01:00 - 16:0016:00 - 22:00

1:46 AM
kkkk I would like to drop a bomb...
Do you think that Sabine Hossenfelder is a anti-science person?

3 hours later…
4:44 AM
@M.N.Raia no, she is a well established physicist. She had to leave academia because she didn't manage to get off the postdoc treadmill, and I wouldn't blame her for being a little bitter. She has a tendency to be critical of what she sees as hype in physics, and that has earned her a bit of a reputation as "anti-science", but I think this is unfair.
I guess you're thinking of her latest video Particle Physicists Continue Empty Promises. The title is a bit click-baity, but she is making what seems a good point to many people. She objects to the way many physicists are pushing to build a collider much larger than the LHC because she feels there isn't the theoretical justification for it.
Not everyone agrees with her (I don't) but she is presenting a point of view that does have its supporters in the physics community.
Deleted

5:53 AM
Never heard of that channel before...
Do y'all know about 3 blue 1 brown?
or something similar? It's a good Channel tho
Although, I spend very less and rare time on Youtube, but I watch most of his videos... :)

You might also like the Mathologer channel, though he is a bit more hardcore than 3Blue1Brown.

@JohnRennie Yes, I've subscribed him too.
I like those channels only which have a hardcore mathematical interests, otherwise stories bore me

I didn't know that. I imagined she in her room writing papers and going to lectures

Hi all,

hi

6:03 AM
0

As we have developed the idea of Electric Field Lines from coulomb's law. If two equal and opposite charges are in plane all the effect of electric field vectors add to line joining the two points, means all the electric field lines of forces contribute to coulomb's force. When more than two char...

@123 Do you know vector laws and principle of superposition?

Yes dear i know.

Then what's the problem? You can find the field line components of more than 2 charge particles of any point
or you can reconstruct them too!

I made animation. not just the Electric Field join the contribute to coulomb force. I found the Field above and below added as vector addition so resultant is again straight line.

It's possible to have charges such that the some particular field lines are straight
no problem here...
Although there is a tiny singularity on that line, but it's straight

6:08 AM

magnitude may also vary...

With this fact i observed that that not just line join the point contribute to coulomb's force all above and below forces addition contribute to force

Yes, more the electric field, more will be the Coulomb's force

Hi @JohnRennie , Thank for your always good answers. Pls also explain this.

@123 hi :-) I saw your question when you posted it, but it isn't clear to me what you are asking.

6:11 AM
@Azmuth What if more charges on the plane. The electric field distribute between charges. So the coulomb force must also reduce.
But we apply coulomb's law as it is, why

@123 Yes, there are some specific points where coulomb's forces may vanish to 0...

@JohnRennie Pls ask me, What is not clear.

@123 Electric field lines are representation of Coulomb's forces for a point....

@123 I'll wait for Azmuth to finish otherwise the conversations will get mixed up.

@123 Oh! I guess you want to ask, what happens to field lines of the net force by addition of Coulomb's forces reduce to 0?
@JohnRennie Honestly, I'm still trying to understand the question....

6:14 AM
@Azmuth If it reduces , Why again uses F = K qQ/ r^2 . Means more than two charges it should be useful. Because it only worked when all the E worked on one charge.
@JohnRennie Pls contribute. I am trying to explain again.

@123 The formula should be summation from (i=1) to n K (q_i Q)/r^2 for the force of all the charge on Q.
If there are n charges
@123 Would you mind if I suggest you some good book or material? You just have to read the chapter -1 of it, then try asking the question if your doubt persists? or you guess there are better ways?
@JohnRennie Most of her papers have 1 to 2 citations which she cited herself....

Case I : Two equal and opposite charges are in plane. Between two charges let say +q1 and -q2 , Let say q1 has 10 electric field lines. All 10 electric field line attract q2.

yes
@JohnRennie Well, another interesting paper :P arxiv.org/pdf/1806.04641.pdf

Case II : If more than two charges. q1 , q2, q3 are in plane. q1 has again 10 electric field lines . But 5 lines attract to q2 and 5 E attract q3. So, force must be reduced.

@123 Number of field lines are not a measure of force, actually, it's the density of field lines per unit area that determines the force!

6:21 AM
But in calculation we use coulomb's force. So q1 10 E attract q2 and 10 E attract q3. Why...

