The h Bar

user228700

01:10

@Balarka:

user228700

7 hours ago, by Balarka Sen

i kinda like it

user228700

There's a GIF, too!

0celo7

03:22

jesus christ GR is too hard

god damn signs

Sir Cumference

03:32

Why is Special Relativity Hard? | Special Relativity Chapter 1

►

Huh...

0celo7

fookin ell @Slereah yvonne is a madwoman

she uses two different conventions for extrinsic curvature in the same equation

0celo7

04:21

@Slereah I need to write a note on null geometry

this is too hard

just doing everything from scratch would be easiest

Abcd

05:50

@JohnRennie I logged in from my old deleted account. I have forgotten the email of my actual account, what do I do now?

I am logged in from my actual account through mobile.

But there's no way to see my email :/ :(

The reason is, that I hadn't deleted login history since 3 months on my laptop and today I deleted it :/ , Then after that I couldn't recall my email.

Can any Mod please help?

John Rennie

@Abcd Mods can see the e-mail of your actual account. Though I guess you'll need to prove to them that you're really Abcd not some hacker pretending to be Abcd.

Abcd

@JohnRennie Yes, I can prove that to them by sending screenshots from my real account which is still logged in from my mobile.

screenshot of my profile page* on the SE mobile app.

John Rennie

That should be no problem then. Is there a Contact us link on mobile? Alternatively ping the mods here and ask them to help or post in the Meta.

Abcd

@ACuriousMind @dmckee @DavidZ @Qmechanic Please see.

John Rennie

@Abcd is there no way to see your email from the SE app profile page?

Abcd

05:59

@JohnRennie no :/

John Rennie

Loong isn't a physics mod.

Qmechanic, dmckee or DavidZ are the other mods.

John Rennie

06:13

→ 28 messages moved to SecretLabs (SE Branch)

@Secret Done!

Secret

07:34

15 hours ago, by vzn

~275 refs to susskind in here. just bought his book on QM. via reddit physics ran across this new video espousing universe-as-simulation. any reactions?

If the universe is a simulation, then magic will be possible

2

Else if the universe is not a simulation, then there is no magic since any model can be expanded indefinitely to accomodate new phenomenon

David Z

08:04

@Abcd I suggest contacting the SE team.

Abcd

@DavidZ I will give you the proofs...why make the process long?

David Z

In general, the moderator agreement prohibits us from revealing personal information such as email addresses. I guess it should be fine to reveal an email address to the owner of that email address but we (site mods) don't really have an established procedure for verifying that you do own the address, so I think we would have to be overly cautious. But the people on the SE team will know what to do.

Slereah

@DavidZ Christmas is over!

John Rennie

08:19

@EmilioPisanty there was obviously more demand for an explanation of the symmetric twin paradox than I thought. Not just has it attracted lots of upvotes but also five other answers. Only my list of things to do is extend my answer to discuss four velocity and how it transforms between the three observers' frames.

Secret

in Mathematics, 12 mins ago, by Vrouvrou

Let $u\in L^1_{loc}(\Omega)$ such that $$\int_{\Omega} u(x)\xi(x) dx=0,~\xi\in C_0(\Omega).$$ Then, $$u\equiv0~\text{a.e. in}~ \Omega.$$

Does this famous result even have a name?

I only knew it is used in making a boundary term to vanish in electromagnetism

Slereah

09:17

I like how two of the big papers you get for branching spacetimes are "What branching spacetime might do for physics" and "Why branching spacetime is a bad idea"

Slereah

09:34

Hey @ACuriousMind

Emilio Pisanty

in SecretLabs (SE Branch), 11 hours ago, by Secret

I think we are getting closer to tabletop proton accelerators

@Secret Yes, that is correct.

