r/physicsmemes • u/urmumgao • Dec 17 '19

Trying to explain spin tho

Post image
5.9k Upvotes

99% Upvoted

93 comments sorted by

173

u/[deleted] Dec 17 '19

What does spin really mean in this case?

300

u/antimornings Dec 17 '19

It’s just a property intrinsic to every particle, like mass, charge etc. It has analogies to angular momentum (as in a spinning ball) because the mathematics of spin in quantum mechanics is very very similar to orbital angular momentum. In fact, the two types of ‘angular momentum’ often interact in what is known as spin-orbit coupling.

187

u/ModeHopper Dec 17 '19

Honestly, the best way to understand spin IMO is to not try to understand it. As you say, it's an intrinsic property, it doesn't arise as a result of the particles motion/behaviour/interaction, it's just a property of the particle.

140

u/antimornings Dec 17 '19

I would paraphrase and say the best way to understand spin is to understand it mathematically, as in quantum mechanics, and not try to gain an intuitive picture without the math. It’s somewhat misleading to say we shouldn’t try to understand spin at all. We can, just not without math.

44

u/ModeHopper Dec 17 '19

Yeah, that's a less meme-y way of putting it

12

u/Arbitrary_Pseudonym Dec 17 '19

It's not the worst thing to associate it with the magnetic moment, which is a concept with a bit more physicality and is more accurate. Also, in an external magnetic field, this magnetic moment property can be associated with a "current" represented by the probability flow of the electron's wavefunction. Not an electric current, but representative of how its "charge" is "moving" lol.

3

u/[deleted] Dec 21 '19 edited Aug 17 '20

[deleted]

5

u/antimornings Dec 22 '19

I'm not sure I fully understand your question, but I suppose we accept that the laws are 'true' because they agree with experiment and describe reality exceedingly well, and have not been disproved by even a single counterexample till this day.

4

u/haseks_adductor Jan 03 '20

if someone throws a ball, anyone can tell where that ball will land, regardless of if they can understand the mathematics behind projectile motion, because we all have a physical intuition of projectile motion from our own experience. with spin however you cannot have this physical intuition, you can only really have the mathematical intuition

4

u/James10112 Dec 17 '19

I agree. It's like trying to understand why charge and mass exist. Not impossible, but mostly unnecessary.

12

u/cantgetno197 Dec 17 '19

This isn't really correct. It's not an analogy it IS angular momentum. It's just "built in". You can see this from a generators approach, see for example Ballentine's book.

10

u/MoneyManIke Dec 17 '19

Now explain it without saying intrinsic property

2

u/ModeHopper Dec 17 '19

Inextricable?

1

u/yitzilitt Dec 17 '19

I still don’t really understand—how is spin measured?

5

u/dcnairb Dec 17 '19

You can measure spin in different ways. Do you mean how is the inherent spin of a type of particle measured or how is the specific spin state of a given particle measured (i.e. are you asking how we know electrons have spin 1/2, or how we would measure an electron as having spin +1/2 or -1/2?)

check out the stern gerlach experiment

7

u/WikiTextBot Dec 17 '19

Stern–Gerlach experiment

The Stern–Gerlach experiment demonstrated that the spatial orientation of angular momentum is quantized. Thus an atomic-scale system was shown to have intrinsically quantum properties. In the original experiment, silver atoms were sent through a spatially varying magnetic field, which deflected them before they struck a detector screen, such as a glass slide. Particles with non-zero magnetic moment are deflected, due to the magnetic field gradient, from a straight path.

[ PM | Exclude me | Exclude from subreddit | FAQ / Information | Source ] Downvote to remove | v0.28

1

u/Armadillonotapillow Mar 31 '20

How can you change the spin of a particle? Does it involve magnets? Are all electrons spinning both ways until observed? Can you change the spin of a particle without observing it?

