The h Bar

John Duffield

20:03

@0celo7 : go and read up on it. Do your own research. Why do I have to spoon-feed you?

"These have only two possible spin angular momentum values measured along any axis, +ħ/2 or −ħ/2, a sheerly quantum mechanical phenomenon..."

0celo7

You had your chance to convince me.

You failed.

Danu

@JohnDuffield Your quote of Goudsmit is rendered moot by Goudsmit himself here. He describes, in a lecture from 1971 (by then quantum theory WAS well-understood), how he and his collaborators came to realize the electron is not actually physically spinning. And I quote:

> And that was it: the spin; thus is was discovered, in that manner. Of course we told Ehrenfest about it and then summer was over and I went again to Amsterdam and various episodes followed. Naturally, I found it wonderful, because in the formalism which I knew it fitted perfectly. And the rigorous physics behind it I did not fathom. But Uhlenbeck, being a good physicist, started to think about it. ...... "A charge that rotates"......? He claims that he then went to Lorentz and that Lorentz replied: "Yes, that is very difficult because it causes the self energy of the electron to be wrong".

0celo7

I'm deleting this question, this was a useless trip into quackland

Danu

The paragraph above it contains your (obvious) out-of-context misquote that you keep on using.

@0celo7 NO

I'm writing a thorough response to JD's answer in a series of comments

plz don't render my work moot :P

0celo7

just for you <3

John Duffield

20:05

@0celo7 : You're deleting it because you got a good answer that you can't fault.

0celo7

@JohnDuffield oh sure

Danu

I responded to the first 4 points in your answer @JohnDuffield

John Duffield

@Danu : Goudsmit did not say electron spin is not a real rotation or words to that effect.

0celo7

3 hours ago, by 0celo7

Danu is right, like always

Danu

@JohnDuffield You can have your own interpretation of his words if you like, but I think it's pretty clear what is going on here.

dmckee

20:10

@0celo7 And this is how you learn the reason for John R's recent meta post.

Danu

The quote shows that he was mostly very confused about what he was seeing in his experiments, and had very little of a clue what he was talking about at the time. In particular, the "real rotation" aspect immediately leads to big problems (as described in the quote).

@dmckee Hahaha

0celo7

wait I can't delete my own question?

Slereah

sorry @0celo7, this goes on your permanent record

dmckee

@0celo7 Not if it has an upvoted or accepted answer.

My mistake. John didn't post the question. But rather answered the one David Z. posted.

Kiss Off Violent Femmes

►

0celo7

hipster music detected

AngusTheMan

20:14

apologies for interrupting the conversation chaps, but would this SE be the place to ask about lab instruments, i.e reviews of workers? thanks :)

reviews by workers ^*

0celo7

sounds like engineering, you might get shot for that

dmckee

@0celo7 Hipster? Dude, I knew that song when punk was fresh.

AngusTheMan

hmm my fear haha

dmckee

I've seen those guys in concert. Dingy little venue on the waterfront in Norfolk, VA.

@AngusTheMan Treading pretty near the edge, of a "shopping question" I suspect.

Question about experimental technique are in, but "How do I pick a technical-thingy?" is out.

0celo7

@Danu what do you make of Timaeus' answer?

dmckee

20:17

Come to think of it, I think I saw them before @0celo7 was born.

Which I suppose makes it old-people music.

0celo7

yup

you're old

dmckee

The ironic part is that the song is about youth rebellion against arbitrary authority.

Danu

I wonder if anyone will read my chain of comments

It's rather in-depth

0celo7

there are more!

I read the first three

Danu

I won't make responses to points (9) and (10) because they're uninteresting and irrelevant

0celo7

20:21

why is 9. uninteresting

Danu

Picture for posterity; I suspect the question will get deleted at some point.

0celo7

ha

Danu

Because string theory has nothing to do with the rest of the questions, per se.

dmckee

@Danu I hate to tell you this, but I see long string of comments like that as something that needs deleting. Put it in an answer or something. Please.

Danu

@dmckee That'd be going directly against one of the answer-deletion rules: Do not post comments on other answers as an answer.

0celo7

20:22

haha Danu can report himself and get another flag point

dmckee

@Danu Well, I meant write an answer that address the question and covers that ground along the way.

Danu

I'm open for alternative suggestions, but I can't, right now, think of something better than this.

@dmckee I'm only interested in specifically addressing the points made in JD's answer.

