The h Bar

4:49 AM

0

Q: Could there be lightning in space, and would it be a perfectly straight line?

I do understand that here on Earth lightning consists of electrons moving in space and some of these electrons are tracing path, and eventually lightning will move in the direction of least resistance. Now the reason why some electrons need to trace the path is because there is atmosphere here a...

hmm...

@EmilioPisanty Is it just me or is $R_{01}$ and $R_{02}$ give me a weird impression that if I add the two together, then since they are complementary, you will actually get the same shape as $D_0$?

Likewise, adding $R_{03}$ and $R_{04}$ seemed to also give the same shape as $D_0$. I am not sure what to make of this observation

O wait sorry, you already explained in the answer, I had not paid enough attention to the brackets

Hmm...

It does seems the actual take home message of the quantum eraser experiment is what postselection does to the outcome. I wonder... if it is true that in some scenarios where in quantum experiments we see no interference pattern, the interference patterns are actually still there but is buried because two or more complementary interference patterns add up to form something that don't look like interference, which cannot be resolved without some scheme that recovers the phase relationship

Secret

6:04 AM

In fact, if my above guess is correct, in theory one can get interference patterns in any experiments if the postselection criteria contains some kind of phase relationship between observables, because then all that matters is how one decomposes the outcome

which for some reason, I found that more weird than quantum

Nick

6:36 AM

Is a particle a sphere?

When modelling particle-particle interactions, what shape is a particle best as? I think it's spherical but is there any other shape, maybe one that can be regularly tesselated, that it ought to be.

John Rennie

@Nick do you mean fundamental particles like electrons? Or larger particles like gas molecules or billiard balls?

Sir Cumference

6:56 AM

@bolbteppa That has to be the longest version of that meme I've seen :P

Emilio Pisanty

7:41 AM

@Secret that's what decoherence is.

Slereah

morning

Nick

@JohnRennie self-defined or general. I just want to template something for the future right now.

Slereah

when modelling particle interactions, in modern theories, they are considered to be points

Particles used to be modelled as hard spheres in the early 20th century

Nick

that's newtonian and points really don't have mass and shape and spheres sound too um, it sounds like we made that up.

I'm thinking of Regular Polyhedrons, because it would be interesting to see what edges and surfaces do when they clank in on eachother, but not just in a kinetic sense but like sheering forces and strain and all those other juicy things.

John Rennie

@Nick the problem is that scattering of fundamental particles is fundamentally different from the scattering of macroscopic particles. You can't use the same approach for both.

Fundamental particles don't have a size. Instead they interact via a potential that is a smooth function of distance.

Nick

7:56 AM

What is potential really, is it an energy embedding in space? like a blanket with hills and valleys? Because then the billiard balls work fine as a fundamental particle.

John Rennie

The potential is just the energy of the system, i.e. of the two interacting particles, as a function of distance.

Slereah

@Nick Point particles can be described as having a mass

Nick

@JohnRennie ok $P(x)$ is some gradient function that quantifies energy owned by the interaction.

Slereah

If you really want to you can describe them as moving delta potentials

Nick

@Slereah yes, but point particle is just another term for centroid location.

Slereah

7:59 AM

It is not.

Nick

Then, we are neglecting surface areas. I think area is required to model interaction on a blanket. Like a watermelon thrown on a trampoline.

Slereah

I mean overall particles aren't even described as having a shape in most quantum theories

But if you go by the ones that do, then particles are either points or strings

By going with worldline quantum theory or string theory

Nick

Is it impossible to assume another shape and prove or disprove the validity of such a particle existing in nature?

John Rennie

@Nick yes

Slereah

@Nick Well there are no theories with any other shape that panned out so far

Nick

8:03 AM

@JohnRennie but my question is, is the potential an attribute of space or is it an attribute of the particle?

Slereah

People have tried membranes and 3D shapes but this led to divergences

Nick

@Slereah well, i am proposing regular polyhedra here.

@Slereah do you have any references on that?

Slereah

@Nick Going all the way back to Aristotle?

@Nick I think it's in Green, Schwartz and Witten's book on string theory

Nick

@Slereah ok, I'll check it out. thanks.

John Rennie

@Nick I'm not sure what you mean by an attribute of space. The most fundamental description of the interaction we have is from quantum field theory. This describes the two particles interacting thorough their quantum fields. I guess you'd say it was an attribute of the particles.

