The h Bar

David Z

12:06 AM

@ChrisWhite well the moderators are not allowed to discuss it. Other people are just discouraged from doing so.

Anthony

@DavidZ If I have a function like sin(kx) and x is meters, does k have units radians/meters, or just 1/meters?

I have a homework assignment where it seems it should be 1/meters, but what about radians!?

David Z

@DumpsterDoofus He was suspended for violations of the site rules as described here. We can tell you that, but no more.

I would suggest that you take anything else you hear with a grain of salt. Other people do not actually know why individual suspensions are issued, but they are prone to speculating about it so you can get a lot of misinformation.

2

@Anthony The radian is a "fake unit", i.e. you can just replace it with 1.

Anthony

But why, though?

What is a radian then?

dmckee

The "fakeness" of the radian arises because it is a ratio of (arc length)/radius which has units of [L]/[L]=1.

Anthony

Ah!

David Z

12:13 AM

yeah, what @dmckee said :-)

Anthony

That's strange.

Brandon Enright

@dmckee I type ration almost every time too. Damn finger memory.

dmckee

I'm glad it's not just me.

Must be my most common edit.

David Z

@BrandonEnright me too actually

Brandon Enright

A few months ago I searched the site for "ration" and made almost a dozen edits.

Anthony

12:14 AM

Why does it exist then? $w=2\pi*f$...

David Z

For physicists, it kind of doesn't

I mean, in physics we often just don't write radians at all

Anthony

When you introduce some rotation, angular frequency is really just scaling the argument to the circle?

dmckee

People are used to talking about angles with units. That is, in a lot of contexts it is more natural to say "pi-over-four radians" (which feels like "forty-five degrees") than to just say "pi-over-four".

Anthony

But then a degree isn't a unit either, is it?

dmckee

It has a long historical usage as a unit.

David Z

12:17 AM

Sure it is, it's a unit with a value of pi/180

Anthony

I guess a radian kind of just expresses a direction....

Well I mean it's not like meters.

dmckee

The other thing that makes radians special is that the Euler formula (and the Taylor expansions for sin and cosine, but these are the same argument) have the simplest form when the angle is expressed in radians.

Anthony

Also, how is there this discrepancy between degrees and radians?

The small angle approximation works for radians, why are radians somehow more mathematical than degrees?

Brandon Enright

@Anthony What do you mean discrepancy? Degrees are arbitrary just 360 in a circle.

David Z

@Anthony You can do it for degrees too, you just get an extra factor of pi/180 or 180/pi

I forget which

dmckee

12:19 AM

The SMA works because the Taylor expansion requires no coefficients. That is essentially what I was saying about the Euler formula.

Anthony

@dmckee what coefficients? The pi/180?

I see. People just took 360 before they knew 2*pi?

dmckee

The Babylonians liked powers and multiples of 60 because they have lots of integer divisors and their math had no good way of managing arbitrary fractions. They are the ones who first divided the circle into 360 pieces.

@Anthony Yes.

Anthony

Yay!

Thanks guys!

user54412

3:19 AM

@BrandonEnright me too!

tpg2114

4:01 AM

Hey, so magnetic monopoles

nature.com/nature/journal/v505/n7485/full/nature12954.html

ManishEarth

@tpg2114 yeah. nobody's answered my question o how real they are yet :p

tpg2114

@ManishEarth Sounds like you should place a bet xkcd.com/955

ManishEarth

haha

tpg2114

Oh. Huh. Apparently I'm late to that game. And that joke chat.stackexchange.com/transcript/71?m=13476501#13476501

Guess I should just stay quiet... you'd think I'd learn that lesson

@KyleKanos I apologize for inadvertently plagiarizing your joke.

Great minds think alike?

user54412

6:22 AM

"are there major [] universities choosing not to take part?" Caltech for one. — dmckee 4 hours ago

user54412

@dmckee I dunno, if the NCAA is santioning Caltech, they must be doing something right ;)

Kyle Kanos

1:24 PM

@tpg2114 I'm pretty sure that the joke is GPL'd, so fair game.

