Harry Potter and the metamaterials

In 1997, after returning from a conference hosted by the Defense Advanced Research Projects Agency in the United States, Sir John Pendry discussed the talk he had delivered there with his wife over dinner. "That's like Harry Potter," she exclaimed.

Pendry, a physicist at Imperial College London, was then unaware of the Harry Potter books. At the conference, he had speculated about a material that could bend light and render objects invisible — much like the invisibility cloak that figured in the Potter series.

These materials are not entirely new. But researchers have now crafted unique geometric designs on conventional materials, making them behave in unusual ways. These materials, which can bend and manipulate light, sound, and even seismic waves, are called metamaterials. Their innovative uses range from war strategies, advanced sensors and superfast electronics to ultra-thin mobile phones, sound systems and more efficient energy harvesting.

Since Einstein's time, it has been known that bending space affects electromagnetic fields. Pendry and his team discovered that by "distorting" space — similar to stretching a rubber sheet — they could control these fields and design the necessary properties for metamaterials. Pendry extended this idea to make objects invisible by creating a "hole" in a material and directing light and electromagnetic waves around it. This concept of cloaking is now applied across various electromagnetic spectrums, allowing objects to be hidden not just from the human eye but also from radio and infrared waves and X-rays.