The h Bar

5:00 PM

So to get from $ ^{214}_{80}\rm Hg $ to $ ^{214}_{84}\rm Po $ requires four beta decays, and that's why four electrons are emitted.

Osheen Sachdev

but where did the 6 e in the first step go?

John Rennie

What 6 electrons in the first step?

Osheen Sachdev

@JohnRennie here wouldn't 6 e be released

John Rennie

The uranium atom will lose 2 electrons with every alpha particle emitted, 12 electrons in all, so it ends up as Hg with 80 electrons, but the question presumably means you to ignore these as they aren't newly created electrons.

Osheen Sachdev

oh...not my fault :P

Thank you so much!

user218912

5:37 PM

@0celo7 I found this GR book by choquet-bruhat published in 2015. do you know it?

user218912

it looks like a more advanced version of carroll.

0celo7

Einstein field equations?

user218912

no let me link it

0celo7

Interesting

The EFE book is PhD level (not kidding)

user218912

never seen this before.

user218912

5:38 PM

amazon.com/…

0celo7

Oh

I've heard of it but haven't bothered

user218912

ToC looks good.

user218912

but I wouldn't be able to tell xD

0celo7

I'll look at it later, Redmond me

user218912

@0celo7 what does that mean?

Keep these mind

5:41 PM

@bl00 The "Bicycle Capital of the Northwest"

0celo7

Remind

user218912

@0celo7 oh you're on your phone?

user218912

ok.

user218912

nvm this book seems too advanced for me.

user218912

the first exercise is

user218912

5:44 PM

prove that a $C^1$ diffeomorphism with $f$ as a class $C^k$ is a $C^k$ diffeomorphism

user218912

I know what those words mean but no idea how to prove it.

Keep these mind

@bl00 What do those words mean?

user218912

look it up.

user218912

it's just basic math terminology.

user218912

@Obliv hello

Obliv

5:52 PM

did u change ur name again @bl00

and hi

user218912

yes.

0celo7

@bl00 Yikes

user218912

OMG

user218912

PROBLEM SET DUEDATE EXTENDED BY 1 WEEK

user218912

:D

Obliv

6:02 PM

does 100% relative humidity mean the air is water

user218912

no.

user218912

lol

Obliv

what does it mean then? lol

user218912

@0celo7 do you know how to do that?

user218912

@Obliv I think it means that the air can't hold any more water vapour.

0celo7

6:08 PM

do what?

It should just be the chain rule

user218912

oh

0celo7

F applied to its inverse is 1, so it has derivative 1

Then apply that a bunch of times?

Something like that.

user116211

Pseudo-answer:

user116211

0

A: Why does a mirror reverse polarization of circularly polarised light?

I agree with dmckee. For more details, I want to point out that if xyz is a right-handed coordinate, then after a reflection, because z is reversed, x or y has to be reversed too. It is in this new coordinate that the reflected light has reversed circular polarization when compared with the incid...

user116211

?

Obliv

6:19 PM

@mafia probably would have commented if not for the low rep

Bernard Meurer

burp

What's up?

user116211

IS it JD?

user116211

Hallo JD o/

Obliv

hi @bernard nm just studying hbu

Bernard Meurer

@JohnDuffield Hello darkness my old friend

@Obliv Same, reading some CS stuff abotu Karnaugh maps

user116211

6:30 PM

@BernardMeurer o/

Obliv

anyone know what's the difference between $\frac{\partial}{\partial x}(\frac{\partial f}{\partial y})$ and $\frac{\partial}{\partial y}(\frac{\partial f}{\partial x})$

user116211

@Obliv HORROR!

Bernard Meurer

@Obliv Both have broken TeX but in a different way?

Obliv

crap.

0celo7

Lol

Obliv

6:32 PM

I thought it was \left and \right @mafia

what was it then?

user116211

@Obliv yes.

Obliv

$\left( \right)$

..

user116211

\left( \right)

Obliv

ah I see.

Secret

[Need to refine to to turn it into an actual PSE question] We knew we can detect signs of higher spatial dimensions by finding a sequence of massive particles whoose mass is related in some way (correspond to their momentum in the hidden degrees of freedom, and we can also recover the notion of time dilation and length contraction in SR by using a hyperbolic geometriy instead. Is there exist any phenomenon that we might
anticipate in the future that cannot be explained as shaodws from a higher dimension?

