yaaaaay! Welcome to the jungle.
The issue is as follows - this process defines the superconductor as a... quantitatively* different from a normal conductor. Is there something that separates them qualitatively* or there's just a theoretical borderline that separated the definitions of the two?
yeah, this is a neat question, because the answer is crazy and historic and we alluded to it a little in the show, but we forgot to talk about it explicitly.
so 100 years ago Heike Kamerlingh Onnes was testing the conductivity properties of mercury. he would lower the temperature a bit, and then the resistance would drop by a little bit.
and then there was a threshold. 4.2 Kelvin, where all of a sudden *BOOM* it went to zero. it turned into a superconductor. as far as I understand it (and you'd be surprised the number of times in this episode where my experts corrected me and made me re-state things) superconductors are fundamentally different than regular conductors, the same way solids are different from gasses. there's a sudden transition between the two.
essentially what happens is that above 4.2 kelvin, all the electrons are regular electrons. as the heat in the metal decreases, they start to stack on the "bottom" of the bathtub.
and as darren kept saying, the electrons who live "below" the water line of the bath tub can't really do much. they're stuck in place (well. not quite in space. but you can't change their momentum)... (because the bath tub is a metaphor for the momentum space. )
but then at 4.2 kelvin, BOOM, all the "surface" electrons pair up and start acting like bosons. this effectively freezes ALL of the electrons to not change what they're doing. all of the electrons "below" the surface are stuck in place, as we've said. all of the electrons *on* the surface are stuck because they've been paired up.
um. so yeah. they are characteristically and fundamentally different than regular metals. it's not just like when... I dunno... a student graduates from university. technically, you could have pulled them out of class 2 weeks before the end of term, and they'd be pretty much the same.
instead they're more like the hulk, when they change, you get something super different.
*bows to rampant applause that occurs whenever the hulk is used in a metaphor*