The h Bar

The (American) college system caters to the lowest common denominator, for better or for worse. If something is below your level, pass out of it, or skip lectures and just ace the exam, and move on with other things. It's less stressful that way.

0celo7

12:17 AM

the homework itself is much more challenging

HDE 226868

@0celo7 Okay, that makes more sense.

0celo7

@ChrisWhite didn't we go over this? I asked to get out of it, they said "no, no exceptions"

ACuriousMind

...what's a "reading quiz", and why does it make sense that it has stupid questions?

0celo7

@ACuriousMind it's like 3% of the grade, no clue why they do it

DanielSank

@0celo7 FWIW I broke a lot of "rules" about requirements and nobody really cared. The trick in a lot of cases is to just do it.

I skipped differential equations and mathematical methods.

0celo7

12:19 AM

@DanielSank I asked my advisor and he would not even consider it

ACuriousMind

@0celo7 "it's like 3%" is not an answer to "what is it?" :D

DanielSank

@0celo7 That's stupid.

Is the rest of the course teaching you anything?

0celo7

@DanielSank "AP physics does not teach you how to be an engineer, this class does"

so this class teaches me how to ask stupid questions?

user54412

@DanielSank where were you for undergrad again? I can see this being more difficult with more red tape, and bureaucracy scales with the cube of the school size I think.

0celo7

hah

ACuriousMind

12:20 AM

"red tape"...why have you people started talking in riddles?

DanielSank

@ACuriousMind wat?

That's a standard English phrase.

0celo7

@DanielSank no...there are some projects that go really in-depth

that's about it

the book is even the same one as I used in high school

ACuriousMind

@DanielSank Never heard it before

0celo7

@ACuriousMind rot...uh...Tape

DanielSank

@ACuriousMind It means bureaucracy.

0celo7

12:22 AM

@DanielSank diff eq is a graduation requirement

ACuriousMind

@0celo7 It's rotes (Klebe-)Band in German, but that's just...tape that is red :P

@DanielSank Ah, okay

DanielSank

@ChrisWhite Yale.

0celo7

@ACuriousMind they give you 4 questions in 10 minutes that are based off of the reading. it's supposed to get you in the habit of reading the book before the lecture.

HDE 226868

@0celo7 Are they all true/false?

ACuriousMind

@0celo7 Ah, I see.

0celo7

12:24 AM

@HDE226868 no, one was "select all quantities that are scalars"

DanielSank

@0celo7 So was math methods for me. I wonder what would happen if you just skipped.

I'm not recommending skipping diff eq. though.

0celo7

@DanielSank too late to skip, I'm taking it now!

DanielSank

@0celo7 ::brain melts::

0celo7

and I like the professor, so

@DanielSank I just chat with you guys during lectures

DanielSank

@0celo7 Nice. That's usually the most important aspect of a course.

0celo7

12:25 AM

I think we're doing vectors, at least based off of the homework

@DanielSank yeah, he explained to me why a nontrivial Jacobi field that vanishes at two points does not imply there are two distinct geodesics that connect the two points

DanielSank

@0celo7 What's a Jacobi field?

0celo7

@DanielSank solution of the Jacobi equation :P

DanielSank

@0celo7 What's the Jacobi equation?

0celo7

@DanielSank if you've done any GR, it's the solution to the "geodesic deviation" equation

DanielSank

@0celo7 That sounds familiar.

0celo7

12:27 AM

infinitesimal separation vector of a geodesic congruence

DanielSank

How the crap have you done GR and you're a freshman in college?

2

0celo7

I was bored in high school

DanielSank

o_O

0celo7

Einstein Field Equations - for beginners!

►

ACuriousMind

@DanielSank I've stopped wondering about the weird path 0celo7 took through math/physics subjects a long time ago.

0celo7

12:29 AM

this video was pretty interesting

although now it's cringe worthy

DanielSank

@ACuriousMind I... don't understand how someone could acquire the math needed without a teacher or colleagues.

HDE 226868

@DanielSank That and "How the hell is he in Physics I?"

DanielSank

@HDE226868 Yes, this is disturbing.

0celo7

@HDE226868 NO EXCEPTIONS

DanielSank

@0celo7 wtf? Go to the head of undergraduate affairs in the physics department and explain that you know wtf a vector is.

