This video demonstrating the power of superconductivity has been making the rounds this week and is an example of how video is really the best way to capture and share with thousands of viewers the amazing power of science!
You will notice that the video is a demonstration without the science explained live. It was a missed opportunity in my opinion. Thankfully, Tel-Aviv University, who is responsible for the demonstration, has posted an explanation of the Meissner Effect as demonstrated by a liquid nitrogen cooled disc composed of a sapphire wafer coated thinly with yttrium barium copper oxide. Supercondutivity and magnetism are usually in opposition to each other. In this case, where the disc is extremely thin, it's possible for the magnetic field to penetrate the disc via tiny flux tubes which somehow (biologist hand-waving here) are what's responsible for the levitation we see over the track. Jump below the video to read their explanation and catch a Quicktime video of the physics.
The explanation from Tel -Aviv University's website:
"Superconductivity and magnetic field do not like each other. When possible, the superconductor will expel all the magnetic field from inside. This is the Meissner effect. In our case, since the superconductor is extremely thin, the magnetic field DOES penetrates. However, it does that in discrete quantities (this is quantum physics after all! ) called flux tubes.
View the Quicktime link to what is happening: Magnetic field expulsion
Inside each magnetic flux tube superconductivity is locally destroyed. The superconductor will try to keep the magnetic tubes pinned in weak areas (e.g. grain boundaries). Any spatial movement of the superconductor will cause the flux tubes to move. In order to prevent that the superconductor remains “trapped” in midair."
Even if the explanation opportunity was missed in the video, the awe inducing wonder of the demonstration will hopefully capture the attention of non-scientific viewers and intrigue them enough to explore further!
Image is courtesy of Tel-Aviv Univeristy http://www.quantumlevitation.com/levitation/The_physics.html