2:00 AM
@heather Something for you to think about then

@0celo7 Regardless of whether I can obtain that particular information, passing on personally identifiable information to non-moderators would violate the moderator agreement and would be grounds for losing the diamond.

Let $X$ be a set. A ring $R$ is a class of subsets of $X$ such that (i) if $A,B\in R$, then $A\cup B\in R$, and (ii) if $A,B\in R$, then $A-B\in R$.
Prove that $R$ is closed under $\cap$ and $\Delta$.
$\Delta$ denotes symmetric difference: $A\Delta B=(A-B)\cup (B-A)$.
@ACuriousMind I figured.

Note: that's a ring of sets and not the kind of ring that algebraists think about.
So one needs to be careful Googling stuff about that

The next exercise is to show that a ring of sets is a ring in the algebraic sense too.
@ACuriousMind Is it bad that when I hear "ring" and "algebra" I think of measures?

It shows you're not an algebraist, but that's been evident for a long time :P

2:04 AM
Hey, I have two algebra books!
@ACuriousMind Does algebraic topology count?

Only if you actually have to do commutative algebra when you're doing it. If you don't say "Noetherian ring" at leats once a day, you're not an algebraist ;) [the preceding sentence may contain narrow characterization and hyperbole]

@obe Want to see a magic trick?

@ACuriousMind I don't know what a Noetherian ring is.

Yeah, you're not an algebraist, "Noetherian" is the algebraic version of "sufficiently nice" in many cases

@0celo7, okay, i'll give it a shot.

2:10 AM
@ACuriousMind I never claimed to be crazy algebraically minded.

what does it mean to be "closed" under something? i've heard of that term referring to for example I being closed under +, -, * but not /
I isn't right, but i mean that to be all integers
$\mathbb{N}$
or whatever it is.

If $o$ is a binary operation on a set $X$, and if $A,B\in X$, then $AoB\in X$

basically, applying an operation to numbers within your set shouldn't take you out of the set?

@ACuriousMind I've not had a reason to learn algebra. The things I care about tend to not involve algebra.

@0celo7 If you quote me or link me to that note, I can probably clarify what I meant, but that doesn't seem like the kind of thing I would write.

2:14 AM
@SirCumference yes

@obe OK, pick a card.
Any number 1-52, any type

what?

@obe Just pick a card

like a playing card?

yeah
any suit

2:16 AM
ace of diamonds?

You're not supposed to tell me XD
crud, should've clarified that
OK, retry

ok

@obe Pick a card
Ok good. Is your number a prime or composite number?

how do I tell what number my card is?
idk anything about playing cards.

@DavidZ Was I ever suspended for a week?

2:18 AM
@obe Uh, it's just a card with a number between 1 and 52, and a suit of spade/diamonds/hearts/clubs

@0celo7 I dunno, maybe. We don't discuss suspensions in public, remember.

I am giving you permission
I, Revolver J. 0celo7, do give permission
4

lmao

We don't discuss suspensions in public. Permission has nothing to do with it.

@0celo7 xD

2:19 AM
What? I was definitely told that you can give permission

@0celo7 You can give permission, sure, but that doesn't oblige the moderators to do it.
I don't remember people's suspension histories off the top of my head anyway. If I wanted to find out I'd have to hunt through some records.
We may have derailed @heather's study of logic, anyway... my bad

no, not a problem @DavidZ, @0celo7 has a question as well.
i thought you could answer the question if they gave permission.

@heather We won't, so it's sort of irrelevant if we can.
which kind of alludes to "if P then Q" actually :-P

if P is false and Q is true then if P then Q is true but it's irrelevant because P is false.
anyway.

Yeah. Something like that :-P

2:24 AM
Just accept it and move on
@DavidZ I read all of your messages, and didn't find it. But I know I saw it somewhere.
Maybe on the official stack exchange policy
I know there's the mother meta thread on chat policy

Is this about account deletion now? I suppose it could show up in the official network-wide policy, but just to cover their bases

Ok, @heather, want to see a magic trick?

@SirCumference, sure.

@DavidZ yes
but it's not important

OK, then, pick a card, any card:
🂠 🂠 🂠 🂠
Numbered 1-52, any suit

2:27 AM
the far left one'
oh, nvm then.
um, okay, picked.

