Why Do Superconductors Float?

hi i'm science educator and the least attractive hemsworth brother kyle hill as legendary physicist richard feynman once said if you think you understand quantum mechanics you don't understand quantum mechanics that's why before today's episode i watched the documentary exploring quantum history with brian greene on curiosity stream the sponsor of today's episode curiositystream is the award-winning destination for documentary series and features covering every topic from space exploration to dinosaurs curiosity stream adds new films and series each week with subscriptions starting at just 2.99 a month plus 25 off for a year subscription plus you can watch it just about anywhere screens exist if you want to try curiosity stream like i did then go down into the description box below click the link and get curiosity stream for a full year for just 15 personally i'm going to be going on it to watch david attenborough's light on earth later tonight because as you know if there's two things that i love it's bioluminescence and old british dudes now let's see just how much quantum mechanics we can understand today to me this might be one of the coolest and most easily amazing effects in all of science but its explanation is also one of the most casually confusing so today what is quantum levitation and how does it work you're staring again oh right sorry i just i may have developed a perpetual motion device now entering the facility as with anything to do with quantum mechanics to really get our heads around this topic we need to begin with the basics yes i could just hold up a wafer of yttrium barium copper oxide and yell quantum like i'm deepak chopra or something but then we wouldn't really learn anything and we'd just be selling poorly written self-help books so let's begin with magnets how do they work well don't worry juggalettes your boy gotcha so a strong permanent magnet like the neodymium squares you are seeing on screen project a magnetic field outside of themselves as the result of innumerable atomic alignments if we zoom all the way down to the size of atoms we will see the secret of magnetism that has confounded many a juggalo in this simplified diagram simplified remember of a single atom we have a nucleus of protons and neutrons with a quote-unquote orbiting electron the electron is zipping around the nucleus spinning like a tiny moon as it orbits this spin and the motion of the nucleus gives the atom an overall magnetic moment keep in mind nothing is really spinning it's more of a quantum mechanic nevermind now in most materials the magnetic moments of the atoms are all over the place and any overall magnetic field that would be generated is instead cancelled out by the randomness but in a permanent magnet like neodymium all of the atoms moments instead add up they are aligned the microscopic influence from quadrillions of tiny magnetic fields adds up and an overall magnetic field pushes itself outside of the boundaries of the material so far so good great feel free to show that last part of the video to any juggalos that you might know who wear way too big shorts with chains the next step is to understand what happens when a magnetic field starts moving as we said electrons orbiting their nuclei have some influence on the atom's magnetic moment it stands to reason then that a strong external magnetic field might attract or repel those tiny magnetic moments in short moving magnets moves electrons and this is the real key to quantum levitation yep sorry it's just it's really cool there is another name for moving electrons for moving charged particles and that is electric current now one of the fundamental properties of electromagnetism is that an electric current generates its own magnetic field so if you're following along we have a moving magnet creating or inducing an electric current which creates its own magnetic field the reason why this happens has to do with special relativity and the fact that an electric field or a magnetic field can be the same thing as viewed from different points of reference but that has to do with einstein and frame dependent length contraction and if you want to know more about all that you can just go to my adoptive father veritasium's youtube channel and check it all out there what we want to know is that the magnetic field from this electric current is not random in fact it's created in opposition to the original magnetic field that made all of this happen it's because of electromagnetism that these fields are always intertwined in this way like peanut butter and jelly macaroni and cheese or millennials and depression you know what i mean you're probably anxious right now aren't you aren't you so to recap a changing magnetic field or magnetic flux can induce an electric current or eddy current in some conductive material which then in turn creates its own magnetic field in opposition to its parent like a teen with very poorly cut bangs now once you understand eddy currents that can attract and repel like normal magnets do you can see some absolutely amazing physics like the slowing of a strong magnet falling down in a copper tube or the magnetic breaking that looks almost like magic when you put a hunk of aluminum in an mri don't do that but even with a magnetic field strength of an mri that is 50 000 times stronger than the earth's magnetic field nothing is levitating yet why well that question brings us to the last piece of this puzzle did you ever do this little science experiment as a kid i did you take a strong permanent magnet and you run it along something that your teacher told you could become magnetic that's amazing mr d but now we can explain what's actually happening here when you have something like a material like inside of this nail that has a lot of misaligned magnetic moments you can take a strong permanent magnet like these neodymium discs and you can run it across the nail 20 to 30 times and when it does it causes all those magnetic moments to line up with the magnetic field specifically of this magnet and so do it enough times and you can make the magnetic field of this look like this and have some fleeting magnetism we can explain this effect now and you could call it the jugger lowdown if you want which i do want to do when i was just a boy before i invented the patented lion's mane i got to ride a real hoverboard sure it sounded like a dying cat when you turned it on and only had a battery life of a few minutes but it did indeed hover now the inventor of this hoverboard didn't want to tell me how it actually worked you know it's patented at all but when i guess spinning magnets driven by a motor he got all shifty so i guess i'm probably right and you now have the tools to explain why i was right spinning magnets in the bottom of this board would create some changing magnetic field some magnetic flux and this would induce an electric current in the copper beneath the board or another conductive material which would create eddy currents which would serve to repel the board and lift it up we are definitely closer now to quantum levitation but again there's a problem copper is very conductive but there's still some electrical resistance to electric current in something like copper to achieve truly effortless quantum levitation we would need stable and non-dissipating eddy currents