The h Bar - 2015-02-03 (page 1 of 2)

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12:06 AM

@tpg2114 A toy project with a couple of students and a little coding for my last post-doc experiment.

lol did someone say "vegas escort"? & without a link? bummer missed the fun :\

@ACuriousMind what is this catastrophe that you did to your face? Please change this image. It's unbearable !!!!!!!!!!!!!!!!!!!

@ACuriousMind : why did you change your picture? It looks like a vampire !!!!!!

@Sofia Hahaha...that was a Halloween masquerade

And I changed my profile picture because I began to find old Edwin boring and because I probably didn't own the copyright for that picture.

user54412

12:25 AM

@DavidZ That's just nasty. You aren't inserting long, space-requiring strings of words in a text-inside-math-inside-text environment, just upright math symbols, so you should use \mathrm rather than \text. And the space separator is not upright, any more than the period after inline math should be italicized. Semantically it should be 10\ \mathrm{m}, or 10\,\mathrm{m} if you're one of those people who like having a multitude of different horizontal spacings in the same line.

One could, of course, \usepackage{siunitx}.

Not that I do, I use the \,\mathrm{} strategy.

But you could.

user54412

Ever since I started submitting papers, I've grown to fear most packages. I always imagine getting in trouble with some copy editor or with some "we'll compile your source for you" submission framework.

The Physical Review system is pretty robust and it lets you look at the output they're getting so that you can fix it if there is a disaster.

user54412

Astro does that too, to varying degrees of success. But I don't like finding out things are incompatible the day I'm submitting.

@ACuriousMind I guess that soon you go to sleep. I though insist that you change it. If you want, I can send you a picture, which is a beauty. Just say yes.

@ACuriousMind : unfortunately, it's I who has to go to sleep immediately. So, good night and pleasant dreams!

12:43 AM

@Sofia Sleep well. I think I'll stick with this picture for a bit, though

@ChrisWhite yes, good point. I would only use \text because it's marginally easier to write $10\text{ s}$ than $10\ \mathrm{s}$ but I'm getting away from that.

@dmckee not in MathJax

1:05 AM

@tpg2114 Yeah, I've done some FPP'ing in the past to debug pure routines. I can't imagine it changing performance any, since, AFAICT, it only ensures the compiler checks for intent and that there are no side effects. Other than that, it's the same as any routine

1:22 AM

@KyleKanos The argument is that by making sure there are no side effects, it can be run at the same time other functions are run

Since you know there are no effects outside of the routine

It should be faster because the compiler should vectorize the PURE (and ELEMENTAL) routines

But in our experience, it just never actually is any better

So the biggest perk is knowing exactly what each routine does and that it does nothing else

That makes sense

Have you tried comparing adding the force vectorization flags in there?

No, we haven't gone that far to use the pragmas

We also haven't tried using the auto-parallelization compiler options

Well given 96 hours to compile.... ;)

Intel is much faster!

I know

I was just poking fun at NAG

1:26 AM

But we haven't tried to figure out that side of things. We figured it might help on a serial code to make it faster

But on a massively parallel, distributed code we just use more MPI threads rather than trying to let the compiler figure that out

That sounds reasonable.

I kind of want to save some money up and build a cluster of Rasp. Pi's new computer

I found some LINPACK specs for the old board but not the new one

Like a Beowulf cluster? Or an actual mini-cluster?

Actual mini-cluster

So the old version was at like 150 megaflops

Interesting....likemagicappears.com/projects/raspberry-pi-cluster

1:33 AM

An Intel Core 2 is at like 1600 megaflops

The new version is supposed to be 6x faster (whatever that means really)

So maybe like 900 megaflops per board?

