotional.

ACuriousMind

@DanielSank Heh, "fun" times :P

John Rennie

17:55

But in this case the only comment I made around that time was (I hope) a helpful one.

Anonymous

@JohnRennie I understand :) Anyway the reputation gets restored within a day. Mostly new users who aren't aware of the suspicious voting pattern detecting script do it :-P

Anonymous

Happens even if someone upvotes too many of your answers in a day

Anonymous

:-D

John Rennie

@S007 it's irrelevant anyway. I decided when my rep passed 200k that I'd start using it up on bounties, e.g. on this thoroughly awesome answer.

So the -16 rep loss in serial downvotes is inconsequential.

DanielSank

@JohnRennie You and @EmilioPisanty are the bounty-barons.

You are the rich, giving to the deserving poor.

John Rennie

18:01

I should do more bounty awarding. However I don't see that many really great answers.

My definition of a really great answer is when I think I wish I could have written that answer.

DanielSank

@JohnRennie Clearly you haven't perused my answers list.

ffahim

Well. How ?.. t=0 means no displacement... so how there can be acceleration ? @S007

ACuriousMind

@DanielSank What modesty! (But most of your answers really are great, I'll grant that :) )

John Rennie

I really like:

90

A: Which is more fundamental, Fields or Particles?

This is a tricky question because it asks about the meaning of words. People use the word "particle" to refer to various, not always well defined, notions in physics. In the end, I think the simplest and more correct single way to categorize the terms is to interpret "particle" as "excitation of...

ACuriousMind

@ffahim It's unclear what you mean by "t=0 means no displacement". The acceleration is the second derivative of displacement. The derivative of a function can be non-zero at a point even if the function is zero.

John Rennie

18:08

But what have you answered for me lately? ;-)

@ffahim suppose you're in a car that is stationary, i.e. v=0, and when your stopwatch reads t=0 you press the accelerator. Is the car going to accelerate?

DanielSank

@ACuriousMind It was an obvious joke... :\

@JohnRennie Good point.

John Rennie

I think this site is at its finest when an answer takes a complicated subject and explains it in a way that is (to quote Albert) as simple as possible but no simpler.

Sometimes an answer will see past the confusing detail to the real core of the matter and explain that basic principle elegantly and clearly. it's those answers that really make this site the great place it is.

Anyway, I have to finish my book about werewolves and drink a beer or two in the process. See you all tomorrow.

DanielSank

18:33

@JohnRennie yes

Anonymous

@ffahim Why does t=0 mean no acceleration ? :-O Suppose you push any object at rest ( apply force ) even if it has no velocity it will start moving (neglecting friction). How does t=0 matter ?

Anonymous

@JohnRennie Well, you do have tooooooooooooooooooo many rep points to actually worry about down-votes :-P BTW you wake up so early! Who wakes up at 5 in the morning! :-P I guess you sleep very early :)

Emilio Pisanty

19:07

@DanielSank I'm not sure anyone over 10k rep gets to describe themselves as rep-poor

It's not quite enough rep to give any amount away and not feel it

but you're essentially made

DanielSank

@EmilioPisanty Hahaha true

@EmilioPisanty Made like a mafia member?

dmckee

@JohnRennie Hmmm ... I think the script will reverse those. And then I'll check some tools we have. Others have been treated to this approach lately.

heather

19:49

hello

Kyle Kanos

20:03

In my opinion, although the dupe candidate is essentially the same question, it is clear only for the majority of the reviewers and not for the googlers of the future. A layman-focused answer here would be from their viewpoint much more understable and very useful, thus I vote this question to "leave open". — peterh 27 mins ago

Isn't that kinda defeating the purpose of closing questions as a duplicate?

Sanya

@KyleKanos it is also not taking into account that it should be the actual question which is under review and not the possible answers that someone could think about - but that's just my opinion of course

ACuriousMind

20:19

@KyleKanos Yes, the point is that people finding the closed question will be led to the dupe target and get their answer there. Alas, some people will never understand the way this site works :P

Kyle Kanos

@ACuriousMind That was my impression and, hence, my response back to peter

Sanya

could anyone remind me how to access the bookmarked conversations for the hbar?

DanielSank

@Sanya Go to the page with all the chat rooms.

See that little link "info" up near the top right?

Sanya

@DanielSank found it; thank you a lot

DanielSank

sure

heather

20:46

so, kleppner and kolenkow doesn't appear to have langrangian/hamiltonian mechanics; do I need to read something like goldstein or landau to get that?

