This experiment confirmed quantum physics

In this video, we dive into the details of how the Stern-Gerlach experiment provided unquestionable evidence of quantum behavior in atomic physics.

[Related videos]

[Erratum]
01:02 Einstein received his Ph.D. from the University of Zurich, not the ETH Zurich. Thanks @mattabesta for pointing this out.

[References]

∘ W. Gerlach and O. Stern, "Der experimentelle Nachweis der Richtungsquantelung im Magnetfeld," Z. Phys. 9, 349 (1922)
∘ G. E. Uhlenbeck and S. Goudsmit, Naturwissenschaften 13, 953–954 (1925)
∘ A. Sommerfeld, "Zur Theorie des Zeemans-Effekts der Wasserstofflinien, mit einem Anhang über den Stark-Effekt," Phys. Z. 17, 491 (1916)
∘ P. Debye, "Quantenhypothese und Zeeman-Effekt," Phys. Z. 17, 507 (1916)
∘ O. Stern, "Ein Weg zur experimentellen Prüfung der Richtungsquantelung," Z. Phys. 7, 249 (1921)
∘ W. Gerlach, "Otto Stern zum Gedenken," Physikalische Blätter 25:412 (1969)
∘ D. Herschbach, Angew. Chemie Int. Ed. Engl. 26, 1225 (1987)
∘ W. Gerlach and O. Stern, "Der experimentelle Nachweis des magnetischen Moments des Silberatoms," Z. Phys. 8, 110 (1921)
∘ W. Gerlach and O. Stern, "Über die Richtungsquantelung im Magnetfeld," Ann. Phys. 74, 673 (1924)
∘ M. Born, "My Life: Recollections of a Nobel Laureate," Scribner, New York (1978)
∘ B. Friedrich and D. Herschbach, "Space Quantization: Otto Stern's Lucky Star," Daedalus 127, 165 (1998)

[Credits]

Stern-Gerlach experiment, by Tatoute under CC BY-SA 4.0
Spin angular momentum by T. Knott/CheChe under CC BY-SA 4.0
Otto Stern, public domain
Prag (1912), by J. Neuwirth, public domain
Albert Einstein in 1912, by J. F. Langhans , public domain
Max Laue, public domain
X-ray diffraction by W. Friedrich, Knipping P, M. Laue, Classe der K.B. Akademie der Wissenschaften zu München (1912)
Wettermessungen, by the German Federal Archive, under CC-BY-SA 3.0
Feldberg weather station, by T. Berwing, under CC BY-SA 3.0
Steps at the Solvay Insitute, by T. Sheerman-Chase, under CC BY 2.0
Walther Nernst, public domain
Wreckage of a German Albatross D. III fighter biplane, by Library of Congress, public domain
James Franck, public domain
Gustav Hertz, public domain
University of Frankfurt am Main in 1920, public domain
Otto Stern in the lab, AIP
Visible spectrum of hydrogen, by J. Homann under CC BY-SA 3.0
Max Born, public domain
Arnold Sommerfeld , by Bain News Service, public domain
Peter Debye, public domain
Sommerfeld orbits, by CielProfond under CC BY-SA 4.0
Rutherford atom animation, by G. Creador under CC BY 3.0
Solar system, by Orrery under CC BY-SA 4.0
Walther Gerlach, public domain
Universität Frankfurt, Archiv der Universität Frankfurt
Friedrich Paschen, public domain
Menschenmenge vor Bäckerei, by German Federal Archive, under CC-BY-SA 3.0
Wrecked WWI crane, by National Library of Scotland, public domain
Starlight bent by the sun's attraction, by W. B. Robinson, public domain
Reichsbank, Geldauflieferungsstelle, by German Federal Archive, under CC-BY-SA 3.0
New York City Skyline, New York, by I. Underhill, public domain
Goldman Sachs Tower, by J. Hałun, under CC BY 4.0
Goldman Sachs logo, by The Goldman Sachs Group, public domain
Born lecturing, AIP
Rostock, public domain

AIP: American Institute of Physics, Emilio Segrè Visual Archives

[Coolmd-itck]

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

[heribertovasquez]

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!

[thesouledguitarist]

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.

[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.

[willrein]

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.

[mfj]

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.

[jeffwads]

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

[copywright]

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

[ffs]

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.

[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!

[АлексейИлларионов-шо]

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 🔥🔥🔥

[rbarberac]

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

[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.

[SmallPharm]

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

[markborz]

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

[luudest]

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

[WD_GX]

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

[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).

[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.