Nick

8:05 AM

@JohnRennie Sorry, I meant field and not space.

Slereah

why would you assume polyhedrons

That's a bit old school

Do you have earth, fire, water and air particles

John Rennie

@Slereah amplituhedron? :-)

Nick

@Slereah Uh, yes!

Think along the lines of particle systems in blender 3d engine.

Slereah

I mean even Democritus didn't have polyhedral atoms :p

John Rennie

@Nick the interaction is described as a property of the quantum field, but be careful about taking this too literally. The quantum field is a mathematical object not a physical object. Quantum field theory works, but what exactly a quantum field is describing is an open question that still puzzles physicists when they have nothing better to do.

2

I know of no sense in which the interaction has anything to do with polyhedra.

Nick

8:11 AM

ok, imagine this, every point in space corresponds to a baby name. I throw in a bunch of polyhedrons and they bump into each other and land in some positions and I generate a subset of the baby names for the baby that needs a name.

Um, that's what I'm working on, and almost every conversation where I bring up particles takes me into particle-physics for some reason. (and I honestly don't mid what this ends up as, as long as it's interesting)

John Rennie

@Nick I'm afraid I have no idea what that means. Sorry :-(

Nick

In an lxmxn volume, point (x,y,z) is mapped to a string from a list of strings and random points are selected based on what happens in the simulated environment and a subset from the list is generated.

Why 3d objects bumping into eachother for this? Um, it seemed like a step above the kNN approach in data science.

John Rennie

It sounds vaguely information theoretic. There are information theory approaches to quantum mechanics but I don't know much about them, and none are anywhere close to being a complete theory in the way that quantum field theory is.

Nick

I guess phsyics is not a place where nominal values like baby names have relavence, but it's an example. Probably has some more scientific use-cases like selecting which topics need study or which astronomical bodies need new names or something like that would be more relavent. Yes, it is information theory, in a lot of senses.

@JohnRennie And Fock Space does not have any requirement for particle anatomy, just the potential fields?

John Rennie

@Nick the Fock space is the space of states of the field.

We interpret excitations of the Fock states as creating and annihilating particles, but they are states of the field not states of particles.

Nick

8:27 AM

ah, you have answered now my first doubt.

23 mins ago, by Nick

@JohnRennie but my question is, is the potential an attribute of space or is it an attribute of the particle?

Slereah

Also "particle" in the Fock state sense isn't really the same as in the point particle sense

Fock particle states aren't localized at all

Nick

That's to do with the quantum nature, right? So position is fuzzy, that's ok.

Slereah

Well it's a bit more than fuzzy :p

It's spread over all space

John Rennie

@Nick it's complicated. How long have you got? :-)

Nick

Sure, I imagine it teleports as well.

@JohnRennie one lifetime

John Rennie

8:28 AM

@Nick too short! :-)

Nick

You must be thinking of nuclear half-life and decay, surely.

ok, I'll feed my brain into the matrix. I have whatever time it takes.

google.com/search?q=how+to+reverse+entropy

google.com/search?q=human+body+as+a+perpetual+machine

Nick

8:51 AM

Maxwell's demon

Maxwell's demon is a thought experiment created by the physicist James Clerk Maxwell in 1867 in which he suggested how the second law of thermodynamics might hypothetically be violated. In the thought experiment, a demon controls a small door between two chambers of gas. As individual gas molecules approach the door, the demon quickly opens and shuts the door so that only fast molecules are passed into one of the chambers, while only slow molecules are passed into the other. Because faster molecules are hotter, the demon's behaviour causes one chamber to warm up and the other to cool down, thereby...

PM 2Ring

@Nick If particles were polyhedra, then we'd expect the symmetries of the polyhedron to have some influence on the particle interactions. But we don't see that. All observations involving fundamental particles (i.e., not composite particles) are consistent with particles being point-like, with spherical symmetry.

Nick

@PM2Ring ok, are there no chances of surfaces or irregularities on the observed sphere. Isn't there a limit to the resolution of observation that would allow for some shape to be assumed although not pertinantly required by any theory for it to be so.

John Rennie

@Nick we can currently resolve down to about $10^{-18}$ metres, and there are no signs of irregularities on that scale.

