The h Bar

12:24 AM

@JakeRose The double negative there is kinda confusing. If you mean why is the other half of the hoop not shown, it's because they are showing how the stress is derived, they didn't even need to take a half section, they could have taken a tiny slice to show that stress, what's important is the direction it acts

user351417

1:50 AM

@Blue Yeah, I'll echo what ACM said... let's leave it around for a bit. I was hoping @DavidZ could edit that last part of it, but the issue can wait for even a couple of weeks. The H Bar has looked quite calm for a while, and I haven't seen anyone missing anything other than "don't ask about asking, just ask", which isn't a problem at all.

user351417

2:06 AM

@ACuriousMind nooooooooooooooo.com

David Z

2:45 AM

I put faq-proposed on it

but yeah, we can leave it for another week

user351417

3:01 AM

Thanks!

user351417

4:01 AM

Are the review queues down? They don't seem to be loading, for no apparent reason.

user351417

Huh, never mind. It looks like my browser's messing something up. It works on Edge but not on chrome. It's usually the other way around.

vzn

5:07 AM

@Chair "calm"? the ultimate calm is an empty room o_O :P

Slereah

8:45 AM

Morning

Slereah

9:49 AM

I have this uneasy feeling that half the papers involving the Curzon metrics or other Weyl coordinates are nonsense

I hope that is not the case

Like there's a lot of confusion between the actual metric and the weird Newtonian analogue

I'm not sure the Newtonian analogue should really be talked about at all because it has basically nothing to do with the actual metric

It's more confusing than anything else

user8718165

Hello sir @John Rennie

John Rennie

@user8718165 hi :-)

What did you want to ask about light?

user8718165

10:04 AM

yes sir, just typing it in

Sir the speed of light depends upon gravitational force and the nature of medium...

Im not sure about this statement

John Rennie

@user8718165 Can you go into more detail? What specifically are you unsure about? For example the speed of light in a medium is c divided by the refractive index.

user8718165

I wanted to know that if light bends around massive bodies like the sun.

and does the speed of light change during this phenomenon?

John Rennie

@user8718165 how the speed of light changes in a gravitational field turns out to be quite complicated, but we can take a rather simplified view and say that the speed of light reduces as the light gets closer to the Sun.

So it's a bit like the refractive index of space increasing as the light gets nearer to the Sun. So the light bends round the Sun as if it were passing through a spherical lens that has a refractive index increasing as you get nearer the centre.

user8718165

And sir what happens when it just bends and passes by? I mean does the speed become the same as in vacuum after passing by ?

John Rennie

10:22 AM

Yes. The light slows down as it approaches the Sun then speeds up again as it heads away from the Sun. As it gets far from the Sun it goes back to travelling at c.

user8718165

Ok sir thank you very much.

Slereah

lol "sir"

have you been knighted yet @JohnRennie

John Rennie

@Slereah :-) It's just the standard way to address teachers in India

A lot of the Indian students call me "sir" until I can break them of the habit :-)

Slereah

break out the spray bottle

Avnish Kabaj

10:40 AM

@JohnRennie So in uk etc etc the teacher-students are on first name basis?

John Rennie

@AvnishKabaj as I recall we used to call our teachers "sir" as well. But I'm not a teacher, just a fellow physics nerd :-)

Slereah

Herr Doktor Professor

Avnish Kabaj

@JohnRennie oh

I see

John Rennie

You can call me anything that won't get you banned from the chat :-)

Slereah

@JohnRennie Your mother was a hamster and your father smelt of elderberry

2

John Rennie

10:45 AM

@Slereah I fart in your general direction

(how we laughed :-)

Captain Bohemian

@JohnRennie you even called your female teacher sir?

John Rennie

@CaptainBohemian I honestly can't remember what we called the female teachers, but then it was 40 years ago

"miss" I think - even the married ones.

Captain Bohemian

we always call our teachers teacher, whether they are male or female

John Rennie

@CaptainBohemian I don't know what the convention is in UK schools these days.

Captain Bohemian

I don't know how to call teacher in English--calling them teacher seems strange. I used to often call my USA advisor teacher, but he doesn't correct me.

