The h Bar

ACuriousMind

00:00

Gnnnnnnnnnh, why do some users have so much trouble understanding what the proper attribution for quoted or copied material is?

2

Bernard Meurer

@ACuriousMind Because they never produced anything

ACuriousMind

You mean...they don't understand why what they're doing is wrong because they have no concept of the difference between copying and coming up with the content by themselves?

0celo7

@ACuriousMind This might be a stupid question, but if there is some smooth timelike curve connecting two points why can't there also be a spacelike curve connecting them?

Bernard Meurer

@ACuriousMind I mean they don't see it as such a big issue because they're not familiar with the hard work of coming it up by themselves

ACuriousMind

@0celo7 Formally? No clue, I don't speak your kind of GR.

0celo7

00:11

@ACuriousMind Uh, what?

How about in SR?

Why can't a point inside of the light cone be reached by a spacelike curve?

The opposite is not true -- a point with spacelike separation to another can be connected by a timelike curve.

ACuriousMind

...what?

I seem to parse at least one of the statements wrong

0celo7

@ACuriousMind Let me rephrase :)

Take Minkowski space with...

wait

Take Minkowski space on a cylinder, time cyclical.

ACuriousMind

Because "If there's a timelike curve between two points, there's no spacelike one" seems to contradict "There can be timelike curve between them if there are spacelike ones".

0celo7

@ACuriousMind Yes

If you take some surface in this space

Then you have an "almost ctc" that goes around and nails a point close to the original one

so that point $q\in I^+(p)$ (the first point)

but if you take the surface as a constant spatial slice, then there is a spacelike curve connecting the two

@ACuriousMind Ok, you're right, that's wrong.

ACuriousMind

Yes

0celo7

00:21

@Slereah You said something wrong in our Skype chat yesterday

and now I have even less of a clue why we need to define $\ll$, etc. only with smooth curves

@ACuriousMind thanks for pointing out that derp...but in causal spacetimes it's probably true

it's certainly true in standard $\mathbb{R}^{3,1}$

@ACuriousMind Do you see an obvious proof for Minkowski?

DanielSank

@ACuriousMind Yes. However, I tried that with scipy.stats.kstest and the resulting p-value was literally random upon repeated trials.

0celo7

@ACuriousMind Do you interpret "a curve never intersects $U$ in a disconnected set" as $\lambda\cap U$ has one component?

DanielSank

Furthermore, the "KS-statistic" is a dumb measure of fitness.

ACuriousMind

@DanielSank Maybe your sample isn't large enough?

DanielSank

A million samples?

0celo7

00:31

not as good as 10 million

get to measuring

ACuriousMind

Hm...I have honestly no idea how large the sample has to be for that test to reliably work

@0celo7 Uh, probably?

But I'd guess that the resulting p-value fluctuating widly probably indicates your data is not being generated according to the distribution you're testing against

DanielSank

@ACuriousMind If I visually compare the function I calculated against a histogram of the numerical samples, they match exactly.

I need to write a software test though.

ACuriousMind

@DanielSank Oh

@DanielSank This says you should perhaps try the Anderson-Darling test

Perhaps you should ask at Cross Validated which test is appropriate for your specific situation?

DanielSank

@ACuriousMind That would be like asking "how do I solve a physics" on this site.

I am inclined to ask there why the p value is fluctuating.

I'm trying to understand the idea behind this.

Consider each bin in the histogram of sampled values, one at a time.

0celo7

00:47

0

Q: When does causal separation imply no spacelike separation?

(See here for notation) In Minkowski space, if $p\prec q$, then there is no spacelike curve $c:[0,1]\to \mathbb{R}^{n-1,1}$ with $c(0)=p$ and $c(1)=q$. This is obvious from a spacetime diagram. (Here a "spacelike curve" is a $C^1$ mapping from a nondegenerate inverval into a Lorentzian manifold w...

Maybe PSE will know better than ACM

DanielSank

The number of counts in that bin should be Poisson distributed with mean equal to the value predicted by my calculated expression.

0celo7

Is it legitimate to ask an answerer "proof?"

