There's no way people can understand this crap.

@0celo7 Joking or serious?

It's just a cartesian product

It's not rocket science

Because this really isn't harder than understanding what $2^\pi$ does at all.

$A \times B = \{\langle x, y\rangle \vert x \in A \wedge y \in B\}$

Since B has no members, that set is empty

@ACuriousMind Michael (my linear algebra TA) tried explaining Zorn's lemma and AOC to me for an hour straight. I still have no clue what it's about.

I cannot understand it.

@Slereah you have iTunes?

Technically

I need to see if this album is released on Monday

and it's Monday where you are

I only have it on my phone and my phone is dead right now

@0celo7 Zorn's lemma and the axiom of choice are weird. Functions between sets are not

Bah humbug

I'll make you a deal

I'll understand functions between sets when you help me with my balls

I don't see what I would get out of that at all.

@JohnDuffield That has absolutely nothing to do with the definition of a tensor.

@ACuriousMind dude please just help me with the balls

He needs help.

@ACuriousMind why have you been helping me so far?

what did you get out of that

@ACuriousMind that was what I thought, thus my confusion about the statement they make, and I quote "for equilibrium, we must have |F_s| <= u_s|F_n|". I'm sure they're right (and they arrive at the same answer in the end), but I just got really get what the relation to the equilibrium is.

@ACuri

@ACuriousMind (personally, I just calculated |F_s| and then the force acting in the opposite direction, took the difference between that and the role acting in the same direction as the friction. (its asking how much force must the role apply, to keep a box on a incline static)

@JustDanyul Yeah, I'd say "they" misspoke there.

@ACuriousMind ok, well, thanks. i was worried I completely misunderstood something :D

@ACuriousMind thanks for putting my mind at ease :)

@0celo7 When the better half speak, I listen.

Any way, the short answer is that every year there are student who will obviously have no trouble finding themselves a respected place in society.

@dmckee well, I respect most people

Which is not to say that I expect them to become famous. There is a lot of time and a lot of oportunities to be surprised between undergrad and famous.

but that's not what I was talking about

@dmckee have you ever met someone and known they would be somebody big some day?

I assume that integrated over my career someone I teach will become something special. But I don't pretend to know who.

I've known people much smarter and more able than I to flame out early. And I've seen some I thought we not my equals get much more prestigious jobs than me.

So, while I may have my favored candidates, that as strong a statement as I'm willing to make.

How does one integrate over a carreer

Do you just take the boundaries

It's a sum.

You draw a really tall ess, and write "postdoc" at the bottom and "emeritus" at the top, of course.

Who's the most famous person you've taught so far?

@dmckee career doesn't start freshman year?

I've been told I could publish next semester

I'd have to do a lot of work

but it's not out of the picture

@0celo7 That part of the sum is usually negligible. A dilligent student should prove this for his or her own case, however.

More seriously, I was talking about my career teaching, so I suppose it could start at the beginning of grad school (TA time).

It must be an engineer thing that seniors TA

@dmckee your steelers beat us today 8(

ooooooo

fite fite fite

Go Sportsball!

@ACuriousMind @Slereah how'd your teams do

My Steelers? Never rooted for them in my life and don't follow the pro grame to speak of.

Roll tide.

@dmckee Does your school have a team?

I don't have a team

>school

>team

@0celo7 seems to have a cultural clash

commies raus

The notion of schools having sports teams is very American

@0celo7 Sure. In division II. Go MoSo. I bleed green and gold, and all that. But they aren't on TV except locally.

@Slereah The notion of freedom and awesomeness is very American.

Sorry, must have been Kyle @dmckee

@Slereah I agree with some of that.

*all of that

@skullpetrol how long has user been trolling in the math chat?

Off and on for about two yrs

It's sad.

jesus

does he always call people homophobes

@ACuriousMind no matter what I do, I'm not that guy

always remember that

I think you mean homomorphic

hmm

He is a very confused person. He needs professional help.

what are humans, topologically?

