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00:00 - 19:0019:00 - 00:00

12:00 AM
@Semiclassical "Traditional leadership qualities" might have been a better way to word it. But either way it points to the weirdness.
12:53 AM
Q: Have there been studies of "old photons" to see just how constant Planck constant has been?

uhohThe question Are photons aged? and answers therein have got me thinking: I vaguely remember hearing something about experiments where "old photons" were collected by large telescopes from very distant objects, and either their energies or their frequencies were compared to their wavelengths to c...

3 hours later…
4:22 AM
Unwilling ti change your belief no matter how many instances disprove it is a sign of dolitshness. In this case it is "weid" and "weir" slogan.
4:48 AM
5:42 AM
@Akash.B hi :-)
I have a question regarding propagation of sound through air
We know according to kTG air molecules are in constant random motion
Which means that the air molecules are disturbed
So sound was defined to me as propagation of disturbance s through air
@JohnRennie so my question is how's its possible to produce disturbance s on a disturbed thing?
The air molecules move very fast and they move randomly in all directions, so their motion averages out. This means the pressure of the air remains constant despite all this motion.
And a sound wave is an oscillation in the pressure i.e. the pressure increases and decreases slightly with time.
5:50 AM
I have another question
According to kTG
All molecules are in constant random motion ,right?
So if just vapourise a metal and kept it in a magnetic field will it create electricity?
The atoms of metal would just cut the magnetic field lines,right?
I have another question too
Let me leave it here
If the atoms in the metal vapour are just atoms, i.e. not charged, then they are not affected by a magnetic field.
If the gas is so hot that the atoms are ionised then the charged ions interact with the magnetic field in complicated ways.
Complicated ways?
This happens in the Sun where the H+ ions interact with the Sun's magnetic field and the motion of the ions is fearsomely complicated!
6:02 AM
Okay let me google
@Akash.B see here:
Magnetohydrodynamics (MHD; also magneto-fluid dynamics or hydro­magnetics) is the study of the magnetic properties and behaviour of electrically conducting fluids. Examples of such magneto­fluids include plasmas, liquid metals, salt water, and electrolytes. The word "magneto­hydro­dynamics" is derived from magneto- meaning magnetic field, hydro- meaning water, and dynamics meaning movement. The field of MHD was initiated by Hannes Alfvén, for which he received the Nobel Prize in Physics in 1970. The fundamental concept behind MHD is that magnetic fields can induce currents in a moving conductive...
So it is possible
Time to use ML to predict my grades
Another question
6:08 AM
I feel something fishy about this video
We know that friction is caused due to the pits and falls in a surface right?
So if a metal gets heated like this
It would just expand right?
Friction isn't just due to roughness of the surface. In fact the brake disks on cars are very smooth.
I wrote an answer explaining how friction happens. Let me do a quick search and see if I can find it.
@JohnRennie oh then on what?
A: How is frictional force dependent on normal reaction?

John RennieYou need to start by considering the microscopic origin of the frictional force. In most circumstances surfaces are rough so when to touch two surfaces together they actually only make contact at the highest points on the surfaces. We call these high points asperities, and in the diagram below I...

