If it is a black hole, x ray data should reveal it

@dmckee why do people come to class who pay zero attention?

why bother?

if I were a prof I'd like to interrogate certain people

@0celo7 Attendance requirements can drive this. Some people can pay partial attention while looking wholly distracted—I did that in a philosophy class where actually paying attention would put me to sleep on account of the prof's smooth and lovely, unmodulated, baritone drone.

@0celo7 I find that draining and have decided not to care more than they do.

@dmckee I'm doing double slit diffraction. I know the first maximum is 3mm away from the middle. It wants to know what the intensity is at 1.5mm.

Morally, it's zero, but when I run the numbers I get 8E-28W/m^2

Neither is the the correct answer

Any idea what's going on?

Crap. It says minimum is 3mm away...how did I get the first part right?

@JohnRennie Chemistry pls

I'm failing at oxidizing something

Good evening, all

@rob hi

I seem to mostly use this chat room to gripe while I'm grading exams late.

@rob what exam?

HAHA

Intro physics midterm, second semester. Magnetic fields due to wires.

@BernardoMeurer Memphis is a war zone. Young Dolph-Yo Gotti beef exploded -- Dolph's car shot 100 times.

He put out a pretty sick diss track, I can't blame Gotti's people.

@rob What's the worst grade?

Oh, I'm early in the pile.

Any good ones?

@rob My thermo prof says people come up with "cool looking equations"

Is that generally true?

@0celo7 Like autographs: cool-looking, but not legible

@rob No, I mean equations that are legible but came out of thin air and are wrong.

@0celo7 No, we mostly have complete incomprehension

Well, from our troublesome cases

We decided not to grade paper homeworks this semester, and it's pretty obvious that some students are doing a problem on paper for the first time during the exams.

@rob That's how Handler's EM class was

I tried to do the first two exams like that and it was bad

worked for the final and got an A in the class, but I imagine that was possible only because of a massive curve

the first test had a 50 average

@0celo7 I had a student send me a great email in the fall ... he said that he had dropped the course a previous semester because he was failing hard, returned and studied by solving problems, he's top of the class now.

He even gave a time estimate: working through all the homeworks, example problems from lecture, and previous-year exams takes him about fifteen hours per test

I sort of chant about this to my section, and they seem to be doing pretty well

But I get to grade a problem on the other sections' exams, too.

people in my circuits class do practice quizzes

I have no clue where they're getting them from

but it seems like overkill to me

@0celo7 Depends on what a "quiz" is.

@rob two problems, weekly

@0celo7 I have some "reading quizzes" that I give at the start of a class period, to get people in seats and on time. There are 20+ of them in the term and all together they are about 5% of the grade.

@rob Handler didn't even grade our exams...which is one of the many reasons why I didn't like him.

Spanier is pretty enthusiastic and grades the exams

I'll have students blow off a big homework assignment but beg me to please let them make up these silly motivation-only quizzes.

@0celo7 Does he have a TA do it?

@rob He had four TAs

Class filled up the big lecture hall in Nielsen completely

@0celo7 Is that a couple hundred seats?

@rob yeah, easily

probably 250

@0celo7 Yeah, if the exams have been stable for a while he may have a good idea what to tell the TAs to expect.

It's lovely to grade things yourself and learn from them, but it's also lovely to finish them in a finite amount of time.

Speaking of which, back to work.

Bye

Hmmm, that was funny.

?

I'm learning a new language and I've been using it to say hello and goodbye to people

But I can't do that in chat because I am 100% illiterate

What language?

I went to type and nothing happened. A strange feeling.

Arabic

Hmm

Can you transliterate?

Probably like a kindergartner.

My program is audio-only, and suggests that if I avoid writing things down I'll develop less of an accent.

I remember having to write some prayer in English in 2nd grade

It was so embarrassing

Is English not your native language?

I'd only ever spoken it

@rob It's my native language, but I went to school in Germany

Oh, interesting.

I learned German spelling formally first

But I went to church on the base

So I had to write some prayer (maybe the Nicene creed)

I didn't know it in German, so the teacher made me write it in English

I realized I couldn't spell any English words

the -tion construction in e.g. "salvation" was not something I understood

@0celo7 To be fair, my kids struggle with that one a little bit.

I think if I asked my third grader to write the Nicene Creed it would not go well for him either.

And that's not counting the theological discussion we'd have to have first.

I thought you meant your physics students :P

I think if I asked my physics students to write the Nicene Creed ... I'm not sure what would happen.

The amount of men my age with kindergarten-level handwriting is a little revolting.

@rob I don't remember the first line any more.

Anyway, cheers, see you later.

bye

@rob It was "Our Father." I couldn't spell "temptation."

@D3075 I will give you the problem

you can solve it to get back in my good graces

Hi :-)

Things got lively last night in the chat room :-)

Religion and social issues!