@123 Because you are thinking that number of field lines determine force, its wrong. It's the number of field lines per unit area, that determines the measure of force

@Azmuth but this field density per unit area should be reduce when more charges added in the plane.

@123 Depends where are you are at. For example, the number of field lines per unit area between 2 changes are much much higher than somewhere away at infinity

Because now one charge contribute to attract more charges at different place in a plane.

So?

6:26 AM
Put other way my question dear member. Does effect of adding charges reduce coulomb Force of q1.
@Azmuth Dear it should reduce. But in calculation we use the same Coulomb's Law formula. It should not valid.

Depends where you put other charges with respect to q1
@123 No, we don't use Coulomb's formula! We use principle of superposition, both are different

Pls share superposition formula. But in elementary book we use coulomb's force formula. i share with you

Just a bit different than Coulomb's formula..

Three positive charges are placed on a side of an equilateral triangle. Determine the net force on charge q1.

Just 1 second

6:30 AM
can i share the pictures here

yes
there's an upload button on the right side.

k. dear

Equation (1.3) is superposition formula...

@Azmuth dear i am doing the same. but in my analogy it should not valid.

@123 You didn't notice that summation sign here!
and also that e_ri thing

6:34 AM
Yes dear i dear i have noticed summation sign. let me share a picture

It it vector addition. Vector addition of 2 or more vectors can be smaller than individual vectors or even 0...

may be you guys can understand my question better

Ummm.....

Two similar charges. Electric Field and Potential map
Two opposite charges.
Dear Pls see the pictures. My question is that coulomb force between two charges means all the force of q1 contribute to attract or repel q2.
but , when more than two charges whether it lie on the same line or in a plane. q1 force must reduce. because now part of q1 attract another charge and partial force attact or repel another charge. force should reduce.
In mechanics we have 10N force (as charge have). If i apply a force 10N on a box. Then i apply the same force on two boxes it should distribute between two boxes. but coulomb's law apply same force on each charge. It is not distributed. Why
@JohnRennie Pls explain this.
As you can see in pictures of 4 charges not all electric filed goes to the other charges. as in case of case charges. It should reduce and we can not apply coulomb's force
@JohnRennie @Azmuth dear did you get my point of question.

7:05 AM
If still i don't clear to you guys. Can we talk on mic it is possible in chatroom. If anyone interested.

@123 hi
22 mins ago, by 123
In mechanics we have 10N force (as charge have). If i apply a force 10N on a box. Then i apply the same force on two boxes it should distribute between two boxes. but coulomb's law apply same force on each charge. It is not distributed. Why
Let's pick up on this comment.
Give me a moment to draw a diagram:
Suppose the force is being exerted by a spring between the boxes. It exerts a 10N force on the right box.
If I understand you then you are saying we could add a second box like this:
@123 And now the 10N force is being exerted on both boxes i.e. the force on each of the two boxes on the right is only 5N. Is this what you mean?

@JohnRennie Thanks for the reply and sharing your knowledge. Yes you are right. May be this way i can explain better.
Electric Field Lines/Intensity (E) span complete space radially outward by charge q1. If i placed opposite q2 charge in space at some distance all E of q1 curved and attract q2 not just straight line. Because when i added upward and downward E vector there resultant is also straight line. I can come up with this result all E contribute to attract q2. not just E of straight line.
ecause the above and below forces also add up to straight line. so they are also contributing in attraction. What if i placed q3 charge. Now q1 electric field not all go to q2. because in their path there is another charge. Coulomb force should distribute between charges.

OK, but now suppose we add a second spring like this:

@JohnRennie Hmm.. Yes

Now there are two springs, both exerting a force of 10N, so now the force on each of the two boxes is 10N making 20N in all. Then the force on the left box would be -20N to the left (by Newton's third law). Yes?

7:20 AM
Yes.... :)

Well this is what happens with charges. In effect there is a "spring" between each pair of charges.
The "spring" between charges is the electrostatic force.

It should also same between charges.
Now in this case all the force comes from one place. Means the span of force is straight line. But in the case of charges the force distribute in 3D space there span is whole space.

With three charges it would look like this

@JohnRennie for the contribution. My question is about span. In case of mechanics problem all the force (line of action) in the same line not distributed in the whole space 3D. But In case of charge it distributed in the 3D space.

