Remember the possibility of creating invisibility cloaks using metamaterials? While perfect invisibility can theoretically be achieved, one big problem is that light cannot reach inside the cloaking device, preventing anyone from seeing the outside. No surprise there, since it works by diverting the incoming light waves away from the inside and then putting them back on their original course.
However, it turns out that blocking out the waves can itself be a very useful thing. Not so much for light, where a cheap box would do. Instead, someone remembered that light is not the only thing that is made up of waves. Earthquakes cause seismic waves through the ground which shake things up and even destroy buildings, and an “invisibility cloak” that worked on seismic waves would protect the inside from earthquakes. The weakness of an invisibility cloak can end up being its strength! And since cloaking would not be the goal here, there is no need to even attempt perfect invisibility in seismic waves and should be a lot easier to do.
Researchers from the University of Liverpool figured out how such an invisibility cloak for earthquakes can be constructed out of concentric rings of plastic. It is only a theoretical design so far, but hopefully it could be applied in the real world in the not too distant future. Even if it never becomes practical, it is still pretty neat how the idea of an invisibility cloak can be turned on its head.