Have a read through that.
So friction is caused due to that adhesive force
Roughness does also have an effect.
But in things like brake disks the surfaces slide over each other and smooth each other out so the disk surface ends up very smooth and adhesion is the main source of the friction.
6:20 AM
Oh I see
Okay thank you
And one more thing
I wonder how heat is produced?
@Akash.B In friction you mean?
When the surfaces slide over each other the contact points between the two surfaces are continually being torn apart, and when this happens the broken surfaces vibrate.
It's like snapping a rubber band - when the band snaps the two halves bounce back and waggle around.
The energy of that motion is absorbed into the material under the surface where it makes the molecules in the material vibrate.
And the vibration of molecules in a solid is exactly what heat is.
7:04 AM
would this help? @Akash.B
l.h.f.^ sir @JohnRennie :-)
7:18 AM
@skullpatrol Pal Tyson won the match
@JohnRennie Sir is it possible to study Tensors without Linear Algebra. I'm needing Tensors for Fluid Mechanics but it seems that for Tensor Analysis I have to complete Linear Algebra first. Can I do it without LA?
@Knight I don't know to be honest.
I use tensors but I don't have an in depth knowledge of tensor analysis.
But linear algebra is a very useful skill to have.
Sooner or later I will have to take LA. But can i understand Tensors if I know Vector Calculus @JohnRennie
yup, it was a victory for all of british boxing @Knight
@skullpatrol John sir must be very happy
I don't think he follows the sport
7:25 AM
@skullpatrol correct :-)
Yeah I too think so
Tyson must have grown up in Manchester during their soccer dynasty?
@Knight yes.
There's a difference between being able to use tensors and having an in depth understanding of them. You need tensor analysis for the latter but not for the former.
@JohnRennie What is latter here? Linear Algebra or Fluid Mechanics?
@skullpatrol When is your birthday?
7:36 AM
feb 29 <---joke
@Knight the former is being able to use tensors and the latter is having an in depth understanding of tensors.
@skullpatrol I'm only 15 :-)
@JohnRennie 15 X 4 = 60
@JohnRennie How can I learn to use Tensors? What Are prerequisites ?
@Knight I wouldn't try to learn about tensors. Learn about whatever it is that you're trying to learn and when you encounter a tensor try and figure out what the tensor does. Tensors are very simple beasts. They just convert a vector to another vector.
@JohnRennie 28 years of teenage hood?
7:40 AM
(strictly they convert a vector to a dual but unless you're learning GR you can ignore this complication)
@skullpatrol :-)
@Knight actually 59. I'm 60 next year.
@JohnRennie Okay, that’s a very nice advice
@JohnRennie When is your birthday?
I'm not telling in case anyone wants to commit identity fraud! :-)
@skullpatrol Pal do you really got your birthday on 29th ?
@Knight nah, I said "joke"
7 mins ago, by skullpatrol
feb 29 <---joke
Hahahahaha LOL
