The h Bar

GPhys

05:04

if I get into Penn, I could end up teaching @BernardMeurer in a lab haha

Sir Cumference

@ChrisWhite I don't know how you got it down to 73KB, but I can barely make a dent in the file size

Indexed mode doesn't seem to do much. I've also been compressing it in 8-bit, by the way

user54412

05:37

@SirCumference 8 bits per pixel or 8 bits per channel (i.e. 24 or 32 bits per pixel)?

user54412

there's only 75k pixels, so if it really was 8-bit indexed, it would be 73 kB

Sir Cumference

@ChrisWhite 8 bits per channel

Oh...

Ya meant bits per pixel...

0celo7

Sturdy is such a bullshit ability

Screw you Game Freak for making it a thing

Sir Cumference

@ChrisWhite This might sound like an idiotic question, but how do I set BPP?

0celo7

@SirCumference What?

Sir Cumference

05:47

Crap

I'm tired...

Bernard Meurer

@GPhys Poor you

user54412

@SirCumference No idea. Like I said, most image software is terrible on this point.

Sir Cumference

.-.

So, er...I'm out of luck?

0celo7

that's life

Sir Cumference

Fun...

Bernard Meurer

05:48

@0celo7 brand new linux running

less than 600MB of used ram

0celo7

Currently using 12.88GB

Sir Cumference

Well beyond photoshop, what else could I work with?

Bernard Meurer

GIMP

Sir Cumference

GIMP sucks

Bernard Meurer

Say what brother?

fite me irl

free software bitch

GNU

Sir Cumference

05:50

Hence it's the poor man's version

0celo7

Don't fight him!

He has such a pretty face

Sir Cumference

Er...Me?

0celo7

No, your mother

Sir Cumference

Thanks?

Bernard Meurer

@SirCumference Saying free software is 'poor man's version' is pure ignorance and nothing else

Sir Cumference

05:51

If ya mean it nonsexually

0celo7

What the hell are you talking about

Sir Cumference

It's from experience, Bernard

Bernard Meurer

I suggest you do your research on GNU, GPL and so on

Sir Cumference

I've used GIMP for 3 years

Bernard Meurer

@SirCumference saying it's bad it's one thing

Sir Cumference

05:51

It doesn't really fare well against PS

Bernard Meurer

Saying it's a 'poor man's version' is a much worse statement

because it implies that it's being free has something to do on it's quality

Sir Cumference

I don't support piracy (looks around for NSA), but Photoshop can be downloaded for free

0celo7

Pretty sure NSA doesn't give a shit about piracy.

Bernard Meurer

being freeware and being free software are two different things

one again, read on the Free Software Foundation

Sir Cumference

I know this. It was meant as a joke.

0celo7

05:53

@SirCumference They do care about stupid jokes.

Bernard Meurer

gnu.org/philosophy/free-sw.en.html

Sir Cumference

@0celo7 Dang, guess imma change my name

@BernardMeurer I've messed around with other photo editing softwares. I know GIMP's a good free alternative

It's not PS level though

Using it instead of PS would be a downgrade

Bernard Meurer

Nope, because it lacks contributors from the community

Make it better if you think it's not good enough, that's what Open Source is all about

Sir Cumference

All right, lemme ask the big question then

0celo7

NO

I will not marry you

Sir Cumference

05:56

Does it already have BPP (bits per pixel) configurations

@0celo7 You monster, leaving me with the children

0celo7

Protip: they're not yours.

Sir Cumference

D:

@BernardMeurer PS doesn't seem to have any. Using GIMP wouldn't help unless I can fix my ad

Bernard Meurer

@SirCumference Is this what you are referring to?

Sir Cumference

That's bits per channel. PS has that

8 bits per channel = 28 bits per pixel

Bernard Meurer

I thought BPP was a result of color depth

Sir Cumference

05:57

I can't figure out how to change BPP

Bernard Meurer

well if 8 BPC = 28 BPP

Sir Cumference

It's long and complicated

Bernard Meurer

you can change BPC and that's cause BPP to change

Sir Cumference

@BernardMeurer I can't figure out the ratio though. 16 BPC = 48 BPP

Ah whatever, I'll leave the ads as they are

user54412

@BernardMeurer Indexed mode is one channel (you define your own color space). But most software doesn't know about it and uses RGB or equivalent at 3 channels.