You won't get to LHC-like energies

i.e. tabletop laser wakefield accelerators are unlikely to be producing Higgs bosons anytime soon

i.e. I don't think those energies are even on a 20-year roadmap (but then again I'm not an expert on the accelerator uses of lasers)

Slereah

We already had tabletop proton accelerators in the 30's

Emilio Pisanty

but there's plenty that you can do

Slereah

Not great energies, but still

Emilio Pisanty

@Slereah yeah, that's the rub

Slereah

09:41

the first accelerator was like 20cm

Emilio Pisanty

from the Nature Comms paper Secret linked to

> The emitted proton bunch is reproducibly observed with central energies between 20 and 40 MeV

that's going to be hard to do on a tabletop using electrostatic acceleration

though a megavolt isn't all that crazy for e.g. a small facility that can be built in-house

> PHELIX laser. The experiment employed the PHELIX laser at GSI Helmholtzzentrum für Schwerionenforschung. PHELIX is a glass laser system based on chirped pulse amplification with a central wavelength of 1054 and 3 nm bandwidth. In the experiments the pulse energy amounted to 150 J with pulse duration of 500 fs. The laser pulse was focused by an 45° offaxis parabolic copper mirror with 400 mm focal length. The beam size amounted to 250 mm. The laser contrast was enhanced by a fast Pockels cell and optical parametric pulse cleaning techniques leading to an amplified spontaneous emission (ASE…

I love how they need to jump to laser contrast pretty much immediately

it's such an unintuitive concept

Also of note:

> The laser is capable to deliver one shot every 90 min.

not quite the way to go for experiments that need lots of data to crunch the statistics.

Slereah

"Some results of branching phenomena within a single spacetime were prompted by research into so-called “trousers worlds”"

an entire world of trousers

Emilio Pisanty

@Slereah lolz

Shing

10:55

I know entropy is extensive when it is weakly interacting. but how weak is weakly interaction?

have this confusion when I was studying blackbody radiation, what first came to my mind is: "it is quite hot, so probably something pretty crazy going on there.", but then it turns out to be weakly interacting

It really blowed my mind, and left me in dire confusion: how weak is weakly interacting? When exactly we can neglect the energy of interaction ? How weak the interaction need to be, so that we can safely claim entropy is extensive? Do we only possibly know it in hindsight? Anyway we can foresee it?

Would anyone be kind enough to shed some light on this matter for me?

Master Yushi

12:24

What happens when a capacitor is earthed ?

0celo7

13:44

@JohnRennie any idea what caused this and basically crashed my computer? i.gyazo.com/58e15a16a9cb9f7d0d1ccf664c557e72.png

John Rennie

@0celo7 You can use the Task Manager to see what apps are using memory. Right click the taskbar and choose Task Manager from the popup menu.

0celo7

@JohnRennie whatever did that stopped using the memory

John Rennie

The memory usage alone shouldn't have crashed Windows though. It peaked around 13GB so you had memory left. I wonder if the memory spike was just a symptom of some other problem.

0celo7

that's my worry

it didn't crash, it basically stopped responding for a few seconds

John Rennie

Unless you can catch the rogue app in the act there's not a lot you can do.

Intense disk activity can cause that ...

But it has to be pretty intense.

0celo7

13:53

@JohnRennie even with an SSD?

John Rennie

Yes

Unless it happens again I wouldn't worry about it. I doubt it's a problem with the hardware of Windows.

Just a rogue app.

I'll have to leave that with you. I have to go off and score lunch now :-)

0celo7

@Slereah I'm going to write up section 2.7 of HE.

And then do a thing on apparent horizons.

The literature is too confusing, I have to work it all out myself from scratch.

Slereah

Which one's 2.7

0celo7

@Slereah hypersurfaces

@Slereah I'm working on stability and regularity of (apparent) horizons for now, so I'm trying to work through the derivation of all of the equations

it's a mess

@Slereah one also has to be careful of physicist proofs in this area...