Donald Trump went to India and did a good amount of time-pass
7:47 AM
have you get your drivers license yet?
I got photo shoot yesterday for my learning driver license
@skull patrol ooo.
hi pal
What, s happening?
rewatching the fight
sooo much blood coming out of wilder's ear :(
7:52 AM
Pal do you got your original license or learning only?
Has time renewal come? How many years are left for renewing it?
@Knight what you think will he return?
@Knight my twitter is filled with it.
Return? I think he left for America
Trump is a master at manipulating Twitter.
7:55 AM
What I mean in president election.
Well he got lot lot of money so he can win, protest alone cannot defeat a corrupt man
The southern states love him.
Luckily yesterday I got some time to watch his press conference.
Very well handled the media.
Our prime minister have only one small house that, s it as a property.
24/7 for country service.
Am I in science room
Political science :-)
7:58 AM
Come on shoot me with lot of science facts
@Akash.B we talk about all sorts of stuff here, including occasionally physics :-)
@ACuriousMind well, we know that waves can generally be polarized so I was just wondering that the same concept is taken in qm or not
@Korra a wave can only be polarised if it's a vector or tensor wave.
Actually it’s not a Science room, it’s a bar you know a BAR
@Korra Scalar waves cannot be polarised.
7:59 AM
Okay, got it
Physics can, t run alone without political back presence right sir? @JohnRennie
@skullpatrol Do you like long hair or short?
Also, waves in qm generally denote probability of say position or momentum of a particle right?
@skullpatrol T-shirt or Shirt?
8:00 AM
@skullpatrol Jacket or Blazer?
@skullpatrol Jeans or formal?
@Knight tailor? Want to make a dress?
8:02 AM
Now I’m sure it was YOU who trained Cliff Booth. You you’re good
Pal did you take any money for teaching Brad Pitt about styling ?
Yeah you’re quite philanthropic ha?
someone has to be :-)
8:04 AM
@Knight sorry for kidding!
All I was thinking I can, t see any opposition that trouble trump on his way to white house again.
@YuvrajSingh... Nah! Why sorry? When skullpatrol is here we can be friendly, he is just awesome. We don’t have to bother about those users
@Knight can you predict the
Us president election with vote percentage.
nobody can, toooo many unknowns
No. I’m quite passive towards Politics. There so so many things going on in there and media never lets us know the truth
I predict Jeb Bush will win
8:12 AM
@skullpatrol We cannot call Slereah as Sam or Sammy, I’m just reminding you :-)
@Slereah very less, according to Fox TV!
You may call me Skeleton Lord
change your username to skeleton lord
Inspector Clouseau was French, someone asked him about the bomb blast that took place in his city, “Inspector What kind of bomb it was”, Clouseau replied calmly “the explosive kind”.
8:18 AM
Q: Anecdote of an astronomer looking for correlations in antipodal pairings of stars; what am I remembering?

