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4:00 PM
I plan to live forever
Shouldn't be too hard
Just gotta avoid dying
 
fite god
 
-6
Q: SCIENCE IS THE BEST BUT I HAVE QUESTIONS

J. Doewhat does this have to do with AIR PRESSURE PEOPLE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!...

 
user228700
Omg lol x'D
 
I love the way someone has attempted a rational reply in a comment :-)
 
user228700
"PEOPLE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!" x'D
 
4:03 PM
stack exchange is the best but i got banned!!!1!!
 
user228700
@JohnRennie I bet it features a lot of Ogden Nash :-)
 
The Hippopotamus by Hilaire Belloc

I shoot the hippopotamus
With bullets made of platinum,
Beacause if I use leaden ones
His hide is sure to flatten 'em.
 
user228700
That's...nice :-)
 
user228700
Oooh, @JohnR: Did u see the thing about the abandoned ferris wheel?
 
A crusader's wife slipped from the garrison,
To have an affair with a Saracen,
She was not oversexed,
Nor jealous nor vexed,
She just wanted to make a comparison.
@Kaumudi.H Abandoned ferris wheel? No, what was that?
 
user228700
 
user228700
...and a few lines of conversation following that.
 
Scary stuff - the ghost of communism
Probably the question asked most often is "Do one celled animals have orgasms?" The answer is yes, they have orgasms almost continually, which is why they don't mind living in pools of warm slime.

Dave Barry - Sex and the Single Amoeba: What every Teen Should Know.
 
Boooo the workers shall control the means of productiooon
 
Good grief, the new Hawkwind album is no. 2 on the BBC Radio 1 rock album chart.
 
4:25 PM
Who listens to radio, anyway?
 
> Recent evidence indicates that several Amoebozoa lineages undergo meiosis.

Orthologs of genes employed in meiosis of sexual eukaryotes have recently been identified in the Acanthamoeba genome. These genes included Spo11, Mre11, Rad50, Rad51, Rad52, Mnd1, Dmc1, Msh and Mlh.[51] This finding suggests that the ‘’Acanthamoeba‘’ are capable of some form of meiosis and may be able to undergo sexual reproduction.

The meiosis-specific recombinase, Dmc1, is required for efficient meiotic homologous recombination, and Dmc1 is expressed in Entamoeba histolytica.[52] The purified Dmc1 from E. histo
An amoeba (/əˈmiːbə/; rarely spelled amœba, US English rarely spelled ameba; plural am(o)ebas or am(o)ebae /əˈmiːbiː/), often called amoeboid, is a type of cell or organism which has the ability to alter its shape, primarily by extending and retracting pseudopods. Amoebas do not form a single taxonomic group; instead, they are found in every major lineage of eukaryotic organisms. Amoeboid cells occur not only among the protozoa, but also in fungi, algae, and animals. Microbiologists often use the terms "amoeboid" and "amoeba" interchangeably for any organism that exhibits amoeboid movement. In...
Ok, I thought that guy is making some kind of sexual themed alternate theory on animal reproduction, turns out nature is stranger than you think
 
@ACuriousMind I listen to mostly (Internet) radio these days. I find it's a good way to hear about new bands that I wouldn't otherwise know about. Admittedly I get to listen to a lot of crap bands too :-)
For the record (no pun intended) the new Hawkwind album probably won't appeal to any but the die hard Hawkwind fan.
 
-7
A: Is the influence of gravity instantaneous?

dv1penguinIf the speed of gravity were equal to the speed of light, which most conventional astronomers believe, our solar system would have evolved in a completely different way. The speed of gravity is a critical physical fact that tells us why the theory of General Relativity is an absurd hypothesis i...

Love Rob Jeffries' response
 
"He didn't just make it up like Mr. Einstein would do."*
@AlbertEinstein what do you have to say for yourself
 
4:43 PM
> There are many einsteins, but only one is real
 
Also more importantly
If I do a GR book
what do I call it
I get the impression that GR books either have very short or very long titles
It's either "Gravitation" or "Exact solutions of the einstein field equations"
 
"GR", or "A complete treatise on gravitational phenomena, from differential geometry to cosmology, geodesic motion, black holes and causality - A new perspective - Volume I."
 