And each board has 1 GB RAM in the new system

So even if a single board is the same as half a Core 2, that's kinda cool

20-30 of them and it would be a reasonable little minicluster. Although that might work out to be more expensive per flop than a decent quad core machine

Still, at <$50 pi is a decent piece of work

And you're not limited to someone else's cluster

It's $35 for the new one, but it might need some more than just the base hardware

I ahven't looked into it too much

Just thought it could be fun

It's like the BlueGene systems IBM likes to build. Millions of cores but each core only has like 512 MB of RAM and is a crappy processor

The people who develop my MHD code have a BlueGene cluster on site (or at least on campus)

We tried using one, we couldn't get running

Their head node didn't have enough memory for us to generate our grids or message passing information

raspberry pi supercomputer :)

1:40 AM

And their internet connection was too slow for us to generate it locally and send it

Yeah, AstroBEAR is supposed to be rather efficient

@vzn Man, that's a cluster I could get behind

←jealous wish sof would offer to send "beautiful picture" lol

@KyleKanos Our problem is our full code requires a bunch of grid generation and domain decomposition beforehand. We have a timing-only version that generates the grid/mapping on the cores when it runs

Rather than a pre-processing step

From what I can tell, A-BEAR maps out the domain boxes on a single processor, then fills them

1:43 AM

clicking on kyles link, makes me wonder, could it be though that raspberry pis as cheap as they are, are not so great in price/ performance/ cost ratio(s).... and actually similar to what you guys are saying, maybe someone needs to attempt to calculate this price/ performance ratio for different cpus....? eg wrt linpack etc.... have never seen that....

After filling up with ICs, it checks if the gridding is correct and adjusts as necessary

@vzn The RPI's aren't intended to be cost effective from a performance standpoint

They recently made the regridding parallelized, but I haven't DLed that branch yet

They are supposed to be cost effective in the barrier to entry sense

Only (mildly) crazy people would want to build a cluster out of them

And mostly just because it's cool and you could have a tiny supercomputer

tpg ok figured that but then what is a good cpu... or maybe those calculations (est price/power of different cpus) are done every time new clusters are built.... it would be neat to see that analysis....

1:47 AM

Yeah, that is a big trade off. That's why the BlueGene's exist -- ridiculously low power consumptions

whats your guys take on Arms/ low power cpus in clusters? thought that was catching on last heard...

So people definitely do those studies. We're in the "maximize performance" category so we don't care about power consumption or cost

I haven't used any ARM processors

Nor I

But again, the BlueGene's use a PowerPC CPU that is very low power and approximately the same clockspeed as the ARM's

hpcwire.com/2015/01/27/…

Those guys are taking retired cellphones

And although many people built a PS3 cluster, I'd like to see the productive research time vs. the call of duty time

2

PlayStation 3 cluster

The considerable computing capability of the PlayStation 3's Cell microprocessors has raised interest in using multiple, networked PS3s for various tasks that require affordable high-performance computing. == PS3 clusters == The National Center for Supercomputing Applications had already built a cluster based on the PlayStation 2. Terra Soft Solutions has a version of Yellow Dog Linux for the PlayStation 3, and sells PS3s with Linux pre-installed, in single units, and 8 and 32 node clusters. In addition, RapidMind is pushing their stream programming package for the PS3. On January 3, 2007, Dr....

tpg thats very cool/ ideal/ lucky to be in a "money is no object" environment wrt this...! even ignoring power consumption! so it sounds then like youre in the business for the most expensive/ high performant cpus no matter what....

1:58 AM

@vzn Well, there's only 2 (serious) CPU players and they sell to governments/businesses who do care about costs. So, the cost comes down because they need to sell these things

intel & ...?

So we get the best processors, which are also the most expensive, but it's not unlimited expense because other customers keep the prices in check

AMD

All Cray systems were on AMD chips until a year or two ago. They finally started moving them over to Intel's though

IBM still makes processors too, but they are less commonly used

yeah the move by apple to intel was a big shift also probably having significant effect on market.

And weird. Big-endian is annoying

Apple was using the IBM chips until they switched

its probably good for consumers that intel/ amd compete...

2:01 AM

The funny thing is AMD invented the x86_64 architecture by extending Intel's x86 32-bt architecture for 64bit processing. Intel tried to make a whole new thing, ia64, but then found out it wasn't very good and so they adopted the x86_64 that AMD made

yeah. "cross pollination".