Sir Cumference

06:00

I've got a test tomorrow and I can't sleep...

@ChrisWhite Dude, if PS isn't gonna cut it, what'll I have to get?

The program costs like $10/month

user54412

write your own codec?

Sir Cumference

I don't have the skills for that

I can write in HTML5 and JS.

Crap

Wrong chat

Bernard Meurer

@ChrisWhite I get you

Sir Cumference

06:27

Howdy

Sidarth

07:34

@SirCumference partner.

yuggib

08:04

@ACuriousMind You take the derivative wrt the number ($L$ I think in your notation) on a suitable dense domain, and then solve the differential equation (i.e. re-exponentiate)...in the case of the position and derivative is possible and easy, in general the zassenhaus is plainly wrong (a zillion of domain problems)

Physics Meta

09:02

0

Q: Should we add a notify/follow a question feature?

I have come across many questions that I want to know answer of to. But All I do is favourite the question. So I want to make a suggestion to the community to add a feature that would notify me about any new answers added to the questions. So that I don't have to check the question every day from...

feature-request

Valentin Tihomirov

11:34

Why does he tell that \sum(Ai iA) = 1 in hermitian basis?

I do not see which equations which tell me how to deal with combination iAi.

Danu

physics.stackexchange.com/review/late-answers/119850

Is this flagable?

Valentin Tihomirov

I do not understand even how can you pull iAi from the first A. I understand that Ai is a dot-product which gives us a simple number. Same is iA. But what is A times iAi?

Danu

You should use bra-ket notation. Note that mathjax also works in chat if you enable "chatjax" (see top right of this page for information about it).

Valentin Tihomirov

Ok, |i><Ai> is a component of A in the direction of basis vector i. But what is <A| times |i><Ai>?

Danu

$\mid i \rangle \langle A \mid i \rangle$ is indeed the component of $A$ in the $i$-direction.

Now, sum over all possible $i$. What is the result?

Valentin Tihomirov

11:45

That is vector A, I see now. I just had difficulty with the fact that you can pull <A| as a coefficient in front of the sum sign.

Danu

$\langle A \mid$ does not depend on $i$, so why should it not be allowed?

Fred Kline

13:31

The reason my body is sagging is because I'm surfing the crest of a gravity wave.

user685252

ba dum tss

:)

Physics Meta

0

Q: There is a subtle bug in the (first post) review queue(s?): The (up to recently) normally greyed-out options are no longer greyed out

The title says it all, really. Normally, when one hasn't done anything the "I'm done" option in the First Post review queue is greyed-out. Now, it is no longer so, but one still cannot click it. Similarly, after having done something, the "No Action Needed" button is not greyed-out, yet unclickab...

bug design review-tools

John Duffield

14:01

@DanielSank I think of waves interacting with waves. You can imagine this in the ocean, where a little wave rides over a big wave. Its path changes on the way up, and changes back on the way down. Then it continues on its way and you might think there was no interaction. But there was. A wave makes a wave change path.

Secret

14:28

https://www.sciencedaily.com/releases/2016/02/160211185926.htm

Despite both subject of study being simialr because they are both nonlinear, it does wodner me why these analogues actually helped in understanding black holes

ACuriousMind

14:51

-2

Q: Virtual object real image

Under what condition a concave mirror form real image of a virtual object? Fuck stackexchange what more shall I type

reflection

What is going on in the head of someone who thinks "Gee, yes, typing 'Fuck stackexchange what more shall I type' will certainly let me get the answers I want"?

ACuriousMind

Also, why was this migrated here:

0

Q: Relationship between Lippmann-Schwinger integrals of different dimensions

Define $G_n (\mathbf{x},\mathbf{x}')$ as $$ G_n (\mathbf{x},\mathbf{x}') = \lim_{\epsilon \to 0^{+}} \left[\dfrac{1}{(2 \pi \hbar)^{n}} \int_{\mathbb{R}^{n}} \mathrm{d}^{n}\mathbf{p} \dfrac{e^{i \mathbf{p} \cdot (\mathbf{x}-\mathbf{x'}) / \hbar}}{p^{2}-\hbar^{2} k^{2} - i \epsilon}\right]. $$ D...

integration quantum-mechanics

0celo7

@ACuriousMind He's frustrated

ACuriousMind

I'd rather migrate that to math because it's really just about the properties of that integral (and it doesn't even explain the physical meaning of the integral), and they migrate it here because "Lippmann-Schwinger" are physicists??

