For a time-reversal experiment, the device was surprisingly simple: a small immersion in a tank of water. Emanuel Fort perturbed the surface with a blast of air, creating a series of ripples that spread outward in concentric circles. He then subjected the tank to a gentle shock as the waves spread out. The waves suddenly began to move inwards, refocusing at their point of origin.
Fort's 2016 work was the first of a flood of experiments to steer, control, and even reverse waves with unprecedented precision. And today, we're no longer just playing in water: Researchers have figured out how to create a variety of “temporal metamaterials” that can manipulate and rewind electromagnetic waves, including visible light itself, more precisely than ever before.
The key to these strange materials isn’t the clever spatial arrangement of atoms, but how they work in the fourth dimension: time. Just like a tank of water being agitated, temporal metamaterials can dramatically change their properties in the blink of an eye. This creates a kind of boundary that acts like a mirror in time, exerting very subtle forces on the waves.
These materials are not only amazing inventions, but also an unexpectedly rich playground where physicists can test a range of fundamental ideas to their limits. What happens when you send a quantum particle through a slit in time? Does friction really exist in the quantum world? And do we…
Source: www.newscientist.com
