4:00 PM
I should add : I admire the guy. He has worthy goals.

4:41 PM
@BernardMeurer: I believe it's Linux's 25th birthday (give or take a few days). Are you out celebrating? :-)

@JohnRennie If I recall correctly the first release was October 5th 1991 :)
I will, however, go out celebrating on that day :p

AH
That's the Minix change that got released to a few friends, 0.01
Interesting, so technically it was yesterday
Because October 5th was 0.02 already!
I need to drink!
I'm going to get beer, brb

@BernardMeurer Any excuse :-)

My beer should be cold in 10 minutes ish
This is the chosen one for today

4:49 PM
@vzn : thanks. Isn't it a pity that SpaceX are flogging a dead horse?

@JohnDuffield not sure what you mean.
proudly running linux since ~1994

Is that water?

Pint of vodka!
It is my favourite glass though. It's easy to hold, because of the narrow base, but not a pain to wash like tall narrow glasses.

Phew, that's better, you should watch out for this water stuff, it kills you
My favorite glass was my Flensburger one
but it is now long gone
RIP
2015-2016

5:01 PM
@BernardMeurer Rest In Pieces? :-)

Yep, lol

This one is quite overwhelming though

I just hate having to wash glasses like that. In a bar they have machines to do it. At home you have to try and push the dishcloth down with a cooking spoon or whatever.

@JohnRennie You only have to clean if you stop drinking!

5:06 PM
I have to sleep some time ... :-)

So that's what age will do to you huh :p
This one!

@JohnRennie Lol, That's some mean grandma
I'll buy this with my first salary :p

Too much pattern matching can be bad sometimes

@Secret I suck at poker, are you telling me I'm bound to fail?

5:14 PM
nah, that's just one of the may points I get from that article, which talked about how AI plaing poker might teach us how to play it and life itself better. for exmaple, work out how many possible routes you can lead yourself to victory
and avoid patterns

Hmmm. Winning the lottery
Getting a Flensburger chair
there, victory

we also make wrong decisions very quickly when under pressure
This is why I hate time pressure in work environments
for me, time pressure also strangle most of the weridness and randomness that defines me, and hence make my innovation less efficient

In poker, according to that article, the pattern you play it can indirectly give info about what cards you have on your hand
Another theme is abstraction, where we tend to (sub)consciously try to simply complex information by using patterns and grouping them into categories, thus narrowing our possibel range of options
One artist taught me about the concept of "presence", that each concept has something that is just "it is". Yet we tend to find "patterns", which in art speak is the projection of our ideals and thoughts and interpretation on a concept, thinking it means what we think it is
A nice example to illustrate this is the experimental results of quantum mechanics, that's the presence, while our inumerable interpretations of quanutm mechanics is a pattern

So...anyone good with astronomy here?

5:25 PM
Working hypothesis: let $g$ be any Riemannian metric on $M$. Let $f:M\to\Bbb R$ be a smooth exhaustion function. Then $(\mathrm e^f+1)^2g$ is complete.

@SirCumference well it has to be johnrennie cause 0celo7 do pure GR. ACM is not on atm

@Secret Well okay then

Proving this Rigorously will be trouble

@JohnRennie You're good with astronomy, right?

Because you need terrible curves

5:31 PM
@SirCumference I'm a master of Astronomy, ask away

@BernardMeurer Great

The only problem is I have a really hard time communicating, so I can't ever answer any questions

So I set a bounty on this question

or prove that I know anything

4

Hi I am trying to understand the concept of dex and how to use it in calculations. The usual definition is that it is the order of magnitude, so $10^{0.1}$ is $0.1$ dex. I want to do a simple exercise of calculating the value of the RHS of Eqn 4 in this paper arxiv paper, the gammas are incompl...

5:32 PM

And I'm screwed if I don't get an answer
Sigh...

Sorry mate :p
Dex for me is pokedex

Ffs
The badge I was trying to get requires me to AWARD a bounty
Not start one
So I lose my rep and get no badge if it's not answered

@ChrisWhite Just got his PhD so he's probably still drunk

I really wish I could answer the question somehow, and award myself the bounty

6:05 PM
https://en.wikipedia.org/wiki/System_dynamics
This diagram pretty much summarise what happens when I am making a decision (excluding emotional factors)

Hi, I have a question:

I'm thinking of enrolling in a graduate level course in electrodynamics. The course is taught using Zangwill's Modern Electrodynamics (http://www.cambridge.org/us/academic/subjects/physics/general-and-classical-physics/modern-electrodynamics?format=HB). This first graduate level course couvers electro/magneto-statics, fields in matter and the basics of Maxwell's equations -- pretty much what is covered in the corresponding first course in undegraduate E&M.

