The h Bar

ManishEarth

7:34 AM

@TRiG I think the name was @DavidZ's idea. You can thank him :)

We used to be called "The Coupling".

RhysW

@ManishEarth yeesh i bet jokes were made about that on a daily basis

David Z

8:04 AM

@ManishEarth Nah, it was someone else's idea, I just made the change

"The Coupling" was my idea

RhysW

8:15 AM

I have never noticed that mods names are blue in chat

David Z

10:07 AM

Don't forget, everyone, a chat session is coming up in about 6 hours!

RhysW

@DavidZ a specific topic or just getting everyone together?

Crazy Buddy

11:10 AM

@RhysW: My "Axe murder" horror question got 1k views :)

RhysW

@CrazyBuddy the what now?

@CrazyBuddy linky?

Crazy Buddy

@RhysW Aargh.. How did you forget that?

3

Q: Horror story writer moves with his family into a house where the previous family was murderered

I watched a movie a few months back. The movie starts with four people hanging by their necks on a tree. The hero is a writer of horror stories. He comes to a house along with his family. He finds a projector with several film rolls on the attic. He watches those films everyday. All films were ba...

RhysW

oooh that one

Crazy Buddy

That's what I call SE blockbuster... I think the title attracted more people...

RhysW

the titles on gaming.se is the best

Crazy Buddy

11:17 AM

Ohhh... like "How can I kill this guy?" o_O :)

RhysW

How can I tell if a corpse is safe to eat?
How can I kill adorable animals?
My head keeps falling off. What can I do?
Is it dangerous to go extreme pig riding in a thunderstorm?

3

all actual titles

Crazy Buddy

@RhysW Yeah... similar ones. Physics.SE gets such titles twos or thrice a year ;-)

RhysW

@CrazyBuddy oooh examples?

Crazy Buddy

@RhysW You should've heard those...

31

Q: Why doesn't light kill me?

I was attending my philosophy class and in the middle of student presentations, I found myself mentally wondering off and thinking about light. After a few minutes of trying to piece together how the sun works I came to ask a question I could not answer myself. Why does each individual photon hav...

energy electromagnetic-radiation visible-light photons

RhysW

oh thats just made me think of a question i want to ask!

Crazy Buddy

11:25 AM

@RhysW Ask your questions... Very busy to spend time posting stuff? ;-)

RhysW

il ask it after lunch

or during lunch

or whenever i have time to

its about light

and earth

Crazy Buddy

@RhysW Ohh... Enjoy both... ;-)

RhysW

um, thanks?

Crazy Buddy

2:26 PM

Anyone around..?

Does "pedagogical virus" mean teaching something crudely ??? o_O

Physics Meta

2:42 PM

0

Q: Policy regarding intentionally counter-productive users

I recently noticed a joke post; a user intentionally asked and answered a question that was a very subtle mockery of research-level physics papers and had no application as an actual question on this site. I've got a sense of humour, it was pretty funny, so I thought "we can let this slide. Close...

discussion policy users

Anonymous

3:25 PM

@David Zaslavasky: This suggested edit: physics.stackexchange.com/review/suggested-edits/21181 came from the OP's own comments on annav's answer. How does that change too much ? .

Anonymous

...

Anonymous

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Anonymous

???

Anonymous

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Crazy Buddy

3:50 PM

Welcome to our Physics Chat session everyone :)

ManishEarth

Anyone around?

Also, 9 more minutes to go

Crazy Buddy

1 hour ago, by Crazy Buddy

Does "pedagogical virus" mean teaching something crudely ??? o_O

ManishEarth

I guess it means a teaching tool (could be an analogy, or whatever) that spready easily but is harmful

Crazy Buddy

That's it??? o_O

David Z

@CrazyBuddy it can get confusing when you welcome people to the chat session before the chat session actually starts ;-)

Crazy Buddy

4:00 PM

@DavidZ I should add advanced or something next time...

David Z

Or just wait until noon EDT

which it is

now

so I guess we should "start" :-P

Who's here?

Crazy Buddy

@DavidZ It's night..! I'm postponing my dinner everytime for this chat session :)

ManishEarth

@DavidZ No it's not. You prejudiced EST folks think you rule the world. Hmph

@DavidZ Me!

David Z

@ManishEarth that's EDT, thank you very much

there, edited :-P

user54412

yay East Coast!

Crazy Buddy

4:03 PM

@DavidZ I'm the one who reminded you all..! Suffer my infinite wrath :)

ManishEarth

@DavidZ Hm. Never had heard of that till now. And I used to live there

David Z

You never heard of daylight savings time?

