The h Bar

Danu

18:00

No, more like a German trying to say "tilde"

DanielSank

Anyway @Danu, what I wrote there is true and very cool.

Danu

twiddle, every time!

Bernard Meurer

@DanielSank hahaha, I see

@ACuriousMind Ah, alrighty

DanielSank

If you hold up a sheet of paper, the square of the area is given by the sum of the squares of the projected areas onto the walls and floor.

!!!!!

Who knew!

Danu

@DanielSank But, I don't know, isn't it kind of clear?

DanielSank

18:01

@Danu Hmmm, no

Danu

I feel like it's not that enlightening

Bernard Meurer

@DanielSank Where are you getting all this information? Are you a scientist or something?

Danu

@DanielSank Okay, maybe I'll try to draw a bit

DanielSank

@BernardMeurer wat? I used to read math books by the pool in younger days...

Danu

And see if it makes less sense then ;D

Bernard Meurer

18:01

@DanielSank I got a really neat math book! It's called The Gentle Art of Mathematics

DanielSank

Sun, Munkres's Analysis on Manifolds, and people in bathing suites. That was my summer once upon a time.

Bernard Meurer

by Dan Pedoe

DanielSank

~Sigh~

Bernard Meurer

It's quite nice

Danu

@BernardMeurer many people recommend either

Generatingfunctionology (no joke)

or Visual Complex Analysis

as amazing books

(if you're looking for recommendations)

Bernard Meurer

18:03

@Danu Any chance I'll understand what's in any of those?

:p

Danu

@DanielSank so would you prove it using induction over both $k$ and $n$?

@BernardMeurer Yeah, I think so---if you know calculus.

Do you?

Bernard Meurer

@Danu I know basic calculus; limits, derivatives and some integrals

DanielSank

@Danu I don't quite remember but it's something like that.

Bernard Meurer

But I don't have a lot of practice, so I suck balls at it, specially integrals

Danu

@BernardMeurer Give Visual Complex Analysis a try

DanielSank

18:04

As usual there are probably a few different approaches. I think you could probably do it by using the fact that determinants give volumes, and then using the multilinearity of the determinant and various other properties.

Danu

(internet will probably yield a free copy, so you don't have to waste money if you don't want to)

DanielSank

Not sure.

Bernard Meurer

71 US DOLLARS?!

Danu

@DanielSank Yeah, probably.

3075

@BernardMeurer dude that's on the low end.

Bernard Meurer

18:05

I can buy a new family for that here

2

Yikes, currency sucks

DanielSank

@BernardMeurer books are expensive in the US.

3075

@BernardMeurer yeah right.

DanielSank

People complain about it all the time.

Bernard Meurer

@DanielSank If I transfer to UCSB will you give me love, care, a fatherly figure, weekly nimm games and a pillow?

ACuriousMind

@Danu You don't need induction. For any $k$-vector $v = v_1+ v_2$ with orthogonal $v_1,v_2$ you have that $\langle v ,v\rangle = \langle v_1,v_1\rangle + \langle v_2,v_2\rangle$, and the $k$-volume is just $\sqrt{\langle v,v\rangle}$. The $k$-vectors lying parallel to $k$-planes form an orthogonal basis of the space of $k$-vectors. This shows the claim.

Showing that they're an orthogonal basis is just Hodge star-type combinatorics/acrobatics.

DanielSank

18:12

@BernardMeurer What's nimm?

Love, care, and fatherly figure, yes.

Pillow, sure.

Danu

@ACuriousMind Hmmkay

Bernard Meurer

@DanielSank Nimm is a game where you set three stacks of something (usually matches). Each player can remove any number of matches from any of the stacks; whoever takes the last one wins. E.g. We define our state as being $(a,b,c)$ for our stack sizes and say that our currect game starts as $(3,4,7)$. Player A takes 3 matches from a leaving $(0,4,7)$, player B now removes 3 matches from b making $(0,1,7)$ and so on

ACuriousMind

*whoever

Bernard Meurer

Thanks ACM

It's the first game we managed to make an AI consistently beat humans at

DanielSank

@BernardMeurer I see.

This is similar to the game where you count to 13.

Each player in turn can advance the count by 1, 2, or 3.

Whoever hits 13 loses.

Go ahead, try it.

