For an experiment designed to reverse time, the equipment was surprisingly easy: little greater than a tank of water. With a puff of air to disturb the floor, Emmanuel Fort created a set of ripples shifting outwards in concentric circles. Then, because the waves unfold, he gave the tank a practised jolt – at which level they instantly began travelling inward, refocusing on the level of origin.

Fort’s work in 2016 was the primary of what has turn out to be a deluge of experiments through which waves are manipulated, managed and even reversed with unprecedented precision. And lately, we’re not simply taking part in with water. Researchers have found out create a spread of “temporal metamaterials” that may manipulate and rewind electromagnetic waves, together with seen gentle itself, with ever larger precision.

The important thing to those weird supplies isn’t a lot the cautious engineering of their spatial association of atoms, however how they work within the fourth dimension, time. Just like the fast jolting of the water tank, temporal metamaterials can transform their properties within the blink of an eye fixed. This creates a type of boundary that acts like a mirror in time – and it’s this that exerts such refined energy over waves.

Not solely are these supplies a mind-bending invention, they’ve additionally turn out to be an unexpectedly wealthy playground through which physicists can take a look at a raft of basic concepts at their limits. What occurs whenever you ship quantum particles by means of a slit in time? Does friction actually exist within the quantum world? And may we…