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12:03 AM
Anyone have any ideas for my question above?
 
12:15 AM
i'm reading now about the Bragg-Kleeman rule: $\frac{R_1}{R_2}=\frac{\rho_2\sqrt{A_1}}{\rho_1\sqrt{A_2}}$ and it lists $R$ as "range" - of what?
the distance the particle travels?
 
12:46 AM
@heather it's Saturday night, go do something fun
 
1:29 AM
does anybody here knows Induction Coupled Plasma or
Induction Coupled Plasma Spectroscopy?
 
1:42 AM
@Sweeper Funny you should ask that, I was just about to ask if anyone here knows anything about PVD systems, I know just enough about induction plasma to be deemed "incompetent"
My only attempt ended in failure and misery, but I blame that on my test equipment
@Sweeper What are you trying to do?
 
2:04 AM
@0celo7 I am...
physics = fun
7
we did go out for pizza - that was nice.
 
2:24 AM
@Sweeper, out of curiosity, what's your question (I probably/definitely won't be able to answer)
 
@heather I'm standing in line for popcorn
 
Giskard42 I am trying to turn small amount of gases into plasma,but stationary gases at atmosferic pressure,becose Induction Coupled Plasma is specific term that means certain industrial process that use flowing,low pressure and high volume gas
I have three big questions 1. Why does the Induction Coupled Plasma use RF freqency? I saw numbers between 13mhz up to 40mhz! There must be good reason for that becose 40mhz electronics at power like 1000 watt is much more expensive than 60hz Induction Heating of steel for example
 
@loltospoon That piece of information is suppose to be taken in combination with the knowledge that the zero of potential energy is set at infinite remove.
 
2. Why do electrodeless lamps use PHOTONS and not AC magnetic field to ionise gas? Why they use magnetrons and not coils?
 
@0celo7 where are you at? movie theater? amusement park?
 
2:28 AM
So, if at any finite distance the total energy is less than zero, then the system can't get to infinite remove: it's bound.
The graph shows you unambiguously that this is possible. To actually arrange that a bond occurs you need to bring an electron in and then lose some energy somehow.
 
I hate the term electro magnetic.... becose every moving electron or photon is described as "electromagnetic" but magnetic,electric and photon is three different things so when I tried to study on internet its giant cluster f-word becose all there ways to make ionised gas are described as electromagnetic
 
@Sweeper they arent really that different as far as things go
 
2:45 AM
I disagree! Magnetic ionisation is solenoid coil using high current..... electric ionisation is electrode using high voltage..... electromagnetic wave aka photon ionisation uses crystal like ruby or nd:yag and is pumped by flashtube
 
2:59 AM
ah, nevermind, figured out the nuclear physics question
only to find a new one in the next sentence
geesh
brehmsstrahlung?
are they trying to get people to misspell it?
so (generally) electrons decelerate as they come near a nucleus and emit a photon...okay...
but why does this affect higher energy electrons more than lower energy electrons? surely it'd depend more on how nuclei-dense the area was...
 
3:23 AM
asked a question about the above here if anyone's interested
 
3:41 AM
@heather It makes sense in German: the "ss" is a transliteration of a ß.
 
@dmckee oh yeah - the esset, right?
 
Yeah.
 
thank you for your comments by the way - I'm pulling up the Particle Data Book right now.
 
Of course, now that I look I find I'm wrong. It's spelled "ss" auf Deutsch, too.
 
and for the first comment - the faster car lost the most. though i'm not quite sure i get intuitively why that is.
 
3:47 AM
The intuition is tricky. In the math is just comes from the $v^2$ dependence which means slope increases with velocity. But to get why you have to really think about hte meaning of work and how the distance covered comes into play.
One of Ron M's old answer is a very nice treatment: physics.stackexchange.com/a/14752/520
 
okay, i'll read through that. also in the latest review of particle physics i can't find a chapter titled passage of radiation through matter. there is one called passage of particles through matter, is that it?
 