Bernard Meurer

18:17

There are many games like it, but I carry matches around so Nimm is practical

3

DanielSank

4

Bernard Meurer

7

DanielSank

8

Bernard Meurer

9

DanielSank

12

:)

Bernard Meurer

18:18

dang it

I was thinking as if 13 was a victory

DanielSank

Oh, oops.

Bernard Meurer

when you said 12 I was like "Ha, loser!"

and then I thought "Oh, wait"

ACuriousMind

I remember that someone (Conway?) used Nim to introduce some weird number system that extends the reals, where you assign a number to each Nim game state by...some rule. Damn, it's been too long.

yuggib

surreal numbers

but you need just two parts

Bernard Meurer

It's a pretty cool game, I always play it at the bar with granps

yuggib

18:21

anyways surreal numbers are not weird, are similar to nonstandard analysis

Bernard Meurer

Well, I'm off to do my mandatory army enlisting

because freedom

yuggib

in the sense that you can define infinites and infinitesimals

Bernard Meurer

or lack of thereof

yuggib

and manipulate them algebraically

ACuriousMind

@yuggib It was just a vague memory from some workshop I had before I even started studying!

Bernard Meurer

18:22

See yall, and wish they don't pick my limping ass

yuggib

you live in a third world country

Obliv

@ACuriousMind do you have a moment

ACuriousMind

I'm...actually just about to go shopping so I don't starve tomorrow

Obliv

lol ok np i'll ask someone else

ACuriousMind

@Danu Remember that shops are closed tomorrow!

Bernard Meurer

18:24

@yuggib Recently I've been categorizing brazil as a Complex world country

yuggib

(no offence meant, but a country with mandatory military service is...outdated)

Bernard Meurer

@yuggib I don't get offended by something that is just a fact :)

ACuriousMind

@yuggib Germany had that until...like five years ago. Although you could do community service instead.

Obliv

What causes an increase in temperature of an object, specifically? Does anyone know? I know it is regarded as the average kinetic energy of the particles within an object (if this is correct that is)

yuggib

@ACuriousMind italy had it until twelve years ago

still it's something outdated

Danu

18:30

@ACuriousMind I'm going on holidays tomorrow :3

Also, thanks.

@yuggib Like Greece?

bolbteppa

18:54

@Danu pretty nice proof, source?

@ACuriousMind 2nd day in a row you're picking needless fights over things tbh

ACuriousMind

@Danu Nice; where to?

Danu

@bolbteppa Nelson - A Proof of Liouville's theorem (available online)

@bolbteppa Finally someone who likes it :D

@ACuriousMind Back home

ACuriousMind

19:11

"The superconformal hypermultiplets in this paper have a conic hyperkahler target manifold"...reading this sentence evokes a "What am I doing with my life?" moment :P

Danu

It doesn't seem that bad, honestly.

bolbteppa

@Danu I think one could get real intuition for this formulation of the theorem with pictures if they used some ideas from Tristan's visual complex analysis book

Danu

@ACuriousMind ...unless you mean just the actual words

I just don't know what a hyperkahler structure is supposed to be

ACuriousMind

@Danu I mean the actual words... super-this, hyper-that, just...can't they be a bit more creative? :P

Danu

Fair enough

I'm just happy we haven't arrived at "ultra" yet ;)

ACuriousMind

19:13

Well...there are ultra-filters, but I haven't seen physicists use them

Danu

Yeah, I was about to point out that set theorists beat us to it

Bernard Meurer

19:38

I'm back!

dmckee

20:05

I somehow missed

A Google search for hull drag would be a good place to start doing some research for yourself. Ignore the links related to drag queens in Hull - they are unrelated to ships. — John Rennie Sep 21 '14 at 11:06

when it first appeared.

yuggib

@Danu yep...I have a colleague that is trying to convince its embassy that he's working here to avoid being arrested when he gets back to greece in two weeks... o.O

Danu

:\ I have a very close friend in a similar situation.

@dmckee There is actually a result! :D

user54412

@dmckee so apparently clicking a google.co.uk link brings up a privacy notice for me

dmckee

@Danu Well, I assumed there would be. I didn't seen John R amking it up just for kicks. But referring to it for kicks is quite another thing.

Bernard Meurer

@ChrisWhite Same here

UK people are sketchy

user54412

20:17

yeah, they pronounce privacy all weird :p

ACuriousMind

Works fine here

What kind of "privacy warning" do you get?

user54412

ACuriousMind

Oh...that also appears on google.de for me. Probably something to do with EU laws

Bernard Meurer

You first world countries and your pesky laws!