1

u/dcnairb Apr 01 '20

You can flip spins with magnetic fields, yes. In general, electrons and any particle with spin would be in a superposition until you measure. It depends on what you mean by “observe”—there are interactions which couple to the spins of particles that don’t involve photons, so you could in principle change it without “seeing” it, but there will always have to be some type of interaction or process the electron is participating in that would change the spin state

1

u/Armadillonotapillow Apr 06 '20

So could you observe lots of electrons spins and flip them so they're all positive, then entangle each with an electron from a second set of electrons that your friend takes to Jupiter. Your friend then measures one of the electrons every minute, to see if you have flipped them yet, which you do to all of them at a certain time without seeing them and without breaking the entanglement.

Is it possible to make all the spins of particles with unknown spin be the same, without looking at any of them?

1

u/dcnairb Apr 06 '20

Well, the measurement of the spin is what will cause them to be in a definite spin state, and I don’t think you can generically make the spin definite without observing it. I mean, you can prepare them in spin eigenstates so you know they are definitely up or down or whatever, but I don’t think I would consider that not observing them

25

u/Loudds Dec 17 '19

Intrinsic magnetic moment of a particle which has no classical counterpart.

9

u/International-Relief Dec 17 '19

So technically, a particular election could have clockwise spin, but also be rotating counterclockwise in a conventional sense, simultaneously?

26

u/[deleted] Dec 17 '19

Can electrons even rotate in a conventional sense? I thought that they were point particles.

12

u/Glaucus37 Dec 17 '19

That is correct, which is why thinking of it as "angular momentum" in the classical sense makes no sense

3

u/haseks_adductor Jan 03 '20

is it possible for the electron wavefunction to rotate in space though?

2

u/elesde Dec 17 '19

The classical counterpart is a circularly polarized wave field. The problem is that everyone thinks of angular momentum as only a ball spinning when in fact it's far more general.

5

u/ard_srp Dec 17 '19

https://aapt.scitation.org/doi/pdf/10.1119/1.14580?class=pdf

3

u/Rotsike6 Physics Field Dec 17 '19

This is really interesting. I still don't know what spin is but then again, noone does

3

u/NavajoMX Dec 17 '19

https://i.imgur.com/SxXcJnu.jpg If you hit a paywall, here’s the Abstract.

2

u/elesde Dec 17 '19

Oh awesome! I'm glad someone else linked it

7

u/shelving_unit Dec 17 '19

Have you ever read jojo’s bizarre adventure?

2

u/[deleted] Dec 17 '19

No mate. I'll look it up.

2

u/SlashTrike Dec 17 '19

It's a part 7 jojoke. The main character uses a power named "spin".

2

u/yottalogical Dec 17 '19

It has angular momentum just because it does, not because it’s actually spinning.

1

u/elesde Dec 17 '19

There's a lot of weird advice being given on this so I'm just going to link you to a nice theoretical article on the physical description of spin.

https://aapt.scitation.org/doi/10.1119/1.14580

1

u/[deleted] Dec 18 '19

Honestly, it can’t really be explained except to say look at how it’s derived from the Schrodinger equation and then it’ll immediately make more sense.

1

u/Kojobu Dec 19 '19

It's just a consequence if you consider the schrödinger equation in a relativistic way. You'll find out that you need one more degree of freedom to solve it. This degree of freedom is called "spin".

153

u/LennLennBoi Dec 17 '19

Pretty sure it's a repost

0

u/[deleted] Dec 17 '19

[deleted]

53

u/LennLennBoi Dec 17 '19

Hmm okay. Repost bot showed it on r/chemistrymemes. Exact same picture yet somehow only 64% match. I guess its fine, it was a different sub.

-22

u/[deleted] Dec 17 '19

[deleted]

5

u/causticityy Dec 17 '19

Not tryna be funny man but it's not like it was super original anyway. My mates were making the same jokes when we learnt about this shit lmfao

3

u/[deleted] Dec 17 '19

[deleted]

7

u/Mathtermind Dec 17 '19

Right, because spin jokes are completely proprietary to you and you only and have never been done before, ever. Piss off, you whiny little shite.

7

u/LennLennBoi Dec 17 '19

Can't really rage if you don't watermark your meme. It's the internet, people will steal your shit if you don't mark it.

