« first day (2694 days earlier)      last day (2238 days later) » 
00:00 - 13:0013:00 - 16:0016:00 - 18:0018:00 - 21:0021:00 - 23:0023:00 - 00:00

Prathyush Poduval
Prathyush Poduval
6:00 PM
Damn, it's tough mugging up the messier objects
 
Master Yushi
Master Yushi
@Tanuj My answer maybe wrong because i didn't think about it much but they do lie on the same unit circle, I checked
 
Prathyush Poduval
Prathyush Poduval
my brain's just this much away from exploding
 
Tanuj
Tanuj
@MasterYushi how
@PrathyushPoduval "this" is relative
 
Master Yushi
Master Yushi
parametric point (cosa,sina) for the unit circle
 
Prathyush Poduval
Prathyush Poduval
@Tanuj the subtelties of life are meant to be ignored
 
Tanuj
Tanuj
6:03 PM
@PrathyushPoduval not in here , or.. It's the h bar !
 
Master Yushi
Master Yushi
https://www.desmos.com/calculator/kc14buzy9s
See this graph, for $\theta=pi/4$ and $\alpha=pi/8$
 
John Duffield
John Duffield
@Mockingbird360 : I know what energy is. And mass.
 
Tanuj
Tanuj
@MasterYushi You're giving JEE this year too ?
 
Master Yushi
Master Yushi
@Tanuj yeah
 
Tanuj
Tanuj
cool
Guys check this out
 
John Duffield
John Duffield
6:14 PM
@Mockingbird360 : mass is resistance to change-in-motion. And "the mass of a body "is a measure of its energy content". A body contains energy. A radiating body loses mass. Energy is something real. Matter is made of it. A photon doesn't have energy, it is energy. See Einstein's E=mc² paper.
 
Prathyush Poduval
Prathyush Poduval
@Tanuj a bit of geometry lad
 
Tanuj
Tanuj
@PrathyushPoduval yea I know its circles :p
 
Prathyush Poduval
Prathyush Poduval
yeah, you don't need to do any coordinate geometery
the case given here is a very simple one
 
Tanuj
Tanuj
@PrathyushPoduval that's fine , but I wanna know how to do it with calculus , to solve similar kind of common tangent and common normal problems
 
Prathyush Poduval
Prathyush Poduval
that's bruteforce stuff which i haven't bothered to learn lol
 
Anonymous
6:18 PM
@JohnDuffield That's beating about the bush without actually axiomatizing the definition of energy. Also, the concept of relativistic mass is outdated.
 
Anonymous
Defining energy in terms of mass, doesn't make it clear at all
 
Tanuj
Tanuj
1 min ago, by Tanuj
@PrathyushPoduval that's fine , but I wanna know how to do it with calculus , to solve similar kind of common tangent and common normal problems
@Blue can you give some idea ?
 
Rick
Rick
Is it okay to apply Kirchhoff's voltage law if my circuit has inductors? ..like in a RL circuit? Can I consider the inductor to be like a battery with a polarity trying to oppose the changing current already flowing through it with a emf magnitude of Ldi/dt ? All my books do this.. I remember watching a lecture from Walter Lewin where he says we can't apply KVL if we have a time-varying magnetic field since it's non-conservative :/
 
Prathyush Poduval
Prathyush Poduval
@Tanuj Thinking about it, you can actually solve it using geometry I think for any arbitary cases
 
Tanuj
Tanuj
@Rick any ideas on how to do those common tangent and common normal questions ?
 
Anonymous
6:23 PM
@JohnRennie It seems GitHub can now render Jupyter notebooks without any external plug-ins. So I can share that link directly!
 
Anonymous
Also this seems a good website: nbviewer.jupyter.org
 
Master Yushi
Master Yushi
@Tanuj answer is A?
 
Tanuj
Tanuj
@MasterYushi yea , how did you do it ?
 
