The h Bar

Lucky Chouhan

01:22

@MoreAnonymous then why not USA or Europe?

naturallyInconsistent

01:49

@Obliv wasnt this done in high school physics? It's fun

Ryder Rude

06:48

hi

Slereah

07:12

Ryder Rude

09:01

A.I. ‐ Humanity's Final Invention?

►

Slereah

09:24

citeseerx.ist.psu.edu/…

lol

Ryder Rude

09:36

@Slereah this paper has no math

Slereah

Sorry, you must use your mind

Ryder Rude

the premise and the intro r too vague...

it says "Plato and Aristotle introduced a metaphysical ontology in which things r certain, contrary to the pre-Socratic thought". And that this metaphysical framework only worked out for the macro world

i dont think Plato and Aristotle introduced this. they may have formalised it

Slereah

Perhaps this requires reading past the intro

Ryder Rude

maybe the metaphysical ontology was uncertain in the pre-Socratic thought, but thats not to say that pre Socratic thought aligns with QM

@Slereah it does not sell itself well

Slereah

Physicists are terrible at selling themselves

That is why you must read

Ryder Rude

09:50

i will read a few more sections. see if they make themselves clear

Ryder Rude

11:35

the latter sections give the impression that early philosophers were extremely confused about the universe

it is essentially Zeno's stuff : motion is impossible, All is One. everything is changing, therefore, everything both exists and doesnt exist, therefore contradiction

Slereah

They were just one generation after "A magic sky man did it"

Give them some slack

Of course it's Zeno stuff, he was an eleatics

Ryder Rude

yeah.. they talk about an eleatic ontology and another ontology that starts with P

@Slereah the paper says that even Newton was doing this stuff. he said that all objects had the spirit of God surrounding them, which somehow explained Forces

in the eleatic philosophy, everything is fixed and certain. while in the other philosophy, things are changing and dynamic

Slereah

Newton was powerfully insane

From bits I've seen in Jammer the idea of absolute space is based on some mystical notion that the universe is the body of god

Ryder Rude

the other philsophy is Heraclitian philosophy

it says everything is dynamic

@Slereah oh

Slereah

Yes

He is the famed guy of the popular platitude

You cannot cross the same river twice

Ryder Rude

11:42

yeah, thats what he says. u cant jump in the same river twice

were no women doing philosophy? they are all "he"

maybe they werent allowed or not taken seriously

WaveInPlace

Greek women weren't far from property, no?

Ryder Rude

probably

WaveInPlace

I wouldn't expect them to be allowed to do much.

Slereah

There are two famous women philosophers in Ancient Greece iirc

Hypathia and some other one

But yes it was a pretty patriarchal society

WaveInPlace

Hypatia was 350 AD.
https://en.wikipedia.org/wiki/Hypatia

I remember being really surprised when I learned how bad Athens was for women. Sparta was better, but terrible in so many other ways.

Slereah

11:46

Yeah when I say ancient greece I mean a period of like a thousand years

They weren't big on women's rights

Ryder Rude

it says Hypathia has written about conic sections

Slereah

Also she was the one killed by an angry mob

Ryder Rude

she was at least doing something tangible, instead of saying "motion is impossible" :P

@Slereah her death is associated with the destruction of library

Slereah

It's not really

Ryder Rude

sorry... it says some portrayals in the 20th century have made this association

Slereah

11:49

Shit happened at the library but there was no particular moment in history that was the destruction of the library

Same as always really

Ryder Rude

oh

Slereah

The people in charge stopped funding the library

WaveInPlace

This youtube covers the library's decline really well.
https://www.youtube.com/watch?v=M4WU8gqrgsQ

Slereah

People always want some great cataclysm or the decadence of society but most of the time when science turns to shit it's always just "they stopped funding it"

Ryder Rude

or the mongols maybe

for a short period

it says Plato and Aristotle each unified the Eleatian and the Heractilian philosophies

Plato had a two layered philosophy with the Eleatian layer being the unchanging forms and the Heractilian layer being the subjective experience i guess

aristotle seems to disagree with the above, but i still dont know what he disagrees about :P

the point seems to be that these vague ideas were once useful in the development of math. they eventually lead to spacetime and things on top of spacetime

but even after that, people got confused and started debating how atoms could live on spacetime, as in, they cant overlap with spacetime :P