I'm not interested in answering the question myself

dmckee

Well, sooner or later someone looking for their marshal badge (say) is likely to flag those comments. Unless, as you suggest, the quetion is nuke wholesale first.

0celo7

I won't nuke it until ACM has returned

I know he wanted to see what would happen

Danu

@JohnDuffield The final sentence of your last comment is reasonably accurate: I am ranting about your blatant misrepresentation of well-known facts and spreading of misinformation in a way that seems authoritative to unsuspecting laymen. Your answer is, on all points, either (1) avoiding the question (2) an irrelevant side remark tangentially related to the question (3) demonstrably wrong (4) wild assertions without any serious back-up (5) appeals to authority

@Danu : guess what? Photons interact with photons. There are no electrons and positrons popping into existence like magic. Have you got that? — John Duffield 1 min ago

0celo7

20:31

but that's wrong

Danu

Hey, finally something to concretely pin you down on :D

0celo7

there is no photon-photon vertex

Danu

Directly contradicting the QED Lagrangian :D

0celo7

directly contradicting gauge invariance

abelian gauge theories can't have self-interactions

Danu

And the best thing is that QED is the experimentally best established physical theory in existence, full stop.

I'm done for now :)

0celo7

20:33

@Danu gg

Danu

John Duffield

@Danu : it's not a problem if you know the answer. Magnetic moment says that rotation is real. So does Stern Gerlach. So does the electron's helical motion in a magnetic field. There is no magick.

0celo7

> There is no magick

This is true.

Danu

OR IS THERE? magic.wizards.com

0celo7

@Danu On a good gate we're movin on. - Ludacris

Danu

20:37

More screenshots in case of deletion

0celo7

I have a text copy of the OP.

John Duffield

@Danu : I am not misrepresenting facts or spreading misinformation. The misinformation is the cargo-cult nonsense that says a 511keV photon spends its life yo-yoing into a 511keV electron-positron pair that magically morph back into a single 511keV photon that nevertheless manages to keep on going at c. That's garbage. Got it? Now watch my lips: photons interact with photons.

Danu

@JohnDuffield Deeper and deeper :)

0celo7

I think I need some references to Einstein and the evidence here.

Danu

Side note, even classical (i.e. Maxwell) electrodynamics is linear and has no photon-photon interaction.

Every freshman who took E&M surely knows the superposition principle ;)

Hence, any claim of photon-photon interactions must be purely quantum and it is exactly there that it is most strongly debunked by experiments :)

John Duffield

20:43

@0celo7 : what you need is the the Breit-Wheeler process: "However, in 1997, researchers at the Stanford Linear Accelerator Centre were able to conduct the so-called multi-photon Breit–Wheeler process using electrons to first create high-energy photons, which then underwent multiple collisions to produce electrons and positrons, all within same chamber.[4]".

0celo7

I thought Wheeler dealt in cargo cult stuff

dmckee

@JohnDuffield For which QED provides cross-section and angular distribution predictions.

John Duffield

@Danu : LOL. "They would then direct the photon beam from the first stage of the experiment through the centre of the can, causing the photons from the two sources to collide and form electrons and positrons."

dmckee

Ones that work.

Come back when your hand-waving can say the same.

0celo7

@dmckee what kinds of diagrams contribute to that process?

John Duffield

20:52

@dmckee : I never said QED was wrong. I'm a Feynman fan. What I said is the notion that a single 511keV photon spontaneously morphs into an 511keV electron and a 511keV positron which then morph back into a 511keV photon which continues to propagate at c is cargo-cult nonsense. It is the the cause of that turbine hum you can hear, which is Feynman spinning in his grave.

0celo7

oh my god...that's Feynman in the ceiling!!?! I thought it was the AC!!

skill patrol

:D

Feynman and The Evidence

0celo7

EFE Inc. - Einstein, Feynman and The Evidence Incorporated

Danu

> photons interact with photons

> never said QED was wrong

ERROR ERROR

Slereah

Albert E. and the Evizzle

0celo7

20:58

I imagine a high, dunk French man saying that while stumbling through rows of GR books and papers

skill patrol

::makes fresh popcorn::

Danu

@skillpatrol I think we've already climaxed

yuggib

@Danu I was about to say the same...

