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.
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.
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!
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.
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.
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.
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 🔥🔥🔥
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.
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.
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.
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.
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
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.
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?
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.
What creates the space quantization/orbitals of the electron field are the longitudinal/scalar impulse frequency of the nucleus of the atom. The longitudinal waves, which are a voltage potential and gravity are what manifests the transverse electromagnetic waves, which are called electrons. The longitudinal impulse frequency determines how many orbitals will form, and in what pattern due to longitudinal wave addition and cancellation effects. The higher the frequency, the greater the mass of the nucleus of the atom.
“We gotta take down Bohr. Let’s design an experiment to once and for all her back into classical land” Oops. And all of this after WW1 and all of the economic woes. In just a few years Hitler comes into the scene so the fact this was even accomplished is equally amazing as the experiment itself. So simple as well.
Exactly, I bet Stern had a Millikan moment, although for what I have read Stern was a very kind human being, not like Millikan. There were so many reasons that could have made this experiment fail, I really wanted to show all the struggles, from Stern's surviving a plane crash to the little money they had becoming useless. But I also wanted to emphasize the role of others like Einstein but mostly Max Born, who not only approved the project but really worked hard for the experiment to be completed. Special mention for the unsung heroes of experimental physics: lab technicians.
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?
Glad you enjoyed it! You are not alone, like most people, I was thought 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.
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)
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.
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.
You are totally right, I messed it up; thanks for pointing this out, I am always happy to add corrections. I included the appropriate erratum in the video description and credited you for that. Thanks again fro the constructive feedback.
you need to ask: why did the beam split into two? in other words, where did the atoms with angular momentum different from parallel and antiparallel to the B-field go? Classically the beam should spread up and down but not split. The experiment shows that the beam splits, it doesn't spread.
The first time stamp shows a more simplified model of the experiment where the beam entering the magnets is a thin ray. Correspondingly what exits the magnets are thin rays angled up and down. The question was whether they would sweep out a continuous range or only appear at 2 specific angles. The second time stamp shows something more faithful to the original experimental setup. You can see there that the slits turn the particles emitted by the oven into a thin horizontal line instead of a thin ray as shown in the first simplified picture. The question is still the same: will this thin line be deflected up and down continuously (leading to a rectangle on the detector) or only at 2 angles (leading to 2 separate lines on the detector). As he shows at the end, in the actual pattern the separation was stronger in the center than on the sides due to the nature of the magnetic field, but this is only a minor point. The detail of a thin line vs a thin ray is typically omitted because it doesn't matter for the theory behind the experiment and I guess a ray makes it easier to draw and understand
7:00 "...a third quantum number" that "...could not take any integer values." Meaning they cannot take 𝘫𝘶𝘴𝘵 any integer values, only 𝘤𝘦𝘳𝘵𝘢𝘪𝘯 integer values. Right?
By far the best video in the history of pedagogical introduction to the Stern-Gerlach experiment!
thanks, the aftermath of the experiment deserves its own video, coming soon
This channel is a gem
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.
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.
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!
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.
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.
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.
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 🔥🔥🔥
thanks, I am so delighted that viewers enjoy the content as much as I enjoy making it
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.
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.
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.
Another key experiment on its historical context. Thanks for this series. It’s wonderful.
Glad you enjoy it!
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.
the aftermath of the experiment deserves its own video, coming soon
It is a crime that your channel has just 34K subs. These videos are priceless.
Dr., I'm not a physics major, but your videos has made me love physics experimentation and result interpretation
Thanks fro this, it really means a lot. I am glad that you like the content and that it can sparkle interest in physics.
Finally, i've been waiting for this video!!!
I hope the wait was worth it.
@@jkzero it was worth it and I can't wait to watch your next video, you're one of the best channels in youtube
Keep it up man.
Your videos are really educational 🙌
Glad you think so!
Breathtaking video (really)! You are a great story teller. I finally understood the Stern Gerlach Experiment. Thank you very much!
