2:29 AM
> HAIR
Clearly an acronym

2:59 AM
clearly

3:25 AM
Hey I messed with pytorch over the weekend. After the initial pains, it seems pretty neat. And by initial pains, I mean I’m an idiot

3:49 AM
@danielunderwood lol how many ppl can get an ML pkg to do something? so what kind of data are you working with? :)

2 hours later…
5:25 AM
@danielunderwood better than tensorflow amiright

2 hours later…
6:55 AM
Btw @DanielSank it appears there's a high chance that I'll be at a KITP workshop for several weeks next year
That's right in your neck of the woods, right?

7:29 AM
@EmilioPisanty Indeed so. I'll look forward to that.

7:46 AM
@vzn 😲😲😲

8:37 AM
morgen
@ACuriousMind All people who are interested in spacetime engineering tend to be insane rly
I won't name names but I'm thinking them very loudly :V
okay maybe I'll name them a little
this one talks about UFOs and mind powers

8:53 AM
@Slereah Harold White? To a lesser extent Matt Visser? They are lovable nutcases though i.e. they'd be great fun to chat with over a few beers.

Visser seems alright
Krasnikov seems fairly sane although he is really into it
Everytime there's a theorem forbidding wormholes/warp drives/time travel, he publishes a paper saying WAIT
Consider this counterexample!
Eric Davies seems mostly sane in what he writes but he has very suspiscious interests

Harold White has managed to get NASA to pay him to be insane, though I imagine he won't be replaced when he leaves ...

Like if an experiment of a crazy thing has negative results he will most definately say so
But he is very persuaded UFOs are a real thing
I don't want to say he's insane but he did propose to use a nuke for a wormhole experiment
A very poorly thought out one

9:41 AM

@PM2Ring I think G. Smith's answer has pretty much covered it and I don't have anything to add. Safesphere's views on GR are some way from mainstream.

@JohnRennie Fair enough. And I understand your not wanting to get into a HNQ "showdown" against Safesphere. I certainly agree that Safesphere has views on GR, and many other topics, that are some way from mainstream. And he has a very annoying habit of posting them in comments, where they can't be downvoted.

:-)

Hey @RyanUnger

It's kinda cute that Arpad is the OP. He used to annoy me with all his slightly off answers. But I get the impression that he's trying very hard to rise above the half-truths he learned from popsci. His answers are slowly getting better, and his questions seem to be focused on getting to the real physics behind the popsci myths.

10:09 AM
yo @JohnRennie
any thoughts on how to produce shiny text to describe light of multiple colours other than calling it a 'rainbow'?
I'm looking for a good sci-comm-y word for it that describes a discrete palette with a finite number of colours instead of a continuum

coruscant?
Ah, not coruscant then.
polychromatic?

@JohnRennie ugh
this is for the title of a piece that faces the general public
hence the need for "shiny" ;-)
kaleidoscopic, maybe?

I was about to suggest kaleidoscopic though that doesn't imply discrete colours.

I think I'm going to suggest just using "multicoloured"
anyways, the piece will be out in a few days, I'll post it here when it is

prismatic?

10:18 AM
:-|
for all its glories, this part of the English language is strangely... monochromatic?
=P

Polychromatic? Although that doesn't necessarily imply quantized chromaticity.

@PM2Ring "polychromatic" is poison in a headline =|

10:30 AM
I suppose so. And it could be talking about music, rather than light.

10:44 AM
I rendered that using POV-Ray a decade or so ago. If you look closely, you'll see that the colours are quantized. That's because POV-Ray's dispersion algorithm works by shooting a bunch of rays of different frequency.

11:00 AM

> Web Page Blocked!
> You have tried to access a web page which is in violation of your internet usage policy.

11:14 AM
The chatrooms have been not connecting, or very slow, for several hours.

there you go

And it's not just the rooms themselves, the transcript pages are also very slow.

2 hours later…
1:41 PM
Oh boy. The numerology guy from yesterday has been busy with the comments. physics.stackexchange.com/questions/481404/…

Anybody please...Is it possible to prove that the center of mass of the earth-moon system moves in an elliptical path around the sun using Keplers laws?

@user8718165 Assuming some approximations, yes

@Slereah thanks.. what are those approximations?