Kyle Kanos

1:54 PM

What the: seattle.cbslocal.com/2014/01/30/…

Waffle's Crazy Peanut

2:15 PM

Wait! But, isn't this spamming? o_O — Waffle's Crazy Peanut 41 secs ago

kalina

3:07 PM

@Waffle'sCrazyPeanut that's a good question

from what I can see, it's only been posted the once

so I wouldn't call it spam, per se

Waffle's Crazy Peanut

@kalina Hey!!! We usually spam things which are necessarily posted with an intention to advertise. No? o_O

@kalina: BTW, Welcome to our bar :P

Undo

hehe

chatflags draw folks from all corners of SE :P

kalina

I don't intend to stay, you'll use sleazy physics based chat up lines on me

Waffle's Crazy Peanut

@Undo Yeah, yeah... :D

@kalina You think we chat "Physics" here? Oh, of course... We do chat "physics" - but most often, we just hang out here :D

Kyle Kanos

We discuss all sorts of things. Like Ape's picking the winner of the Super Bowl

Waffle's Crazy Peanut

3:14 PM

^^^ yeah, like that!! :D

kalina

ok cool, but anyway

I'm going to leave you

Waffle's Crazy Peanut

Oh, c'ya later then ;-)

kalina

if that guy feels like posting more physicsoverflow stuff, it would technically be spam from the second post onwards

I'd flag them for moderator attention rather than chat flagging them

since a chat flag won't present any context to anybody who is reviewing the flag and it will get denied

o/

EnergyNumbers

4:10 PM

@kalina Moderators can always come in or examine the transcript, consider the context, and then decide that it's spam. And deal with it accordingly. Please do flag spam as soon as you see it, whether it's in chat, meta or main site.

kalina

@EnergyNumbers mod flags are better suited in this instance, as they can't be dismissed by users

EnergyNumbers

4:50 PM

@kalina The advantage of spam flags is that they teach the anti-spam system. You're right, mod flags are effective: because we can act on them by flagging the message as spam.

David Z

6:15 PM

0

Q: What is the constant $K_1$ in these orbital equations?

I want to compute the derivatives of argument of periapsis and longitude of the ascending node of the orbit of a GPS satellite from the following formula. $$\frac{d\Omega}{dt} = -K \cos{i} \\ \frac{d\omega}{dt} = K ( 2 - 2.5 \sin^2{i}) \\ K = \frac{nK_1}{a^2(1-e^2)^2}$$ But what is $K_1$?

It might be useful to discuss whether that should be closed. Some people voted to close because the OP already found the answer but I don't think that's really a proper close reason...

user54412

@DavidZ I voted to leave open

Kyle Kanos

Same here

user54412

note physics.stackexchange.com/help/self-answer says OP can't self-answer for 5 more hours

David Z

oh, rules are weird

Kyle Kanos

@ChrisWhite We could always community-wiki an answer for him

user54412

6:22 PM

@KyleKanos true, but that denies him any rep for the answer

user54412

the question isn't so well-phrased as to garner much upvotes, but a good answer might

ManishEarth

in The DMZ, 7 mins ago, by ManishEarth

Guys, I've just created a partial chat API. Currently can only post messages. Ideas as to what I can do with it?

in The DMZ, 7 mins ago, by ManishEarth

I already replaced kalina with a script

in The DMZ, 7 mins ago, by ManishEarth

And made a minified feedbot

Kyle Kanos

@ChrisWhite Seems to be a fairly local question, doubt there would be much interest altogether

ManishEarth

@DavidZ it isn't

David Z

Something else to discuss:

-1

Q: Proof of minimum distance between object and image of a convex lens image being 4*focal length