Great to read that the experiment is now clear for you. Thanks for your comments, I am glad you like the content.
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
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.
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?
Excellent video, please continue your work
That's the plan!
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.
So cool, great video. Glued til the end.
Glad you liked it!
Wonderful story and experiment. Thanks a lot. All the best.
Amazing video!!!
Glad you liked it!!
What creates the space quantization/orbitals of the electron field are the longitudinal/scalar impulse frequency of the nucleus of the atom. The longitudinal waves, which are a voltage potential and gravity are what manifests the transverse electromagnetic waves, which are called electrons. The longitudinal impulse frequency determines how many orbitals will form, and in what pattern due to longitudinal wave addition and cancellation effects. The higher the frequency, the greater the mass of the nucleus of the atom.
These videos are simply amazing.
Glad you like them!
“We gotta take down Bohr. Let’s design an experiment to once and for all her back into classical land”
Oops.
And all of this after WW1 and all of the economic woes. In just a few years Hitler comes into the scene so the fact this was even accomplished is equally amazing as the experiment itself. So simple as well.
Exactly, I bet Stern had a Millikan moment, although for what I have read Stern was a very kind human being, not like Millikan. There were so many reasons that could have made this experiment fail, I really wanted to show all the struggles, from Stern's surviving a plane crash to the little money they had becoming useless. But I also wanted to emphasize the role of others like Einstein but mostly Max Born, who not only approved the project but really worked hard for the experiment to be completed. Special mention for the unsung heroes of experimental physics: lab technicians.
Excellent
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?
Glad you enjoyed it! You are not alone, like most people, I was thought 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.
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)
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.
Very interesting. So when was spin first experimentally detected? And were Stern and Gerlach involved as we have been taught?
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.
Another amazing story! I liked the fund-raising aspect.
Thanks for the content, very good resource for self-learners and frustrated physicists
Einstein got his PhD at UZH not ETH
You are totally right, I messed it up; thanks for pointing this out, I am always happy to add corrections. I included the appropriate erratum in the video description and credited you for that. Thanks again fro the constructive feedback.
Great, thank you!🙏
Plz next video about Books and ressource......
how did this confirm quantum mechanics? i can explain the results classically. the atoms’ L aligns with +/-B. and then they get separated by L.
you need to ask: why did the beam split into two? in other words, where did the atoms with angular momentum different from parallel and antiparallel to the B-field go? Classically the beam should spread up and down but not split. The experiment shows that the beam splits, it doesn't spread.
12:36 vs. 19:25 Why is the beam from the second timestamp rotated by 90 degrees?
The first time stamp shows a more simplified model of the experiment where the beam entering the magnets is a thin ray. Correspondingly what exits the magnets are thin rays angled up and down. The question was whether they would sweep out a continuous range or only appear at 2 specific angles.
The second time stamp shows something more faithful to the original experimental setup. You can see there that the slits turn the particles emitted by the oven into a thin horizontal line instead of a thin ray as shown in the first simplified picture. The question is still the same: will this thin line be deflected up and down continuously (leading to a rectangle on the detector) or only at 2 angles (leading to 2 separate lines on the detector).
As he shows at the end, in the actual pattern the separation was stronger in the center than on the sides due to the nature of the magnetic field, but this is only a minor point. The detail of a thin line vs a thin ray is typically omitted because it doesn't matter for the theory behind the experiment and I guess a ray makes it easier to draw and understand
@@lunkel8108thanks! Just understood the experiment!
I am glad it is cleared out, I came here to reply too late
❤❤
@00:12 _"Stern and Gerlach did their famous experiment in 1822"_
*1922
7:00 "...a third quantum number" that "...could not take any integer values." Meaning they cannot take 𝘫𝘶𝘴𝘵 any integer values, only 𝘤𝘦𝘳𝘵𝘢𝘪𝘯 integer values. Right?