This experiment confirmed quantum physics

[@bbonagura9]

This channel is a gem

[@Coolmd-it4ck]

By far the best video in the history of pedagogical introduction to the Stern-Gerlach experiment!

[@jkzero]

thanks, the aftermath of the experiment deserves its own video, coming soon

[@ruby_linaris]

@@jkzero just find the original photo from this experiment. Reality is very different from pictures.

[@supreetsahu1964]

​@@jkzero🫡🫡🫡

[@uploadJ]

@@ruby_linaris I have not viewed Dr. Diaz video here yet, but, has anyone in recent contemporary times replicated the Stern-Gerlach experiment?

[@ruby_linaris]

@@uploadJ apparently, yes, it is impossible to get a similar result, it is necessary to separate spin-oriented molecules from the standard non-oriented flow.

[@thesouledguitarist7144]

Hi, I would just really like to appreciate the insane amount of research that would go into creating these lectures. Thanks a lot for making these, they really help in understanding the real pedagogical value of learning the history through thought experiments and laboratory experimental marvels.

[@jkzero]

Thank you so much for you comment. It really means a lot when viewers appreciate the amount of effort that goes into creating this content, from researching the old papers, finding them, translating many of them, creating the script to transform a series of facts into an interesting but factual story, and production. I am not the best when it comes to animations and graphics, but I hope they are good enough to support the story.

[@NoahFect]

@@jkzero What I really appreciated were the photos. The one with Stern peering into an observing instrument while holding a cigar should be a cliché by now, given how nicely it evokes the serendipitous nature of so many historical experiments. But I'd never run across it anywhere. Same for the fascinating back story with Goldman's contribution. Thanks for your work on the video and the fresh perspective you brought to the subject!

[@ivolol]

I wonder if there would be enough anecdotes to make a behind the scenes video at some point. Any interesting facts you discovered while researching all this material. In fact, your videos, uniquely, give me a subtle urge to go read the original papers and discover what the horse's mouth was actually saying, although unfortunately it seems quite a few are in German which I do not know.

[@jkzero]

@@ivolol sometimes I leave content out of the final video for time reasons or because it takes me through a long tangent, maybe one day I will collect them all and release them. Old physics papers are not easy to read, the notation is confusing, most don't include units for physical quantities, and a significant fraction are published in German. I use online tools to translate. Although I am studying German, reading these papers is quite hard.

[@will2rein]

This has happened so many times: physicists develop a mathematical formalism to described some physical phenomenon, but they have a hard time accepting the full consequences of that formalism and tend to mistake them for mathematical artifacts. It would deserve an epistemological rumination. Awesome video. Subscribed.

[@nicholasandrzejkiewicz]

Physicists still say this about gauge theory!

[@rippedtorn2310]

Top Marks for the phrase ''epistemological rumination'' .

[@jkzero]

I am glad you liked the video and welcome to the channel.

[@reluginbuhl]

I really like your videos. It's so nice that you don't shy away from the math and go into the theoretical details enough so that I have some idea about what is really going on! Thank you.

[@jkzero]

Glad you enjoy it. I feel the same with an audience that doesn't shy away from some math. It is just great having viewers that value the sprinkle of math that I include. I really don't want to turn these videos into lectures, but also I was tired of superficial stories and analogies, I hope that there was an audience that wanted to be challenged in order to follow the concepts more deeply.

[@wafikiri_]

​@@jkzeroFortunate of us! How often I've been frustrated by those articles in scientific divulgative articles because they used analogies instead of maths!

[@jkzero]

@@wafikiri_ analogies are great but they are also limited and can lead to misunderstanding when taken beyond their validity. Math leaves no room for misunderstanding.

[@islandfireballkill]

​@jkzero Sometimes, people forget that the best, clearest, most enlightening description for something is not an analogy, but a cold hard equation.

[@ffs55]

This is an amazing video and made my week! I have been pining for a followup to the Sommerfeld video -- which is also AMAZING. It makes a huge huge difference that you teach through the eyes of the pioneering scientists rather than backward through the lens of what we know today. This allows the concepts and teaching to flow naturally when it is otherwise so easy to become lost in mathematical symbology, methods, and topology.

