Yet another story that features the physics of invisibility, continuing my series of posts inspired by the research into my upcoming book on the history of invisibility physics!

A secret race of mutant humans, gifted with superpowers, hides out from the bulk of humanity that hates and fears them and seeks to exterminate them utterly.

If this sounds familiar, you might be thinking of the classic Marvel comics series X-Men, but in this case I’m referring to the much earlier novel by A.E. van Vogt, Slan, first published in serial form in 1940 and then made into a book in 1946. (Image from the contemporary edition that I read.)

Slan is a classic of science fiction, and A.E. van Vogt’s first novel. Like many serialized stories of the time, it is a fast-paced tale with lots of twists and turns (and things that don’t completely makes sense if you think about them too much). I was drawn to read it because it includes a description of a spacecraft with what amounts to a cloaking device!

Slan is set at an unspecified point in the future, where technology is significantly ahead of our own (at least as far as science fiction writers of the 1940s could imagine). The world is now a dictatorship, run from the city of Centropolis by the ruthless Kier Gray.

Centropolis was originally built several hundreds years earlier by the Slan, mutant humans who possess superior strength and intelligence as well as telepathy. Those long centuries ago, the Slan managed to take over the world, prompting a murderous backlash from humanity that drove the Slan into hiding. Since then, they have been hated, feared, and slaughtered by humanity whenever they appear.

As the novel begins, nine year old Jommy Cross loses his mother to the secret police. Jommy is forced to find a way to survive to adulthood on his own, as he knows of no other Slan that can help. Fortunately, as a Slan, Jommy is far more intelligent and strong than any human his own age. Jommy lives in hiding until he becomes an adult, when he begins the search for technology that his father invented and then secreted away, technology that could save the Slans. But Jommy is faced with another mystery: where are the surviving Slans? Or are there any left?

The novel follows two characters. Jommy is the principal protagonist, and it is overall his tale. The book also tells the story of a young Slan woman named Kathleen Layton, who is kept alive in the palace of Kier Gray as an “experiment” to see whether Slans can be rehabilitated. But not everyone is in favor of letting any Slan live, even for a little while, and there are forces in the government even more ruthless than Gray. Kathleen must survive and manipulate palace intrigue in order to survive.

As Jommy grows up, he finds his father’s secret: new atomic technology that can be used to power a spaceship or as a disintegration ray. Jommy, who finds himself not only being hunted by ordinary humanity but by a third species of humans, uses this latter ability to create an ingenious form of stealth technology for his own spaceship:

Completely invisible, traveling many miles per second, his ship headed to Mars! He must have hurtled through mine fields, but that didn’t matter now. The devouring disintegration rays that poured out from the walls of his great machine ate up mines before they could explode, and simultaneously destroyed every light wave that would have revealed his craft to alert eyes out there in the blaze of sun.

What I really love about this explanation is that it sounds strikingly like van Vogt is describing invisibility through wave interference, which is an actual way that some invisibility schemes work! A bit of background: because light is a wave, it possesses up and down “wiggles” as it travels. When two or more light waves cross paths, they “interfere” with each other. If two waves combine with both of them wiggling “up” at the same time, they produce constructive interference, and make a bigger wave. If two waves combine with one “up” and one “down,” they produce destructive interference, and can partially or wholly cancel each other out.

This phenomenon of interference was the earliest definitive proof that light in fact possesses wave-like properties, as Thomas Young showed using his famous two-pinhole experiment in the early 1800s.

Much later, theoretical physicists realize that it is possible for three-dimensional sources of radiation to produce waves that destructively interfere everywhere outside the region of the source itself. These objects are, paradoxically, sources of radiation that produce no radiation, and are called nonradiating sources. They were first described in the early 1900s by Paul Ehrenfest, and have been rediscovered and studied by numerous researchers over the years, including me in my PhD work! These nonradiating sources are a sort of “invisible” object, as they produce no detectable radiation, and more traditional invisibility can be described using mathematics analogous to the mathematics of nonradiating sources.

Van Vogt’s “great machine,” producing disintegration rays that “destroy” light waves, sounds very reminiscent of nonradiating sources to me! Of course, van Vogt didn’t have that science in mind when he wrote his book, and his description of the effect switches from waves to particles in the very next paragraph, but it is fascinating to see how close he got to correctly imagining some very strange optical science. (If you want to read more about nonradiating sources, I will discuss them extensively in my invisibility book when it comes out.)

As I have said, Slan is a novel filled with twists and turns, and unexpected surprises. By the end of the novel, a number of major mysteries are solved, explaining the history of the Slan and what happened to them. The novel is complete and satisfying in and of itself, but does end on a bit of a cliffhanger. Where the novel ends, the Earth is on the verge of an interplanetary war!

Van Vogt sketched out plans for a sequel much later in life, but his failing health prevented him from writing it. The project was taken over, with the van Vogt family’s blessing, by Kevin J. Anderson, and in 2007 the sequel, Slan Hunter, was published. This, of course, is one of the books on my upcoming reading list.

Slan is historically interesting for a number of reasons beyond just being a classic of science fiction. It was written in 1940, as the Third Reich was persecuting Jews throughout Europe, and it is clear that the struggles of the Slan were intended as an analogy for those real-life horrors.

I also noted the striking similarity between Slan and the story of the X-Men, who were created by Stan Lee and Jack Kirby in 1963. Lee apparently never acknowledged the influence of Slan on his own work, but everyone seems to agree that he had likely read the novel and been inspired by it. Obviously, the X-Men became very much their own thing, and I’m not implying any shadiness on the part of Lee and Kirby, but it is always fascinating to me to see how ideas evolve as they are passed from one person to another.

Overall, Slan is a very good novel! It didn’t have a whole lot to do with invisibility overall, but I’m glad my invisibility research led me to read it.