@heather Yeah. That's the one. I forget when they changed the title, but I still recall the old one.
 
okay
when you said hard sledding, you weren't kidding.
i'll give it a go, though =) thanks so much
 
4:12 AM
@heather Chicago
 
nice.
sorry to bug you @0celo7, but since you study nuclear engineering I thought I'd ask you - would you mind looking at this question?
 
isn't he in the middle of watching a movie?
although that would be a great test of multitasking :-)
 
oh, i didn't realize he was in a movie
i thought he was just in chicago
 
@heather whats the difference at that point
 
um...a city vs a movie theater
seems a fairly large difference to me =)
 
4:26 AM
all of life is a stage, and i bet chicago shenanigans rival the theater sometimes
 
2 hours ago, by 0celo7
@heather I'm standing in line for popcorn
 
"All the world's a stage, And all the men and women merely players" - As You Like It, Act II, Scene VII
 
Who is the watcher(audience)--- non-men and non-women ...lol
@heather
 
4:48 AM
@satyatech its actually a quantum superposition of them
 
 
2 hours later…
6:30 AM
@skillpatrol @heather Chicago is a musical
@heather It's spelled bremsstrahlung.
 
6:46 AM
@JohnR: Morning :-)
 
Morning :-)
 
7:05 AM
hello @JohnRennie
have you heard of this book?
 
No, that's new to me. But then I don't use Quora.
 
What do you think if one where to produce a similar book for SE
would one legally be able to publish such a book?
 
I'm not sure. The licencing for posts on Stack Exchange is documented somewhere.
 
There's a "legal" link in the footer
 
it is creative commons with attribution required
interestingly JEff states attribution should include a hyperlink
not sure how to include a hyperlink in a physical book though
 
7:10 AM
You could legally publish a book like that for SE as long as you distribute it under the CC license
@Kenshin You could just print the URL
 
yeah
@DavidZ do you think I could sell the book to recoup publishing costs?
or would the book need to be free?
 
There's no requirement that the book is free
 
yeah I thought so, so long as the content is under CC license
 
FWIW, there are CC licenses that prohibit commercial use, and if SE used one of those, then the book would have to be free (or maybe you could charge the cost of preparing a physical copy, if you were distributing physical copies)
But they have chosen a license without that particular restriction
 
nice
so the next step is to check if anyone is interested in the idea of a best of SE book
would you prefer to see a best of Physics SE, or a best of SE in general with chapters from a variety of SE sites?
I think a variety of sites is more interesting
since most users of Physics.SE already know the best content, but this book will allow them to learn intersting things from a variety of different topics
 
7:18 AM
Well, personally I don't think I'd be interested in this book either way
But you can ask around
 
Yeah I'll make a meta post and see if there is any interestr
@DavidZ while the content of user contributions on SE is licensed under CC, the Stack Exchange brand isn't. So before publishing we would definitely need the permission of SE
that is, if we are going to sell it with the SE brand
 
7:54 AM
If you called it something like "The Stack Exchange Compilation of Best Posts" then yes, you would need the permission of SE (and with that title I'm guessing you would be unlikely to get it). If you called it "Best of Stack Exchange" then it's unclear whether you would need permission, i.e. the mere fact that the book title includes the words "Stack Exchange" probably doesn't necessarily mean you need permission from SE. (But it might.)
 
yeha
I think if the book only consisted of physics posts, I would title the book PHYSICS
or Best of Physics
 
It's too hot,
It's too hot in this town.
My will to live is melting
And that's what's got me down.
It's too hot
And my state is on fire.
I'm an endothermic organism
And that's why I perspire
When it's too hot.
 
1
Q: The Best of Stack Exchange Book

KenshinAs you may be aware, Quora has created a physical book compiling some of the top contributions from a variety of topics. I'm wondering if there would be any interest in publishing a similar hard-copy book compiling the top posts from Physics.SE or perhaps even have the top posts from a variety...

 
Not all endothermic organisms perspire ...
 
8:09 AM
To be clear, I didn't write that song :-P
I'm (Yes, me) making lemon rice for lunch todaah, I will post a picture when I finish making it.
 
Ooh, lemon rice :-)
 
Yep. I'm off for about half an hour to make it, toodles!
 
8:49 AM
This is too early
 
9:19 AM
Sheesh, that took much longer than anticipated. Anyway, @JohnR, here:
^ Lemon rice and potato "crisps".
 
Looks yummy.
 
It was :-)
 
I don't see a fork?
or chopsticks
 
Fork?
 
To eat the rice.
 
9:23 AM
Typically, we eat rice (and everything else, really) with hand.
 