[@jkzero]

Wonderful! I am glad people enjoy the content, I personally have a blast creating it. I have got to read many of the original papers that this series has become also a journey of discovery for me too. Most of these things are never mentioned in classes but I personally believe that many of the misunderstanding on quantum mechanics or conceptual holes arise because people jump directly to modern quantum mechanics and its ad-hoc postulates without studying the early developments. Even though the old quantum physics was rapidly replaced by quantum mechanics, it is the old quantum physics that led to the conceptual jump of Heisenberg, Born, Schrödinger, Pauli, and the others.

[@m1323fj]

This is one of the best history of science videos I have ever seen. I am a science professor, and I know how difficult it is to convey a concept this complicated and nuanced with such clarity and context. It is a tour de force. Excellent work.

[@jkzero]

Thanks so much, I am glad you liked it. Is that "tour de force" line a reference to Wolfgang Pauli?

[@jeffwads]

It is a crime that your channel has just 34K subs. These videos are priceless.

[@ft7339]

@jeffwads You are completely right.. But please think, when you are interested in Physics, Astromomy, Maths, Philosophy, Archeologie, Nutrition, preventive Medecine, History, Geography, Chess, Bridge, etc., how many channels you would subscribe? And, subscribing is not the problem, you must also find the time to watch them! I tried to find an Earth 2.0 with 48 hours a day, but was unsuccessful! 😀

[@copywright5635]

I appreciate the historical approach. I remember reading Feynman Lectures Vol III and him referencing that the Stern-Gerlach Experiment was different to the example he provided. A lot of resources seem to use that same altered Stern-Gerlach experiment that Feynman showed, so it's interested to see the exact experiment that it was originally

[@jkzero]

Yes, SG is briefly introduced just to go over the quantum postulates and show experimental evidence for the uncertainty principle. This is a logical teaching approach, but I personally find it unsatisfactory. Most textbooks treat SG has a result, I am also interested in the experiment and the motivations. I think it reveals what people were thinking back then, I want to know how all this was discovered instead of just 'shut up and calculate'

[@DynestiGTI]

Learning about the history behind the derivation of the quantum numbers, equations, the Stern Gerlach experiment, all the physicists behind it, and all the small mistakes they made and wrong ideas, gives you so much more motivation to learn rather than just learning from a book with all the correct equations and theories given to you. Also love how you add historical context, makes an otherwise purely physics education video feel like an engaging story. Love this part 25:31 too, one of the most important qualities of a great scientist. P.S. can you please add this video to your QM playlist 🙏

[@EricaCalman]

So TLDW (although the whole video is very worth watching) they were trying to measure if orbital angular momentum was really quantized or not by passing atoms in different Lz states through a field gradient, and only later was it tried with electrons on their own to verify it worked with Sz too. I actually never knew that, cool!

[@jkzero]

Thanks for your summary. I am with you, the story behind this experiment is really interesting and quite forgotten because the concept of "space quantization" was rediscovered in a different manner when solving Schrödinger's equation for the hydrogen atom, where the azimuthal and magnetic quantum numbers reappear as the indices of spherical harmonics.

​@jkzero They were trying to measure the orbital angular momentum, but they actually measured the spin of the unpaired electron in the silver atom. Bohr predict the split of the beam in two, but he had the wrong reasons. If they were measuring orbital angular momentum as bohr suggested, the result would be different. I really really loved the video, but I think you could have mentioned how lucky bohr was at the end :)

[@jkzero]

Thanks, you hava good point. I made a full video covering the lucky and fortuitous reasons that this experiment worked at all kzbin.info/www/bejne/lWHdiWuqgZKFl80

[@rbarberac]

Another key experiment on its historical context. Thanks for this series. It’s wonderful.

[@jkzero]

Glad you enjoy it!

[@АлексейИлларионов-ш5о]

OH, MAN! What a great goal of the video! What a instructive and inspirational story behind it! (it's a great loss that it wasn't told earlier). Not a single unnecessary word! This is what is absolutely necessary for studying physics!!! By the way it's a great scenario, pictures, design and the voice acting! What a great work you've done!!! It's amazing. Hope, it brought pleasure to you and work will be fairly appreciated 🔥🔥🔥

[@jkzero]

thanks, I am so delighted that viewers enjoy the content as much as I enjoy making it

[@MathsSciencePhilosophy]

The best part about your video is that you include mathematics in it and you explain the history behind the discoveries (which is useful to know how scientists thought about making that discovery).