I have done E&M (except for fields in matter and a bit of Maxwell's equations) over the summer. Although I have

6:29 PM
Crap! You can have a finite integral of a divergent function
The integral is too insensitive for blowup detection

@0celo7 I think it should be some quite tricky function
@0celo7 I suspect, $\int sin(x^2) dx$ may be in such type
@vzn He is a good linuxer
@JohnDuffield Afaik you should be able to answer problems and questions
@JohnDuffield If you have a better theory, you have to prove that it is really better,

6:45 PM
what a coincidence, a few hours earlier Shing is also asking about using divergence theorem in biology context
Translation: One of my friends asking whether divergence theroem is used in biology
and the guy answered him that it tends to be used in fluid mechanics or EM

7:03 PM
@SirCumference I had a look at the calculation, but I couldn't work out what the values of the parameters should be. When I attempted the calculation I got wildly different answers. What values did you use for $\phi_*$, $M_*$, $M_{Sun}$ and $\alpha$. Also what is that $e^1$ in equation 4? Is it just $2.718...$?

7:19 PM
@JohnRennie That ain't my question
I just bountied it since I didn't know the answer
If you could correct him, I'd gladly award you the bounty
I just need to give it to someone, or I won't even get a badge

7:30 PM
Title seen in the HNQ sidebar: "How do US municipalities get their authority to govern?"
The temptation to make an account just to comment "Strange women lying in ponds" is almost irresistible.

1 hour later…
8:33 PM
@JohnRennie :-)
What is "HNQ"?
@DanielSank I think, this question shouldn't have been closed... now the problem is that closing a question is an automatic thing, while reopening one requires a fight on the meta, what most of us don't really want. The regular VtR votes have only a nearly negligible chance.
Wow, I'm an admin on the chat SE :-) It is the only site where my reps are summed together. .-) If I had focused to a single site, now I would be a 20k+ there... but so is it also okay.

9:15 PM
@peterh This is incorrect. Re-opening has the same rules as closing. There is a "close votes" queue visible to users with access to the review queues and there is also a "re-open votes" queue.
The difference isn't in the system.
It's just that you are more liberal in wanting to re-open things than the majority of the people active in dealing with such things.

@dmckee Yes, but in practice, if a question goes into the VtC queue, it will be probably closed, while if it goes into the VtR, it probably won't be reopened.
2
@dmckee Yes, but it is a clearly problematic difference. The difference is in the mindset of the VtC/VtR voters.

But that fact alone is not a demonstration that there is a problem. In principle it could be indicative that closing is mostly done right and that re-opening is therefore not needed..

@dmckee What is clearly a rationalization. We all know the VtC queue, the voters are simply bored an unmotivated after some hunderds to close decisions, what strengthens the automatized solutions.

It is "clear" to you because it doesn't jibe with your opinion. But it is also clear evidence that most of the active users disagree with you.
That's how crowd-sourced sites work. The people who take the time and make the effort set the policy.

9:35 PM
@peterh Why do all of @peterh's baseless assertions about how the site works get starred?
Note: I'm not saying the assertions are wrong, just that they're baseless.

Hi, I have a question:

I'm thinking of enrolling in a graduate level course in electrodynamics. The course is taught using Zangwill's Modern Electrodynamics (cambridge.org/us/academic/…). This first graduate level course couvers electro/magneto-statics, fields in matter and the basics of Maxwell's equations -- pretty much what is covered in the corresponding first course in undegraduate E&M.

I have done E&M (except for fields in matter and a bit of Maxwell's equations) over the summer. Although I have to admit, I do feeling like going back and revising stuff. I always feel E&M can never b

@dmckee The fact that this question, which has 13k views, is one of the most popular questions of all time, and is on-topic, was closed and hasn't been re-opened, is a good example that the system has flaws.
2

@Pulsar It's popular because it's numerology and it hit the HNQ. People who don't do or know about physics are impressed with that stuff, and we already have, but I don't count that as a good question.
Anedar's answer is very good, but it still doesn't repair that basic senslessness of the question.