0celo7

12:30 AM

although Dr. Hines said I had done some "quite impressive" work on my own

HDE 226868

One does not simply take a physics class 30-odd levels below what one is capable of.

0celo7

it's an engineering class

DanielSank

0celo7

the class is physics for engineers 1

user54412

@HDE226868 You began "one does not simply" and didn't make a meme out of it?

HDE 226868

12:31 AM

Whatever. You know the material.

DanielSank

@0celo7 Are you majoring in engineering of some kind?

0celo7

@DanielSank ACM helped quite a bit, actually

@DanielSank yeah, nuclear engineering

HDE 226868

@ChrisWhite Have you seen my meme attempts? My text clashed with the Daleks' colors last time around. It was next to unreadable.

DanielSank

@0celo7 ACM?

0celo7

@DanielSank @ACuriousMind

DanielSank

12:31 AM

@0celo7 Oh.

Cheers to @ACuriousMind. clinky clinky

0celo7

I got through Zee's GR book without ACM

ACM helped with some more advanced stuff

ACuriousMind

@0celo7 Were you not already capable of basic GR when you showed up here? I think we met because you couldn't deal with clopen sets ;)

0celo7

@ACuriousMind yup

DanielSank

What's your deal? You some kind of genius or something?

0celo7

We met because of a problem in Wald I think :D

@DanielSank Not even

DanielSank

12:33 AM

@0celo7 Then what the hell is going on?

0celo7

Have you seen some of the people like jamal

DanielSank

I still don't understand Gaussian integrals.

@0celo7 I remember him sort of.

HDE 226868

@ChrisWhite See this, the one I'm referring to. I turned someone else's quote into a meme at the request of another user:

Aug 27 at 21:00, by HDE 226868

DanielSank

And I really don't understand $dz \wedge dz^*$.

How the hell did you figure that out by yourself?

0celo7

I think I have a math SE question on that

DanielSank

12:35 AM

@0celo7 Link?

0celo7

4

Q: How do we wedge the complex differentials $\mathrm{d}z^i$ and $\mathrm{d}\bar z^{\bar j}$?

By the standard definition of the wedge product as an alternated tensor product, I would think we have $$\tag{1}\mathrm{d}z^i\wedge\mathrm{d}\bar z^{\bar j}=\mathrm{d}z^i\otimes\mathrm{d}\bar z^{\bar j}-\mathrm{d}\bar z^{\bar j}\otimes\mathrm{d}z^i$$ As I understand it, the left side should be a ...

btw, how are you just now figuring out where I am in the math/physics world

user54412

0celo7

ACM has had extended lectures trying to drill things into my head

cf. e.g. the whole clopen sets things

DanielSank

@0celo7 Uh, I guess I don't care that much...?

HDE 226868

I wonder if the legacy of J. R. R. Tolkien will just be a sea of Boromir memes.

DanielSank

12:37 AM

@0celo7 That is not meant as any sort of insult.

ACuriousMind

@HDE226868 Nope. There's also at least one with Gandalf.

DanielSank

@HDE226868 Nah. Most people probably don't know who Boromir is, despite the meme.

0celo7

I've watched the movies

don't have time for the books

HDE 226868

@DanielSank So the context is lost?

DanielSank

@0celo7 They're actually rather good.

HDE 226868

12:38 AM

@0celo7 Read the books!

DanielSank

@HDE226868 Well, just guessing.

HDE 226868

They're incredible

DanielSank

@HDE226868 Meh.

0celo7

I have too much to read1!!!!!!1111

DanielSank

@HDE226868 There is zero character development.

0celo7

12:38 AM

screw it all

I'm gonna play some video games

HDE 226868

I've only read The Hobbit and The Lord of the Rings; I've got The Silmarillion on my reading list.

0celo7

@DanielSank what is there to understand

DanielSank

@HDE226868 There's maybe 1.5 female characters.

HDE 226868

@DanielSank The world he made is just amazing, though.

ACuriousMind

Mar 18 at 2:44, by ACuriousMind

@StanShunpike No. While liking fantasy, I never got to like Tolkien, I find his writing style tedious and boring, and the black-and-white morality also gets on my nerves.

DanielSank

12:39 AM

@HDE226868 Yes it is.

HDE 226868

@DanielSank Counting Tom Bombadil's wife?