The field is spread out through 3D space, but I think we need to be careful about the difference between the field and the force. The force acts only at a single point i.e. at the position of the charge.

7:28 AM
and all the E of charge moved their direction and to attract/repel another charge.

The force is simply F = qE where E is the value of the field at that point

@JohnRennie Yes Ahaa.. I think you got my point. Now you can tuned me better.
@JohnRennie Pls explain me field according to my problem in question.

@JohnRennie if we consider the whole universe as a system then will the center of mass be moving with a constant velocity or be at rest ?

@123 what isn't clear about the concept of the electric field?
@Ankit how could you tell the difference? You can measure your velocity relative to the universe as a whole, but how would you measure the velocity of the universe as a whole?

I can understand the mathematics of Field and can extract physical results from it. But sometime found problem in understanding to connect with physics and physical world. That's why i asked weird questions.

7:36 AM
@JohnRennie although there is nothing outside the universe but can't we imagine an observer seeing the universe expanding from outside ?

@123 The concept of a field is a bit weird once you start thinking about it. As you say it is mathematically well defined, but what actually is it? If you have some electric field and you point to some position in space what exactly is it that is present at that point due to the electric field?
And there isn't a good answer to this.
And the end of the day what physicists do is construct mathematical models that correctly predict what happens when we do an experiment.

When i draw the electric field as per function found all E of +q1 contribute to attract -q2 it moves change their direction. but if we placed q3 in the path of q1 E. It steal some part of the E which could not go to q2.

@123 that's where you are going wrong.
Charges do not "block" fields due to other charges.

@JohnRennie Ooohh.. I see

7:44 AM
yes i understand charges do not block field. But how possible for q1 the same magnitude of force apply on q2, q3, ... , qn

Do you mean how can q1 simultaneously exert a force on more than one other charge at the same time?

I means q1 has 10 Electric line in 3D. When only q2 in place all 10 E of q1 moves and attract q1. When q3 is also in place now how possible all 10 E of q1 goes to q2 and all 10 E goes to q3 at the same time. because q1 has only 10E not 20.
@JohnRennie Yes yes.... Exactly what i mean.

The field lines are a way of visualising the field. Field lines are not "things" - they do not actually exist.
The force can't be calculated by counting field lines.

@JohnRennie Yes i know this is just an idea to understand, visualizing and adding as vector.

Right, but you seem to be saying that because a finite number of field lines have to be divided between two different charges then the force per charge must be reduced.

7:50 AM
Yes i know Force can not be calculated by counting the field line. I have just used it as an example . So, i can explain my question. you already explained my question better.
How can q1 simultaneously exert a force on more than one other charges at the same time.
@JohnRennie May be my question part of it. Because when i placed q2 all force and direction of q1 changes.

@123 because q1 doesn't directly interact with the other charges. q1 creates an electrostatic field around itself, and then that field interacts with the other charges.
The field will interact with any number of different charges.

It means q1 can apply same number of forces on n charges. Does it possible to explain this idea by E

Yes. The field created by q1 simultaneously interacts will all other charges in the field.

It means direction of field changes by placing other charges not force.
All the charges contribute to change in field which can be check by positive test charge. But the magnitude force by each charge on every others charges is same.

8:07 AM
Suppose you have n charges. The total field is just the vector sum of the n fields from each of the n charges.

And if placed new charge q5 within the q1, q2, q3, q4 charge system it also contribute in change in field.

But remember that a charge doesn't feel a force from its own field, just from the other n-1 fields of the other n-1 charges.

@JohnRennie Yes like example of sphere inside the sphere there is no field.

So to calculate the force on the charge q3 (for example) you add up the fields from all the other charges, E = q1, q2, q4, q5, etc, and then the force on q3 is just F3 = E q3

What is the purpose of place where E is zero if placed a charge in that region it create own field and create a new E system

8:11 AM
Let's take an example e.g. we could have q1, q2 and q3 at the corners of an equilateral triangle so the field at the centre is zero. Yes?

What information/purpose we can get from E, it does not matter whether field is zero or not. because as we placed new charge it create new system.

I'm not sure what you are asking ...