Nick

And I'm betting even if there were particles smaller than that, it would still be modelled spherically because of what is deciphered from the potential fields.

I'm still interested to know the effects of a particle system that has some meaning for the surface.

1 hour ago, by John Rennie

@Slereah amplituhedron? :-)

and this is very interesting, in regard to quantum theory.

PM 2Ring

9:12 AM

@Nick Our macroscopic intuitions of geometry aren't so useful down at the size of atoms & smaller. This is related to Heisenberg's uncertainty principle. To make observations of the structure of stuff requires energy, and the more precision you require, the more energy you need. So to get a smaller scale than what John mentioned, we'd need a more powerful particle collider.

And it would most likely tell us that electrons still look point-like, with spherical symmetry at that scale. If we could build a collider 10^15 times more powerful, then we might see some structure, but that"s not technically feasible.

Nick

@PM2Ring I'm thinking about working the other way around. Theoretic approach, build a model, if it fits a theory one day, then great. Rather than waiting for observation to stir the research.

PM 2Ring

@Nick That's ok, but you still need to base your model on what we've observed. Otherwise, it's just metaphysical speculation, like Kepler trying to fit the orbits of the planets to the "perfect" geometry of the polyhedra. Or the stories that pass for cosmology in the various ancient scriptures.

Nick

@PM2Ring that is true.

PM 2Ring

At low energies, even atoms look fairly spherical, even though they're composite bodies. So an undisturbed helium atom is very spherical. It's not easy to see how that could work if you treat the electrons, protons, and neutrons as classical spheres or polyhedra.

Novalium Company

@EmilioPisanty I bought Q is for Quantum 1 day ago (but I haven't had time to start it yet) and I was wondering, besides teaching me the "real" core basics of QM, would it also teach me to evaluate future quantum technologies? (whether they are a scam or can actually work...)

Nick

9:30 AM

Nov 7 '13 at 10:16, by Anonymous

@Nick A squareheadon. : )

Better start making new shapes and concepts, then. At this point, atoms and molecules might as well be robots in disguise.

Surely, molecules don't look all perfect like this. Some of them would be injured and out of shape.

PM 2Ring

@Nick Images like that are diagrams that depict some of the structural information, but by necessity they leave out some information.

John Rennie

@NovaliumCompany the Terry Rudolph book or the John Gribbin book?

PM 2Ring

Going back to the undisturbed helium atom, its electrons are in the 1s orbital. That means the probability cloud of their position has spherical symmetry. If you choose a small volume near the atom there's a certain probability of detecting an electron within that volume, and that probability only depends on the distance from the centre of the atom.

John Rennie

@NovaliumCompany Terry Rudolph's book looks quite good at first glance.

@NovaliumCompany have a look at this article. I suspect you'll find it very relevant.

PM 2Ring

9:46 AM

However, the 1s orbital also says that the momentum of an electron in that orbital (or any s orbital) has no orbital angular momentum. That is, if you try to measure the momentum of a 1s electron then it's purely radial: it's heading directly towards or away from the nucleus.

Nick

Well, that's a step above all this then x)

Secret

I am... not very sure what I am reading in this transcript...

Novalium Company

@JohnRennie Terry Rudolph. I'll read the article later cuz I have to go to school now... ahh boring.

Captain Bohemian

@NovaliumCompany your action of buying a book is very fast.

Nick

inconsequential babble mostly, @Secret

Novalium Company

9:58 AM

@CaptainBohemian Is that a compliment? :D

PM 2Ring

@Nick Yeah, diagrams like that are pretty misleading. Apart from the stuff about the electrons, it gives the impression that the nucleons (protons & neutrons) are locked into position, but they actually have momentum, and move in orbitals, quite similar to the electron orbitals.

Novalium Company

@CaptainBohemian I'm getting 30$ each month from school cuz I have good grades...

John Rennie

Wow, no-one ever paid me to go to school! :-)

Nick

the meritocracy dawns with many incentives, but mostly for honours students.

Novalium Company

I bought it fast because @EmilioPisanty recommended it and I trust him. I googled the book, it looks interesting, it wasn't expensive, soo... what better way to spend your money than on books?

@Nick I don't understand 90% of the words in this sentence xDD

Nick

10:00 AM

@PM2Ring heavily structured thingabobs floating around and glued to be you and me and all that we see. What a thing that is, eh.