DanielSank

21:03

@heather well, it's not a bad idea to learn basics first.

I don't know of any good books that treat Lagrangian/Hamiltonian mechanics.

heather

@DanielSank, I know; I just kind of wanted to have a list of books to go through so I can have them all ready, so to speak. =)

Sir Cumference

Do degenerate gases fall into the realm of "condensed matter physics"?

DanielSank

21:20

@heather partial list

Kyle Kanos

21:36

10

Q: Any good resources for Lagrangian and Hamiltonian Dynamics?

I'm taking a course on Lagrangian and Hamiltonian Dynamics, and I would like to find a good book/resource with lots of practice questions and answers on either or both topics. So far at my university library, I have found many books on both subjects, but not ones with good practice questions and...

classical-mechanics lagrangian-formalism resource-recommendations hamiltonian-formalism

@heather: see above

I've heard good things about Taylor's book, but never used or read it

I've skimmed Marion's text and thought it good

But I was taught from Goldstein in my MS program & Saletan in PhD program (though it wasn't actually used in the course)

I liked the former (Goldstein) and not Saletan (mostly because we were not required to read it nor assigned any problems for it, so it was barely ever opened before selling it off)

Sanya

@KyleKanos thanks for quoting that thread, the list is actually insteresting. Sometimes I'd like to just take a sabbatical year (or two, or three, or ...) to read books ...

Emilio Pisanty

Hey @Sanya

one quick reference

290

Q: How does deleting work? What can cause a post to be deleted, and what does that actually mean? What are the criteria for deletion?

What circumstances can cause a question or answer to be deleted, and what does that actually mean? How can a post be deleted? When can't I delete my own post? Can I see a list of my deleted posts? How can I undelete one of my posts? What does deletion mean for a post? How do votes to delete wo...

support faq delete deleted-questions deleted-answers

you were worried that closed h/w questions might get deleted before you got to them

> The system will automatically delete closed (not as a duplicate), unlocked questions with zero or negative score having no positively scored or accepted answers or pending reopen votes, that were closed 9 or more days ago and haven't been edited in the past 9 days.

Sanya

@EmilioPisanty I was not worried, I saw it in my flagging history

Emilio Pisanty

@Sanya how do you mean?

Sanya

because some people actually delete their questions by themselves

Emilio Pisanty

21:45

@Sanya ah

Sanya

it should be a reasonably small number though

Emilio Pisanty

That requires a bit more rep

the 10k tools have a Recently Deleted tab

Sanya

and thanks for reading all that :)

well yeah, I'm not too close to that yet ... :D

Emilio Pisanty

@Sanya oh, I'm about halfway through

Kyle Kanos

@Sanya Haha, I hear ya

Emilio Pisanty

21:47

Just to check - you're aware of the Stack Exchange Data Explorer?

if not, it's a useful way to get data

if you are, then I'm just a pompous mansplainer =P

Sanya

@EmilioPisanty I am aware that it exists, I'm not really able to use it

@EmilioPisanty you most definitely are not

Emilio Pisanty

@Sanya ok, fair enough

I've managed to dreg up some vaguely competent sql from what I learned in highschool

lemme know if there's SEDE-accessible data you'd like help having a go at

Sanya

@EmilioPisanty thanks for the offer - I'm not quite sure what I'd like to get out of it, but I might come back to the offer

@EmilioPisanty my mum convinced me to do latin instead of IT in highschool - I'm still unsure of whether that might not have been a mistake :D

Emilio Pisanty

@Sanya it's a reasonably good way to look at all (non-deleted) closed questions

Sanya

but honestly, you did sql in highschool? I'm impressed

Emilio Pisanty

21:50

btw I just had a look at the Recently Deleted 10k tab

it shows me 45 deleted questions

oldest timestamp is 2016-11-21 13:32

2 days ago

Sanya

that's quite a number

Emilio Pisanty

@Sanya yeah, it is

Sanya

well, let's just hope I didn't miss too much then

Emilio Pisanty

and goodness, there's a heck of a lot of cruft there

If you want to repeat the experiment and keep an eye on that channel, I'm happy to help

if it's just checking in every day or two and taking note of h/w questions deleted by OP

then that's not a problem at all

this one is fun

physics.stackexchange.com/questions/292405/…

@KyleKanos might enjoy it

Sanya

that's a great offer - I'd just like to postpone it a little bit, the time until christmas will be a bit hectic

Emilio Pisanty

21:55

@Sanya fair enough

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