Is your number prime or composite?

composite

OK, then square it

squared

Is your suit black or red?

2:28 AM
um..

Club and spade are black, heart and diamond are red

black

Ok, then divide your new number by 27
Is your number now within 1-12?

I get a remainder
no, it isn't

rekt

2:29 AM
is your number the 9 of hearts?

no

HA
@heather noice

do i tell you what it is?

sure, i guess...

2:30 AM
or do you want to guess again?
25 of spades
okay

25?

@0celo7 oh fduck

yeah, he said between one and fifty-two.

I told her that the numbers are between 1-52
I meant that there are 52 cards...

...

2:31 AM
um.
sorry?

I'm an idiot...

you want to do it again where i pick a number in range?
what's the real range, by the way?

this doesn't look like set theory to me @heather

I guess we can do it again. Pick a card, any card:
🂠 🂠 🂠 🂠

i have no clue what the range is, but okay.

2:32 AM
Numbered 1-10, or a king, queen, jack or ace

oh, okay.

and any suit

yep.

Is your number prime or composite? (count jack as 11, queen as 12, king as 13 and ace as 14)

composite

2:33 AM
okay, then square it

okay

is your suit's color red or black?

red

then divide by 9

okay

2:33 AM
is your number between 1-12?

yes

is your number the 3 of diamonds?

no.

goddammit!
what was it?

@SirCumference may I point out your last answer didn't make sense - you said hearts when I said earlier my suit was black.

2:35 AM
@heather I made it.

@SirCumference 9 of hearts

proof?

@heather Wait, no, I'm an idiot...
I did that one wrong entirely...
@heather Sigh...

@obe which one?

disclaimer: this is not my design but just a remake of heather's in photoshop and also in blue.

2:36 AM
whoa.

That's the same thing but blue...

it's very blue.

And vectory

How is that a better idea?

2:36 AM
@SirCumference did you not read what I said?

and the rocket base looks weird because you added in the spot that was supposed to be lines.

@heather oh it seems like I forgot the shadows.

why is it so damn blue

xD

@obe Oh, missed that

2:36 AM
it's very blue.

what is QGA site?

@0celo7 Everything he works on, he makes blue

huh, yeah.

He made me a realistic gravatar

not sure what QGA is.

2:37 AM

lol

@SirCumference your pie needs to be warmed up - it looks like it went through a freezer =P

the & just looks weird in that font
i'd have to make my own & to fit in
@SirCumference and yes^ i made that but it's not finished

@obe Can ya send the logo now?

p.s. I basically made the pie myself using pieces of a smaller pie.
the original looks nothing like that.

2:40 AM
Hey, I have a somewhat stupid physics question and I dunno if it warrants a topic; it involves Planck's equation

@Enfyve Sure, what is it?

@heather and @0celo7, he also made an astronomy background

@Enfyve, go ahead and ask.

ooh, that looks quite nice.

2:41 AM
@SirCumference that requires me to upload it to dropbox. too lazy but ok soon
wow

@obe plz

the astronomy logo is cool.

it's unfinished man
stop posting my unfinished work it looks like shit

got to go, good night all.

2:42 AM
it's already on here tho...

bye!
well nobody saw it before

'night

lol

Ok, well the equation states that E = hc/y where y is the wavelength, but if y increases via cosmological expansion, E decreases - does this disprove conservation of energy?

@SirCumference why is it so blue?

2:43 AM
@0celo7 preaching to the choir on that one

@Enfyve energy is not conserved in general relativity
no one claims it is

@Enfyve That would be fine on the main site if you asked "how do I reconcile this with conservation of energy" instead of "does this disprove conservation of energy"

@Enfyve look up conservation of four-momentum

@DavidZ yeah, I felt the question was a bit obtuse..

conservation of energy doesn't apply in dynamic spacetimes
e.g. an expanding universe

2:46 AM
@0celo7 why don't you ask me?
i made it lol
and the answer is simple, because blue is the best colour that exists.

@obe Wait, that's it!

the entire world should be blue.