Captain Bohemian

@NovaliumCompany no, because I seldom buy any book not for school need that fast. I usually consider whether buying it for long. I would only photocopy a book that fast because photocopying can be reimbursed when I was in my lab.

PM 2Ring

BTW, the K shell in that diagram equates to the 1s orbital, and the L shell to the 2s & 2p orbitals. The K & L come from old 19th century spectroscoper's notation, long before modern atomic theories.

Nick

@NovaliumCompany Atleast there's 1.1 words you do understand. I consider that a win.

Novalium Company

@Nick Can't believe you actually calculated it! :D

Nick

Can't believe you understand 0.1 words, a fraction!!

Novalium Company

10:03 AM

@Nick I'm from Bulgaria... my only source of english is internet and books.

Nick

one tenth of a word implies there's ten parts to a word to disect from

@NovaliumCompany Same.

Captain Bohemian

@NovaliumCompany your high school is so nice to you. My schools before graduate school never gave us much money just for the reason of good grades.

PM 2Ring

Electrons in s orbitals have a non-zero probability of being in the nucleus. Cartoons like the above diagram don't show that.

Nick

@PM2Ring so, thomson was right to an extent with his plum cake pudding.

TIL the atomic nucleus is a soup.

Captain Bohemian

@NovaliumCompany usually the money from our schools just for the reason of good grades isn't even enough to pay for the tuition or eating.

PM 2Ring

10:07 AM

@NovaliumCompany FWIW, your English is very good. Occasionally, you use the wrong preposition, but it's generally clear what you mean.

Novalium Company

@PM2Ring Here I don't really pay attention to my English because I know you'll understand it, but if I have to use proper grammar, complex words... I think I won't do a bad job.

Nick

TIL prepositions and postpositions, together called adpositions, are a class of words used to express spatial or temporal relations or mark various semantic roles.

Novalium Company

@CaptainBohemian My 30$ is called scholarship. (Or at least the Bulgarian version of it)

Captain Bohemian

@NovaliumCompany I know. Scholarship is just what I mean by the money for good grades.

Novalium Company

Alright guys. I have to go to high school now (unfortunately) soo cya later.

PM 2Ring

10:10 AM

@Nick A very small extent. ;) His electron dough is totally uniform, so it doesn't reflect the structure of the probability clouds of electron position.

Nick

@PM2Ring For a microfraction of the oscilation of Cs-133 atoms, perhaps. Maybe once in the universe, somewhere out there.

Captain Bohemian

@NovaliumCompany our schools before university usually just award us a prize paper for good grades without any money or other substantial things which have economic value. That prize paper is just a piece of paper saying we award you a prize for your good grades to cheer you. I don't know how to say that paper in English.

only university would award money just for the reason of good grades. But that kind of money is also of the quantity not enough for even food or tuition.

PM 2Ring

This page has some nice info about electron orbitals. The bottom graph in the 1st diagram shows the relation between radius & probability for a 1s electron, but you should read the text to make sense of the diagrams.

Slereah

10:25 AM

0

A: Rigorous procedure of gluing together two spacetimes

Boy oh boy you're in luck because it's one of my favorite topic! You are indeed correct, there isn't a whole lot of literature on the topic of rigorous treatment of spacetime gluing. There's a whole pile of articles and books to peruse to get some unified picture of what this involves. Not parti...

phew

Secret

1:52 PM

quora.com/…

Accounting is so annoying

Matching principle

In accrual accounting, the revenue recognition principle states that expenses should be recorded during the period in which they are incurred, regardless of when the transfer of cash occurs. Conversely, cash basis accounting calls for the recognition of an expense when the cash is paid, regardless of when the expense was actually incurred.If no cause-and-effect relationship exists (e.g., a sale is impossible), costs are recognized as expenses in the accounting period they expired: i.e., when have been used up or consumed (e.g., of spoiled, dated, or substandard goods, or not demanded services)...

Slereah

3:05 PM

Hey it's @RyanUnger

JMac

4:28 PM

is the Flawless guy driving anyone else mad? They seem to just be posting whatever they can google that is remotely related to the topic and ignoring all the actual questions

vzn

4:43 PM

@Nick your shoshin questions touch on newer ideas eg solitons check em out :)

Abhas Kumar Sinha

Hello

Just a personal question, How do you manage the headache caused from kids?

