The surprising reason behind electron ‘spin’! (They don’t REALLY spin)

Electrons don't really spin. Yet, every chemistry teacher will tell you they do. Everyday. Why do they do that? What does the 'spin' really mean?
In this video, we will explore the idea of spin angular momentum. We will see how electrons precess in the presence of an external magnetic field, just like how a spinning table top does.
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[@Picasso_Picante92]

59. I am 59 years old. Studied physics in high school and university. Read many many popular science books written by all the greats. And in 15 minutes you helped me understand something that never ever made sense to me. Thank you dear friend. You have a new subscriber.

[@dp5475]

40+ (let's say) year old engineer. Same hear.

[@edwardofgreene]

58 here. Ditto.

[@BogdanBaudis]

Same here, down to the point, simple enough but not simplistic, Bravo!

[@bhisham2687]

Study with focus and have imagination😅

[@bijukumarkn4626]

yes, i feel the same, Thank you.

[@nealharder]

I love how he refers to experiments that "we" have done, referring to us, team humans, and he's so excited to be on that team!!! Go us!!!! We can do incredible things!!!!

[@Minisynapse]

Agree! It's a part of scientific thinking 😁 We're all in this together, no one can or could have figured it all out alone, and we can all reap the fruits of scientific progress.

[@thisrandomdude2846]

HELL YEAH!!!!!!!!!!!! WE HUMANS ARE PRETTY DARN COOL NGL

[@johnjeffreys6440]

ever see the moon model. It doesn't spin either so-to-speak. The same side faces the earth at all times. It's really tough to comprehend.

[@chocoolatey]

​@@johnjeffreys6440 Unless I misunderstood you, the moon actually does rotate, it just turns out that it is tidally locked to Earth and rotates on its axis at the same rate it moves around the Earth giving the illusion it doesn't rotate. But if it didn't rotate we would see the other side of the moon which we never do.

[@johnjeffreys6440]

@@chocoolatey I think it’s analogous to a ball in a sling. A person is spinning the sling the ball will appear to be stationary on its axis from the person’s perspective unless maybe you looking down on it from aBirdseye view. I hate auto correct

[@Summerisle1961]

I love your conversations with Einstein/Feynman etc. They really bring the concepts to life.

[@Batwam0]

I know right, I was thinking gosh, he is so lucky having been able to talk to all these famous scientists!

[@jesublade356]

They are dead tho ☠☠

[@forkenstein]

@@jesublade356 no shit sherlock

[@termitetoxin7983]

@@jesublade356yeah with that attitude

[@giancarloarcenal622]

wth! when? @@jesublade356

[@dappy9988]

I love this guy, I genuinely NEED to see a gold play button somewhere in the background somewhere in the near future.

[@jamesh318]

This is a very good explanation. As an old physicist I can say, I wish we had these powers of visualization decades ago. It took me years to establish a mental model for electron spin, and you’ve done it in a few minutes! To be fair, there was a lot more mathematics involved but an intuitive model is super useful. Perhaps you can explore this further by talking about some of the experiments that established the existence of the electron and its spin and magnetic nature.

[@abdulkhadarainur4348]

Really thank you sir, for keeping this marvelous field of science alive through your memories. Because of our predecessors, we've got a headstart. But don't worry sir, we will further enhance Physics with each coming generation.

[@TailoredReaction]

If you want to totally blow your mind, think of gravity as though a sphere is expanding (getting bigger) at an accelerating rate. To an observer in the vicinity, the sphere appears to exert a "force" away from its center. Then imagine another sphere does the opposite, it contracts (gets smaller) at an ever increasing faster rate. To an observer the sphere would appear to be accelerating away. In the first instance if you were out in space you would have no way of telling whether you were being drawn towards the sphere or the sphere itself is expanding. In the second instance you would have no way of knowing if the sphere is shrinking at an accelerating rate, or if the sphere is moving away from you at an accelerating rate due to some mysterious "dark energy". We could be just like the two frogs in a well. We may be approaching the 'end of physics' unless and until we can get out of our well. I think the first step is to understand you are in a well.

[@abdulkhadarainur4348]

@@TailoredReaction Really thank you. Your insights help a lot.

[@giannismentz3570]

As an old physicist, would you be so kind to explain to this joker that electrons not only do not circle, have no angular momentum, no spin, and in truth, they do not exist.

[@jamesh318]

@@giannismentz3570 It's all just a simulation lol

[@brucehilton1662]

I was a practicing magnetic resonance spectroscopist in my career, and taught courses that focused on spin dynamics. So it's not an unfamitiar subject to me. Even so, Ifound your presentation insightful and pleasing. Good work.