Intel played dirty for awhile and got sued for it. They made their compiler suite disable a bunch of optimizations if it detected you were running an AMD processor

So all their benchmarks ran super slow and they convinced people it's because the AMD chips were slow

AMD was very competitive some years but afaik its not near the same scale as intel. scrappy, its amazing they are so competitive.

So they got sued and busted for it, had to return money to customers. Now their compiler documentation has warnings that performance "may" be "compromised" on processors other than Intel

interesting. very similar to some stunts pulled in windows OS yrs ago.

possibly causing competitors code to break. not sure if it was proven in court but it was rumored for years.

actually, guess it was basically proven in the case of java & ms had to pay millions $$$ in damages in settlement.

2:04 AM

Wow, the GPU in a Nintendo 64 has the same performance as a RPi

suspect google/ amazon/ facebook are interested in different configurations on their clusters but havent heard too much about them, they are all pretty secretive.

@tpg2114 Apple had been part of the technology consortium responsible for Power PC R&D. When they decided to ditch that the processor decition was easier.

Plus OS X which is BSD on a mach microkernal also made processor architecture changes easier.

They'd had a belly full of trouble during the m68k to powerpc transition and knew that they didn't want that again.

I've never owned a single thing Apple has made, ever. So I don't know a lot about their hardware

Aside from it was a big deal when they switched from PPC to Intel

And that their OS was a flavor of unix

My first computer was Dad's Apple ][+, and I've had a mac now and again over the years.

In fact I've had one with every processor they ever used except the 68030.

The earliest I remember playing with was a Commador 64

But after that, it was all DOS machines with the *86 processors

2:18 AM

These days I use a MacBook because it's unix underneath and all the accessories work.

I've had linux laptops several times, but there is always something that isn't supported on the fool things.

From... 2000 until I got this computer in late 2013, I've only run linux

Now I'm on Windows 8.1 and I actually like it more than any other Windows. Probably because it's more like Gnome/KDE than Windows

With homebrew I'm able to participate in particle physics programing and still have a easy to setup descktop.

I've been avoiding windows 8, but the school is switching our desktops this summer. Is there something I should know to make life easier for myself?

Not really

8 is kinda lame because of the default login to the Metro screen instead of the desktop

But 8.1 fixed that

Otherwise, I've found all the "poweruser" things I ever needed in Windows are still in the same place on the control panel and stuff. I haven't had a "start menu" since Gnome 3 came out and got rid of it

So I don't miss that either

Hmmm ... I've never been good at windows, so I always open the tools from the start menu. Oh well, I can still learn computer things.

On my laptop, if I swipe from right to left, it pops out a little bar that you can search in

So if you start typing the program you are looking for, it brings it right up

Which is what Gnome did also

user54412

2:32 AM

@tpg2114 what does "swipe" mean? with your finger? the mouse?

So for me, it's way way faster than looking through the start menu. I can get 2-3 letters of my program typed in and hit enter and it works

@ChrisWhite I'm on a laptop, so on the touchpad

I want to say there's a keyboard shortcut to pop out the side bar too but I don't know it

user54412

because the way I've used windows since ~Vista was <windows key> + <first few letters of program> + <enter>

If you hit the Windows key now, it brings up the Metro interface

Blech

They say "If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, and then click Search."

And moving the mouse to the upper left corner shows you all the apps open (again, just like Gnome/KDE did for me)

Ooo, neat. The mouse in the corner thing works

The Atlanta transportation network is so messed up... petapixel.com/2015/02/02/…

Granted, closing down the interstates anywhere will probably cause problems

But the roads are all gridlocked when the interstate is open. It took me almost 2 hours to go 14 miles home today

user54412

I remember a time when I looked forward to new OS releases with all their nifty new features. Now I find myself dreading them. Each one seems to take another step closer to the bleak future of mobile-only interfaces, where keyboards are a thing of the past.

user54412

I suppose this officially makes me old.

2:38 AM

Now they terrify me because I'm always worried some driver won't work with some hardware and I'll brick my computer for a week trying to sort it out

My lab workstation is a few years without updates. Just because I would be in big, big trouble if I lost data or time trying to update it

Re this question: physics.stackexchange.com/questions/162866/… , I've seen Feynman derive electrostatic forces from photons (with time-and-longtidunial polarizations). Isn't this post the question to that answer?