0celo7

@ACuriousMind math touched by physicists is impure

ACuriousMind

It even was a unilateral migration by a mod.

0celo7

14:56

Haha

ACuriousMind

I'm only on for about half an hour and I already have had enough :D

0celo7

@ACuriousMind We could discuss least common multiples...

ACuriousMind

15:49

12

Q: Where does gravity get its energy from?

I would like to know where gravity gets its energy to attract physical bodies? I know that the law of conservation states that total energy of an isolated system cannot change. So gravity has to be getting its energy from somewhere, or else things like hydropower plants wouldn't be able to turn ...

gravity energy

Bounty reason: "The current answer(s) are out-of-date and require revision given recent changes."

Wat.

Either I'm unusually grumpy today or this site is not making a lot of sense right now :P

Secret

Those who are interested in the more serious aspect of the coffee machien joke can look into the main PSE site

http://physics.stackexchange.com/questions/221274/quantum-joke-not-a-real-joke-not-a-riddle

Well, + or - depends on whether the coffee machine is a fermion or boson. But for such a many particle system, Iwill not view it by counting the number of fermions that compose it

0celo7

16:21

@ACuriousMind You've been unusually grumpy for a while now...

user116211

16:33

@ACuriousMind Probably he is too literate to understand physics . He is probably fascinated by Gravitational Waves!! So called LAYMAN ;/

user116211

-3

Q: Conceptual Change thinking needed

Using Conceptual Change Research To Reason About Curriculum By Glenn D. Berkheimer, Charles W. Anderson, and Steven T. Spees Introduction The kinetic molecular theory is fundamental to the understanding of most of modern science. Feynman recognized this when he said: If, in some cataclysm, al...

field-theory

user116211

What do you expect from him?

0celo7

Energizer777

1 6

newtonian-mechanics energy kinematics electromagnetism homework-and-exercises classical-mechanics acceleration

That's a long "temporary suspension"

ACuriousMind

@0celo7 All suspensions are temporary.

0celo7

@ACuriousMind Wait, is this the sockpuppet guy?

user116211

16:35

@0celo7 No.

ACuriousMind

@0celo7 How would I know?

(If I knew, I would probably not be allowed to tell, and if I don't know for sure, it would be irresponsible to speculate. Discussing the reasons for suspensions is generally a bad idea)

0celo7

Hmm.

ACuriousMind

@user36790 That doesn't make much sense to me either, and using "It's a layperson" as a reason is an insult to laypersons.

0celo7

@ACuriousMind How do you feel about salsa on eggs?

ACuriousMind

...what.

0celo7

16:39

@ACuriousMind Do you know what salsa is?

(Yes, I abruptly changed the topic.)

ACuriousMind

Yes. I've never encountered that strange combination, though

0celo7

@ACuriousMind Strange??

Oh you poor German child...

ACuriousMind

When you say "on eggs", how is the egg done?

0celo7

google.com/…

Scrambled, omelet.

Not boiled/poached.

ACuriousMind

Hm, okay, scrambled I can imagine

0celo7

16:41

It's very common in the US.

Slereah

I should go back to that CTC book I was working on

0celo7

@Slereah Do it.

ACuriousMind

But salsa is generally not really eaten here outside of Spanish cuisine

0celo7

@ACuriousMind Well...same here, I think. Except for eggs, that is.

ACuriousMind

I think I've seen people eat eggs+ketchup, though

0celo7

16:42

@ACuriousMind Yes, I think that may be a German thing.

dmckee

@0celo7 Suspensions lengths escalate over repeated offenses. The baseline schedule (built into the stack exchange software is) is 7 days, 30, days, 365 days and repeat.

On Physics we often introduce a 1 days suspension before the 7 days for users who look like they ought to be good contributors and we have issued a 2 or 3 month suspension between the 1 month and 1 year one in some cases as well.

I, of course, can't say anything about the case in front of us.

Slereah

who are we banning

I say let's ban everyone!

ACuriousMind

@Slereah But...who bans the last account?

Can mods ban themselves?