[@Mahesh_Shenoy]

Wow, that's incredibly encouraging, Bruce. Thanks :)

[@ezdlc2693]

Hi Bruce 🙋‍♂️

[@hillaryclinton2415]

MRI is proton spin, not electron. Edit.. nope.. it's precession of a spinning proton.. not the same thing

[@NicolasSchmidMusic]

It’s physically the same. It’s as if you would say that that the speed of a ball was not the same as the speed of a car. Also some NMR technics actually use electron spin because they get more easely polarized and then transfer this electron spin to nuclear spin by shining a microwave source. This is called « hyperpolarization »

[@rinzhler6922]

​​@@hillaryclinton2415If you check his comment, he mentioned 'spin dynamics' and that 'he is familiar with it' . 🙂

[@danilo49252]

This is an extremely well put and organized way to explain electron spin. I greatly appreciate the humor and the way of narrating through the whole story, and most importantly not omitting the smallest of details that fill in all the little gaps and ultimately form the full picture. Thank you so much for this video!

[@craigwall9536]

If you think he "explained" spin, you will have to UNlearn things later. This guy suffers from a overdose of mysticism. "They can NEVER spin!" Yet they cannot be distinduished from a spinning object? He needs to go back and thin about "observables". And that imcluded the tools in your imagination by which we construct these flawed "Gedanken Experiments". He says it can't spin because nothing extends from a point that can observed circling the axis. So your assertion that a point "CANNOT SPIN" reduces to : connot be OBSERVED to spin" which is NOT the same thing!!!!

[@I_Am_AI_007]

“Individual pieces of cell aren't alive” Mitochondria: 💀

[@terencehawkes3933]

This is the first time I have ever heard such a clear explanation that I, a layman, can understand. Thank You!

[@codingbloke]

What a brilliant way to explain this concept. I'm an avid watcher of physics youtube videos and have seen many that "explain" that quantum spin isn't really spin but most just leave it at that even when that is subject of the video. This "conversation with a physicist" style where you ask the obvious questions that I as viewer would have was really refreshing and informative. I have seen much material already on this subject, I rarely learn anything new, I did today! Well done!

[@Mahesh_Shenoy]

Wow, glad to hear that!

[@blueckaym]

The reason table-tops are stable when spinning is centrifugal forces. Yes practically everyone knows that, but why specifically? Well the spinning top has some energy, or angular momentum, and we know that it'll spin until it loses its energy. That energy obviously comes from the rotation, but all the particles of the top would prefer to continue on their straight path ... except that they're bound not just by their gravity (like in a star system or a galaxy) but are also bound by the much stronger electromagnetic-forces. But the thing is they're still trying to fly away in straight paths despite being hold back by these forces. And having each particle of a symmetric object pull away at the same time straight-away from the axis of rotation makes that axis stable (though that axis isn't actual physical object - just the line of rotation stability). To be even more pedantic in order to change direction of that axis you have to introduce force in order to affect their momentum, but while Gravity pulls a spinning top directly down - ie on the same line as that axis it's not going to topple the top at least until it loses enough of its energy due to friction and air-resistance. I know that's super pedantic description, and a bit boring to read (for those that understand it), but I hope that it explains the gyroscopic effect to those that didn't know it. :)

[@zebt7477]

There is no such thing as centrifugal force it's a pseudo force. It is only real in a inertial reference frame. So it isn't real .

[@bharathcarrom2159]

I had tried a lot to understand what the Spin really was before this, but had a hard time. This video has taken me the closest towards understanding it. Thank you. Now I think I can move from this reference point.

[@jamesmckenzie4572]

I clicked on this randomly and I'm glad I did. You've finally explained electron spin in a way that I can understand and even believe. And with a sense of humour too. I've read about this stuff for a long time and yours is the first explanation that has worked for me. I think you are the first to take the time to not just skim over the peculiar details that need to be understood to make any sense of what spin is. Thank you, and I'm subscribing (and sharing) by virtue of this, the first of your videos that I have seen.

[@Mahesh_Shenoy]

That made my day. That's the exact response I was looking for while planning this video!

[@hakiza-technologyltd.8198]

You’re wrong www.dropbox.com/s/c69trrjillfr23r/HAKIZA-1%20%28draft%29%20-1.pdf?dl=0

[@monoamiga]

SAME HERE! I *FINALLY* understood it! Thanks man!

[@lastchance8142]

The thing about quantum mechanics is that we can't explain it from "first principles". Most of the properties and behaviors we observe are so counterintuitive that they are tantamount to magic! After 100 years, we can describe it well enough to predict results (probablistically), but can't explain "why". Two possibilities present themselves. Either we have reached the ground floor of knowledge and will never understand "why" these behaviors exist, or we have yet to discover something even more fundamental than QM, from which it emerges. Based on the history of all science, I expect the latter.

[@MrSpock-sm3dd]

his explanation is useless and very slow but im glad at least some people liked it

[@clintanderson4591]

Legit. Tons of other vids and classes here, yet you still taught me something new--without math and based on intuition. Grow your channel, dude. Standing behind you.

[@GuntherX57]

I'm a chemistry student, and this is a topic I struggle a LOT to understand (my teachers just say "it makes sense when you apply general relativity"). So it's refreshing to see videos like this. Good job!