T_T

John Duffield

@Danu : photons interact with photons. Get used to it. Stop thinking I haven't heard about it so it must be junk. It isn't junk. It's physics. And it's my pleasure to teach you some. Go and read anna's virtual-particle answer here: "Thus virtual particles exist only in the mathematics of the model".

yuggib

I lost the better part

Danu

21:00

@JohnDuffield Keep on digging that hole all you like :)

0celo7

@Danu The chapter on "anchoring" in T,F&S is incredible

Danu

@0celo7 Yeah, almost everything he talks aboutis very insightful

sometimes I wish he'd try to keep it slightly more technical but okay, a man's gotta make a living :P

dmckee

rationalwiki.org/wiki/Argument_from_incredulity Just as wrong in physics as in evolution.

0celo7

lol @ rationing makes people buy more

Danu

@JohnDuffield I directly addressed the point about virtual particles in my comment chain: I, too, agree that they're an oversimplification that should not be used to make any kind of ontological claim. Feynman diagrams are just calculational tools. This is totally unrelated to the rest of the discussion.

(hey, it's something we agree on lol)

Slereah

21:04

If you get rid of virtual particles, then please also do not speak of "photons"

Talk of the EM field

Danu

That takes it too far

particles are just fine

John Duffield

@Danu : The virtual particles are virtual. As in not real. They are mathematical abstractions. The virtual electron-positron pair that feature in what you think is the QED description of gamma-gamma pair production are not present. Two photons are present. They are the only particles present. They interact. The Breit-Wheeler process is an example of this. Have you got this yet?

Slereah

Sure, except WHEN THEY DO NOT EXIST

Like WHENEVER THERE IS INTERACTION

So all the time everywhere

Danu

> never said QED was wrong

Contradicting yourself again?

0celo7

@JohnDuffield Do you know what a Lagrangian is?

Danu

21:06

I'm going to stop responding to you for today, by the way.

Slereah

he does not, it has math in it

John Duffield

@Slereah : the photon is real. The virtual photon is virtual.

skill patrol

Want some fresh popcorn? @Slereah

Danu

You've made enough of a fool out of yourself for me to have lost motivation to try and correct you.

John Duffield

@0celo7 : yes, I know what a Lagrangian is. And you know that even if by some miracle I didn't, I'm smart enough to go find out. Duh!

Slereah

21:07

Ahahah

dmckee

I'm going to repeat myself just once: an alternate theory of particle physics has to make predictions of observables, by which I mean thresholds, cross-sections, angular distributions and spectra.

0celo7

@JohnDuffield Do you know what the Lagrangian of QED is? Please write it here.

dmckee

Without those it isn't even wrong yet.

That's what makes this business a science.

2

Slereah

why do you people e

still even try

John Duffield

@Danu : you're going to stop responding because I referred to the Breit-Wheeler process to demonstrate that photons interact with photons, after you said repeatedly that they don't. Oooh! How embarrassing!

0celo7

21:09

haha

@dmckee Can Breit-Wheeler happen spontaneously (in vacuo) or do the conditions need to be just right like pair production near a nucleus?

John Duffield

@0celo7 : yes I do, but why should I do anything for you any more? I spent more than an hour giving bona-fide references in response to your question, and you ignored the whole lot. You even ignored Timaeus's answer too. You're a timewaster.

DanielSank

Hey everybody!

skill patrol

Welcome @DanielSank

DanielSank

Oh....

0celo7

@JohnDuffield I'm trying to digest his answer.

@DanielSank hola hovito

DanielSank

21:12

@0celo7 hovito?

dmckee

@0celo7 It needs a high field. Near a nucleus works, but so does a high intensity laser environment.

0celo7

@DanielSank no clue, don't speak Spanish

DanielSank

@0celo7 wtf, you said "hovito".

@0celo7 Wow, @0celo7.

obe

Lol

John Duffield

@dmckee : and this high field. Would that be the electron field?

0celo7

21:14

@DanielSank well that's where I got it from

haha

good song, amirite @Danu

yuggib

@JohnDuffield Define what interaction is. There is a box on which you can't see inside, and a pen goes inside the box. Then a pencil comes out. What could you infer from that observation? It is not sure that a pen transformed into a pencil (pen-pencil interaction)....maybe the pen is still inside the box, and there was a pencil before that has then come out, and no interaction at all occurred.

DanielSank

@0celo7 google.com/…

skill patrol

@0celo7 so now you think you are Jay-Z

John Duffield

@0celo7 : bah, you ignored his answer. Now do excuse me, I'm off.

yuggib

The better you can say, is that you have observed a pen go in, and a pencil come out

In an experiment where you measure a photon going into the device, and then a photon coming out, you cannot infer anything on the nature of the interaction.