[@jkzero]

I personally believe that many of the misunderstanding on quantum mechanics or conceptual holes arise because people jump directly to modern quantum mechanics and its ad-hoc postulates without studying the early developments. Even though the old quantum physics was rapidly replaced by quantum mechanics, it is the old quantum physics that led to the conceptual developments by Heisenberg, Born, Schrödinger, Pauli, and the others. Here I attempt to share these unfairly forgotten early times of quantum physics.

[@markborz7000]

Phantastic lecture! This lecture should be standard for physics students. Wish, it existed in my student time.

[@johnwillson]

Love it when the desktop thought and the mathematics predicts, confirms, or rejects ā priōrī before a physical result/experiment. Great presentation and explanation of quality science.

[@HugoBossFC]

This channel will blow up eventually. And it’s much deserved!

[@jkzero]

I appreciate that, thanks

[@JacksonRiddle90]

i always greatly appreciate your videos! as a physics student these are always my favorite things to learn about. Not only do i learn about the concepts more, i learn the history of it too. thank you!

[@James-ll3jb]

@@JacksonRiddle90 You're all being misled

[@luudest]

Breathtaking video (really)! You are a great story teller. I finally understood the Stern Gerlach Experiment. Thank you very much!

[@jkzero]

Great to read that the experiment is now clear for you. Thanks for your comments, I am glad you like the content.

[@SmallPharm]

Great video! Criminally underrated channel, KZbin algorithms should be ashamed for not recommending your channel frequently(((

[@jkzero]

I appreciate this, but I cannot complain, I am very happy with how much the channel has grown in just one year.

[@krwada]

A great video! Many years ago, as an undergraduate at university, I remember attending lectures on introductory quantum mechanics. The very first thing we were lectured on was the Stern Gerlach experiment. This video does a very good job explaining the importance of the finding and very clearly shows how the integral quantum numbers are manifest in an experiment which shows that there are indeed very well defined quantum states.

[@davidcarr2216]

This is another lovely explanation of a groundbreaking experiment in context. I thought it was going to give me some insight into electron spin, but alas. Well, maybe a little bit.

[@jkzero]

the aftermath of the experiment deserves its own video, coming soon

[@heribertovasquez5945]

The math, physics and history combined together make it all so stunningly captivating. I love that you never shy away from any mathematical derivations, and never shy away from any historical context and linear storytelling. More please! I feel like I see Griffith's Intro to QM book with so much vibrancy and color (so to speak) now with all of this context!

[@jkzero]

Thanks so much for your generous support. I am so delighted that viewers enjoy the content as much as I enjoy making it.

[@spencerwenzel7381]

This is an absolute treat. This is definitely a topic I want to know more about. I haven't watched the video yet but I know you will do it more justice than any other physics youtube channel out there, and that is taking nothing away from them.

[@erenerdem4657]

Keep it up man.

[@abhijithcpreej]

Your videos are becoming more and more consistently captivating! Another amazing video!

[@jkzero]

Thanks for the feedback, I am glad the interest keeps growing. I write and rewrite the stories more than I should, but it takes a lot of my time so I am happy that the result is appreciated.

[@ahmadtabikh5533]

Wow, this video was absolutely incredible! The way you presented the content was both captivating and insightful-definitely one of the best I've seen in a while. Your dedication and creativity really shine through, and it’s clear how much effort you put into making this. I’m definitely looking forward to more amazing content. Keep up the fantastic work!

[@456dave7]

Excellent video, please continue your work

[@jkzero]

That's the plan!

[@sphakamisozondi]

Dr., I'm not a physics major, but your videos have made me love physics experimentation and result interpretation

[@jkzero]

Thanks fro this, it really means a lot. I am glad that you like the content and that it can sparkle interest in physics.

[@WD_GX]

Finally, i've been waiting for this video!!!

[@jkzero]

I hope the wait was worth it.

[@WD_GX]

@@jkzero it was worth it and I can't wait to watch your next video, you're one of the best channels in youtube

[@kfawell]

As always your videos fill in and expand and illuminate the explanations I have learned before. What a great history and presentation!

[@jkzero]

Glad you enjoyed it

[@cjhtas]

Thank you for the trouble you take to make these interesting videos. My maths isn't up to higher level, but I understand enough to follow along. Having the pictures and stories of the scientists helps to bring the physics alive. I'm enjoying your channel.

[@jkzero]

Thanks, it is not trouble at all, I really enjoy creating this content

[@jamescarnevale3312]

Outstanding example of the scientific method accepting truth over opinion. The world needs more such dicipline.