Master Yushi
Master Yushi
@Tanuj some basic coordinate, I'll drop a pic, wait
 
Tanuj
Tanuj
ok
 
Master Yushi
Master Yushi
6:29 PM
 
Anonymous
@Tanuj It is possible, but it's been long since I did such a problem. Tangent to a curve has slope $dy/dx$, while Normal has slope $-dx/dy$. So basically you use that.
 
Anonymous
Why not ask on Math SE?
 
vzn
vzn
@Mockingbird360 the motion is of space itself
 
no_choice99
no_choice99
6:53 PM
@Blue instead of relativistic mass, what do we use now?
i've been taught the old way apparently
i've been taught that rest mass is m_0 and that mass is gamma m_0
is that outdated?
 
Anonymous
Just rest mass. And when/if you need $E^2=(pc)^2+(mc^2)^2$, where $m$ is rest mass.
 
Anonymous
That's pretty much the modern standard
 
no_choice99
no_choice99
wait so the only difference is that now gamma m_0 has no name?
 
Anonymous
34
Q: Why is there a controversy on whether mass increases with speed?

User 17670Some people say that mass increases with speed, some people say that the mass of an object is independent of its speed. I understand how some (though not many) things in physics are a matter of interpretation based on one's definitions. But I can't get my head around how both can be 'true' is an...

special-relativity mass speed mass-energy
 
David Z
David Z
@no_choice99 Pretty much. Sometimes you'll still hear people say "relativistic mass" which does refer to $\gamma m$ (with $m$ being what you know as $m_0$, i.e. the "mass" or "rest mass"), but usually they just say "energy" which refers to $\gamma m c^2$
 
no_choice99
no_choice99
7:03 PM
i see. man that's confusing
 
Anonymous
It just reduces confusion.
 
no_choice99
no_choice99
what i find confusing is keeping track of what's modern and what's the old way
if only i was taught the right modern way right away, i wouldn't find that confusing
 
Anonymous
Anyway, you wanted an axiomatic definition of energy?
 
no_choice99
no_choice99
who, me? no
 
Anonymous
36
Q: What's the real fundamental definition of energy?

user1620696Some physical quantities like position, velocity, momentum and force, have precise definition even on basic textbooks, however energy is a little confusing for me. My point here is: using our intuition we know what momentum should be and also we know that defining it as $p = mv$ is a good definit...

classical-mechanics energy
 
Anonymous
7:07 PM
@no_choice99 Ah, okay
 
no_choice99
no_choice99
i see a new quantum computing stack exchange website
what's that? qubit things? where does one learn about qubits? I haven't dealt with them in undergrad QM
 
Anonymous
Quantum Computing is a separate subject. It isn't taught at the undergrad level, at most places.
 
no_choice99
no_choice99
i see
 
David Z
David Z
@no_choice99 Yeah, that's always a necessary step when conventions change - you take on more confusion in the short term to reduce it in the long term.
 
no_choice99
no_choice99
I agree David Z. i'd usually favor changes
 
Captain Bohemian
Captain Bohemian
7:16 PM
does graduate school QM teach quibits? No in my alma mater. I learnt it in a research assistant position.
 
Anonymous
@CaptainBohemian QC is not QM :P
 
Captain Bohemian
Captain Bohemian
@Blue I know that, but @no_choice99 said " I haven't dealt with them in undergrad QM".
 
Anonymous
@CaptainBohemian Okay, but I don't get your point.
 
Anonymous
Was that "does graduate school QM teach quibits?" a rhetorical question?
 
Captain Bohemian
Captain Bohemian
I assume no_choice99 considers qubits would be taught in QM in graduate level because (s)he hasn't been taught about qubits in QM in undergraduate level, but I don't think that's the case.
 
no_choice99
no_choice99
7:22 PM
yeah i assumed that
 
Anonymous
As I already said, it is a separate subject
 
Captain Bohemian
Captain Bohemian
I only like some topics in quantum information and quantum computation. Some topics in this subject are very odd (in the sense of being paranormal) in that they are not like the usual topics physics department teaches.
 
no_choice99
no_choice99
uh what.. paranormal??
can you give an example?
is it what john preskill studies
 
ACuriousMind
ACuriousMind
Hey @JaimeGallego :)
How's it going?
 