uhohThe question Are the stars distributed in uniform distribution, on the celestial dome, with respect to brightness? brings to mind a different study that I vaguely remember hearing about a while ago, perhaps several decades. This is a summary of how I recall it, it may not be 100% accurate: An as...

Periodicity of Redshift Distribution in a T-3 Universe (FERMILAB-Pub-90/26-A January 1990)
@Knight why did they call the pink panther, "pink"?
> The first film in the series derives its name from the eponymous pink diamond that has an enormous size and value. The diamond is called the "Pink Panther" because the flaw at its center, when viewed closely, is said to resemble a leaping pink panther.
8:49 AM
@Korra the wavefunction encodes all the information about the particle. We get the observables like momentum by applying an operator to the wavefunction. The wavefunction itself is not observable.
sir @JohnRennie have you ever gone to the museum where they keep the Crown Jewels?
@skullpatrol no
Sir, can you recommend a good book on astronomy/astrophysics?
@Korra is there anything here?
Q: Book recommendations

David ZEvery once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. If you're looking for book recommendations, this is probably the place to start. All the question...

Also, I am bored and want to do some projects possibly am or astronomy based. Any ideas?
@JohnRennie I am an undergraduate, so I don't know which ones will be suitable for me
I meant qm not am...
9:46 AM
@skullpatrol Not even the Hoyle model in it
Very sad!
Weinberg has it I think
Is it possible that the reason human brains learn so fast is that they already have genetically embedded concepts of the ideas? For example, if you show a baby a car for the first time, it will really quickly build a mental image of it and can recognize it, while a neural network needs tons of data. Why is that?
How quickly?
I'm no babyologist, but I don't think a baby learns to recognize an elephant any faster than a neural network
Calling all animals a doggy is a classic underfitting error of the baby's neural network
I mean babies have usually a lot more to learn, so it's hard to compare directly
I heard Ian Goodfellow saying in an interview that one of the AI's problems right now is that they need a lot of data to learn, while a baby brain learns faster, something like that.
10:02 AM
the human brain is too complex to ask "why"
Please help, somebody help !
in Problem Solving Strategies, 2 hours ago, by Knight
@JohnRennie Sir I’m learning Green’s Theorem. My book writes $$ \mathbf A = U \nabla V - V \nabla U $$ and , consequently, for $A_n$ $$ A_n = U \frac{\partial V}{\partial n} - V \frac{\partial U}{\partial n}$$
I'm unable to understand how he got that fornula for A_n
Human brain has a bunch of benefits
much larger number of neurons, for a start
also they all run in parallel
neurons themselves are thought to do some extra internal calculations, IIRC
and a really long learning time
it has its downsides, though, of course
"It turns out that humans use a wealth of background knowledge whenever we take on a new game. And this makes the games significantly easier to play. But faced with games that make no use of this knowledge, humans flounder, whereas machines plod along in exactly the same way."
The whole exectuive function system of the brain makes it hard to train it
if you place a baby in front of a set of stock market data, he will learn very little of it
10:08 AM
Slereah please look on to my question once you get free
I will never be free
I am shackled in a prison of my own making
born free?
If I had to guess, I'd say that AI learns no faster or slower than a human baby but the human baby has prior experience and connections from which to build new stuff...
I used to be free but then I went to school.
@skullpatrol His paisano said that Everyone is born free and but now everyone is in chains.
The baby brain is also somewhat better structured than a random neural network
due to evolution and whatnot
10:10 AM
@Slereah So, please have a look on it now.
@Slereah simply put, it's too complicated to say anything for now
I would learn more but ethics boards are very stringent on the topic of experimenting on babies
@Slereah the ethics board is just a reflection of evolution's attempt to keep us f*cking.
will baby monkeys work?
Somewhat, but there are more human babies than monkey babies
This is a list of primate species by estimated global population. This list is not comprehensive, as not all primates have had their numbers quantified. == See also == Lists of organisms by population Lists of mammals by population The World's 25 Most Endangered Primates == References... ==
just look at the numbers
Humans #1 by a huge margin
10:13 AM
The ethics board is fine with monkeys, rats... animals... but with humans - damn no. I suppose that's because you can't reproduce with other animals.
Larger than all of them combined
Gorillas 🦍 are cute
China learned how to clone baby monkeys.
I bet they've laser-printed "Made in China" on the monkey's foot.
10:16 AM
Skull 💀 do you feel ghost around you?
do you?
I say it's the most exciting time to be alive! It seems that everything is getting "exploited". Genes, intelligence... who knows what's next...
Yeah! They scare me
have no fear, skullpatrol is here
They cry in their echoing voice “Skull patrol, skill patrol”
10:21 AM
let them cry
you don't have to listen
What are your opinions about what the future of AI will be? Do you think robots will eat us, make batteries out of us or maybe we'll live in harmony? Or maybe we'll transcend to a higher state of existence?
The robots will be like us in many ways
Working tedious jobs in offices
Doing data processing
@skullpatrol They haunt me 👻
haunt them back!
10:33 AM
How? Should I tell them that I know you and you can do anything to them without any discrimination?
All right! I will them
I gotta go pals, cya later.
@skullpatrol Pal whether you believe it or not but today you were a little different I found you different today. I don’t know, it may be with me or who knows!
2 hours later…
12:52 PM
@Korra try “The physical universe” by Frank Shu.
1 hour later…
2:16 PM
Q: Instead of just down-voting a new post, can't the same person care to explain why?

Firebolt I have a question about my Physics Stack Exchange post: How to exactly evaluate the Magnetic Field associated with the given Electric Field in a lossy medium? My question here is that instead of just down-voting my question that i just posted, shouldn't the same person explain why, especiall...