Hmm...very traditional :-)
 
In case it's gooey and I'm afraid to stain my dress or something, I use a spoon, not a fork. I don't even know how to use chopsticks.
Hang on, do people really eat rice with chopsticks?!
 
Chinese do.
 
Holy crap, wow, I see. I wasn't aware that it was even possible to eat rice using chopsticks!
 
Yup, it's a skill.
 
9:26 AM
Nice.
Using a fork to eat rice is simply ludicrous, though.
 
I do :-/
 
Spoons!
 
That sounds reasonable.
 
:-P Try--u'll be able to finish a lot faster.
 
10:06 AM
2
Q: The Best of Stack Exchange Book

KenshinAs you may be aware, Quora has created a physical book compiling some of the top contributions from a variety of topics. I'm wondering if there would be any interest in publishing a similar hard-copy book compiling the top posts from Physics.SE or perhaps even have the top posts from a variety...

 
10:29 AM
@Kaumudi.H peanuts?
 
Yes, peanuts too :-)
 
Wasn't that a bit dry just eaten on its own?
 
A bit dry, well, yes.
Tasty all the same!
 
I would have eaten it with a side dish. Sambar or some other vegetable disk with sauce.
 
Nope, lemon rice is a dry dish, we don't eat it with other curries, that corrupts the richness of the flavor.
 
10:36 AM
Kidney beans and rice...unbeatable combo..
 
@JohnRennie Got Led Zeppelin IV yesterday :)
 
Cool :-) On vinyl?
 
@JohnRennie Yep :P
I've had it in Flac for ages
 
You still use vinyl discs? o.0
 
Zep 4 is probably the one everyone thinks of as their best album, and I'd go along with that. There isn't a bad track on it.
 
10:44 AM
@JohnRennie Just listened to it end to end, truly a great record
I like III too
and in through the outdoor
 
They got a bit arty after that. Plant started trying to write deep meaningful lyrics rather than just concentrating on writing good songs.
I'm afraid I struggle to like In Through the Out Door ...
 
That album is worth it just for Fool in the Rain IMO
 
If I had to choose just one Zep album to take to the desert island it would be Zep 4, but 3 and 1 are also great albums. Zep 1 is the most awesome blues rock album I've ever heard, and 3 is a great example of how good they were when they weren't trying to write stadium classics.
Since I've Been Loving you is my favourite ever Zep song.
 
11:12 AM
"Next, we present the no-interaction theorems of Powers and Baumann. The central outcome here is that field theories conforming with the CCR/CAR must be necessarily free if the dimension of spacetime exceeds a certain threshold (d ≥ 3 for fermions and d ≥ 5 or d ≥ 4 for bosons)."
whaaaaaaaaaaat
 
@Sweeper uh... photons don't have a charge nor substructure, thus you cannot really ionise it. To ionise something is to excite electrons so that a net neutral object becomes positively charged.
Sleeeah: so... no interacting fields allowed in spacetimes d > 3-4....?
 
imho Pink Foyd is so much better than Led Zeppelin.
 
11:38 AM
@skillpatrol that's a bit of a false comparison. Pink Floyd are a completely different band and play completely different music. They are both among my favourite bands but I wouldn't try and compare them.
 
one of the last thoughts i had before going to bed: griffiths EM is awful
 
@Skyler ...but you're wrong
:)
 
@Danu its not as bad as his QM book to be fair
but he tries to simplify things to the point where he doesn't explain them enough that you can be comfortable working with the material
 
The QM book is a bit outdated now and it's sad that he decided not to mention tensor products at all---they're super important and confusing to students, I noticed.
@Skyler Like what? I think he has plenty of decent exercises.
 
@Danu he will actually never define some important things or his "official" equations are wrong
 
11:44 AM
Examples?
I'm asking because I've worked through almost all of that book, twice, and I thought it was very good.
 
in the conservation laws chapter he never actually defines the total angular momentum L
just kind of lazily talks about it by multiplying by volume
from little l
no $L = r \times S$
 
Isn't it clear that you just integrate?
Yeah, I think that at that point in the book the idea of mostly working with densities and integrating when necessary has become rather intuitive.
Anyways, I don't mean to put you down or anything---I just don't think that one should call Griffiths' book awful.
 
he's being really lazy there though, he makes you hunt through his text trying to see how he presents just to skip one line of equations
This wouldve been a perfect area to actually talk about the Poynting vector in a compelling way too
Like right after talking about Poyntings Theorem he says I just want to show you this compactly and doesn't really touch on it again for a while
You have to let him hold your hand through the whole book instead of being able to reference a section when you're missing a little something
 
3
Q: Good physics book to discover stuff by yourself

tpkI am asking for a book/any other online which has the following quality: The book, before introducing any particular theory about any natural phenomena, demonstrates and gives example of an good experiment, from which the theory is/can be developed. For example, about the topic Gravitation, b...

