When browsing through the shelves of a delightful bookstore near my home, I saw a book that was devoted to the science of “Harry Potter”- I’ve seen books on the science of Star Trek, but never Harry Potter, so it was unusual for me to find Michio Kaku’s article, "Small-Scale Invisibility Cloaks".
The whole article sounds like crazy-talk, but is actually true. In 2006, some industrious scientists at Duke University created metamaterials, “which could render an object invisible by absorbing all the light that hits it, but only in two dimensions and only at microwave frequencies”.
Now, very small three-dimensional objects can appear to disappear when under an infrared light if they are placed under an invisibility carpet. According to Kaku, when you put the object underneath the carpet, the bump disappears. He believes that this technology can be applied to larger objects or people as well in the future, which is definitely starting to sound more than a little like Harry Potter. The main reason that the technology is able to work is that infra-red light works at a lower frequency than regular light and has a longer wavelength; when light hits the bump, it bounces off.
Don’t get too excited about the magic carpet just yet, however. Kaku mentions a few things about the technology that show that it isn’t quite up to par with JK Rowling’s imagination yet.
- It doesn’t work with light that you can see yet.
- So far, the object under the carpet is roughly the size of a human hair, so there is quite a ways to go until an actual person can hide under the carpet (or so we are told, anyway!)
- The carpet has a reflection similar to that of a mirror.
The other Invisibility Cloak material that I’m aware of comes from the use of a special raincoat covered with many small beads. Like the “magic carpet”, the raincoat has a mirror-like reflection and involves the use of light to “make the person underneath the coat disappear”. This technology was first developed in the 1960’s- unfortunately, it is limited in that it requires the viewer to look at the raincoat through an apparatus such as a camera or a movie camera in order for the invisibility effect to be complete. The apparatus is necessary because it is only a computer-generated image. For more information on Invisibility Cloaks, HowStuffWorks has a full-range of introductory-level articles on the topic of “Optical Camouflage”.