[@ArduinoHocam]

I just found my self in the chat gpt and was asking the same question like what was measured with the stern-gerlach experiment and how it is called as spin when there was no term like this. This is the best video I have ever seen so far in the youtube that explains this experiment. Thanks!

[@jkzero]

Thanks, I am glad you liked it

[@Schraiber]

Fantastic video! I love seeing the actual context of this stuff. I hope you'll go through the history of how exactly people came to regard this as needing to be an intrinsic angular momentum of the electron rather than the quantized angular momentum of the orbit. Also wild that what again sounds like a really dumb quantization argument basically led to spin, which if my understanding is correct is a fundamentally relativistic, field theoretic concept

[@jkzero]

I am glad you liked it. The aftermath of the experiment deserves its own video, coming soon. Spin came much later, first introduced by hand into Schrödinger's equation, but later rediscovered as a relativistic term hidden in Dirac's equation.

[@5eurosenelsuelo]

Thank you for another great video. Seeing how these discoveries and conclusions were made in their historical context is way more interesting and often illustrating than a plain textbook throwing irrefutable facts at you. The experimental tests proving them right is what transform those statements into facts and not the other way around.

[@solitonacademy]

Great work Dr. Jorge, I wish he was educator at an university. University is limited Dr. JORGE is getting more Dr. JORGE day by day. Historical accounts , so mesmerizing! Accuracy and the simplicity. The voice!

[@redsky1433]

This is a clear explanation of the experiment and its results. I also enjoyed your account of the 'back and forth' between the scientists and the various experimental difficulties which are usually left out of the textbooks.

[@jkzero]

Thanks, I am glad you liked it. My videos are intended as a lecture but rather a fun mini documentary so I take the liberty to include the spicy backstories that I would share with my students.

[@physicsbutawesome]

Very useful discussion of the experiment and finally putting it in its right context! Most descriptions in physics textbooks are too much of fittting a narrative post-hoc...

[@moeboe6293]

These videos are simply amazing.

[@jkzero]

Glad you like them!

[@dominicestebanrice7460]

Fantastic content. Thank you! At 23'23", on hearing about the (initially inconclusive) results, Peter Debye seemingly prefigured Tucker Carlson......"only silly people would actually take what I say/write literally". I watched several times but keep losing the thread near the end: the two images presented around 25'10" were created during Gerlach's solo effort on the night of Feb 7 1922, right? The first image showing the "magnet off" distribution (that looks just like the earlier "failed" experiment when Stern was participating directly) and the 2nd image showing the famous split-distribution. If that's the case, this story is a testament to Gerlach's tenacity: he didn't "give up" when the earlier observations didn't confirm the hypothesis but kept persevering: the issue for me is that there is no mention of the improvements Gerlach made to the apparatus to eventually achieve his success. Gerlach's tenacity is admirable but I wonder to what extent the experiment's destiny was imbued with the odor-of-sanctity having received funding from Born, Einstein, Goldman and Messer and following the cultural demoralization that shattered science, culture and the arts in the aftermath of the horrors of WW1? Anyway, thanks again for such great content.

[@peacekeeper9687]

Your videos are really educational 🙌

[@jkzero]

Glad you think so!

[@joshdanziger8367]

I've loved this series, particularly the way it follows the actual history of ideas, with experiments interpreted in the light of what was then understood rather than what came later. And also that you don't shy away from maths including calculus. I do hope you're going to carry on and show those of us with some maths but no quantum mechanics how Bohr's model later gave rise to the work of Schrödinger and Heisenberg....

[@NemosYouTube]

Sir, you have done it again. You have filled a very important gap in my understanding from a second year undergraduate modern physics class. Back then, the professor teaching the class used Feynman’s lectures as the text book - a very poor choice - which of course introduced the SG experiment to explain quantum spin. There was no historical context, and the ideas of the apparatus and the rotated modules seemed to come out of nowhere. Furthermore, you’ve pointed out a very important controversy that i never appreciated - the resistance to quantization of space, by Max Born no less! That really shows how perplexing those early days of QM must have been to all scientists of the time, and it is a bit comforting to know this since quantum numbers, which for me first showed up in a high school chemistry class seemed to make no sense. Again, my sincerest thank you for your wonderful videos. The history behind these famous experiments is fascinating, and the turmoil of WW1 and the resulting German economic crash was a very interesting backdrop. You should really consider writing a better modern physics textbook that includes all of these little historical dramas. Truly, my upbringing in high school chemistry all the way up to 3rd year undergraduate physics now makes much more sense and holds together!