Obliv

6:36 PM

@0celo7 is there a difference or no? 'cos i'm reading something called Clairaut's theorem that says they're equivalent if you define them on a disk?

user116211

@Obliv Why do you think they are different?

Obliv

because there's a theorem to say they're equivalent so maybe it's not obvious that they are the same

0celo7

@Obliv for nice functions there is no difference

Secret

[Another pre PSE queston] We knew why we don't expect multiple time dimension due to lack of initial value problem for ultrahyperbolic field PDEs. But suppose they do exists, how will they manifest themselves in possibel experiment outcomes?

0celo7

@bl00 No, I don't know how to do it, which is annoying

@bl00 I'm fairly sure it's wrong, actually.

no it's correct

Obliv

6:47 PM

@0celo7 when the function is non-continuous at some point, does the symmetry of its second derivatives break?

or does there have to exist some other condition

0celo7

@bl00 The hint she gives is wrong.

@Obliv yes

Look up wiki for the exact requirements

They probably have some examples too

Obliv

@0celo7 would you say $z(x,y) = \frac{1}{2}(x^2 - y^2)$ is continuous?

it's a hyperbolic paraboloid (saddle)

Slereah

seems p. continuous to me

Obliv

Taking 2nd partial derivatives for each variable gives me diff results tho

1 and -1

Slereah

well yes

why would it not

Are you confusing it with the condition $\partial_{xy} = \partial_{yx}$

Obliv

7:02 PM

wait what did i just do.. i'm trying to prove symmetry of 2nd derivatives

*find a counterexample

yeah I was.

0celo7

@Obliv that's smooth probably

Obliv

Ah I see what I need to do. I need to find a thrice differentiable function where the 2nd derivative differs in sign when u switch the order

0celo7

Sure

or

MartianCactus

My pleasure Marty. Keep asking the questions. @0celo7 : it doesn't point either way. Two electrons repel, and so do two positrons. But an electron and a positron attract. That's because the electron has an electromagnetic field. So does the positron, which has the opposite chirality, and it takes two to tango. Say hello to Bernard and the guys for me. — John Duffield 33 mins ago

0celo7

Just wiki it

@MartianCactus ???

Obliv

7:07 PM

$z(x,y) = \frac{x^3-y^3}{x^2y^2}$ should work I think.

MartianCactus

@0celo7 someone who answered my question told me to give this to u

XD

user218912

lol 0celo7

MartianCactus

he can't chat?

user218912

JD's ghost is still haunting you.

user218912

@MartianCactus no he's banned for a year.

MartianCactus

7:09 PM

oh

why???

0celo7

Evil mods

MartianCactus

oh :((((

when will the ban get over?

0celo7

A year

MartianCactus

like, when was he banned?

Bernard Meurer

@MartianCactus Don't listen to 0celo7, my brother only talks bullcrap

MartianCactus

7:11 PM

how much time is left?

ur his brother?

XD

Bernard Meurer

@MartianCactus Ask 0celo7

user218912

@MartianCactus 350-something days.

Bernard Meurer

@0celo7 Did you figure out whether M is going to H after all?

MartianCactus

nono how much time is left?? When was he banned?? this month? 6 months ago?

0celo7

No

Obliv

7:12 PM

@0celo7 yeah that counterexample yields $\frac{\partial}{\partial y}\frac{\partial (z(x,y))}{\partial x} = \frac{3x^2}{4xy}$ and the other one is $\frac{-3y^2}{4xy}$ and they're not equivalent for any $x,y$ right?

0celo7

Beats me

Bernard Meurer

@MartianCactus Dude, JD will be banend for about 350 more days

0celo7

I haven't taken calc 3 yet

MartianCactus

oh

D:

he should make another acc for chatting then!

Bernard Meurer

@0celo7 Was that no to my question?

0celo7

7:13 PM

Yes

Bernard Meurer

@MartianCactus No he should not. He got banned for a reason

Obliv

@0celo7 I can tutor you if you want. I'm pretty much at the forefront of this subject.

practically a phd

MartianCactus

for what reason?

Bernard Meurer

@0celo7 Sigh, I'll ask her

user218912

@Obliv tutor me too.

0celo7

7:14 PM

@BernardMeurer what reason?

MartianCactus

i thought he was unfairly banned

Bernard Meurer

@MartianCactus Being a general dick around the website basically

and he hassled the frog

MartianCactus

so he said bad words?

0celo7

@BernardMeurer flagging.