Too broad?
 
12:03 PM
@Qmechanic Probably.
 
12:22 PM
"We now show that if $f$ is not identically zero then $f(x) = 0$ has no solutions."
Well, I agree I suppose
 
1:06 PM
Hello
anyone good with latex?
 
0
Q: Hyper Magnetism?

Harry ZalesskyDidn't know where to post this one but this forum seemed the most suitable. So about a year ago I've discovered that my mom can "glue" metalic spoons and forks to her hand and mechanic watches slow down on her. Didn't mind that really much though it was pretty cool, till last Friday, when I decid...

is that on topic?
it is too weird though
 
@YashasSamaga It seems like a health problem more than anything else. :P
 
Spoons and forks made up of Neodymium !! I want them!!
 
Hehe :')
I want adamantium
 
1:21 PM
What's that?
 
Google search :D
Didn't watch Wolverine?
 
I watch cartoon movies only :P
Tangle, Frozen, Shrek, Jungle Book, BRB, Bolt, E.Wall, Toy Story, etc.
 
Kiddo :P
Is there any way to block sms from unknown numbers on Android ? I keep getting advertisements from some companies and I can't block them because they have no phone number! Any idea, anyone ?
 
@Kenshin Mi Yodeya did something similar a while back. It might be worth asking someone there about the process, both technical and legal.
 
thanks @HDE226868 my plan at the moment would be to not use the SE brand in the book
rather have the title something like PHYSICS 2016 with the font used here
and include the mexican hat potential
which is also CC
 
1:35 PM
@Kenshin Why not?
 
@Kenshin What? I don't think you can publish the book without attributing it to SE. That will be sort of illegal.
 
@anonymous I will be attributing the content to SE
but I cannot brand the book as being SE
because while the content is under the CC licence, the SE brand isn't
 
Uh that's okay
 
so the book won't be titled SE, but there will be appropriate attribution
 
BTW is there any specific reason why you want to publish it ? @Kenshin
 
1:37 PM
What's wrong with calling it "Questions and Answers From Physics Stack Exchange"?
 
@HDE226868 that may be ok but I"d err on the side of caution
@anonymous because I trust myself to get the job done
 
I'm not sure what you mean by "branding", then.
 
and it was my idea so I think I will publish it it @anonymous I see no reason to not publish it myself
 
@Kenshin No I am not saying that. I mean why do you want to make such a book ?
 
@HDE226868 if I say "best of SE" it implies that SE is the one producing the book
@anonymous it was just an idea that I had and I wanted to see if others liked the idea, that's all
 
1:39 PM
@Kenshin . . . So what name that includes "Stack Exchange" doesn't?
You're going to need community support to do this.
 
@HDE226868 sorry when I typed SE I was being lazy, I meant Stack Exchange
 
You might as well ask SE itself.
 
Actually you will be allowed to the site logo
 
@HDE226868 I don't legally need support no
@anonymous yes the mexican hat potential can be used, it is licenced under CC so I plan to use it
 
@Kenshin I meant that you likely will not be able to do this entire project by yourself.
 
1:41 PM
@HDE226868 I disagree but I think input from the community with regards to what questions to include would definitely be helpful
that said, if people want to help I have no problem with that
but I'm not going to hold off on the project waiting for people to assist
 
I'm just saying, you might as well ask Stack Exchange what you can and cannot do.
The company as well as the community.
 
Yeah, make a post on main meta. That'll help you.
 
@HDE226868 I find the SE community can often be quite negative to ideas. I'd rather create a product fiurst
 
@Kenshin I think I'll duck out now, but people are not going to like that.
 
