The h Bar - 2018-10-17 (page 1 of 3)

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6:59 AM

Nonsense of the day:

0

A: Do matching (left/right) lights often burn out within a short time period of each other? If so, why?

In my experience, the right one tends to be the one to give out first. This is natural, with it being nearer the side of the road where it's darker, so it will have the most work to do. That is also why the other one will give out soon after, as it will then have twice as much darkness to dispel ...

The right light of your car does more work. sigh

"the other one will give out soon after, as it will then have twice as much darkness to dispel"

7:17 AM

> This is the Physics SE not the Jokes SE

I'm no expert but that seems like Mechanics SE

Anonymous

@KlaymenDK this is the Physics SE not the Jokes SE. The point of answers here is to be helpful to anyone working in or studying physics. — John Rennie 6 mins ago

Anonymous

Is this a joke about a joke? ^

Anonymous

@SirCumference :P

Anonymous

Well, that's bound to happen when you make all the sites look too similar

@Blue Lowkey dissing the new design eh?

7:22 AM

@Blue we are not amused

Anonymous

@JohnRennie You wrote "this is the Physics SE" on mechanics.stackexchange.com ;)

Anonymous

13

Q: Do matching (left/right) lights often burn out within a short time period of each other? If so, why?

A couple of weeks ago, the right headlight in my car burnt out, so I went to the garage and had it fixed. When I picked up my car, their salesnerd told me to watch my left headlight, for "once one headlight burns out, the other often follows in short order". At first, I found that statement a li...

headlight kia rio

JR is living in the days where physics was all mechanics I guess?

@Blue ah, I just assumed it was on our SE

Fortunately comments can be deleted without leaving any trace :-)

Anonymous

@SirCumference I like the new design but it sorta feels like the sites have lost their individualities, although that's probably the exact thing SE was aimed at anyway (to make site-wide updates easier)

Anonymous

7:26 AM

@JohnRennie Heh :P

Anonymous

I so wish to have the power to edit comments! They could roll it out as a rep-based privilege. Imagine having OCD and not being able to correct the spelling error in your previous comment XD

@Blue It just rubs me the wrong way how they paid little attention to the community's response

It was pretty clear most people were against the changes

Anonymous

@SirCumference Well, it's like any other for-profit company....

@SirCumference people tend to ignore the fact the SE provides its sites for free. The change was made to reduce maintenance costs. If everyone was willing to pay a subscription then I'm sure the SE would be willing to provide any themes we wanted. Not that I'm necessarily accusing the moaners of being ungrateful bastards but ...

Anonymous

That is very true. We tend to take all the good things for granted

Anonymous

7:39 AM

(but, well, criticism is a fun passtime anyway)

@JohnRennie I wasn't aware of the reason, you have a source?

Anonymous

Ah, it sure was discussed on meta SE

@SirCumference it's in a post about the changes on the SE meta somewhere

Maybe I'm blind then

Anonymous

139

Q: Ch-ch-ch-changes: Left nav, responsive design, & themes

Thanks everyone for your feedback. The team has responded to feedback in the post Left nav, responsive design, and theming next steps . Check it out. Ch-ch-ch-changes are coming. As you've hopefully read in our various posts on Teams, we are in the midst of some major work. We're introduci...

discussion design navigation announcements

7:41 AM

But isn't SO one of the top 50 sites in the world, and the goto for programmers? You'd think they'd get a lot of revenue from that, at least some of which could account for the themes

@SirCumference Blind and ungrateful? That's a hell of a lifestyle choice :-)

Oh give me a break :P If I could donate to the site I definitely would've by now

Anonymous

@SirCumference Attractive site designs are indulgences (although people on TeX SE might disagree) and not necessities. SO is business-smart enough not to spend unnecessarily on indulgences ;)

Just because I question the design choices of a website doesn't mean I'm ungrateful

Anonymous

Although some of their decisions haven't struck me as business smart lately

7:44 AM

@SirCumference If I caused offense I'm sorry. It wasn't intended to be taken seriously.