ACuriousMind

Do you have some sort of allergy against using a fully formed and polite sentence for that? :P

0celo7

@ACuriousMind I was reading BEE earlier and literally said "proof?" out loud

that and "huh"

it's a disease

ACuriousMind

@DanielSank Is that sufficient to conclude the distribution is the correct one? My statistical knowledge is quite weak.

0celo7

00:52

@ACuriousMind Could you please provide a proof?

ACuriousMind

@0celo7 For what?

0celo7

@ACuriousMind I'm showing you I have no allergy

DanielSank

@ACuriousMind Yes. in this case.

I have a ton of data, etc, etc.

0celo7

@ACuriousMind I would not be a bit surprised if the necessary and sufficient condition is global hyperbolicity.

that's really the condition for spacetimes to be "nice"

I think that's sufficient.

If we have closed timelike geodesics, then we can do stuff with Jacobi fields

But that seems really complicated

Sir Cumference

I think I accidentally found a bug in SE

0celo7

01:01

reported

Sir Cumference

I made an account on one website, upvoted a comment, deleted the account, and the upvote stayed

So I curiously made a profile again, upvoted it, deleted the account, and the upvoted stayed

So I guess you can get infinite upvotes on comments

dmckee

@SirCumference How long have you waited since deleting the accounts?

Sir Cumference

A minute?

0celo7

Caching.

dmckee

There is a lot that is chached on SE, and that stuff can take a while to notice deletions.

Sir Cumference

01:03

Nope, reloaded my cache

0

Q: How to impress my lover who is in the verge of breaking up with me

How to impress my lover who is in the verge of breaking up with me please,any way to revieve my dying love,please help me out,I won live without her

personal-care lifespan

Does one of the comments here have 5 upvotes?

It had 1 before

0celo7

hmm

Sir Cumference

Dang...

0celo7

I'l favorite that for future reference.

dmckee

@SirCumference Not your cache. The one on the server farm.

Sir Cumference

Oh

dmckee

01:04

And possible the ones on the machines your ISP matains for that purpose.

Sir Cumference

I guess we'll find out

Also a potential bug

You create an account, set a bounty on a question, and it gets popular. Award the bounty, delete your account, then recreate the account

0celo7

@James OP need not be a man. — 0celo7 12 secs ago

Sir Cumference

You'll now have 101 more rep and can repeat the process

0celo7

Welp, going SJW

Sir Cumference

@0celo7 Check back on your comment

Jesus this is broken

I think

If it isn't the cache

0celo7

01:12

How do I have that many votes already

Sir Cumference

Cough

I just told you I found a bug

I can also set infinite bounties on a question

0celo7

oh, I wasn't paying attention to you

Sir Cumference

I just realized

0celo7

what did you say

Sir Cumference

By deleting my account and remaking it

Sigh...

0celo7

01:14

I'm doing GR

Sir Cumference

If you make an account, upvote a comment, delete the account, the upvote will stay

0celo7

did you delete your account a dozen times just now

Sir Cumference

So just keep making accounts, upvoting and deleting

Yep

Testing it out on ya

Not like I'm actually gonna use that trick, but it's cool

Dang, your comment was deleted

So nevermind

0celo7

wtf??

Sir Cumference

Yeah, mods ruin fun

0celo7

01:42

@SirCumference how much GR do you know

Sir Cumference

Less than I know QM

0celo7

Should I take you on as my GR padawan

Sir Cumference

Is that a star wars thing?

0celo7

....

have you not watched Star Wars

Sir Cumference

I don't watch sci fi

I love real astronomy

not fake astronomy

By the way

love this

0celo7

01:46

I don't get it

Sir Cumference

...

dude, stop

0celo7

what

Sir Cumference

you know what you're doing

0celo7

that's simply not true

Sir Cumference

there we go

all right, explain

0celo7

01:47

if it's rotating or charged you can go through the ring singularity

Sir Cumference

ain't the event horizon defined as the point where no information escapes?

0celo7

and there's another universe on the other side of the black hole

Sir Cumference

another what?