Pretty much
Just like old timey books
Galileo's own "The Discourses and Mathematical Demonstrations Relating to Two New Sciences"
 
I would have gone with "science, yo' - Galileo"
 
I would go with: The Mathematical Theory of Gravity
Well, maybe not
My hypothetical book doesn't really concern itself with gravity
How about just "Mathematical General Relativity"
 
4:58 PM
Yeah I'm gonna have it a bit more grounded in physics
 
I guess I could just call it "general relativity", but then there's a lot of books with that title
cuz I'm a physicist
 
GR is not a realistic physical theory though
 
Is it
it predicts a ball falling down
 
5:00 PM
pretty good prediction
 
that's the book with Sanchez in it
I think
 
nice
 
Actually no...
It has a Sanchez article in it
But not the usual one
 
What is the prediction of throwing a ball in GR anyway
I don't think Schwarzschild has a generic solution for geodesics
 
god, who knows
 
5:01 PM
Radial one is probably doable
 
@Slereah Radial for sure
General orbits are not analytically known
 
@Slereah Go for something more eye catching, like "10 wacky equations (solutions inside!)"
 
one approximates with Newton +$1/r^3$, then does some shit
 
I guess throwing a ball straight up has a solution
 
it's in every book
 
5:02 PM
Did anyone do that experiment
Throw a ball up
Look at the deviation from Newton's theory
 
Guys, is it possible to visualise why a field, whose curl is zero, must be the gradient of a scalar valued function? (I can prove this direction: $E=-\nabla V\implies \nabla\times E=0$), however, since the proof in the other direction involves advanced maths, I was hoping I could make this intuitive for myself. Is it that rotating vectors cannot represent a gradient? (if we're thinking of the steepness of hills, for instance)
 
@Slereah Thank me later
 
@ShaVuklia Think about if the vectors are gradients, it tells you which direction is uphill. Now think about what happens when you apply this logic to a swirling vector field
 
yea I was trying to visualise that
let me think (or draw)
 
In the meanwhile I have to do my homework
Terrible
 
5:08 PM
@Secret wouldn't we get something that spirals upwards?
 
@ShaVuklia No, you will get something that look like a penrose stairs after you completed a cycle around the region of nonzero curl
 
ohhhhh, wow
 
which means the start and end point will have two values for the potential (the height of the hill) and we normally don't use multivalued potentials
 
did not think of that at all
wow, I had no idea the answer was that simple
 
and this is why any nonzero curl vector field is not a gradient, because if it were so, we would already have a perpetual motion machine by placing a ball bearing in such potential
as it will, as you have noticed it forms a spiral, it rolls downhill forever, releasing unbounded amount of kinetic energy
 
5:11 PM
wow, that makes sooo much sense.
damn, I did not expect such a satisfactory answer
thanks
 
(Unrelated: Too bad physical infinities don't exists, (except possibly the gravitational singularity in black holes), otherwise economics would be much simpler)
Pictures are often good at intuition, but it only really helps if you have a solid understanding of the subject in question
and there are concepts too abstract to be captured by pictures without distortion, thus be aware of different learning methods
 
yea true
I must say tho; since I've been doing physics the past two weeks, I've really had to resort to my intuition many, many times. I think mathematicians have the luxury of being able to turn of their intuition and simply work from definitions and theorems.
 
Question: is chemistry just physics in disguise?
 
Chemistry=mostly electron shell physics, plus some rules of thumb
 
Like, people complain that there's an astronomy SE (saying that astronomy is just physics), but no one says anything about chem SE
 
5:16 PM
@SirCumference no
chemistry is a bunch of rules of thumb
 
The thing is, while yes it is fundamentally electron shell quantum physics and statistics, the methods and thinking process (such as the emphasis in an array of representations and diagrams to aid in the thinking, and the heuristic guidelines) makes chemistry so distinct it can no longer be considered completely a subdomain of physics
 
Hmm, so where do you draw the line between Chem and Physics?
 
Please don't call it Chem.
 