@Blue Yeah, perhaps they don't need ultra-luxuries ones, but as you've said they've largely removed the individuality from sites

@JohnRennie Semi-got that idea with the ":-)" in your comment, but I think I'm too tired to process the tone here :/

At any rate I think I ought to head off. 'Night

Anonymous

Good night!

Anonymous

@JohnRennie The h Bar is missing your food pics, for over a month now!

@Blue The h bar has got more physics focused recently, which I think is a good thing and has improved it. So I'm not sure how appropriate it is to post food pictures any more. Maybe if I have a really spectacular meal :-)

Anonymous

8:02 AM

Duh, everyone likes to have a glance at food pics, and more so when talking about physics ;) We'll be waiting!

Anonymous

On another note, it's Durga puja time here and I'm getting to taste a lot of new stuff. Yesterday we visited a Thai restaurant and they probably had the best soup I ever tasted:

Anonymous

Tom yum or tom yam (UK: , US: ; Thai: ต้มยำ, RTGS: tom yam [tôm jām] ( listen)) is a type of hot and sour Thai soup, usually cooked with shrimp (prawn). Tom yum has its origin in Thailand. In recent years, tom yum has been popularised around the world. The words "tom yam" are derived from two Thai words. Tom refers to the boiling process, while yam refers to a Thai spicy and sour salad. Indeed, tom yum is characterised by its distinct hot and sour flavours, with fragrant spices and herbs generously used in the broth. The basic broth is made of stock and fresh ingredients such as lemongrass, kaffir...

Anonymous

I guess I've become a Thai food fanboy now :D They taste very fresh and not too heavy on the stomach

8:14 AM

I spent a few weeks working in Thailand. Eating in the local cafes I found that the food was very, very hot for Western palettes. The hot and sour soup was almost undrinkably hot. The spicing was milder in the expensive restaurants but my Thai friends tended to dismiss these as "food for tourists" and not real Thai food.

Anonymous

Ah. I guess almost anywhere in the Asian countries: the local restaurant food is not quite representative of the traditional (homemade) cuisine. Even in India, unless you visit the really expensive restaurants you wouldn't quite get the real taste of say biryani or kosha mangsho. The local restaurants will either make them too spicy or too "watery". It does take a lot of skill to prepare the traditional dishes right!

Anonymous

My grandma used to be great at cooking traditional dishes, while my mom....not so much (but then she has kids to look after and I can't blame her)

8:30 AM

ψ(x)=e^ix -0.5≤x≤0.5

is this wave function normalized?

Anonymous

@ostrichguy Compare with the condition for normalization....

i did but i dont get any answers. please check if its squared modulus within the limits yielld 1

Anonymous

Sorry, we don't solve homework problems here. You'll need to elaborate the steps you took to solve the problem. We'll help you out from the step where you are getting stuck.

@ostrichguy do you mean $\psi(x) = 0$ for $x < -0.5$ and $x > 0.5$ and equal to $e^{ix}$ within that range?

yup

i just need to check if it is normalized or not

8:34 AM

Just integrate $\psi^*\psi$ from $x = -0.5 \to 0.5$ and see

Actually given that $|\psi| = 1$ that's a rather easy integral to do :-)

psi is not 1. It had to be normalized first na?
ψ(x)=e^ix. question is if it is normalized or not within -0.5 to +0.5

@ostrichguy $|\psi|^2 = \psi^*\psi = e^{-ix} e^{ix} = 1$

so it is normaized isnt it?

It is

even within the range -0.5 to +0.5 ?

8:42 AM

Help coworkers are talking about cosmology

and it's all dumb

@ostrichguy $$ \int_{-0.5}^{+0.5} 1.dx = 1 $$

Thanks a lot.

Anonymous

@Slereah The web developer co-workers? :D

@Slereah the lot of the theoretical physicist

Yes

Anonymous

8:44 AM

lolol

Damn normies

Actually I've found people are very interested to hear from real physicists, provided you don't beat them about the head with your erudition.

And now they're talking about warp drives

I am boiling

Tell them about the alcobeer drive. You drink ten pints of strong lager and it warps you.

