So, you're telling me that a fictional scientist and a skateboarder didn't create a Nobel Prize-worthy piece of levitation technology that would literally change the world? I guess it's Back to the Drawing Board... After a rather elaborate series of videos, denials, and eventual reveals, it turns out that Tony Hawk and Doc Brown will not be bringing you your very own hoverboard by the end of the year. As easy as this silly hoax was to uncover, you can never tell how much scientific damage is done by stunts like this (the fake video has 8.5 million views at the time of this writing). After all, thanks to Animal Planet, many people believe mermaids are frolicking topless on some distant shoreline. Thankfully, the hoverboard hoax is a teachable moment--we know how to hover boards (kinda). It sounds like magic, but it actually is an astonishing phenomena exquisitely captured by Tel-Aviv University in a viral video almost three years ago. Watch the video below, then stick around for the science that would make the Doc proud: http://www.youtube.com/watch?v=Ws6AAhTw7RA&feature=player_embedded Here's an even better video representation of the effect: http://www.youtube.com/watch?v=VyOtIsnG71U&feature=player_embedded Amazing right? So what is going on here? What we are witnessing in these videos is called the Meissner effect. Once a superconducting material has transitioned into the superconducting state (you have to cool materials down to near -273 degrees Celsius, or "absolute zero") it will eject all of the magnetic field lines from the interior of the superconductor. This ejection of the magnetic field is what "locks" the superconductor in place. It's quite literally very, very cool science. It looks something like this:
In the case of the video above, Tel Aviv University used a ceramic superconductor:
We start with a single crystal sapphire wafer and coat it with a thin (~1µm thick) ceramic material called yttrium barium copper oxide. The ceramic layer has no interesting magnetic or electrical properties at room temperature. However, when cooled below -185ºC (-301ºF) the material becomes a superconductor. It conducts electricity without resistance, with no energy loss. Zero.
To get a bit more technical, the magnetic field lines still get through the wafer, but only penetrate in the "weak" areas, or the boundaries between the grains of the material. These "flux tubes"--or areas where the magnetic field is passing through the material--destroy the superconducting properties in the surrounding areas. Therefore, to maintain superconductivity, the superconductor "tries" to keep these tubes in one place (the weak areas), and does not allow them to move. Because the flux tubes would move if the superconductor is moved in any spatial direction, the superconductor stays "locked" in space. This is why the experimenter can move the superconductor and the resulting position also becomes locked. So no, Tony Hawk and Christopher Lloyd did not crack the quantum conundrum of taking something like levitation and applying it commercially. At the same time, it's pretty amazing that a rough analogy for the hoverboard is actually real science--mind-blowing to learn about as it is to watch. Oh, and it's pronounced GIGA-watts, not JIGGA-watts, Doc. --
This post was adapted from an earlier post from my first blog, Science-Based Life.
