How scientists are making the power of invisibility a reality
“In my opinion, invisibility is no longer a science fiction concept.”
For thousands of years, people have told tales of magical beings capable of moving through the world unseen—literally.
From the wish-granting jinn of Arabian folklore to the shadow people of Inuit mythology, creatures possessing the fantastical power of invisibility have long captivated the human imagination. More recently, science fiction and fantasy series have popularized the idea that ordinary humans could become invisible with the help of magical cloaks (Harry Potter), genetic mutations (Marvel superheroes), or advanced tech (Star Trek spaceships).
But is there a science-backed way to produce this most fantastical of illusions? Physicists around the world are working on it.
Researchers have shown that it is at least theoretically possible to create a cloak that can make ordinary objects vanish. Inspired by these findings, other scientists are designing ways to render buildings invisible to earthquakes and concert halls invisible to sound. All these vanishing tricks rely on a similar approach of cleverly steering waves—whether of light, sound, or seismicity—to produce the illusion of empty space.
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And while there are major hurdles to creating the sort of wearable invisibility cloak of our most cherished fantasy stories, some scientists say it’s not outside the realm of possibility.
“The goal is very simple,” says Yun Lai, an invisibility researcher at Nanjing University in China. “The key is how to engineer the material to achieve this.”
Proof that invisibility is possible
Invisibility cloaks jumped from the halls of Hogwarts into the scientific literature roughly 20 years ago.
In the late 1990s and early 2000s, scientists were beginning to develop a new class of materials, called metamaterials, that exhibit strange and extreme properties not found in nature due to the presence of finely engineered microscopic structures. When physicist Ulf Leonhardt learned of their extraordinary optical properties in the early 2000s, he started thinking about how they might be used to achieve the ultimate illusion: invisibility.
“I just thought, This is such a cool thing to do,” says Leonhardt, adding that he was reading H.G. Wells’ The Invisible Man around the time that he learned about metamaterials. “What would it take in order to make that happen?”
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In 2006, Leonhardt and a separate team of researchers at Duke University and Imperial College London published a pair of papers in Science theorizing how to make an invisibility cloak. They imagined that a metamaterial could be engineered with many tiny holes, or other structures, that would steer incoming light waves around the cloak without passing through. Because light would exit the cloak in the same direction that it would have had it not been manipulated, it would create the illusion that light had passed through—and encountered nothing but empty space.
“This is the first time people proved invisibility can be achieved in a scientific way,” Lai says.
Several months later, the same Duke and Imperial College scientists reported building the first such invisibility cloak that could shield an object against microwave radiation in two dimensions. In their experiment, a copper cylinder was “hidden” inside a cloak made up of 10 concentric rings of a material typically used in circuit boards and measuring less than five inches across. The cloak successfully steered the waves around the cloak so that it and the copper cylinder seemed to disappear.
While this demonstration was considered a big step forward, it was clear metamaterials had some major limitations.
For a metamaterial cloak to shield against a particular wavelength of light, the holes need to measure around a tenth of that wavelength, says Sebastien Guenneau, a physicist who studies cloaking at Imperial College London but was not part of the original research team. To deflect visible light waves that are measured in nanometers (a billionth of a meter) would require high-precision nanoengineering.
“You can’t imagine Harry Potter dressed up with this kind of metamaterial—it would cost billions,” Guenneau says.
Another limitation of metamaterial cloaks is that they typically only work for a specific wavelength: A cloak tuned to hide red light won’t conceal objects from blue light, for instance. Steering light around an object takes more time than sending it on a straight path, meaning the waves must travel faster than lightspeed to reach the other side without a time delay. This turns out to only be possible for a single frequency at a time.
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Some researchers have used glass or prisms to create broad-spectrum cloaks for hiding objects from specific angles, showing that it’s not theoretically impossible to achieve. However, metamaterials offer far more promise for sophisticated invisibility technology and, for them, this remains a major challenge.
Ironically, even if a cloak could be engineered to deflect the entire spectrum of visible light, there would be a new problem from the perspective of the wearer. With no light penetrating the cloak, “the person cannot see what’s outside.” Guenneau says. “Harry cannot see Lord Voldemort.”