Anonymous

@JohnRennie (...as long as their beliefs are not shattered) :)

8:48 AM

@Blue to be fair, most of their beliefs have probably come from a Michio Kaku or Brian Greene pop science broadcast and they aren't entirely divorced from reality. It's just that things get jazzed up for the TV.

they get jazzed up in Madonna songs also re: "quicker than a ray of light..."

Ah, the Ray of Light album. One of her best I think.

yup, I concur

Sorry if im bothering
ψ(x)= (8/pi)^1/4 e^-4(x^2) is this wave function normalized within -infinite to +infinite ?

So the condition for normalisation is $\int \psi^*\psi = 1$ and in this case $\psi$ is real so we get:

$$ \sqrt{\frac{8}{\pi}} \int_{-\infty}^\infty e^{-8x^2} dx $$

9:03 AM

that doesn't make 1 obviously

$\int e^{-ax^2}$ is a standard integral that you can easily Google.

$$ \int_{-\infty}^\infty e^{-ax^2} dx = \sqrt{\frac{\pi}{a}} $$

@Slereah why boil about that?

pop science :p

pop sci can be unpopularized by math :p

while, the only pop math would be recreational; I believe

9:22 AM

there's plenty of pop math and it's all mostly useless shit

9:44 AM

when am I going to use this?

Saying "Avogadro's Number" Avogadro's Number of Times (World Record)

an Avogadro-plex

In other news, I wonder what is the current progress in warp drive research. Haven't heard anything ever since that warpfield eaglelabs experiment

and the EM drive seemed to be shot down again due to thermal error stuff

I'm pretty sure it's a hoodwink

A swindle

A snooker

A chouse

A bilk

Also, macroscopic extra spatial dimensions are ruled out (largely)

How to Detect Extra Dimensions | Space Time

(see relevant paper if the PBS spacetime is too pop sciency)

9:53 AM

A bamboozle

Safe to say our reality is like the most mundane in existence

@Secret the Higgs mass is a bit weird ...

Yeah, it is unbelievably light. This and neutrino oscillation seemed to be our best bet on finding new physics

Almost everything else seemed to follow well the standard model though

Have you read Jim Baggot's book called Mass? @JohnRennie

The Concept of Mass - with Jim Baggott

I think he's a chemist.

@user2236 no

I have a few of his books, but not that one.

10:07 AM

Good news, one down, 132 sites to go: interpersonal.meta.stackexchange.com/q/3330/543

and the bad news can be found by checking the newest proposals in Area 51 :P

10:26 AM

@JohnRennie It worked, it worked!

@SwapnilDas cool :-)

Thanks a lot!

The Physics Stack Exchange IT Support Service strikes again!

amazon.co.uk/Quantum-Space-Gravity-Structure-Universe/dp/…

^his latest :-)

By a chemist?...

10:32 AM

Chemical physicist

ohk.

Is he a good writer?

I have to confess I lost interest in popular physics books when I first started to understand GR and QM. These days I still read popular science books if they are about biology, geology, archaeology or some other field that I know little about.

You can listen to him on YouTube above @SwapnilDas

@JohnRennie Have you read 'Elegant Universe' by Brian Greene?

@SwapnilDas yes, when it was first published. Actually I still think that's a good book even now that I know (a little) more about string theory.

10:36 AM

Does it have anecdotes about scientists like witten?

To some extent. It's mostly about the science though.

I really like those books which contain anecdotes.

Great then.

I'll buy it.

@JohnRennie Is there any other introduction to string theory book available (on a pop sci level) ?

@SwapnilDas there must be thousands of pop science books about string theory. The trouble is that they will present at best a caricature because the maths involved is just so intimidating.

Does Greene talk about the math involved or just tells stories?

@SwapnilDas he talks about the math to some extent, but only in a superficial way.

10:42 AM

Hmm, fine.

docs.google.com/document/d/… I can only buy the book if the total goes above 3000, wish me luck!

Good luck!

Ty :P

That's the no. of problems I solve everyday. I've to make it 3000 in the month.

What's the best scientific calculator for physics?