@0celo7 Coffee cups, of course.

@dmckee hmm

let's use the GB theorem

get some topological info

Humans are of genus 2

what's the Ricci scalar of a human

One opening mouth to butt

One nostril to nostril

yes...

Which means that humans have a metric conformal to the hyperbolic space metric

What about the ears?

@ACuriousMind those end

Unless you burst your ear drums no ear holes

the ear does not go anywhere

so those are just "dimples"

smooth them out

So

@0celo7 The seniors TA thing is very school dependent. At You Can Study Buzzed, in the early '90s seniors would be hired to grade exams for minimum wag and pizza (did that a few times), but only grad students could be TAs or regular graders. At my current place we have no grad students so juniors and seniors can become TAs for class credit with instructor approval.

$\mathrm{human}\cong T^2\#T^2$

> At You Can Study Buzzed

huh?

@0celo7 No, they connect to the back of the throat. It's why you can pop your ears on a plane.

@dmckee really

where

No. I think @Slereah is right on this. The connection is to behind the eardrum. Sigh.

we're assuming an intact human here

That's what I get for thinking I'm smart. Or at least full of facts. Again.

hmm

Also any piercing adds to the genus

we have two holes for excretion

how does that work

the peehole doesn't extend to the other side, though

right

take a sphere

drill a hole to the half way point

then split and go at 90 degree angles

drill all the way out

what's the genus

rather, take the ball

do that, then what is the genus of the boundary of the ball

A sphere with one hole is $R^2$

A sphere with two holes is a cylinder

$S \times R$

human topology is too hard

what are the open sets

@dmckee So what are your first semester kiddos doing?

@0celo7 I'm teaching the algebra/trig version (pre-med, pre-nursing, pre-dental, pre-pharmacy, biologists, biochemists, etc...). We've gotten as far as angular momentum at this point. About to talk about simple harmonic oscillation. But first they have a test. ::cackles and dry washes hands::

@dmckee Wow, that's further than we are??!

@dmckee what do you think should be in first semester physics, anyway

@0celo7 I believe you started later than we did and they have learned only the most cursory versions of some things (like angular momentum, for instance).

I have no complaints with my physics class, really

We're covering all the first semester things and the problems are nontrivial

@0celo7 Our curriculum for the course calls for kinematics, forces, circular motion, eneergy momentum, rotational motion, angular momentum, oscillation, elasticity, heat transfer and thermal equilibrium, waves and sound.

We rarely get to the waves.

Wow, that's our whole year

How the hell do you go that fast??

@0celo7 But again, you are expected to know it in depth and well. These guys only skim the surface. And some can't keep up even so.

We go that fast by not doing any really interesting problems and giving them a break in terms of how hard we let the math actually get. Remember most of these students not only haven't had calculus, but are unwilling to take it.

@dmckee derp, "When considering rotational motion, the mass of an object can be considered as concentrated at its center of mass." Is that true?

They're memorizers not engineers :P

I'm bad at physics

I'm not even sure what they mean by "can be considered as"

@0celo7 Generally no. For the purposes of computing the torque exerted by an object's weight yes if the gravitational field is constant.

@dmckee Ok, that was my gut answer.

But I'm not sure what they mean by it

Presumably they're talking about static equilibrium, in which case the line makes sense.

@dmckee The line makes sense?

looks like you have an answer on this

btw I would probably know that if I read the book

or paid attention

Wow! @dmckee You \mathrm your derivatives?

@0celo7 Recently. There is actually a standard that calls for it, though there is much resistance in some communities. See also tex.stackexchange.com/questions/14821/… .

I'm also toying with the physics package which (a) takes care of that detail for me and (b) make the detail configurable, so I can easily changing it later if I change my mind.

FWIW I use physics.

@dmckee Where exactly is there "much resistance"

I can get "I'm too lazy"

But how can there be resistance

Resistance as in mathematicians saying "I've never done it that way before and I'm not starting now."

ah

A standard only has authority if people pay attention to it.