I can prove that the minimum distance between an object and its image, through a convex lens is 4*focal length, if I assume that the distance between the object and the lens is the same as the distance between the image and the lens, i.e. if: $$1/u + 1/v = 1/f$$ that $u=v$, but is there a way of...

homework optics lenses

does that violate our HW policy or not? I'm leaning toward not, but I'm not sure.

user54412

6:32 PM

meh - I don't feel one way or another on that

Kyle Kanos

That one does seem kinda borderline

ManishEarth

@DavidZ borderline here too

Mostafa

About Dimension10's post above:
Why do you think speaking about PhysicsOverflow here should be considered as *spam*? Although I personally don't know much about their work, I don't think PhysicsOverflow, which is a theoretical physics Q&A site, should be viewed as an opponent to Physics.SE.

2

ManishEarth

Technically, it's promotion for a site. A site that overlaps on the scope.

Besides, in the initial stages (and in comments every now and then), it has been touted as a "If you don't like it here, go there!" sort of thing.

Kyle Kanos

@Mostafa From their website: A question and answer site about advanced Physics, from graduate-level and beyond, including Theoretical Physics, Phenomenology, Experimental Physics, and Astronomy. On-topic subtopics will include String Theory, Loop Quantum Gravity, String Phenomenology, advanced Quantum Field Theory, Experimental Techniques, etc and for Physicists relevant Mathematical Topics.

Their site overlaps in intent/purpose, therefore it's a competitor

Mostafa

6:44 PM

@KyleKanos Yes, but the point is that their success will be good for us too. We had a theoretical physics proposal here that failed. If they succeed at building the site, it can become a subset of SE network too; like MathOverflow.

Dilaton

@KyleKanos nope, PhysicsOverflow is intendet to have the same relatinship to Physis SE as MathOverflow has to Mathematics SE. It will be a higher level companion if anything and not a competitor. The site is intended to be some kind of a revival of the closed Theoretical Physics SE with a slightly broadened scope and lowerd bar to ask questions (graduate level upward), whereas Physics SE accepts all (including popular) level.

Kyle Kanos

As a non-interested party to PhysicsOverflow, that is how I view it. You two, as seeming insiders, have a differing opinion, which is awesome and all, but I just don't care to get into the details about it

ManishEarth

@Dilaton you don't see users from Mathoverflow posting comments on Math.SE urging users to switch if they don't like it.

Dilaton

BTW I dont see why it should be a bigger problem to talk about it than for example mentioning Quora, Physics Forum, etc on Physics SE if not done in excess and/or at completely inappropriate places...?

@KyleKanos sure, I dont care about everything talked about here in chat either ;-).

Kyle Kanos

@Dilaton Not sure what to make of that sentence

Dilaton

6:56 PM

@ManishEarth I have seen many comments suggesting people to switch to Quora, Physics Forum, etc if they are not happy with how things work here on Physics SE... So I dont see a big difference ...

@KyleKanos I mean certainly knowbody likes or is interested in every comment or topic talked about in chat.

ManishEarth

@Dilaton Nobody posts advertisemets for Quora or PF on meta. If they did, it would be deleted.

3

Kyle Kanos

@Dilaton Understood

Dilaton

@Manishearth ok... Have to do a phone call now ...

Mostafa

7:20 PM

@KyleKanos I have not ever visited PhysicOverflow, so I'm not an insider certainly. I just wanted to say it is hard enough for PhysicsOverflow to succeed, and you should not be hostile towards it.

@Dilaton When advertising/finding users for PhysicsOverflow, keep in mind what Jerry Schirmer said here: (you should build a community other than Physics.SE's)
http://meta.stackoverflow.com/questions/130361/why-did-theoretical-physics-fail/130704#130704

Kyle Kanos

@Mostafa Not much interested in its failure or its success.

5

Mad Scientist

7:38 PM

@Mostafa The hostility is pretty much coming from the other side in this case, or at least the creators of PhysicsOverflow speak rather harshly about this site and its users. They have spent a lot of time insulting users of Physics.SE on Lubos' blog

Brandon Enright

7:51 PM

@KyleKanos At first I felt the same way but now I lean towards hoping it succeeds so that some of the criticism of Physics.SE is reduced.