Jaime Gallego
Jaime Gallego
Howdy
About to begin Easter holidays
Mostly doing some R&R before getting back to other projects
 
Anonymous
7:32 PM
R&R?
 
no_choice99
no_choice99
reading and research i guess
 
Jaime Gallego
Jaime Gallego
"Rest and recuperation"
R&R (military)
R&R, military slang for rest and recuperation, is a term used for the free time of a soldier or international UN staff serving in unaccompanied (no family) duty stations. The term is used by a number of militaries such as the United States Armed Forces and British Armed Forces. The US Morale, Welfare and Recreation network provides leisure services for US military personnel. In the UK, the term applies to a type of leave granted to personnel during an overseas deployment which allows them to return home to the UK to visit their family. Service members and US Defense Department civilians on 12-month...
 
ACuriousMind
ACuriousMind
Ah, nice :)
 
Captain Bohemian
Captain Bohemian
@no_choice99 I can't recall those topics quickly now because they are too odd (paranormal) to understand for me. I usually have difficulties remembering for long things I can't learn well.
But if someone mentions those topics to me, I may have impression.
 
no_choice99
no_choice99
ok
im not convinced of the weird (in the paranormal sense) stuff in QC
coz i didn't see such thing in QM
 
ACuriousMind
ACuriousMind
7:35 PM
@CaptainBohemian "paranormal" usually means things like ghosts (not Fadeev-Popov ghosts, but ghosts in the colloquial sense). You're likely looking for a different word
 
no_choice99
no_choice99
i doubt it's different, but hey, i know nothing about qc
 
Anonymous
How does physics explain ghosts? Hmm. Never wondered about that
 
Anonymous
QM is usually a good place for cranks to start from :P
 
ACuriousMind
ACuriousMind
@Blue They're a crucial ingredient for the quantization of gauge theories ;)
 
Captain Bohemian
Captain Bohemian
@ACuriousMind I do have the feeling those topics are as increditable/inexplicable as paranormality. I can't think of other words to describe my feeling now.
 
Anonymous
7:39 PM
@CaptainBohemian Example?
 
no_choice99
no_choice99
already asked for an example
 
ACuriousMind
ACuriousMind
@CaptainBohemian Since something paranormal is by definition not explicable by science, I still have my doubt about your choice of words ;)
@JaimeGallego Ah, "Easter holidays". All I get now is a Friday and a Monday off ;)
@Qmechanic I'm not sure that will do anything - if I enter a synonym, it's only replaced after I have entered the tag. People who won't read the tag description to figure out whether the tag is right for their question probably also won't be fazed by kinetic-theory being magically replaced by statistical-mechanics after posting.
 
Qmechanic
Qmechanic
@ACuriousMind : It is more likely to be corrected, either by OP or others.
 
Captain Bohemian
Captain Bohemian
@no_choice99 ok, now I think of an example, something like teleportation. @blue
 
no_choice99
no_choice99
i wish i had studied that ^^
 
Anonymous
7:47 PM
@CaptainBohemian That's far from "paranormal".
 
Anonymous
Very much explainable
 
no_choice99
no_choice99
@Blue did you study QC?
 
Anonymous
Unless you are referring to some Michio Kaku level pop-sci stuff
 
Anonymous
@no_choice99 I am
 
ACuriousMind
ACuriousMind
Obligatory xkcd on quantum teleportation
 
Anonymous
7:50 PM
@ACuriousMind This is why I love xkcd
 
Anonymous
There's always something relevant :D
 
Captain Bohemian
Captain Bohemian
@Blue maybe it's very much explainable to you, but I feel the way of the explanation is unusual to me, not completely understood by me.
 
Anonymous
@CaptainBohemian Let's put the cards on the table. What's the usual way of explanation you're referring to ?
 