You basically have to treat it as a two body problem
well I guess technically as two two-body problems
I think you just need to assume $M_{\text{sun}} \gg M_{\text{earth}} + M_{\text{moon}}$

@Slereah we'll consider the COM of the earth-moon system as one body and the sun second...this way?

1:49 PM
basically, yes

@Slereah okay thanks!

@PM2Ring hundreds of thousands of equations? That's a lot of time & work invested...

@KyleKanos Or a whole lot of columns and rows in Excel that just multiply a bunch of things together randomly... perhaps equations is being generous

2:05 PM
That's the best way to use Excel though

It kind of all reads like those magic tricks they used to do on TV specials -- when you put your finger on your birthday or whatever, do a bunch of math, and the guy magically knows where your finger ended up

But this guy could be on to something....I mean, pi is everywhere
puts on tinfoil hat

Well, pi \approx 3 is everywhere. I think. I didn't follow it all

Well that's the problem with having so many equations, it's hard to connect the dots

I was going to come up with something clever about Excel making line plots... but I haven't had enough caffeine yet

2:11 PM
It's 10 am for me & I've been up since 5:30a. Plenty of caffeine & time to be awake for me

10am for me also. But my tolerance is too high I think
And I'm dealing with a completely jacked up supercomputer and losing my patience.

Local one? Or a national cluster?

It's going to be decommissioned in August, so they decided to do a full OS swap two weeks ago. But none of the software has been rebuilt, it's taking 5-10 minutes to save code commits so I can migrate them off the machine, and lots of drives aren't mounted like they should be
National -- one of the machines at ERDC
I've got some 13M hours I am supposed to use there before it goes down, but I can't even run/compile/do anything.

Full os swap!? From RH to SciLinux?

From SuSE to RH

2:14 PM
Suse!? Wow

My guess is their support contract ran out, and they can only renew it for longer than the few months they have left
Most of the DoD supercomputers run some flavor of SuSE enterprise.

The local cluster I was using in grad school ran SciLinux; so I installed that on my machine so that the envs would be the same

I actually used OpenSuSE forever. It's my goto desktop when I have a say in the matter...
I don't anymore, unfortunately

Supposed to be a stable distro, but it was so old that it didn't even have gcc 4

That's why I don't like RH/Fedora -- it's always so far behind

2:17 PM

I've been using an arch variant the last few years

CenOS is the same. Even worse, I'm stuck at CentOS 6
All of my home machines are... sigh... Windows.
As well as half of my work computers
Well, 60% of them anyway

My work uses Win10

@KyleKanos It is, but hey, you have to work hard when you've discovered something that's bigger than anything Newton found.

I've gotten used to using powershell instead of bash

2:21 PM
Windows Subsystem for Linux is pretty awesome, actually
If you're allowed to install it

No, can't install crap bc it's a bank

Trust me, I feel your pain (and then some)

Something about viruses getting in causing major harm to the global economy or something

@user2723984 Agreed. Which is why I tried to not be too dismissive in my comments to him. But I know from past experience that it's not possible to argue constructively with people who are obsessed with stuff like that.

I'm sure not many viruses are written to target COBOL based software ;)

2:23 PM
I work securities side, so it's all C++ for us ;)

That's unfortunate. Because C++ is set up so beautifully to write really bad C++ code directly

I think it's a problem inherent with giving math-oriented people free reign to write code without a central architect
And also allowing development to occur without code review for a decade

That described every Fortran code out there too. And an increasing number of python codes
The most effective tool we found back at school wasn't code reviews -- those took too much time, and people took them too personally... It was pair programming

I'll have you know that the Fortran code I wrote and used was actually really well designed

Our was too -- I got to take it with me when I graduated and I still use it. And a great deal of other people in the other labs use it also now. But, it was like pulling teeth to get people to follow a style guide
And still involved a lot of us going in afterwards and refactoring/cleaning up the mess

2:29 PM
Except for the wrong ordering when doing the hydro step bc they were taking slices of i instead of slices of k...
It was a pain, but I managed to fix that on my own

3:19 PM
@JakeRose true
whomst'd've'll's
Whomst'd've'll's here has read Q is for Quantum?
WHOMST'D'VE
ahh I love that meme

3:40 PM
@NovaliumCompany I haven't had time to reply - and I haven't had enough time to get comfortable with the book's notation yet. I'll ping you as soon as I do.
I have a question for the typography nerds here, though
how do you bibtex a paper that has an en-dash in the title?

