The military has stealth to hide from radar, but planes, boats and even humvees still leave infrared and magnetic signatures.
The problem: all the electrical systems hooked up to all that metal.
Recently, a team of researchers in China worked to solve that problem. They are developing what they call a "DC Invisibility Cloak"— not an invisibility cloak in the traditional sense, but one that can hide electrical and magnetic signals that are given off by direct current.
As the charged particles that make up direct current flow through something holding an electric charge, say a battery, they create a magnetic field.
The cloaking device was unveiled in a paper in the journal Applied Physics Letters. They say it is the thinnest "nearly perfect" direct current invisibility cloak.
The finding was eloquently described by Carl Franzen in Talking Points Memo:
The cloak that the Chinese researchers successfully tested was made up of a network of resistors, common parts of electrical circuits that are used to reduce voltage, which act in this case as a type of metamaterial, an artificial material that exhibits properties such as bending current or electromagnetic waves, including visible light.
However, the cloak in this case doesn’t affect visible light, instead just hides the static fields produced by direct current and magnetic fields, as PhysOrg reported.
Magnetic and electrical fields are make up the electromagnetic spectrum, which includes all the different types of electromagnetic radiation. Some examples of electromagnetic radiation include things we know, like microwaves and visible light.
Sensors can detect these electrical and magnetic fields, so to truly hide something you would need to silence or block those signals. To do this, the cloak is designed so that the electromagentic waves coming off the cloaked object in the center look the way they would if that object didn't exist. It does this with a series of resistors (electrical components that reduce voltage) that bend electromagenetic waves.
The cloak is also only mono-directional, which means that the illusion would only work from one perspective — say straight above, if you are trying to hide the electromagnetic signature of a buried land mine from a drone. They say this is one of the thinnest of its kind, about a centimeter thick.
Scientists leading the research said the technology has many possible applications, to include disguising weapons systems, like fields of buried mines or artillery batteries, which give off detectable electromagnetic signatures. They also mentioned that understanding how cloaking works will help them design countermeasures, so surveillance systems could unveil cloak users and see what they are hiding.
Because light is a type of electromagnetic radiation, this advance could one day lead to visible-light cloaks — yes, a possible real life invisibility cloak, Harry Potter style.
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