Honestly, I hate chemistry. A lot. But I get annoyed when people say it's just physics. If it were physics, then physics would have to: 1) be complete and 2) allow the results from chemistry. I feel like analytically solving the schrodinger equations for heavy metal atoms would be a huge waste of time and at this time impossible.
 
It's Chemistry.
 
5:19 PM
@0celouvskyopoulo7 You don't say "astro"?
 
No.
I say "trash."
 
I realize now that sounds a bit nerdy...
 
@0celouvskyopoulo7 Math or Maths
 
@0celouvskyopoulo7 on page 43. . . working through defs and concepts . Got back on the horse this morning. "(It is left to the reader to
understand how to make the set of equivalence classes into a vector space.)"
 
Math is fine.
 
5:20 PM
Oh
Well, die
tbh
 
@Cows You're doing $L^p$?
 
@0celouvskyopoulo7 Well, one man's trash is another man's treasure, I guess
 
@Phase Did you just say I should die?
 
@0celouvskyopoulo7 yup!
 
Did you just assume my subject
 
5:20 PM
@SirCumference I was trying to toll you, I guess you're learning...
@Phase You're not German
 
I'm also not French
or Spanish
 
@0celouvskyopoulo7 ;-;
 
or Japanese
 
@Cows What's unclear to you?
 
The line is extremely blurry if you are working in physical chemistry domains such as quantum chemistry, computational chemistry, solid state chemistry, thermochemistry and photochemistry, where a lot of things overlap.

The line is more clear cut for things like organic chemistry, coordination chemistry, where we mostly think of heuristic periodic table trends, and orbitals, and laboratory preparation, reagents and reaction conditions, and does not involve much quantitative analysis
 
5:22 PM
@Cows Let $\mathcal L^p(\Omega)=\{f:\Omega\to\Bbb F\mid ||f||_p<\infty\}$, right?
 
@SirCumference Astro is cool, I just hate it because at the levels I've learnt it it's always been memorising formulae and definitions, without any real flexibility in the maths unlike normal classical mechanics questions. i'm sure it's different high up tho
 
So let $\sim$ be an eq. rel. on $\mathcal L^p$ such that $f_1\sim f_2$ if $f_1-f_2=0$ a.e.
 
@0celouvskyopoulo7 hang on let me switch to chrome for the mathjax to kick in
 
Then $L^p:=\mathcal L^p/\sim$.
 
@Phase Don't memorize them. Try to understand them.
Then it becomes cool and fun
 
5:23 PM
Clearly $\mathcal L^p$ has a vector space structure since it is a function space, and you have the Minkowski inequality. So that structure descends to equivalence classes (elements of $L^p$). It's not hard to see how.
 
@Phase Yup , it is still impossible, this is why all existing computatonal methods on that are numerical. As for whether that is useful, well our iphones etc. works because of these
 
@SirCumference what I meant is that for normal classical mechanics, you can go in knowing things like $L = rmv sin(theta)$, and with a few integrals describe a systems angular motion and how that changes
meanwhile with Astro at the level I've learnt it it's uh...
Very static and seems like number crunching
 
@SirCumference Astronomy is a subdomain of physics, but its community has grown large enough to warrant a separate SE site. One cannot claim a subdomain is the domain itself
 
@Secret Are observational astronomy and telescopy subdomains of physics?
 
That honestly I don't have enough background to answer correctly, but IMO, I suspect they are part of astronomy and hence are subdomains of physics
But if you talk about things like astrobiology, astrochemistry, etc., then these are multidiscipline and not a subdomain of anything
 
rob
5:28 PM
 
I think it's mostly theoretical astronomy that uses physics
Wtf mobile chat...
 
@rob I will soon be able to put fine arts, religion, liberal arts, spirituality, etc. into that picture now that my knowledge domain have recently expanded to that
(Villian crackle) On the process of colonising all knowledge domain of humanity
 
Is AlbertEinstein still in the chat or has he been banned yet?
 
@Phase "Yet"?
 
Idk, just seems like all the warnings are for naught
 
5:32 PM
What warnings?
I don't think there's a rule against being annoying. At least not unless you annoy mods
 
The barrage of short questions
Oh, I figured the warnings were formal, didn't realise it was just "or else I'll ignore you"
Haven't really been as active in the chat so haven't been around to see stuff.
 
