The Forgotten Experiment That Proved Quantum Mechanics

I'm 100% embarrassed to say I knew very little about this experiment until starting researching it 😅 I'd always assumed something like the double slit experiment was our big break. Awesome experiment - let me know what you think! Also - go to www.piavpn.com/drbenmiles to get 83% off Private Internet Access with 4 months free

Didn't hear a word of Dr. Miles for the first two minutes because I was waiting for the two pictures on the wall behind him to move on their own again!

Stern-Gerlach experiment is hardly forgotten; it’s covered in every QM class. Also, it was nowhere near first experiment to show quantum effects: blackbody radiation, hydrogen spectrum, etc. came first.

Literally all quantum textbooks start with explaining the significance of these experiments

OMG, seeing people smoke cigars while doing lab work is so crazy.

Thanks for the "new" presentation of this scenario. I learned about the second-hand cigar smoke being a KEY to the success of this experiment but did not realize that it wasn't originally designed to identify spin.

I remember the Stern-Gerlach experiment being presented in my undergrad QM and Atomic Physics courses as the experiment that verified electron spin. Thanks for the real “back story”. Interesting how when one sets out to prove or disprove something, the results turn out to verify something different.

I got married. After that, I knew the reality around me was fundamentally different from what I thought I understood.

they were also lucky that a 19th C mathematician named Sophus Lie worked an useless abstract realm that turned out to be not so useless, otherwise this two component spin thing would have never made any sense.

I'll admit I am embarrassed I just now realized that Stern-Gerlach was two names instead of a single person

Sorry for being that guy, but you've some errors in the introduction. First, Stern was German and Breslau a German city back then. That changed in 1945. Secondly, the 19th century refers to 1801 till 1900. 1901 till 2000 is 20th century.

Looks like that moment of clarity passed me by. Never understood a thing.

This explanation on Bohr’s model missed a key part. Bohr used Planck’s constant h, that was used to explain Black Body radiation, in his model of the Hydrogen spectrum. This constant h divided by 2pi is the quantum unit of angular momentum that the electron can have when it orbits the nucleus. This was a revolutionary step in modern physics.

The earliest evidence for quantised electron energy levels in atoms were the narrow bands in the visible (and later IR and UV) emission spectra. The names given to the lines were "strong", "principal", "diffuse" and "fundamental" as scientists like Rydberg and Balmer tried to understand their significance. Those names live on as s, p, d and f sub-quantum levels for the orbitals. Bohr used the spectrum of hydrogen as the basis for his atomic model and realised the electrons could only have certain specified energy levels. Quantum physics was built up on a variety of observations from spectroscopy and mathematical models of radiation, etc., not just the work of one person or one particular experiment.

Stern-Gerlach experiment is not forgotten, if mere amatures like myself, born long after that era, have some (small) understanding of it. Gotta say the last point you made about what they thought they were measuring vs what they actually measured, was something i hadn't really appreciated. Thanks for telling the tale in a fun and engaging way!

Your comment about the "Aha!" moment in science is spot on though it's sometimes the "that's funny..." moment. I liked the expression of it by Edna St. Vincent Millay, who was very definitely not a scientist but was similarly taken by Euclid's discoveries in plane geometry: "Euclid alone Has looked on beauty bare. Fortunate they Who but once only and then from far away Have heard her massy sandal set on stone." If you've had the experience you know what she means.

A great video, and sensibly humorous loved the " not a brothel" sign behind him when drinking his coffee. Master stroke

I've heard abou this experiment for years and I am so glad to hear the story of the hurdles and insights that we needed to attain the result. Great video!

2:02: Breslau in 1912 was in the German (previously Prussian) province of Upper Silesia. It became part of Poland in 1945 (as Wrocław).

So how did other scientists discover that they were wrong, and that what the two had discovered was actually electron spin? Maybe make a video on/explaining that?!! That'd be cool!