Metamaterial Reveals Nature of Time and the Impossibility of Time Machines

Metamaterial Reveals Nature of Time and the Impossibility of Time Machines

By recreating the Big Bang inside a metamaterial for the first time, physicists have shown why the cosmological arrow of time points in the same direction as the thermodynamic arrow of time

Metamaterials are periodic structures that can be engineered to steer light in specific ways. The trick is to manipulate the properties of the "electromagnetic space" in which light travels by controlling the values of the permittivity and permeability of this space.

In recent years, physicists have had a great deal of fun using metamaterials to build all kinds of exciting devices, the best known being invisibility cloaks which steer light around an object, thereby concealing it from view.

But metamaterials have a more profound application because there is a formal analogy between the mathematics of electromagnetic spaces and the mathematics of general relativity and the spacetime it describes.

That means it is possible to reproduce inside a metamaterial an exact copy of many of the features of spacetime. We've looked at a number of these ideas, such as how to build a black hole and even create a multiverse.

Today, Igor Smolyaninov at the University of Maryland, College Park, says it is possible to recreate the arrow of time inside a metamaterial. Such an experiment, he says, allows the experimental study of one of the great outstanding mysteries in science: why the cosmological arrow of time is the same as the thermodynamic arrow of time.

At the same time, the exercise gives a curious insight into the potential for time travel.

The arrow of time is a long standing puzzle. Many cosmologists believe that the Universe began with the Big Bang, an event that is clearly in our past.

And yet our standard definition of time comes from thermodynamics and the observation that entropy always increases with time. For example, you can easily break an egg or mix milk into your tea but reversing these processes is hard. Observing phenomena like these defines the arrow of time.