@JohnRennie Is it reasonable to have a types.h just with all the custom types I need?
 
@0celouvskyopoulo7 yes, the book says this too. I just read this part. I am trying to make sense of of some of it. Let me chew on the concept for a while.
 
@Cows are you familiar with quotient vector spaces?
This is exactly the same thing
 
Ohhhhh
 
5:40 PM
You have a space $N(\Omega)$ of measurable functions $f:\Omega\to\Bbb F$ with $f=0$ a.e.
 
i see
 
You're quotienting $\mathcal L^p$ by $N$.
So $f,g$ are equal in the quotient if $f-g\in N$.
So giving $L^p$ a vector space structure is the same as giving a quotient vector space one
Basic linear algebra
 
@0celouvskyopoulo7 perfect!! got it
 
5:59 PM
Let me know if I left anyone out:
user image
2
Take home message: Sciences are more well defined in terms of purity
 
@Slereah Currently reading the "Journal of Mathematics and Mechanics"
Seems like a strange name.
 
what, all of it?
 
Yeah
There's only like 300 volumes
@Slereah please save me
 
6:16 PM
of what
 
PDE
I have a headache
 
close the book
 
not a book
 
@dmckee I want templating in C :P
So that I can have the same linked list structure for multiple types
Actually
I got a question @JohnRennie @dmckee
 
close your eyes
 
6:20 PM
@BernardoMeurer People used to do that with code-generation schemes. Now they just write is the c-like subset of c++.
 
Suppose I have a CSV file, I've read it into memory (char*) and I'm now parsing it into a data structure. What's the best way of doing this?
 
I found a open source library for that once.
 
If I do a m/calloc I'll need to realloc after every line to add the next thing
 
It respects the RFC and everything.
 
No libraries out of the standard allowed :/
 
6:21 PM
You did know there was an RFC that everyone ignores, right?
 
Should I do a linked list?
There's an RFC?
 
@BernardoMeurer SO there are two separate questions here. Te first is "how should I parse the file?" and the second is "How should I store or manage the results?".
 
@dmckee I'm parsing with strtok, is that not good? Using "\n," as a delimiter for the tokens
 
And the answer to the second depends on how you are going to use the data.
 
I already have a structure that holds a single entry
typedef struct bikeStation {
    unsigned int ID;
    id terminal;
    char *name;
    char *city;
    coord location;
    bool status;
} station;
 
6:23 PM
@BernardoMeurer It's hard to make it respect the RFC (or any scheme for escaping commas).
 
boolean
 
It's better to write a state machine or a recurse desecnt parser.
 
6:24 PM
But for a class assignment you may not need that. Read the spec carefully.
 
@dmckee Is it worth the trouble? to just parse a simple CSV?
I don't need it to be general or anything
id,terminal,station,municipal,lat,lng,status
3,B32006,Colleges of the Fenway,Boston,42.340021,-71.100812,Existing
4,C32000,Tremont St. at Berkeley St.,Boston,42.345392,-71.069616,Existing
5,B32012,Northeastern U / North Parking Lot,Boston,42.341814,-71.090179,Existing
6,D32000,Cambridge St. at Joy St.,Boston,42.361285,-71.06514,Existing
 
@BernardoMeurer The state machine is maybe 40 lines. But "Is it worth it" depends on the input. Will there be escaped commas or not?
 
I just need to parse that into the structure I presented
No escaped commas
 
Then strtok will work. Leaving aside its horrifying use of local static storage.
::shudder::
 
I was thinking of reimplementing this
Because it handles blank tokens
Which I need for the other CSV I gotta parse
@dmckee But the question remains, do I do a linked list or do I just do a malloc and then reallocs
@dmckee I'm going with linked list
Cause realloc() is slow af
 
6:51 PM
@dmckee Is it easier to quicksort and manipulate doubly linked lists?
 
0
Q: Comment votes can be easily gamed

Sir CumferenceWhen someone deletes an account, the upvotes they left on comments are not removed. When they create another account, they can upvote these comments once again. This is a huge problem, as you can give a comment as many upvotes as you want by: Upvoting the comment Deleting your account Repeatin...