I think I know a tagline for my astronomy advertisement
"Blueshift to astronomy SE"

i like it

@SirCumference as someone who didn't take physics, that confuses me - it's hard to understand how a dynamic spacetime leads to dissipation of a photon's energy

2:48 AM
@Enfyve That's a complicated topic
The thing is, the energy doesn't really even "dissipate" - that is, it doesn't go anywhere. It just isn't there anymore.

@Enfyve I'm a little surprised you aren't asking about momentum too, since that's related to a photon's wavelength. In relativity you can think of conservation of energy and conservation of momentum as part of one thing: conservation of four-momentum
Actually, I'm not sure how this can be explained to someone who hasn't taken physics...

@DavidZ does that mean that at some point the photon simply ceases to exist? or that it ceases to 'move'

@Enfyve No, its energy just becomes less

@Enfyve A photon with zero energy would still exist because it still has spin

@Enfyve Here's an intuitive way to think about it: imagine the expansion of space is stretching the photon's wavelength
You can't stretch it far enough that the photon won't have energy, but you can keep stretching it more and more

2:53 AM
Ok, that much makes sense. Physics have always fascinated me, but by some stretch I ended up in computer science instead..

@SirCumference what if you fire a photon into a white hole

@0celo7 it explodes the white hole

Isn't a white hole by definition 'exploding?' (being facetious)

@0celo7 cc @DavidZ The old "A Day in the Penalty Box" says: "(This should probably go without saying, but if the problem behaviors do continue beyond the timed suspension, your account is very likely to be permanently deleted.)"; this is from the days before the escalatory structure of successively longer bans was instituted though, I believe.

@Enfyve Watch some lectures
Or read a high school textbook even

2:56 AM
@ACuriousMind Yes, that's what I was remembering.
@SirCumference He should read HE

@0celo7 HE?

I'm not talking to you until you figure it out.

@ACuriousMind ahh... yeah, maybe they should fix that. In practice, we generally don't delete accounts as the next step after a suspension. It normally takes something above and beyond suspension-worthy behavior to get your account deleted.

@0celo7 helium? high energy? her excellence?

@0celo7 yes it only requires basic calculus and algebra.

2:58 AM
my god
@ACuriousMind do you know what I am referring to
@obe knows

Am I stupid or something?

I cannot give an honest answer.
They would delete my account.

@obe wtf is it

@0celo7 What you're referring to with what?

@ACuriousMind what do the letters HE mean to you
don't say if you do know

2:59 AM
wtf...

@0celo7 I'm still a bit sad you don't use proper declension and say he should read HIM :P

...
I feel like I'm missing an obvious joke
explanation for the dumb?

@SirCumference No, it's not obvious nor a joke, just a long-running abbreviation

then wtf

Of course it is ovious
My advisor says it too
@SirCumference just think about it

3:02 AM
long running abbreviation...

@SirCumference normally acronyms like that refer to books when used in academic context or in this chat.
so yeah it's a book.
another hint is that it's a physics book (debatable) in case that wasn't obvious already.

is it very well known?

mathematical physics

or something obscure?

depends on which circles you travel in

3:06 AM
I guess I should've encountered it...
hmm....

no, because you refuse to learn GR
@ACuriousMind should we tell him

I'm not refusing to learn anything

@SirCumference you're refusing to learn anything except facts. XD

Is this still a topic on a book I ought to read or @SirCumference?

I need a stable understanding a lot of other stuff first
@obe "Facts"?

3:07 AM
alternative facts

da hell?

@SirCumference then go for it

@obe Reading papers doesn't just give you "facts" >_>

@SirCumference You'll figure out which book it is eventually

@obe I'm trying

3:08 AM
It's on my desk right now
I don't even have to move my torso to touch it

How the hell does obe know it?
He said it just requires basic calc and algebra knowledge

Because we talk about such things

@0celo7 Why don't you enlighten us?

@rob Yes, I'm not alone!
:35243970 ...
@ACuriousMind ...
@obe ...

ACM and obe know

3:09 AM
to be fair

Sam does too

HE isn't very well known unless you do very mathy GR

Wow.

3:15 AM
...
Uh

Let's keep the discussion about moderation etc in the other room

@SirCumference The book title rhymes with "crime"
The authors rhyme with "jealous"

@SirCumference do you know what book it is

@0celo7 It's called BS

3:18 AM
@SirCumference no
the title is LSSST

the hell is LSSST

@SirCumference $\mathfrak{The large scale structure of space-time by S.W. Hawking and G.F.R. Ellis.}$

Oh, Hawking and Ellis, of course.

