The ability to become invisible has long been one of the most compelling devices in science fiction, in part because the potential applications are mind boggling. But is invisibility within the realm of possibility in the real world? It turns out that a sort of inside-out approach has scientific value that could bolster the effectiveness of invisibility technologies.

Researchers from Spain last year proposed that the electromagnetic properties of specific materials could possibly make some objects invisible if applied from the inside. To make the proposal easier for non-scientists to understand, one of the researchers cited popular fiction; he explained that this new theory draws from the experiences of the lead character in H.G. Wells' "The Invisible Man," who used a potion to create an invisibility cloak, rather than borrowing from the external device that made J.K. Rowling's Harry Potter seem like he wasn't really there.

In other words, if the Spanish researchers' theory can ever be successfully applied on a large scale, humans or aircraft could cloak themselves from within and be invisible — like Wells' invisible man — but still be able to see and interact with the world around them, which Harry Potter couldn't do if his cloak covered his eyes.

To See But Not be Seen

Published in Scientific Reports, the Spanish researchers' theory hangs on the principles behind plasmonic cloaking, which is when the interaction of light and metal nanostructures creates electrical currents that make a device invisible.

In 2012, Stanford University engineers announced they had used plasmonic cloaking to show that a coating of reflective metal can "create a device that can see without being seen — an invisible machine that detects light,#Bib1" said Science Daily. Essentially, they painted the silicon nanowires of a semiconductor with gold; the light from the metal and silicon canceled each other out, making the device invisible but still able to detect light.

The recent proposal by the researchers in Spain builds on the Stanford study but posits that the interaction could happen from inside an object by using certain fillers. "Although we all have in mind the invisibility cloak of Harry Potter (that) is the model that other scientists have used to make things invisible â€¦ the idea of potions that was suggested in the work of 'The Invisible Man' by H.G. Wells has not been proposed," one of the researchers said in an article published by the University of Extremadura, where he and his colleagues are studying.

Relying on a Harry Potter—style cloak has limitations, researcher Alberto Serna implies. That type of invisibility relies on light dodging the cloaking device, which means it doesn't work as effectively when the object has contact with light, he said.

Envisioning Invisible Things

Serna and his colleagues acknowledge that their theory can be applied only to small objects — and that it's entirely hypothetical. But they believe it opens the door to a number of possibilities, including gains in bioengineering and communications, although they don't specify how those or any other fields would benefit. "'[T]he fact that the object can 'see' the exterior without external layers preventing or hindering vision is novel and promising,'" Luis Landesa, the head of the research project, said in the University of Extremadura article.

The researchers don't want the filler-based method to replace an external cloak, which they admit performs better "compared to the results of our paper," but they believe it could be a plausible alternative for situations where an external device would interfere.

Nonetheless, between their research, the Stanford study and other tests — including Northrop Grumman's work in the field — these advancements reveal the promise of invisibility technologies.

Pretend for a moment the filler method is able to achieve invisibility on a large scale. Aircraft could fly undetected and without any cloaking device obstructing the pilot's view. Yes, that would give the world a "Wonder Woman" jet. And who knows what good (or bad) invisible people could do for society. On a smaller but still significant scale, fillers could help medical technologies fight disease or shape still-unimagined devices that could exponentially increase computing power.

But we'll have to wait and see — until we can't see it.