Bernard Meurer

@MartianCactus No. I say bad words all the times and I'm around

user218912

7:14 PM

@MartianCactus don't listen to his answers, they are mostly wrong and don't deal with real physics.

user218912

so ignore them.

Bernard Meurer

@0celo7 I'll hit you with a piece of turkey at thanksgiving

0celo7

@BernardMeurer Dude

Bernard Meurer

@MartianCactus Listen to @bl00

0celo7

You're not coming to DC

MartianCactus

7:15 PM

well...I think his answers are conviincing

Bernard Meurer

@0celo7 Nope, lol

But I can still make empty threats

0celo7

S wouldn't allow it

user218912

@MartianCactus that's because you don't know enough physics to be able to see how wrong they are.

user218912

just ignore his answers, they are bad for you.

0celo7

She doesn't like 3rd worlders :/

Bernard Meurer

7:16 PM

@0celo7 Which S?

AH

0celo7

M's 3rd worlders have a bad rep in the U family

@BernardMeurer B's wife

Bernard Meurer

@0celo7 That don't matter, K, R-Michigan, M and Bob like me :p

MartianCactus

"A uniform magnetic field is a place where the linear forces cancel, but the rotational forces do not. Hence when you throw an electron through the middle of a solenoid, it follows a helical path. Note though that a typical magnetic field is not uniform, and so we see linear forces too. Hence two wires like the above attract one another. But if you reverse the current in one of the wires, they repel."- is that wrong?

Bernard Meurer

@0celo7 I got it when you said "she"

Obliv

@bl00 in return you need to quickly teach/remind me how to do a piece wise function in latex

0celo7

7:17 PM

@BernardMeurer It's S's house.

Bernard Meurer

@0celo7 I'm European now dawg

@Danu Hello fellow brother

0celo7

Dude, you + me + M would be way too much stupidity and alcohol in one unit area

Bernard Meurer

@Danu Do you want to colonize some countries?

0celo7

Something would get broken

Bernard Meurer

@0celo7 We'd rek the house lol

MartianCactus

7:18 PM

eeeyyyyy how old r u bernard?

0celo7

12

Bernard Meurer

@MartianCactus 12

MartianCactus

xd

tru

Obliv

@bl00 too late figured it out.

MartianCactus

finally starting to get better at photoshop tho..imgur.com/a/wjdKB

Bernard Meurer

7:19 PM

@0celo7 This reminds me I still need to get M and R a gift for hosting me back in July

thecometiscoming.bandcamp.com/album/channel-the-spirits

0celo7

They don't need anything

Bernard Meurer

Space Jazz is pretty cool

0celo7

And you need Abbott

Bernard Meurer

@0celo7 I want to gift R some cigars, and no clue what to give M. I owe her a truckload of beer though

Jesus

user218912

@Obliv you should finish zankyou.

user218912

7:21 PM

100% worth it.

0celo7

@BernardMeurer Dude R is so mad at me

Bernard Meurer

@0celo7 If I wasn't broke af I'd totally join though. Would be fun

@0celo7 What did you do?

0celo7

Nothing. Literally. She's mad because I wouldn't be mad at her for doing something she didn't do

Bernard Meurer

@MartianCactus If you looked at my profile you'd know the answer

@0celo7 Define something

MartianCactus

i know i already looked but I wanted to get the exact number

thats y i asked

cuz otherwise, most people here are in their 40s i guess

Bernard Meurer

7:24 PM

@MartianCactus More exact than 18? You want my birthday or something?

MartianCactus

or around 30 or 35

Bernard Meurer

@MartianCactus You're wrong lol

user218912

lolwut

MartianCactus

nah

0celo7

@BernardMeurer I think it's a big misunderstanding

MartianCactus

7:24 PM

just 18

good

Obliv

@bl00 when did you finish it? I'm guessing recently?

user218912

@Obliv nah while it was airing xD

MartianCactus

oh..didnt read

the decription

Bernard Meurer

@0celo7 I was wondering what was going on, you haven't been mentioning R much I was afraid something had happened but didn't want to poke it

MartianCactus

in your profile

Bernard Meurer

7:25 PM

@MartianCactus That's what I figured

Obliv

@bl00 one that I started watching a few months ago but haven't finished yet is great teacher onizuka. It's not similar to zankyou but I really like it.

user218912

@Obliv never heard of it.

Obliv

it's hilarious and teaches good morals. One of the older animes maybe 90's

user218912

oh I don't like old things.