4

user54412

The chord-length probability density of the regular octahedron

user54412

(1) Does it really take 20 pages to calculate the result?!

user54412

(2) Has no one done the dodecahedron or icosahedron yet? How hard can it be?

Brandon Enright

8:16 PM

@ChrisWhite "...this point it is not unreasonable to conjecture that the γ (r)s of all Platonic solids have an algebraic form and, recalling the parallelepiped result as well as the result shown in the two-dimensional case for polygons, the conjecture holds likely true for all polyhedrons."

My reading of that is that the solution to the octahedron wasn't known to be algebraic but turns out to be.

user54412

It seems weird to even question that it will be a simple answer - I mean, we're asking a simple geometry/probability question about the simplest of 3D shapes

user54412

I guess it's a harder problem that it at first appears

Brandon Enright

@ChrisWhite I'd never heard of a chord-length probability density but this seems relevant:

Bertrand paradox (probability)

The Bertrand paradox is a problem within the classical interpretation of probability theory. Joseph Bertrand introduced it in his work Calcul des probabilités (1889) as an example to show that probabilities may not be well defined if the mechanism or method that produces the random variable is not clearly defined. Bertrand's formulation of the problem The Bertrand paradox goes as follows: Consider an equilateral triangle inscribed in a circle. Suppose a chord of the circle is chosen at random. What is the probability that the chord is longer than a side of the triangle? Bertrand gave thr...

And it does seem much more complicated than I'd expect.

Amaterasu

@MadScientist yup, just noticed that.... wow, I was going to do my usual wandering around the internet to go hav a looksee, but if they dislike us here that much, I would not get a good reception having being a contributor here....

Brandon Enright

@Amaterasu I really don't think there is that much hostility or contempt. I'm pretty sure they'd welcome your contributions.

Mad Scientist

8:31 PM

> Asking questions there is for me no longer feasable as the arrogant pompous dimwits and know-nothings capriciously are capable of closing good to excellent questions too, for se political reasons, because they dont understand them, or whatever :-(

Just one excerpt of the stuff they're saying about Physics.SE

Amaterasu

@BrandonEnright not really, as a member here, we seem to be "arrogant pompous dimwits and know-nothings" according to the above

Brandon Enright

@MadScientist shrug Seems like an emotionally charged venting of frustrations. Probably best to ignore it.

Mad Scientist

@BrandonEnright My main point was to explain to some extent why the reception of posts promting the site is rather frosty, as not all users kept up with the whole drama

Brandon Enright

@MadScientist yeah. There isn't any good response to ad hominem attacks other than to point out that it's an ad hominem attack and therefor doesn't warrant any further response.

Amaterasu

it just seems not worth it to even try to start an account over there

though, I am not really doing all that well here either

Brandon Enright

8:50 PM

On a related note, I wonder what the criticism of "Of Particular Significance" is about. I've always gotten the impression that when it comes to physics, he knows what he's talking about.

Amaterasu

who?

ManishEarth

@BrandonEnright ?

Brandon Enright

Matt Strassler's blog "Of Particular Significance".

I can't figure out how to directly link to the comment but Dimension10 wrote "You seem to have “Backreaction” and “Of particular Significance” on your blog roll. I think you forgot to unfollow those blogs . . .".

I'm curious what's the perceived issue.

Amaterasu

@BrandonEnright i seriously doubt that I'd be welcome there, I am barely welcome here

Brandon Enright

@Amaterasu What do you mean? I've never felt any sort of hostility here or unwelcoming environment.