@DanielSank But, typically it goes so, if my opinion differs from the ruling view, that I get 20 downs and 2-3 ups. And, this 2-3 up is enough for me to continue. Actually, they are my motivation.
@DanielSank You are a physicist, and I am sure you have a better answer to the domination of the linearity in the physical theories as we can read in the comments.

9:53 PM
@dmckee Numerology? Are you serious? It's about the definition of units! I even linked to this physics arxiv paper on it.

@Pulsar Giving the 5th reopen vote was like an endorphin-explosion in my mind. Now the question is open again. :-)

@Pulsar That case has a basis in history but the idea of comparing the numeric values of (often very random) things comes up over and over again and it is always popular and usually has no basis in anything at all.
And that relationship is specific to the one set of units and the one environment where it was developed. It has no significance to the universe.

@dmckee One of the reasons why MathSE goes so well that questions like this remain open there. Yes, it decreases the mean quality of the site, but 1) only if we see it from an elitist viewpoint 2) actually increases the mass of the HQ content. 13k view is not few, even comparable to the daily hits of the PSE.
@dmckee Popularizing science is also an important viewpoint, and yes, questions like this make common people to think about physics, and they understand that the scientists aren't burbling madmen in ivory towers, but actually there are secrets of the reality, important and interesting secrets, and the scientists are working on them.

@peterh If I was bored and unmotivated I simply wouldn't bother to vote on anything. I vote because I care about the site's quality. Your continued insistence that you somehow can divine the intentions of people on this site better than their explicitly stated intentions is a sign that you don't actually want to have a meaningful conversation about this, but that you just want to push your viewpoint.

10:08 PM
(@peterh excitedly watches his desktop)

@peterh On what?
But you haven't listened, and still characterize people who close questions you think should stay open as "bored" and "sick".

@ACuriousMind Can you get me a flensburger Liegestuhl?

@ACuriousMind Ok. Then instead of debating who should how interpret, who said what, maybe check this closed question. What about a reopen?

@BernardMeurer Uh...not better than anyone else, I'm afraid.
@Real That's not a meaningful combination because it depends on the norm of the state vectors, but the basic principle of quantum mechanics is that states are rays in Hilbert space, so no function of states may depend on the norm of the vectors. The question is unclear because without a specific proposal of what non-linear combination we should be looking at and why, all an answer could say is "because there's no reason to". — ACuriousMind 11 mins ago

@ACuriousMind Dang it

10:16 PM
Why would I vote to reopen a question that I voted to close and that has not changed since then?

ACM just ignore him; the chat is full of your arguments.

@0celo7 Now that's the pot calling the kettle black :P

I don't know what you're talking about.

@ACuriousMind Little deviations from complex, non-linear things tend to behave independently. I think, this is why things like to be linear in physics. Why would be this question unclear?

Oh, wait, is hating on ACM the trend again?

10:17 PM
@BernardMeurer got $20 Spivak it looks$20...

@peterh I have no idea what that means.

@ACuriousMind I have. I explained in the comment.

@0celo7 How is it?
@ACuriousMind You mango-jamber!

this thing is from 1979 and was definitely used.
I should complain, this is not in "very good" condition

10:17 PM
worth $20 though for 20 bucks, what were you hoping for exactly beats a$400 new copy...

Don't be a mangojamber

what
time to reorganize my shelf.

@peterh Well, maybe you tried, but I simply can't tell what your comment means. "But, I think the essence of the question, what it means in the physical reality." - this isn't a proper English sentence, and it's not clear what the "it" refers to or how you deduce "it" is the essence of the question. "I suspect, an accepted answer had focused on that little deviations tend so behave independently from eachoter" - what "little deviations"?

10:20 PM
@ACuriousMind I think, in your case, there is a possibility that you like rigor, what can be a disadvantage for you if you need to understand naive, perfectly informal questions. This is why I tried to bridge the gap between you, and the OP, in the comment.

@ACuriousMind l'ma gonna show you my rigor ( ͡° ͜ʖ ͡°)

@BernardMeurer As long as it's not rigor mortis :P

Those are the best rigors

Hahahaha, good one

@0celo7 That's what your mom always says, eh?