Cloaking at a distance
Metamaterials are not the only path to making objects vanish. “During my research, I found there are a lot of ways to realize invisibility,” Lai said.
Another option Lai has explored is cloaking objects at a distance by manipulating the scattering of light. Essentially, if a cloaking device is placed at the correct distance from an object, light waves will scatter between the two objects and cancel each other out.
Such a cloak has the benefit of allowing the hidden object to “see” incoming waves. However, Lai says the design is highly complex and may only be practical for low-frequency waves like radio waves rather than visible light.
Other researchers have imagined devices that actively emit waves to cancel out incoming ones—an approach known as active exterior cloaking. In 2021, scientists showed that by encircling an object with a series of heat pumps, the object could be conceaed from a thermal camera, which detects infrared radiation that otherwise isn’t visible to the naked eye. The study also found that heat pumps could be used to give an object a different thermal signature—essentially disguising it as something else.
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“You can make an apple look like an orange,” says study co-author Fernando Guevara Vasquez, a professor of mathematics at the University of Utah.
While metamaterial cloaks have a specific and immutable function, cloaks made with sources of radiation, like heat pumps, can be tuned to different fields. It’s “essentially software control,” Guevara Vasquez says.
Still, anyone using such a cloak must understand the field they want to cancel out in advance. If, say, military officials wanted to hide an object from radar, which relies on radio waves, they would need to know ahead of time what radio frequencies to shield against. Until they figured that out and set up the cloak, the object would be visible, Guevara Vasquez says.
Research on cloaking objects at a distance remains largely theoretical, with some limited experiments. To find invisibility cloaks that are ready to be deployed in the real world, we need to think bigger.
Seismic cloaking
While the microscopic size of light waves makes it inherently difficult to engineer materials that can alter their course, scientists are also interested in shielding objects from much larger waves—such as ocean waves and seismic waves from earthquakes.
This turns out to be much more practical.
“Now you’re making holes on the order of a few meters,” says Guenneau, who has researched seismic cloaks. “You can use any kind of drilling machine—no more nanotechnology.”
Guenneau explains that by drilling a series of concentric holes in the ground around a building that are tuned to match the frequency of incoming seismic waves (which can be predicted by local soil and rock properties), those waves can be redirected. Similarly, concrete columns or rods could be drilled into the seabed to protect an offshore platform from ocean waves. Researchers have been studying these types of large-scale cloaks for over a decade with an eye toward protecting cities, historic sites, nuclear reactors, and even sensitive scientific equipment like gravitational wave detectors.
Guenneau and others have even explored using trees as a natural metamaterial. Research has shown that forests are capable of attenuating seismic waves at Earth’s surface; by spacing trees out at just the right distance, it may be possible to enhance the effect.
While seismic shielding may seem like a far cry from a Romulan cloaking device, this research might never have emerged if scientists hadn’t pursued more science fictional cloaking.
“In my opinion, invisibility is no longer a science fiction concept,” Guenneau says. “It’s something which is extremely useful to improve existing earthquake protection [and] ocean wave protection designs.”
Will fictional cloaks become reality?
While a lightweight cloak that a person can vanish under remains the stuff of fiction for now, the field of invisibility continues to see exciting breakthroughs.
In 2024, Lai and his colleagues proposed a new strategy for getting around the bandwidth limitation of conventional metamaterial cloaks. Using a metamaterial cloak consisting of precisely crafted “acoustic tunnels” that guide sound waves around an obstacle and out an exit surface, the researchers showed that it was possible to produce the illusion that the entire space between where the sound entered and exited the cloak did not exist.
As a result, unlike with conventional metamaterial cloaks, where only a single frequency of light can travel from one side to the other without experiencing a time delay, the researchers demonstrated that soundwaves across a broad acoustic spectrum could traverse the cloak at the same speed.
“We find that if space also disappears, you can easily achieve a very broad band invisibility cloak,” Lai says. While this work is limited to sound waves for now, Lai wants to extend the approach to electromagnetic waves, including visible light.
While some experts are doubtful that the invisibility cloaks of science fiction will ever be practical, Lai believes that seemingly insurmountable barriers will continue to be overcome with more research.
“Maybe one day we can indeed realize Harry Potter’s cloak,” he says. “It’s important to keep pursuing this goal.”
