I keep finding new invisibility stories! Will I ever come to an end? Stay tuned!

It is pretty clear at this point that stories about invisibility were a huge business in the early to mid 20th century, and every author of science fiction or horror had to get in on the action in some way or another.

For example, I just had to type “Edmond Hamilton” and “invisibility” into a search bar and found Edmond Hamilton’s “The Invisible Master,” that appeared in Scientific Detective Monthly in the April, 1930 issue.

Edmond Hamilton (1904-1977) is another one of those super-prolific science fiction authors who had a huge influence on the field but isn’t broadly recognized like an Asimov, Bradbury or Clarke. I would be hard-pressed to single out a particular story of his that everyone would know, but I’m particularly fond of “The Metal Giants,” that appeared in Weird Tales in December 1926. I like big stompy robots!

“The Invisible Master” is more of a mystery story than science fiction, marking invisibility’s foray into another genre of fiction. It also happens to have one of the best and most enjoyable descriptions of invisibility that I’ve yet seen! Let’s take a look at the story, and I’m going to be a bit spoilery this time!

If you want to read the story beforehand, here’s a link to the pdf posted through my blog.

The story begins with reporter Charlie Carton being assigned to go see a demonstration of Dr. Howard Grantham’s new scientific invention which, of course, is invisibility. In front of a small crowd of journalists, Grantham uses his device, which so far is a small cabinet, to make an opaque black glass paperweight gradually vanish before their eyes with the turn of a knob!

What really gets me is the explanation he gives for how his invisibility works:

“Why is it, then? Why do we see a house? We see it for two reasons, its obstruction and reflection of light. The light rays come to us from all around it, but not from behind the house because they are stopped by it. The house, then, is an area of comparative darkness to us, and so is outlined against the light. Also light is reflected from all sides upon it and to our eyes.”

“But suppose that the light-rays behind, instead of being stopped by the house, curved round it? Then we would see what was behind the house, with ease, and the house itself would be quite invisible to us, granted that light striking it from all sides did not really strike it but curved around it. Then if I want to make a house, or a tree, or a stone, invisible, all I need to do is to deflect the light- rays around it in such a way that they will curve around and avoid it instead of ever striking it.”

This is quite amazing, because this is more or less exactly how we describe the operation of modern theoretical invisibility cloaks!

In 2006, the actual “cloaking craze” in physics began with the publication of two theoretical papers in the journal Science back to back. One paper was by Ulf Leonhardt, then at the University of St. Andrews, and the other by John Pendry from Imperial College and David Schurig and David Smith, then at the University of California, San Diego. Both papers used the same strategy for invisibility: guiding light rays (technically, light waves) around a central cloaked region and then sending them on their way. Illustrations of their designs are shown below.

But how are these light-guiding structures made? Physicists took a page from the mathematics of Einstein’s general relativity. Einstein conceived of gravity as mass physically warping the structure of space and time, and one of the side effects of this is that light can be bent around massive objects like black holes, in a phenomenon known as gravitational lensing. A black hole warps space towards its center; cloaking researchers imagined a cloaking device warping space away from its center. Once the mathematical warping is selected, it is possible to find a material structure that will mimic that spatial warping.

So let’s return to Dr. Grantham’s explanation of invisibility in “The Invisible Master”:

“Can that be done? In principle, it has been possible for years, for years ago we learned that light does not always travel in straight lines but can be deflected to one side or another by certain forces. Einstein’s discoveries showed that, it being photographically confirmed after his theory that the light-rays of stars curve in toward the sun in passing it in space. If there is a force that will attract light-rays and make them curve in toward an object, why not a force that will repel the light- rays and make them curve outward to avoid an object?”

The “photographic confirmation” described in the story is the photographs taken by astronomers Dyson and Eddington during the May 29, 1919 solar eclipse. Einstein’s theory predicted that starlight would be bent in a certain way when passing close to the sun. It would only be possible to observe this effect during a total solar eclipse, so Dyson and Eddington organized two expeditions, one to the African island of Principe and the other to Brazil. The photographs seemed to confirm Einstein’s predictions, and the results were heralded around the world.

