A jealous, violent ex-husband, bent on revenge and seemingly capable of anything, pursues and terrorizes his former spouse. Oh, and for some reason, he’s invisible.
This is the premise of The Invisible Man, the new thriller starring Elisabeth Moss in theaters today. A modern twist on H.G. Wells’ classic science fiction novel, the film offers new twists on the classic horror trope of an unseen foe. Handprints appear on a shower door. A bucket of paint offers a clever jump scare.
The superpower kind of invisibility that makes this story scary—allowing the villain to lurk unseen in the middle of a room or grab his victims unaware—remains far in the future. But the real science of making things invisible has come a long way since Wells’ 1897 book. Scientists have devised materials that bend light around an object, effectively causing it to disappear. They’ve used cameras to record and project images of what’s behind an object onto the object’s surface, making it appear like it’s not even there.
These technologies are far from perfect. Society has neither Harry Potter-esque invisibility cloaks nor potions that would turn the human body see-through. Today’s cloaking technologies might hide something from view, but only at certain angles. In other cases, they blur the background in a way that’s easily detectable or might work only for static objects. But invisibility tech keeps getting more clever.
How to Disappear Completely
One way of making something disappear involves four lenses spaced just right. Scientists from the University of Rochester figured out this relatively low-tech solution. The lenses bend light in a way that creates a blind spot between them, curving light rays around a ruler, hand, or some other small object, rendering it invisible when viewed through their aperture.
But the setup has a key flaw. Move your hand back and forth out of the blind spot, or simply take your eyes away from the lens, and the spell is broken. This is a problem common to most of the modern technologies that are called, somewhat misleadingly, “invisibility cloaks.” Most of them work from just a narrow range of angles or wavelengths of light.
For example, another invisibility tactic, similar to that used by the Rochester researchers, involves metamaterials, so named because they possess properties not found in nature. Some metamaterials can bend light, and a metamaterial cloak could effectively curve incoming light around an object behind it, making it appear to disappear. The drawback (at least for the moment) is that they only work for a single wavelength of light, says José Azaña, a researcher with Canada’s Institut National de la Recherche Scientifique who studies fiber optic communications and photonics.
“In reality, what we are dealing with when we see an object is white light, so it has all the possible colors together over the whole spectrum,” he says. Thus, an “invisible man” cloaked in a garment of metamaterials wouldn’t make it very far out of the lab.
There might be a simpler way, however. Canada-based Hyperstealth Biotechnology has created a thin sheet of material capable of bending light to create the same kind of invisibility effect. The material, called Quantum Stealth, works with all wavelengths of visible light, and it works by bending light coming from the background on both sides toward the viewer to create a blind spot in the middle.
“You get the background that is to the left of me appearing on the right of the material and the background that’s to the right of me appears on the left of the material. And in that overlap zone in between those two you can actually hide a target in the middle,” says Guy Clark, Hyperstealth’s CEO and Quantum Stealth inventor.
But there are drawbacks to this invisibility cloak, too. Objects need to be a certain distance behind it to disappear and can reappear if they move too far to one side. Current prototypes also create a blurry background, though Cramer argues future versions will fix that issue. He envisions the technology being used for police riot shields or to hide tanks on a battlefield. Someday.
See Me Now?
In his own work, Azaña has taken a different approach to invisibility. His “spectral cloaking” device relies on the fact that some objects allow certain electromagnetic wavelengths (but not all) to pass through. He and his colleagues designed a system that modulates incoming light so it’s made of just the wavelengths that pass through an object and then changes them back to the original wavelengths afterward. Because the incoming light never interacts with whatever it passes through, the object would be invisible.
The drawback of this method? Well, spectral cloaking works for any wavelength of light, but only from a single angle, according to Azaña. Viewed from a different perspective, a cloaked object would be invisible no longer. Our invisible man might conceal himself when he’s running at us, for example, but take a step to the side and he’d pop into view.
To find a more robust form of invisibility, we might look to what’s called “active camouflage,” a topic of particular interest to military researchers. The idea is similar to the tactics that make octopuses and cuttlefish invisible. By matching their skin to the background behind them, these cephalopods blend in almost seamlessly. The same could be done for humans with cameras and a suit or cloak that projects images. Imagine a 360-degree camera paired with a body suit covered in OLED pixels.
That’s just a fantasy for now. While some researchers have attempted to design prototype active camouflage suits, the results fall far short of invisibility. The suits don’t disappear entirely, and it’s unclear how they respond to rapid movement.
True invisibility, the kind that would let you walk unseen through a room, is impossible today. But in the more than a century since H.G. Wells dreamed of an invisible man, we’ve proven the concept is more than just a figment of the imagination.
“Today we could say it’s not simply restricted to science fiction,” Azana says. “[It’s] something that makes sense scientifically.”
A multidirectional `perfect paraxial’ cloak using four lenses. From a continuous range of viewing angles, the hand remains cloaked, and the grids seen through the device match the background on the wall (about 2 m away), in color, spacing, shifts, and magnification.
(J. Adam Fenster / University of Rochester)
#Nature | https://sciencespies.com/nature/the-invisible-man-isnt-real-but-this-invisibility-technology-is/
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