ManishEarth

No, never heard of EDT

of course I heard of Daylight Savings time :P

user54412

EST -> EDT during Summer

ManishEarth

I know, I know

Crazy Buddy

4:04 PM

@DavidZ I heard... That coal supply was less during WWI (Isn't that the real story? :P)

user54412

but most people mistakenly say EST during summer - technically it's 11:04 EST

David Z

@CrazyBuddy I don't know, perhaps you should ask Wikipedia

Crazy Buddy

I know... Okay.... Okay.... :D

David Z

Anyway, do we have anything in particular to talk about today?

ManishEarth

@ChrisWhite Somehow I keep thinking you're in California.

Crazy Buddy

4:06 PM

Meh... Here we go.... :D

ManishEarth

Please let it not be tags :P

Crazy Buddy

@ManishEarth I'll ping Dilaton .... :D

user54412

I'm curious if anyone from the non-astro side of things is keeping up on Cas A

user54412

for instance arxiv.org/abs/1308.2137

ManishEarth

2 days ago, by ManishEarth

Time crystals? Crackpot or mainstream?

David Z

4:08 PM

@ChrisWhite no, I haven't heard about it

RhysW

did someone say time crystals?!

user54412

@DavidZ basically, it's a supernova remnant that we know the age of quite well (about 300 years)

ManishEarth

@ChrisWhite Cas A ... hmm, wasn't that related to a quite important radioastronomy discovery having to do with black holes?

Crazy Buddy

@RhysW None by the name... Take care now... Bye bye then :)

RhysW

oh ok

(waves)

user54412

4:09 PM

and we see the neuton star cooling in real time

user54412

so it heavily constrains the physics of the interior

David Z

@ChrisWhite oh, well I know about Cas A, I meant I hadn't heard about why it's particularly interesting lately

That is pretty cool

:-P

...that was a terrible pun

ManishEarth

@ChrisWhite wha..?

How can you have fast cooling at that scale?

user54412

@ManishEarth look at figures 2/3 in arxiv.org/abs/1308.2137

ManishEarth

Or is it rapidly ejecting energy like a black hole with an accretion disk?

user54412

4:13 PM

basically, before this was observed, it was predicted that there would be a rapid cooling phase due to the onset of superfluidity of various species etc.

user54412

the cooling phase probably lasts a decade or three, and we started observing this just at the right time

ManishEarth

@ChrisWhite nice!

user54412

@ManishEarth I should mention, neutron stars cool primarily via neutrino emission in their youth

ManishEarth

yep

David Z

It's great how I can read the abstract and the introduction and actually kind of understand what they're saying

ManishEarth

4:16 PM

That's the nice thing about abstracts :)

David Z

Not always

ManishEarth

Well, yeah

Anyone around?

Crazy Buddy

@ManishEarth From the audience... Yeah.. me :)

David Z

yeah

ManishEarth

Hmm

David Z

4:24 PM

I just don't particularly have anything to talk about

ManishEarth

Ah

user54412

indeed

ManishEarth

I've been playing around with a rather interesting system -- music

user54412

?

Crazy Buddy

I don't usually talk when professionals are discussing "stuff" :D

David Z

4:25 PM

@CrazyBuddy well there's your problem

user54412

@ManishEarth covering up holes over nodes in your flute?

ManishEarth

In Indian classical music, the notes are separated in a certain set of frequency ratios (Western music has them equally spaced on a log scale)

Now, there's a well-known reason for the ratios; there's good resonance there

Crazy Buddy

@DavidZ Of course... I'm not really good.. I'm still learning from you people.. To be true, I can't cope up....

ManishEarth

But I wanted to see how good the resonance was when compared to other notes

user54412

@ManishEarth talking about a raga?

ManishEarth

4:26 PM

@ChrisWhite nono

David Z

@CrazyBuddy no I mean you should talk more

or rather, don't have this attitude that when "professionals" are talking you need to stay out of their way.

user54412

@DavidZ +1

ManishEarth

@ChrisWhite The notes themselves. Do/Re/Mi/... aren't separated by $2^{1/12}$ and $2^{1/6}$ like in Western music

Crazy Buddy

@DavidZ No... I'm not really like that too... Else, I wouldn't have talked at all...