Obliv

Yeah I passed it at first glance since it was older. But, if you ever are in the mood to watch one I highly recommend it.

user218912

7:27 PM

ok.

MartianCactus

youtube.com/watch?v=UGPuEDyAsU8 <3

user218912

@Obliv zankyou probably has the best anime ost ever just sayin.

user218912

you should listen to it even if you don't end up watching it.

Physics Meta

0

Q: Why was this question closed as "non-mainstream" when it asked about mainstream physics?

Is this an adequate resolution of the "paradox" of the arrow of time? This question was closed on the grounds that it is not "mainstream physics", and I was referred to this page. That page says: a question that proposes a new concept or paradigm, but asks for evaluation of that concept wit...

discussion

Obliv

@bl00 u ever try eden of the east?

user218912

7:29 PM

@Obliv youtube.com/…

0celo7

@BernardMeurer Depending on what happens later today something might have happened

user218912

@Obliv yes but I didn't like it that much.

Obliv

and yeah my friend that told me to watch it also likes the ost. he said he might learn it on piano

0celo7

She bit my head off and gave me the silent treatment for 3 days

Obliv

@bl00 what about eve? the one about robots & a.i.

user218912

7:30 PM

@Obliv I watched a few minutes of that.

user218912

didn't like it :(

0celo7

Only nerds watch Chinese cartoons

user218912

you said you watched like 5 animes.

0celo7

I was a nerd in high school

Slereah

NEEEEEEEEEEEEEERD

Obliv

7:31 PM

@bl00 what do you like?

Bernard Meurer

@0celo7 Hope everything goes well man, keep me up to day via iMessage

Obliv

@bl00 the devil is a parttimer and fate/zero are really good imo.

brb.

user218912

@Obliv I only like zankyou. lol

user218912

@Obliv you should do yourself a favour and listen to the ost. in particular - walt, nc17, crystallized, von, bless, birden.

user218912

I have the original cd.

Bernard Meurer

7:35 PM

Interesting thing: I know a lot more Python than I do C, and unarguably so. However, when searching for questions to answer on StackOverflow there are always far more C questions than Python ones that I could answer, mostly because the vast majority of C questions are extremely basic.

0celo7

Oh god. There's an Asian guy in my CS class. He always comes in with Beats, unrolls the LoL mousepad and plops down a $100 mouse and $3000 gaming laptop

Also he has a chain

And isn't even that good at CS

Obliv

@0celo7 ew beats

probably an overpriced razer mouse hah. i would knock league too but some parts of it are cool.

0celo7

Yes it's a Naga (?)

The MMO one

I have a Logitech

Also he has his graduation tassel on his backpack

Obliv

that's really weird i've never seen that before

maybe a high school jersey but the tassel..?

0celo7

No the college one

Obliv

7:40 PM

oh he's a grad student?

0celo7

no

Obliv

uh...

0celo7

They gave us the tassels during "induction" or whatever

We're supposed to keep them until 2019

Mine is hanging from my bed

Obliv

what happens if u dont keep them

you don't graduate? 8^)

0celo7

Correct

It's a fee to get a new one.

Bernard Meurer

7:46 PM

0

Q: Creating a system in java or c?

I'm deciding to create a fire walking system but I can't decide whether I should write it in java or c , I'm leaning more towards c but would I be able to get it to work on windows or is firewalking more of a Linux system? Thanks all

java c firewall

ZOMG

Firewalking system?

I'm crying

Slereah

is that like a cyber bed of coal that you walk across

Bernard Meurer

@Slereah No clue, but it's hilarious

@Slereah I have a very robust firewalking system on my penguin installation

0celo7

How do computer nerds even work?

How does one learn PhD programming without going to school

Slereah

Working at it, I guess

and reading about it

Bernard Meurer

@0celo7 I wouldn't say I know PhD programming, but what I learned I did in a very simple method.
1. Set an objective (I want to make a face detection thing, I want to make an AI that mocks people, ...)
2. Learn what you need to fulfill it (OpenCV, Theano, C, Python, Vala, Scala,...)
3. Make it
4. Repeat

Or the other way around
1. Set something you want to learn how to use
2. Define a project that needs it
3. Build it

Slereah

7:51 PM

why do an AI that mocks people

I'll do it for free

Bernard Meurer

@Slereah You're french, you won't work on sundays

Slereah

The mocking never stops

There's no brakes on this train

Obliv

does $\partial_x f\mid_{(x,0)}$ mean partial derivative of f evaluated at $(x,0)$