The Forgotten Experiment That Proved Quantum Mechanics

what would it take to convince you that the reality around you was fundamentally different from what you thought you understood it might start with noticing cracks like discontinuities things you might not quite expect or cannot explain breaks in what you thought was real from these cracks stories go one of two ways either into madness or into Revelation Revelations that allow Humanity to stare deeper into the abyss of the universe when Dalton found two gases reliably combined at a ratio of 2:1 to produce a third gas he reasoned all materials must be built on fundamental building blocks combined together he revealed the atomic world when Einstein imagined chasing after a beam of light he realized no matter how fast he moved light would move away from all observers at the speed of light and revealed to us relativity these insights are few and far between unless you're Einstein and only privy to select number of individuals throughout history was sometimes centuries long intervals between each Insight again unless you're Einstein but there is one story that is rarely told and is usually misremembered before Schrodinger's cat was alive and dead before electrons could be both particles and waves and insight described by Einstein as one of the most important of all time and a rare one in that it wasn't an Insight he made himself that is the story that I want to tell today how he peeled back the workings of the universe and stared Into the Heart of quantum mechanics for the very first [Music] time this Story begins in the early 1900s with a talented Scientist by the name of Otto Stern known for his rigorous attention to detail Stern completed his Doctorate in physical chemistry from the University of Breslau in Poland and joined the University of Prague as the very first pupil of none other than you guess it Albert Einstein under Einstein's tutelage Stern became interested in the nature of the atom the pair allegedly held many discussions in a cafe attached to a brothel bringing together three of the most powerful forces in the universe physics caffeine and the desire to impress girls and there was a lot to talk about the world of physics had recently been shocked by a new theory of the atom Dalton's 1803 simple building block atom had been replaced in 1904 by tomson's Plum Pudding model a mix of positive negative and neutral subatomic particles all clustered together in 1909 Rutherford proved this incorrect by firing alpha particles at a foil of gold atoms most passed through unaffected leading in 1911 to Rutherford proposing the atom was largely empty space with a high density positively charged core and negatively charged electrons orbiting much further out in 1913 ball was determined to make things one step more complicated and suggested that the orbiting electrons must be at fixed distances and angles relative to the nucleus a suggestion that no one was really that happy with because why would the universe be quantized into discrete steps rather than the nice continuous spectr like most phenomena we observe the good thing about this theory is that it enabled B to explain a phenomenon that had puzzled physicists and chemists for decades the fact that atoms can only absorb and emit light at discrete sets of optical wavelengths for example this is the emission of the hydrogen atom where light can only be absorbed or emitted at these wavelengths which correspond to the atom capturing or releasing just the right amount of energy for an electron to jump between these orbital levels but there is an inherent problem with this idea according to classical physics orbiting charged particles like electrons should radiate energy and so spiral downwards to ultimately collide with the nucleus as this does not happen in reality B suggested a counterintuitive restriction to get around this problem electrons just aren't allowed to lose energy to put into perspective how weird this is imagine a child on a swing if you were to quantize this child's swing they could only be swung to specific Heights or specific angles rather than any height or any angle in between why would the universe we live in operate like this when we have no indication this is Its Behavior stern was equally unconvinced by the many restrictions in B's Theory writing to his colleague If this nonsense of bore should in the end prove to be right we will quit physics little did he know this conviction was putting the wheels in motion for stern to attempt to disprove B's conjecture like Stern and Einstein I too like thinking about science in cafes the only problem is that I'm often connected to public unprotected networks putting my data at risk which is why I'm excited to be working with today's sponsor private internet access vpns or virtual private networks keep you safe by creating a private connection between your device and a remote server this digital connection is encrypted meaning no one else can see it without that protection Bad actors can track your activity or steal your personal data including search history key loging or even photos another perk of vpns is that they hide your IP address so you can't be traced based on your location which in turn can give you access to region restricted content from around the world on platforms like Netflix what I really like about private internet access is that my subscription covers an unlimited number of devices and it is compatible with more platforms so my computer my laptop my phone can all be protected if you've still got cold feet private internet access promises not to record or store user data and this has been proven to be true in a court and by a third-party audit from deoe so you can rest easy knowing your Digital Life remains private by using my link in the description you get 83% off so only $159 a month and as a bonus the first four months are free thank you private internet access for sponsoring the channel now back to the video Stern's work to disprove B would have to wait until after World War I when he returned from the front lines to the University of Frankfurt now working as an assistant for Max Bourne at The Institute of theoretical physics on experiments using Atomic beams with a goal to better understand the nature of some of the smallest building blocks in the universe in 1920 stern was joined by Walther GAC another skilled German scientist known for his considerations about the implications of scientific research and the responsibil ities of scientists and who had spent World War I developing an x-ray device to locate bullets and trapnel in wounded soldiers GAC was similarly focused on beam experiments in particular he wanted to see if atoms have magnetic moments meaning if there was a particular direction of magnetism inside an atom almost like detecting an internal bar magnet if an atom did have a dipole Magnetic Moment GAC reason it should experience a torque in the presence of a magnetic field and will therefore start to rotate if the measurement magnetic field varies in strength called an inhomogeneous