Cloaking is getting to be all the rage. So let’s seek out a few of the interesting things hiding in this topic.
Successful cloaking - that is, moving light around the object instead of through it, so it is functionally not there for the light’s reflection and refraction - was demonstrated back in October of 2006. For those of us envisioning Predators and Romulans, however, there were a couple of small problems. Specifically it only worked on light coming in along a plane, and it only worked against a single frequency of light - well, radiation, as David Smith and his Duke University colleagues used microwave for the demonstation. Oh, and speaking of predator, that team expected that were you to see it in visual light the cloak would resemble that more than the cloak of the Romulans. That is to say, they believed you would see a distortion - a ripple of some sort - where the cloaked object was.
Then in October of 2008, Igor Smolyaninov and his team at the University of Maryland made a newer version. This one works against light in the visible spectrum. It’s still two dimensional, but it worked in the visible spectrum. It confirmed the distortion expectations of Smith’s team. Oh, and it only worked on a very small object.
At this point I want to fork. The first fork steps into a much larger practical demonstration. Stefan Enoch at the Fresnel Institute in Marseille, France, had one of those “huh. wonder if…” thoughts that sparks so many advances. In this case, he wondered if the cloak would work against physical fluids moving in (for all intents and purposes) two dimensions. So, using the existing literature - both theory behind the above demonstrations plus the demonstrations themselves - he built a much larger cloak. 10 cm in diameter, actually. He and his team tested it in a wave tank. It worked pretty much as it did for light. That is, waves came in, diverted in a bit of a whirlpool effect around the center, and exited. The center remained functionally calm. While Enoch and others believe it may eventually be able to use these to protect shore-lines from tidal waves, an earlier practical use comes in protecting much smaller objects at sea. For example, protection of oil rigs from at least the waves (wind remains untested) of hurricanes and tsunamis seems quite possible. Yes, a cloaking device against weather is still an in-the-lab device, but on a large enough scale that the risks of translating from micro (or nano) to normal are somewhat lessened.
And with that let’s take the other fork. As noted the big problem so far is that light is only cloaked against in two dimensions. Except, well, there are two reports out there which indicate three dimensional cloaks are attainable. Jason Valentine and team at the University of Berkeley report creating a metamaterial that does the trick. Another team from the same University but different department claims the same result with a different material. Both are being challenged by the earlier theorists who believe only two dimensions are possible, but they stand by their results. If either (or both) of the Berkeley teams’ discoveries turn out to work, it just means one more adjustment to theory. We’ll have to see.
So yes, it appears we may be on the verge of being able to hide things in plain sight. As if it wasn’t hard enough to keep track of the car keys anyway…