This is bad
 
@SirCumference Read your last paragraphs
 
@BernardoMeurer What?
 
This can even be done very quickly, since upvoting a comment doesn't require you to contact SE to delete your account (the "Delete" button will remain in your profile settings).
This makes little sense
 
What doesn't make sense about that?
Jesus christ backlash
 
7:07 PM
@ACuriousMind algebraic bat signal
 
@BernardoMeurer The mechanism will look a little different, but I am sure you can do it.
@SirCumference Don't rile the meta.
 
struct Node* GetNewNode(int x) {
	struct Node* newNode
		= (struct Node*)malloc(sizeof(struct Node));
	newNode->data = x;
	newNode->prev = NULL;
	newNode->next = NULL;
	return newNode;
}
 
But seriously, the way to deal with it is not to give any weight to comment votes in considering arguments.
 
@dmckee Why the heck do people use structs for that and not a void func?
 
Tell people to put it in an answer and see how the real votes fall.
 
7:10 PM
@dmckee What do you mean?
 
In some case you can also flag the comments as noise to be deleted.
 
@dmckee But darn, I was not expecting such opposition
 
@SirCumference Comments that people might care to falsely amplify are mostly on meta. On meta we are a bit more forgiving about topicality of answers. So ask the author of the comment to make an answer of it.
You can do the same on the main site if the comment is a pseudo-answer.
Some of are more pernicious trolls have been forced to mightily resist that, making it clear that they know the way their notions are perceived.
 
Ah, nevermind that question
I was being stupid
 
Then they fall back on, "its a consipracy", but it makes the situation clearer to casual readers.
 
7:14 PM
@dmckee Well, some of the people resisting have >50k rep on some sites
 
@SirCumference Hmmm ... I think you may have misunderstood my suggestion. I'm saying that we have a work-around for the problem you want to solve: push commenters to commit their ideas to answers where they can't easily falsely increase the vote count.
That is, I'm not worried about comment vote counts and don't feel the team needs to rush out and do anything about it.
 
@dmckee I suppose, but then what's the point of having comment counts if they're broken anyways?
 
I'm pretty sure I can guess how many votes a stupid comment on meta.physcis will get because I know which users feel that way. And that implies that people aren't falsiely inflating their counts.
 
I don't understand what the problem here is - can 1 rep users upvote comments?
 
They are mostly not broken: they are breakable, but there is no payoff in it, so it rarely happens.
 
7:18 PM
@ACuriousMind Anyone with the association bonus can game them
 
@dmckee I need a tip on naming schemes. I have two types, station and trip, each has an associated doubly-linked node type named station_n and trip_n. I'm implementing utility functions (add node, remove, etc) for both. What to name, for example, the insertHead() function for each of the types?
 
@SirCumference See, that's not clear at all from your meta post. So, the issue here is that deleting an account on one site and then immediately recreating it allows me to upvote comments again?
 
@ACuriousMind Yup
 
@BernardoMeurer That's why c needs namespaces.
 
Also, the post is not quite clear on how you came by this information - did you test that yourself?
 
7:19 PM
Meh, templates would solve it
But I ain't got those either :P
 
I usually go with inertFooAtHead() and the like.
 
Yeah, that's reasonable I guess
@dmckee Am I wrong to always use calloc()?
 
@BernardoMeurer Template need a name mangling scheme which is the infrastructure upgrade needed for namespaces, too.
 
I just like to stay safe
 
@ACuriousMind Yeah, I noticed that, when I deleted my account, the upvote remained
I haven't abused it, of course
 
7:21 PM
@dmckee Aha! I did not know that :)
But C ain't getting neither templates nor namespaces I'm afraid. But to be fair I don't even know what's in C11
 
@BernardoMeurer It is traditional to default to malloc unless you known you want the zeros because there is no guarantee that calloc is as fast as malloc.
 
@dmckee I just like calloc better because it handles the allocation size arithmetic with failsafes
 
But that tradiation has it roots in the days when computers were slow, and arguably the repeatability of bugs you get using calloc is worth it today.
 