Slereah

You ban yourself

0celo7

@dmckee Try to ban another mod -- let's see what happens.

dmckee

16:45

@ACuriousMind I'm almost temped to try it.

@0celo7 Why would I give one of those other guys a day off when I could give one to myself?

0celo7

One of my shoes is making this strange clicking noise when I walk, almost like it's sticking to the floor.

There's no gum on it AFAICS.

Any ideas?

HDE 226868

Banning yourself is possible-ish.

user116211

11

Q: How to stop shoes from squeaking on hard floors?

I have a pair of pretty nice shoes that I love, except when I'm going to work! We have hard linoleum-style flooring in most places, and carpet only in the office area where I work. When I have to go to another area, my shoes squeak very loudly. I have tried other sources of information for this...

shoes

0celo7

Not squeaking.

It makes the noise on all surfaces.

It sounds like it's sticking and then breaks free

user116211

@0celo7 The shoe is farting then :D

user116211

16:54

-2

Q: Theoretical Astrophysics accomplishments or Physics Popularity contest winners?

Many of the recent accomplishments in Theoretical Physics are based data creating a theory, instead of the creation of a theory, and observation proving the theory. Has technology gotten ahead of scientific thought and the proving of those thoughts? Do we have simply too much to explain? Does aca...

field-theory

user116211

^ What the hell is this?

sharaf zaman

hello

any astronomy lover

Bernard Meurer

@sharafzaman Are you looking for a lover or an expert?

sharaf zaman

experts are lovers

dmckee

Most of us like astronomy at one level or another. There is also a Astronomy site.

sharaf zaman

16:58

oh!!!

dmckee

@sharafzaman But not all lovers are experts.

user116211

Hi! @JohnDuffield.

sharaf zaman

yeah that's true

Slereah

Do not call out to He Who Shall Not Be Named!!!

dmckee

explosm.net/comics/3557

user116211

17:00

@Slereah Time pass :)

user116211

@0celo7: What kind of shoes are you wearing?

Bernard Meurer

@sharafzaman I asked because I do like it, although I'm probably not fit to explain most things about it

sharaf zaman

k my question appears

@BernardMeurer If an object is moving close to blackhole it has very high velocity!
agree!!! ????

question not over

0celo7

@user36790 Some Polo shit. I don't know what they're actually called

Bernard Meurer

@sharafzaman Please don't abuse punctuation, it looks weird

sharaf zaman

17:04

k

Bernard Meurer

But I guess it could have very high speed, yeah

user116211

@0celo7 it sticks on the surface- on all surfaces for some time, right?

sharaf zaman

okay, it has very high speed,
Then it means according to relativity it has very huge mass, agree

0celo7

@user36790 I have an idea...give me 15 to get back home and try it.

user116211

@0celo7 Meanwhile enjoy this:

user116211

17:06

Shoes glued to the floor prank

►

dmckee

@sharafzaman No. See ...

23

Q: Why is there a controversy on whether mass increases with speed?

Some people say that mass increases with speed, some people say that the mass of an object is independent of its speed. I understand how some (though not many) things in physics are a matter of interpretation based on one's definitions. But I can't get my head around how both can be 'true' is an...

special-relativity mass speed mass-energy

That approach will consistently lead you astray which is exactly where you are headed.

You're about to suggest that that makes it into it's own black hole which is simply wrong. Give me a minute to find the question on that too.

26

Q: If a 1kg mass was accelerated close to the speed of light would it turn into a black hole?

I'm a big fan of the podcast Astronomy Cast and a while back I was listening to a Q&A episode they did. A listener sent in a question that I found fascinating and have been wondering about ever since. From the show transcript: Arunus Gidgowdusk from Lithuania asks: "If you took a one kilog...

black-holes speed-of-light relativity mass-energy

0celo7

@user36790 Plan failed.

I wanted to see if I could get a piece of paper to stick to the sticky spot

user116211

@0celo7 Did it stick?

sharaf zaman

then will its mass increase or not

0celo7

@user36790 No, it failed

user116211

17:14

@0celo7 The shoe is sticky but actually it is not sticky??

user116211

The shoes are haunted!!

dmckee

@sharafzaman There is a thing that increases. In very old fashioned and misleading language that is called "relativistic mass". There is also the right way to define mass, which is invariant under Lorentz boosts (changes in speed).