There are kids all around, and I'm getting bored, this sucks. They are screeming, shouting, fighting. I don't like someone reading my chats and stuff and more I tell them to stop, the more they're doing that 😓😔😔😞😟

Hopefully, the question is not an headache for others.

Emilio Pisanty

4:59 PM

Any mods around? this looks like the start of a vandalism campaign.

ACuriousMind

@EmilioPisanty Thanks, on it

Emilio Pisanty

@ACuriousMind wait, what'd you do to my link?

=P

ACuriousMind

Magic. :)

Jake Rose

Is anybody familiar with basic condensed matter?

Emilio Pisanty

hmmmmm

@JakeRose depends

Jake Rose

5:10 PM

specifically calculating the density of states

^

Emilio Pisanty

@JakeRose what about it?

(I may or may not be able to help, depending on the specifics)

Jake Rose

considering a 1D potential box of width a, a) why is using $\psi (0) = \psi (a) =0 $ a good approximation to the situation, b) Why does using periodic boundary conditions, thus incurring a k space with plus and minus $k_x $ also a good approximation?

i has a look at one of the answers which talked about this but I just couldn’t really get the point

Emilio Pisanty

well

those two can be good approximations

they can also be terrible approximations

without more context, one can't really tell

Jake Rose

Well the context is the free electron model. This is where this has popped up.

Emilio Pisanty

generally, if you're mostly interested with what happens in the bulk, and you expect edge effects to be negligible (or you're putting them on hold, so that you can go back to edge effects once you've firmed down what happens in the bulk), then you don't need to fret too much about the boundary conditions

Jake Rose

5:16 PM

If it doesn’t matter (roughly) what’s happening on then how can we impose bc?

Emilio Pisanty

@JakeRose well, you need to specify some form of behaviour, to get a definite problem you can solve

the alternative is to treat an infinite system, which can be similarly challenging or more

Jake Rose

So why is imposing these bc w good choice?

i.e. why not say it’s 5 in one side and 246 on the other side

Emilio Pisanty

@JakeRose they're good choices because they're easy to handle

@JakeRose This wouldn't do. You need the problem to be linear. Those boundary conditions aren't linear.

Jake Rose

what are linear bc?

Is there any good reason to why they’re decently close to the physical situation?

Emilio Pisanty

if $\psi$ and $\phi$ are solutions of the problems, you need $a\psi + b\phi$ to also be a solution, for arbitrary $a,b\in\mathbb C$

@JakeRose but the question isn't asking why they're good choices, it's asking why they're good approximations

Jake Rose

5:22 PM

could you not have $\psi (5)+ \phi (5) = \psi(246) + \phi (246)=0$?

mhmmm, os why are they good approximations?

Emilio Pisanty

@JakeRose this reads as $\psi(0)=5$ and $\psi(a)=246$. If that's not what you meant, then you need to be more careful with how you phrase things

Jake Rose

Oh sorry I got mixed up

Emilio Pisanty

if you meant $\psi(5)=\psi(246)=0$, then it's exactly the same. QM is translationally invariant, so you can just move everything by $5$ to the left, and you get $\psi(0)=\psi(241)=0$, or in other words $\psi(0)=\psi(a)=0$ with $a=241$.

Jake Rose

The eq should be $\psi (0) + \phi (0) =5$ plus the other bc

Emilio Pisanty

@JakeRose you've stopped making sense.

What are $\psi$ and $\phi$?

Jake Rose

5:30 PM

Ohhh

sorry I’m chatting rubbish

ignore me

let’s go back to why the bc are good approximations

Emilio Pisanty

15 mins ago, by Emilio Pisanty

generally, if you're mostly interested with what happens in the bulk, and you expect edge effects to be negligible (or you're putting them on hold, so that you can go back to edge effects once you've firmed down what happens in the bulk), then you don't need to fret too much about the boundary conditions

Jake Rose

I don’t fully follow sorry.

Emilio Pisanty

they're good approximations because you don't care about the boundary

you're doing condensed matter, you only care about the bulk

basically by definition, if the difference between those two BCs matters, you're doing surface science, not condensed matter

(sort of. surface science is also a part of condensed matter. but hopefully you get the point.)

