The h Bar

Abhas Kumar Sinha

15:00

@JohanLiebert That's what I was talking, there is polarization and that's what I dislike.

I give up my mind of posting answers here

-427

Q: An apology to our community, and next steps

I’m David Fullerton, Stack Overflow’s CTO, responsible for the product, engineering, and community teams. I joined Stack Overflow in 2010 because I believed in the vision and mission of Stack Overflow. I wanted to be a part of building a community where programmers come together to help one anot...

ACuriousMind

@JohanLiebert it's a bot, no human curates it and it is a time honoured tradition to downvote its Community Ad every year ;)

Johan Liebert

@AbhasKumarSinha what happened to him(Chandrasekhar)?

Abhas Kumar Sinha

@JohanLiebert nothing

John Rennie

@JohanLiebert he reached a limit

Abhas Kumar Sinha

@ACuriousMind I wonder why you don't inform everyone here to address you in a gender neutral way?

@JohnRennie He's newly appointed, I think.

@JohnRennie @JohanLiebert Let's move to physics parliament.

John Rennie

15:07

@AbhasKumarSinha it was a poor attempt at a joke. So poor that no-one noticed :-)

Johan Liebert

@ACuriousMind "it is a time honoured tradition to downvote its Community Ad every year" I can't comprehend it (is it a joke?)

Abhas Kumar Sinha

@JohnRennie lol, okay, I now get it...

@JohanLiebert Just downvote, that's it.

ACuriousMind

@AbhasKumarSinha why would I? I'm fine with being called 'he', though given my profile picture I can't take really exception to people calling me otherwise at first

John Rennie

Since God is gender neutral I would like everyone to call me God.

ACuriousMind

@JohanLiebert no, it's just what happens. Every year the default ad for the Twitter account gets posted, and every year it gets downvoted because no one really likes that twitter feed

Abhas Kumar Sinha

15:10

@ACuriousMind But, CoC says, tht Gender Neutral Chat should be promoted. By citing a useless US Law.

Johan Liebert

@ACuriousMind okay I got it.

ACuriousMind

@AbhasKumarSinha no, that not what it says. Just call people by the pronouns they ask you to use.

Loong

> Use stated pronouns (when known).

Abhas Kumar Sinha

@ACuriousMind Okay...

Johan Liebert

@JohnRennie God please help me!

Abhas Kumar Sinha

15:12

I was once lectured for using gender neutral words by a moderator in other room.

I didn't like it! :(

@JohnRennie God, What did you have at dinner? :P

John Rennie

@JohanLiebert I bring words of comfort to all physicists: "don't study fluid dynamics"

Abhas Kumar Sinha

@JohnRennie Why? Fluid Dyanamics is cooool! :P XD :D

John Rennie

Mods, we have a bot in the room! :-)

Abhas Kumar Sinha

@JohnRennie :P XD

Johan Liebert

@JohnRennie @AbhasKumarSinhA God is the God of GR and SR!

Abhas Kumar Sinha

15:16

@JohanLiebert God is the God of the God of GR, SR

John Rennie

There is a relativistic version of fluid dynamics of course - magnetohydrodynamics

Abhas Kumar Sinha

@JohnRennie God, help me XD

@JohnRennie What is the name of your kid?

Johan Liebert

@AbhasKumarSinha God is the God of GOd of God! (Now after sometime it would become meaningless!)

John Rennie

> Magnetohydrodynamics combines the intuitive nature of Maxwell's equations with the easy solvability of the Navier-Stokes equations. It's so straightforward physicists add "relativistic" or "quantum" just to keep it from getting boring.

Abhas Kumar Sinha

@JohanLiebert God is the God of GOd of God of God is the God of GOd of God!

John Rennie

15:18

explainxkcd.com/wiki/index.php/1851:_Magnetohydrodynamics

Abhas Kumar Sinha

@JohnRennie K, it's very boring now.

Johan Liebert

@JohnRennie God have you voted to close this homework question?

Abhas Kumar Sinha

@JohanLiebert If god says, follow.

GDD

Johan Liebert

@AbhasKumarSinha okay bye!

John Rennie

@JohanLiebert aha, thanks, I've voted to close now.