[@tahititoutou3802]

Very good and simple explanation of a subtle but decisive experiment.

[@OwenEkblad]

So cool, great video. Glued til the end.

[@jkzero]

Glad you liked it!

I wanted to see in the end of video you explaining how Bohr was right for the wrong reasons (they measured spin instead of orbital ang momentum, which they were trying to). The maths in the video were amazing, and reflect the historical reasons, but do not reflect what we understand as the cause of the split today. So the connection that we normally do today of this experiment and the spin, mentioned in the beggining, is not explained. I really really like your videos, so I hope we can have a second part to connect all the dots!! :)

[@jkzero]

You are right, and that was there but video would have been 20 min longer and a pain to edit and produce so what you are asking for is coming in a follow-up video.

@@jkzero I am really glad to know this :)

[@valentinmalinov8424]

You are too enthusiastic and thirsty for knowledge that I cannot resist to help you. Quantum mechanics is amazing, but it is incomplete, because it was stop in completion by TR. TR postulate impossible fundamental structure of the Universe and this made incredible damage to completion of QM. That's why to present day science do not know what Space is, Time, Gravity, Energy, Field, Electromagnetism. Polarity, Attraction... There is a explanation which you are looking for in the book - "Theory of Everything in Physics and The Universe"

[@gregorypirog6134]

At 24:00 min. Gerlach performs the test again (without Stern) and all of a sudden, the silver plate shows the split in the line. Why? What did Gerlach change/ fix 🤔? Gregory/ The Pigeon Meister ... . 🐦‍⬛

[@AmericanDiscord]

​@@gregorypirog6134One of the more interesting questions. Video misses a lot.

[@germalganis]

Amazing video!!!

[@jkzero]

Glad you liked it!!

[@mixolydian2010]

Wonderful story and experiment. Thanks a lot. All the best.

[@kalaidoscopez5388]

You deserve some serious love, respect and monetary compensation for these incredible videos. I shall help you when I am financially able in a few years! Thank you very much!

[@jkzero]

Wow, thank you so much. Keep me posted your future endeavors to remind you of this message :) In the meantime, I keep waiting for Goldman Sachs to reach out.

[@jimparsons6803]

Interesting and thanks for the explanation of how the experiment was performed. Back in my undergraduate days, my second year Physics Prof mentioned this effect in passing. It was part of a presentation about about some of the early accomplishments that lead up to the invention of the cyclotron and the atomic bomb. Liked the fact that the vector analysis was a pivotal point in this history. If I am not mistaken, the image describes a vector cross product and the equation displayed was a dot product?

[@Higgsinophysics]

RIP everyone who tried to prove Bohr wrong :D ! Loved all the historical details

[@sreerampp8839]

a small correction at 10:12 , for alpha equals 180 degrees, the direction of the orbit, should be opposite to what is shown.

[@jkzero]

You are right, I used the wrong orbit, my mistake. Later I used levels of transparency to make clear which side of the orbit was on which side of the X axis. Thanks for pointing this out.

[@tonibat59]

Amazing experiment and very good, detailed video. The reason why they failed to see a result initially is not clear to me. Were there too few atoms generated?

[@jkzero]

yes, to few atoms. The low intensity of the beam was great to avoid false signals but it required long time to collect enough atoms to be visible on the glass plate. The experiment was very unstable so keeping it properly running for many hours was a great challenge.

[@michaelblankenau6598]

Very interesting. You are able to present difficult concepts so that even the lay person has a chance to understand them . Very impressive work .

I love this video, on an experiment whose importance has few parallels. The motivation that drove the experiment, collaboration of the physicists involved, some of the details presented on the science, it was all new to me, and fascinating. I was even somehow excited as I read how the experiment progressed, in fits and starts!

[@jkzero]

I am glad you liked it. The aftermath of this experiment deserves its own video, coming soon.

[@068LAICEPS]

This is better than a movie about Atomic Bomb

[@AndriusKamarauskas]

I recommend watching Fat Man and Little Boy (1989) on the same topic but pointing out different aspects

[@John-bq1lp]

Just discovered your channel, fantastic work!

[@jkzero]

Awesome, thank you! I am glad you liked the video. I am always curious to know what brings viewers to the channel, were you searching for something in particular or did the 'mighty algorithm' find you?