[@bradwiley1882]

Badass. Nice work. I’ve studied chemistry and quantum mechanics for 45 years and appreciate your approach!

[@ignorasmus]

Think of electrons being politicians. They "Behave" as if they care about people, but really, they don't and they can't. 😂

[@Mahesh_Shenoy]

Woah! That sums things up very nicely!

[@eyewaves...]

Good one...prefer science of course...😂

[@laurie886]

Fantastic video . I'm a 66 year old man with no physics qualifications at all but I've been reading quantum physics for the past 5 years just as a (unwinding) after work sort of thing I'm hooked on it I just can't get enough and I think your videos are just great thank you ( by the way I find the Richard Feynman lectures volume 1 2 and 3 a great read )

[@Mahesh_Shenoy]

That’s so incredible, Laurie. Super encouraging!

[@laurie886]

Thanks for the reply I look forward to seeing the next video

[@ravikantpatil3398]

Very good

[@shubhamkumar-nw1ui]

Wow.thats inspiring

[@alexandrekassiantchouk1632]

Check Dr. Vivian Robinson video about electron is confined photon/standing electromagnetic wave (Dr. Williamson model of electron) - that explains/gives origin to spin, charge, inertia=mass.

[@draelyc]

I love the way you laid the whole matter out in the form of a "conversation with the master." Very helpful for folks like me, who love to follow the subject but who've got no formal training ... and CERTAINLY don't have the mathematical ability!!! ... to engage the material directly. Thank you!

[@adamlatour4011]

Great explanation, but I have to correct something: the individual particles in your basketball *are* spinning about their own centers as they move in a circular path around the center of the basketball. Here’s another way to think on it: someone standing on the equator will do a full flip head over heels over 24 hours. Someone standing on one of the polls will spin around once over 24 hours. Every point in a solid (rigid) spinning object has an angular velocity equal to the angular velocity of the object it belongs to. Put a coin on a spinning record, or a book on a spinning chair and watch it - it doesn’t “hold still” as it moves in a circular path, it spins too! At exactly the same angular velocity. While it’s hard to conceptually think of a true singular point (i.e., no consituent parts) spinning, explaining this by saying spin is an emergent property of a collection of non-spinning objects moving around a common axis is a bit wrong. A spinning object full of non-spinning consituents would experience a ton of tidal friction. But, the explanation of how we detect the spin of an electron by measuring it’s wobble in a magnetic field is great, so the lesson of the video is still mostly unchanged and really great.

[@CACBCCCU]

You should try to explain how a non-spinning electron can (or cannot) generate light that carries spinning field vectors (is circularly polarized). All light can be constructed with circularly polarized photons, so it's a critical concept.

[@AdamAlton]

This seems to me like a strong clue that electrons are in fact *not* fundamental particles and that there is something deeper yet to be discovered. Thanks for the excellent video.

no, even if the electron is not fundamental the momentum would be too high to be explained by anything happening inside of it.

[@DJVil777]

There is also another thing. If electron has a spin axis that going from this tube it would be deflected depending by the angle of the spin axis. In the experiment there is NO dependence. The electrons are eigher deflecting up or down. That is why the electron spin is not a spin. It is some fundumental property of it that cannot be understand by our intuition

[@AmericanDiscord]

@ Lots of theories posit composite electrons. I don't know why you think there is some rule about momentum that would prevent a composite electron. Your statement is self-contradictory, even if it is not composite it's momentum has to be related to whats is happening with the particle.

[@AmericanDiscord]

​@@DJVil777 Electrons can have arbitrarily oriented spin axis, so you are incorrect. That they align themselves in one of two ways in the presence of a magnetic field, has nothing to do with whether "a spin is a spin".

@@AmericanDiscord no, you just don’t understand me. This reason is not mine is the textbook reason, which you would know if you actually studied real physics.

[@JaredWyns]

Finally, an explanation that focuses on the nature of reality instead of trying to overly analogize it. Thanks!

[@mikegale9757]

Excellent presentation. As you say, the issue with electron spin is that the electron has no breadth or if it does, it looks the same from all angles so there's no sense in which it can spin. Black holes have the same problem, but they can have angular momentum, too. The upshot is, angular momentum is more fundamental than we have been led to believe. It is possible to have angular momentum even if you have no breadth or you are devoid of features. It will manifest when you interact with your environment. Photons are another case in point. Planck's constant is effectively a chunk of angular momentum.

[@aaattteeennn]

Such is the wonder of endlessly empty curving space!

[@user-mz4ck4qd8h]

Great video! Ever since high school, any time electron spin was brought up in class, it was always accompanied by the phrase, "the electrons aren't really spinning, but...". So, I asked nearly every chemistry professor that I've ever had what exactly electron spin is, and never got any answers. This has finally put those nagging questions to rest. Thanks!

[@Mahesh_Shenoy]

That was the whole intent, I am glad it helped!