Means as i shared a picture. Where Electric Field is zero how can we use this E zero position. What information it give us, what is the application of Electric Field map.
Because as i placed new charge it creates its own field and interact with other. The whole system again reestablished and create new electric field.
What is the benefit to get the information of knowing E map. or potential map.
Is there any answer for that so, i need to explain my students. How it is possible for q1 can apply same force on every single charge.

The field is a function of the values and positions of all the charges. If we know the field at every point in space then we can work out where all the charges are and what their values are. But we can't do this just by measuring the field at one point. We have to know the field everywhere.

@JohnRennie Give me your brain... :-)

8:23 AM
@123 you wouldn't want it, it's worn out from overuse :-)

Pls explain this. How charge q1 apply same force on every single charge. Is there any explanation. Because idea E does not give us that information.

The charge q1 creates a field everywhere in space, and that field exerts a force on each and every charge within it.

@JohnRennie I am young enough to use it more efficiently.
@JohnRennie Hmm... but they can ask same question if q1 has 10N force how q1 apply 10N on q2 and 10N on q3 and so forth. What is the explanation of this.

It's like when I drew the boxes and springs. In effect the field creates a spring between q1 and every other charge in the field. There isn't just one spring that needs to be shared. The field creates as many separate springs as there are other charges.

if q1 10N applied on q2 it is regularly consuming in attract/repel q2. They don't have more force to apply on other charges.
@JohnRennie Pls explain 3 box spring system.

8:31 AM
When q1 interacts with q2 is doesn't "use up" q1's field so there is less available to interact with q3, q4, etc.

@JohnRennie Thanks a lot for sharing you knowledge. If time permits you i also wanted to know the idea of Work Done of charge and Potential.
@JohnRennie Hmmm... I see. Now it is very clear to me. It means q1 10N force not all apply on q2. It distributes within whole system.
Am i right

2 hours later…
10:11 AM
Hey!

10:28 AM
Hey?

Hey.

10:43 AM
Hey...

$$E_{\text{BV-BRST}} \; := \; \underset{ \array{ \text{anti-} \\ \text{fields} } }{ \underbrace{ T^\ast_{\Sigma,inf} } } \left( \underset{\text{fields}}{\underbrace{E}} \times_\Sigma \underset{ \array{ \text{ghost} \\ \text{fields} }}{\underbrace{\mathcal{G}[1]}} \times_\Sigma \underset{\array{ \text{auxiliary} \\ \text{fields} }}{\underbrace{A}} \times_{\Sigma} \underset{ \array{ \text{antighost} \\ \text{fields} } }{\underbrace{A[-1]}} \right)$$
The horror

11:19 AM
eh, looks pretty tame

11:30 AM
@knzhou Hey, this is not on the topic of arrival times but I looked at your github and your physics notes are beautiful. Is there any chance you have a template or .tex of some kind that I could look at?

Hi... Guys.
Any one can explain the topic what i discussed?

11:46 AM
Afternoon everyone

Hello

2 hours later…
1:43 PM
yeho!
How to become a pro physicist?
Add one more term with anti perfix
Sitter Space is for common physicists, Anti-desitter space makes you pro physicist
matter is for common physicists, anti-matter make you pro physicist
Photons is for common physicists, anti-photon is for pro physicists

@Ankit Others have explained most of it
HNQ is a... problematic... mechanism
if you know where to look, there's plenty of public record of me bashing it
it was fixed about a year ago, which made it substantially better
but it still has a tendency to pick up a variety of awful threads that do a poor job of representing the site to a wide audience, mostly due to self-reinforcing feedback loops that favour lowest-common-denominator content

2:01 PM
I think my biggest issue with it right now is that we're not good at preventing off-topic questions landing on it. Our close review queue is too slow to stop a HNQ.
But that's less an issue with HNQ and more an issue with our general lack of close reviewers.

there's definitely a certain type ('flavour') of question that the HNQ mechanism is much more likely to pick up
which is basically what I was commenting on here

oh, it actually became hot

You are right that I was in the end simply advertising a question I had answered in a way that would benefit me

but apparently only briefly, judging from the low view number

but I wasn't doing anything beyond posting a link; people can vote (including downvoting) as they see fit
and as mentioned previously, nobody can really control what HNQ picks up
as far as 'greed' goes, though
it is all just fake internet points
though gamification as an engine to make it easier for people to contribute is a large reason of why this site works well
I stopped gamifying rep a long time ago
if anything, I gamify how much rep I've given away