I wasn't fleeing :-) I generally clock out about 18:30 to slump into my armchair with a book.

Given that I start at 5 a.m. by 18:30 I'm generally feeling a bit flaked out.

I'm not as young as you :-)

Cool :-)

If you want to borrow any of my books let me know, though I suspect our tastes are too different for there to be much overlap.

@Kaumudi.H There are some unresolved legal issues. If I mail you an ebook do I have to delete that file from my PC at the same time. Am I even allowed to do it?

My approach is that I don't really care.

@Kaumudi.H I mean that if you want a book and I have a copy I'm happy to mail it to you so you can load it on your Kindle. I'm unlikely to be reading it anyway since I rarely reread books. Whether you want to delete it after 14 days is up to you.

You know you can manage books using your laptop? When you connect the Kindle to your laptop it looks like a thumb drive and you just copy the ebook files to and from the Kindle.

@Kaumudi.H As an old fart I find myself unimpressed by existential crises. I consider them an indulgence that teenagers can afford but which sensible people grow out of :-) You have to just get on with life because life doesn't care what you think about it!

@Kaumudi.H All of us have good thoughts and bad thoughts. When you're tired, ill or just feeling down you'll find the bad thoughts dominate. It happens to me as well even though my life is as close to idyllic as humans can reasonably hope for.

Why this happens I don't know. Just one of those little gifts that life bestows on us to make it more, erm, interesting!

I'm reluctant to try and advise because all I know is what works for me and that might not work or might even make things worse for other people.

Anyhow, what works for me is at all costs avoid thinking about the big picture.

Focus on the next hour or maybe the next day at most. Concentrate on getting through the next hour/day and let the day after that take care of itself.

Good, at least I'm not completely insane - or at least if I am that's two of us that are completely insane :-)

Sadly, in the next hour I have to get back to work ...

It is quite fun. I moan about work, but that's traditional :-) Actually I really enjoy it.

I disagree, I think one should tackle their problems head on

unsolved problems will always come back to bite

hello...

Howdy

@SirCumference, How are you?

@LeonhardEuler Good, you?

@SirCumference, Not much fine...

Hello @LeonhardEuler

I'm a big fan of your work

@Kenshin, hy

Why are you not much fine @LeonhardEuler?

@Kenshin I'm good

I didn't ask you

sorry lol

Oh, you capitalized "Sir" ;P

I meant Sir Leonhard Euler

but good that ur good

@JohnRennie can you please answer or up-vote this question: physics.stackexchange.com/questions/315302/…

@Kenshin, nothing much difficult

@Kenshin Upvote begging...

is that bad?

I guess

It's like those youtube comments that ask for likes

my bad

@Kenshin all I know about quantum radar is what I have found out by Googling, and that's an option open to you as well. Some of the articles are rather technical, but you could at least edit your question to describe what you've read and highlight the points you aren't comfortable with.

@JohnRennie I don't have the time to filter through google

@Kenshin Oh wait, is Kenshin your name or the guy in your pic?

I need someone to do that for me then rehash the concepts in a nice simple coherent answer

@SirCumference the bloke in the pic :D

@Kenshin so your question amounts to: I can't be arsed to research this so I want someone else to do it for me. What did your last PA die of?

lol

aren't lots of questions like that

but really, I dont want someone to do the resaerch for me

Ideally someone would already know the answer

in which case it is more efficent for me to ask them then for me to repeat the research they've already done

> Immunology is also one of my interest for a very weird reason: The arms race between the microbes and our immune systems (or immune systems of other organisms from other microbes to plants) helps inspired interesting ways to make tower defense games

Some of my technical interest are game design motivated

Nature seemed to be really good at designing tower defense and RTS games with unique strategies

i see :)

what do you mean tho by resources to help are unavailable?

oh

Does anyone know how it follows in electrodynamics that the magnetic field experienced by an electron which is being circled is by a proton is $$\vec{B} = -\frac{1}{c}\vec{v} \times \vec{E}?$$

yeah I'm interested to know what the problems are?

lol

but I thort u knew

what do you experience then?

but you said you wanted to talk about it

oh lol

I thought so

:p

so cheaky

oh k

PM me on physics.qandaexchange then

PCM?

Why are you doing Pulse Code Modulation?

Ah

Lame

I thought you were doing something cool for once :P

@Alex It follows from solving Maxwell's equations

Or rather, if you don't have the form of $\vec E$ given, all you can do is plug it in there and observe it is consistent with them

@ACuriousMind Not true

@Kaumudi.H Yes

what's cool stuff?

@BernardoMeurer ?

@Kenshin Ice

@ACuriousMind I felt like it had been too long since I antagonised you, didn't want to lose the habit

@Kaumudi.H You're only cool when you have Doom running on some form of unusual hardware

I suggest a potato

@ACuriousMind Oh okay, never seen that before.