ACuriousMind

Deja-vu, we've had this discussion half a year ago :D

user54412

@DanielSank Meh. Mythical sagas aren't really about character development, since the characters are supposed to be manifestations of abstract ideals more often than not.

DanielSank

@HDE226868 Ok, 1.75 female characters.

HDE 226868

Arwen, Galadriel, Eowyn, whats-her-face.

DanielSank

12:39 AM

@ChrisWhite Sure.

HDE 226868

The female Sackville-Baggins.

DanielSank

@HDE226868 Jeebus, ok fine, 2 female characters.

user54412

Lobelia?

DanielSank

^ That one

HDE 226868

@ChrisWhite I can't believe you remembered that.

DanielSank

12:40 AM

@0celo7 all the things

0celo7

was she in the movies

user54412

Ungoliant and Shelob were sorta female. Not sure if that helps this case, though.

DanielSank

@0celo7 For like two seconds.

@ChrisWhite Sigh. Ok, female characters with lines.

HDE 226868

@DanielSank I had a mini debate with Duffield earlier when I was bored (I may have won; it was at least a draw), so I was in that sort of mood today. :-)

DanielSank

@HDE226868 ?

HDE 226868

12:41 AM

@DanielSank Ah, that brings the count down sizably.

DanielSank

@HDE226868 :)

HDE 226868

Most of Arwen and Eowyn's plots are about Aragorn. Except for Eowyn in battle.

Galadriel's the only cool one.

DanielSank

@HDE226868 Yeah, Eowyn is the only sort-of interesting female in the entire 1500 or whatever pages.

@HDE226868 And that.

She'd be a lot more awesome if there were more description of her rolling into Dol Guldur and wrecking the place.

0celo7

@DanielSank I kinda had to admit defeat at trying to learn strings.

DanielSank

@0celo7 Oh... pobrecito.

HDE 226868

12:43 AM

Anyway, I should most likely get going. Good night/evening/day/twilight/dawn/dusk/lunchtime/breakfast/dinnertime/suppertime/t‌eatime/that-time-in-my-profile, everyone.

user54412

@DanielSank Did you watch the final Hobbit movie yet?

HDE 226868

@DanielSank Oh, that would be awesome.

DanielSank

@HDE226868 I know, right?

HDE 226868

Screw Gandalf, let Eowyn wreck the Necromancer.

DanielSank

@ChrisWhite I watched that one scene because it was all I cared about. It was super-duper less exciting than I hoped. I wanted to see her literally like tearing the fortress down to rubble.

0celo7

12:45 AM

@DanielSank I'm just saying...I'm not a genius.

I don't even really know QFT.

DanielSank

@0celo7 You're a *@(%#^ freshman!

@0celo7 You know, with all your background you should go spend a summer in an experimental lab. You can come out of college more well rounded in theory and experiment than anyone I've ever met.

0celo7

@DanielSank There are people who are published by age 15!

DanielSank

@ChrisWhite I was envisioning some primal rage style Elvish ass kicking and a lot of Emperor Palpatine style finger lightning.

user54412

Ha. Well, maybe one day we'll get a 12-part Silmarillion, and we can see her rebelling in Valinor.

DanielSank

@ChrisWhite Yes!

HBO miniseries?

Parts of the Silmarillion would lend well to film.

user54412

12:49 AM

the kinslaying is just what HBO needs

DanielSank

@ChrisWhite ha yeah.

gtg

user1667423

2:17 AM

What is the induced metric tensor on an n-sphere in (n+1)-dimensional Cartesian coordinates?

0celo7

3:23 AM

@user1667423 there's a lot of math.SE posts for that

David Z

4:30 AM

0

Q: Physically, what causes joint pain?

I wasn't sure if there was a better site to post on with regards to this- I wasn't sure if people on the physical fitness stackexchange would give a sufficiently mechanical description. When performing an exercise, such as a squat, one can incur joint pain if performing the exercise incorrectly....

biophysics

off topic, I think, but I'd like to get at least a few community votes before closing it.

(well, ideally 4 :-P)

Danu

7:01 AM

@user1667423 Just naively using the transformation law and the expression for each of the coordinates in terms of each other will work.

Slereah

8:00 AM

hey

Slereah

8:18 AM

back at work

such sorrow

Physics Meta

8:30 AM

0

Q: What's the policy on ill-formed, laymen questions that have interesting answers?