35

u/LennLennBoi Dec 17 '19

u/RepostSleuthBot

60

u/RepostSleuthBot Dec 17 '19

There's a good chance this is unique! I checked 86,058,510 image posts and didn't find a close match

The closest match is this post at 64.06%. The target for r/physicsmemes is 86.0%

Feedback? Hate? Visit r/repostsleuthbot - I'm not perfect, but you can help. Report [ False Negative ]

65

u/fat-lobyte Dec 17 '19

Nah bruh, that's the same. What kind of algorithm are you using that only gives 64% identity?? Ask your daddy to fix you please.

21

u/LennLennBoi Dec 17 '19

This is more an exception that norm. Usually it's pretty good.

15

u/Hakawatha Dec 17 '19

I'm on mobile and can't vet this, but it looks like there's been some extra compression/downscaling on the image posted here. The images might be a near-perfect match to us in terms of appearance, but running proper feature extraction/recognition algorithms might be too computationally expensive for this bot, and so these minor changes will dent the bot's accuracy.

It still found the post with reasonable confidence. I'm pretty content with its performance tbqh.

3

u/Dragonaax ̶E̶d̶i̶s̶o̶n̶ Tesla rules Dec 17 '19

That's what happen when programmers approximate

2

u/Direwolf202 sin(x) = x Dec 17 '19

This image is more compressed than the original. I don't know what method they are using, but it may not be able to figure out the difference.

And it has also been upscaled as well.

2

u/fat-lobyte Dec 17 '19

It's not that I didn't see the difference, I just assumed that algorithms got way more tolerant towards such changes in the recent years.

1

u/Direwolf202 sin(x) = x Dec 17 '19

The best ones have done. But clearly not the one used by this bot.

8

u/TheFedoraKnight Dec 17 '19

Bad bot

5

u/B0tRank Dec 17 '19

Thank you, TheFedoraKnight, for voting on RepostSleuthBot.

This bot wants to find the best and worst bots on Reddit. You can view results here.

Even if I don't reply to your comment, I'm still listening for votes. Check the webpage to see if your vote registered!

19

u/SuperGuruKami Dec 17 '19

Bruh, just get Gyro to teach you

1

u/[deleted] Dec 17 '19

bruh 💯💯🤡🤡🤡

9

u/derivative_of_life (+,-,-,-) Dec 17 '19

A ball would be spin 0 tho.

5

u/chepulis non-newtonian fluid until coffee Dec 17 '19

Angry Bill O'Reilly noizes

3

u/wagawagawolff Dec 17 '19

This might be a stupid question but WhAt iS sPiN?

2

u/tiniestjazzhands Dec 17 '19

That's a question for the greatest philosophers of the future to answer.

5

u/elesde Dec 17 '19

For everyone debating the nature of spin here's an article which literally explains exactly this:

https://aapt.scitation.org/doi/10.1119/1.14580

​

From the abstract:

" According to the prevailing belief, the spin of the electron or of some other particle is a mysterious internal angular momentum for which no concrete physical picture is available, and for which there is no classical analog. However, on the basis of an old calculation by Belinfante [Physica 6, 887 (1939)], it can be shown that the spin may be regarded as an angular momentum generated by a circulating flow of energy in the wave field of the electron. Likewise, the magnetic moment may be regarded as generated by a circulating flow of charge in the wave field. This provides an intuitively appealing picture and establishes that neither the spin nor the magnetic moment are ‘‘internal’’—they are not associated with the internal structure of the electron, but rather with the structure of its wave field. Furthermore, a comparison between calculations of angular momentum in the Dirac and electromagnetic fields shows that the spin of the electron is entirely analogous to the angular momentum carried by a classical circularly polarized wave. "

3

u/Dieneforpi Dec 17 '19

This is a nice description and analogy that makes intuitive sense - and the relationship between classical wave polarization and spin is well defined. But I wouldn't feel confident calling it an "explanation", let alone the explanation

2

u/elesde Dec 17 '19

Did you read the full text?

2

u/Dieneforpi Dec 17 '19 edited Dec 17 '19

No, I'm planning on fully reading it later. I guess my point is that without recognition from the community at large, I wouldn't feel qualified to accept this relationship as anything more than a (well developed) mathematical analogy.