"IWHULWZDVLPSRUWHGLQWR*KDQDIRUXVHDVDSHVWLFLGHWKHORFDOILVKHUPHQDO‌RQJWKHVKRUHVRI/DNH9ROWDIRXQGLWKDGDQRWKHUXVHDVZHOO:KHQWKH\GXPSHGLW‌LQWRWKHZDWHUPDQ\GHDGILVKIORDWHGWRWKHWRSRIWKHZDWHUDQGWKHILVKHUPHQ‌FRXOGHDVLO\FROOHFWWKHPVHOOWKHPDQGIHHGWKHPWRWKHLUIDPLOLHV"

hmm

tried copying from a pdf

Slereah

14:17

Is that the physicist proof

just take a screenshot

will be simpler

0celo7

@Slereah it's not related to GR

Slereah

14:33

Why do we define the volume form, anyway

Why does it have to be $\sqrt{g} \varepsilon$

Why can't it be some other function

In what sense does it define the volume

I guess it has to just be the Lebesgue integral in the flat limit, but that doesn't make it unique

0celo7

@Slereah because if $e_1,\dotsc, e_n$ form an orthonormal frame, then $\omega(e_1,\dotsc, e_n)=1$.

Slereah

ah yes

Balarka Sen

@Slereah Look up "Gram determinant"

Slereah

Hm, does the notion of space orientability make sense if a spacetime doesn't admit a spacelike foliation?

Balarka Sen

If $\{v_1, \cdots, v_n\}$ spans a parallelopiped in $\Bbb R^m$ then the volume is given by the square root of $\text{det}[v_i \cdot v_j]$

Slereah

14:41

I'm not sure

0celo7

@Slereah what is space orientability

Slereah

Errr... I guess the best way to define it without foliations is that spinors don't have left-right projections

or does that just depend on orientation period

I'm not sure

0celo7

@Slereah there is a serious need for a good mathematical GR book

not Yvonne

Slereah

O'neill?

0celo7

@Slereah no, something with big guns

black hole topology, hypersurface dynamics, jet formulation of ADM

Slereah

14:54

this is the only math book with big guns

web.math.rochester.edu/people/faculty/doug/otherpapers/…

0celo7

existence of maximal surfaces

Slereah

just doing jet formulation of Hamiltonian is hard enough my man

I don't even know why you need foliation for Hamiltonian mechanics

0celo7

my stack of mathematical GR papers that are nowhere in books is ludicrous

Slereah

Since the bundle description never seems to mention it

0celo7

granted some are very recent

Slereah

14:56

I guess it's needed for some uniqueness of development argument

0celo7

@BalarkaSen yo

Suppose I have a linear map $\theta:V\to W$ of vector spaces

Slereah

IIRC if you do ADM without a good foliation the metric fails to be Riemannian

or something

Balarka Sen

go on

0celo7

If one wants to consider the "natural extension" of $\theta$ to the tensor algebras $T(V)$ and $T(W)$, it should be like $\theta:V\otimes V\to W\otimes W, v_1\otimes v_2\to \theta(v_1)\otimes\theta(v_2)$, right?

Balarka Sen

true

0celo7

14:58

and then do the multilinear shit

Balarka Sen

mhm

0celo7

@BalarkaSen ok so consider the following

I have an embedding $\theta:M^n\to V^{n+1}$ of manifolds

For $p\in M$ I let $H_{\theta(p)}V=\{v\in T_{\theta(p)}V:\mathbf g(v,n)=0\}$, so just $d\theta_p(T_pM)$

Balarka Sen

mmk

0celo7

And one can define $H_{\theta(p)}^*V$ in the natural way

the map $\theta^*_p:T_{\theta(p)}V\to T_pM$ will be injective on $H^*_{\theta(p)}V$

so we may consider $\theta_{* p}=(\theta_p^*)^{-1}:T_p^*M\to H_{\theta(p)}^*V\subset T_{\theta(p)}^*V $

fug

@BalarkaSen idk what's wrong

Balarka Sen

$\theta_p^*$ is the dual map of the inclusion $d\theta_p : T_p M \to T_{\theta(p)} V$?

0celo7

15:05

@BalarkaSen it's the pullback

Balarka Sen

injection rather than inclusion but w/e

Sure, same as dual

OK

0celo7

so $\theta_{* p}$ is an isomorphism of $T_p^*M$ and $H^*_{\theta(p)}V$

Balarka Sen

Hm, it is.