Suggest reopening.

I much prefer remaining "behind the times" with regards to my OS. That's what I like about SciLinux, it's hella stable

Most of the "new" stuff doesn't work on it, but it doesn't crash

whereas my Ubuntu & Fedora distros crashed weekly due to either some dumb bug or my own fault

We were keeping up with new releases until the software we wanted to use actually worked the way we wanted it

Then we kinda stopped and made sure we didn't use new features that would require newer versions

2 hours later…

5:05 AM

@tpg2114 however, rubber ducks will not get my papers published, whereas the rigourous experimentation has got me published (9 so far). I am sure that a rubber-duck would become a downvote magnet

so, going beyond the 'rubber duck' method, I still have questions.

questions of an experimental nature that is

5:48 AM

1

Q: Kinetic energy of an expanding sphere

In the study of Newtonian stellar structure, Weinberg (1972) writes The uniform dilation of a sphere with uniform density will give it a kinetic energy $$U=\frac{3}{10}M\dot R^2$$ I don't know how to derive this, or even really where to begin. Does one resolve the sphere into particles o...

homework-and-exercises newtonian-mechanics kinematics astrophysics

Food for thought: should that have been closed as off topic for being no-effort homework? Why or why not?

6:02 AM

tpg wow, re atlanta highway shutdown. reminds me of the 2007 "aquateen" boston bomb scare & ofc there have been so many others...

"warning: unattended science prjs will be detonated"....

6:46 AM

49

Q: Alpha-testing a wizard

So over the past few days I've put some of my time into building a wizard. It currently stands as a 515 line user-script. And it's really still just a tech demo. Before we go any further, a screenshot of what you'll see on the Ask page if you install it. If you're just joining us and have no ...

kind of cool

7:05 AM

perhaps I should keep my 'rubber-duck' physics off here. The site is a TP dominated one after all (not a bad thing, but a statement of fact).

6 hours later…

12:54 PM

@DavidZ I have to say that I did not close it only because I was puzzled that that should be the result for a sphere as in "surface of a ball", thinking Weinberg did something very obscure to get that expression.

2 hours later…

2:38 PM

0

A: Why is a new moon not the same as a solar eclipse?

What I want to know is.. the moon rotates the earth on a monthly basis. Where as the earth rotates the sun on a yearly basis. To me, somewhere on earth at nearly all points of time should experience an eclipse... so I am asking for someone who is intelligent in this topic to explain how this cann...

Imperative: Prove there isn't an eclipse happening at every moment somewhere on Earth

Solution: There are moments where we observe no eclipse happening

For instance, there's no eclipse happening now

Is it just me, or was this post perhaps not well thought out?

@Jim HOW DO YOU KNOW THAT?!

Perhaps you are just used to living in perpetual darkness

Hmm, I'm not sure I believe you Jim

Do you have evidence of that?

@ACuriousMind Jim est lux lucis

@KyleKanos The internets?

The internets is your evidence?

List of solar eclipses in the 21st century

During the 21st century, there will be 224 solar eclipses of which 77 will be partial, 72 will be annular, 68 will be total and 7 will be hybrids between total and annular eclipses. Of these, two annular and one total eclipse will be non-central, in the sense that the very center (axis) of the moon's shadow will miss the earth (for more information see gamma). In the 21st century the greatest number of eclipses in one year is four, in 2011, 2029, 2047, 2065, 2076, and 2094. The predictions given here are by Fred Espenak of NASA's Goddard Space Flight Center. So far, the longest duration in which...

List of 21st-century lunar eclipses

There will be 230 lunar eclipses in the 21st century (2001–2100): 87 penumbral, 58 partial and 85 total. Eclipses are listed in sets by lunar years, repeating every 12 months for each node. Ascending node eclipses are given a red background highlight. See also: List of lunar eclipses, List of 20th-century lunar eclipses, and List of 22nd-century lunar eclipses == List of lunar eclipses between 2001 and 2014 == Eclipses from August 1998 are included to complete the first eclipse set. == References == This list was compiled with data calculated by Fred Espenak of NASA's GSFC....

