Bending Light the Wrong Way

The refractive index is a measure of how much light slows down when it enters a medium. Conventional materials have a positive refractive index that is normally greater than 1. In his Perspective, Wiltshire explains how Shelby et al. were able to defy convention and make a negative refractive index material without violating the laws of physics. Such materials may enable the fabrication of the perfect lens.