2:07 PM
I had also pointed out (don't see it anymore) that you had literally answered like 6 questions that day, let alone the last week, and that was the only one you promoted.

seems the whole conversation was nuked, it wasn't exactly a constructive discussion :P

(and in that race I'm winning by about 20,000 rep, FWIW)

Have you given the most rep on the site?
well, the physics site

oh wow it's not even close lol

2:13 PM
but that said I would like to get a Legendary badge at some point, in which pursuit I still need to get 200rep on 41 more days, hence this comment.
@Charlie ;-)

I only need 136, so you better watch out, I'm super close to you.

@JMac yep, I can see you closing in
though actually, it seems @ACuriousMind is something like three rep-cap days away from the Epic badge?

If you can just stop answering for a few years, and also ask some really popular but easy classical mechanics questions when you know I'm online, that would be great.

oooooohhh, and @rob is just one cap short of the badge?
actually, y'know what
if there's somebody with 49 rep-caps under their belt, I will happily donate 200 rep to nudge them over the edge
T&Cs: somebody else must nominate that user, and the nomination must point out an outstanding answer by that user, along with a short argument for why that answer is worthy of a bounty

2:24 PM
this query has the stats
.... which are probably wrong
@ACuriousMind kudos =)

@EmilioPisanty I don't think bounties count towards the rep cap
@EmilioPisanty The query probably undercounts the number of rep cap hits because it doesn't count deleted votes

@ACuriousMind they do ;-)
@ACuriousMind oooofff. If that's it then that's a tough one to query for.

you can hit +200 in a day and then later some user that upvoted you gets deleted, so the vote is gone but the counter towards the badge isn't taken away

Hi everyone
Can anyone of you suggest a book on moleculear physics
?

@EmilioPisanty Yeah, I don't think deleted votes are accessible in SEDE (and probably not even internally, since SE always stresses how they can't easily restore deleted accounts or invalidated votes).

2:35 PM
@JackRod I have good memories of Physics of atoms and molecules by B. H. Bransden and C. J. Joachain.
(but it's been years since I've seen a copy)

2:56 PM
**I am, whatever you say I'm**
**If I wasn't why would you say what I'm**
I've a problem with my Phone, it has 600mAh Battery and drains 6-7% in 3 hours, I feel like I'm wasting too much time on it.

It doesn't have a 600mAh battery :-)
6000 mAh possibly.
And 6-7% in 3 hours is nothing. I mean, come on, you're clearly not even trying :-)

Yes, 6000 mAh, (just one 0 left out)
@JohnRennie What should I try?
Do you play Among us?

No. I only use my phone for making phone calls and texting. Very boring really.

@JohnRennie I don't use hone for texting... Only reading..... not even whatsapp...I just ave 4 apps installed, JIO Care, Adobe acrobat, Adobe scan, Aarogya Setu (COVID19 Tracker)

Ah, yes, now you mention it I do have a covid tracker installed.

3:09 PM
which one? Official ones?

So far it hasn't sent me any alerts.

We have Official ones - github.com/nic-delhi/AarogyaSetu_Android It does sends alerts to me everyday

@JohnRennie hi sir

@Azmuth Do you guys still have a lot of cases?

@JMac it is decreasing

3:21 PM
Well at least that's good.

Today it was approx 54k earlier it was 98k

@JackRod hi :-)

And even death rate is decreasing

@JMac no, 0 cases in my district but yes there are high risk people here
i.imgur.com/dwkRa7F.jpg

@JohnRennie how are you sir?

3:23 PM

Oh okay you guys aren't doing nearly as bad as my neighbors to the south. That's good

The thing is India is about to get at least 50-60 million cases by next year Feb
That's scary

@doublefelix Sure, send me an email and I'll send it to you!

I am going good with my qm book

@Azmuth According to who? Is India planning on just stopping all measures to prevent spread? If your numbers are fairly low right now I can't see how it would expect to bloom that much again unless people just stopped caring.

3:26 PM
But looking for some good physicists on net related to this

@doublefelix About the arrival times, I would like to think more about it, is there any way you can post a copy of your thesis?

