@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.
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.
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.
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?
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
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.
@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.
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
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
@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
@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.
user280247
but if we enclose it with a surface S after the expansion the pressure on the walls is less than in the beginning @jacob1729
I’m hoping someone can help clarify comments to an answer to this question: https://physics.stackexchange.com/questions/43125/is-it-possible-to-make-statements-about-bosonic-fermionic-systems-by-taking-the?answertab=active#tab-top 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.
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
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 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"
@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?
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
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)
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
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?
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
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”?
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.
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)
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.
@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.
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
@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.
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
@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
@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
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 Walsby4 hours ago
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”?