I'm still trying to communicate... (quite nicely)

ManishEarth

The notes are arranged so that there's good resonance with the harmonics of other notes. More or less

user54412

4:28 PM

@ManishEarth ah ok - keep going (I'm actually really interested in music theory at this level)

ManishEarth

While usually you deal with 12 notes, there actually are a total of 22 in Indian classical music. But they mostly come in close by pairs. So you have two flat Re's, two natural Re,s, Two flat Mis, etc

user54412

22 / octave?

user54412

that's rather dense

ManishEarth

@ChrisWhite yep

user54412

this is sounding like resolving doublets in spectroscopy

ManishEarth

4:30 PM

Each note ^

If you look at it, the numbered pairs are quite close. If you take the capital notes you get your normal octave, if you take the lowercase ones as well you get your umm...12-ave

But most notes are two notes

Interestingly, the 12-ave in Indian music comes pretty close to the 12-Ave in Western music

user54412

12-ave <-> chromatic scale?

ManishEarth

Yeah

I should have remembered that :P

user54412

hmmm, wonder how close this is to Chinese scale construction

user54412

(to the extent that there is a well-defined Chinese standard, they basically start with one note and apply a series of simple whole number ratios to it to get new frequencies, using factors of 2 to get back into the appropriate octave as needed)

ManishEarth

4:36 PM

So anyway I'm analysing the overlap of non-sinusoidal waveforms (that contain strong harmonics) with themselves at varying frequencies. I'm getting some strange results, and it seems to be like chaotic behavior with the fixed points as a subset of the notes

@ChrisWhite It's similar in Indian music. You recognize the strength of the harmonic overlap of Sa(Do) and Pa(Sol)/Ga(Mi), and you reuse those ratios a couple of times

The numbers look different though

user54412

@ManishEarth 243/128 is suspiciously the last entry in both

ManishEarth

There's a common 81/64 too

and 9/8

brb

user54412

lots of (3/2)^n, give or take enough factors of 2 to put it between 1.0 and 2.0

Crazy Buddy

@ChrisWhite: In the meanwhile, I can't really understand how something orbits the lagrange point itself...

> A spacecraft in a halo orbit does not technically orbit the Lagrange point itself (which is just an equilibrium point with no mass), but travels in a closed, repeating path near the Lagrange point. Halo orbits are the result of a complicated interaction between the gravitational pull of the two planetary bodies and the coriolis and centrifugal accelerations on a spacecraft

I got this from Wiki... (Halo orbit)

ManishEarth

@ChrisWhite That's because the 3-2 resonance is the strongest

1-1 and 2-2 are just fundamentals overlapping, and 1-2 is the standard octave shift

3-2 (Sol-Do/Pa-Sa) is the best overlap there is

Second to it is 2-3 (Fa-Do/Ma-Sa) and then 3-5 (Mi-Do/Ga-Sa)

Basically it's all about the harmonics of a note overlapping

What I'm trying to do is to see if there's a way to construct a way of gauging how pleasing two notes will sound when played together mathematically

user54412

4:45 PM

@CrazyBuddy You could try reading my excessively wordy explanation:

user54412

0

A: Why are L4 and L5 lagrangian points stable?

I think there are some good explanations here, but I'll try to add a very simplified, hopefully intuitive explanation. First, let's agree on some conventions. Suppose the Earth is going counterclockwise around the Sun. It's going in a circular orbit at a distance $R$ (from the barycenter) with a...

user54412

no equations but it might help to draw a diagram as you're reading

Crazy Buddy

@ChrisWhite Thanks... BTW, I haven't noticed that answer of you ever... :)

I'll ping you when I get something wrong (if you're unlucky)... :D

user54412

basically, if you are co-rotating (say in Earth-Sun L4, moving around the Sun at 1 orbit /year), then if you are inside the orbit of the smaller mass, you are moving too fast for that radius, so your inertia carries you outward

user54412

the reverse happens if you are more than 1 AU from the sun

Crazy Buddy

4:48 PM

@ChrisWhite What bugs me is the L2 -_-

user54412

@ManishEarth by minimizing beating or something?

Crazy Buddy

Dinner, then Chris' answer, and finally chat touch-up... C'yall later :)

David Z

See you @CrazyBuddy

user54412

@CrazyBuddy I think L2 is the most complicated :P

user54412

cya

ManishEarth

4:51 PM

@ChrisWhite That's one way, but I haven't got to that yet (I plan to). There's some interesting (chaotic) behavior when I just plot $\int\limits_0^{n\pi} (flute(x)+flute(kx))^2 dx$ as a function of k and then vary n. It's a sort of chaos that isn't really that chaotic, but it's interesting

user54412

flute(x)

user54412

?

user54412

$\sum_j \alpha_j \sin(j x)$? with $\{\alpha_j\}$ chosen to give the right timbre?