John Duffield
John Duffield
@Blue : relativistic mass aka E=mc² is not wrong, and nor is it outdated.
 
Anonymous
@JohnDuffield It's not wrong, but it's outdated. Also, you're dodging the point that that does not give any axiomatic definition of energy.
 
Anonymous
7:53 PM
You can't just say "energy is relativistic mass" and get away with it
 
Anonymous
And when asked to define mass, you invoke energy
 
John Duffield
John Duffield
@Blue : I didn't give much of a definition of energy. Nor did I say energy is relativistic mass. I said mass is resistance to change-in-motion. That's what it is. It's a lot easier to get a skateboard moving than a truck.
Do you doubt me Blue?
 
ACuriousMind
ACuriousMind
@Blue Between xkcd, smbc and the newly-revived Abstruse Goose, there's a comic for everything
 
Anonymous
Inertial mass is a measure of resistance to acceleration. Okay, that's a very middle school level definition and I like it. If so, I don't understand why you even needed to mention $E=mc^2$, there. Is it like compulsory for you to invoke Einstein's work at every possible instance, even where it is not relevant?
 
Jaime Gallego
Jaime Gallego
In some cases it may be more intuitive to lump everything together into a single inertia. But I agree that it is outdated.
I mean
"The photon does not have mass until it does" sounds backward.
 
John Duffield
John Duffield
7:59 PM
@Blue : it's because when you trap a massless photon in the mirror-box, the mass of the system is increased. The box is harder to move because the photon is in there. Then when you open the box, the mass is reduced. Like Einstein said: "If a body gives off the energy L in the form of radiation, its mass diminishes".
 
ACuriousMind
ACuriousMind
@JaimeGallego It's a tautology, not backwards ;) (But be aware there's no such thing as a photon with mass in standard physics, this is prohibited by gauge invariance)
 
Jaime Gallego
Jaime Gallego
@ACuriousMind Indeed, that is why I commented on it being outdated
 
Anonymous
@JohnDuffield You're again confusing between relativistic mass, energy and rest mass.
 
Jaime Gallego
Jaime Gallego
Use momentum instead
 
Anonymous
"when you trap a massless photon in the mirror-box, the mass of the system is increased"
 
Anonymous
8:00 PM
That statement clearly shows the confusion
 
Anonymous
@ACuriousMind I haven't seen much Abstruse Goose comics. But yeah, smbc is cool too!
 
ACuriousMind
ACuriousMind
 
John Duffield
John Duffield
@Blue : I'm not confusing these things. That's what happens. As per Einstein's E=mc² paper, "radiation conveys inertia between the emitting and absorbing bodies". If you open mirrorbox1 to let the photon out, its mass reduces, then when you catch the photon in mirrorbox2 its mass increases. The box is harder to move when the photon is in there.
 
Anonymous
"The box is harder to move because the photon is in there. " Gosh, you speak as if someone has actually performed that experiment. That's so much nonsense in one sentence.
 
Anonymous
@JohnDuffield "radiation conveys inertia between the emitting and absorbing bodies". That part is true.
 
John Duffield
John Duffield
8:04 PM
@Blue : it's true. "If a body gives off the energy L in the form of radiation, its mass diminishes" This is basic stuff. Why do I have to teach you this? Are you still at school?
 
Anonymous
@JohnDuffield The quoted statement is true. But that does not say anything about why a box will be harder to move if there is a photon inside.
 
Anonymous
I'll probably give this a rest. It's not worth the effort.
 
John Duffield
John Duffield
@JaimeGallego : photon momentum is a measure of resistance to change-of-motion for a wave moving linearly at c, but you cannot decelerate it like you can decelerate an electron. However you can decelerate it in the vector sense, as per Compton scattering.
@Blue : it's because the photon is not moving in aggregate with respect to you. See arxiv.org/abs/1508.06478 by van der Mark and (not the Nobel) 't Hooft.
 
