What do whales and the invisible man have in common? Waves. Whether they are sound, seismic or electromagnetic, it is waves that determine our ability to perceive our environment, and perhaps soon to protect it.
Absorb the acoustic wave, and the submarine becomes undetectable. Redirect the surface seismic waves to the depths of the Earth, and damage to facilities becomes minimal. Divert electromagnetic waves in the visible spectrum, and you can cherish the hope of becoming invisible.
If this latter application still belongs for some time to the realm of science fiction, the previous ones have either already been applied for decades or are the subject of very promising developments.
Kim Pham, a teacher-researcher at the Unité de mécanique of ENSTA Paris, talks about the research he is conducting on the protection of port infrastructures, with floating structures that play the role of resonance belts capable of transforming a strong swell into a peaceful chop.
He also presents the concept of metaforests, vegetal belts whose very controlled properties, notably in terms of tree height, would allow to reflect seismic waves towards the interior of the planet, and to spare the big urban centers.
Finally, he addresses the question of invisibility, directly linked to that of metamaterials, whose microscopic details could absorb or deflect light in the same way that the dihedrals of an anechoic chamber absorb sound waves.