0celo7

so it extends to the tensor algebra

in particular, let $g=\theta^*\mathbf g$ be the natural induced metric on $M$

now we can "push $g$ forward" by considering $h=\theta_*g$

this is now a tensor on $V$, but shouldn't be a metric

by following the arrows, we expect that $h\in\Gamma(H^*V\otimes_S H^*V)$, right?

Balarka Sen

$h$ is only defined on a subbundle of $TV$, right?

0celo7

15:08

@BalarkaSen restricted to $\theta(M)$

Balarka Sen

Well, a subbundle on $TV$ along $\iota M \subset V$

Yeah ok

0celo7

I was being a bit lazy there

Balarka Sen

np, i getchu

0celo7

$H^*V$ is only defined along $\theta M$

but $H^*V\subset TV|\theta M$ in a natural way, so $h$ is a tensor on $\theta M$

But, by the definition of $H^*V$, we have that $h(n,-)=0$

because $H^*V$ annihilates the normal bundle

Balarka Sen

@0celo7 I agree with this

@0celo7 Mhm

0celo7

15:11

@BalarkaSen the goal here is of course to find a formula for $h$

the claim is that $h=\mathbf g-n\otimes n$ works

Balarka Sen

$h$ is of course very degenerate because of $h(n, -) = 0$

@0celo7 Hm

0celo7

@BalarkaSen not very degenerate, should only have a dimension 1 kernel

namely the normal bundle

Balarka Sen

Yeah true

0celo7

see, it's the metric on $M$ viewed as "living in $V$"

very convenient for computations

Balarka Sen

mhm

0celo7

15:12

so we have that $(\mathbf g-n\otimes n)(n,X)=0$ for any $X$ tangent to $\theta M$

assuming $\mathbf g(n,n)=1$

Balarka Sen

Is $n$ the dual of the unit normal vector?

0celo7

@BalarkaSen yeah

Balarka Sen

'kizay

0celo7

$n^\flat$ if you like

Balarka Sen

for sure

0celo7

15:14

so what this shows is that $\mathbf g-n\otimes n$ has values in $H^*V\otimes H^*V$ because it annihilates the normal bundle

and I don't know if that is immediately true or needs some work

Balarka Sen

I mean it's a tensor $TV \otimes TV\to \Bbb R$ which vanishes on $n \subset TV$. That descends down, either by restriction or thinking of $HV$ as $TV/n$, to a tensor $HV \otimes HV \to \Bbb R$. (by the universal theorem of quotients if latter)

That's your element of $H^* V \otimes H^* V$

Just elaborating that much should be enough

0celo7

right, I guess you could define a "restriction" in the natural way, and then it agrees with it on everything, so it's equal to the restriction

Balarka Sen

Yep

Slereah

wot

0celo7

Ok, so we have that $\mathbf g-n\otimes n$ lives in the right space

so to show that it equals $h$, we claim that $\theta^*(\mathbf g-n\otimes n)=\theta^*h$

Balarka Sen

15:18

Now $n \otimes n$ vanishes on $HV \otimes HV$

By definition

0celo7

and then the claim follows from the isomorphism property of $\theta^*$

Balarka Sen

yeah

'Cuz $\mathbf{g}|_{HV} = h$

0celo7

@BalarkaSen well that's the problem, I'm having a hard time unpacking the definition of $h$

it's $\theta_*\theta^*\mathbf g$

putting a $\theta^*$ on that is too hard

Balarka Sen

theta_* is just inverse of theta^*

so they cancel

restricted to HV

0celo7

the "restricted to HV" bit is what I need to make precise

Balarka Sen

15:25

Look, $\theta_* : T^*M \to H^* V$ is an isomorphism. $\theta^*$ is inverse of this isomorphism.

$\mathbf{g}|_{HV}$ lives in $H^* V$

Therefore $\theta_* \theta^* \mathbf{g}|_{HV} = \mathbf{g}|_{HV}$

0celo7

do you mean $\mathbf g|_{HV}$

Balarka Sen

Right, sorry.