4:19 PM
@EmilioPisanty Of course, take your time! Just make sure to message me because I'm also struggling with understanding half of part 2 and part 3.

4:32 PM
If a gas expands in vacuum, work done is 0
do you think it is reasonable?
What happens if it expands from V_1 to >V_2, and then we enclose it with a surface S. Isn't some work-energy lost?

4:43 PM
@santimirandarp if it's an ideal gas then it hasn't lost any energy. None of the individual particles have collided with anything so they've kept their kinetic energy.

but if we enclose it with a surface S after the expansion the pressure on the walls is less than in the beginning @jacob1729

This is true, because internal energy goes as U~PV. U is constant V has increased and so P has decreased.
The fact that pressure has gone down doesn't imply anything about work done.

so the capacity to do work is less than in the beginning @jacob1729

I'm afraid I don't follow that. Do you mean the free energy has decreased? I think that would be a true statement.

No worries, I'm not sure too...@jacob1729 but I think your interpretation is correct

5:48 PM
on the existence of “anyonic” commutation relation.
Is there an intuitive way to see why there is no Fock-space description for anyons, and what are simple properties of tensor networks that fix this?
I can see how it’s difficult to make sense of something $(\hat b_k^\dagger)^2\vert 0\rangle$ unless there “in some sense” a notion of ordering but that’s all rather vague.

@EmilioPisanty what's wrong with using normal en-dash of two dashes: --?

@KyleKanos I think it'll be OK?
I've put that into the bib file but because of the way the project is structured I can't test whether it'll work just now
I'm more annoyed that the Google Scholar bibtex generator produces bibtex with unicode en-dashes in it
.... which, of course, are visually indistinguishable from hyphens unless you know exactly what to look for and you're explicitly on the lookout for them
..... and which, of course, will send your compilation into a tailspin

Yeah, I've had to fix a bunch of those in our bibliography files

6:03 PM
luckily the worst that happened is that the compiler ate all the dashes up and printed "Spinorbit" and "BoseEinstein", and it got corrected by the journal

Another reason to avoid LyX, but earlier versions worked just fine with Unicode & didn't spit out warnings...we updated and got a slew of Unicode warnings

I'd really like a Chrome extension that gave you a button you could click and produced working, proper bibtex
with a decent set of options for how to customize the output

And I just checked on my local LyX, and en-dash works fine with & without using double braces in title

Ah. I know what happened.

Using plain style, mind you

6:06 PM
My original version had \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} so we could use accented characters
that probably made it look at the unicode en-dashes and go "oh, yeah, you're using unicode en-dashes, that's totally not a LaTeX catastrophe".

Regex to the rescue: [^\x00-\x7F]+

6:23 PM
WHOMST'D'VE
Humanity has reach another peak with Whomst'd've
I propose taking it to the next level by introducing: Whomst'd've'll's

You say "peak" but I think you mean valley

Oh no, it's definitely a peak

Trough?

I'm not familiar with that word
I mean, Whomst'd've is such a genius invention...

It's the thing pigs eat out of

6:30 PM
Which's'll'd've'ed
WHOMST'D'VE
I want to know the inventor of this master piece

Whomst'd've'ly'yaint'ed'ies's'yes is apparently a thing

OMG YES
Whomst'd've'ly'yaint'ed'ies's'yes is what I'll answer when the teacher asks me a question.
Might as well get an A
I don't think she'll understand it. She's not superior enough

And people wonder why I'm not a professor & have little interest to be one....
2

You are interested in more superior and intellectual stuff

Writing C++ & Python code?

6:36 PM
Like "high IQ skepticism" by having a bunch of tabs open and drawing false conclusions off them?

False conclusions are the best conclusions

I can't remember the name of the video, but the phrase "interested in more superior and intellectual stuff" just sounds like the "high IQ skeptic" who was some dude on youtube going on about how flat earth was true and he was a high IQ skeptic and that's why he had 30+ tabs open for "research"

Earth looks pretty flat from my vantage point

@KyleKanos well, from my point of view the jedi are evil

Also, I have 17 tabs open on one browser and 2 in another... Is that bad?
@EmilioPisanty well touche

6:45 PM
WHOMST'D'VE AAAAAAAAA
Currently programming a roblox server in Lua
hopefully will become big
'bout to get some robux
muhahah
ROBUX!!!
AAAAAAAAA

How old are you?