I just think it looks better upright

I don't know that the upright or slanted thing matters much to be, but the operator spacing does.

It shouldn't look like just another letter to multiply together.

In geometry, it's very annoying when there are three ds floating around with different meaning

but

I don't know how to fix it

maybe upright some of them?

@dmckee so you don't like $\int abcdx$

@0celo7 Nope.

Anyone know why xkcd links get one-boxed some of the time?

@dmckee Doesn't one-box if you use https

Ah ha!. Thanks.

Firefox uses https by default so copying the link from the address bar foxed me.

acm never fails to lurk

my water from my water cup tastes strange

IT'S OUT

IN EUROPE

DAMMIT

hardstyle.com/album/radical-redemption-the-one-man-army/65017

oh please just let me get it on American iTunes

@dmckee Does music like that just confuse you?

I know it confused my father (a lot older than you).

My brother likes it, and I'd wager you're about the same age.

Maybe a little older.

3 years if your profile is correct.

Never cared much for club music from any era, and can't parse the genre lines you insist are there.

Well, there are people who will divide hard dance by country. I can't do that.

And there are people who like both kinds.

Country and western.

Wait

Country is not western?

And if you don't know what movie I got that from I'm going to go cry quietly in the corner.

Or is that a joke

We've established I'm culturally impoverished

::curls up and sobs::

Don't feel bad

Must've been a decade or so since I watched that one. Also, it was dubbed.

@ACuriousMind As long as they didn't dub the musical numbers.

What movie is that?

The Blues Brothers

Never heard of it.

@dmckee How much granularity do you have?

You know, if you don't know that movie then you've missed a number of good inside jokes over the years.

Can you distinguish

@dmckee i.e. can you tell that these are completely different in tone, intended audience, etc.?

@dmckee I think they didn't

It's not completely absurd, though, many songs sung by protagonists do get dubbed, especially in older films

@dmckee When you say you can't tell genres, you might just mean you can't detect the difference between rawstyle and modern hardcore, which is about 10-15bpm and some characteristic sounds.

But if you can't distinguish house and hardcore...that's pretty severe.

The notion of dividing genre on tempo lines is simply foreign to me, though I suppose I can see how people who like that kind of dancing would care.

All the artists I would put down as series long term keepers use a wide range of tempos to fit the emotional content of the song.

I'm not a dancer but I classify my music by tempo.

Well, I've never seen a hardcore song that wasn't very aggressive.

Happy hardcore is not real hardcore.

I'll pull a Scotsman all day long on that one.

@dmckee If you listened to the above, certainly you noticed something other than the tempo being different.

I'm trying to find any sad music I own that isn't rap.

There are some pretty damn song rap tracks.

Probably considered sad. That's about as sad as hard dance will get.

Mind you, I have a piece of software I use to classify songs by tempo and add them to my workout mixes for different activity levels, but the songs are drawn across my library.

Well, all of my music is either happy, angry or whatever rap is. It's hard to classify that is a lot of cases.

I have no clue what Skrillex is, either.

Besides noise.

@0celo7 Happy, angry or sad?

I don't even begin to know how to classify a song about twerking and big asses.

Besides being awesome, ofc.

@ACuriousMind Was zur Hölle?

:)

Lol das kleines Mädchen

@0celo7 I think about two thirds of my friends can sing along with that

@ACuriousMind Du hast komische Freunde

Kannst du mitsingen?

Yes to both

@ACuriousMind Meine Deutschlandreise ist in einem Monat, ich muss üben :o

Danke @Zizouz212

Hi!

Hallo

Wir sprechen nur Deutsch hier

A...wobbuffet?

Sorry, I don't speak German :/

@ACuriousMind Yes indeed.

Woingenau, @ACuriousMind

Warum weis ich das...

May I ask why you are speaking in German?

@ACuriousMind Should there be a ß there?