Maybe I should I call him professor, but I feel that call too solemn.

how should we call researchers? There seems not to be a way to call them. They are neither professors nor teachers.

Slereah

10:54 AM

Doctor, presumably

or "you"

depending on your level of deference

Captain Bohemian

I feel fine to call my ex-advisor who is a researcher not too older than me his name, but I don't feel fine to call researchers their name directly if they are far older than me.

Slereah

So can someone access this : researchgate.net/publication/…

They still haven't sent me a copy of it

And I don't know if that stuff is available in another paper

Anonymous

11:42 AM

@Slereah Ask as a reference request on Math Overflow perhaps? I searched for a bit and that paper doesn't seem to be available anywhere online. BTW it seems to have been last cited in November 2018. You could try mailing those authors too; they might have a copy. :P

Anonymous

books.google.co.in/books/about/…

Anonymous

> Digitized 15 May 2015

Anonymous

The UC Berkeley library should have a copy then...

Anonymous

> Berkeley University of California Electronics Research Laboratory

Anonymous

Huh, that book is text searchable. Try searching for "manifold" for example. Should be possible to download a part of it at least.

Slereah

12:49 PM

npr.org/sections/goatsandsoda/2019/01/09/683298815/…

whew

Captain Bohemian

I don't like searching, which is one of the most demanding things in the world.

Jake Rose

2:06 PM

Does anybody understand this integral to get the force?

Slereah

2:53 PM

Who writes Minkowski space as $$d\xi^2 + d\eta^2 + d\zeta^2 - d\tau^2$$

Damn you Israel

The physicist, not the country

Sir Cumference

Slereah

och och och

Oh Javascript

Anonymous

@SirCumference LOL. Let's see...I'll try that next time I visit the coffee shop. :P

Secret

4:03 PM

PhD chemistry:
f888 hate carriage returns. whenever they show up in linux code, they do all sorts of weird things. for example:

If the variable \$k contains a carriage return, then e.g. echo stuff\$k.xyz gives:

.xyzf

Anonymous

@Zerix Ah...that Mangekyou shining through the cut on the eyelid is a bit...scary. More so in a 3D animation. :)

Secret

that is, those carriage returns somehow caused the character after it to be translated to the beginning of trhe string, and then eat that string

Zerix

@Blue that was one of the reasons I put this as pfp xD

John Rennie

5:08 PM

@Secret no, that's just the way the string is displayed. On a VT100 or similar the CR character moves the cursor back to beginning of the line. It's just a display issue.

Secret

Ah I see

John Rennie

On that sort of terminal a LF character just moves the cursor down one line i.e. echo "abc\ndef" would produce:

abc
   def

A terminal will require CR then LF to start a new line at the first column.

Which is why MS-DOS used CRLF to terminate a line.

Student404Mus

Hey :49149880 i think i got it! if the initial state for example was in superposition |ψ⟩=α|0⟩+β|0⟩. After measurement (the classical result or the certain result) is definitely |0⟩ or |1⟩. Hence you can't go back because the measurement had occurred.

In addition to this, quantum gates are evolutionary gates that 's to say if we apply them again in a reverse they give the same result or more precisely the same initial state. Thus, quantum gates have nothing to do with measurement and we would explained the desired point.

Anonymous

@Student404Mus That's correct. I don't know what you mean by "quantum gates are evolutionary gates", but they certainly are unitary. :)

Student404Mus

@Blue and sorry . Because nobody explained for me the conflict of measurement and gates

i mean unitary operators

Anonymous

5:15 PM

I think you should dump Wilde's textbook. If it didn't teach you these basics in the first couple of chapters, it's useless. :P

Anonymous

There are better sources to learn the basics of quantum computing and linear algebra from.

Student404Mus

indeed

Anonymous

When I first started I referred to Vazirani's lectures. Those were pretty helpful.

Anonymous

They're on YouTube.

Student404Mus

Ah! that's great

thank you

i didn't notice

my bad English gets me in trouble whence my questions being not clear to people

Anonymous

5:30 PM

@Student404Mus Something like Grammarly might be helpful for you? My English wasn't good either when I first joined SE. It has improved a bit over time. Making a conscious effort helps.