17
i'm bored...

@NovaliumCompany it shows.

Thought I can learn some Lua
What are you guys doing?

Trying to automate calibration of a volatility model
And simultaneously documenting it because the existing documentation is terrible

6:53 PM
slowly coming to the conclusion that what I'm trying to prove probably isn't true

@KyleKanos I just looked up volatility models out of curiosity. I'm not in the mindset to try to understand statistical terms right now; but is it like randomness stacked on top of randomness?

It's basically the variance
So the square of the std deviation

but the variance is also random in this case?

Yes, it can be/often is taken to be a Stochastic process

So is this for like predicting market movement?

7:01 PM
Pricing trades and measuring the risk of the trade under the predicted movement
In the model I'm looking at, it's not a Stochastic process, which makes it easy for me :P

Nice. I barely understand what I'm reading here, but the gist of it seems really cool. But to automate calibration of such a model... is it constantly evaluating how good it's own model is and adjusting based on real data?
oh the wikipedia page has a large section on calibration, that might have some insight

Yep. We have options with scalar volatilities for a set of strikes & a bunch of parameters that go into the model. Since it's more than 1 parameter, I'm basically looking at simplex or Nelder-Mead it something like that
So trying to do multidimensional minimization

oh okay, I kinda get it now, that's pretty cool. Sounds like it's something which gets re-calibrated often, which explains why automating the calibration makes sense (also makes sense that you might need constant adjustments when you're trying to model something so volatile)

Basically needs to be done daily :(
But shouldn't take particularly long to do, once the quotes are entered

I can imagine it would need to be done daily. I can't imagine that predicting market movement is very accurate unless you are constantly adjusting for all the factors. Economies are complicated as hell. Reminds me of like weather

7:15 PM
Well one day's fit doesn't need to match the markets for all time, just on that day (maybe a "close enough" the next day)
So it's basically weather prediction by looking out the window on that day

Does it throw out the prior data?

I don't think you use historical values, I think it's normally the futures markets (e.g., market-determined value of a swap 1 month from now)
There might be some cases that I'm not aware of that use past data, though
I guess some machine learning algos would have to use historical data, but not sure I'd call that a volatility model

7:30 PM
Seems pretty similar to weather prediction IMO. You look at the current weather to make educated guesses on future weather. Isn't that pretty much what this would be doing?

Doesn't the mathematician Simons do that kind of stuff?

Obviously I'm just guessing compared to what Kyle knows, but it sounds like its a bit different. This method seems to look for "non-random movements" while what I understand about volatile models they account for more random movements.

@JMac it's certainly similar, but one difference is that the market quotes for future prices are a known for today whereas weather isn't known in that manner

8:24 PM
1

In this question, 5 comments on knzhou’s answer were moved to chat, but 5 questions on Ben Crowell’s answer were not moved. Neither were 9 comments on the question. (On my answer, 11 were moved, which I am not questioning.) So how do moderators decide what counts as an “extended discussion”?

physics.stackexchange.com/questions/481728/… Sometimes I enjoy talking to myself while someone screams nonsense in the background

8:39 PM
@JMac He's a little over-excited...
I was almost going to post a comment saying planet rotation doesn't work like that, but over a huge time span tidal locking may occur. But I decided against that when he started on the capslock foaming at the mouth stuff.

8:57 PM
Yeah, I wasn't even going to get into how it was wrong. I was trying to point out that we aren't friggin calculators. The guy says he has an EE degree, this should be a trivial problem to solve for an engineer. If it's not trivial, he should obviously have some idea why

I saw another trivial question a couple of days ago, with some weird misconception, by someone claiming to be an engineer. I wonder if it's the same guy.

Wouldn't surprise me. His comments suggested it's not the first account he had closed questions on. Something I find strange is that in my completely biased perspective, a lot of people coming up with these weird theories are engineers. I can kinda understand, given that engineering doesn't care so much about theoretical foundation, and novel application is so important

@JMac I heard once in a podcast about an engineer who was convinced to have found an error in special relativity, they framed it in an interesting way, the guy was used to be able to fix things that didn't work by opening the engine and see what didn't make sense, so that's what he did (his own words, IIRC)
no clue where I found it though

9:42 PM
Smart people aren't immune to dumb ideas. On Astronomy, we're getting posts from a member who's a fan of Subhash Kak, a professor of Computer Science who claims to have discovered a whole bunch of valid astronomical information encoded in ancient Indian scriptures and treatises.