2:44 PM

Wikipedia can be edited by anyone, how can I trust that?

Note to self: Wikipedia = evidence

@KyleKanos If you can't trust the word of random strangers from wikipedia, why would you trust the word of random strangers here?

@Jim Oh, because you're not random and not strange

Only one of those is correct

@KyleKanos Not so sure on the last one

2:47 PM

And to the guy who posted that question, I think I'm a random stranger

Probably

Hopefully

It'd be weird if he knew me really well. Kind of stalkerish

You don't have classmates that you've tried getting on Physics.SE?

I've mentioned it, but never encouraged them to join

I really don't have classmates either

Hmm. I try encouraging mine often. They rarely listen though.

They just don't know what's good for them

2:51 PM

I'm one of 4 cosmologists at my university. One, who's gone now, had a profile here. He answered 4 questions I think, then never showed up again

I know one or two computer scientists who occasionally use SO, but no one who'd come here.

I've wanted to encourage my old supervisor to join, but it's just awkward going to him and saying "Hey, so here's what I wasted a lot of time doing while I was your student. Wanna give it a try?"

2

@ACuriousMind That picture is actually you though?

@Danu Yes, it is. (Note that I made that comment before changing it. ;) )

Ah...

Well, there goes my theory that you were a girl

I guess it was already statistically beyond implausible

Also, I had the diffgeo exam this morning and it was surprisingly easy; I may even have passed ~50% chance

3:05 PM

I hope you are not disappointed :D

always

Passed my algebraic geometry this morning, too. Far easier than I feared

I restate: You guys and your exams

3:59 PM

A classmate is up for a departmental award and asked me about CVs. So now I spent the last 45 minutes updating mine. :/

@ACuriousMind Was this a really algebraic course with reduced commutative rings instead of complex numbers, or something more practically useful?

@ThomasKlimpel It was pure math - an introduction to scheme theory, essentially. Aside from me simply liking math, a distant motivation is to understand the rigorous definition of moduli spaces (generically of bundles over a geometric object, and specifically of principal bundles over manifolds, since the latter appear in gauge theories).

The rings involved weren't necessarily reduced, only commutative, btw.

4:15 PM

Cool stuff. My own knowledge of advanced algebra ends a bit sooner, which is ironic in a certain sense.

Too mean?

Hmm, it seems I forgot that this site was mean to teach people how to "search the internet," and not help them with physics concepts. Silly me. — Kyle Kanos 16 secs ago

@ThomasKlimpel And what certain sense would that be?

7

Q: Can Schwartz-Zippel be formulated for commutative rings instead of fields?

The polynomials which occur in the Schwartz-Zippel lemma could be defined for any commutative ring, yet the lemma is restricted to fields. This makes it inapplicable for $(1+x^n)=1+x^n(\operatorname{mod}n)$ and similar identities, and feels a bit "unnatural" to me. Why can't Lemma (Schwartz, ...

ra.rings-and-algebras polynomials computational-complexity

@KyleKanos If you had written that as a snarky comment to a naive question, I'd say yes, but as a reply to an unhelpful comment on an unhelpful answer I think it is fine.

For the sort of questions I currently try to solve, a good basis knowledge in algebra and category theory would really be useful.

4:22 PM

@ACuriousMind Awesome. Thanks.

But I came more from the "formal logic" side, so I have to cope with my patchy knowledge somehow.

@ThomasKlimpel Probabilistic polynomial identity testing...I hadn't heard of that before

@ACuriousMind: You should start doing some First Post reviews. You do seem to get to a lot of first posts w/o going into the queue.

4:39 PM

@KyleKanos I don't have the patience to wait for a post to turn up in that queue when I think it needs improving.

And the one you probably refer to right now actually was a review from the suggested edit queue

Actually, I think there were like 3 today

(out of 17, that's a high rate!)

In formal logic, you can just write down things, and these things then become the objects which actually exists. But two objects can be identical, even if the symbols which are written down are not identical. But how to test whether two "written down" objects are identical or not...