[@tiborbogi7457]

@@Mahesh_Shenoy It would be nice, if there is a link to experiment, that proves electron wobble in magnetic field. Or at least write down name of experiment in description, please.

[@gibbogle]

I get the impression that many physics and chemistry professors don't actually know what electron spin is.

[@mohosinmahmud4238]

Thank you so much. I've been struggling to comprehend this for years. Your ability to explain complex topics in so simple manner is truly remarkable.

[@christophercalvin8174]

The way that you walk through the concepts helps me to understand, and your enthusiasm is infectious! Thanks so much for your work on these videos!

[@user-tt4jz3tm6t]

I love it when you finally hit on a video that explains clearly concepts you have been trying to understand for ages.

[@varsha_1703]

Mahesh we need QUANTUM MECHANICS from you ...more topics on QM please ❤🙏🛐

[@Mahesh_Shenoy]

Working on it.

[@user-vi1tw1xw7r]

This was nicely done. I still don't feel I really understand electron "spin", but now I know precisely what I don't understand 😂. (40 years in electronics too!)

[@user-lc8yc4cq5n]

Conclusion. Angular momentum can exist (arise?) without spinning. A nice concise video. I like it.

[@atrus3823]

Watched a few of your videos lately. You are really talented at explaining things: clear, methodical, enthusiastic in a genuine way, and most importantly, you lead logically from point to point guided by natural questions that would arise.

[@Frank-si2jd]

Incredibly well explained! Thanks for these nice physics tutorials, they are very understandable for “us” non physicists!

[@michaelwobrien]

Great video. You are a talented teacher. Your entertaining and engaging method of explaining complex topics is fantastic.

[@sjallard]

Guy, your videos are like the residual FAQ of every other physics video I've watched which didn't bother to explain either well enough or even at all this kind of fundamental topics. I'm binging against my will and available time, but no regrets. Thanks!

[@jdbrinton]

Your explanations are fantastic! You're teaching the part of the curriculum that's left out of the books, e.g. the "big takeaway". Thank you so much. Keep it up!

[@DurgeshSharma-oz2xb]

Nicely done. I am a hobby physics student at age 47. When I first started QM few years back electron spin bothered me but I was able to overcome that by reading a lot from various sources including Feynman lectures. You have explained this nicely in a short video. I believe there is more to fundamental particles. I have intuition that even electron and other particles have structure and study of which will reveal more. I m sure your videos will encourage more guys to take interest in quantum mechanics. As more people will take interest in physics more Einstiens and Feynmans world will produce. So please keep up the good work and keep these videos rolling out.

[@nohithair]

I really enjoyed listening to you! Thanks so much for sharing a small piece of your mind with me. You communicated an important concept extremely well. I count myself fortunate to have lucked into finding your video here, today. I will definitely subscribe for more! Best wishes! By the way, I think that the wonderful readability of the Feynman Lecture series had more to do with those who surrounded Feynman during its development than with Feynman himself. I've listened to his lectures, not just those in the US but also to many of those done in Australia, and I consider all of them to be rather 'difficult' to access, in the moment. I'm not the only one. Freeman Dyson had to take nearly a year off and drive around with Feynman to grasp his ideas well enough to codify them in terms others could more readily follow and accept. Feynman was clearly a radical at the time. My absolute favorite book about Feynman is "The Beat of a Different Drum" by Jagdish Mehra. I cannot recommend it enough.

[@MTWDD]

I love how you do your dialogues! It allows some pre-thinking and guessing, which makes it much more fun watching the video. Very creative!

[@yashbhat94]

Hi Mahesh, I love how you make all these concepts so accessible. Like I cannot state how simple your explanation is for me to understand (for twin paradox and other non intuitive concepts). I just wanted to mention that for a 3d body, spin is rotation around an axis (not a point) which passes through the body

[@NeedsEvidence]

Fantastically educational video! The electron behaves like it's a magnet (has a _magnetic moment_ ) and that it somehow "rotates" (has an _angular momentum_ we call _spin_ ) and that the _magnetic moment_ is proportional to the _angular momentum_ , as is the case with classical electrically charged bodies that rotate (as explained in the video). However, there is a fascinating difference between the classical rotation and the quantum spin: The ratio of the _magnetic moment_ and the _spin_ of the electron is TWICE the ratio of the _magnetic moment_ and the classical _angular momentum_ of the classical counterparts. Somehow, the quantum spin is TWICE as "powerful" as the classical rotation, as predicted by quantum mechanics and confirmed by experiments.

[@mrfranksan]

Somehow (and I’m not the slightest bit authoritative) I recall the “as if” concept of 720° arc per “revolution”; this could be garbled, irrelevant or both.

[@ianohlander]

This (and your others) is fantastic. You give good explanations without skipping steps. I watch a lot of.videos and sometimes its easy to.get lost in the weeds or get too HIGH of an overview. You have a great balance. Keep it up

[@Mahesh_Shenoy]

That’s exactly what I am trying to do. Thanks for pointing it out!!

