The h Bar

12:26 AM

@Obliv good academic/ scientific work is "selfless" in general. likely "our kids" will face many of the issues the superintelligence book raises. there are "only" ~2 decades between generations.

@SirCumference try Code Review

Sir Cumference

@vzn Oh crap

Wrong person, wrong chat

Sorry

user507974

12:47 AM

guys

is there a name for this equation

${C(x,t)-C_s}\over{C_s-C_0}$ C_s might be some other subscript in many contexts

DanielSank

1:40 AM

@BernardMeurer <3

Bernard Meurer

@DanielSank <3

That was positively unexpected hahaha

I literally just sat in my chair

DanielSank

@ChrisWhite I have figured out SQL in the past...

What's "gini"?

@BernardMeurer Then our meeting was fated.

Bernard Meurer

Gini is a coefficient to measure distribution

DanielSank

Forget that blonde.

Bernard Meurer

it's used to measure how unequal wealth is distributed in countries usually

At least that's the gini I know

Never! She only cooks texan <3

DanielSank

1:43 AM

@BernardMeurer I'm not even sure what that means.

What is Texan food?

Wait a second, she's American?

Bernard Meurer

Yeah she is dood, hadn't I mentioned that?

Lel

DanielSank

@Jiminion Is that a Groucho Marx line?

@BernardMeurer yes but I was confused because the information was conveyed through some bizarre description of her sister's friend or some such thing.

Bernard Meurer

@DanielSank I have trouble being clear a lot of times

FreezingFire

5:04 AM

I hope this is the right place to request an answer to the question here: physics.stackexchange.com/questions/250330/…. A short description: in electrostatics, if some conductor is earthed, what happens to it? If this isn't the right place, where am i supposed to request answers of willing users? Thank you very much!

John Rennie

@FreezingFire the "Earth" behaves like a giant capacitor i.e. you can push charge onto it or pull charge off it without changing its voltage (very much).

FreezingFire

Umm, yes, but actually i am not able to apply that concept to a specific problem (i.e. use it mathematically), that is mentioned in the question (too long to put here). Could you help me with it?

user54412

@Slereah There are the occasional papers I never read too closely. Once we discovered that galaxies really are distributed homogeneously beyond a certain scale, interest in this waned a lot, since it probably would only ever be a small correction to things.

FreezingFire

@JohnRennie Umm, yes, but actually i am not able to apply that concept to a specific problem (i.e. use it mathematically), that is mentioned in the question (too long to put here). Could you help me with it?

John Rennie

5:24 AM

@FreezingFire OK let's take your case (a). Plate B starts off with a charge +Q, so it's attracting electrons onto plates A and C.

However electrons can't flow onto plates A and C because there is nowhere for those electrons to come from. OK so far?

FreezingFire

@JohnRennie Yes.

@JohnRennie Actually, when the plates are not earthed, i am able to tell the charge, distribution as i have said in my last comment on Farcher's answer! But anyways, i would like to hear you out completely...

John Rennie

When you close the switch S1 you are connecting the plate to an effectively infintiely big ball (the Earth) of mobile charges. So charge flows off the Earth and onto plate A. Because the capacitance of the earth is so big there is no assciated change in potential.

So a charge -Q flows off the Earth and onto plate A.
Plate C is unaffected because it still has no way for charge to flow onto or off it.

skill patrol

Congratulations @ChrisWhite and @JohnRennie on your room owner appointments.

user54412

^ the temptation to delete that message just to be ironic...

skill patrol

:-D

it's nice to see non-mods get the job

FreezingFire

5:36 AM

@JohnRennie Okay, so what i understand from this is that the Earth remains practically unaffected, but then why the specific value of -Q appears on the plate? Why not some other arbitrary value of charge? Again pondering a bit more, it seems to me that the two plates want to behave like a capacitor, so that they have equal charges on opposite plates. Am i correct in thinking so?

John Rennie

Yes, the plates are behaving just like a capacitor. Indeed they are a capacitor.

I'm trying to think of a simple way to explain why the charge that flows onto plate A is equal and opposite to the charge on plate B. Give me a moment to think about it ...

Actually I'm going to have to drop out for a bit. I'm currently working and something has come up.

Is it just the issue of why the charge on plate A is equal and opposite to the charge on plate B?

