Name: Using Science to Achieve Invisibility
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How do we see objects? By intercepting waves of light bouncing off of them and into our eyes, each reflected at a different angle. One way to achieve invisibility is to bend the paths of light using lenses, mirrors, or metamaterials with unique reflective properties. There are a lot of problems still to be solved—and valuable applications awaiting those who succeed.

Researchers recently made a bunny almost entirely invisible to infrared. But achieving true invisibility is a much more difficult feat.

How do we see objects? By intercepting waves of light bouncing off of them and into our eyes, each reflected at a different angle. One way to achieve invisibility is to bend the paths of light using lenses, mirrors, or metamaterials with unique reflective properties. There are a lot of problems still to be solved—and valuable applications awaiting those who succeed.

Achieving true invisibility is a difficult feat.

Using Science to Achieve Invisibility

Researchers recently made a bunny almost entirely invisible to infrared. But achieving true invisibility is a much more difficult feat.

Physics & Math

Using Science to Achieve InvisibilityPublished: April 5, 2019Onscreen: It's springtime. So why not make a bunny invisible? Researchers made this one invisible to infrared. Infrared radiation is visible through night googles. The warmer something is, the more infrared there is.Hao Bai's team looked to polar bears whose hair traps heat. They made a synthetic material that does something similar and put it on a bunny.Hao Bai: Under an infrared camera, you can barely see the body of the bunny. It’s because… there’s no infrared emission from the bunny’s body out across the fabric.Onscreen: Instead, all the heat is trapped under the cloak. But what would it take to achieve real invisibility?Jose Azaña: The first thing that is important to understand is how you see an object.Onscreen: Waves of light travel from a source to an object. These waves bounce off that object and into your eye — each reflecting at a different angle. One way to achieve invisibility is to bend these paths of light.Azaña: Typically, the waves propagate in a straight line…but in this case, you will be doing something to the wave so that it is curved, and it goes around the object. And in this way, you avoid the interaction between the object and the wave…Onscreen: rendering it invisible.Joe Choi: We used mirrors and a four-lens system to deflect light around a body. You’d be able to see this optical effect where you see around maybe my fingers.Onscreen: Researchers are also using metamaterials to bend light.Azaña: Those are materials that offer properties in their interactions with waves that cannot be found in nature. You take different materials, you put them together in a way that’s not obvious and you can do to the waves things that the natural materials will never do.Onscreen: These metamaterials are super tiny and arranged into specific patterns.Choi: Then you can guide light around a region and that region becomes invisible.Onscreen: Another way of achieving invisibility doesn't bend the light at all.Azaña: We do a kind of manipulation of the properties of the wave so that it can pass through the object like a ghost.Onscreen: Because the detector sees the same light that was emitted, the object seems invisible. Achieving invisibility isn't easy.Azaña: There are a lot of problems still to be solved.Choi: For metamaterials, the main difficulty is they can only really do it for a single wavelength. For ours, the main difficulty is that we have limited range of angles that you can do it. You can’t get everything. That’s the limit of physics.Onscreen: If we manage to resolve these problems, there are larger applications: military operations that require stealth, surgeons who could see without their hands being in the way, and pilots seeing the runway below them as they land a plane.Choi: If you could scale this…maybe a…suit would be more practical… As the suit moves, you know where it’s moving in relation to the suit and you can map the light so that it goes around perfectly so that it just becomes invisible.Azaña: I want to believe that it will take us to a point where we can make it practical…to create invisibility cloaks and invisibility devices.

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Using Science to Achieve Invisibility

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