0celo7

@SirCumference yeah, back into the first universe

Sir Cumference

Isn't the Universe, you know, everything?

0celo7

01:48

well, yeah

but there are parts

Sir Cumference

all of spacetime

what "parts"?

I don't like multiverse theory

It falls into that realm of sci-fi

0celo7

Sir Cumference

What is this?

0celo7

GR

Sir Cumference

Yeah, okay, and?

it's multiverse hypothesis

0celo7

01:50

lel

you're so cute when you say wrong things

Sir Cumference

"Lel" means penis in Dutch ಠ_ಠ

Wait, shit

that's lul

All right, continue

0celo7

continue?

Sir Cumference

That's like if I asked you intricate questions about things you haven't studied

like astronomy

0celo7

but I'm not interested in astronomy

you claim to be interested in this

Sir Cumference

Fuck it

Stop messing with my head

0celo7

01:53

?

all I'm saying is that you can get out of the black hole

Sir Cumference

How?

Its escape velocity > speed of light

0celo7

by going all the way through

@SirCumference lol

Sir Cumference

Usually, you know, you'd die

0celo7

maybe!

maybe not

Sir Cumference

Okay, what happens if you don't die?

0celo7

01:54

you go through

Sir Cumference

to where?

0celo7

another universe

Sir Cumference

Why?

Isn't a black hole just an infinitely dense mass of matter?

0celo7

hehe

Sir Cumference

...

I want to know how much you're laughing

0celo7

01:56

Do you want to be redpilled on what a black hole is

Sir Cumference

Okay, what's a lack hole?

Fine, enlighten me

0celo7

fuck. lost a pencil, brb

Sir Cumference

what..?

0celo7

it's a $50 pencil

Sir Cumference

Why do you have a $50 pencil?

I'm going to guess you're delving into white holes?

0celo7

01:58

I like nice things.

Sir Cumference

So...?

Are you looking for the pencil or...?

0celo7

just wait a moment, I have 14 books on my bed

Sir Cumference

Why?

0celo7

have to clear some shit off before I can search for it

@SirCumference trying to prove something

Sir Cumference

What?

What's your point?

0celo7

02:03

fuck, dropped my analysis homework under my bed

ok, what was I talking about?

Sir Cumference

Goddammit man

I'm about to lose it

0celo7

huh?

Sir Cumference

I was waiting for your explanation so I'd be able to go to sleep

Jesus christ man, why you waste my time?

0celo7

explanation of what?

Sir Cumference

What is your point about black holes?

0celo7

02:05

sorry

Sir Cumference

Multiverses?

GR

0celo7

Ok, so you solve the Einstein equations for a rotating mass, right

you get the Kerr solution

Sir Cumference

Yes, sure

Okay good

0celo7

but it turns out that you can do some crazy shit (cf. Hawking and Ellis (1973) for details) and you can glue a second Kerr spacetime to the first one

and you can glue a third one to that

Sir Cumference

All right

0celo7

02:06

etc.

it follows that you can glue the first one to a zeroth one

Sir Cumference

"glue"?

0celo7

and so you get an infinite chain of Kerr spacetimes connected at the singularity

Sir Cumference

And?

0celo7

so you can go through the black hole and be in another universe!

no crazy tidal forces, you're free

until you hit the next one

Sir Cumference

I feel like you're pulling my leg

You've done this before

0celo7

02:07

have I ever lied about GR

Sir Cumference

Yes

Yes you have...

0celo7

fucking when

Sir Cumference

When you told me how to "derive" the Schwarzschild radius formula

0celo7

that wasn't GR

Sir Cumference

Screw that, how would I know when to trust you?

0celo7

02:09

read Hawking and Ellis for yourself

Oh wait, you'd need to know calculus for that.

Sir Cumference

.......

I don't think keyboards can convey anger

You kept me up to tell me "you need to learn calculus"?

0celo7

Kept you up?

It's 10PM EST

Sir Cumference

It's 3:09am

Ain't in New York right now

0celo7

what country are you in

you must be in central Europe

Sir Cumference

Yeah, actually

0celo7

02:10

where

Sir Cumference

No wait, it's 4:10...