@ThomasKlimpel Well, that occurs in abstract algebra all the time, doesn't it? In fact, determining the isomorphism classes of certain kinds of objects is what a very large part of celebrated theorems are about

@KyleKanos I stopped reviewing the FP queue a while ago, actually, because I felt that I clicked No action needed quite a lot when I really meant There's stuff bothering me about this, but I'm too lazy to fix it now.

Isn't there a "skip" button?

Yes, there is. But going through a queue and ending up skipping most of it also feels weird.

@ThomasKlimpel: Wouldn't the problem to decide whether two formulae are equivalent be the same kind of problem in formal logic?

Totally unrelated: What are prolate and oblate shapes? The German translation for both seems to be "flattened", which is not really helpful in distinguishing the two.

4:55 PM

Prolate is squished at the equator

Oblate is squished at the poles

user image

Ah, so the words only make sense if there's a distinguished axis to begin with?

(else you have no "poles")

Yes

@ACuriousMind If the two formula are actually equivalent, then writing down a formal proof that they are equivalent is a typical problem in formal logic. But if they are different, then giving a concrete counterexample is the way to go. But can you guess counterexamples with a guaranteed high rate of success? Probabilistic polynomial identity testing shows that sometimes you can...

@ThomasKlimpel I see. That's kinda cool

LOL

Here, OP mistakenly included general-relativity

And JohnRennie used his golden hammer to close it

5:09 PM

...which allowed John Rennie to use the dupe hammer.

Which is weird because I removed it in my edits

But whatever

@KyleKanos The dupe hammer rights, as well as the tags that count for the breakdown in the tags section of the profile, pertain to the original tag of a question to prevent people from editing in the tag they either have or want a gold badge in

Well that makes sense

I had actually kinda wondered about how tag vote things were computed

Like if it was tagged X, Y, & Z when you answered it and accrued some upvotes, if someone else came along and swapped Z for W, do new votes count towards W

But, given your description, it seems not

<removed>

user image

Sigh Apparently I had my do-loop skip the whole i direction

do i=1,mb(1,1),mb(1,2) instead of do i=mb(1,1),mb(1,2)

where mb is the array bounds....

I've been wondering why on earth my emission map hasn't been appearing in the output

5:26 PM

@KyleKanos ¯_(ツ)_/¯

Well I found the answer. And it was my error in writing the code

So while I should have had something to show my advisor yesterday, I didn't

So now I'll have to see if he'll be in later this afternoon

6:06 PM

Hi there

I have a question guys .... can I ask?!

Feel free to ask it. If someone knows the answer, they can respond

Im working on a problem. I know the theory but I cant understand why it happens?!

when we place a non-ferromagnetic disk in a magnetic field it will be repelled.

like an aluminum disk that repels in magnetic field of a coil by applying AC current to it.

I dont know why it repels?! Aluminum is paramagnetic it should be absorb to the field.... but Mr.John Rennie said This is because the oscillating field induces eddy currents in the conductor and the eddy currents in turn generate a magnetic field that repels the original field.

6:32 PM

@FarinazTalebi i am no expert, but i think it has to do with the alternating current and field, if say it was a static material or if a DC current is passing through i think it shouldn't repel.

@Gowtham yeah it just repels in the field of AC current. but I dont know why?!?!?

@FarinazTalebi you are already familiar with EM Induction and Lenz's law ?

@Gowtham yes, I read about it

the key here is you should see Al as a conductor than paramagnetic material, an eddy current is setup in Al by varying magnetic field produced by the Alternating current. what is your confusion

6:48 PM

u mean that when we have AC current our field will change in a period.... so our induction filed will change. what happens here that causes repulsion?!

@MarkMitchison and how helpful r u?

the induced eddy current produces a magnetic field of its own , and the eddy current's direction is always such that it will oppose the change which produced it. this is just lenz law. you may find this link helpful.