If you have a model of the interaction, you can make predictions and test those with the experimental observation.

skill patrol

21:17

I think he left.

obe

@0celo7 I didn't die.

yuggib

@JohnDuffield The QED, as @Danu intends it, gives you the predictions of an experiment where a photon goes in, and another goes out. However it does not admit a direct interaction between the two.

0celo7

lots of people don't die

welcome to the club

yuggib

@JohnDuffield The theory may as well be false, but it makes precise predictions. Would you be able to provide a theory with photon-photon interaction that makes prediction that agree with experiments? We don't need to know the experiments, but we are curious about "your" theory explaining them. If you are not able to provide a satisfactory one, at least do not make jokes of those who tell you there is one.

John Duffield

@yuggib : huh? What's all that about pens and pencils? Two photons interact and turn into a positron and an electron, which we can diffract, and which has a magnetic moment, and which in an atomic orbital exists as a standing wave described by spherical harmonics. What do you think happened in that pair production? Magick?

skill patrol

21:22

22 mins ago, by skill patrol

::makes fresh popcorn::

yuggib

@JohnDuffield It was a rhetorical figure

0celo7

@skillpatrol I should run down to the store and get some

John Duffield

@yuggib : QED isn't false. The falsehood is the cargo-cult crap that's crept in. The virtual electron and positron that feature in two-photon physics are virtual. They aren't real. They only exist in the maths. The particles that exist are the two photons. They interact "through higher order processes" because the front of a photon is somewhat like a partial positron, and the back is somewhat like a partial electron.

It's like what dmckee was saying. High field.

0celo7

huh, seems my question got closed

We should talk about Timaeus' answer

I'm not sure what exactly he's trying to say

dmckee

@JohnDuffield Don't suggest that I agree with you. You are not even wrong about this.

Come back when you have predictions.

4

John Duffield

21:27

@dmckee : I'm right about this. Those virtual particles are virtual.

dmckee

Predictions, John. Predictions.

0celo7

How can he have predictions when he refuses two write any equations on principle?

John Duffield

@0celo7 : I don't refuse on principle. I write equations down. But you still don't understand that mathematics is not evidence.

dmckee

No, writing predictions then doing the test and being right is evidence, John. You don't have any.

0celo7

Ok, if you write equations, show me the term in the Lagrangian which gives rise to photon-photon interactions.

John Duffield

21:30

@dmckee : we do physics to understand the world. Not to be told to shut up and calculate, or that quantum physics surpasseth all human understanding. And the evidence that I do have is the evidence of electron diffraction, the Einstein-de Haas effect, et cetera.

yuggib

@JohnDuffield You are deliberately omitting the point that is raised (since many days) against you. @dmckee is just the last of a long series of people that is saying the same thing to you.

dmckee

So, show that you understand the world by making a prediction and testing it, already.

A pre diction, BTW. Not a post diction.

2

Danu

@DanielSank Guess where I'm going tomorrow? :D

dmckee

Disneyland?

0celo7

Greece

Danu

21:33

Hey, I'm 14 now, I'm too old for that!

0celo7

tfw I'm not much older than 14

I was 14 in 2011-2012

Danu

tfw Nobody is too old for Disneyland

[never been]

skill patrol

The circus?

0celo7

CERN?

California?

Danu

Ocelot got it right, from the fact that I addressed Daniel ^^

0celo7

21:34

good

John Duffield

@yuggib : I'm not omitting anything. I'm referring to evidence, but people like 0celo7 and Danu dismiss it because they think they know better when they don't. Danu didn't know about the Breit-Wheeler process. He's been taught that photons don't interact with photons, and he believes it, like some Sunday school kid.

0celo7

cuz the places were about to get a whole lot weirder

obe

@0celo7 I can imagine.

0celo7

my next guess would have been @obe's room, in fact

obe

D:

skill patrol

21:35

Sunday school kid?

Danu

@JohnDuffield :D Yes, yes, John. Very convincing :)

0celo7

@JohnDuffield please just show me the term in the Lagrangian

please

I need to see it

John Duffield

@dmckee : here's a prediction. It will be discovered that neutrinos aren't fermions. And that their mass varies because their speed varies.

Danu

Woops, there I go, responding again!