@HDE226868 the first product will be for physics only
I have posted in the physics META
once this becomes popular I will then move to the broader community
and create one for mathematics
and other subjects
the Physics one is the prototype if you will
I think the broader SE community will be more receptive of the idea when they see a successful prototype
 
1:46 PM
So ask the company what you can do.
 
what do you mean "what I can do"?
do you mean legally?
 
Yes.
 
the company can't give me legal advice
the creative commons licence is clear what I can and can't do
 
But you seem to be unclear on the limits of how you can use the name, for instance.
The company can probably be more explicit.
 
@Kenshin But they can sue you in case your book violates some policies. Precaution is better than cure. One Meta SE post asking for your legal rights won't stop your project.
 
1:48 PM
yes but wehther I put the SE logo on the book or not doesn't matter too much so maybe when the book is ready I can ask them
@anonymous they can't sue me because I won't be violating the CC licence
SE doesn't own the content on their site
 
Hmm, anyway good luck for your project. I'll buy it if it is published. :)
 
ty @anonymous
 
2:16 PM
@ACuriousMind plz help
 
2:44 PM
@Slereah do you need analysis or algebra
 
I need to know why all QFT is a lie
 
What happened now?
 
"Next, we present the no-interaction theorems of Powers and Baumann. The central outcome here is that field theories conforming with the CCR/CAR must be necessarily free if the dimension of spacetime exceeds a certain threshold (d ≥ 3 for fermions and d ≥ 5 or d ≥ 4 for bosons)."
There's no interacting QFT in 4 dimensions
It's all lies
 
Lol what
 
I mean I vaguely knew that $\phi^4$ theory was probably trivial
but dang
 
2:53 PM
@Slereah what?
I need a proof of this
 
IIRC the heuristic is like
 
Your statement isn't very valuable. What exactly is wrong with writing $\mathcal L_0+\lambda \phi^4$?
what does it violate?
 
$\lambda \phi^4$ is divergent if $\lambda < 0$
But it is fine for $\lambda = 0$
So by continuity it's probably not a good theory for $\lambda > 0$
Or something like that
 
@Slereah what
 
I don't recall the exact argument
It was something along those lines
 
3:02 PM
if your function is $\infty$ for $\lambda>0$ and zero for $\lambda =0$, then there is no continuity
 
"Triviality of lattice phi^4 theory in this sense has been rigorously proven for D>4 while for the most interesting borderline case D=4 we have only partial results but very strong evidence from numerical simulations."
"The recent proof of triviality of phi^4 in 3 + 1 spacetime dimensions indicates that the situation becomes worse in the real world, and in particular the renormalized perturbative series of the phi^4 model seems to have little to do with the non-perturbative solution."
Basically all of QFT is a lie
put it in the trash
 
3:35 PM
@Slereah you know what is not a lie?
 
GR
 
Math.
Well, and that.
 
What about the axiom of choice
Is it a lie
 
GR is basically math it's so well-defined
 
hello
 
3:36 PM
hey
 
@0celo7, how was the musical?
 
Did @0celo7 perform in a musical
 
no, watched one
 
Unfortunate
 
Btw, apropos this meta post, wasn't there someone recently who lifted answers from SE and published them?
 
3:42 PM
That's not recent at all
It was like over a year ago
 
@Slereah : Do you recall the name/have a link?
 
Hm
It was discussed here
It was one of those cheap book and it was just a list of good questions and answers from PSE
nothing more than that
 
@Qmechanic does the SE licensing model allow that? (I'm actually curious, I have no idea ?)
 
Questions and answers on Stack Exchange are public domain, yes
 
as long as you attribute them, you're good, right @Slereah
 
3:49 PM
Well if it's public domain you don't even have to
But it was attributed, yes
Do we even have a clue if string theory is bullshit or not
 
yes
 
So
is it
 
it's at least not obviously bullshit to people who know more than me :)
 
It would be nice if there was some demonstration of a basic string theory process
Like just
A free particle moving through space
 
4:16 PM
@heather good for the most part
There were some really bad numbers. Not sure if it's the musical or the cast at fault there
 
hmm, that's unfortunate
at least it was mostly good.
 
4:40 PM
BRST symmetry in a path integral, any ideas?
 
what about it
 
Looks so random in P&S, the infinitesimal transforms
Where do they come from, why are they obvious/easy?
 
@Kaumudi.H My lunch was considerably less refined than yours :-)
 
4:58 PM
Hii
 
@JohnRennie What are those?
 

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