Abhas Kumar Sinha

15:25

bye

@JohnRennie Resnick Halliday Walker 3rd Edition, chapter 1 question 10 (exercise), we were asked to do that in 8th grade!

"Iran never won a war, but never lost a negotiation!" Donald Dick

twitter.com/realDonaldTrump/status/1213078681750573056?s=20

Everyone see this : twitter.com/Atheist_Krishna/status/1213100040861835265?s=20 It's funny af

Abhas Kumar Sinha

15:53

@Semiclassical Hello sir, Is there any stuff on Quantum Entanglement in Landau and Lifshitz?

vzn

@JohnRennie lol xkcd, 21st century wisdom with stick figures humor on fluid dynamics + collatz, more than anyone realizes, ahead of its time™ :) explainxkcd.com/wiki/index.php/710:_Collatz_Conjecture store.xkcd.com/products/collatz-conjecture

Abhas Kumar Sinha

@vzn <3 Number Theory

vzn

@AbhasKumarSinha \o .<3 .. so what parts do you like? :)

Sarvesh Ahuja

Hi, can somebody help on this: physics.stackexchange.com/q/522694/187127

Abhas Kumar Sinha

@vzn collatz conjecture, prime numbers and distribution.

vzn

16:07

@AbhasKumarSinha sometime when you have free time check out riemann hypothesis + physics too (QM) :)

Abhas Kumar Sinha

@SarveshAhuja space time is not QM

Electrons move in continuous paths and don't teleport but thy don't have definite paths

Sarvesh Ahuja

How exactly does the electron move

?

Abhas Kumar Sinha

@vzn riemann hypothesis? I give up, its insanely hard and requires analysis... I tried doing long way back...

@SarveshAhuja it takes one of infinite paths from one point to other.

vzn

there is new cutting edge research/ experiments measuring electron transitions that have mainstream physicists agreeing that bohr didnt have the complete story, and that new revisions to the theory are here. see eg quantamagazine.org/… — vzn 40 secs ago

Sarvesh Ahuja

Is it like a spiral or a jump?

Abhas Kumar Sinha

16:10

@SarveshAhuja It's non definite movement is the cause of existance of resonance structures.

@SarveshAhuja No one knows, no one has seen, so we don't assume both, but generalize them.

@SarveshAhuja But these paths have certainly a pattern, which causes interference.

Unfortunately nothing in real world/classical object can be used to explain it...

Sarvesh Ahuja

What Ki was thinking if such resonance structures occur,what resonance structures?:)

Sry..what kind of resonance structures

Abhas Kumar Sinha

@SarveshAhuja Resonance structures are needed in chemistry, because the electrons can be everywhere!, even at your hands, but there are different probabilities of having it at different places. When we draw resonance structures, we keep in mind to draw structures where electrons have most chances of being there (for example near electro negative elements)

vzn

← (coincidentally) recently emailed 5 top physicists leading/ investigating the area about an experiment that may reveal electron jumping dynamics using classical fluid dynamics, havent heard back from any yet... "the search goes on..." :(

Abhas Kumar Sinha

@vzn lol

I'll be back.

Sarvesh Ahuja

No..the type of resonance(waves)I was talking abt in my questions physics.stackexchange.com/q/522694/187127is different

pits abt the resonance in space time

*its

Abhas Kumar Sinha

16:18

I don't understand ur question.

Sarvesh Ahuja

if possible?!

PM 2Ring

@SarveshAhuja Our classical ideas about trajectories don't apply very well to electrons. However, we can say that electrons move smoothly, they don't jump around in a discontinuous fashion. Please see knzhou's excellent answer:

78

A: Do electrons really perform instantaneous quantum leaps?

Do electrons change orbitals as per QM instantaneously? In every reasonable interpretation of this question, the answer is no. But there are historical and sociological reasons why a lot of people say the answer is yes. Consider an electron in a hydrogen atom which falls from the $2p$ state...

Sarvesh Ahuja

In in case of rather instantaneous or extremely quick motion,the curvature in space time due to the electron’s mass would relax(where it was present initially,and then cause curvature at the final place it has moved to...

Thanks , I will read it and check back..

