Novel cloaking device could shield ocean-faring vessels

Science : A device to protect, or cloak, such objects as oil-drilling rigs and ships floating on the ocean surface is being developed by a researcher at the University of California, Berkeley. Mohammad-Reza Alam, who has published his results in Physical Review Letters, used computer simulations to test his theory. Because ocean water tends to stratify into a colder, denser layer below and a warmer, lighter layer above, waves propagate either along the surface or along the interface between the two layers. Interfacial waves have much shorter wavelengths and lower speed than surface waves, so Alam theorized that before a surface wave reaches a floating object, he could change the wave into an interfacial one, which would pass below the object, by introducing a patch of ripples of a certain wavelength on the sea floor. A second, identical patch of ripples on the other side of the object would turn the interfacial wave back into a surface wave. Although the ocean is much more complicated than the simulations, Alam’s novel approach offers a new twist on cloaking and could inspire a whole new direction of research.