[@John-bq1lp]

@@jkzero Saw it recommended after watching the video "What is the Schrödinger Equation? A basic introduction to Quantum Mechanics" by the Physics Explained channel

[@jkzero]

@@John-bq1lp Thanks for sharing and I am glad the algorithm is working, I hope you find the other videos of interest too and welcome to the channel. In case you haven't, make sure to check the currently running series on quantum physics kzbin.info/aero/PL_UV-wQj1lvVxch-RPQIUOHX88eeNGzVH

[@alucs6362]

This is beautiful history of physics work, amazing stuff! To my mind, it is also a great demonstration of how critical it is to take theories seriously and see them in a realist light (rather than only instrumentally) - not only for theoretical work but also for experimentation. Knowing how to recognize which parts of a theory are mathematical surplus and which are to be taken seriously seems to me to be one of the most crucial skills for the development and evolution of science.

[@jkzero]

Glad you enjoyed it!

[@nikhilsen9007]

Another great video. Finally I found a teacher you doesn't assume that details of experiments are trivial. In a standard textbooo, physics always seem like playground of theoreticians and experimentalists just play the followup game but as many people who have done experimental physics can tell that experimental physicists think by hand as well as brain. On a side note, I believe that the brilliance of experimental physicist in early 20th century is very hard to repeat again. In my opinion the main reason can be assigned to lack of opportunities to design and build experiments from scratch or close to scratch. With advent of modern technology ecosystem it is easy to buy off the shelf components from market whereas in the earlier ear people had to design and build experiments almost from scratch. I believe that just designing and building experiments from scratch can help juggle with so many creative ideas that can not be easily replicated by simply ordering cool gadgets from Thorlabs or oxford instruments.

[@jkzero]

This period of trying new ideas and experimenting to find unexpected results is what made me fall in love with physics as a kid.

[@djmips]

This is a very moving video. Thanks. Well done. 👏

[@jkzero]

Glad you enjoyed it!

[@robertroy1878]

That was impressive. Fascinating and very well presented.

[@jkzero]

Thanks, I am glad you liked it, make sure to check the follow-up video explaining the many lucky coincidences that helped Stern and Gerlach kzbin.info/www/bejne/lWHdiWuqgZKFl80

[@_joac]

Thanks for the content, very good resource for self-learners and frustrated physicists

[@narayanganesan1048]

Great video and history behind the Stern-Gerlach experiment! While setting out to detect angular momentum, they stumbled upon the spin of the unpaired electron in the silver atoms. I think the video could have provided the last extra bit of information and thus making it complete for those who are still assuming it was about angular momentum quantization.

[@jkzero]

I fully agree but it made the video over 50-min long; a follow-up with all the explanations is coming in the next video.

[@janbeck8269]

By far the best treatise on this important experiment I have seen. When I was a student, I really struggled with finding out why the magnetic field had to be nonuniform. Wish I had this video decades ago 😅

[@jkzero]

Thanks, I am glad it was helpful

[@catoleg]

Such a great content! Thank you sir for your work, it was very interesting to discover the history behind this experiment.

[@jkzero]

Glad you enjoyed it!

[@JumpingCow]

Very interesting. So when was spin first experimentally detected? And were Stern and Gerlach involved as we have been taught?

[@jkzero]

technically, spin was first experimentally detected by Stern and Gerlach with this experiment, they (and nobody else) just didn't know it. Everyone explained the result using the "space quantization" of the Sommerfeld-Debye theory but in reality a collection of coincidences didn't let spin to be discovered immediately. In a future video about spin and I will clarify this point.

[@Great_Beholder_Brooke]

An incredible video, lovely explanations and visualisations, and I never knew that's what the Stern-Gerlach experiment was originally designed for! Out of curiosity, does anyone know why the spin of the electrons don't cause more beam splitting? Intuitively I'd have though that the spin of the electrons would also interact with the external magnetic field and cause more beam splitting, but clearly that didn't happen since there's only two beams in the end. Anyone have any ideas?