I just bumped into this question, which was closed shortly after being posted. It was definitely a badly-written, super ambiguous question. But somebody provided a really nice answer: one that was practically useful, comprehensible to the layman, and nontrivial to nonlaymen. I feel like the comm...

discussion

David Z

11:26 AM

@Qmechanic see my comment here

John Duffield

@HDE226868 : Pah, you lost hands down because you dismissed Einstein and said understanding gravity is mere philosophy.

skill patrol

You can never win a debate with a mod.

John Duffield

Course you can.

skill patrol

how?

Secret

I found it curious why of all physics phenomenon that the principle of superposition apply, we are so good at picking apart colors

John Duffield

11:32 AM

@skill patrol : How? Just refer to the hard scientific evidence and to the peer-reviewed papers.

skill patrol

refer all you want, if you get out of hand you get suspended

John Duffield

I don't get out of hand. I'm one of the good guys.

4

skill patrol

prove it pal

John Duffield

Let's talk about some physics issue and I'll demonstrate.

skill patrol

I believe division by 0 is a physics issue because that is how instantaneous speed is defined, no?

John Duffield

11:42 AM

No. Division by zero is undefined. We've talked about that. As for speed, when you appreciate what a clock really does you appreciate that speed is defined in terms of the speed of something else.

skill patrol

What does a clock really do?

8 mins ago, by John Duffield

Let's talk about some physics issue and I'll demonstrate.

0celo7

A clock ticks and tocks.

John Duffield

A clock clocks up some kind of regular cyclical local motion and shows you some kind of count that you call "the time".

skill patrol

This "regular cyclical local motion" must be in the same location as the clock, correct?

John Duffield

Yes, it's typically inside the clock. The interior mechanism of a mechanical clock is called a movement.

A mechanical clocks is in essence just a set of gears which make the big hand and the little hand go round and round.

skill patrol

11:55 AM

Ok, so we have a space and we have a time within that space, now how do we define the instantaneous speed of an object in that spacetime?

John Duffield

Using the motion of light. You sit there and I send 9192631770 microwaves past you. You count them going by, and when you get to 9192631770 you jump up and say that's a second. Then you define the metre as the distance travelled by that light in 1/299792458th of a second.

Then you use your second and your metre to define the instantaneous speed of your object. You're expressing its speed in units derived from the motion of light.

skill patrol

I see.

John Duffield

Note that the definition of the second and the metre means the locally-measured speed of light is 299,792,458 m/s by definition. It's a tautology, Magueijo and Moffat talked about it here.

Also note that 299,792,458 m/s up by the ceiling is not the same as 299,792,458 m/s down by the floor. The seconds are different, so the speeds are different. That's what Don Koks was talking about in the GR section of this Baez article.

HDE 226868

12:26 PM

@JohnDuffield (Sigh) No to the latter, yes to the former.

@skillpatrol "Out of hand" - yes. But just because @JohnDuffield disagrees with me (and vice versa) is not a valid reason for suspension.

Let me clear something up, and I'd like people to listen:

I will not suspend John Duffield - or any other user - unless he or she commits an offense that violates the Be Nice policy (the most relevant reason here), spams chat, post inappropriate messages, or goes against any other related Stack Exchange policy, and I would appreciate it if this would not be brought up again.

I'm going to remove the star on my second message above, but I will pin the fourth if there are more suspension requests (sorry to put it like that, @skillpatrol; that sounds a bit extreme).

John Duffield

@skillpatrol : anyway, Irwin Shapiro said much the same thing: "the speed of a light wave depends on the strength of the gravitational potential along its path". But for some strange reason this sort of thing is news to physics students and PhDs.

0celo7

12:51 PM

@DanielSank I'm trying to do that...

@KyleKanos You're alive!

@DanielSank Is "topological quantum computing" a thing that actual researchers do or is that more for mathematical physicists?

@alarge I'm ordering the book you recommended from the library.

NeuroFuzzy

1:24 PM

@0celo7 re: physics.stackexchange.com/questions/203537/… angular velocity isn't proportional to angular momentum. b/c $I$ in general is a linear transformation

it actually gets really ugly. You know. ${\bf L}$ being conserved and all

0celo7

@NeuroFuzzy For a single particle it is, cf. OP's question.

NeuroFuzzy

oh, kay, just checking!!

