Invisibility has long been one of the marvels in science fiction and fantasy—and more recently in physics. But while physicists have figured out the concept for how to make invisibility cloaks, they are yet to build a practical device that can hide human-sized objects in the way that Harry Potter’s cloak can.
Objects are visible to the human eye because they distort light waves according to their shape. We see the objects by registering these distortions when the light from the objects hit our eyes. In a similar way an object can also be visible to a radar, which transmits radio waves or microwaves that bounce off objects in their path.
So far, most invisibility cloaks are made from engineered materials that can bend light in a way that manipulates the eye—or another device such as a radar. However, these typically only work for tiny objects. But that may be about to change. A new experiment has created a cloak that, for the first time, can hide small objects of any shape completely from visible light. The cloak, which is thinner and more flexible than any of its predecessors, can also be scaled up to hide bigger objects—potentially transforming the science into something that can be manufactured and sold.
Messy Metamaterials
The first invisibility cloak was created in 2006 by British scientist John Pendry. It consisted of a material that could bend microwaves, but not visible light, around a tiny, 2D object measuring just a couple of micrometers—making it look like they had traveled straight and never touched the object. Since then, better versions that work for other wavelengths in both two and three dimensions have been created.