WaveInPlace

11:56

Epicurious apparently taught quite a few female philosophers. Almost nothing of their work remains, which is hardly surprising.
https://en.wikipedia.org/wiki/Epicurus

Ryder Rude

but the paper is saying that these old ideas can still be useful in interpreting Quantum mechanics, which is wrong

they r too vague to say anything about qm

Slereah

It's fine

People just get inspired by old ideas

I've seen what people said about Hegel's ideas in the 19th century and it wasn't category theory

Ryder Rude

yeah... these ideas can turn into non vague things over time

it says Descartes didnt make a distinction between objects and space, as in, objects r nothing more than the spatial extent

Slereah

Sometimes you just gotta go back to the basics just in case you're too ossified in your formalism

Ryder Rude

there was some debate about how indivisible atoms could live on top of an infintely divisible space

Gassendi gave an argument for how matter and space could co-incide without interfering with each other

he said that space didnt have qualities, so it didnt interfere

which means nothing at all... lol. But Gassendi was on a right track i guess

@WaveInPlace he had a theory of free will, where things sometimes deviate from their expected path, thereby escaping determinism

More Anonymous

12:29

@LuckyChouhan it's easier to migrate to canafa

WaveInPlace

12:59

@RyderRude @RyderRude That would fit in with teaching women pretty well. Cool.

Ryder Rude

yeah... he seems to practice what he preached

Slereah

That was the style at the time

You just promoted a lifestyle and went nuts with it

Ryder Rude

like being one with beans

WaveInPlace

It would be darkly hilarious if Pythagorus were only known for his fear of beans.

Slereah

If you wanted to just say bullshit and get paid you just became a sophist instead

Ryder Rude

13:06

they were getting paid?

Slereah

Sure

Ryder Rude

@WaveInPlace he feared them?

Slereah

They were basically the lawyers of the era

WaveInPlace

iirc, yeah

Ryder Rude

@Slereah no law books in that era?

they would each be lawyering in their own philosophical framework :P

like a determinist lawyer argues his client did nothing :P

WaveInPlace

13:09

Oh wow, it was weirder than I thought. He thought beans were reincarnated humans.
https://www.iflscience.com/pythagorass-belief-that-beans-are-human-may-have-killed-him-58261

Slereah

There were laws, although a bit looser

But at a trial you basically had to advocate for yourself

So it was useful to get good rhethorics training

Ryder Rude

@WaveInPlace i think pythagoras did pyschedelics

maybe he became a bean once

Slereah

Pythagoras did the most reckless thing of all

He left behind no writings

So pretty much anything we know about him is basically bullshit

Ryder Rude

his followers worshipped beans though. unless his followers came into existence centuries later, they got that from pythagoras

Slereah

Did they

I'm not sure which source talks about the bean

Ryder Rude

13:13

oh..

WaveInPlace

This link is a little more evidence based. Short answer: no one knows, but he definitely didn't want people to eat them.
https://thehistorianshut.com/2024/06/26/pythagoras-curious-relationship-with-beans/

Slereah

Might be like how in modern days people will say that liberals worship the (coffee) bean (because they go to starbucks)

WaveInPlace

Science pre-scientific method: Pretty much anything we know is basically bullshit.

Slereah

@WaveInPlace It's from Laertius

I wouldn't 100% trust it :p

Ryder Rude

might be, but also not implausible that they were strange people. cults exist even today

Slereah

13:15

He was the ten fun facts about philosophers guy of antiquity

Ryder Rude

we will never get to know history for sure.... strange how it's literally unaccessible forever

relativity makes far future accessible, but not past

do u think the nature of philosophical debates have changed? earlier, there were debates about how motion implies that things dont exist. have we moved on past that

maybe the debates are less confused today. with well listed assumptions and conclusions

math and physics have certainly moved past that phase... when people do GR, they dont ask questions like that

WaveInPlace

@Slereah I didn't know that. Good to know.