Jake Rose

But what we decide our bc are impacts the solutions dramatically

so surely we should have to care about the boundary?

(sorry for the cyclic nature of this discussion)

Emilio Pisanty

@JakeRose it impacts some aspects of the solutions (dramatically).

if you care about those aspects, then they're not good approximations

25 mins ago, by Emilio Pisanty

they can also be terrible approximations

if you don't care about those aspects,

25 mins ago, by Emilio Pisanty

those two can be good approximations

PM 2Ring

5:41 PM

Some people have strange ideas. Eg: "if you could zoom into a small portion of the curve on the smallest scale you would actually see a staircase of alternating horizontal and vertical increments". From physics.stackexchange.com/a/479978/123208

Jake Rose

It just feels rather arbitrary @EmilioPisanty

@PM2Ring that answer was a wild ride

Emilio Pisanty

@JakeRose it can be

Jake Rose

Mhmmm

Emilio Pisanty

it just means that you need to keep an eye out for how hypotheses like this one are used throughout the line, and how the answers would change if you had made a different choice

the question text as phrased looks pretty awkward and ill-constructed - as far as it goes, I'd say pay lip service and move on to something more useful.

But your observations are much deeper and much more important - don't discard them.

Jake Rose

@EmilioPisanty thanks. Nice to hear a compliment about my questions for a change compared to feeling dumb 99% if the time!

PM 2Ring

5:59 PM

@JakeRose :) I'm curious how the author will respond. And I wonder what other odd misconceptions they've managed to pick up. Maybe they'll be able to fix their answer so I don't have to downvote it...

JMac

6:26 PM

@PM2Ring They really lost me on that one... wow. It seems like they're working in some sort of discrete time system? But even then... it's still like impossible to follow. I'm very curious about what they are trying to say

JMac

6:38 PM

Wait what, there's a heavily related question to that answer physics.stackexchange.com/questions/480272/…

Emilio Pisanty

Goodness. It seems @Chair-then-@Rishi has deleted his account

PM 2Ring

@JMac Yeah, seeing that new question reminded me about that weird answer.

Emilio Pisanty

... taking >500 of my rep with him ...

PM 2Ring

@EmilioPisanty What?! That's very unexpected.

JMac

@EmilioPisanty Well now I feel dumb for not even noticing that Chair was Rishi, that explains the 20 points I just lost though. That's also unfortunate... I wonder what happened there

Emilio Pisanty

6:42 PM

I don't really know what the thresholds are here

108

A: Don't throw away all votes when a user is deleted

I'm not gonna call this completed; as you and everyone else reading this know, we do still throw away some votes for some user-deletions... and probably always will for the reasons you noted in your proposal. But we have a system in place to prevent the most disruptive forms of vote deletion, a...

but it feels like a stretch to say that this user didn't meet them

PM 2Ring

I know Rishi got some flack from the OP of that recent metrology question, but surely that's not sufficient reason to rage-quit...

JMac

@EmilioPisanty Unless they for some reason violated the voter fraud policy (seems out of character from my limited interactions with them)

Emilio Pisanty

@JMac Seems out of character to me, too.

JMac

Yeah, closest I would expect is genuine activity setting off a script or something... but obviously that shouldn't lead to deletion unless justified... just strange all around

PM 2Ring

@EmilioPisanty I think there's also a vote age threshold too. On SO, I was told that votes older than 60 days are preserved.

Emilio Pisanty

6:47 PM

it'd be good to have a better idea of the scope of the removed votes

ACuriousMind

@PM2Ring I think you're mixing that up with reputation earned from posts more than 60 days ago staying with the user even if the post is deleted, cf. meta.stackexchange.com/a/327541/263383

SDFG

@Rishi quit? What!!!??

PM 2Ring

Rishi asked in here if that metrology question was a dupe, and I said:

2 days ago, by PM 2Ring

@Rishi Sort of, since Emilio's mega-post appears to cover that stuff https://physics.stackexchange.com/questions/147433/what-are-the-proposed-realizations-in-the-new-si-for-the-kilogram-ampere-kelvi

@ACuriousMind Ah, right.

ACuriousMind

@JMac All I can safely say is 1. the deletion was triggered by the account owner and 2. the deletion was reviewed by a CM before going through.

