Limit physics to prevent invisibility fabric technology

US researchers have demonstrated that there are basic physical limitations that make invisibility cloaks nearly impossible.

According to Business Insider, current technology can develop invisibility cloaks that make objects invisible at a certain range of electromagnetic wavelengths - such as the light of a human eye or radio waves. But it is very difficult to make invisibility cloaks to shield objects in front of multiple waves.

"There are strict restrictions on covering an object with a passive material and making it invisible, with an arbitrary wavelength and viewing angle , " said Andrea Alu, a researcher at the University of Texas at Austin, USA, said.

The passive materials that Alu mentioned have special properties that enable them to invisible objects without taking energy from external sources, such as the mechanism of metamaterials that have the ability to bend or steam. light receptor.

To determine the limits of these materials, engineers use Bode-Fano theory to match broadband ranges. Simply put, they will consider the magnitude of the object to be covered, the range of electromagnetic waves projected to the object and based on the type of passive material used to calculate whether the material is effective.

It is very difficult to get the Harry Potter invisibility cloak.(Photo: Warner Bros).

According to the results, we can invisible small objects but it is almost impossible to invisible to large objects.

"We have shown that it is not possible to eliminate the light scattering of a tank or aircraft at the visible light frequency range using available techniques based on passive materials," Francesco Monticone, one in the research team, said.

"However, with objects comparable in size to the electromagnetic wavelengths coming in (for example, radio receivers or noseheads of some optical microscopes), we find that it is possible. doing something useful, when the limits are relaxed and we can quantify them. "

The reason why the team decided to try to find limits in making invisible objects is because they want to improve invisible devices as quickly as possible.

Understanding the real limits for further research is better than not actually trying to build an invisibility cloak that can disappear a person.

The University of Texas research team is looking to overcome these limits.

"Our team and other groups are working on active and non-linear stealth techniques , outside the scope of the limits , " Monticone said.

"With the active invisibility cloak , Einstein's theory of relativity also basically limits stealth performance," Alu said. "However, with new concepts and designs, such as active and nonlinear metamaterials, the need for transparency and invisibility can have new advances."

"In addition, we are aiming for other forms of invisibility more easily, such as phase-delay devices of transmitted light, or camouflage techniques or optical tricks that give an impression of clarity. transparent without really reducing the overall scattering of light ".

Although progress has been slow, researchers have also shown that they can stealth micro objects and use lenses to bend light a bit around large objects.

A Columbia University research group has also designed a radio shield device that could theoretically protect the Earth from alien life forms. This study was published in the Optica magazine in July 2016.