@PM2Ring

It makes kind of sense..but I don’t know what these symbols mean... |𝜓(𝑡)⟩=𝑐1(𝑡)|2𝑝⟩+𝑐2(𝑡)|1𝑠⟩.

cuz I haven’t learnt all of this

still in high school

Abhas Kumar Sinha

@SarveshAhuja It's Bra-Ket Notation aka Diarc's Notation.

PM 2Ring

Practically speaking, we can generally ignore the changes to spacetime curvature due to the movement of electrons. The electromagnetic effects are far greater, by around 40 orders of magnitude. So unless your experiments can measure stuff with 40 significant figures you won't even see those gravitational effects.

Abhas Kumar Sinha

16:29

It's just superposition principle which says $$ \psi = \sum_n c_n \psi_n $$

Where, $c \in \mathbb C$

@SarveshAhuja Quantum Gravitation is very controversial, but we generally don't see those effects.

Sarvesh Ahuja

@AbhasKumarSinha, all I see is sumbols and $ signs in ur reply..

Abhas Kumar Sinha

@SarveshAhuja Use Latex Plugin

Sarvesh Ahuja

What’s that

from where

Abhas Kumar Sinha

ψ=∑_ncnψn

ψ=∑_n c_n ψ_n

^ this one

Sarvesh Ahuja

So basically our quantum theory and general relativity show some effects through math but might not nessecarily model our world

is it?

Abhas Kumar Sinha

16:35

@SarveshAhuja no

@SarveshAhuja applies to all theories, we may get some results which might be useless, but the thing you are talking about, holds both correctly.

Sarvesh Ahuja

but together..as in the question?

Abhas Kumar Sinha

@SarveshAhuja yes, it's called, Quantum Field Theory

Sarvesh Ahuja

then I was just wondering, if we are able to replicate the motion of the electron, is it possible to create more significant effects in space time and perhaps create such resonating depressions to tear space time(to create a temporary black hole)

Abhas Kumar Sinha

@SarveshAhuja I don't see any point of thinking about spacetime, it's a altogether a different thing and has nothing to do with quantum mechanics

PM 2Ring

@SarveshAhuja Ok. That equation just says that at the start of the transition the electron is in the 2p orbital, and at the end of the transition the electron is in the 1s orbital. During the transition the electron is in a superposition of the 2s and 1s states. If you try to observe the electron during the transition you will always observe it in either the 2p or 1s state, never in some other state.

And the equation tells you the probability of measuring it in each state. So near the start of the transition, the probability is close to 100% that you'll see it in the 2p state, near the end of the transition, the probability is close to 100% that you see it in the 1s state. And in the middle of the transition the probability is 50% that you see it in 2p, and 50% that you see it in 1s. This is fundamentally the way that probability works for any quantum transition.

Sarvesh Ahuja

16:43

But if such motion exists in the quantum world shouldn’t we be able to do the above

Abhas Kumar Sinha

@SarveshAhuja I'd suggest you to read some stuff on QM/QFT (the mathematical way) so that you won't get confused...

Sarvesh Ahuja

Where can I learn a of this for beginners ,cuz I don’t have much mathematical knowledge besides till 12th Std of Indian high school

Abhas Kumar Sinha

@SarveshAhuja I read in 12th std. Indian High School. I think mathematical part is okay for it.

Sarvesh Ahuja

Oh

PM 2Ring

@SarveshAhuja Quantum theory and general relativity are both very good models, but we don't know (yet) how to combine them into a united quantum gravity theory. But that's mostly ok, since we only need quantum gravity to model very extreme situations, like at the core of a black hole, or conditions during the very early phases of the Big Bang, when the universe was less than 1 nanosecond old.

Abhas Kumar Sinha

16:50

QM is very easy, easier than classical mech...

Sarvesh Ahuja

Thx for it time

*your time

ill

get back to you soon

PM 2Ring

@SarveshAhuja Ok.

Abhas Kumar Sinha

Does $U \times U^{\dagger} = I$?

@PM2Ring

or $[(1,1,1,\dots),(1,1,1\dots),\dots]$

PM 2Ring

@AbhasKumarSinha Does this help? physics.stackexchange.com/a/494763/123208

Abhas Kumar Sinha

@PM2Ring Oh yes, thanks :)

Physics Meta

18:37

0

Q: Can this question be slavaged?