Emilio Pisanty

@PM2Ring damn, and right above a ping to me, too. No, it's not a duplicate.

@ACuriousMind huh. Fair enough.

If y'all wanna short me, then go ahead, short me. I don't care.

JMac

6:51 PM

@EmilioPisanty I guess they decided that 500 rep to you wasn't significant lol; probably not inaccurate (maybe a bit rude :P)

Emilio Pisanty

(j/k aside - I really don't!)

@JMac 500 rep more or less has indeed faded into the noise.

I do care about staying ahead of Qmechanic on the total rep earned (i.e. rep + offered bounties), but that's about as much as I'm able to gamify bare rep nowadays

PM 2Ring

@EmilioPisanty Agreed, which is why I didn't dupe-vote it myself. I just noticed that the OP of that question is unregistered. physics.stackexchange.com/questions/479739/…

Emilio Pisanty

@PM2Ring "unregistered" sounds a bit inaccurate. You can't post on PSE without registering for an account, so unregistered OPs aren't a thing here. (They are on some other SE sites, for contrast.)

That account also appears to have been deleted.

It showed up on this chat yesterday.

yesterday, by Tellus

Hi! A moderator commented that I should edit an answer to my question to make it complete, if I could improve it in that way. I tried to to improve it, but it seems to have been rejected: "This edit deviates from the original intent of the post. Even edits that must make drastic changes should strive to preserve the goals of the post's owner."

JMac

@EmilioPisanty You can't? I swear I've seen unregistered users all the time in review queues?

Emilio Pisanty

@JMac You can suggest edits, but you can't ~~post~~ ask. (apparently you can answer, though.)

try asking a question from an incognito window

PM 2Ring

7:00 PM

@EmilioPisanty Ah, right. I remember seeing that. I try to at least skim the transcripts to catch up on stuff I miss.

Emilio Pisanty

and that OP didn't even take the trouble to accept the (excellent) answer.

PM 2Ring

Dale wasn't impressed with the suggestion that he spend time importing a linked table into his answer.

Emilio Pisanty

@PM2Ring OP had an extremely brash and uncivil tone on all the comments I saw there.

I would not at all be surprised if all of OP's side of the conversation was auto-deleted via a quorum of rude-or-abusive comment flags without mod intervention

PM 2Ring

And it looks like Tellus tried to edit it in himself, but it got rejected. Maybe the typesetting was lousy. Or it was an over-zealous review queue person...

Kyle Kanos

@PM2Ring I'm not over zealous, am I?

Emilio Pisanty

7:05 PM

the question seems to have lapsed out of HNQ. I wonder if the deletion of OP's account triggered it.

@PM2Ring it's a little more complicated than that.

PM 2Ring

@EmilioPisanty Yeah, I missed most of that. I saw the start of it, but it was all cleaned up when I checked later.

Emilio Pisanty

the relevant suggested-edits review ticket

Kyle Kanos

Also, Dale ended up approving it, after 2 people rejected it, which is weird

Emilio Pisanty

@KyleKanos yep

PM 2Ring

@KyleKanos You might be. :D

Emilio Pisanty

7:06 PM

heck, it takes some rather finely-tuned timing for that review ticket to be even possible

MrRobot9

I am facing a little difficulty in understanding how to convert Euler angles to directional vector. Does anyone have a good source to understand the derivation?

Kyle Kanos

@PM2Ring I suppose that could explain the massive number of reviews for me...

PM 2Ring

@EmilioPisanty Ah. So he was just editing in a PNG of the table. That's less than ideal...

Emilio Pisanty

though even then I don't understand - the approval by the answerer was given a full 1h15m after @299792458 rejected the edit, which should have killed the edit suggestion

@PM2Ring I agree. I suspect I would have rejected the edit, too.

JMac

@EmilioPisanty Probably popped up as a 1 on Dale's notifications and he opened it before the review completed

but didn't actually accept until later

Emilio Pisanty

7:10 PM

@JMac that would explain it, but it feels like a fair bit of a stretch to me

PM 2Ring

@KyleKanos Lol. Seriously, from the quality of your answers, I expect that you're a thorough and conscientious reviewer.

Emilio Pisanty

@MrRobot9 what do you mean by "directional vector"? The axis of the rotation?