field that will lead to a net force on that atom which will deflect it as it flies through the magnetic field the size of that deflection should indicate the size of the atom's Magnetic Moment when talking through gac's work Stern realized applying the same principle could be the test he was looking for to disprove B's atomic model either the universe is classical and electron can spin at any angle and so the internal bar magnet can point in any direction or according to bore they orient at certain angles relative to the nucleus something that seemed impossible Stern needed to find an element though where the effects of this fixed alignment would be noticeable and he came across an ideal candidate in silver which has 47 electrons and where the Magnetic Moment from the inner 46 electrons largely cancels out leaving just the effect of the very distant 47th unpaired electron by passing silver atoms through an inhomogeneous magnetic field in classical physics the beam should broaden as expected however if B's model was true if the electrons were constrained to certain angular momenta the same experiment should produce two silver atom lines on the detector together Stern the theorist and GAC the experimentalist formed the ultimate scientific team and set about trying to conduct an experiment that could revolutionize the world of physics even though Stern had carefully designed and calculated for his experiment actually building and running it was incredibly problematic progress was hampered as vacuum pumps and molecular Beam Technologies had only just been developed making them incredibly unreliable in order to vaporize the silver the pair needed to heat it to a, de C which had a habit of melting all of the seals on their gas vacuum chamber causing it to explode as a result running the experiment for a long enough time to collect significant data was almost impossible each run only managed to deposit a few silver atoms on The Collector Plate such a small amount that they couldn't be seen with a naked eye after many failed attempts inevitably the experimentalists funds ran out and it was only because Albert Einstein and the banker Henry gold man one of the founders of Goldman Sachs chose to bail out the pair with donations the experiment was able to continue even when the experiment was successfully running The Collector Plate was about the size of the head of a nail so producing legible results was incredibly challenging it was so bad that gac's graduate student Wilhelm shutz described it as a Copus like labor it was only due to some very poor lab etiquette and some very cheap cigars that the silver atoms that were deposited usually in visible to the naked eye were converted into a slightly visible black silver sulfide that meant that the very first images started to be collected though the results were inconclusive going forwards they moved to a photographic process to develop the silver but apparently kept smoking in the lab regardless which is not an endorsement even in the name of revolutionizing physics eventually after months of no progress Stern moved away to work as a professor at the University of Roso by this time it was 19 22 and the pair decided to meet in nearby Goan to discuss and ultimately decided to give up it was only due to sheer coincidence that the usually punctual European train line went on strike that same day and GAC was forced to spend the time retracing his experimental work over and over again in his mind Reawakening his obsession with the experiment on February 7th 1922 GAC spent the entire entire night shooting silver at The Collector Plate the next morning he and his colleagues developed the plate and revealed for the very first time two lines of silver neatly separated GAC rushed to announce the result the very same day he sent a short and to the point telegram to stern saying B is right after all he then sent a postcard to B with an image of the result of the split silver beam they had observed the postcard read attached is the experimental proof of directional quanti ation we congratulate you on the confirmation of your theory for the very first time a crack in our understanding of the universe had been brought into Crystal Clarity Frozen in time for everyone to see the Simplicity the reliability the sensibleness that we thought our universe respected was in fact wrong and a stranger deeper Theory now needed to take its place Einstein called to finding the most interesting achievement and nominated Stern and GAC for the Nobel Prize the physics Community around the world was fundamentally shaken but there is one last strange twist to our story B Stern and GAC were all wrong what Stern and GAC thought they were measuring was B's spatial quantization of electrons an inherently arbitrary feeling restriction of the angular momentum of the electron of the silver atom but the universe had one more trick to play this was wasn't quite the case the actual cause would not be found until several years later and is now understood to be the inherent angular momentum of the electron a property known as electron spin rather than the spin of the orbit around the atom it had turned out through sheer luck that Stern and gle's experiment the electron Spin and this anomalous Magnetic Moment happened to cancel out revealing the expected two line result so although Stern and GAC were right for the for the wrong reasons their answers still pointed scientists correctly at the pursuit of a quantum theory in order to find an explanation the stern GAC experiment demonstrated that physical properties like angular momentum and spin are discret quantized in their nature rather than continuous in Spectrum something that still makes all students of the universe scratch their head Stern's goal ultimately of definitively proving the foolishness of quantum theory backfired though he did not hold true to to his promise of quitting physics and instead he won on to win a Nobel Prize in 1943 for a subsequent groundbreaking discovery his lasting remarks on the matter were I still have objections to the beauty of quantum mechanics but she is correct it was this feeling when I was reading books as a kid of the pursuit of the clarity of understanding and that sudden aha moment that always excited me about looking at the universe 99.9% of us it is only in rereading and relearning about these stories that we can ever hope to capture that Moment of clarity of understanding that something about the universe is wrong and we've definitively proved it and that always was exciting to me and I think it's why so many people do ultimately get into science I'll leave you with a final comment from last week's video that I liked you know when a man with a lisp says bismo he means business check out that video here pick up a t-shirt or join our Channel if you would like to support us thank you as always for watching I will see you next week goodbye

Channel: Dr Ben Miles

Views: 126,377

Keywords: science, future, breakthrough

Id: kgO_EEjpQHI

Length: 15min 9sec (909 seconds)

Published: Thu Jun 27 2024