10:21 PM
What?
That actually makes no sense :P

@ACuriousMind OoOoOoOOOO SNAP

@ACuriousMind Because it is about anything. For example, look the linearized GR. Or the perturbative methods in the QM.

Are you calling my mom a necrophiliac
Because...that's messed up

@0celo7 He insulted you on multiple levels

@peterh You're not making any sense. What has linearized GR or perturbative QM to do with "non-linear combinations of vectors"?

10:23 PM

@0celo7 I apologize for being messed up :/

@ACuriousMind In all of these, and many similar cases, there are many, complex, non-linear, but mostly continous correlations. If you change a little bit in its properties, the result will change also a little bit. Such small changes tend to behave independently from eachother.

@BernardMeurer i need help
I have no room on my shelf next to my desk

@0celo7 Get a new shelf

well I wanted to have a second shelf but there's no room
just my bookshelf which is too far away

10:25 PM
@peterh What "small changes" are you talking about, and what has any of this to do with non-linear combinations of vectors in QM?

the only books on this shelf I don't regularly use are the GR books
because I haven't done any GR in a while
and there's only 3 GR books on it
if I move HE and SW there might be enough room...

@ACuriousMind If you see the spectrum of an atom in magnetic field, if you double the field, the change in its spectrum will be also doubled (if the field isn't very strong).

There's a difference between being non-rigorous and not making sense. What you are saying doesn't make any sense in relation to the question we're supposedly talking about.

@ACuriousMind Yes, I make sense. I know very well what I am talking about, and I know, it is okay.
@ACuriousMind Gravitational waves can be also added together, until they aren't too strong, because even the EFE are linear for weak waves.

ok, everything fits

10:29 PM
@ACuriousMind These are 2 examples, but I can make a lot, too.

For heaven's sake, gravitational waves or the dependence of the spectrum on the magnetic field have nothing to do with non-linear combinations of vectors in QM. You're just saying random things related to general non-linearity. This conversation is pointless, and it ends here.

@ACuriousMind can I distract you from this with some math

@ACuriousMind Even the EM is linear until pair production and similar things don't happen.

@0celo7 ...where did you remove them to?

10:30 PM
@ACuriousMind To by other bookshelf, clearly.

@ACuriousMind Yes, but all of them have very clear connection to the original question.

Where was the problem if you have another bookshelf?

I have one that I can grab books from without moving from the desk, and a second one.
I don't want to get up in the middle of thinking.

I see
Maybe you should move the desk to have access to both shelves, then
@0celo7 What kind of math?
If you say "geodesic balls", I'm out :P

@ACuriousMind It does not involve geodesic balls.
@ACuriousMind Geodesic balls are really, really complex.

10:32 PM
@ACuriousMind So, I couldn't know your viewpoint even today. Again.

I thought they existed also on real manifolds...

@ACuriousMind boo.
but still, geodesic balls are an invaluable tool in geometric topology...

@0celo7 Sorry, but bad puns cheer me up :P

no, this does not involve geodesics

Well, then pray tell what it does involve!

10:33 PM
Ok, I have a Riem. mfld $(M,g)$. I want a positive real function so that $hg$ is complete in the Hopf-Rinow sense.
But wait, there's more
By Hopf-Rinow, this is equivalent to showing that the distance topology of $hg$ is complete in the topological sense.
So, here's the idea
You take $f:M\to \Bbb R$ a smooth exhaustion function. This means that $f^{-1}(-\infty,c]$ is compact for $c\in\Bbb R$.

Moderators keep coming in and out, HEAVY BREATHING INTENSIFIES

::hands asthma medicine to @BernardMeurer ::

If you can choose $h$ so that $f$ is bounded on $\tilde g=hg$-bounded sets, you're done

@ACuriousMind Do you have a favorite beer glass?

because, if $f$ is bounded on $B$, i.e. $|f(x)|\le C$ on $B$, then $B\subset f^{-1}[-C,C]$

10:36 PM
@BernardMeurer A large one

take the closure $\bar B$, this is a subset of $f^{-1}(-\infty, C]$, which is compact.
Thus $\bar B$ is compact and $B$ is precompact.

@ACuriousMind Ha, you passed test #317 for being a real German

If the bounded sets are precompact, your metric space is complete.

@0celo7 I'm with you so far, but I'm feeling I won't be able to help with whatever the question is.