Bernard Meurer

20:53

@ACuriousMind Are you around?

ACuriousMind

I'm here

Bernard Meurer

Can you help me build this IKEA chair

Argh wrong image

ACuriousMind

lol

Bernard Meurer

I don't get this step

ACuriousMind

Well...it appears you have to put the thing into the other thing

Bernard Meurer

20:55

I'm so confused

Danu

:resists temptation:

Bernard Meurer

@Danu Temptation to?

Danu

That's what she said - Michael Scott

►

Bernard Meurer

Ah, hahahahaha

Love The Office

good one

Obliv

21:45

hey does anyone know if early 20th century physicists as well as 19th century physicists used calculators?

like mechanical ones obviously not the electronic ones we use today

ACuriousMind

@Obliv I believe you didn't get far without knowing how to use a slide rule

Bernard Meurer

@Obliv I have no official reference to this, so take it with a grain of salt, but no, not a mechanical one like those people in accounting used; they did have slide rules however which is sort of a calculator I guess

Dammit ACM beat me to the punch

But can we really say the slide rule is a calculator? Isn't it really just a reference?

I like you @Obliv, you're the only one who asks questions I can answer :p

Obliv

God it's weird thinking people performed calculations to such great degrees of precision without the aid of electronics. I'm guessing approximating roots of quintic functions and other things that require approximations were difficult then, huh?

Bernard Meurer

Like the difference between mod and rem operators

@Obliv Back then science was hardcore

ACuriousMind

@BernardMeurer What do you mean? You give it an input, and it gives you an output, which is the result of performing a calculation on the input. That you have to give the input in "mechanical" form by sliding a thing seems rather immaterial to me

@Obliv What are "such great degrees of precision", and name one instance where getting the roots of a quintic function that you can't exactly compute is actually relevant

Obliv

21:51

@bernard lol I am a student, afterall. I actually am forced to take an intro to CS course so I'm going to have to go through all the basics again qq

Bernard Meurer

@ACuriousMind I never used a slide rule (or saw one), but my point was based on the fact that, if all the information is already present on the rule you're not doing much more than referencing

but then again, I don't know :p

@Obliv I'm not even a student yet ;-;

Obliv

degrees of precision that are acceptable in physics and are arbitrarily close to the actual values. Hey man it might be irrelevant to theoreticians but perhaps certain approximations are required to be precise when building objects. @acuri

ACuriousMind

@BernardMeurer Define "all the information is already present on the rule". It's a perfectly fine "analog computer" (Wiki gives like five references for that for people like you who don't believe that ;) )

Emilio Pisanty

Grand

5

Q: Am I just some energy traveled at light speed?

I don't quite understand $E=mc^2$ very well, and here is my question: does this equation mean masses are just condensed energy? And does this mean that the extra energy an object has when traveling at light speed simply becomes mass? So then are all the masses just energy traveled at light s...

↑ This in the hot network questions bar?

Bernard Meurer

@ACuriousMind youtube.com/watch?v=IdtKbq3Omkw :p

Danu

21:57

@EmilioPisanty Oh god

Yes it is (obviously)

ACuriousMind

@Obliv That's not an answer ;P Sure, precision is required, but integral/log tables and stuff like that can give you the required precision just fine - some poor sod just had to sit down one time and compute these values for days ;)

Emilio Pisanty

@Danu I'm not usually one to tell people how to vote. But if it can teach the HNQer some manners here...

ACuriousMind

My "answers" to that question: 1. What? 2. What? 3. What? 4. What?

I get nothing from that question except "Please explain $E=mc^2$ to me"

@BernardMeurer Uh, what?

Danu

It's also at 7 downvotes already

Obliv

LOL I hate when acm responds like that to my questions but it teaches me to formulate real questions and not just word salad/philosophical questions.

not that there is anything wrong with philosophy by itself. It just has no place on a physics website

ACuriousMind

22:05

@Danu Sadly, the HNQ formula weighs answers much more heavily than questions

Emilio Pisanty

@Danu good. It was at +10-3 = 7 when I saw it, I think.

Danu

@ACuriousMind Damn :\

DanielSank

We're partially to blame for answering these questions.

2

This happens a lot.

Sure, a worthwhile writeup can come underneath a terrible question (there's even a badge for this, I think), but that doesn't mean we should do it.