1 hour later…
3:29 PM
man why is $\xi$ such a popular variable in physics
like at least use the capitalized version
@SirCumference I've always assumed it's because someone has a twisted fetish with watching me struggle to write the symbol properly without it just turning into random curls that look nothing like it.
3:58 PM
@SirCumference From studies so far I have found German Physicist used it so much in their literature.
@SirCumference Is that a sandwich in your profile pic?
4:25 PM
I can draw a ξ
Thanks to many years of university
The evil people have different variables as the same letters in different scripts though
After many years as a colloid scientist studying zeta potentials I can still not reliably remember the difference between zeta and xi, nor draw either one of them. My life has been a failure.
@Knight It's a pie
I use many ξ
Because it is part of the spinor symbol family
ξ, ζ, ψ
Hopefully I never have to do anything involving 4 spinors
4:41 PM
Slereah I think French and German languages are not much different from Greek and Latin and therefore those writers use these symbols very much. When we the original works of Fourier it becomes extremely hard to whether he has made some symbols or some insect has died and got printed.
@Knight did you see the YouTube link that I send you? It concerns Ron Maimon.
Let me check my Facebook
He sings well.
If he was around 24 in 2007 then he must be around 40 years old now!!!!
Yes indeed.
But I must say my expectations about you were not wrong. You are a champion of informations on internet
4:46 PM
Is it asking you too for VPN app?
Why it asked me?
I think you’re VIP :)
Have you checked again?
I’m downloading that VPN
No you shouldn't download random apps.
4:50 PM
I wonder if that's the same Ron Maimon who used to be on this site.
@JohnRennie Yes he is the one that the podcast is about.
What injury and death was he talking about?
@SirCumference Same
@Knight I didn't listen to the whole podcast.
Listening to his podcast now.
5:18 PM
@JohnRennie The xi is the squigglier one ;)
@JohnRennie I don't know if I've ever considered much difference between those two symbols. I can't think of many contexts where I had to use xi and zeta at the same time. I think my brain just internalized them both as "hard to draw scribbles".
@Knight French as a Romance language is much closer to Latin and Greek than German is, but language relationship does not explain why one would tend to use Greek letters (the Romans certainly didn't think they had to use Greek letters!). The explanation is more likely that most early European scientists had a "classical" education that involved Greek, so when they needed symbols, they turned to what they already knew.
@ACuriousMind Yes, English always considered themselves to be different from all Europe and therefore they adopted English alphabets for variables while the rest of Europe went for Latin and Greeks.
@Knight have you listened to the podcast?
...the English alphabet is the Latin one!
(unless you mean old English runes but I don't think anyone uses that for variables :P)
5:28 PM
Let's use Chinese symbols!
@JohanLiebert Not full.
$ᚦ = ᚱ \cdot ᚾ$
@JohnRennie I’m happy that Wikipedia said it clearly that it was a Islamic terrorism.
ACM do you make your dinner or do you eat in some restaurant?
I think you have come back from Office
That podcast was too political to listen. I quitted it at 20:00.
@Knight is there any other form of terrorism? 😂
@Knight Is there anything I can do to help end some of the annoyance you have had with me recently?
5:32 PM
@JohanLiebert Yeah you’re very very clever here
@AaronStevens I want to ask with all due respect (you’re my elder) how it was not clear to you ?
@JohanLiebert Certainly there is. Please refrain from comments that might appear to slander religious or ethnic groups.
@Knight How was what not clear?
@JohanLiebert the guy who just killed nine people in Germany, then his mother (then himself) wasn't Islamic.
@AaronStevens You said in your comment that intolerance is due to being off-topic not something inborn, my argument is in my first paragraph I made it clear enough that Homework problems are off-topic and then in next para I said some people have intolerance with it, isn’t it natural to assume that intolerance is there because it is being off topic?
@JohnRennie What? When?
@Knight Ok, that is fine and you can address that to me. I am asking if there is anything I can do to help with the annoyance you have had with me lately. I am fine with having a discussion, but you seemed quite annoyed about it. I just want to know what I can do to help.
5:37 PM
See here or Google for many such articles.
@JohnRennie @ACuriousMind Sorry. I was just trying to say how in recent time the term terrorism has become synonyms to Islamic terrorism.
@AaronStevens No, I’m not annoyed with you. We just come to same platform for a few hours and even in that if I were to hold some grudge against you then I think I’m not a good social man. You got any problems with me? If my words have hurt you ever I publicly apologise you for that
@Knight I do not have problems with you. I am just confused as to why you were resorting to essentially telling me to not comment on your post.
@Knight your comment there did seemed like you were annoyed by Aaron's comment.
@AaronStevens :) I was annoyed because yesterday @JMac kept on saying us Americans “weird” and I thought you are his good friend and you know ...
5:43 PM