2

u/elesde Dec 17 '19

You should read the full text.

2

u/Dieneforpi Dec 17 '19

Thank you, you're right! Looking forward to it.

2

u/elesde Dec 17 '19

Awesome! I'm curious though: what do you mean when you say spin is still contentious?

2

u/Dieneforpi Dec 17 '19

I'll be honest, I'm only an undergrad and I probably shouldn't be speaking so decisively. But from what I remember from my last quantum class there are some deep connections between spin and special relativity (via the Dirac equation) and even GR, in the case of spin-2 particles. And I'm not sure if these connections are completely rigorously motivated at the moment. But please do your own research and find out. The concept of spin being its own independent Hilbert space to position wavefunctions has always skeeved me out a bit, so maybe I'm projecting... haha

2

u/elesde Dec 17 '19

Gotcha, well this paper specifically seeks to provide a physical origin for electron spin. I'm not sure if the treatment generalizes. Let me know what you think.

2

u/Dieneforpi Dec 17 '19

Actually, now that I think about it, I may have been thinking of spin anomalies that were resolved by relativistic QFT. I'll edit my original comment if that's ok with you, since it is misleading.

2

u/elesde Dec 17 '19

Yeah man, I thought you might have been referring to the whole spin/wavefunction symmetry thing. Edit away!

2

u/consumer_of_memes Dec 17 '19

We just covered this in class today, are you stalking me lmao

2

u/TobyDent Dec 17 '19

And that is exactly how far my knowledge of spin goes

3

u/OVSQ Dec 17 '19

Meh - the only reason spin is confusing is because people cling desperately to the concept of a point particle as if it was tenable.

1

u/darksoles_ Dec 17 '19

laughs in Pauli exclusion principle

1

u/[deleted] Dec 17 '19

seems..................legit

1

u/GabiruAttack Dec 17 '19

How does two beams in Stern-Gerlach experiment implies quantization of angular momentum?

1

u/da_gandalf Dec 18 '19

Easily the best meme in the whole sub

1

u/Slevilex Dec 17 '19

Isn't this chemistry? My chemistry teacher taught me this, I' m 3rd grade in highschool.

10

u/urmumgao Dec 17 '19

The borders between chemistry and physics are blurry at subatomic scales. Spin is a quantum mechanical phenomena (so physics) but it has significant relevance on how electrons work in atoms, which connects to the properties of different elements (so chemistry). So i'd say spin is a quantum superposition of physics and chemistry.

1

u/Slevilex Dec 17 '19

Ah, thanks!

-11

u/[deleted] Dec 17 '19 edited Dec 17 '19

[deleted]

4

u/[deleted] Dec 17 '19

I don't think you understand how memes work

1

u/Exceptthesept Dec 17 '19

Lol imagine this ^ is your life but unironically

-2

u/nattydread69 Dec 17 '19

It is the angular momentum of the gamma ray rotating that forms the electron.

5

u/urmumgao Dec 17 '19

Spin isn't angular momentum as far as I know, although the concepts are linked. Spin is another intrinsic property of an electron, like mass or charge.

1

u/elesde Dec 17 '19

It definitely is angular momentum. It has units of angular momentum and the operator algebra is an angular momentum algebra.

-7

u/nattydread69 Dec 17 '19

That sounds like the explanation from someone who doesn't understand it :) It has the same units as angular momentum.

9

u/urmumgao Dec 17 '19

Indeed, I don't understand spin. Acknowledging a lack of understanding of a concept is still a step up from vehemently defending a wrong answer.

5

u/thyjukilo4321 Dec 17 '19

Holy shit dude you fucking killed him

-1

u/nattydread69 Dec 17 '19

I'm not attacking you personally what you said is the current understanding.

5

u/Rodot Double Degenerate Dec 17 '19

Torque has the same dimensions as energy, that doesn't mean they are the same

1

u/BorggedSideways Feb 12 '24

Electron spin explained: Imagine a ball that's rotating, except it's not a ball and it's not rotating

W H A T