The bending of light by the sun was first demonstrated in 1919 by Arthur Eddington during an eclipse, but bending space ourselves is not so easy. It takes an enormous amount of matter or energy to warp space, like the presence of a star or a black hole. We do not yet know how to obtain and control that much energy, and so cloaking by diverting light is still a distant prospect. This also means that the Invisible Woman—Susan Storm of the Fantastic Four universe—must remain in the realm of fiction for the foreseeable future.

1. Cloaking 

The idea of making something invisible by bending light is so captivating that, despite the obstacles, scientists continue their attempts to create the effect. And that includes me.

The figure shows how rays of light would pass through a metamaterial “invisibility cloak.” The metamaterial occupies the region between the outer shell and the inner core (not shown). Items placed inside the central sphere are invisible since light rays can never reach them, instead being routed through the cloak and restored to their original trajectories as they exit.
The figure shows how rays of light would pass through a metamaterial “invisibility cloak.” The metamaterial occupies the region between the outer shell and the inner core (not shown). Items placed inside the central sphere are invisible since light rays can never reach them, instead being routed through the cloak and restored to their original trajectories as they exit.
Image: Dr. David Smith

Our group at Duke University, in collaboration with theoretical physicist Sir John Pendry, suggested and later demonstrated one method using a special type of material called a “metamaterial.” Metamaterials are human-made materials with little circuit-like elements—conducting rings and wires, for example—that mimic the properties of atoms and molecules of conventional materials.

Rather than physically warping space, we can use the idea of warping space to find a recipe for a material that will have the same effect. In this way, we can design an invisibility cloak just by picturing the way we would like waves to circulate around the cloaked object. This is a technique called “transformation optics.”

Light—or, in the case of our experiment, microwaves—are redirected in a metamaterial cloak, appearing to bend or flow around the cloaked object. They are then restored on the other side as if they had passed through empty space. The metamaterial cloak is a real device that forces light to flow exactly as it might around a cloaked Romulan ship, which means this type of invisibility device is plausible.

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Science fiction helps us begin to understand how things that don’t exist yet might change the future of humanity. In fantasy, we must often suspend our belief of what is scientifically possible; in science-fiction, we challenge it. The question is not if something is possible, but more if it is feasible. Sometimes that smallest feasibility can eventually be transformed into reality, and when that happens, we will be ready for it, thanks to science-fiction.

As the great science-fiction author Arthur C. Clarke wrote, advanced technology can seem indistinguishable from magic.

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