0celo7

@BalarkaSen ok, so?

Slereah

@0celo7 HE "defines" space-orientability p. 181

0celo7

@Slereah they probably mean that "if" there are spatial slices, they should be orientable

Slereah

15:30

yeah, it's my guess

Emilio Pisanty

@Slereah whoa

that's quite remarkable

0celo7

@EmilioPisanty why?

fucking algebraic topology is so mysterious

I have no idea what level this stuff is

maybe algebraic topology is just the best subject and those who don't do it are crap plebs

Emilio Pisanty

@0celo7 getting the git commit hash into the pdf

though I guess if the pdf isn't in the repo it's not that crazy

Balarka Sen

@0celo7 Let me be more precise and politically correct. $\iota : M \to V$ was the inclusion. $\theta : TM \to TV$ was inclusion of tangent spaces, and it's image is $HV \subset TV$. $\theta^* : T^* V \to T^* M$ was the pullback. $\theta^*|_{H^* V} : H^* V \to T^* M$ is an isomorphism. $\theta_* : T^* M \to H^* V$ is the inverse of this dude. OK?

0celo7

@BalarkaSen sorry I've gotta get showered and to class

Balarka Sen

15:34

Alrighty

It's not hard to see, you just need to write down everything carefully.

0celo7

I was typing this last night and I have some typos which are the source of my confusion

@BalarkaSen exactly

@BalarkaSen I'm trying to be very careful because next I want to put a $\Sigma^{n-1}\hookrightarrow M$

Slereah

16:03

So proof that the inverse metric is same class as the metric

$X, Y$ are smooth, then $g(X,Y)$ is $C^k$ if $g$ is $C^k$, which means that $g^{-1}(X^\flat, Y^\flat)$ is $C^k$

which means that $g^{-1}$ is at least $C^k$

But how to show it's exactly $C^k$

Since $X^\flat$ is $C^k$ itself I can't rly do much better

I doubt that $g^{-1}$ magically becomes smooth when $g$ is $C^k$, but dunno how to proof

Wait, if $g^{-1}$ is $C^{k+n}$, then $g^{-1}(\omega, \theta)$ is $C^{k+n}$, but then it's also equal to $g(\omega^\sharp, \theta^\sharp)$, which should also be $C^{k+n}$ but is only $C^{k}$ best case scenario

So it's $C^k$

QED

0celo7

16:23

@Slereah follows from Cramer’s rule

Slereah

Is that proof working alright, too?

How do you define the differentiability class of tensors, anyway

I used $T(X,...)$ smooth for smooth vector fields but I have no idea if it's correct

Apparently the correct definition

Whew

0celo7

16:40

@Slereah I’ll have to look tonight when I have a computer

It’s not clear from what you wrote that X and X flat have the same regularity.

Slereah

X flat is partial application of g, so if g is Ck, so is X flat

And same argument with ω sharp and the regularity of the inverse metric

ACuriousMind

17:07

@EmilioPisanty 9 seconds. ::blows smoke off gun::

Slereah

What's the general rule for regularity anyway

if I have a $C^k$ vector field and a $C^r$ function

Is $X(f)$ of class $C^{\min(k,r)}$

John Rennie

@ACuriousMind had I the power to unilaterally close homework questions that would be nothing. Note no smiley, because the current deluge of homework questions is not funny.

0celo7

@Slereah yes

Slereah

gud

ACuriousMind

@JohnRennie I think the proportion of HW questions hasn't really gone up, but our total traffic has simply increased

Yeah, in November we had 29,4% close rate with 35,6% of that homework, now we have 34,7% close rate with 37,2% of that homework. Not a very significant increase I'd say

Emilio Pisanty

17:51

@ACuriousMind a pointer to mechanics.stackexchange.com might've come in handy

37

Q: Helping our new users make the transition

mechanics.SE is not a forum It's Q&A. Not Q&Q. Nor Q&Commentary. Nor Q&Chit-Chat. The seasoned SE veterans understand the rules, but the new users don't and we ought to help them make a smooth transition. I'd like to use this Meta post to highlight to the new users what they should understand ...

lolz

> mechanics.SE is not a forum
> It's Q&A. Not Q&Q. Nor Q&Commentary. Nor Q&Chit-Chat.