@Zizouz212 I'm making a glorious return to the mother land after a 4 year hiatus in a month

@Zizouz212 Probably my fault, posted a German song

ACM is my mother duck

Aah. Cool.

Hmm

The mother duck thing probably doesn't make sense to you.

Probably doesn't make sense to him either.

I'm not going to ask, or even try an translate that...

Smart man!

@ACuriousMind Is that last German sentence correct?

@0celo7 No, ß needed indeed

then when do you need it

@0celo7 For words which are written with it :P

There really is no pattern

is weiß not a thing?

@ACuriousMind I keep saying English makes more sense

Anyways.... See ya later peeps :)

Oh, you misunderstood me. I meant: No, that was wrong, an ß is needed indeed

bye

ah

OH, there's a comma there

dammit

Seriously?

What is wrong with people.

@ACuriousMind what is "seriously"

Echt? Or is that more "really"

Is Echtlich a thing?

IT'S OUUUUUUUUUUUUUUT

oh this is gonna be so eopic

::ruins eardrums::

Oh god this is GOOD

VERY GOOD

random screeching + 150 bpm drums + epic chanting = very good

6 tracks in. Album is a success.

This is epic.

Pulp fiction sample. 10/10 album

@dmckee Nice.

@0celo7 link?

@0celo7 : it's got everything to do with the definition of a tensor, because that's the history of it. But hey, if you want to lurch into dismissal mode about something you don't know about, and doubtless call me names too, well, that's one way to cling to ignorance.

@JohnDuffield I won't call you (or anyone) names

I don't get pullback notation

Why don't they just write $f(\varphi(p))$

Surely that is more immediatly readable

@0celo7 seriously = ernsthaft

@JohnDuffield Incorrect.

@ACuriousMind Did you ping me?

@Danu Mh...I don't think so?

Today, November 9th, 2015, is the 5 year anniversary of Phys.SE's public beta. Congratulation! (The 5 year anniversary of the private beta was last week, November 2nd, 2015.)

November 2nd, 2015 also had a new record: (almost) 133k total page views in a day.

Managed to get banned last night.

The flagger said he did it for revenge and I think he claimed to be sockpuppeting to get out of a ban I apparently caused.

@Qmechanic Nice.

Wait

How do we know if a free particle is massive or tachyonic

The mass term doesn't appear in the EoM

@0celo7 With the way you were acting when I left, I can't say that I'm majorly surprised to hear that.

what condition imposes $\dot x ^2 = \pm 1$

Hm

@Slereah The relativistic point particle is a constrained system, you need to remember the constraints together with the e.o.m. to have full information about the system

What is the constraint

and how does it derive naturally from the Lagrangian

$p^2 = -m^2$

Ah yes

@Slereah Just determine the canonical momentum - you'll see that it fulfills this relation, and that's how all constraints arise, one calculates the canonical momenta and observes there are relations among them which are not captured by the e.o.m. (i.e. the Legrendre transform is singular)

I suppose since we have a lock on the sign of $m^2$, that imposes the sign of $\dot x$

Also one thing I wonder is

Is the mass a relevant physical information?

^lol

Or is only the square of the mass relevant

oh

lol @Danu

@Slereah I think it's only the square - you can't say what negative mass would mean.

Hm

Also is the Lagrangian of a tachyon just $L = \frac{im}{2}x^a x_a$

Since the Poincare reps are classified by $m^2$, you cannot have physical difference between $m$ and $-m$ since they'd determine the exact same particle representation.

@ACuriousMind There is probably a way to interpret-away negative masses.

@Danu What?

I got banned for saying "big booty" as an example of a username that would be inappropriate.

@0celo7 Oh, that does surprise me :P

Or is it $m^2$ still for a point particle

@Danu I'm sure someone can cook something up, but I don't see any obvious way within the standard formalism

I forget

@Danu Yeah, no kidding.

Feels weird to have an imaginary lagrangian

@ACuriousMind repulsive gravity

@Slereah You're missing a square root there