@ACuriousMind ?
 
@0celouvskyopoulo7 !
 
7:23 PM
Yes, no?
Too drunk to answer?
 
Not drunk, but not sure what to answer
 
@ACuriousMind My algebra question
 
@dmckee Just read on the C11 changes, nothing special there, apart from threading
 
@0celouvskyopoulo7 where is it?
 
@ACuriousMind In my head
Do you want me to ask it?
 
7:24 PM
When I start answering questions in your head you might need help ;P
Ask away
 
@ACuriousMind I was just testing if you can read my mind.
Just to...make sure.
 
If I could, would I not have also read that and avoided giving it away?
 
@ACuriousMind You might have thought "oh, I missed it!" then read my mind to obtain the question, rather than looking for it and concluding I never posted it.
Ugh, this is a technical question
@ACuriousMind I don't think the Sobolev spaces are important here, it really is just the linear algebra. I have a function $u\in W^{2,q}_\delta$, and I know that $\Delta u\in W^{0,q}_{\delta-2-\tau}$. Now $\Delta :W^{2,q}_{\delta-\tau}\to W^{0,q}_{\delta-\tau-2}$ is Fredholm (finite dimensional kernel and cokernel).
So the idea is to show that in $E_R=R^n-B_R$, we can find $v\in W_{\delta-\tau}^{2,q}$ with $\Delta u=\Delta v$.
And it's remarked that this cannot generally happen in all of $R^n$.
 
@dmckee Uuuugh
C'mon...
 
So in a sense, $\Delta$ is surjective on $E_R$...
I want to argue as follows: $\coker \Delta$ is finite dimensional.
 
7:32 PM
@SirCumference Look, I think it is cool that you've found a technical flaw in the system. Well, done. You get the 'Genius of the Moment' award (Savior it quickly it moves on fast!), but there is no evidence it is a big problem.
 
So the image of $\Delta$ only misses finitely many linearly independent functions on $R^n$
 
@dmckee Sigh...
 
So I claim that the functions that $\Delta$ misses are characterized by their values inside of $B_R$
 
I think I'll just give up, no one's listening to the other
 
Guys, sorry to interrupt, but I have one question. What was the main motivation to define potential energy? I understand that the potential is a scalar field, as opposed to the vector field of a force, so that is nice. However, why did we associate this quantity with energy?
 
7:34 PM
Because if $\Delta$ misses some function defined on $E_R$, then I can change the values arbitrarily in $B_R$ to produce more such functions
 
I understand that the work done by a force was practically defined as the change in kinetic energy, so was part of the purpose of defining potential energy in this way that we would have a sum (kinetic energy + potential energy) that is always constant, which is in line with our assumption that the total energy of an isolated system remains constant?
I’ve always just seen it as a definition, but I’m wondering if this really is the “motivation” or maybe intuition behind it. I keep forgetting that a (conservative) force is the negative of the derivative of the potential, because I just don’t have any intuition for it.
 
And eventually end up with an infinite dimensional cokernel
Now that I say that, it sounds nothing like what was in my head
@ACuriousMind Did that make any sense at all?
I think my idea is right though, I just need to formulate it precisely.
@ACuriousMind The idea is that if $\Delta$ cannot reach this magical $f$ outside of $B_R$, I can just change $f$ inside of $B_R$ (without leaving the Sobolev space) to create a bunch of functions it misses on all of $\Bbb R^n$. This contradicts the Fredholm hypothesis.
 
@dmckee If I want to compare structures can I just do a memcmp?
 
@SirCumference argh, what's wrong with people?
I dont get it
 
Thank you
It just baffles me
 
7:42 PM
I mean, I get that it might not be a top priority
but it is a very valid point
they could, you know, just say "yeah, we'll keep this in mind. Thanks"
but for some reason they are trying to argue that your post is pointless and nothing really matters
whatever
 
@AccidentalFourierTransform I know right? It can actually be a problem, but they're now arguing that upvoting comments is pointless
Way to ignore that a system is broken
 
are they really trying to argue that a comment with 40+ upvotes will have the exact same impact than one with no upvotes!? that they are to all purposes equivalent!? have they ever used SE!?
 

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