Consider a mirage on a hot toad: when light tays hit the hot ait just above the surface, they bend. Although light moves through a vacuum at a certain constant speed, it moves more slowly through any transparent medium, such as water or gas. Light travels faster in the thin air near the road than it does in the colder, denser air above, and the difference in speed makes it shift direction as it crosses the boundary between the two. Rays once headed downwards from the sky are redirected to your eye, hiding part of the road with a shimmering image.

A research team has constructed an apparatus to cloak an object from electromagnetic radiation (EMR)—in this case, microwaves—making the object "invisible" to microwave-based detection devices, somewhat as a mirage on a hot road makes the road invisible. The apparatus bends incoming microwaves around the object, using a class of recently created metamaterials—materials that gain certain desired properties directly from their engineered structures rather than from their composition. These metamaterials possess the ability, not found in nature, to bend microwaves at extreme angles. The metamateria! in this case—thin, rigid sheets of fiberglass insulator stamped with conducting loops, coils, and tiny rectangles—was designed to control the movement of incoming EMR.