Slereah

I mean it's maybe true but who knows

Pythagoras we have basically zero first hand sources

WaveInPlace

True, but it's not unreasonable to assign likelihood ratings to ancient sources. And some not quite so ancient ones.

Slereah

I also think he probably didn't have a thigh made of gold

WaveInPlace

13:26

Blasphemy.

Ryder Rude

@WaveInPlace standardised ratings would be great. like multiple committees each give a rating based on member historian vote, so that one can check multiple ratings of any historical event

WaveInPlace

@RyderRude those do exist, though I don't know too much about how widespread/acknowledged they are. People have categorized Jesus's actions by the likelihood that they occurred, for example.

For the most part I doubt we have enough independent sources to categorized most ancient works though. When you only have random quotes from people talking about someone (and none of the original work) it's pretty hard to do much.

Ryder Rude

it would be great if they exist and are recognised by most historians. history really needs standardisation

but ive never come across such a system

without standardisation, all u r left with is 600 pages of opinion for each historian. and for every historian that says something is credible, there's another historian who says it's not credible

and there's no aggregation or standardised scores. it's a hopeless field to learn anything from

WaveInPlace

lol, the historians seem to manage.

Ryder Rude

they too have no idea if their opinions are biased

they couldve just done a phd while never getting to know about contradicting views

WaveInPlace

13:36

Different fields have different approaches to knowledge, guided by the shape of the information. There isn't a one-size-fits-all approach.

Ryder Rude

i just dont agree with the historian approach to knowledge lol. but maybe theyre managing

Slereah

History has different epistemology from physics

For rather obvious reasons

Mr. Feynman

14:53

I'm getting triggered by the starred comment about "ACurioußMind"

Why would he include a double s in the username?!

ACuriousMind

15:13

@Mr.Feynman none of the people who wrote or starred that message understand what an ß is, they've just seen me use it for Gauß :P

4

Claudio

Acuriou(ß-1)Mind

Mr. Feynman

-s, not -1

Claudio

right wrong units

Mr. Feynman

Or rather /s

AcurioußMind/s

@ACuriousMind I hoped I would find a reply of yours to that but you didn't even bother to complain!

Claudio

Did anybody read Joseph Polchinski's memories?

ACuriousMind

16:12

@Mr.Feynman also not quite right, since ß doesn't really stand for ss, but is originally a ligature of sz - it is only substituted by ss when ß is not available because sz at some point merged phonetically with ss so they are pronounced the same and sz has fallen out of use outside of words written with ß for historical reasons

@Claudio yes, but to be honest I don't remember much of them, so they didn't leave any particular impression on me :P

It's mostly a narration of his life talking about the physics he did, interesting as a historical artifact and not written in a particularly exciting style, but really all I learned was that he really was a theoretical physicists who apparently mostly cared about the physics he did and little else

Mr. Feynman

16:29

@ACuriousMind So was Gauss originally pronounced Gausz?

Unless this merging happened a long long time ago

naturallyInconsistent

Maybe his name was pronounced just like gauze

ACuriousMind

16:45

@Mr.Feynman the history is confusing and not particularly clear, but Gauß would have pronounced his name as modern Germans do today, the relevant consonant shifts here happened at some point between the 3. and 15. century

Slereah

Did the germans even have writing in the third century

I thought back then they just threw each others in bogs

ACuriousMind

the normalization of German spelling happened relatively late in the 19th century, but they preserved some of these features that no longer made any difference to pronounciation

@Slereah no, but the consonant shifts started back then - the "problem" is that at some point, German had many distinct sounds that had to be represented with a combination of s and z produced by what is still dentals in English (English that vs. German daß*/*das) that would have each had a different pronounciation, but then ss and sz collapsed into one sound, but people kept writing the words with either of those and then the 19th century people just froze a particular variant

it's a mess, but this is the worst weird historical spelling issue in modern German, so compared to English and French we got off easy :P

imbAF

17:17

Can someone help me regarding two questions I have about the S.G/ spin component and measurements?
1. When two operators A and B do not commute, the two following statements are said about them:
1)We cannot measure the two observables simoultenously.
2) The probability of measuring an arbitrary eigenvalue for A followed by an eigenvalue of B, is not the same as the probability of measuring the same eigenvalue of B initially and then that of A.
Now when we measure the Z-component of spin with eigenvalue $\frac{\hbar}{2}$ and after that we measure the X-component of spin and we get $\pm\frac{…

ACuriousMind

@imbAF Since you didn't compare it to measuring the observables the other way around, how could it possibly relate to your second statement?

imbAF

No

But I can't see how it's related to the first?