and zero resistance to electric flow so now we need to go beyond the conductor to the superconductor and this thing i've had in my pocket this whole time just so happens to be one he named it stephanie i what i don't fall in love with exotic materials what what certain materials under certain conditions allow electrons inside of those materials to flow completely free of any electrical resistance and therefore form inside them perfectly stable ed and eddy currents these materials are called superconductors stephanie here is just such a superconductor which i specced out and purchased with the help of quantum levitation and the quantum condition she needs to be in is one of cryogenic temperatures we can get these temperatures via immersion in another material liquid nitrogen which you can purchase easily enough just about anywhere now why a superconductor exactly transitions into superconducting at sufficiently low temperatures is extremely complicated it will have to suffice for me to say today that if you want to know more about it you can look up so-called bcs theory which won a nobel prize in physics in 1972 what's important for us to understand to continue this program is that we know enough of the physics to make relatively easy and very nicely high temperature superconducting material so now it's time to go all the way back to the beginning of this program watch this now if i did my job right you should be able to explain why this happens above the superconductor gravity is trying to pull the magnet down but if the magnet did fall that would be changing the magnetic field right so in response to the falling magnet and the changing fields eddy currents form and stabilize in the superconductor below at every possible instant we are witnessing a magnet falling but met by perfect eddies in opposition flowing freely and perfectly in a superconductor also note that i can spin the magnet about this axis because it doesn't change the magnetic field this phenomenon also works in reverse and i gotta be honest i've kind of been holding out on you the reverse situation which happens for different reasons might be even cooler than this yeah i know wow this is absolutely amazing right and you probably noticed something different it's not spinning it's not moving around and if i touch it it almost stays in the orientation i leave it in three-dimensional space-time like it's magically locked in space this is due to a related phenomenon that we just need a little bit more physics to fully explain what's that uh no ari and i just worked together saturday uh yeah i'm yeah i should be it's not it what it's not weird just a quick aside about magnet safety before we continue magnets are awesome they're quantum magic that we can see with our own peepers but they are no joke very strong magnets like these neodymium discs which you can buy basically anywhere are deceptive in that they react with each other dependent on the distance the attractive force between them gets exponentially larger the closer they get according to the square of the distance that is to say they don't seem like they're an issue until they're totally an issue and with bigger magnets this if you're not paying attention could lead to pinched skin injury broken fingers all that kind of stuff so for the rest of the episode know that my magnets are being stored in special packaging they're away from other metal surfaces that they could be attracted to and they're away from my sensitive electronics look magnets are awesome but they are no joke and you got to take them really seriously okay what are you using neodymium magnets as earrings no stop snitching on me today dang the ultimate in quantum levitation is this a superconductor amazingly locked in space time it occurs because one of the other fundamental characteristics of these materials is that when they fall below the superconducting transition temperature they expel all the magnetic fields within them when a superconductor is placed in a magnetic field the material will force any flux any changing magnetic field to go around specific superconductors though type 2 superconductors like the one you see here will let some field through now we have magnetic vortices acting like invisible pins holding the superconductor in space unlike the levitating magnet if you want to put everything in more physicsy terms our type 2 superconductor made of yttrium barium copper oxide when it falls below the transition temperature displays the masonry effect due to the impurities in the material and therefore gets flux pinned in space those 10 words are nice and all but they don't mean very much unless you understand the key concepts behind them and hopefully now you do and hey let's let's stare at it some more so this is probably the coolest thing that i've ever seen with my own seeing balls and better yet we now know exactly how this works and why this happens if you want to see just how crazy quantum levitation can get stay tuned on this channel in the upcoming weeks because i worked with quantumlevitation.com to make what i think is a world first it's it's gonna be awesome until next time oh he cooled down it's all right you can rest it cools down and then the effect goes away i didn't explain that part now exiting the facility thank you so much to the very nerdy facility staff for their direct and substantial support in the creation of this here video today especially i want to recognize research assistant june choi and visiting scholar michael calder if you want to join the facility get on the staff get your lab coat get episodes early get behind the scenes photos and videos get to join the discord talk with me almost every day join our d d groups our magic gathering league all that nerdy goodness you can go to patreon.com kyle hill and get on the staff today and hey if you support the facility just enough get your name on aria here each and every week and as you can see there's literally hundreds of you i'm adding minutes to the ends of these videos and that really hurts watch time and i have no idea do you know what's fun about liquid nitrogen it's not really fun but it's interesting so a doer of liquid nitrogen like this this is what is really expensive about liquid nitrogen and as you can see the cap is very loose that's because there is no doer that has a solid cap do you know why well there's basically no place in the universe where it's going to be a an advantageous environment for the temperature here that is to say that it's always going to evaporate and if that's the case then if this was sealed which it never is then eventually build up enough pressure to explode so these are never fully capped there's even a pressure release valve release valve here it's heavy release valve here that is just just with a little bit of goo on there so it could also it could all thanks for watching

Channel: Kyle Hill

Views: 244,466

Rating: 4.9735813 out of 5

Keywords: because science, engineering, kyle hill, learning, math, physics, science, stem, the facility, quantum, quantum levitation, quantum levitation explained, superconductor, levitation, flux pinning, quantum locking, meissner effect, boaz almog, magnetic levitation, quantum mechanics, liquid nitrogen, yttrium barium copper oxide, quantum physics

Id: kEDCE2nOQeM

Length: 16min 39sec (999 seconds)

Published: Mon Nov 23 2020