So the question is: what the fuck is $h$?
My advisor suggested something like $\mathrm e^f$.
Then you try to get a contradiction, i.e. assume $f$ is unbounded on a $\tilde g=\mathrm e^fg$ bounded set

10:38 PM
@0celo7 Yeah, what about $\mathrm{e}^{-f^2}$?

@ACuriousMind I forgot to mention. Once can pick $f\ge0$.

@peterh He's very much alike most Germans I know

@ACuriousMind What does that do for you?
I'm wondering if one should "shrink" the distances with $f$
certainly $\mathrm{e}^{-2f}$ would do that?
because it's $\le 1$ for $f\ge0$.

@0celo7 I didn't really think about that, it's probably not a good idea

@peterh Why'd you delete your comment?

10:40 PM
@BernardMeurer Because I try to fix the community and not harm it.

@peterh You had just made a joke as far as I can see

I was thinking writing $h=h(f)$, then trying to compute "something" and see what form it should have.
Hmm

@BernardMeurer :-) Thanks!

@ACuriousMind Can you please get a new avatar, this one is disturbing me

@0celo7: So, to say it again, we want that on sets bounded in the distance metric induced by $hg$, the function $f$ is bounded?

10:42 PM
if you take $\mathrm{e}^{-2f}$, I think distances wrt. $\tilde g$ are always equal to or shorter than with $g$.
@ACuriousMind Precisely.
@BernardMeurer would star again.
@BernardMeurer Shankar is no longer on my shelf
in fact, no physics physics books are on it

@BernardMeurer :-) :-) :-)

@ACuriousMind Test #318: How much do you hate Deutsche Bahn?

@ACuriousMind Based on my geometric analysis expeditions that I take from time to time, I strongly suspect one can pick $h$ so that $f$ is $\tilde g$-Lipschitz.

Hmmmm. I'm having trouble to think about this because I don't have any intuition for the induced metric. However, you're right that the distances for $\mathrm{e}^{-2f}$ will always be shorter.
@BernardMeurer It has not yet run its course

And that suffices to prove it's bounded on $\tilde g$-bounded sets.

10:45 PM
I need time to think about who to take next
I think it'll be a pretty lady again
@BernardMeurer Not much, actually. My experience with it has so far been rather good.

@ACuriousMind Hmm... Maybe you're just Belgian or something
My experience with DB has been horrible

wtf
every german hates DB

@0celo7 As I suspected, I can't help with that question

@ACuriousMind What do you mean

@peterh How do you feel about DB?

10:50 PM
@0celo7 I don't. The other Germans laugh at me for that

I don't think I need to prove it's Lipschitz, that's pretty strong.

@0celo7 I mean that I am unable to help you with that question - I'm not sure what's unclear about that

I wonder how something crazy like $g/f^2$ works.

@BernardMeurer The DB says their trains can go with 300km/h. In fact, they go around ACM's region at most with 130. But they are at least clean and there is power supply for your devices. In other countries they go with 40 km/s and they are dirty. They seem working heavily to make the public transport feasible, but they are still very far from it.

@ACuriousMind Problem is I don't really know where to begin. Boundedness of a set is defined via an integral, which is actually quite crude.
An integral cannot reliably detect if its integrand blows up

10:53 PM
@peterh I'd rather have a dirty train on time than getting a 3-4h delay in bloody Kiel

where the hell are you

@0celo7 I think he's talking about past events :P

@0celo7 Rio?
@ACuriousMind Yes, July 2015

@BernardMeurer Yes, but you can buy a car from the cost of around 10 travels... and there is no speed ilimit n Germany on the highways...

@peterh Not all the highways have no speed limit though, right?

10:57 PM
@BernardMeurer Well... I must admit I never watched this little tables around the roads very carefully :-) But as I can remember, if there is no some maintenance work, which is unfortunately common there, then there is no speed limiz.

And also I, for one, have no interest in buying a car whatsoever

what kind of desperate women are there where you live that consider guys without cars

@peterh Watch out, you're going to miss the right ausfahrt and get lost forever in the black hole of Bielefeld

@0celo7 Almost no student here owns a car.

@0celo7 Rebecca started dating you before you had a car. So that kind of woman

10:59 PM
@ACuriousMind Literally insane

@0celo7 why? You don't need a car to get anywhere, we have working public transportation :P
It's just expensive and most useless