ACuriousMind

I mean, it's not particularly related to the first either from what you said :P

imbAF

Cuz, it's not as if we are actively trying to measure 2 components at the same time and we are failing to do so. Our setup is such that we try to measure one component at a time

ACuriousMind

I'm puzzled by the whole setup here, why would you think any of these two statements is specifically related to the sequence of measurements you've talked about

imbAF

17:23

Because spin components do not commute and since we are performing measurements of them, I thought that this characteristics of them will be manifested when measurements are performed

ACuriousMind

yes, but not by the particular sequence of measurements you've mentioned :P

to demonstrate 1), I would make a three-step measurements of z-spin, x-spin, z-spin, and since the second z-spin measurement will not have a single definite outcome, this means we cannot attribute both a definite x-spin and a definite z-spin to the particle

imbAF

I thought of including the triple sequential measurement

But in that case what I get is that measuring an observable that does not commute with what we measured

that influences the measurement outcome of the measurement of the initial observable that we consider

ACuriousMind

to demonstrate 2), I would start with a state of definite x-spin (let's say x-up). Then the probability of measuring x-up, then z-up is 1/2, but the probability of measuring z-up then x-up is 1/4

imbAF

"and since the second z-spin measurement will not have a single definite outcome, this means we cannot attribute both a definite x-spin and a definite z-spin to the particle"
But I can't see how this is tied with the simultaneous measurement ?

ACuriousMind

@imbAF To measure two observables $A,B$ "simultaneously" would mean to get measurement results $a,b$ so that we can say the state is an eigenstate of both $A$ and $B$ with those eigenvalues. But the three measurements show that the state that is an eigenstate of z-spin is not one of x-spin and vice versa

it's not really about measuring observables literally "simultaneously" in the temporal sense, it's more about the idea that a measurement of one of the observables does not affect the measurement of the other, regardless of whether the measurements are subsequent in time or at the same time

imbAF

17:30

I see

But measuring X

does effect a subsequent measurement of Z

hence non commutative ?

ACuriousMind

yes, that's the point - you can get a different result for the x measurement after we've measured z (and vice versa) than you got from the initial x measurement

imbAF

ok

user 20458579510081670432

@ACuriousMind would you be offended if I used that username?

imbAF

Question 2:
Arbitrary spin component $S_{\vec n}=\vec S \vec n$
Corresponding eigenvectors:
$|+\rangl_{\vec n}=cos(\frac{\theta}{2})e^{-i\frac{\phi}{2}}+sin(\frac{\theta}{2})e^{i\frac{\phi}{2}}$ (eigenvalue +\hbar/2)
$|-\rangl_{\vec n}=-sin(\frac{\theta}{2})e^{-i\frac{\phi}{2}}+cos(\frac{\theta}{2})e^{i\frac{\phi}{2}}$ (eigenvalue -\hbar/2).
If I want to measure either eigenvalue, I'd need a 2nd S.G oriented in direction $\vec n$?

ACuriousMind

@user20458579510081670432 I would find it annoying and unfunny, yes

imbAF

17:35

And regardless in which eigenstate the system is found, one could measure the +\hbar/2 eigenvalue of Z-component in both cases /

ACuriousMind

I don't really understand either question

imbAF

Let's say you prepare system such that in a SG device where the magn. field poitns in the Z-direciton, you'd get 50-50 probability of a particle landing in one of the two spots

So the state is initially prepared, and then with a 2nd S.G device we make measurements regarding the eigenvalues of the Z-component of Spin

right>?

