Flights of fancy
Celebrating 100 years of superconductivity
1 May 2011
So, is it possible? Could we levitate and smoothly float above the ground, as if on a wave in the ocean? The answer is yes...and no
Last year a scientific colleague came into my lab and asked, “Julien, do you think the floating mountains in the science fiction movie Avatar will ever exist?”
If the question hadn’t come from a top astrophysicist, well known for his deep understanding of his branch of physics, I probably would have laughed in his face, and then fired him. But not only was he a good physicist, but he was well known for giving amazing lectures about what is right and wrong about the science in SF movies, such as the light saber in Star Wars. So though it was a pretty weird question, I thought I should take it seriously.
Why did he come to me? Because I’m a physicist who specializes in superconductivity. With superconductivity, you can make things levitate – or to be more accurate, you can make magnets levitate. In the movie Avatar, the mountains were indeed supposed to be made of superconductors, and therefore able to levitate at about hundred meters off the ground.
I faced a similar question not long before that, when the French TV channel TF1 asked me if I could help them make famous guests levitate on superconducting surfboards about a meter above the floor for a Saturday evening show.
So, is it possible? Could we levitate and smoothly float above the ground, as if on a wave in the ocean? The answer is yes...and no.
Yes, it is possible, as seen in the main picture at the top right of this article where I have used a small magnet and put it on top of a superconductor (the black disc below).
Even more incredibly, this levitation is stable and can be turned – even upside-down, as shown in the third picture.
This same property can even be used to make a levitating hula hoop, as in the video below.
And yes, you can put heavy things on top of the magnet: a real human being, for example – even one as heavy as a Japanese sumo wrestler. Superconductors are even used to make a train levitate in Japan; it is the fastest train on earth since there is no friction with the rails.
But no, we can’t make things levitate at 100 meters, or even one meter, from the source. Only a few centimeters are possible. Even worse, not only can we not levitate objects very high, but we also have to cool down the superconductor for it to work – to a very chilly minus 150°C.
Why? This question is one of the most fascinating and most studied in the last century in physics. It all started exactly 100 years ago, in 1911, when a great Dutch physicist, Heike Kamerlingh Onnes, discovered an unexpected property inherent in most metals. Take aluminum, for example: cool it as much as you can, and then suddenly, it will conduct electricity absolutely perfectly. A humble metal such as aluminium has suddenly become a superconductor, so much so that if you would put an electric current into a superconductor ring, it would circulate in it forever even after disconnecting the battery. And at the very same moment, if you introduce a magnet nearby, it will be repulsed from the superconductor, and levitate indefinitely.
The reason this happens is due to quantum physics: all of the electrons present in the metal suddenly “dance” together in a collective fashion and become something else, a new state with amazing properties. But the way the electrons dance together is still a subject of research. More than thirteen people have been awarded a Nobel price for working on this subject. And many others are still working, trying to understand and improve these superconductors – including me and my own team in Orsay, for the past fifteen years.
After all of this hard work, we hope that one day we will discover precisely how these superconductors work and how to make them work at room temperature. When this day comes, the levitating mountains of Avatar will not be science fiction anymore – except that they’ll still be a lot closer to the ground than Hollywood would have us believe.
The author is one of the scientific advisors on www.superconductivity.eu, a website put together by the superconductivity community in honor of one hundred years of the science. On it, you can find amazing videos, animations, games, history, applications, current research and explanation of how the phenomenon works that are accessible to everyone. Do check it out!