ACuriousMind

@EmilioPisanty I didn't have in mind that site existed, but you're right :)

Slereah

Sorry I only go to the best stack exchange

Emilio Pisanty

@ACuriousMind it's come up a few times on the SEWAGE list

Slereah

6

Q: How does Islam interpret the creation of the universe and is it compatible with the Big Bang Theory?

My colleagues and I often discuss about creation of universe, our solar system which is, in scientific theories, explained by Big Bang Theory. My questions are: Was this universe, specially our solar system, created according to the Big Bang Theory? Does Quran and Ahadiths support this theory...

creation universe

nothing but great physics threads

Balarka Sen

I am sure we get compatibility-with-science questions in Hinduism SE too

Emilio Pisanty

17:54

@Slereah well, there was this one physics.meta.stackexchange.com/a/9595/8563

Slereah

hint : the answer is always no

Emilio Pisanty

Balarka Sen

lol

beautiful

Slereah

well, are there

Probably

Emilio Pisanty

proposed community ad from last year

Slereah

17:55

I'm sure things fall down in the Veda

Emilio Pisanty

somehow managed to get four upvotes

Slereah

i would upvote it

Emilio Pisanty

don't know if I've ever been more mystified at upvotes on this site before

Balarka Sen

its very psychedelic

ACuriousMind

I love the bearded dude in the background

Balarka Sen

17:56

me too

his expressions are very c o s m i c

Emilio Pisanty

@Slereah good thing is that you can check for yourself.

Slereah

is it hindu jesus

Balarka Sen

its a hindu monk i guess

Slereah

My favorite thing about buddhism by the way

Is that Buddha never saw old age, death, sickness or religion until he was all grown up

Emilio Pisanty

@Slereah ... is how tenuously related it is to hinduism?

Slereah

17:57

And then he goes out in town

Emilio Pisanty

it's like they're two completely different religions =P

Slereah

And he sees ALL OF IT AT ONCE

What a ride!

The illustrations of it are great

Same cultural substrate :p

Balarka Sen

Siddhartha was a jolly old prince

Slereah

Balarka Sen

@Slereah the watermarks add to the aesthetic

Slereah

17:58

If I was the Buddha I'd never leave my house again

look at that midget skeleton

Emilio Pisanty

btw y'all seen this golden bit of twitterism?

OKAY I HAVE AN IMPORTANT THREAD FOR YOU about fighting in ballgowns! I will illustrate with Disney Princess gifs, because why not. First, you can absolutely swordfight in a dress. Some dresses are great to swordfight in, and some are not so great.

Tweeted by melisscaru on January 31, 2018 at 2:33 PM

Balarka Sen

lol

guess thats a new brand of feminism is it

good good

ACuriousMind

But where do you keep the sword while in the gown but not fighting? Do you have to get an aesthetically fitting scabbard for each dress?

Emilio Pisanty

@ACuriousMind would that be such a deal killer

ACuriousMind

Probably not

Emilio Pisanty

18:11

also, good punch

Remember all this, and be ready to rip your seams if you have to, and you'll be able to dance with the villain AND duel him later. https://t.co/iiZvL5JK2n

Tweeted by melisscaru on January 31, 2018 at 3:16 PM in reply to melisscaru

t.co/iiZvL5JK2n

hmmm

as a trained martial artist, I approve of the punching technique

Slereah

What is your martial art

Emilio Pisanty

good solid stance, well-squared arm movement, good all-body involvement, clean pullback

could maybe rotate the hips a bit more for some extra oomph, but hey

you don't want to kill the guy, either

@Slereah wu-shu

Slereah

Sounds delicious

I did Judo when I was a kid

went to a tournament once

I lost every match

But I still got a gold medal

I was so thin I was the only one in my weight category

Anonymous

@Slereah Lol. Were there gold metals for being extra heavy too? Like, if everyone else is thinner than you ? :D

Slereah

Actually there was!

