We've seen lots of steps toward invisibility cloaks that can bend different wavelengths of light and conceal objects. And then there's inaudibility cloaks, anti-vibration cloaks, and time cloaks. Get ready for the latest insane advance in cloaking technology.
Of course, like the rest of these proposed cloaks, the idea is long on theory and short on practical application, at least right now. But Mohammad-Reza Alam, a UC Berkeley fluid mechanician, has an idea for an all new type of cloak that can bend a type of wave very different from those of light or vibration. In this case, Alam says he's come up with a theoretical model in which ships and off-shore structures like oil rigs and buoys could be effectively hidden from the waves below.
As ScienceNOW reports, the idea revolves around how ocean water tends to stratify into two major layers - a cold dense one beneath a warm light one. There are waves that form along the interface between these two layers, rather unsurprisingly known as interfacial waves. Alam's idea is to take potentially dangerous waves on the surface and use the cloak to turn them into relatively harmless interfacial waves. Here's how it would work:
To make that happen, Alam takes advantage of a key difference between the surface waves and the interfacial waves. For the same frequency of oscillation, the interfacial waves will have a much shorter wavelength and lower speed than the surface waves above. That makes it possible to transfer energy from the surface wave to the interfacial wave by placing a patch of wavy ripples on the sea floor in front of the object that have a wavelength that's tuned just right. The precise condition is easiest to understand in terms of "wave vector," essentially one over the wavelength: The wave vector of the ripples must equal the difference in the wave vectors of the interfacial and surface waves.
Admittedly, while this idea works great in ideal conditions, it's a whole other matter to figure out how this could work in the far more complex environment of the open ocean. For more, including a diagram of Alam's proposed cloak, check out ScienceNOW.