9:52 PM
@PM2Ring agreed. Smart people are just as dumb as anybody else in things they aren’t trained in.

@JMac Not really; it's the age old P vs Q.

@JakeRose I wouldn't go quite that far. Someone who's been trained to think scientifically can apply their skills outside their specialty, to some degree. OTOH, anyone can be misled by their blind spots, preconceptions & pet theories, even someone like Einstein.

10:47 PM
Smart people are fine — it’s people who think they’re educated that are the worst.

11:07 PM
Retired engineers disprove relativity like every day
And they send their results to professional physicists regularly
I hope that since I'm now a retired physicist, I'll discover some new disproof

@KyleKanos is there a common thread?

The ones I've seen usually just assume Galilean velocity addition is right
Oooorrrrr were you meaning about engineers doing it? It something else?

I got an unusual innovative one in the mail that said the problem was that even Galilean relativity was incorrect, and that’s where physics went off the rails.

It kinda makes sense. Engineering focuses on application more than theory, and if you take mechanical, civil etc. you don't necessarily learn much about relativity, let alone if you took it years ago I imagine. Engineering is more problem solving and good enough approximations. If they come up with something they think "solves" the relativity problem, they might dig in instead of step back.
It fits with the basic rules they apply where speed adds up
engineering.stackexchange.com/questions/19159/… Just for a cynical example of engineers taking quick and fast approximations too far

11:29 PM
@ACuriousMind wow the Glenfiddich 18 is good
@KyleKanos huh. why?

@RyanUnger If you only really study classical mechanics heavily, and applying those rules always works, it could make sense that you might become convinced that the approximations you use must be true.

@RyanUnger Because it's familiar? IDK.
What jmac's said definitely makes sense though

Seriously, take a look at my engineering SE link, all the positively upvoted answers aren't really true, and the comments have people trying to support what they are saying. Some engineers will assume buoyant force will apply even if the bottom surface of an object has no fluid beneath it
when you apply the same rules all the time, you can lose track of how applicable they are if you never operate outside them

@JMac Jeez, that is a bad showing. Just about nobody realized that it all depends on whether fluid gets in below the object.

@PM2Ring that comic seems a bit complicated. Just make <simple object> be "some combination of harmonic oscillators"

11:35 PM
@knzhou No, it's worse. In the comments many people actively disputed that. I got pretty worked up over that question and looked at engineering SE a lot less

@danielunderwood Of course! :D

Ugh. Typical thing: for any formula, 90%+ of people who know it don’t know why it’s true.

@JMac I'm not a physicist, so I actually have no idea what the right answer is

Maybe Math.SE sometimes sees us the same way for math questions...

That's what you get when the goal becomes to memorize a formula

11:38 PM
@ACuriousMind It might be just a touch too sweet. There's some like candied apple flavor

@knzhou It's a shame too. The reason why the density buoyancy relationship works with regards to volume* is one of the things I've really enjoyed understanding intuitively. When you realize that it depends on volume because the height adds to the hydrostatic pressure difference, and the area means more force due to pressure difference, it's directly proportional to displaced volume; for any closed surface

@danielunderwood hooray for the American education system!

I tried to tell someone a couple of hours ago that relativistic mass is unnecessary and potentially misleading. He responded:
You can't avoid the concept of relativistic mass increase,regardless of whether you are accelerating particles or spaceships. — Michael Walsby 4 hours ago

fluid mechanics is probably the hardest thing

11:41 PM
@kyle Of course.

Fluid dynamics are a mess, statics usually aren't too bad.

I love Ben's immortal line: "In a book from the Roosevelt administration"

I see
Stuff like this is why I prefer math
my biggest worry is sign convention for the mean curvature vector

11:49 PM
I could never get that into math, I feel like it started to get too abstract for me and I couldn't or didn't train my mind to deal with it

@ACuriousMind After exploring their website, it seems like Glenfiddich has a 21 y/o Carribean cask variant o.o
Probably pretty expensive here

You just pick a sign convention based on how you feel on a given day!

I got too into programming to care much about math. Or physics that didn't involve computers

If I never have to write code ever again I'll be happy

I got into programming for a while, but these days it feels a lot less interesting most of the time