Danu

@JohnRennie, the gauntlet has been thrown down ;)

DanielSank

@Danu I didn't mean it like that.

Danu

22:20

I guess John just feels bad for all those people, trying to learn.

@DanielSank I know that

DanielSank

I know.

I do too.

Danu

OK

NO MISUNDERSTANDINGS

ACuriousMind

::picks up gauntlet, dusts it off, puts it back on::

Danu

@DanielSank The gauntlet has been stolen

DanielSank

@Danu Nah, it's cool. I trust @ACuriousMind.

He can hang onto it for a while.

I want people to learn too.

I don't mind naive questions, but I do mind bad questions, especially if they contain an enumerated list.

I think enumerated lists of sub-questions should be 90% of a close vote.

ACuriousMind

22:22

@DanielSank I am honored

@DanielSank Yes, I fully support your numerous meta posts on that issue

DanielSank

@ACuriousMind I don't think I've ever made a meta post on that.

Have I?

ACuriousMind

11

Q: Is there a way to make it more obvious that each post should contain *one* question?

Background We get a lot of posts asking several related but independent questions [1]. Often the posts are even formatted as enumerated lists, making it clear that the author knows that he/she is asking more than one question. I believe that the quality of the question/answer system increases if...

discussion

2

Q: Should we explicitly tell people that enumerated lists of questions are usually a bad idea?

I find that most (all) posts that include an enumerated list of sub-questions are bad. Outwardly, this is because they're too broad: a good answer would have to go through too much material. Often, the OP has encountered several manifestations of some underlying lack of knowledge and hasn't taken...

discussion

Danu

@DanielSank Lol

DanielSank

>.>

<.<

ACuriousMind

@Qmechanic well, you gotta credit me with consistency :-) — DanielSank Apr 18 at 20:51

DanielSank

22:30

LOLOLOL

ACuriousMind

At least you are consistently being consistent with yourself ;)

DanielSank

I stand by that.

CONSISTENCYCEPTION

John Duffield

@EmilioPisanty : this is a good question. Sadly the answers aren't.

Danu

→ 4 messages moved to Trash

DanielSank

@Danu Good call, thank you.

Danu

22:41

@DanielSank Please don't respond in the future, especially not if you're not happy about what is being said ;)

@DanielSank By the way, about those list-type questions.

Though it may not be possible to edit the relevant "help pages", I'm fairly sure most people active on meta agree with the idea that lists are generally bad. Maybe we can make an faq-type post on meta to settle this and provide a link to it whenever we close a question because it's of this type.

(that tag should of course not redirect to the PSE main site, but you get the idea, I presume)

DanielSank

@Danu I thought suggesting the tone were unuseful was ok, and then my second message was itself not useful.

@Danu Yeah, sure.

Danu

@DanielSank I'm not sure there was any real prospect of it improving anything :P

DanielSank

Well no, but if someone is setting themself up for a chat ban I think they deserve some warning.

Danu

→ 1 message moved to Trash

John Duffield

Well hello there @ArtofCode.

ArtOfCode

22:55

Good evening.

I do hope I'm not in for another evening of trouble.

John Duffield

@ArtOfCode : when did you last have an evening of trouble? It's been very quiet here recently. But since you're here now, you might want to have a little look up the chat and see if there's anything of interest.

HDE 226868

So, has anyone heard about the body TRAPPIST-1, and does anybody know what it actually is? I've heard it referred to as an "ultracool dwarf star" in the original paper, but it seems to have a radius more like a brown dwarf, and a mass ~80 Jupiter masses.

Danu

Errr... possssssibly @ChrisWhite? ^

dmckee

@HDE226868 Isn't the nominal boundary between heavy planet and dwarf star around 70 Jupiters?

In any case, a thing like that is going to be small, dense and only warm rather than properly hot.

HDE 226868

@dmckee I've heard the limit between brown dwarfs and dwarfs stretched to 80+, but it's a fuzzy limit.

ACuriousMind

23:02

Perhaps also a question for @KyleOman

dmckee

Sorry folks. Gotta go. But I guess my figure is out of date.

ACuriousMind

We can't ask KyleKanos anymore, though :/

Danu

WE CAN STILL ASK!

John Duffield

@HDE226868 : I saw the reports, but I don't have a strong view. But note that Sun is circa 332946 times the mass of the Earth, and Jupiter is circa 317 times the mass of the Earth. So the Sun is circa 1000 times the mass of Jupiter.

And so to bed.

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