# Mathematician designs event cloaking device without using metamaterials

Posted August 16, 2013

Mathematician designs event cloaking device without using metamaterialsEnlarge
Basic design of mirror-based event cloak. Credit: arXiv:1308.2606 [physics.optics]

Miguel A. Lerma a mathematician at Northwestern University has uploaded a paper to the preprint server arXiv, in which he describes the design of an event cloaking device that doesn’t require the use of metamaterials. In his design, events are cloaked using mirrors.

An event cloaking device, also known as a time cloak or an invisibility cloak that hides time is a mechanism that causes what appears to an observer, to be a lapse in time during which events have occurred but have not been observed. The idea is based on first slowing down light, then speeding it up again. Doing so causes a lag or gap during which events cannot be observed. Researchers have built such devices using metamaterials that are able to speed up light or slow it down. But those devices have proven to be complicated and expensive. In contrast, in this new method introduced by Lerma, light speed can be manipulated with mirrors by causing it to travel longer or shorter distances before striking an object.

The basic idea involves using multiple mirrors, half of which can be manipulated on-demand to either allow light to pass through or to reflect. The mirrors are arranged in such a way as to first cause light to “slow” by sending it to another mirror instead of directly to an object, which then reflects it to the object. Following that, the light is caused to take a direct route to the source, effectively causing it to speed up again. Doing so creates a “lag” in time, which to an observer would appear as a lapse. If the object were a regular wall clock for example, the observer might see the clock jump from 12:05 to 12:07, if the lag were two minutes. The duration of the lag is dependent on the distance of the mirrors from the light source, thus lags of minutes, hours or days could be caused by placing mirrors on distant planets or spacecraft.

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