Cloaking Technology: From Electromagnetic Radiation to Space-Time

The idea of a 'cloaking device' first came into being when Star Trek writer D. C. Fontana coined the term, ever since it has played an important role as plot devices in a number of science fiction films.

But let's forget sci-fi and move into reality because that's what cloaking technology is currently doing. Scientists are working to develop cloaking devices that could effectively have the ability to cloak anything from a human to a house, even a city or even an event in time itself.

Let's take a step back. So what is a cloaking device? Basically a cloaking device is an advanced form of stealth that could allow an object to become invisible. Now what do I mean by invisible, in essence a cloaking device makes an object invisible by masking the electromagnetic radiation emitted by an object. A full cloak would mask all types of electromagnetic radiation from x-rays to microwaves, from ultra-violet light to infra-red and visible light (the light that makes up the visible world that humans perceive). A partial cloak on the other hand would have the ability to mask a specific frequency of the electromagnetic spectrum, say for example microwaves. Below is an example of how a cloak would work, in the first image the cloak is inactive and the light that object emits is radiated and can be observed, in the second image the light of the object is cloaked and the object remains invisible.

Inactive Cloak
  





Active Cloak



So far optical metamaterials have been used to cloak micro-objects but only in the microwave range of the electromagnetic spectrum. In other words objects that emit microwave radiation which could make it observable, have this radiation masked, cloaked and become invisible. Okay so perhaps this type of cloak could be dubbed as a glorified type of camouflage but what if you could make events in time invisible. Scientists have once again used metamaterials to do this, with conventional materials light travels through them in a straight line, but with the metamaterials the light can be broken up to leave gaps. When light normally enters a material it slows down but it is theoretically possible that the ray of light could be altered and manipulated so that some parts of it speed up and other parts of it slow down. In space light is normally curved but when light is split like this the leading part of light speeds up and arrives before an event and the latter part of the light lags behind and arrives after the event. It is in this gap that an event could occur that would remain un-illuminated and undetected, it is conceivable that information or even a person could move through this temporary gap undetected.

So let's really complicate the cloak, if we look at our first type of cloak it would be possible for a person to walk into your house and rob you, but unless they cloaked everything that they picked up you would see your laptop floating through the air. However, with the space-time cloak you could be sitting in your house and someone could walk in and reduce your house to rubble and you wouldn't have noticed a thing until the cloak closes the gap in space-time. Food for thought, cloaking devices are closer than you think...