One of the contestant was a fat girl

and she too got a gold medal for that reason

Anonymous

18:19

lmao

Anonymous

That's an awesome competition I must say

Anonymous

It seems easy to win, for me. I'd just eat pizzas 3 times a day, for 6 months.

Slereah

A good trick if you want to win at competitions

Balarka Sen

fighting is too hard

Slereah

Plus judo's boring

Kids don't want to do judo

You can't kick people in judo

Emilio Pisanty

18:22

@Blue the circuit I fought in, the heavyweight category was >70kg

meaning there's very little point trying to outrun it

there'll always be people in it, and they will generally be faster than you

Balarka Sen

@Slereah I don't want to kick people

I don't want to break my leg

Emilio Pisanty

though admittedly that was on blackbelt territory

I wasn't in >18yo <blackbelt for very long so I don't remember what the categories were

Slereah

I only went up to orange belt

I wasn't very good at judo

John Rennie

One of my father's friends was a commando in the second world war. I remember asking him if he was trained to fight kung fu style. He told me that no, you preferably shoot people, failing that stab them and failing that hit them with any large heavy objects conveniently to hand.

Emilio Pisanty

presumably the >18yo heavyweight category on a starter belt isn't quite as scary as the heavyweight blackbelt one

Anonymous

18:25

@EmilioPisanty So you got upto black belt? That's remarkable! I dropped out with a blue XD

ACuriousMind

Hence your name?

Anonymous

I was 13 then I think

John Rennie

That's the difference between Hollywood and real life I guess ...

Emilio Pisanty

@Blue I did two black-belt examinations

Slereah

abstrusegoose.com/143

Emilio Pisanty

18:26

what karate people call "second dan"

Slereah

@JohnRennie Léon Degrelle holds the record for close-combat kills in WWII

He did it by strangling people

little tip from an SS officer

Anonymous

@ACuriousMind Nah, I just had the divine realization that my last belt color matches my code-name ;)

Balarka Sen

savate is where it's at

Slereah

(savate means shoe in french)

Balarka Sen

i can tell

Anonymous

18:30

@EmilioPisanty How many degrees of black belts (dans) were there in your form of martial art? In mine (Shinkyokushin) there were upto 6 degrees iirc

Anonymous

Our instructor had 5. I never met anyone with 6

Anonymous

I guess it takes a lot of perseverance to reach that level

Emilio Pisanty

@Blue there isn't really an overarching regulatory body outside of China that I'm aware of. The founder of my school has five if I recall correctly but it's been a long time. I'm not entirely sure where he did his examinations.

Slereah

Does it mean I can start my own karate school

Anonymous

Ah, I see

Slereah

18:32

And give me 10 black belts

John Rennie

@Slereah I am struggling to find a reliable source to back up that claim ...

Slereah

@JohnRennie From what I heard, 75 kills in close combat

Emilio Pisanty

frankly, the fourth examination still makes some sense to me (roughly indicative of ten years of continuous improvement after the first blackbelt) but after that it gets pretty fuzzy afaic

John Rennie

@Slereah citation?

Emilio Pisanty

@Slereah sure, for all the good that that'll do you

Slereah

18:34

@JohnRennie From what I see, it might be in Ritterkreuzträger mit Nahkampfspange in Gold?

books.google.fr/…

Emilio Pisanty

on another note, this is awesome

Balloons look really weird when they resonate

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Slereah

also here

Anonymous

@BalarkaSen It was my dream as a child to introduce a form of martial art where you're allowed to bite people. I was an expert in biting people who annoyed me, in school. (Also received a lot of nicknames acknowledging that skill of mine) :P

Balarka Sen

gross

Anonymous

It's one of best methods of self-defense. The karate guys will never teach you that

Anonymous

18:40

:'D

John Rennie

18:52

Indiana Jones - Arab Swordsman Scene

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