So, in short: Edmond Hamilton pretty accurately nailed the theoretical principles of invisibility, better than any other science fiction author before him!

But what about the rest of the story? After Grantham’s demonstration, the journalists report on the amazing scientific achievement. The next day, however, Grantham is found knocked unconscious, and a portable version of his invisibility device has been stolen! Grantham’s assistant Gray has also gone missing. Soon, the police receive a letter from someone calling themselves “The Invisible Master,” who declares themselves the new master of the city.

They are quick to exercise their power. A bank teller finds money swiped right in front of his face by an invisible thief, and soon a number of people are murdered and robbed around the city by someone who the surviving witnesses claim was completely invisible!

At last, having shown his power, the Invisible Master makes one final demand: five million dollars to leave the city alone for good! Using an inflation calculator, that would be $83 million dollars today! The police set a trap, but the Master slips through their fingers again, getting away with the money for good.

Spoilers to follow

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But did they get away? Sergeant Wade ponders the case further, and finally comes up with the answer to the whole puzzle: there never was any invisibility device, nor any “Invisible Master.” The whole thing was a hoax contrived by Dr. Grantham. But why would Grantham concoct a plan to steal millions of dollars? After he has successfully shifted the blame to his assistant Gray (whom he murdered), Grantham gives a motive by proxy:

“Why should Gray be so crazy after money, anyway?” Wade asked him. “They tell me he was a scientific rather than business type.”

“I think I can understand it,” President Ellsworth said. “Gray has long wanted funds for independent research—even he and Grantham here have been terribly hampered in their work by lack of money. He has seen the millions that are spent each year in this city on luxury and pleasure, has reflected how much good might result to the human race were part of it applied to scientific research, and has started out with this weapon of invisibility to get it!”

Yep, it’s the same old story: scientist struggling to find grant money takes on a life of crime to pay the scientific bills!

But if invisibility doesn’t exist, how did Grantham manage to pull off this scheme? First, there’s some genuine optics:

“A tourmaline crystal,” he said. “There’s another set in that small window pane. Their property is well enough known to physicists, and is a result and proof of the polarization of light. When two tourmaline crystals are placed together with their axes parallel, light streams through both unchecked. If one is turned so that its axis is at right angles to the axis of the other, though, light cannot pass through them and they become thus opaque. A quarter-turn of the one will make them transparent again.

This made me so happy when I read it! Hamilton is basically talking about the classic crossed polarizers experiment! Light is a transverse wave, which means the “wiggles” of light are perpendicular to the direction that light travels.

This means that a beam of light, in general, can consist of two distinct kinds of wiggles: let’s call them “up-and-down” and “left-and-right.” A polarizer will block one type of light: a vertical polarizer will block “up-and-down” and a horizontal polarizer will block “left-and-right.” two perpendicular polarizers will then block all the light passing through! If one polarizer is rotated relative to the other, one will go from seeing lots of light passing through them to no light being passed; here’s an old video I did of this:

So Grantham performed his invisibility illusion by sneakily replacing the black glass paperweight with a pair of crossed polarizers, one of which he could subtly rotate to make the glass seem to disappear! Tourmaline crystal is birefringent, meaning that it is polarization sensitive. Not sure if it could be used exactly like Hamilton describes, but it is an imaginative idea!

But how did he pull off the crimes around the city? He didn’t! He relied on the psychology of people:

“Now what would naturally result when almost all in the city believed that? Would it not result in many people seeing a chance to commit crimes and then blame them on the Invisible Master?”

In other words: Grantham banked on the fact that, in a city of several hundred thousand people, some people would take the opportunity of the Invisible Master to commit crimes! Those people killed by the “Master” were killed by the surviving “victims” of the Master. And stealing the money in the end was basically classic misdirection: all the police were looking for the invisible criminal and didn’t notice Grantham hiding away the extortion money himself!

So “The Invisible Master” is not even a story about real invisibility at all, but ironically contains some of the best descriptions of invisibility — and optics — that I’ve seen in a science fiction story!