@BernardoMeurer, I updated the chromebook without really thinking about it, and when I try to pull up linux I only get a black screen - did I break something?

(is this issue what i want?)

hi @S7S

@ACuriousMind Someone mentioned his email id in a question's comment. Is it fine or does it need to be flagged?

@YashasSamaga What would you flag it for?

idk

You are fond of flagging

nvm he removed the comment.

Why option (1) is wrong

"Tri"

for polydentate ligands, you have to use tris

engineering question

bis, tris, tetrakis

How do I get this global warming thing going

I'm cold

@YashasSamaga oh yeah , I forget about that

Morning

yo

Evening

What? It's 8:30

@BernardoMeurer I just got a Christmas card from Michelle

hello

hi

@skillpatrol, how are you?

@ACuriousMind In what sense is it true that the Hamiltonian has a basis of eigenstates? When it's symmetric and compact, sure. But that's never the case

The spectral theorem doesn't help if the spectrum is bad

@0celo7 It usually isn't in the strict sense of them being "states" or a "basis". The kets that belong to the continuous part of the spectrum represent free/scattering states and don't lie inside the Hilbert space, yet you can get states inside the Hilbert space by forming wavepackets from them. Consider the free Hamiltonian - it has no "true" eigenstates, but the plane waves $\exp(\mathrm{i}px)$ form a "basis" through the Fourier transform

@ACuriousMind Well, the spectral theorem does give a generalized basis, in a sense.

Maybe

But how does the usual sum of n's work?

I'm assuming it doesn't? But why does it work :P

@0celo7 A bit late for a Christmas card, no?

Have a very locally compact Christmas

@Slereah what?

If $V$ is the closure of $U$, is $f(V)$ the closure of $f(U)$ with some continuous function

Sounds right. Is that an exercize?

Nah

Just wondering about $J^+$ being locally the closure of $I^+$

Which sounds easier to show that way

$(-\infty, 0] \to J^+(0) \to \exp_p(J^+(0))$

Or somesuch

@Slereah Image of a closed set need not be closed.

Doesn't it if the function is continuous?

Nope.

Hm

That's bothersome

I mean just take like tan^-1

Image of the whole real line is an open interval

Oh, images. Is it at least true for preimages?

@Kaumudi.H No, why do you think so?

No, I'm not a psychopath.

he has poor communication skills (but I like him anyway)

@0celo7 There's no reason it'd be. The preimage of closure might be bigger than closure of preimage.

We don't play by no rules

How does one prove that $J^+$ is closed in the normal neighbourhood, then

and that it is the closure of $I^+$

Limits of sequences, i guess?

people aren't decent or socially adept in general. you gotta deal with it. also people are free to ignore people.

@Kaumudi.H I don't know why your problem is. I'll look at what you sent me later.

Chat is an asynchronous communication protocol, I can respond to your message when I wish. I happen to be busy right now.

If you walk up to someone doing something who is also trying to talk to other people and demand a conversation, yeah, I would ignore you.

@Kaumudi.H While I agree that certain rules of decency also apply in chat situations, chat is a bit different when it comes to how to reply to people, and also how to address people. One can have several different conversations in chat at once, which is not really possible in real life, and conversations in chat are also not bound to be real-time.

I also sometimes ignore pings - e.g. because I am busy right now or because I don't want to talk about whatever the ping contained right now or because I'd need to think some more about my reply. I don't think that's anti-social or indecent.

@Kaumudi.H John Rennie ignores me all the time, why don't you bust his balls?

Also sometimes I don't respond at all if the people in question are annoying

No, he doesn't.

@Kaumudi.H Sometimes, sometimes not.

If I don't feel I have anything interesting to say, or think the matter resolved itself already or is no longer relevant, I don't really want to dig up the conversation again.

@Kaumudi.H See above where he ignored my question

I also sometimes might just plainly forget :P

I think the proper internet procedure if he does not respond is to say "plz respond"

I doubt it'll get resurrected

@ACuriousMind plz respond

I'll hotkey this

@Kaumudi.H Several? I don't see every ping you know

I wonder if I should join in this discussion or not. I could instead do foliations, or do school stuff, or listen to Ziggy.

Boo hoo

I guess I'm going to pick the last

Hello

You should do potato foliation

Potato foliation lets you make chips

Can a foliation on the potato have nontrivial holonomy?

Foliations have holonomy?

Potatoes are $\approx D^2$ I think

onion rings have $\chi=0$

@ACuriousMind Germinally, yeah. You go around a loop on a leaf and come back to a point and see how the nearby leaves changed

potatoes have eyes so they will have nontrivial holonomy

Remove the eyes before cooking potatoes

@BalarkaSen How do nearby leaves change if I follow a loop? Holonomy for me is about how tangents change under parallel transport along the loop, I don't see how a mere foliation would give a notion of parallel transport

you mean exfoliate the potato of the eyes?