[@ianohlander]

@Mahesh_Shenoy well you've got the balance down. I'd love to see you build up to a break down of the schrodinger equation and the Einstein field equations. I've studied enough that I think I get then (sort of high level, anyway.) But a good delving into tensors (and what the various tensors are- their indices) and operators and the fact that they are differential equations that spawn multiple solutions would be awesome. Professor Dave does pretty well with the schroedinger equation in his series but his explanations of solving them could use your touch. You have an engaging style that asks the questions we are thinking. During the video on deriving the maxwell equations or solving newton's problem in 2 minutes, you did that repeatedly and it helped. You approach from the students perspective- asking Feynman questions or challenging assumptions. Keep up the amazing work!! And whatever you do or don't do, thank you for what you've done.

[@mattp422]

What a beautiful explanation! As an academic radiologist, I have always found it difficult to explain why protons precess in the magnetic field of an MRI. That is, how to reconcile the Newtonian concept of angular momentum with the quantum mechanical theory? Thank you, thank you!

[@tonyt7804]

OMFG! Absolutely the best explanation I’ve heard! I’ve been spinning my wheels in vain trying to understand spin. I’m not technically trained or educated but have been interested conceptually for years. And I’ve read and viewed a lot over the years. Great, great explanation!!

[@susmitbhar9462]

Sir, you have probably one of the recent comments so pls could you clarify my doubt. If we can consider e- wobbling then that means it has an angular displacement and spin is also angular displacement over time so considering wobbling is kinda same as considering spin . So at the end we just thought in a loop and got satisfaction. If I am wrong pls pardon me and explain it would be great.Thank you

[@nd.c.1098]

Hey sir, you have a talented presentation/ tutoring skills, I work in field of medical physics, your explanations for terms are refreshing ! That makes me recalled the teaching of my old fashioned physics teacher, Thank you :)

[@fhamilton1]

Been self learning QM for some time and this is by far the best explanation of spin. Thanks.

[@phazix6529]

Been trying to intuitiveley understand quantum spin for over half a decade, this 15 minute video finally got it through to me, great channel and I love the way you explain things, coming from the perspective of the people testing the ideas at the time, 10/10 vid and channel!

[@praveenb9048]

I just found your channel and I am now bingeing on your excellent videos. I am sure many of us viewers would love to know more about your story -- how did you get started in science education, how did you join Khan academy, what inspired you when you were a kid?

[@Mahesh_Shenoy]

Will do it when I hit a milestone. Say 50k or something?

[@shivukumar2564]

KZbin algorithm has finally understood me.

[@josephbenjamin6426]

I literally subscribed after this…NO WHERE ELSE has been able to explain this!

[@prydin]

Where have you been all my life? When asked to explain what spin is, most physicists would just say “it’s complicated”, but you actually managed to make sense of it. I love the imaginary conversations with Feynman!

[@BloobleBonker]

We are tantalysingly close to understanding this but still it evades our grasp. Great video. The answer is just around the corner. It's a simple answer, surely.

[@Mahesh_Shenoy]

We do understand it. By using the language of math and quantum mechanics. But we will probably never understand it if we try to use English.

[@danielnigel6920]

@@Mahesh_Shenoyyou are obviously still young and full of yourself

[@aaronmicalowe]

​@@Mahesh_ShenoyI wouldn't trust math alone. Math allows many things to exist in theory that have and never will be observed, because they don't exist in reality. For example, white holes, Klein bottles, time travel, warp fields, negative energy, anti-gravity, etc. Saying quantum spin is not saying anything different than spin unless you define the difference. Quantum spin is still, "trust me bro" logic until it is observed and nothing in your video attempted to say what it is.

[@timothymatthews4399]

Thank you. That helped a lot to gain some insight on this mind boggling quantum property. I’ve never heard such a good explanation of this topic. It amazes me that those European physicists back in the 1920s could envision this stuff!!

[@nickush7512]

Dude, you are a much appreciated intermediary between the minds that sussed these thing out and mine, that loves this stuff... the hard stuff and the not so hard stuff ... You have a new subscriber, and thank you :)

[@CVBrennan]

I was feeling lost… but then your explanation hit me like a brick wall in a split second of understanding the analogy. 🤯 thank you for these videos.

[@jwestney2859]

For me, studying quantum physics was like a religious experience: it is beyond what the human mind can comprehend. So we use analogies and rules-of-thumb. This is as close as we can come to understanding. Listen to Mahesh enthusiasm as he experiences this religious experience! Fun video!

[@kingplunger6033]

weird comparison, but yeah. Our mind is limited and you don't have to go far at all to see that. just take 4d concepts

[@brucemacmillan9581]

You're talking a lot. But you're not saying anything.

[@rv706]

Quantum mechanics is not beyond human comprehension at all. The whole "if you think you understand QM then you don't understand QM" is just mythology nowadays.

