Physicists Create Magnetic Invisibility Cloak
By Kate McAlpine, ScienceNOW
The sneaky science of “cloaking” just keeps getting richer. Physicists and engineers had already demonstrated rudimentary invisibility cloaks that can hide objects from light, sound, and water waves. Now, they’ve devised an “antimagnet” cloak that can shield an object from a constant magnetic field without disturbing that field. If realized, such a cloak could have medical applications, researchers say.
“This will take cloaking technology another step forward,” says John Pendry, a theorist at Imperial College London and co-inventor of the original cloaking idea, who was not involved in the present work.
In fact, shutting out a static magnetic field to protect an object isn’t that hard. All a researcher needs to do is to encase the object in a container made of a “superconductor,” a material that will carry electrical current without any resistance when it is cooled sufficiently close to absolute zero. If the container encounters a magnetic field, currents within the conductor will flow to generate a field that counteracts the applied field. In an ordinary conductor, the resistance of the metal quickly snuffs out those currents. In a superconductor, however, those currents just keep flowing, creating a magnetic field that exactly cancels the applied field and zeroing out the total field within the container.