3:24 AM
@0celo7 WTF
How is that known to anyone who's studied basic calc or algebra

more importantly, who abbreviates a book based on the authors and not the title (at first)

@SirCumference The preface says the only prerequisites are basic algebra and calculus.

chat is indeed a lot more alive with 0celo7 back, normally at this particular time period, the chat has low activity (and that's how I end up mostly in the maths chat at that time)

@Enfyve in math and physics we identify books by their authors

3:25 AM
@Enfyve that's standard when referencing.

Hawking & Ellis, Wald, Rudin, Evans, Hörmander, etc.
Spivak, Milnor, Kobayashi-Nomizu
Weinberg, Shankar, Sakurai, Bredon, Hatcher

@DavidZ May I say, "you're trolling me"?

Helgason, Wolf, Guillemin & Pollack

Gee calm down mods

3:27 AM
@Enfyve I can go on

this is actually funny.

@SirCumference I'd recommend against it, and also better to ask that sort of thing in the other room

No need, I guess my way of thinking better fits SO.

WTF is going on?!
When did "troll" become offensive?

do you want to be called a troll?

3:28 AM
@obe If I trolled, then sure, whatever

would you call your boss a troll?

@obe 0celo's my boss?

no...

I wouldn't call my boss my wife, but that's not a slur either

@SirCumference always close at hand
2

3:29 AM
@obe No one here needs that formality

@SirCumference The chat is to be treated like a colloquium at your university.

according to the mods we do.

Don't say anything you wouldn't say to someone in real life in that situation.

@0celo7 But I would call my friends or acquaintances trolls, if they openly admit to trolling me

I admitted no such thing.

3:31 AM
Someone here, get on Physics Meta and ask if troll is offensive

@SirCumference It's global SE policy that "troll" is offensive.

@0celo7 Disregarding your deleted comment earlier
Oct 25 '16 at 2:30, by 0celo7
sorry I'm a troll
Mar 2 '16 at 4:37, by 0celo7
I said I'd troll you
Nov 11 '15 at 4:01, by 0celo7
So no one will tell me how I troll. Great.

How about we return to the perfectly reasonable discussions we were having about formal logic and white holes, before we got distracted by what-have-i-got-in-my-pocket?
2

Those are from last year.
I am a changed man.

3:33 AM
I did hard time, 90 days of brutal torture.

@rob I wish there was a way to down-star
Really, the mods don't care anymore

@SirCumference Best not to say things like that.
So answer my question
What happens if you shoot a photon into a white hole?
(Also, it is possible to completely stop a photon using a rotating black hole.)

You can't shoot a photon into a white hole

Why not?

Just look at the conformal diagram

3:38 AM
Looking

There's no future directed null curve that can enter it

That's because we're looking at Schwarzschild
Is it not possible to have a white hole in the future?

I think the negative mass Schwarzschild can describe a future white hole?

Negative mass Schwarzschild violates positive mass theorem
so it's not asymptotically flat

Oh also apparently it's a naked singularity
So nevermind

3:40 AM
I would make a mom joke but those are probably illegal.

Couldn't a particle inside a black hole 'observe' everything not inside the black hole as a white hole though?

Well there's no singularity outside
Although I guess you could describe it as a white hole horizon sort of thing

the word singularity feels like a misnomer here, if a black hole is a point of infinite spacetime, wouldnt a white hole be an infinite lack of spacetime thus having no 'point'?

"a black hole is a point of infinite spacetime"
That is not correct on any level

I'm not even sure what it's supposed to mean

3:46 AM
something approaching infinity (CS major, not phys)

that's like deepak chopra level

what?
deepak?

Deepak Chopra is some indian mystic fellow
He uses a lot of quantum buzzwords

I understand a black hole to be a body where the gravitational field reaches infinity towards it's 'center.' I thought since gravitational fields can warp spacetime that'd mean spacetime would also approach infinity towards the 'center'

3:50 AM
"you are an infinite being that has taken on the identity of a physicist in space and time" -deepak
who knew you could live off random bs and have a net worth of \$80m
strange world