[@RafaelB1717]

QM can be tested, religious stuff can't.

[@aliensarerealttsa6198]

This is pretty much what every expert does. They actually don't know and just make stuff up. And most are illiterates. "Antimatter" - some idiot

[@kvs79]

⁠@Mahesh_Shenoy Great video. Do you happen to have links to any talks/lectures where Feynman discusses spin? Or maybe the book(s) where he mentions this? I am curious now on his full reasoning for why electrons can not be spinning.

[@Mahesh_Shenoy]

Mostly picked from Feynman lectures. But, this is a widely accepted idea. I just elaborated it to bring out the nuances.

[@agolivei]

@@Mahesh_Shenoy Great! But could you please give a more specific reference? The Feynman Lectures are very extensive. Any volume and chapter? Thanks in advance.

[@jareksprysz]

That was simple, and therefore huge! Thank you, man. And I appreciate this enthusiasm of yours.

[@vishnuk8782]

My mind got blown after knowing the definition of spin and why electrons cannot spin.

[@dityaharpatipraja4442]

sir, in brief history of time, Stephen hawking writes that spin is actually the number of times you need to rotate a particle so that it has the same orientation as we started with. for example- if we take an arrow, we need to rotate it 2 times (at 180*) so that we get same orientation as we started with, thus it has a spin 2. Similarly a particle with spin 1 is like a double headed arrow. but electrons behave differently, we need to rotate them 2 times(at 360*) so that it looks the same and it has spin 1/2. how do I reconcile this with u said? your explanation makes more sense to me.

[@Mahesh_Shenoy]

Wait, don't you mean that the double headed arrow is spin 2, a vector gives spin 1 (the most intuitive one), and electrons do spin 1/2. All of that is true. But the key word is spin is 'like' spinning a particle... So, where as in the case of the arrows they are ACTUALLY spinning, in the case of the electrons, they are not. But they do have a property that very much resembles the classical spin -aka - the magnetic dipole moment and Larmour precession. It's not actually turning the particle in the classical sense. That's the whole message of the video.

[@DrDeuteron]

Wait, an arrow is spin one. A bar magnet has this symmetry. It needs 360. Linear polarized light intensity has spin 2 symmetry, so you wear polarized sunglasses upside down , 180, and they still work. Spin is 1/2 and is the fundamental spin able object, but it hard to visualize. Now I say spinable, bc spin 0, like a helium atom in the ground state, is perfectly spherical, and it cannot be rotated. A rotation is equal to doing nothing (multiplying by one, really).

[@jorgepeterbarton]

Another video explaining what not spinning but acting as if HALF spin really means. I imagine difference outcome of angular momentum and charge, like values that would be impossible for a classical object like a top or magnet, just different values but what does it really mean

[@fabriziosantin7420]

I like your videos and your way of talking/explaining. Keep It up! BTW, this video should be titled "the quantum duck" (or elephant)... "If It looks like a duck, It behaves like a duck, It quacks like a duck, it's NOT a duck, in QM"

[@Mahesh_Shenoy]

Lol! Good one!. Thanks :)

[@wolfgangschneider3743]

Thanks for the wonderful explanation 😀I've always tried to wrap my head around this ("yes it has spin, but it doesn't spin" etc.). Now it seems much more clear to me

[@HylanderSB]

I'd heard before that the spin is an expression of torque or something along those lines but this is by far a much more complete explanation. Thanks!

[@GodSahil]

I really liked your last lines that "we have no intuition for that quantum world" But it would be really great if we could go to the quantum world and maybe see the world with our own eyes 👀

[@aurelienyonrac]

I totally disagree. I think we can get intuition, Stick a belt in a book. Twist the belt once. Try to untwist it by passing the brlt under the book. It spins without spinning. Space time is spinning.😅 On an other note, It would be fun to imagine that all the electrons are actually one. Then it is just space time between each electron that is different.

[@GodSahil]

@@aurelienyonrac haha, very cool! But still, we can't explain every concept of quantum theory with our daily experiences.

[@l.h.308]

But alas, would we not collapse everything there by looking with our eyes?

[@EnjoyNature7]

Could you please mention the research paper on that experiment ?

[@Mahesh_Shenoy]

Check out, Larmour precession in electron spin resonance, and Stern-Gerlach experiments. I have oversimplified it.

[@MrClickity]

Your "if you can't convince them, confuse them" expression reminds me of something I've heard a lot as a repair technician: "if you can't dazzle them with brilliance, baffle them with bullshit"

[@jukesters123]

This youtuber is so addictive. I don't understand it all but i keep trying.

[@MrFeanor82]

You’re such an honest teacher, it truly blows me away. There is no ego whatsoever in the way you explain things to the layman. I hope you realize how good of a teacher you are!!