ACuriousMind

I mean, you're not forced to do the first preparation with an SG device (e.g. a source of uniformly random spin orientation also works), but sure

imbAF

SO the same logic you'd apply for when we consider an arbitrary component of the spin vector operator

Meaning

You'd "force" (lack of vocabulary) the system two be in one of the two eigenstates and then with a follow up S.G device you'd perform a measurement of the observable

And the particles would hit one of the two spots

corresponding to eigenvalues (states):
$|+\rangl_{\vec n}=cos(\frac{\theta}{2})e^{-i\frac{\phi}{2}}+sin(\frac{\theta}{2})e^{i\frac{\phi}{2}}$ (eigenvalue +\hbar/2)
$|-\rangl_{\vec n}=-sin(\frac{\theta}{2})e^{-i\frac{\phi}{2}}+cos(\frac{\theta}{2})e^{i\frac{\phi}{2}}$ (eigenvalue -\hbar/2)

ACuriousMind

...and the question is?

imbAF

17:42

If we would want to measure the Z-component of spin, you'd be able to measure i.e +\hbar/2 for when the system would be in either eigenstate?

ACuriousMind

I'm not really sure what you're after here: By the Born rule, the result of measuring z-spin is one of its eigenvalues, i.e. $\hbar/2$ or $-\hbar/2$. What does it have to do with the specific state?

imbAF

I considered the state, just as an example, I was trying to be specific

But if what I said above is correct, and since you didn't correct, I take it to be

ACuriousMind

yes, but...the example doesn't matter. I'm concerned that there is some fundamental misunderstanding here if you think the answer to the question depends on the specific state

imbAF

I already understand

No the state of the system is irrelevant

you just perform inner product between the eigenstates of the observable you consider with the state in which the system is

square amplitude and you'd get the probability

I hope I am correct on this

ACuriousMind

yes

imbAF

17:51

Ok, thanks for both answers

Might ask you again about scattering in QM, because Cohen tanoujids way of describing it is kinda of a mess

Just like his description of the quantized energy values of the H-atom

user 20458579510081670432

International Online Physics Competition

> It is possible to compete in Czech and English language.

🏆

SnoopyKid

18:56

Hello, does anyone here have a background in medic? Does this article sciencedirect.com/science/article/pii/S1888441523000899 tells us the axial compressive strength of human humerus? Thank you

imbAF

Can someone help me with the following thing:
I have:
$\frac{d^2}{dt^2}x_{1,2}(t)+\omega_0x_{1,2}(t)=0$.
I have the following conditions:
$\omega_0x_2(t)=i\frac{d}{dt}x_1(t)$
$\omega_0x_1(t)=i\frac{d}{dt}x_2(t)$
$x_1(0)=1$ and $x_2(0)=0$.

The solution is supposed to be $x_1(t)=cos(\omega_0t)$ and $x_2(t)=-isin(\omega_0t)$.
I am trying to get this results but I can't

I get $x_2(t)=C_1e^{i\omega_0 t}+C_2e^{-i\omega_0 t}$ For which, while considering the initial condition I get: $X_2(t)=-2isin(\omega_0t)$.
For $x_1(t)=D_1e^{i\omega_0 t}+D_2e^{-i\omega_0 t}$. With the initial condition:
$x_1(t)=2iD_1e^{i\omega t} + e^{-i\omega_0t}$.

imbAF

19:20

I was able to solve it

imbAF

20:18

What does it mean when we say: "for which the projection of the spin has the uncertainty zero" ?

Silly Goose

20:58

what is "total escape rate" in the context of classical markovian stochastic processes?

Claudio

21:10

@ACuriousMind thanks for the pieces of information, I'll probably put it on standby for now, since it doesn't sound as compelling as I imagined.

Mr. Feynman

21:30

@ACuriousMind I don't know how much this will hurt you, but I pronounce the "ss" Gauss like those in "sassy"

Heya @SillyGoose QUACK

Silly Goose

22:41

s q u a c k!

Sir Cumference

23:00

Kind of wish statmech classes made more of an effort to point out that there's a difference between thermal equilibrium and thermodynamic equilibrium

They sound similar so that was a point of confusion when I first started

I mean the textbooks do define them differently of course, but they never really warn about how similar the names are

Sir Cumference

23:14

@imbAF Probably just means "in which direction is the spin well defined?"

I.e. which component of the spin is our particle in an eigenstate of

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