[@jkzero]

Glad you enjoyed it! You are not alone, like most people, I was taught that Stern-Gerlachand spin come together but they don't. I hope I got the record straight. You have a fantastic question. I wondered the same and spent several days researching this. The answer is a lucky coincidence in which terms cancel each other out. In fact, the splitting observed by Stern and Gerlach was due to the spin of the unpaired electron in the last shell of the silver atom, but nobody knew about this in 1922. The splitting was not due to the "space quantization" that they all believed was being confirmed. Space quantization is a real thing but its effect happens to be zero for the silver atoms used by Stern-Gerlach. In the follow-up video I will show what Stern-Gerlach did next: they experimentally determined the magnetic moment and found it to be exactly Bohr's magneton. Why? Another coincidence of terms cancelling each other out that instead of pointing to spin, made it look like space quantization was the reason of the beam splitting.

[@fabienleguen]

@@jkzero this bonus explanation is as mind blowing as the video. Thank you so much !

[@NoahFect]

@@jkzero One suggestion for your follow-up video might to be to point out that we still use a variant of S-G's apparatus for timekeeping. As I understand it, the most common primary atomic clock standards use alkali metal beams for that reason. They perform state selection through magnetic deflection of the single unpaired valence electron, which is really the star of the show rather than the atoms themselves.

[@dennyoconnor8680]

Outstanding lecture on the personalities involved during an exciting time in physics. Now, if only we had used a different word than Spin which leads the mind by the nose into attempting to picture the magnetic effect on the beam as pushing around a bunch of toy Tops spinning away. (sigh)

[@jkzero]

I cannot agree more, using "spin" for the intrinsic property of the electron that looks like a classical angular momentum has really mess up many minds, including every single physics student and physics enthusiast. Unfortunately, originally they really thought that the electron was spinning. After realizing that nothing was spinning they should have picked another word.

[@homerp.hendelbergenheinzel6649]

wow that was very insightful. thanks for your efforts. its a great video that helped me strengthen my understanding of the experiment. say, could you do a video with the experiment when the realigned the magnets and used it to confirm the spin?

[@jkzero]

I am glad you liked it; the aftermath of the experiment deserves its own video, coming soon

[@homerp.hendelbergenheinzel6649]

@@jkzero tyvm, im looking forward to it (:

[@harrybarrow6222]

When I was a university student studying mathematics and physics, I was not very interested in how the ideas were developed, nor in the people involved. In later life, I am now VERY interested in those things. Thank you for an excellent video.

[@jkzero]

Thanks for sharing. I feel that so much is left out during our studies that it is no surprise that there are also so many unclear concepts and misconceptions. Making these videos has also been a journey of discovery for me, reading the original papers by the masters is quite hard, we are used to learning from textbooks that condense decades of knowledge. In the old papers everything is all over the place and hard to follow but it is also quite refreshing to follow the reasoning of these people.

[@stevenverrall4527]

No room for purely classical mechanics. However, semiclassical proton and neutron models have been proposed and published in peer reviewed journals. For example, "Ground state quantum vortex proton model"

[@maciejnajlepszy]

And still nobody has proven the non-existence of the ether.

[@harrybarrow6222]

Excellent scientific history!

[@kaxndr1674]

Excellent. Well presented and informative. While I don't understand the formulas, the illustrations showed me what they predicted and why. This is a great demonstration of why science and physics in particular is objective and changes as more data is acquired through mathematics and experimentation. Stern had to change his preconceived ideas due to the new evidence. Kudos to these individuals who built the foundations of our understanding of quantum physics.

[@jkzero]

I am so delighted that viewers enjoy the content as much as I enjoy making it

[@RobertoCarlos-tn1iq]

great video with lots of information. but at 0:14 seconds, you said 1822 instead of 1922.

[@jkzero]

I am glad you liked the video; unfortunately, my deteriorated elocution failed me again. I really said "1922" but too fast and it sounds like "1822." It happened in another video too and since then I try my best not to mess up dates, for this reason I also try to show the date on the screen in case I mess up. I hope this didn't deter you from watching the rest of the video.

[@RobertoCarlos-tn1iq]

@@jkzero no worries. i activated the closed captioning and it also said 1822. weird. but you add so much to this famous experiment. worth the view and subscription.

[@alvarolouzi]

What does a big bank in the US, a bad cigar and two physicists have in common? Watch the video to find the answer!

[@paulmicks7097]

Thank you, a story very well told, can be used to tell around a campfire 🔥

[@rodya9926]

Excellent

[@abrikos1100]

This videos really help to *understand* QM, thank you very much

[@jkzero]

Glad to hear that! I really appreciate you sharing that the content is useful.