FreezingFire

5:52 AM

@JohnRennie Yes. I understand that the positive charge will attract a negative charge from the earth onto the plate A (because of attractive force), but i don't understand why only a value of -Q is attracted! It could probably attract a lot more (or less)! Also, i am not able to connect this to the concept that earthing "only" sets the potential of a point to zero. Thank you for your interest in this! :D

lucas

6:28 AM

Hello dear John Rennie.

Are you there?

John Rennie

I'm around, but I'm at work now so I may need to drop offline from time to time

lucas

Thank you.

I answered a question, but they downvote me.

Do they want me to leave this website?

Why they don't like me?

Can you help me to know?

John Rennie

This answer:

-1

A: plz solve my question

We use the polar coordinate. $\sum F_\theta=mgcos\theta=ma_\theta$ $a_\theta=gcos\theta$ While body is on the sphere, r is constant. So, we have: $a_\theta=R\alpha$ $\alpha=\frac{gcos\theta}{R}$ $\alpha d\theta=\omega d\omega$ $\frac{gcos\theta}{R} d\theta=\omega d\omega$ $\frac{g}{R} (s...

lucas

yes

John Rennie

The question posted by Bratin Kundu is just an attempt to get us to do his homework.

That is, he wants us to help him cheat.

lucas

6:34 AM

Did he downvote me?

John Rennie

And we don't do that in this site. I don't know who donvoted you, but I expect it was because you are helping someone cheat.

knzhou

@FreezingFire Earthing sets the potential of plate A equal to the Earth. That means the integral of the electric field, along a path starting at the Earth and ending at, say, the left end of plate A, is zero. If the plates are big, having plate A and plate B have opposite charge will guarantee this happens, because then the field outside the two plates will be nearly zero.

lucas

How can I know that it was cheat?

John Rennie

Because it's obviously just a homework question.

lucas

When I answered that question it wasn't blocked.

John Rennie

6:36 AM

Bratin Kundu isn't asking about any fundamental concepts in physics. He has just copied the question from his homework into this site.

lucas

If they continue like this, I loose features.

Comment, for example.

I want to help the others. I like learn and teach.

John Rennie

I understand that you want to be helpful, and that's why most of us are here on this site. But you help people most by enlarging their understanding of physics. Just doing their homework for them doesn't achieve this.

lucas

Thank you very much because of your time. May I ask a little question else?

Do you have time?

John Rennie

Yes, please ask.

lucas

Do you think I am stupid? May you tell your idea comfortably?

Sorry for my poor English.

skill patrol

6:45 AM

if you judge a fish by its ability to climb trees, it will go through its life believing it is stupid

lucas

I guess they think that I know nothing about physics. Do you think same?

Please simple sentences.

skill patrol

do you understand what my last post means?

lucas

I am using dictionaries

What do you think about my abilities?

skill patrol

even native speakers use dictionaries :-)

John Rennie

I doubt anyone thinks you are stupid. Your answer to the question is a perfectly good answer. My guess is that it was downvoted because you should't be encouraging homework questions, not because it was a bad answer.

lucas

6:50 AM

Thank you. Forgive me because of bothering you. I hope chat you in the future if you want. Thank you again. Good luck.

John Duffield

@Jiminion : of course fields really exist. According to Einstein, a field is a state of space.

skill patrol

7:12 AM

Do you @JohnDuffield have a thesaurus?

Slereah

hello

so anyway

Non-perturbatively, $\varphi^4$ is trivial

Do we know about the triviality or non-triviality of other interacting theories

(of the SM)

Like do we know if EM is trivial or not

Bass

@Jiminion Please note that almost all experts on this site do not agree with many statements by JohnDuffield.

Slereah

Why the "almost"

John Duffield

7:28 AM

@skillpatrol : sure.

John Rennie

@Jiminion Hmm, that's not my intention. If you think I'm getting a bit negative that's something I should look at ...

Slereah

Hm

In LFT, I guess that the energy is gonna be something like...

$$\langle \hat T_{\mu\nu} \rangle_\omega = \lim_{\Delta t \rightarrow 0}\int_{\varphi(t,\vec{x}) = \varphi_\omega(t,\vec{x})}^{\varphi(t,\vec{x}) = \varphi_\omega(t+\Delta t,\vec{x})} (\prod d\varphi(x)) T_{\mu\nu} e^{iS}$$

Does that sound about right

Slereah

7:57 AM

Does that sound like a slice of fried gold

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