0celo7

if you show me I will delete my account

not kidding

yuggib

21:36

@JohnDuffield I will say it a last time. You are not only referring to the evidence (i.e. experimental observations), you are giving an interpretation of the observations. How objects interact is not observation, since you cannot observe them in the act of interacting. It is interpretation.

Danu

@JohnDuffield Ah, this is great!

Gnight guys

0celo7

@JohnDuffield wtf

Danu

Gotta recover from that US Open final last night

0celo7

@Danu night Dutch Warrior

dmckee

abstrusegoose.com/511

0celo7

21:37

@JohnDuffield what are they if not fermions

they're either fermions or bosons

and they're not bosons

hmm, can you have a state like $\propto |\mathrm{boson}\rangle+|\mathrm{fermion}\rangle$

Slereah

No

Because of

SUPERSELECTION RULES

0celo7

@JohnDuffield SHOW ME THE TERM IN THE LAGRANGIAN

Slereah

Oh wait

I guess what you could have is like

a scattering process

That produces either fermions or bosons

Like $e^+ + e^-$

John Duffield

@yuggib : electron diffraction is not interpretation. OK guys, I'm off. Nice talking to you. I hope you've learned something today. Nighty pight.

obe

lol...

skill patrol

21:42

Later pal

0celo7

show me the &@#&1ing term in the lagrangian!!!111

Slereah

Please stop lavishing him with attention.

0celo7

::punches @FenderLesPaul :: out of frustration

skill patrol

Crank him up and watch him spin.

0celo7

@Slereah this is why I want to meet him

obe

21:45

@0celo7 We will learn about einbein lagrangian this week.

Idk what that is.

0celo7

professional and nonprofit organizations [are usually identified] by .org

>4chan.org

it's a valid source!

Slereah

Either a poor spelling of Einstein or it's a vielbein in one dimension

0celo7

yeah

it's the thing you use to do massless particles

obe

idk I probably read it wrong off the blackboard.

0celo7

you introduce an einbein on the worldline

obe

21:46

then it's right.

0celo7

it's a way of formulating the relativistic point particle action

Zee's GR book covers this

Slereah

aka a cheaty lagrangian

obe

sigh... his book is too disorganized.

yuggib

@JohnDuffield And you are making seemingly related but in fact completely unrelated assertion to give yourself the impression of winning an argument. I am not arguing with you, just making a point (that you still fail to address, or even acknowledge).

0celo7

@skillpatrol I'm going to go on a mission after I finish this reading

Mission Impossible 4: Find Popcorn on the University of Tennessee Campus

::epic music starts playing::

@obe other places where you can find it: BBS, Polchinski

it's a good way to introduce you to the idea of introducting extra fields and then constraining the Lagrangian

IDK if BLT does it

if it does, then GSW probably does too

@ACuriousMind nice call on the profile pic, I look awesome

DanielSank

21:54

@Danu Munich?

@JohnDuffield Woah, what the? Photons can interact with photons directly?

What's Breit-Wheeler?

0celo7

DanielSank

I've heard of nonlinearities in electromagnetism, but I thought this was understood as an indirect interaction via charged fields.

@0celo7 Ok so there are charges involved. Bug whoop.

0celo7

yeah but it's not a vacuum process so there are some difficulties involved in making it actually happen

apparently the first large-scale verification was in 2014

Slereah

Well for a start it has two QED vertex

So it's ~ $\alpha^2$

Also I don't think it works for all polarizations?

Two photons together can have 3 spins, but two electrons can only have 2

yuggib

iopscience.iop.org/article/10.1088/1742-6596/497/1/012016/…

This article

seems to suggest that is actually only the nonlaser photon who undergoes the transition to positron electron pair

the laser field is defined as "driving"

however, I do not know much about that stuff

0celo7

22:12

not enough math

you deal in mathematical nonsense, not evidence

0celo7

22:28

@obe do you want me to spoil the einbein business?

obe

@0celo7 if you feel like it,

i'll be afk sorry.

0celo7

are you studying QM

obe

I should be.

brb

DanielSank

23:55

Are @JohnDuffield and CuriousOne secretly the same person?

0celo7

hmm?

@DanielSank why do you think that?

0

Q: How many calories would I need to consume to travel at the speed of sound?

How many calories would a human need to consume in order to sustain a metabolism that would allow said human to travel at the speed of sound?

speed

Some people.

Transcript for