Does any body have any suggestions for any specific u tube channel

@JMac Population is billion and population density is multiple times higher than USA

@JMac @JohnRennie
Have any suggestions

@knzhou Hey, I was looking at yout GH notes, I do really like them :)
@JackRod for what?

3:28 PM
Quantum mechanics
College lectures are boring

@JackRod Take a David Griffiths' Book, I don't seem to find an easy book than it.

@Azmuth Yes, but you've only had like 7 million total cases so far, in 8 months of the virus. I'm not sure why it would expect to bloom even more in the next 4 months. US is less dense, and lower population, and they've still had more total cases than India. I really wouldn't expect India to explode like US did because US really screwed up their response; unless India just stopped trying to prevent spread...

@Azmuth I thought to read as suggested by sir @JohnRennie but then my college has prescribed a different book
So do u have any recommendations related to that

@JMac The cases increases exponentially

I mean channel

3:32 PM
@JackRod What book your college prescribed and what branch you are in?

@Azmuth India seems to be steadily decreasing cases in the last month though... I'm just wondering where you're coming up with such a huge number when all the data I see really doesn't suggest it's going to explode there.

@JMac Second wave is yet to come...

Dear physicist pls suggest the best books for electricity and electromagnetism. For undergraduate which explains physics way. And seperate book for math way

First wave is lowing down
@123 Irodov's! It's free on Internet! If you need even simple book, I guess NCERT... :)

@Azmuth What exactly is the "second wave"? What is going to cause that? IDK it just seems like you're assuming something far worse is going to happen when the data doesn't back it really.

3:34 PM
Quantum physics by HC Verma

@123 We have questions on the site for most topics. For EM, see physics.stackexchange.com/q/142419/50583

@JackRod That's pretty outdated... But a good beginner's book

Thanks dear. I have seen HC Verma. But in overview. Now I will read it carefully.
I wanted to know the concepts with deeper level in physics concepts way

@JMac Cases happen in a wavical manner. See Italy/Spain, if the number of cases decline, its a sign for a second peak to start
Schrodinger's score!

@Azmuth the sign for the second wave is when the cases go up again, not when they decline!

3:37 PM
@Azmuth India is still in decline right now. And you're literally calling for almost a 10 fold increase in cases in 4 months when the virus has been spreading for like 8. I just don't see where you're pulling these estimates from at all.

Cases are bound to go up! Not even 1% of the population is infected yet!

In my country peoples are not taking corona seriously.

@JMac I wouldn't be surprised if that happens during second wave... because all the lockdown restrictions are being gradually removed

They said all news are fake.

@123 USA?
or India?

3:38 PM
Nope. Pakistan. Neighbor of India. But conditions are better here.

oh okay..

People's here said there is no virus. It is fake.

@Azmuth "The thing is India is about to get at least 50-60 million cases by next year Feb" This sounds a bit confident to state for something that could happen (and again I don't think the statistics really support such a huge bump in that period of time)

@JMac No, July
Not Feb... I guess cases will keep on declining till December

15 mins ago, by Azmuth
The thing is India is about to get at least 50-60 million cases by next year Feb

3:40 PM
I'm using SEIR Model to model the pandemic.

are you just saying random numbers and months?

@Azmuth So you're just throwing out random stuff even you don't believe and stating it like it's right?

@ACuriousMind Yoo! Nooo, not feb

...

3:41 PM
@JMac I'm just trying to make guesses using SEIR Software, I'm no god, but I'm confident that's bound to happen :P XD
Also if you don't mind starring this :P github.com/ryansmcgee/seirsplus haha :)

@Azmuth If you're making guesses don't state it as a fact. And then when someone questions where you're getting the info from, it's usually a good time to mention it was just a guess.

@JMac K... There's no fact about Corona Prediction either... All of world is a guess and all of world is an Illusion! - Abhas Kumar Sinha

@Azmuth I don't find anything funny about throwing out random guesses as fact, especially when it takes you so long to say that you don't actually have any reputable source for it.

@ACuriousMind Okay, I'll come here to tag this message in July

@Azmuth Tag the message where you said February?

3:45 PM
@JMac June one
*July one

If you're just going to change your guess when someone calls it out, I don't see why we would think it any more than coincidence even if you wind up being right.

3:59 PM
I'm just adding it here, If anyone requires my Entrepreneurship notes (Part -1) Notes here

01:00 - 16:0016:00 - 22:00