Most pop-sci treatment use the old language, which then leads the people who try to really understand it into believing things that are obviously not the case if you use a good definition of mass.

It's not that you can't do physics with the old language, but you'll make a lot of mistakes while trying to learn to do it that way. Learn it the right way and you'll get to a deep understanding faster and with few falls along the road.

DanielSank

@JohnDuffield And why are you so certain this this mental metaphor of Nature is superior to the one involving virtual particles?

sharaf zaman

okay then what is correct definition of mass

0celo7

@user36790 listen youtube.com/watch?v=HRxm0bHzmro&feature=youtu.be

dmckee

17:18

If you want a resource to start learning relativity the right way consider amazon.com/Illustrated-Guide-Relativity-Tatsu-Takeuchi/dp/…

0celo7

The other shoe does not make that noise.

dmckee

@sharafzaman The square of the object momentum 4-vector. It corresponds to what is called the "rest mass" in the old language. And it doesn't change.

0celo7

@dmckee How do you define the momentum without mass?

sharaf zaman

yeah! that was next

dmckee

In terms of Newton's 2nd and 3rd law, of course.

And at low relative speed.

0celo7

17:22

@dmckee Let me know when you can measure a force 4-vector

dmckee

In that case when two otherwise isolated bodies interact the ratio of their changes in velocity is the inverse of the ratio of their masses. It leaves you needing to define a mass unit, but that's unavoidable.

0celo7

Hmm, well, maybe you only need the spatial part.

Sir Cumference

Oh my god

dmckee

All physics has the bootstrap problem and the answer is and always has been to bootstrap from simple approximations.

The more rigorous you try to make physics the more self-consistent it becomes but also the more divorced from every-day, hands-on knowledge. We got from the latter to the former in small steps that were justified because they worked.

That's how you know it is science rather than math or philosophy.

Slereah

Revenge of the Nerds Talent Show

►

0celo7

17:25

@dmckee Dr. Physics, please figure out my shoe problem

@Slereah o.o

dmckee

Letting students puzzle over things is important to their development. I'm doing you a favor by leaving it in your hands.

0celo7

@dmckee Oh c'mon, the shoes are unwearable

dmckee

But that's not my problem. I have grading to do.

sharaf zaman

i think the man exerts some muscular(considered external) force and there was no other force to balance it.
am i right?

hey>

0celo7

@dmckee hmm, so you're doing yourself a favor

nothing wrong with that, but you're not doing me a favor

dmckee

17:30

@0celo7 That doesn't preclude doing you one as well.

ACuriousMind

@0celo7 Doing grading instead of something else is not doing oneself a favor.

sharaf zaman

k anyone say the answer for that problem

0celo7

@ACuriousMind grading is fun

I could grade his stuff and he fixes my shoe

ACuriousMind

Ahahahahahahahahahahahahhahaha...no.

0celo7

@ACuriousMind What?

ACuriousMind

17:32

@sharafzaman What problem?

@0celo7 "grading is fun"

sharaf zaman

that shoe problem

0celo7

> Can anyone explain why Euclid's Lemma holds? The proof makes sense. (Multiply the linear combination by b then apply the basic lemma etc etc.) However, I am trying to think of a reason why it holds. I would have a hard time explaining to someone why Euclid's lemma holds even with showing the proof.

What?

ACuriousMind

@0celo7 Some people are under the strange impression that "proof" and "reason why something is true" are two separate things. The former is what they have to do because the math book says so, the latter is what convinces them it is true.

0celo7

@ACuriousMind Well, the prof wrote this:

sharaf zaman

i had a doubt in fluid mechanics

ACuriousMind

17:36

It's pretty hard to get them out of that mindset because it means they don't really accept logic - so showing them this is a illogical position doesn't do anything

0celo7

@ACuriousMind I think the student just didn't understand the idea behind the proof.

sharaf zaman

even i am a student

ACuriousMind

@0celo7 Then asking for a "reason why it holds" is really bad phrasing for that

sharaf zaman

but y?

ACuriousMind

If that's what they meant, the prof's answer should be fine, though

sharaf zaman

17:39

hey! i had a question in fluids

ACuriousMind

@sharafzaman You said so already.

What do you expect anyone to do without actually asking the question?

0celo7

@ACuriousMind He wants someone to say it's OK to ask the question.