@Knight I was not part of that conversation, and I don't know what you are talking about. Yes JMac and I tend to get along here, but that doesn't mean I know everything he has said, nor does it mean I agree with everything he says or that I think exactly like he does
So I don't think it is fair to base your reactions to me on how you view JMac or interactions you have with him
@AaronStevens Yeah, I shouldn’t judge you by the acts that he did. But you know you people are very powerful, your duo is nice and after all ACM is with you. So, sometimes I become quite aggressive but ... um... let’s go on as we have
@Knight I try not to use any power I may have extensively here. Especially by just commenting on your post for something I thought was unclear. The point of writing posts is for other people. So if a point is not clear to others but clear to you, then telling others they should see the point you are making isn't going to help your post be taken correctly by others
Does this make sense?
Is he/she angry?
@JohanLiebert I would think so. I would imagine wombs are comfortable for babies :)
5:52 PM
@AaronStevens Aaron problem is that when we discuss something your friend and other people come and starts taking your side and then it feels like trolling. You see you post it many times “I agree with JMac” don’t you think posting that is a little not nice
@JohanLiebert He is neither, Quantum Mechanics!
@Knight Stating my agreement with someone is not trolling. Multiple people not agreeing with you is also not trolling. And that didn't even happen in this case
@AaronStevens yeah. She was in mid way drinking the amniotic fluid when the doctors pulled her out. 😂
People can disagree on things and still have perfectly normal discussions
@AaronStevens Ah! I’m not saying that, I’m saying it feels like trolling when you write “I’m with JMac”, why you need to write it you can just upvote his comment and “1” will make it clear that one more person share that view
I am completely lost what any hypothetical agreements with JMac have to do with Aaron's comment on your post.
5:56 PM
@Knight Usually I supplement comments like that with some supplementary information, my own additional thoughts, etc. I do only up vote comments if I think they have said all that needs to be said.
@ACuriousMind Actually I’m talking about Aaron’s friendship with JMac that has always proved lethat to me :)
That really doesn't make things any clearer to me.
@AaronStevens Do you think that writing “I’m with JMac” makes that supplement more powerful? I’m saying it in healthy tone.
@Knight Ok, to help keep the peace from now on I will just state my opinion without stating who I am specifically agreeing with
@ACuriousMind Actually, I came here in month of November 2019 and I and Aaron were discussing something friendly then JMac came and started saying to me “you’re not clear” , “you’re not clear”
@AaronStevens Thank you so much. 😊
6:01 PM
I am the nameless monster. Give praise unto me.
@Knight I don't think it is fair to then get upset with me for that, or to get upset for me agreeing with someone you do not like.
It was Aaron only who told me that downvotes in Meta means something else than what it means on parent site.
I shall always be grateful to him for things like that.
@AaronStevens I have deleted my comment from there. And I shall not do something like that.
@Knight I am fine with having a discussion about your post. If you think you have sufficiently addressed the point I bring up in my comment that is fine. You can let me know that. If I then agree, then that is it. If not, then I can help suggest ways to make the post clearer. Then we both win.
@AaronStevens yes. Did I satisfy you with my clarification of that?
@ACuriousMind My comments from that Meta post were deleted, I posted something about John sir and G.Smith sir. Can you please tell me why they got deleted? As knowing it would help me in not doing those things again.
Look at me, look at me. The monster inside me has grown this large.
Munch-munch, chomp-chomp, gobble-gobble, gulp.
6:09 PM
@JohanLiebert Are you in your knighty?
@Knight They did not add information related to the topic of the post, nor were they aimed at criticizing or improving it. Additionally, naming specific users that might help another user is not something we do here - if someone wants to volunteer to help someone, let them do it on their own.
Hello people!
@ACuriousMind Okay, shouldn’t I do that for new contributors? Is taking the names of specific users makes a burden on them to help the OP even he doesn’t? Am I right
At last he had found a name, but there was no longer anyone to call him by it. Such a shame,.... because Johan was such a wonderful name.
@Knight yeah it's midnight over here.
What’s your real name?
6:18 PM
Go to FB.
@Knight Yes, naming specific users might create an expectation on the part of the OP. And the users you name have never agreed to that, so don't do that. (Additionally, this doesn't scale well - just imagine one user being inundated with dozens of request for help of the "this other user said you'd help me" kind)
@ACuriousMind Thank you for educating me:-)
6:39 PM
@Knight FYI, that's a pretty poor paraphrase of the conversation we had yesterday. I was talking about US politics and elections being weird. That is not the same as calling Americans weird. I was born and raised in suburban Canada. Culturally, Americans aren't weird to me; we have a lot in common. Just their election process and the results of it seem pretty weird, even on a global scale.
00:00 - 19:0019:00 - 00:00

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