David Z

Anyway... it's technically end-of-chat-session time (no need to stop talking though), so thanks everyone for coming and see you in two weeks! When maybe we'll have an actual topic of discussion.

user54412

@ManishEarth well, when your analysis is advanced enough, I've always been interested in inversions - raising or lowering some notes in a chord by an octave to change their ordering

ManishEarth

5:01 PM

@ChrisWhite as in?

@ChrisWhite yeah

user54412

like, most cultures seem to think a perfect fifth (higher note is 3/2 \approx 2^(7/12) the frequency of the lower one) is just great

ManishEarth

@ChrisWhite But I'm going to later record some sounds (flute, voice, violin, etc), take their fourier transform, and get better waveforms out of that

user54412

but the perfect fourth is not quite so popular afaict

user54412

actually, the perfect fourth was more popular than it is today in, e.g., the European Renaissance, but that fad didn't last for some reason

ManishEarth

fourth as in Fa?

Still quite popular in Indian music

user54412

5:06 PM

@RhysW You missed the best title on the entire Stackexchange network: How can I keep monsters out of my nether regions?

ManishEarth

Indian music is usually solo with a tanpura in the background, and the tanpura either plays a Do-Sol, Do-Fa, or Do-Mi chord

@ChrisWhite o.o

RhysW

@ChrisWhite my bad, i just took the ones from the top voted as example hoping to encourage him to find mroe fun ones :D

user54412

@ManishEarth Ah, well, Do-Fa is not unpopular in western music, but it is a bit overshadowed by Do-Sol, despite the fact that they are almost the same thing

RhysW

question

ManishEarth

@ChrisWhite In Western music they are exactly the same thing

RhysW

5:09 PM

why is physics talking about indian music? :L

ManishEarth

In Indian music they usually are, though in some ragas you take the slightly higher Ma /Fa (27/20) so it's not always

user54412

@ManishEarth well, yes, unless you care about which note is absolutely lower (i.e. break the symmetry imposed by equating all notes off by a factor of exactly 2 into the same equivalence class)

Crazy Buddy

@DavidZ C'ya later David :)

ManishEarth

@ChrisWhite I'm thinking in the symmetric loopy system :P

user54412

@ManishEarth which is great - I'm just giving you stuff to think about when your analysis gets tired of easy stuff :P

ManishEarth

5:12 PM

lol

An interesting question is, does f and 2f sound the same when applied to a sine wave?

Note that there are no harmonics.

Because sine wave

They sort of do sound nice when played together as compared to f and 1.99f or something. But that could be the beats. Another thing I want to analyse

@RhysW Music is math. And physics.

RhysW

@ManishEarth true, just dont start talking about nodes and antinodes on a vibrating string please :P

ManishEarth

Notes and antinodes in a vibrating air column then?

RhysW

no no nodes :P

user54412

@ManishEarth One of the coolest classes I took as an undergrad was an order-of-magnitude physics class, and one of the things we calculated was how close two frequencies could be to be (slightly | very) distinguishable given just the spacing of receptors in the cochlea

ManishEarth

@ChrisWhite nice!

ManishEarth

5:57 PM

@ChrisWhite I took down the Chinese data (I can easily swap it in in place of the Indian notes).

Made the graphic above because I wanted to see how they compare

Raw data:

Shrutis = {{1.25, "G1"}, {81/64, "G2"}, {254/243, "r1"}, {16/15,
    "r2"}, {10/9, "R1"}, {1.125, "R2"}, {4/3, "M1"}, {27/20,
    "M2"}, {45/32, "m1"}, {729/512, "m2"}, {1.5, "P"}, {5/3,
    "D1"}, {27/16, "D2"}, {128/81, "d1"}, {8/5, "d2"}, {15/8,
    "N1"}, {9/5, "n2"}, {16/9, "n1"}, {6/5, "g2"}, {32/27,
    "g1"}, {243/128, "N2"}};
Wa = 2^(1/12); Western = {{Wa, "D\[Flat]"}, {Wa^2, "D"}, {Wa^3,
   "E\[Flat]"}, {Wa^4, "E"}, {Wa^5, "F"}, {Wa^6, "G\[Flat]"}, {Wa^7,
   "G"}, {Wa^8, "A\[Flat]"}, {Wa^9, "B\[Flat]"}, {Wa^10, "B"}, {Wa^11,

user54412

6:32 PM

@ManishEarth very cool!

ManishEarth

6:45 PM

Had an F-15 Instructor pilot explain to me what keeps airplanes in the air. That is money and gasoline. Neither money nor gasoline care which way up is. And that is why some planes can fly inverted and others can't. Money (design) and gasoline (engine) — Jerry Oct 21 '11 at 1:53

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