I am making an analogy between the history of arts and physics and wanted to make sure that the physics side is correct. As such, the question is probably not a good fit for this site, but maybe it can be salvaged by rephrasing? Or maybe someone can answer it here? We can try and see the prog...

discussion support

Johan Liebert

18:52

0

Q: Do we imagine the World?

If yes, please elucidate what must be the case such that we can make the statement : "We imagine the World". If no (or if the question is meaningless/absurd) please demonstrate using logical arguments that it cannot be said that "We imagine the World".

philosophy-of-mind philosophy-of-language

Looking at the this (👆) question it seems to me that it is quite hard to close question on the basis of meaningless-ness on Philosophy.SE (the OP might ask what does it mean to be meaningless?)!

user434058

-3

Q: What kind of propulsion would a Scrubbing Bubble use

The brand name bathroom cleaner Scrubbing Bubbles has a mascot, that is a bubble with a rotating bush on the bottom. Please view this video to see an example of the motion. I would like to know what this kind of propulsion is called, and or what it would take for a real life device to move arou...

kinematics propulsion

user434058

I already used an off-topic(blatantly off-topic) flag for the above 👆 question. Should I use the spam flag?

Johan Liebert

@FakeMod it looks to me that the post has been created for promoting the product!

@FakeMod I'm going to flag it as a spam.

Johan Liebert

19:46

4

Q: Determine Earth's radius with stopwatch at sunset

This question appeared on Bangladesh physics Olympiad 2014, Sylhet, Bangladesh for students of class 9 and 10. I really tried to solve this but i failed. Please help. Suppose that, while lying on the beach near the equator watching the sun set over a calm ocean, you start a stopwatch just as...

homework-and-exercises earth geometry

Meh! It became a HNQ.

Kyle Kanos

@FakeMod i don't think it's spam, but i don't think it's on topic either (mostly because it relies on one to either watch enough TV to be familiar with the product & commercial or jump off-site to watch a commercial)

Aaron Stevens

20:11

@JohanLiebert I have flagged to be removed from HNQ

Novalium Company

20:23

I want to plant a long-term financial seed that will grow overtime. What are good options? Index funds seem to be the choice for now.

JMac

@AaronStevens I'm really disappointed how many upvotes have been given for those answers... It's just "I tried to solve this but can't help please", like a super blatant homework question.

Aaron Stevens

@JMac Yes, I agree. And they are from users who I would think should recognize this.

Novalium Company

@JohnRennie I need you on this one

Kyle Kanos

@AaronStevens i ran out of close votes before i saw this, but i left some comments

Aaron Stevens

20:41

@KyleKanos Always the worst

Rob saved the day

Kyle Kanos

that he did.

Jake Rose

20:54

Can anybody explain this in a nice way? I can't see it myself

$\bf [\delta a \cdot P, X] = \delta a \Rightarrow [P_i, X_j]=\delta_{ij}$ as it is true for arbitrary $\bf a$?

Kyle Kanos

don't use \bf, it's deprecated

Jake Rose

Whats the new syntax?

@KyleKanos Do you know anybody in cambridge??

Kyle Kanos

\mathbf

Jake Rose

I'm currently doing astro there

Kyle Kanos

no i do not

Jake Rose

21:04

Lot's of computation astrophysicists!

ahhh sad

Kyle Kanos

i mean, i've heard of longair (through his book), but don't know him

Jake Rose

He's in the other astrophysics department so I haven't met him sadly

A lot of the people in my department are simulation based actually come to think of it

Kyle Kanos

read this guy's papers too: ast.cam.ac.uk/people/Eugene.Vasiliev

Novalium Company

If the universe is only 14 billion years old, how can it be 92 billion light years wide?

►

Still hard to wrap my head around that :P

PM 2Ring

22:20

@NovaliumCompany See people.smp.uq.edu.au/TamaraDavis/papers/SciAm_BigBang.pdf by Tamara Davis & Charlie Lineweaver, and maybe also their classic paper: Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe. The paper does have a fair bit of mathematics, but you can probably skim over the equations & look at the relevant graphs.

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