@MarkMitchison If I have questions, I ask them...what else do i do? I asked my question... but it got closed...so now what do I do? Plus, u know what I was asking @alarge , To make sure I got it right... I wrote of the two-site hamiltonian and then asked @alarge ..who is ignoring me.. I am trying to do it myself but because this community won't help me, I then ask for more help and start annoying everybody, etc.

@MarkMitchison I can't solve this problem in this community as the community can't help me and get annoyed with me... U know why I came here in the first place? because I wanted help on this very problem, modelling quantum mechanics in plants...But I found barely any help...Therefore I am going to ask my quantum mechanics friend for help.. bye bye to you guys!

@vzn thanks for the help.. and thanks @ThomasKlimpel too!

@FarinazTalebi is it more clear now ?

@TAbraham Mark & I have both stated similar things: every time you get stuck on one thing, you are asking for help. If you truly want to learn & master this, you ought to get used to be frustrated over solving the problem (it happens to us all)

7:00 PM

@vzn @ThomasKlimpel thanks for recommending those programs.. currently I think that's the way to go... Bye!

We are not a solving committee who will do the hard calculations that you can't/won't do. We can direct you to the more simple problems you should do to understand how to do the harder problem

6

@SabreTooth for the record, this is not meant to be a theoretically dominated site. We would always like to get more of a balance between theory and experiment (although not by allowing all sorts of random "how do I build X"-type questions from laypeople).

@DavidZ did you reply to the wrong person ? :P

@Gowtham Haha, I was trying to decipher what David wanted to tell me with that, too :D

I think it's supposed to be for @SabreTooth, in reference to his comment just above @ACuriousMind's...

7:09 PM

physics.stackexchange.com/review/suggested-edits/72134

Who is Vince?

IDK

McMahon probably

Vincent Kennedy "Vince" McMahon (born August 24, 1945) is an American professional wrestling promoter, former announcer, commentator, film producer, actor and occasional professional wrestler currently serving as majority owner, Chairman and CEO of Stamford, Connecticut-based professional wrestling promotion World Wrestling Entertainment (WWE). After acquiring the assets of World Championship Wrestling (WCW) and Extreme Championship Wrestling (ECW) in 2001 and 2003 respectively, McMahon's WWE became the sole remaining major American professional wrestling promotion (prior to the national expansion...

LOL

7:32 PM

@TAbraham You said: "you know, people have lives.. I don't spend every hour of my life to figure out what it means...", at which point I quite simply chose to click the ignore button so I would not get pinged by you any longer (or see your messages for that matter). Why? Because this message clearly signalled to me that you had no intention of putting any effort in. You also seem to have misconceptions about your own skill level.

As an example which I think summarizes well the many problems, consider this. You had said that you understood Pauli operators, but when MarkMitchinson asked you to write down the Hamiltonian in 4x4 matrix form, you immediately asked MM to do it for you.

Earlier, Kyle Kanos told you that if you at first do not succeed in solving your problem, try again. I am, instead, asking you to try even that one time before asking for help. In fact, I don't think you can really understand the given advice if you haven't had a go at it.

Ah, finally something broke! :D

grabs popcorn

Well since person A isn't here, there isn't much to watch and chomp on popcorn

chomping intensifies

Also, I'm pretty sure that popcorn is only good if you're watching a movie

Nah, popcorn is always awesome

7:40 PM

CHOMPING INTENSIFIES

I don't like popcorn.

CHOMP CHOMP CHOMP

I eat chocolate/sweets at the movie theatre.

I try to avoid popcorn, actually

I do love it

That's just, like... your opinion man...

7:41 PM

but it's not on the diet

^Same here

@Gowtham whoops, yes I did. I should pay more attention.

sorry @ACuriousMind

@DavidZ No problemo

You humans and your need to eat food. It's a weakness of your kind, really

2

I think Aubrey de Grey said something to the effect that it's the eating that kills you.

7:44 PM

We have not yet breached the real issue - salty or sweet?

Which one is buttery?

@KyleKanos Salty

Okay, then definitely salty

@alarge Unfortunately, not eating also kills you.

@ACuriousMind Maybe with that attitude

7:48 PM

@ACuriousMind Indeed, I think that was his next sentence in his talk. But it was several months ago that I watched it, so I might be wrong.