Sir Cumference
Sir Cumference
"Light does not have momentum because it does not have mass" ~my old high school physics textbook
 
Anonymous
@SirCumference Really? :P
 
John Duffield
John Duffield
8:12 PM
@Blue : what you mean is that you don't know about Einstein's E=mc² paper. Yes, you'd better give it a rest.
 
nitsua60
nitsua60
(@Blue don't let JD taunt you--that was a reasonable decision to disengage you made a moment ago)
 
John Duffield
John Duffield
@SirCumference : light has momentum, and it has inertial mass. That's why it conveys inertia between the emitting and the absorbing bodies.
 
Sir Cumference
Sir Cumference
@JohnDuffield Yes, I know. My old textbook did not know.
 
John Duffield
John Duffield
@SirCumference : good stuff. Perhaps that's the book Blue's been reading.
 
nitsua60
nitsua60
@JohnDuffield Stop it. Be Nice applies everywhere on site, including chat.
2
 
0celo7
0celo7
8:15 PM
@ACuriousMind There's just an error in the proof. I found a correct one.
 
Sir Cumference
Sir Cumference
Holy hell, what's wrong with the chat today
 
0celo7
0celo7
@ACuriousMind How do you feel about the typesetting on the last equation here? i.gyazo.com/40c24f44bed464521b662ec997c842fa.png
 
John Duffield
John Duffield
@nitsua60 : I try. However when people say Einstein was wrong on a physics website it's sometimes tempting to be a little bit forceful.
 
Sir Cumference
Sir Cumference
@JohnDuffield Dude, get over yourself and Einstein.
 
ACuriousMind
ACuriousMind
@0celo7 I'm not sure it's the typesetting that's the problem there ;P
 
nitsua60
nitsua60
8:17 PM
@JohnDuffield It's fine to be forceful--just do it Nicely.
 
0celo7
0celo7
@ACuriousMind ?
 
ACuriousMind
ACuriousMind
@0celo7 I mean there's probably not a prettier way to typeset that equation, but the equation is ugly :P
 
0celo7
0celo7
@ACuriousMind it's my equation :(
I think it's pretty
 
ACuriousMind
ACuriousMind
@0celo7 You have to keep in mind my aesthetics are definitely not those of a geometric analyst
 
0celo7
0celo7
@ACuriousMind The end result is definitely very nice though.
Even you will enjoy it
 
nitsua60
nitsua60
8:20 PM
@SirCumference "get over yourself" isn't really a helpful way to put it to someone you think needs self-getting-over, methinks. Point to specific statements, make actionable requests, explain why. Assume Good Faith, even when it's hard. Especially when it's hard. Ask for help when you need it. Let "Someone On The Internet Is Wrong!" happen.
 
Balarka Sen
Balarka Sen
I think most people don't have the time and energy to argue with difficult people on the internet. The right move then, is not to blatantly tell them to stop - because that's not going to work. The right move is to put them on ignore.
7
Which I do all the time and am happy to do
 
0celo7
0celo7
@BalarkaSen whom do you have ignored
 
Balarka Sen
Balarka Sen
Not a good idea to publicly share that is it
 
0celo7
0celo7
am i on it
 
Balarka Sen
Balarka Sen
Clearly not!
 
ACuriousMind
ACuriousMind
8:23 PM
@0celo7 That's not a useful question in this context - the whole point is not to make a big drama out of it.
 
John Duffield
John Duffield
Anyway, a photon has no mass in the usual sense because you cannot speed it up or slow it down by pushing it. But when you trap it in the mirror-box, this massless photon increases the mass of that "body". Open the box to let the photon out and the mass of that body is reduced. This is why the the inertia of a body depends upon its energy-content.
 
Balarka Sen
Balarka Sen
I do like trolling difficult people occasionally, which is why I don't consistently maintain my rule stated above. But then it's your fault if you get aggravated if the opponent - the difficult person - trolls back
Also, that trolling better be controlled and civilized, otherwise it's just a violation of the guidelines
One has to be eclectic, as a wise man once said
 
John Duffield
John Duffield
It's also why the photon has a non-zero inertial mass. Inertial mass isn't rest mass, it's a measure of energy. The Wikipeida inertial mass doesn't make this clear.
 
