Gregory J. Gbur—
Invisibility—the ability to make something invisible to visible light—has long been assumed by science to be impossible. This changed in 2006, when two groups of researchers published back-to-back papers in the journal Nature demonstrating theoretically that invisibility is, at the very least, plausible. Since then, there has been intensive research on a variety of different ways in which invisibility might be achieved. So far, a practical demonstration of true invisibility has remained elusive, and it is unclear when, if ever, it will be achieved.
With that in mind, maybe it is worthwhile to turn to science fiction for ideas. Long before it was science fact, invisibility was a regular topic of science fiction, and many famous authors imagined their own ideas of how invisibility might be achieved. There are many more invisibility stories than most people are aware of. We may not find the secret to being unseen in them, but these stories give a fascinating snapshot of the science of their time.
We begin with the most famous of all stories: H.G. Wells’s 1897 novel The Invisible Man. Wells told the story of a scientist named Griffin who imbued himself with invisibility and found that being invisible all the time is in fact quite a problem, and his struggles inevitably lead him to madness.
To explain how his invisibility is achieved, Wells talks about exposure to a new type of rays, similar to “Roentgen rays,” also known as X-rays. X-rays were discovered in 1895, and their ability to “see” through almost anything led many people to associate them with actual invisibility. Some unscrupulous people started selling X-ray proof underwear, to block the prying eyes of creepy scientists! Wells certainly knew that X-rays and other rays do not convey invisibility, but he was aware of the popular perception and used that to lend his story some plausibility with the public.
X-rays have been a common ingredient of science fiction invisibility ever since. In 1897, Jules Verne wrote The Secret of Wilhelm Storitz, about a man who uses the power of invisibility to stalk a woman he is obsessed with. Verne, almost certainly inspired by Wells, also obliquely refers to Roentgen rays as the source of invisibility. In the 1931 tale “Raiders Invisible,” by D.H. Hall, an American pilot faces off against unidentified but unmistakably Soviet agents who are using X-ray invisibility to sneak onto and sabotage military dirigibles.
Other unseen rays have been used as an explanation for invisibility. In the early 1800s, infrared and ultraviolet light was discovered, with wavelengths lying just outside the visible spectrum. In 1893, Ambrose Bierce became the first to use these rays to explain an invisible monster, in his story “The Damned Thing.” In the story, a man is murdered by an unseen foe. The inquest into his death eventually turns up his journal, which concludes with the revelation, “The human eye is an imperfect instrument; its range is but a few octaves of the real ‘chromatic scale’ I am not mad; there are colors that we can not see. “And, God help me! the Damned Thing is of such a color!”1
Ambrose’s idea became a standard invisibility explanation for decades to come. In the 1930 story “The Cave of Horror,” by Captain S.P. Meek, a rash of disappearances occur in Mammoth Cave, Kentucky, leading the military to investigate. They find that a monster has emerged from the deepest parts of the cave that can only be seen in ultraviolet light. In “Terrors Unseen,” written by Harl Vincent and published in 1931, a scientist creates robots that are visible only through ultraviolet light, and promptly loses control of them. In the surprisingly apocalyptic 1939 novel Sinister Barrier written by Eric Frank Russell, scientists discover a way to see into the infrared and discover that humanity has been controlled and feasted upon by invisible beings for ages.
Ultraviolet radiation is also responsible for sunburns, and Thorne Lee brought that idea into his 1943 tale of the unseen, “Ghost Planet.” When the Earth is attacked by unseen foes, the President sends a space expedition to track the perpetrators to their lair. The expedition discovers a planet that is entirely invisible, including every living being upon it! At first, the explorers find themselves captured, but they manage to escape once they are exposed to the rays of the alien sun, which gives them a sunburn conveying invisibility.
Other stories are noteworthy for their unique visions of invisibility. In Anthony Pelcher’s 1930 story “Invisible Death,” an inventor is found murdered and his mysterious invention goes missing. Soon after, threats are made against the inventor’s employers by a figure who calls himself “Invisible Death.” The invention is later revealed to be an invisibility device that produces invisibility by vibrating the atoms of its user fast enough to make them unseen! It is inspired by the spinning spokes of a bicycle wheel, which are too fast to be seen in motion.
In a more heroic turn, Eando Binder published a story in 1939 called “The Invisible Robinhood,” about a man who invents an invisibility suit and uses it to strike terror into organized crime. His suit is an electrified metal mesh, that “kicks” light photons that hit it around the outside of the suit and sends them on their way. Binder appears to have been inspired by the photoelectric effect, successfully explained by Albert Einstein in 1905 and one of the great breakthroughs in quantum physics. In the photoelectric effect, light shining on a metal surface kicks electrons off the surface. It was not a great leap for Binder to imagine the electrons moving along the metal and releasing a photon again at another location.
My favorite invisibility description was given by A. Hyatt Verrill and published in 1927. In his lighthearted story “The Man Who Could Vanish,” a scientist invents a method of invisibility and embarks on various hijinks throughout the city. His invisibility is based on heterodyning: the mixing of signals of two different frequencies to produce a higher or lower frequency output. Heterodyning is used to produce the audible output signals in radio communications, as the frequencies of the radio waves themselves would be too high to hear if converted directly to sound. Verrill imagined his invisibility device taking input light and shifting its frequency higher or lower, so that it can pass freely through the body. Then, on the other side of the body, its frequency gets shifted back to visible light so it can go on its way.
Most of these ideas are entirely fanciful invisibility schemes. A number of authors, however, came close to imagining invisibility cloaks the way they are actually envisioned to work: they are structures designed to guide light around a central hidden region and send it on its way. The author that came closest is Algis Budrys, who wrote the 1962 story “For Love.” In the story, aliens have camped for decades on the Earth to repair their massive spaceship, driving humanity underground in the process. The U.S. military designs an Invisible Weapons Carrier, a vehicle that can deliver a fusion bomb to the alien craft. The Weapons Carrier is covered with fiber optic cables that convey light from one side of it to the other, leaving the craft virtually undetectable except at close range.
Invisibility cloaks have been shown by science to be in principle feasible, but we are not yet close to making a device that produces practical invisibility. Though most of the science fiction stories we have discussed have invisibility schemes that would never work in practice, there are plenty of other stories out there that haven’t been read in ages. Perhaps some science fiction author has imagined a key piece of the puzzle of invisibility, and their story is just waiting to be rediscovered?
- Bierce, Ambrose. “The Damned Thing.” Town Topics (New York), December 7, 1893.
Gregory J. Gbur is professor of physics and optical science at the University of North Carolina at Charlotte. He is the author of Falling Felines, Fundamental Physics, and most recently, Invisibility: The History and Science of How Not to Be Seen. Gregory also writes two blogs on horror fiction, physics, and nature. He lives in Charlotte, NC.
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