Metamaterials are substances in which their ability to support electric and magnetic fields can be changed. Fiddle with these properties in just the right way and you can steer electromagnetic waves in all kinds of strange and exotic ways.
The highest profile use of this idea is to build invisibility cloaks but there’s another more fascinating application. It turns out there is a formal mathematical analogy between the way metamaterials bend light and the way gravity does it. Inside metamaterials, electromagnetic space becomes distorted in exactly the same way as spacetime in general relatively.
That means physicists can use metamaterials to simulate the universe itself and all the weird phenomenon of general relativity. We’ve looked at various attempts to recreate black holes, the Big Bang and even multiverses.
But there’s another thing that general relativity appears to allow: faster than light travel. In 1994, the Mexican physicist, Michael Alcubierre, realised that while relativity prevents faster-than-light travel relative to the fabric of spacetime, it places no restriction on the speed at which regions of spacetime can move relative to each other.
That suggests a way of building a warp drive. Alcubierre imagined a small volume of flat spacetime in which a spacecraft sits, surrounded by a bubble of spacetime that shrinks in the direction of travel, bringing your destination nearer, and stretches behind you. He showed that this shrinking and stretching could enable the bubble–and the spaceship it contained–to move at superluminal speeds.
Today, Igor Smolyaninov at the University of Maryland, points out that if these kinds of bubbles are possible in spacetime, then it ought to be possible to simulate them inside a metamaterial.
His analysis makes for interesting reading. It turns out that faster than light travel travel is not possible inside any physically-realisable metamaterial. That agrees with various analyses of Alcubierre’s ideas suggesting that his bubble would be highly unstable and that superluminal travel would be impossible. We looked at one here.
However, Smolyaninov says that subluminal travel is still possible using this method and shows how it ought to be possible to reach speeds of up to a quarter of the speed of light by distorting space in front of and behind the traveller.
That’s not quite warp speed, nowhere near it actually. But it’s a fair rate of knots by anybody’s standards.
It only remains for somebody to actually build a metamaterial capable of this trick. And judging by the rate at which this stuff is being developed, we shouldn’t have too long to wait.