Anonymous

There's also this:

Anonymous

vzn

in theory salon, 2 mins ago, by vzn

DO NEURAL NETS DREAM OF ELECTRIC HOBBITS? / GPT-2 AS STEP TOWARD GENERAL INTELLIGENCE / alexander

Sir Cumference

5:45 PM

I'm starting to think a lot of the "hints" Spivak gives for his problems are just red herrings

Anonymous

BTW Vazirani does need a good haircut...

Anonymous

Also, the guy staring at him when he's speaking...is just creepy (heh, his name is Guy Rothblum). :P

Anonymous

Anyway...Simon's Institute is doing some cool work, apparently.

ACuriousMind

@Slereah Ah, yes, Javascript's "type system". It's...not very good.

It's also famously responsible for == not being transitive or symmetric.

Student404Mus

6:12 PM

@Blue i see

thanks for your help Blue

Anonymous

'nytime! :)

Anonymous

Hmm, this song has a nice rhythm.

danielunderwood

6:31 PM

@Slereah weren't those the coordinates Einstein originally used for SR (though not in tensor form)? I remember reading the paper and hating the coordinates that were used

Actually maybe not...looks like he just used them for the second frame when comparing two frames

Sir Cumference

@ACuriousMind I'm pretty sure it's symmetric, though yeah not transitive

Could be wrong tho

ACuriousMind

Looking it up, the spec says it's symmetric, but you can find some implementations where it isn't, cf. stackoverflow.com/q/5669440/3929857

Sir Cumference

Honestly I don't understand the rationale for making languages weakly typed

ACuriousMind

@SirCumference Strong typing usually requires explicit typed declarations of variables. For a "scripting language", that's seen as unnecessary "clutter". Also, strong typing in object-oriented languages requires the use of interface-like types (e.g. C++/Java's interfaces, Rust's traits) in method signatures for objects, introducing more "clutter" you don't want to deal with when you're just hacking together a quick script

It's so much easier to write a Python function that accepts anything and just tries to call a method with a particular name on it instead of having to construct a coherent interface having that method.

Sir Cumference

@ACuriousMind I mean yeah it reduces "clutter", but can sacrifice functionality. At the very least I'm surprised that a lot of industry standards, e.g. JS for web development, are weakly typed.

If it were casual/quick scripts, yeah I'd understand

ACuriousMind

6:44 PM

@SirCumference JS was explicitly intended to be used by people without much programming experience

Type systems are hard to wrap your head around when you see them for the very first time

(If you think types are easy, then you've just gotten used to them, as one does)

Sir Cumference

I know, but it likely isn't going to be the hardest thing to learn when you first start programming. Seems like a pretty serious thing for a language to discard

ACuriousMind

It also makes APIs much easier to use, as I said. Using different APIs from different authors in a strong, statically typed language tends to require a lot of tedious casting

I'm not saying this makes weak/dynamic typing better (also, there's no clear cut definition of these terms), I'm just saying it's not as one-sided as you might think.

If you take a really strong type system like Haskell's or Rust's as comparison, you can also claim C has "weak typing" - it allows you to dereference the null pointer!

It has runtime errors!

The horror!

Sir Cumference

I suppose so. Though ultimately the general response seems to be quite negative for weak-typing languages, take JS as an example. Seems odd that they'd still be so prominent

ACuriousMind

@SirCumference Look at how many people love Python. They hate JS because it's a terrible language, not because it's weakly or dynamically typed :P

Sir Cumference

Fair enough lol

danielunderwood

6:59 PM

Python good, JS bad!

(also 20 nested callback functions very bad)

Though I've heard that JS was designed and implemented in some number of weeks in a way that was meant to be flexible

ACuriousMind

To me the strongest argument for strongly and statically typed languages has become the IDE support

Autocompletion and refactoring assists are so much better in these languages

bolbteppa

@Slereah cardiff.ac.uk/study/postgraduate/research/programmes/project/… simonwood.eu/phdproject

danielunderwood

Yeah they do have better IDE support. Especially when languages like python or ruby also let you go in and dynamically manipulate classes themselves

Curio

8:35 PM

Does Raoult's law contain the degree of dissociation?

Secret

11:59 PM

nature.com/articles/s41550-018-0602-1

Different bkackhole definitions

Transcript for