Bernard Meurer

@ACuriousMind Maybe he's into guessing games

dmckee

@0celo7 The worst that might happen is that no one answers him.

Bernard Meurer

I have found our new god
https://i.imgur.com/sza5NoV.png

sharaf zaman

17:42

lol! k my question
if we have a tube U shaped and water level is initially same in both, then when i push it on one side and leave why does it come back though its weight is balanced by normal reaction

DanielSank

@BernardMeurer ಠ_ಠ

Bernard Meurer

@DanielSank Isn't that thing bloody amazing?

DanielSank

@sharafzaman Air pressure depends on how far off the ground you are.

That's it.

0celo7

@BernardMeurer Welcome to 2011

DanielSank

@BernardMeurer Well, it's funny anyway. "Amazing" is a bit strong. I do not feel amazed.

sharaf zaman

17:43

forget air! then also it will come back

Bernard Meurer

@DanielSank I'm easily surprised

@0celo7 the shirt

0celo7

@dmckee I know.

DanielSank

@0celo7 You should be a professional jerk.

ACuriousMind

@sharafzaman You do know that the pressure that the bottom of a liquid is proportional to the height of the liquid, right?

DanielSank

^ That too

0celo7

17:44

But the way I was raised, you ask if you can ask a question before you ask it.

sharaf zaman

yes!

Bernard Meurer

@DanielSank He almost is, except no one can bear employ him

DanielSank

@sharafzaman Draw a free body diagram.

ACuriousMind

@DanielSank The Association of Jerks refused to licence him

0celo7

@DanielSank Why?

Oh screw all of you

DanielSank

17:45

@0celo7 Well, you'd get money?

0celo7

@DanielSank How so?

sharaf zaman

thats my question how to draw for a liquid i am confused

0celo7

I'm not a jerk.

DanielSank

@sharafzaman Well, the bit of liquid at the very top has two forces on it:

1) Gravity, i.e. its own weight.
2) Pressure from liquid below it.

sharaf zaman

okay

DanielSank

17:46

However, liquid at the middle has three forces:
1) Its weight.
2) Pressure from above
3) Pressure from below

Give it a shot now. You'll get it.

It's very instructive to first understand why the liquid in a cylinder doesn't move.

In other words, draw the free body diagram for bits of water in your cup.

You will find that in order for the water to stay still, there must be more pressure at the bottom than on the top.

sharaf zaman

oh!! i got it.

DanielSank

In fact, if you ignore air, then the pressure at any level in the water is exactly right to support the weight of all water above that level.

@sharafzaman Good :D

ACuriousMind

@0celo7 It's perfectly acceptable to go "Excuse me, <question>".

Bernard Meurer

@ACuriousMind abuse

0celo7

^

ACuriousMind

17:51

@BernardMeurer Huh?

0celo7

@ACuriousMind what don't you understand

ACuriousMind

@0celo7 How that word is related to my statement, i.e. what he wants to say

0celo7

@ACuriousMind he wants to say it's abuse

sharaf zaman

if i keep a stone at place of earth with zero orbital velocity what will happen

ACuriousMind

@0celo7 Which is a strange way of phrasing that it is unacceptable behaviour to him?

0celo7

17:55

@ACuriousMind mb

Bernard Meurer

@ACuriousMind Now you are just being sexist

ACuriousMind

Okay, no one is making sense today.

0celo7

@BernardMeurer remember the shirt

sharaf zaman

are here everyone 20+

Bernard Meurer

@0celo7 The shirt indeed

@sharafzaman far from it, faaaar from it

0celo7

17:56

@ACuriousMind I have to solve $kr^2-V_0r+\lambda=0$, please help

ACuriousMind

I'm 30-.

sharaf zaman

:o

Bernard Meurer

@ACuriousMind studied physics in stone tablets so old he is

he wrote the very first lambda

sharaf zaman

its very hard to write syntax of stackexchange

ACuriousMind

@0celo7 You have an amazing confidence in my patience and good nature.

0celo7

17:59

@ACuriousMind what do you mean

user116211

@0celo7: Saw the clip. Hmm... it's pretty weird.

sharaf zaman

answer my question!

2

ACuriousMind

Make me!

Bernard Meurer

@sharafzaman Someone will if they want to, don't scream at people

In Brazil it will get you instantly shot at

user116211

@sharafzaman 20-

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