JMac

@EmilioPisanty I'm pretty sure I've done similar before (except I think I also rejected after others rejected)

Kyle Kanos

Also seems that I only lost 40 rep to Rishi quitting, which is kinda surprisingly low

ACuriousMind

160 over here :/

Kyle Kanos

7:15 PM

Well apparently he really like Emilio and hated the rest of us :P

Emilio Pisanty

@KyleKanos ¯\ _(ツ)_/¯ maybe my posts are just better ¯\ _(ツ)_/¯

</ jk >

Kyle Kanos

@EmilioPisanty compared to mine, that probably goes without saying

Emilio Pisanty

@KyleKanos what? no.

it goes without saying that my posts are more

that's just raw empirical fact, what with you having chosen better ways to spend your time

but "better" doesn't even make sense

Kyle Kanos

True, you've got like 5 times as many answers as me

And like 35 times as many questions

Emilio Pisanty

@KyleKanos and also more answers posted while Rishi was active

@KyleKanos questions not quite so much

my q:a ratio has been dropping lately

Kyle Kanos

7:27 PM

You have 140 Qs to my 4.

Emilio Pisanty

@KyleKanos yes, but mostly from before Rishi became active

probably still more, but less pronounced

Kyle Kanos

I also answer smaller niche tahs (comp-phys, fluids, etc) than your tags of QM, QFT, E&M,...

Slereah

@KyleKanos At first I thought you said IQ

Kyle Kanos

Last Q I asked was like 4 years ago. Apparently my best one, but still

@Slereah that could be true, but not what I said :D

Emilio Pisanty

@KyleKanos exactly. they're just different.

JMac

7:31 PM

I haven't asked a single question on PSE. I haven't really been studying anything since I joined and haven't thought of any questions I really want to ask until someone else asks them and I realize I want to know the answer

I find it hard to come up with non-trivial questions when I'm not looking at new concepts very often

Kyle Kanos

I've got a question I would like to also answer, but just haven't had the time to even write any of it

And it probably would get me that prestigious bronze badge for 5 positive questions

Emilio Pisanty

indeed.

ACuriousMind

...looks like a damped oscillator if you squint

Emilio Pisanty

Having reached the prestigious high mark of 8 questions for every 100 answers, back in early 2017, I do seem to be on a steep decline

ACuriousMind

(everything looks like an oscillator if you squint :P)+

Kyle Kanos

7:42 PM

That is an interesting spike near that 2014 transition

Emilio Pisanty

26

Q: How I learned to stop worrying and start asking questions

As has been noted in the past, particularly in Question self-destruction: why don't experts ask more questions? and in Does reputation correlate with the question-to-answer ratio?, and also here, this site has the peculiarity that, in overwhelming proportion, our 'expert' users, by multiple measu...

discussion questions

@KyleKanos you're right, that's odd

no idea what caused it

PM 2Ring

8:04 PM

I hope Pela answers this question: physics.stackexchange.com/questions/480182/… I know the universe was opaque before recombination, but I have serious difficulty accepting it was literally dark in the visible spectrum, at least by the end of BB nucleosynthesis, if not earlier.

Sure, the visible spectrum was a long way from the black body peak wavelength. But there's a lot of area under that curve.

Of course, a detector of visible light that could survive that regime would be difficult, but that's an engineering problem. :)

JMac

@PM2Ring I'm not sure if their point about blackbodies was trying to agree with you, or they wooshed right over the point you were trying to make

But as far as my extremely limited knowledge goes, I totally agree with your logic. There should be visible light basically everywhere; it just gets trumped by all the other EM radiation so it's relatively insignificant; but if you somehow had human senses and could survive, presumably there is a visible spectrum

PM 2Ring

@JMac Yep. But I'm not clear on how bright it'd be, since you can only get photons from the plasma close to your eyeball, which does limit things a fair bit.

And having your eyeballs melted by X-rays doesn't count as seeing. :)

3

JMac

8:19 PM

@PM2Ring Yeah, that's where it gets tricky. It limits things in a way, but at the same time probably not a whole lot. The entire angular resolution of your eye should be exposed to it, so that's a plus, compared to just looking at a heated object that takes up only a portion of your vision.

PM 2Ring

I linked a great answer by Pela in a comment on the question, which talks about the various frequencies in the modern universe, but it doesn't really address the question of brightness, or the early universe.

Transcript for