Combining scientific languages to create an invisibility cloak

An assistant professor at Brussels’ Vrije Universiteit and a visiting professor at Harvard, Vincent Ginis is a brilliant scientist who won a Solvay Award in 2014 and was designated as one of the top 50 tech pioneers in Belgium in 2017. His particular area of study is optics, but he makes a strong case for the combination of different scientific disciplines, or “languages”, to drive progress in research.

As proof of this, he demonstrates how applying Einstein’s general relativity language to the field of optics is being used to figure out how to make an object invisible. You don’t follow? Let’s put it like this: using the curvature of space-time, scientists can find a way to deflect light rays in order to bend them around an object, making it effectively invisible. “In other words, a refractive index - which is a material property of materials that we can engineer - has the same effect on light as the bending of space-time in outer space”, explains Mr. Ginis.

Sounds like science fiction? Well, it isn’t anymore. The main hurdle to overcome was to find the right materials with the right parameters to make that bending of light possible; this is where nanotechnology kicks in. Specifically, the creation of metamaterials, “artificial materials that are engineered on a deep subwavelength scale, smaller than the wavelength of light.” With all the concepts in place, it was just a matter of figuring out how to apply them in real life. The race for invisibility had begun.

The race to invisibility
The first major milestone was reached in 2006. Working with this principle, scientists were able to manufacture the first actual invisibility cloak! Granted, it only worked for light at Ghz frequencies, meaning the hidden object was rendered invisible for smartphones, who communicate in these frequencies, but not for human eyes. But three years later, that hurdle was overcome, and the first invisibility cloak that worked for visible light was developed. The problem this time was that it was smaller than the thickness of a hair, so it could only make invisible objects that are too small to be seen in the first place…

Scaling this up to the human scale was the biggest remaining challenge. Well, you guessed it, that challenge was also met: in 2016, a semi-transparent cylinder was created that could partially hide a cat! Far from perfect, it wasn’t fully transparent and “one could clearly distinguish light refraction - the rainbow effect - at the edges of the device”, but all these subsequent leaps forward meant that creating invisibility is now within reach of the most advanced technologies humans are capable of imagining.

This was all made possible by breaking down the boundaries between scientific disciplines. Quantum mechanics, relativity, thermodynamics, plasma physics, electromagnetism, particle physics, etc. all have their own words and concepts to describe the physical world, and when you borrow the language of one discipline to apply it to another, breakthroughs become possible.

That’s how since 2006, many fields in physics have benefitted from the application of general relativity to areas that have nothing to do with the study of black holes, space travel and the like. In hydrodynamics, this means engineering water waves to redirect tsunamis: plans for several large-scale “water invisibility cloaks” are actually already under construction. Similar installations can be imagined for deflecting seismic waves from buildings, or sound or heat from objects… Invisibility is no longer just about seeing!

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