[@rodocar2736]

Electrons have angular momentum - quantized (Lz = +/-h/2) -, and yes, it is angular momentum of the same type as the angular momentum of the wheel of a spinning bicycle, and changing the orientation of the spin requires the same type of effort as turning the handlebars of the bicycle. It turns out that since they cannot explain the gyromagnetic ratio gs=2, then they say "it is not angular momentum"

[@Mahesh_Shenoy]

We do call it the spin angular momentum!

[@neverusingthisagain2]

Its not momentum because its not time deoendent. Its not time dependent because the coppenhagen interpretation is wrong

[@Shadislecrou]

​@@neverusingthisagain2How is it wrong and what is the correct interpretation?

[@danh5368]

@@neverusingthisagain2 stop making shit up. Leave interpretation to the experts because you clear have no idea what you’re talking about.

[@nsacockroach4099]

​@@neverusingthisagain2 What do the interpretations of QM have to do with that? This topic is not related to the measurement problem.

[@adhenaninghreez-ns8lz]

I think that you have the ability to excellently explain meanings, clarify things and expose their taste and beauty. I appreciate life now that it gave birth to some one like you and like Feynman !❤😊🌹

[@owlredshift]

Bravo!

[@Mahesh_Shenoy]

Thanks 🙏

[@zepplondon]

After watching several of your videos I grew to need them as much as your microphone needs a pop filter

[@d3vilman69]

I think it will be an honor to be able to participate as an audience in Richard Feynman's lectures. I am not fully convinced that electrons are fundamental particles. Look at what we thought about atoms decades ago. Just because we couldn't detect the true stuff that make up electrons because of limitations of current technology, doesn't imply they don't exist. You have ability of putting forth complex scientific concepts, then break them down to bite-size chunks so normal folks like us could at least attempt to understand. Thank you.

[@prasundasgupta1820]

Very nice for a physics hobbiest like me...how simply you explained physics...good to connect 👍

[@rararnanan7244]

A very nice presentation of the topic. Well done! From here, when we look at how much angular momentuum the electron has it gets even wilder. Electrons have spin 1/2 (in Planck constant units). A particle with spin 1 has a symmetry of 1 - that means that if you rotate "it" (meaning its wave function) a full circle it returns to the original state. A particle with spin 2 means that the wave function looks like itself twice in a full turn (think of a rod). A particle with spin 3 repeats itself 3 times in a full turn (e.g., a perfect triangle). This means that in order for the electron with spin 1/2 to return to its original state you have to turn it TWO full circles... this one fried my brain. 😵‍💫

[@shreyash3903]

Mahesh craking social cues and debunking pseudoscience with science

[@Mahesh_Shenoy]

Haha!! Always!

[@tomasmach2272]

How is it possible that I haven't discovered your channel before?! This is so awesome. I finally understood spin. Thank you so much. Keep it going

[@Mahesh_Shenoy]

Welcome to the tribe :)!

[@mthonyamampetsheni3420]

I just finished watching your video on JJ Thompson & Ernest Rutherford, I loved it. This is another hit explainer. They the best thing to do with knowledge is to pass it on, so thank you. Keep giving us more!!

[@GodSahil]

3:10 But what if we found out the electron is still made up of smaller particles in the future. 😂

[@Mahesh_Shenoy]

Great question, I actually edited this out to reduce the length :D. Anyways, that's the besides the point! We BELIEVE that electrons are fundamental particles. So everything else we believe should be consistent with this belief. That's why we can't also BELIEVE that electrons are spinning like a table top. Fun fact: We did try to figure out how big the electron needs to be for it to spin like a top and produce the magnetic field it does. The size came out to be larger than the atom itself!

[@GodSahil]

​@@Mahesh_Shenoynice fact ✌

[@harleyquinn8202]

@@Mahesh_Shenoy Electron is perturbation of a quantum electromagnetic field - a king of wave that spreads beyond the atom it is in. Why that perturbation cannot behave like a tiny cyclone in that quantum field?

[@TankEsq]

​@@harleyquinn820210:55 angular momentum experiments would probably have different results if that was the case

[@alanjones4358]

Great video. Another interesting observation is that the electric charge of an electron is 3 times the smallest unit of charge found in nature (charge equal to 3 down quarks). That, combined with their observed angular momentum and magnetic field, is pretty compelling evidence that electrons may consist of more elementary particles not yet observed.

[@ManuelGarcia-ww7gj]

While I was in college, I complained about not understanding quantum mechanics. One of the TAs responded, "Don't worry. No one understands quantum mechanics. We just get used to it.

[@PAULHODARA]

You explained well in simple terms a very complex unintuitive concept, I loved your story-tellling approach. Wonderful!

[@bigrich6750]

Spin is what Joe Biden’s press secretary does at a news conference

[@Mahesh_Shenoy]

Hahahaha

[@JayFortran]

ANY press secretary

[@peterb2272]

Came here for the science. Downvote.