By best I mean, "a calculator that would increase my performance the most", so it should definitely have physical constants and the most common functions (Trigonometrics, Exponentials, Hyperbolics, unit conversion)

Anonymous

@SwapnilDas There is....by Zwiebach. I haven't read it tho

Anonymous

Iirc it was more of an "undergrad intro"

Anonymous

10:51 AM

amazon.com/First-Course-String-Theory-2nd/dp/0521880327

11:01 AM

I have the book, and it's not a pop sci book. It's more of a final year of a physics degree book.

Susskind talks about what he couldn't find on the web about Feynman

Anonymous

@JohnRennie I can understand, although I don't know if anything at a lower level that would be useful in any way other than passive entertainment :P I wanted to read it for a while when I found this associated lecture series: youtube.com/playlist?list=PLFMKfDJ8QzbN2ls29L0Ij_Ei7E_FxiYRE

Anonymous

In any case, is the book good from what you read? :)

I don't know enough about string theory to judge, but I think it's generally regarded as pretty good.

Anonymous

I'll probably have a go at it (and the QFT for amateurs book) once I'm over with Schuller's notes. I guess these kind of books are pretty heavy investments on time tho, especially when self-studying :)

11:10 AM

@Blue I suspect you need a good understanding of QFT before you'll get much from a string theory book.

Anonymous

@JohnRennie Ah, I see

Most string theory courses have QFT as a prerequisite.

when do you have to choose your specialization in college?

Anonymous

Makes sense. I'll try the QFT book first then

@Blue Lancaster and Blundell?

Anonymous

11:13 AM

@JohnRennie Yup

Anonymous

(do let me know if it's a bad idea :P)

Anonymous

Anyhow, none of these are immediate goals. I just read physics texts during my holidays. So it's probably gonna take a few years

I bought the book but I must admit I have done no more than glance at the first chapter. I haven't had the time, or to be honest the motivation, to start reading it seriously.

Anonymous

@user2236 Me?

yup

Anonymous

11:15 AM

@user2236 Next year

Anonymous

(3rd)

icic

Anonymous

It's not much of a choice tbh....an analog circuits specialization and a computer engineering specialization

Anonymous

More than 90% of the class will pick the latter

Analog circuits doesn't sound that much fun ...

Anonymous

11:21 AM

Indeed. Transistors already feature in my nightmares....so I dare not....

wow! That's a lot of competition for computer eng.

11:48 AM

\o @DavidZ

12:11 PM

Can anyone please take a look at this question: physics.stackexchange.com/questions/435110/…

$$\int \text{Question} = \text{answer} \neq \text{ANSWER}$$

Can anyone tell me whether this is realistic? I asked on Worldbuilding, but the general consensus was that it would require a PhD to answer. I just want to see if anyone here can give me feedback on it before I give up. worldbuilding.meta.stackexchange.com/a/6806/54384

1:11 PM

@Blue I didn't like the presentation of that book too much..

Anonymous

@Avantgarde What do you recommend instead?

@Blue Can you attend actual lectures?

Anonymous

@Avantgarde Not feasible. At least, not in the near future

Anonymous

I'm in no hurry though

@Blue Ok. I think going through some lectures first would be better (and faster). You could try the PIRSA website for that.

Anonymous

1:15 PM

@Avantgarde Yes, I'm aware of the Perimeter lectures. I'll see :)

@Blue Same. Analog sucks.

Yeah I recall Cachazo has lectures on QFT1. He's very good (though I only skimmed through the first lecture long ago)

The problem with books like "Gifted Amateur.." is that they're too watered-down throughout to make coherent sense. But anyway, that was my impression.

Anonymous

@Avantgarde I see

Anonymous

That makes sense, and I was sorta expecting that that would be the case

Anonymous

But looking at the reviews I was sort of neutral

1:44 PM

Let's make a Good QFT Book

From the ground up

Build the bloody Fock space

building a good book from the ground up is a monumental project

I know

Trying to do it for GR

It is quite an undertaking

they're trying to do it over in the homotopy theory room also

in Homotopy Theory, 16 hours ago, by Dylan Wilson

ohhhhh jeeez : https://kerodon.net/

from the ground up, I mean

I mean it's not quite from the ground up because I'm not gonna try to prove every bloody analysis theorems involved

But I'm trying not to rely on other GR books

icic

1:56 PM

Did you know there's a theorem proving that spacetimes can only exist if the manifold if it's either non-compact or compact with Euler characteristic 0

And that theorem was proven only once

It has literally never been proven again since 1952

Every GR book just references that proof

wow! TIL

There's a bunch of those theorems

That are proven once

and that's it

Like the proof that the Godel spacetime can't be foliated by spacelike hypersurfaces

I think Godel redefined what "proof" really means in mathematics

Not really

2:11 PM

I mean in the big picture it will always be incomplete.