Amaterasu

8:55 PM

@BrandonEnright not hostility, just an 'outsider' type feeling

ManishEarth

@BrandonEnright timestamp=comment link

Brandon Enright

@ManishEarth Ah thanks. Link: tpproposal.wordpress.com/about/comment-page-1/#comment-44

ManishEarth

oh, there

Amaterasu

and by 'outsider', I mean that my fields of interest are seemingly are less known (respected?) than most branches of physics (atmospheric physics)... I will perservere though

Brandon Enright

@Amaterasu I have a general "hobbyist" interest which prevents me from making any significant contributions. I mostly nibble away at the easy stuff.

... And once in a while really stick my foot in my mouth when I think I know something it turns out I don't actually know very well.

Amaterasu

9:04 PM

@BrandonEnright i tried that, but my answers are not all that well regarded... and I'll probably lose 25 odd points for one when it gets deleted

Brandon Enright

You lose rep when an answer is deleted?

Amaterasu

yes

Brandon Enright

Huh, I had no idea.

Amaterasu

and my rep is pathetic as it is

actually I'll lose 27 points, as I edited the question too

and to think, I got my PhD in Physics

@BrandonEnright so my rep will soon go back to 231

Brandon Enright

@Amaterasu Well just answer the small stuff and you'll gain rep slowly but steadily.

Amaterasu

9:10 PM

that's what I did.... but it's 'closed' now and soon no doubt will be deleted

and the rep earned will also go

@BrandonEnright I always thought your contributions are good

I have a dozen or so questions rattling around my head

Brandon Enright

@Amaterasu Post 'em

Amaterasu

lol, yeah right

they are mostly about atmsopheric science, other planets atmospheres and such

Brandon Enright

@Amaterasu Just do your best to keep them narrow and specific and you should do fine.

Amaterasu

nah, there seems to be very little interest

lately, I have just been reading the questions, and looking at the unanswered list.... might go answer one or two of them... (which I have done so, but to very little regard)

@BrandonEnright you have an impressive rep, more importantly, your answers are great

Brandon Enright

9:31 PM

@Amaterasu My answer quality hasn't really changed but as I've slowly gained rep it seems users assume I have more authority so what used to gain 0-1 upvotes now will gain 2-6.

Amaterasu

@BrandonEnright I am hoping the Earth Sciences gets into beta... then I could ask/answer about another of my major interests - geology and seimology

@BrandonEnright i'll persevere, my answers tend to be big with relevant diagrams, like this one physics.stackexchange.com/questions/72711/…

that one took me 2 hours to do... not sure why I spent that much time

mind you, between work, weight and long distance walking training, hospital visits and too much volunteer work, I sometimes don't have time to do anything

Brandon Enright

It seems like a pretty good answer to me. This answer of mine took a similar amount of time. The effort put into a question is very poorly correlated with how many upvotes it will receive.

I've seen some crazy long detailed answers by joshphysics that must have taken many hours but they get no upvotes, probably because it's over almost everyone's head so they don't even know if it's any good or not.

4

Amaterasu

and even though it took the addition of a bounty to get it, the answer I have received on my 'Morning Glory roll cloud' question was spot on... my other 2 questions are unanswered

@BrandonEnright damn! thats a good answer

Brandon Enright

It's one of those answers where I started out having only a very general idea for what the answer was and ended up doing a lot of research and reading to fill in the details. It's really something anyone willing to spend the time could have produced the same content.

Amaterasu

same with mine

jinawee

9:56 PM

So pathetic...

tpg2114

11:31 PM

@Amaterasu It's a chicken and egg thing. You say there's not much interest but there's also not much content. Having good questions (even without answers) means people who are interested but not on the site will see it in the favorite search engine. And maybe they'll sign up to answer it

And eventually you'll have people in your interest area contributing. So ask away

I usually try to take on all the atmospheric fluid dynamics questions that come up because I find them interesting, although rare. Which is kinda true for all fluid dynamics questions really

There's 2 ways to go from "outsider" to "insider" -- change what you do so you're on the inside with everybody else, or start building the extra room attached to the house so now you're inside too

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