[@RoboticusMusic]

Bro, this explained nothing, wth

[@randomshorts-ks7dw]

Same

[@danyyer4031]

TLDR of the Video. We call it spin because it behaves like a spinning ball. But it isn't a ball, and it doesn't spin in the litral sense.

[@das_it_mane]

Fantastic explanation. I've watched a ton of videos on this topic and each one fills in little puzzle pieces. This was great.

[@mansoorsiddiqui7396]

Mahesh Kudos. Your episodes are really inciteful and just top of the line!!! Keep them coming...😊😊😊

[@edwardmacgregor1233]

Your cogent and enthusiastic explanation brings joy to my heart and even a bit of understanding to my brain. Thank you!

[@rameetsingh6828]

After watching hundreds of videos on spin this is the first video that really explained what spin really is . Thank you kind sir you are a genius

[@barmalini]

Even more perplexing for me is to imagine a particle that consists of no other particle and yet is greater than a zero point. I mean, how can something that has size not be divisible? You see the left side of it, you see the right side of it, obviously you see something in the middle, but no, it's fundamentally not divisible? If it has size, it must have surface, and it must have inner volume, right? And there must be something that limits that particle in size. A truly uniform non-zero particle can only be of the size of the entire Universe - because its boundaries are not distinguishable from its inner volume. Which gently brings us to another concept by John Wheeler: a one-electron Universe postulate. Thank you for the great video.

[@Raven319s]

Whoa… fantastic explanation. I always just wrote off electron spin as a fundamental property of electron that I just had to accept. I knew it wasn’t like a baseball spinning but couldn’t imagine beyond that. The function of resisting an external magnet makes sense. I’m going to save this video so I can rewatch it many times.

[@ryhanatasnim2107]

Hey, I just found your videos today and I'm already a huge fan. The way you explain the most complicated things (at least to me) is astonishing really. I wish I had found your videos when I was a freshman in uni. Anyway, could you make a video on what does the values of spin mean? Like why do we say some particles have half integral values and some have integral values. What does it actually mean?

[@Camptonweat]

It refers to the degree of rotational symmetry of the wavefunction. For example a wavefunction that is the same when rotated 360 degrees has spin 1. A wavefunction that is the same when rotated 180 degrees has spin 2, etc. The fractional spin comes from an idiosyncrasy relating to the wavefunction object (called a spinor) that inverts itself under a 360 degree rotation, hence you need two rotations (720 degrees) for the wavefunction to revert to its original form. This sounds counter-intuitive, until you recall that we don't observe wavefunctions directly, we observe probabilities which *do* obey 360 degree rotational symmetry. A good analogy, if you are familiar with optics, is the two-fold degeneracy that arises in the rotation angle of polarisation. We use a construction called a Poincare sphere, where rotations in real space are doubled in the "Poincare space" (i.e. a 90 degree rotation in real space corresponds to a 180 degree rotation in Poincare space). With spinors it is similar, except the angle is halved rather than doubled compared to real space. Of course this begs the question *why* spinors behave like that, and why spinors are an appropriate representation of a fermion - to answer that you need to look deeply into the algebra of the Dirac equation, which is itself a tremendously rich and fascinating topic.

This fellow has a gift for explaining this science.

[@bendybruce]

I've searched high and low for an explanation of quantum spin that actually made sense to me. This is honestly as close as I have found in as much as it at least clearly explains the logic as to why we say an indivisible particle has the property of spin. Thanks.

[@FrancisFjordCupola]

From the opening 25 seconds alone, I know I will give the video thumbs-up. Whether it is left-thumb or right-thumb is kinda in superposition, always forget which one.

[@therealDannyVasquez]

KZbin recommended this video and I'm glad it did. You're an excellent communicator and teacher. Thanks so much. A very happy new Subscriber

[@phillair3813]

Thank you. I was a pretty good chemistry student and always just had the notion of ordinary spin. Nice explanation.

[@srinivasvellore447]

Kudos to the presenter for simplified explanation 👏. Ver knowledgeable presenter.👍

[@JohnHowshall]

You are the best teacher in quantum physics I’ve ever heard! Thank you!

[@omgtkseth]

Cool explanation. I was more satisfied with this than with the SpaceTime video. Their video talked about the same experiment and I honestly did not understand it as well as I did with your spinning top analogy which was reiterated throughout the section. Then, their video goes into more topics that just make me have more questions because there's terms of behaviors I don't get and by the end of the video I felt lost, like I missed something. So this is really good.

[@joegillian314]

I've come to think of quantum spin as a form of intrinsic angular momentum. Hardly anyone ever bothers to mention this when introducing the concept of quantum spin. They usually just go on and on about how we call it "spin" but nothing is actually spinning. Although the exact nature of the quantum spin property still eludes us, I don't have a problem with saying that quantum objects have intrinsic momentum. Some day we will learn how this intrinsic momentum arises, but for now we just accept that there is intrinsic momentum verified experimentally. I enjoy Mahesh's style of teaching very much, and I have a similar philosophy myself when it comes to my own students.