I mean sure

But that's not really relevent here

random thought: If our spacetime can be described in terms of hyperreals instead of reals, it probably will not make much of a difference because our measurement precision can never get down that far into the infintesimals

how so is it not relevant here?

But surely there should be "aggregates" of infintesimals in a certain way such that the resulting microscopic phenomenon differs from anything that can potentially be described by real numbers....?

Because it's a proof from Gödel unrelated to his work in that area

2:17 PM

But then if infintesimals exists, what will be the implication when such concepts interact with quanutm mechanics...?

ok

user image

3

2:34 PM

@Slereah why even use a Fock space :p

Need to include that too

@bolbteppa Free theory baby

People never seem to actually really explain the Fock space

I had to look up how it's actually constructed

2:51 PM

I prefer to use the operator space directly, but then crazy numerical hell

Even quanutm computing cannot have infinite parallisation (because ultimately how similar two state vectors are are subjected to how fast can the laser pulse be set

thus there is nonzero separation between any two nearby superposition states

vzn, 2270: O and don't worry if the above sounds a bit like SCP-055, because the fact it is antimemetic means it will play a role in the Saturday election, or maybe even the mid terms in 7 November

That's the price they have to pay to stay hidden, so to speak, and it is a law of nature that they cannot get away from it

Btw that youtube crashed yesterday, that the economy is going to crash and that we only have 12 years to save the climate means The Plan is going smoothly as expected

It all dates back to the Ultimate answer, the 42 of noncorrespondance, and because of that, they will all [data expunged]

So yeah, let them have their last, because after that, there won't be anything left

(I think I read too many SCPs)

Anyway context, especially that line between SCP-3125 and marion

> "Ideas can be killed," she says, stepping into the airlock.
"How?"
"With better ideas."

I repeat:

Ideas can be killed

Or more accurately

$$\Huge{\text{Ideas and metaphysics can not only be blocked, they can be ERASED FROM EXISTENCE}}$$

Anonymous

3:18 PM

@Secret Let's hope that doesn't get flagged for spam :P

lol

I get very unstable whenevr Slereah is nearby (or more accurately, Slereah under the effect of SCP-055)

it's been a while

@Secret Oh jesus what the hell

@Loong that is an excellent find

sir cumference: got pwned, that's what

3:26 PM

I almost burst out laughing in lecture because of this

lol

hi

@EmilioPisanty I finally remembered to look it up before leaving work.

@Loong your work pays for ISO standards?

yes

3:30 PM

fancypants schmancypants

so

you arranged for ISO to earn forty bucks' worth of BS?

OK, it's closer to thirty bucks

I think it's some general contract. I don't think that we have to pay for each individual download.

hopefully

Anonymous

user image

Anonymous

Bug?

Anonymous

(repeated questions in "New feed items")

3:52 PM

BTW, can a mod or room owner remove the format-breaking MathJax from the star board?

hmmm

@EmilioPisanty with one flex of his mighty moderatorial thews John springs into action.

@JohnRennie what's a "thew"?

wait, that wasn't a typo?

@EmilioPisanty a tendon

bejeesus

the English language, sometimes....

3:57 PM

@EmilioPisanty it's a somewhat archaic word these days. Much loved of pulp era science fiction, a genre for which I have a weakness.

ah

so basically you're saying that you like archaic words

is OK

I get

a thew = a tendon?

@EmilioPisanty I'm British. We like archaic everything.

til

@JohnRennie I lived in Britain for >4 years. You lot like archaic stuff for sure, but nowhere near that much.

btw, speaking of

what's this I hear about DUP voting down the budget?

man, that'd be mighty interesting

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