# Mathematician Designs Time Cloak That Uses Just Light And Mirrors

You know what the futurists are always saying: time cloaks are so cool, but they’re so complicated. And it’s true! What were you expecting from a device that literally hides moments in time? A mathematician has just shown, however, it doesn’t have to be quite so hard after all.

Miguel Lerma just published a paper describing a new, simple kind of time cloak. Imagine you’re looking at a clock. Without a time cloak, the hands move steadily on their appointed route, but with a cloak in place, it would appear to skip seconds or even minutes. Previous models for a time cloak create that jump by bending or expanding light around the cloaked event using lenses, though the first successful such time cloak created an event that lasted just 120 nanoseconds.

But why use lenses when mirrors will do the job more simply? Lerma’s theoretical model does just that, using mirrors to bounce light directed at the clock an extra distance to create an effect of the light slowing down. The MIT Technology Review explains the effect:

This extra distance essentially slows down the lights before it hits the clock. After it has been reflected, the light can be speeded up by avoiding the diversion so that it does not travel the extra distance.

This creates a gap during which any change the clock cannot be seen. However, an observer watching the clock sees it jump in time without any change in illumination.

Bouncing light off of mirrors to create a jump in time? That sounds scientifically and, yes, mathematically fascinating. And you know what else? It sounds like the perfect way to stage a jewellery heist. [Technology Review]

Picture: astroshots42/Flickr