0celo7

@NeuroFuzzy The +1 on your answer is from me

:)

NeuroFuzzy

Muchos gracias senor!

Slereah

"U.S. President Richard Nixon, when campaigning for a second term in office announced that the rate of increase of inflation was decreasing, which has been noted as "the first time a sitting president used the third derivative to advance his case for reelection.""

3

0celo7

1:31 PM

@Slereah How are you doing today?

Slereah

back at work

Could be better

0celo7

ooooh

what do you do again?

Slereah

Well I have a degree in physics

So software engineering

0celo7

Sounds boring tbh

I should spend some time and actually formulate a reading list.

Having a big file of PDFs is not very efficient.

Slereah

what topics are you looking for

0celo7

1:37 PM

I want to learn some mathy QM

But I can't do analysis

At all, I just can't do it

Slereah

it is not much fun

Did you read chapter 14 of Wald

0celo7

Tried

I "read" it, but didn't get much of the functional analysis

I have an analysis book sitting on my desk at home

but I can't do the exercises on the first pages :/

I also want to read Special Relativity in General Frames

also I want to get a feel for what quantum computing is about

Slereah

what kind of analysis stuff is it

Is it like deltas and epsilon shit

0celo7

real

Slereah

Or is it mappings of open sets and whatnot

0celo7

1:44 PM

dude I haven't even gotten to limits and I'm stuck

like "show every set bounded below has an infimum"

can't do it

Slereah

Isn't the infimum just the lower bound

FenderLesPaul

ello

Slereah

greatest lower bound, as they are called

FenderLesPaul

@0celo7 it's just about translating english definitions into $\epsilon$ format

and then playing around with inequalities

I'll help you with it soon

Slereah

There's a delta, for every epsilon

FenderLesPaul

1:46 PM

if you get a hang of it a few times then it'll become 2nd nature

Slereah

It's a fact that you can always count upon

There's a delta, for every epsilon

And now and again, there's also an N

But one condition I must give

The epislon must be positive

What a lonely live all the others live

In no theorem, a delta for them

NeuroFuzzy

@0celo7 Do you use the theorem that every set bounded above has a supremum? In which case consider the set of lower bounds of the set in question

0celo7

@NeuroFuzzy uh there's a hint and I think it says that

don't have the book on me now, in LA

Slereah

what book is it

NeuroFuzzy

@0celo7 oh cool, you should stop by SD ;o

Slereah

1:50 PM

Also visit Venice Beach

It's a weird place

0celo7

according to my sister (Studio City), your town is a shithole

no offense

or is that SF

Slereah

The shithole I visited was Bakersfield

According to a friend living there, the meth capital of California

0celo7

one of the Sans is a shithole ;D

@Slereah Carothers

it was the only analysis book the math students hadn't checked out

and two people here recommended it

Slereah

There we go

NeuroFuzzy

@0celo7 Hahaha nooo way! I've spent time in santa monica and even the really nice neighborhoods around there -- the water is gross, there's a huge homeless problem, stuff's dirty, and it takes an hour to travel five miles by car. Better beaches, better streets. In LA terms, there's no traffic :p

ACuriousMind

1:53 PM

@Slereah Posting such links in the chat is frowned upon.

NeuroFuzzy

@Slereah @ACuriousMind :(

Slereah

WHAT THING ARE YOU TALKING ABOUT

smokebomb

ACuriousMind

@0celo7 Posting racism in the chat is also frowned upon.

0celo7

@ACuriousMind Greeks aren't a race.

Slereah

Tell that to other europeans

ACuriousMind

1:55 PM

@0celo7 Your defense is seriously pulling out the dictionary?

So it's okay to generically insult groups of people as long as they are not a "race" (whatever that means)?

DanielSank

@0celo7 There are at least two different meanings of "topological quantum computing".

Slereah

@0celo7 so which problem was it?

DanielSank

One of them has to do with topological states of matter.

That, so far, is not really even close to being a reality in the lab.

The other has to do with how you take imperfect physical qubits and combine them in a way, which uses topology, to create logical qubits of much higher quality.

Typically, when you do this the error rates of the logical qubits are exponentially suppressed by the number of physical qubits per logical qubit.

It's mostly theory, but some groups have actually started getting parts of it to work.

Look up papers by Austin Fowler, Roussendorf, or even the original "toric code" paper by Kitaev (at least I think it was Kitaev).

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