Oh my god

0celo7

lol

Sir Cumference

Israel

Oh my god

0celo7

maybe now you'll learn calculus

Sir Cumference

I said that was Europe

I'm that tired

0celo7

02:12

@SirCumference oy vey

Sir Cumference

Ohahaha

0celo7

don't use His name in vain

Sir Cumference

Yeah, I'll just pray here that I'll learn calc by tomorrow

0celo7

go to the wall

Sir Cumference

In what world is that a name of God?

Already been there

You jewish?

0celo7

02:13

stick a piece of paper "teach me calc pls YHWH"

Sir Cumference

Really?????

0celo7

@SirCumference no

Sir Cumference

I feel guilty that I'm laughing

0celo7

I dig the little hats though

Sir Cumference

Yarmulkes...

The least phonetic word ever

0celo7

02:14

@SirCumference God is typically the name of God in English

@SirCumference I know what they're called.

Sir Cumference

I thought you were talking about "Ohahaha"

0celo7

probably in some Polynesian dialect

Sir Cumference

So yes, what I've gained out of here is:
Black holes may (if you're not lying) open new universes
Israel is now in Europe
Yarmulkes are funny hats
I need to learn calculus

Excellent...

I'm going to sleep

'night

0celo7

I never lie about GR.

Sir Cumference

I don't know if that's a lie tho

Why lie about other physics and not GR...?

0celo7

02:17

GR is holy

Sir Cumference

Oh really now?

Any other physics is garbage

0celo7

physics in general is garbage

GR has interesting math though

Sir Cumference

Physics in general explains the universe

or the other universes you talk about

0celo7

no, that's math

physics is looking at shit

Sir Cumference

Physics is math actually taking effect

0celo7

02:19

go to sleep

you're not making any sense.

Sir Cumference

No you

snores

0celo7

Wow this book is literally HE, what a ripoff

Sir Cumference

High explosive?

Somehow I don't think that's what you meant

By the way, I would like to sleep

0celo7

then sleep

Sir Cumference

But I think I got insomnia...so fun...

0celo7

02:21

I'm not stopping you

Sir Cumference

Haven't slept well in days

0celo7

no, you're just not used to the time zone

Sir Cumference

That too, but even back at home

I might've forgotten how to sleep

0celo7

Wow, I am amazed at how much of a copy this is of HE

Sir Cumference

High explosive?

0celo7

02:22

no

Sir Cumference

What then?

Helium?

0celo7

amazon.com/…

Sir Cumference

Oh dude, you willing to do me a favor?

0celo7

what

Sir Cumference

test out a program I made?

0celo7

02:25

huh?

Sir Cumference

In JS

about physics

0celo7

I don't have JS

Sir Cumference

that's javascript

0celo7

I know what fucking JS is

Sir Cumference

the thing you use for making websites

Your browser should run it

0celo7

02:27

nope

Chrome is 32 bit, can't run JS

DanielSank

@0celo7 There are literally zero web browsers in existence that do not run JS.

Sir Cumference

aw man

0celo7

@DanielSank besides Chrome.

Sir Cumference

Well, this chat is running on JS

I think you're fine

0celo7

@SirCumference nope

Sir Cumference

02:28

?

Dude, it runs on jQuery

DanielSank

@0celo7 Uh, what?

Sir Cumference

Which is a plugin for JS

I guess you just don't want to try it?

0celo7

Chrome doesn't run it

Sir Cumference

Dude

You're on the chat

I'm using chrome

DanielSank

@SirCumference Give up.

He's either trolling, drunk, or I don't know what else.

Sir Cumference

02:30

@DanielSank All right...

0celo7

@DanielSank None of the above, I know Chrome doesn't support Java.

Sir Cumference

Java ≠ javascript

One is for making programs, the other is for websites

0celo7

Perhaps.

Physics Meta

04:28

0

Q: Causes of down downvoting questions

Why can't I ask hypothetical questions about situations that cant't happen in the first place, if I'm interested in the resulting phenomena and/or said situation will cause? And can I try to funny,or is that looked down upon here.

discussion soft-question

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