[@Mark-ce9xh]

You are the best at this. Absolutely 💯

[@federicociampiconi2852]

Amazing video, filled with interesting and surprising historical details. It always amazes me how quantum physics especially boggles the mind of physicists, who eventually have to accept it as a fact of nature. To this day a satisfying and consistent framework of QM and QFTs is not available. These discoveries were truly a turning point for physics, like nothing else.

[@Testgeraeusch]

It's weird to see them using the quantum number k \leq n when nowadays we use l < n. But clasically, an orbit with zero angular momentum is nonsense...

[@jkzero]

I agree, an orbit with zero angular momentum is nonsense... unless there are no orbits, that's the quantum-mechanics view

[@PM-fs2eg]

Amazing...I mean...the discoveries they made on equipment available. Mindblowing!

[@janami-dharmam]

I visited ETH early this month; I did not see the labs but the lecture halls only. The canteen was impressive.

[@DavidMFChapman]

Another amazing story! I liked the fund-raising aspect.

[@ДаниилИванов-г3ж]

That's funny how I was skipping all the "history" part when I learned QM during my undergrad, just some stuff no one uses - I literally ignored old QM theory since it will never be asked during the final and no one uses it. More or less the same with understanding such groundbreaking experiments (SG, photoelectric effect and blackbody radiation) - just a cool story, I better focus on something real. But years later I realized how ignorant I was. I believe that in order to be a good physiscist one needs to have a solid understanding not only of different formalisms and approaches but also to understand the foundation of it, appreciate its beauty. And I can tell by watching your videos on QM that it gave me not only a better understanding and intuition on concepts already known to me, but ignited a spark in me to read about this specific topic and search more about it (which I thought is redundant since I know a lot about these experiments after at least 4 QM courses during my undergrad and grad). Thank you billions for once again giving me an additional insite on the topic that I naively think I know good enough.

[@jkzero]

I find most accounts of these stories to focus on the final result but I find the problems, the struggles, and the wild guesses fascinating and decided to share them here. Glad to find so many people moved by these stories and that don't shy away from some taste of the math behind.

[@bernarddeham4787]

Great video So far I thought that this experiment was about the spin of the electron great scientific KZbin channel indeed.

[@jkzero]

Glad you enjoyed it and that you like the content. I will clarify how SG experiment connect to spin in a future video but yes, this experiment was designed and motivated when nobody knew about spin.

[@supreetsahu1964]

Hey can you recommend me books on scientific history? I love the stories you tell

[@jkzero]

I cannot thank you enough for your continuous support.

[@WyjscieAwaryjnePoSchodkach]

This really well explained 😊

[@GeoffryGifari]

Hmmm why did the Stern-Gerlach experiment turned out a negative outcome the first time? When Stern, Gerlach, and Born were still together

[@jkzero]

Good question. A follow-up video is coming, several people have asked this so I will address it in detail.

[@grumpyg9350]

@@jkzerothey changed the developer used on the plate.

[@chrisdickens4862]

This was great! Thanks.

[@0neIntangible]

(22:27) When the narrator says: "... they soon realized the reason for their Lucky Strike... They smoked in the lab...." Coincidence... intentional (or not), connection in "Lucky Strike"(as in the popular cigarette brand), being mentioned in relation to the sulphur aerosol particulates from cheap cigars affecting the deflection pattern on the plate.

[@luudest]

lol

[@jkzero]

I like leaving Easter eggs in my videos, it is great when viewers spot them.

[@markotrieste]

24:26 I miss what changed between 1921 and 1922. Why did it took months to find the line split? What did they change in the experiment?

[@jkzero]

One issue with the early attempts to measure the split or widening of the beam was the collimation step right after the oven, the initial beam was too wide making the split not easy to observe. Gerlach spent many weeks trying different geometries and the final version used the two consecutive rectangular slits.

[@markotrieste]

@@jkzero Thanks 🙏

[@fooboomoo]

what a great channel!

[@MikeWiest]

Great, thank you!🙏

[@no-one_no1406]

Thought experiments are truly the king of theoretical physics. And maybe physics and engineering in general.

[@lvmbk3755]

Beautiful. Thank you!

[@shahriarrudra7495]

This channel is gem 💎💎💎

[@jkzero]

glad you like it

[@uoflphysicsdepartment8866]

Great vid!

[@erikziak1249]

Brilliant video. Thank you.

[@jkzero]

Glad you enjoyed it!