@TAbraham I'm sorry you don't appreciate the considerable amount of time I spent trying to help you. By the way, I didn't have any help at all when I worked this stuff out for the first time. I am no Einstein, I just have a little determination. I read stuff, tried calculations, got everything wrong the first three times, and then eventually I learned something. Everybody else here went through the same process. Frankly, you don't deserve to learn anything until you are willing to do the same.

I just love talking to myself.

@MarkMitchison You're your own rubber duck, then? ;)

@MarkMitchison Fourth time's the charm?

@MarkMitchison On that note, why does Physics.SE require a show of effort? I was thinking about this as I was writing my own message.

@ACuriousMind What does that mean?

@Jim Nth time, more like

@alarge Well, I require a show of effort, because it's unbelievably annoying trying to help someone who refuses to try things out. Especially because we all know it is impossible to even understand a physics problem until you try solving it. In fact you stated this in your response much more eloquently.

7:51 PM

5

Q: What is the meaning of **effort** that Phys.SE wants in homework questions?

Always do I have seen most of the homework tagged questions are hold, with a close reason to show minimal effort. I thought Phys.SE wanted the asker to show his attempt. But recently, I got amazed when my homework-tagged question was put on hold by a moderator (I am not disrespecting him!). For w...

discussion closed-questions homework close-reasons

@DavidZ I realise the site is not meant to be theoretical dominated, but that is the way the site has developed. It is not particularly encouraging to not have any credible answers on the questions. The cynical part of my brain says that the experimental questions are brushed off as beig 'lesser' - which of course is nonsense.

@MarkMitchison Oh, tpg2114 just introduced the notion of rubber duck physics a bit ago here. We already know dmckee uses professors as ducks.

@alarge And I suppose it makes sense to make this an SE-wide requirement, since most people who have managed to learn stuff will be similarly annoyed by people like that.

@MarkMitchison math.SE seems to disagree (or at least put the bar very low)

@SabreTooth Could it be that theoretical questions are just easier to answer in this format? That's a serious question. I honestly wouldn't know

7:53 PM

@ACuriousMind I think talking to a rubber duck would be more rewarding, frankly.

The final straw of discouragement (for want of a far better term), was the non-answer joke of an answer I received on the recent question - the answer did not help at all, was mocking the question, but was a source of amusement of several more members.

@SabreTooth Sounds like something I'd do after a long day at work. Was it me?

@Jim No, it was CuriousOne.

^no affliation to me, emphatically

4

A: Microtops sunphotometer sun target optics

The basic instrument design is described in the manual: http://solarlight.com/wp-content/uploads/2014/05/MTPMAN-RevC.pdf. An optical collimator is basically just a lens in a cylindrical borehole. The alignment of the lenses and boreholes is crucial for the precision of the instrument. The precisi...

7:55 PM

but as mentioned, as an irony I guess, I have figured it out and will be testing it soon

@ACuriousMind Perhaps this is less of an issue in mathematics... although it seems that the problem-solving structure and requirements should be the same.

Nevertheless, the Physics policy accords with my own views on the matter, so I am happy to promote it!

@SabreTooth poooossssstt annnn annnnsssssssweerrrrrr

@MarkMitchison Well I suppose the natural follow-up is "why do you get annoyed"? Isn't it a bit elitist or arrogant to think that someone doesn't deserve to get an answer if they don't show effort? Do note that I am not criticizing you, or in fact anyone as I agree with the policy of showing effort, but I do sometimes wonder why that is.

@MarkMitchison Although I am very interested in pure math, I do not participate on math.SE because it is absolutely swamped with "How do I solve this quadratic equation?"-style questions that seem to never have heard of completing the square, or the existence of a formula for the solutions.

@KyleKanos very funnnnnnnnnnnny

7:57 PM

@SabreTooth He was serious. If you figured out how it works, post your own answer to the question. It will improve the value of the post

It is very difficult to find something interesting in the flood of poor questions there

I am serious about that

@Jim I think they are, because every experimental setup is a bit different, and it is more difficult to describe the setup properly than to write down some equations.

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