ACuriousMind
ACuriousMind
Oh god I have to water other people's plants. Are there any good "Sorry I drowned your plants" cards?
 
nitsua60
nitsua60
@0celo7 I agree with ACM, but will add that if you're sincerely curious because of whatever reasons, that's the sort of thing that a side-room (around here you use Physics Meta for it?) can be really good for: a genuine conversation about a topic that's fine to discuss but, if simply inserted into the larger flow, would reasonably be expected to cause unnecessary conflict.
 
0celo7
0celo7
8:34 PM
I have a line for private communication with Mr. Sen.
 
nitsua60
nitsua60
That's fine. You may not know, but I write in chat with the same philosophy I write on mainsite(s): it's not just the person being addressed I suppose will read it. See also meta.stackexchange.com/q/244534/311001
 
John Duffield
John Duffield
Would anybody like to talk about the mass deficit? That's typically where gravity converts potential energy into kinetic energy, which ends up getting dissipated, typically in the form of radiation. You're then left with a mass deficit. The mass of the body is less than what it was. It's not a million miles away from "If a body gives off the energy L in the form of radiation, its mass diminishes".
 
nitsua60
nitsua60
@BalarkaSen That's a reasonable position, and (sadly) also one that leads collectively to a toxic environment. Tragedy of the Commons, and all =\
 
vzn
vzn
lol "civilized trolling" :P
 
Balarka Sen
Balarka Sen
It's the position that the mathematics chat has taken for years and years and years
and is still running up and well
 
nitsua60
nitsua60
8:39 PM
Alright people, I've got to run. My weekly punchspace D&D game calls. Be well!
 
ACuriousMind
ACuriousMind
@nitsua60 I'm only here because my biweekly Fate game fell through ;P Have fun!
 
Balarka Sen
Balarka Sen
See ya
 
ACuriousMind
ACuriousMind
@SirCumference ???
 
Sir Cumference
Sir Cumference
Dog walked over my keyboard
 
ACuriousMind
ACuriousMind
Dogs don't walk over keyboards, yours must think it's a cat
 
Sir Cumference
Sir Cumference
8:43 PM
You'd be surprised with how often she walks over mine
 
Anonymous
I've seen dogs sleeping peacefully over keyboards
 
Anonymous
Apparently the PC warmth attracts them
 
Anonymous
Although cats are the more entitled ones
 
John Duffield
John Duffield
Does anybody want to talk about energy then? There's something very special about Compton scattering:
 
Sir Cumference
Sir Cumference
@ACuriousMind What's your gravatar supposed to be?
 
John Duffield
John Duffield
8:46 PM
 
Sir Cumference
Sir Cumference
@JohnDuffield Please, stop interrupting with random physics. No one is talking about that.
 
ACuriousMind
ACuriousMind
@SirCumference Fell the Dabus.
 
John Duffield
John Duffield
@SirCumference : No one is talking about anything, so I'll leave a message for Mockingbird.
 
Sir Cumference
Sir Cumference
@JohnDuffield Then actually ping Mockingbird, instead of asking "does anybody want to talk about energy?" Right now you seem to be ranting to no one.
 
John Duffield
John Duffield
@Mockingbird360 : In Compton scattering some of the photon energy is converted into electron kinetic energy. If you were to perform another Compton scatter on the residual photon, and then repeat ad infinitum, you would have converted all of the photon energy into electron kinetic energy.
 
ACuriousMind
ACuriousMind
8:53 PM
Let's phrase this in a more general manner: When other people ask you to stop going on about a topic, you stop. See e.g. this for precedent.
 
vzn
vzn
wow, shog9 speaketh to Physics hadnt seen that one (+1) o_O
 
00:00 - 13:0013:00 - 16:0016:00 - 18:0018:00 - 21:0021:00 - 23:0023:00 - 00:00

« first day (2694 days earlier)      last day (2238 days later) »