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Optical physics

Optical physics

A cabinet of invisible curiosities

08 Dec 2014
Taken from the December 2014 issue of Physics World

Invisible: the Dangerous Allure of the Unseen
Philip Ball
2014 The Bodley Head £25.00hb 336pp

Now you see it...

“If you could be invisible, what would you do? The chances are that it would have something to do with power, wealth or sex. Perhaps all three.” This statement from Philip Ball’s book Invisible: the Dangerous Allure of the Unseen may sound cynical, but it is probably also accurate. After all, what would you do if you suddenly had a power that, for nearly all of human history, has belonged to the world of the obscure, the occult and the supernatural?

Ball’s book lures you into this world. In reading it, I was reminded of a Victorian museum: every chapter is full of weird and wonderful exhibits. In the first chapter you enter the courtyard of myths and sagas. There, the technology of invisibility is of no concern – gods, after all, can do anything – but the exhibition shows you the human reasons why someone might wish to become invisible. Yes, they are what you would expect: power, wealth and sex, or all three together.

Next comes the dungeon of the dark ages, filled with occult forces that can be mastered with complicated spells and magical ingredients (black cats, mirrors, poisonous plants and the like) if you have acquired the right secret knowledge, the Faustian tome, “with secrets crammed, from Nostradamus’ very hand”. The guardians of this world were the secret societies such as the Rosicrucians and Freemasons who lured their followers away from the path of the plain and obvious. One may be amused or confused by the actions of this dungeon’s inhabitants, but their crude attempts at natural magic were probably the beginning of the dream of mastering the unseen. However inadequate their means were at the time, in some sense they were the precursors of the scientific societies of today.

Once past the dungeon, one enters the chamber of ghosts and fairies – spiritualism was very much en vogue in Victorian times – followed by a large hall filled with the apparatus of invisible rays and waves. Here we find such curiosities as Röntgen’s X-rays, revealing skeletons in living people, and Marconi’s radio waves, carrying voices over vast distances. Sometimes, technology and the desire for the supernatural mixes, for in spiritualistic séances, Victorian ghosts communicate in a code inspired by the Morse code of the telegraph.

The next room is more brightly lit, illustrating the concept of unseen forces and particles forming the foundations of the world as we see it. On one wall, the portrait of Sigmund Freud guides you through a séparé to an antechamber dedicated to psychology and the subconscious, where seeing is not always believing. This is followed by the hall of fame of invisible novel and film characters, in particular H G Wells’ “Invisible Man” and his cousins. Here, too, is some nice physics, explaining how the invisible man disappears. The science of light – optics – has finally found a place in the museum.

The next hall is filled with magnifying glasses and microscopes, revealing the world of the microscopically small – the bizarre, monstrous forms of fleas and other insects that shocked people when they first saw them, but also the invisible world of bacteria and viruses. In making this world visible, scientists discovered the real causes of infectious diseases and could finally come up with effective remedies against them, from disinfectants to antibiotics, much to the benefit of mankind. But fears of the microworld still linger: what if a grey goo of rampant nanobots infects us all?

The last two chapters deal with camouflage, stealth and other forms of modern invisibility technology. Here, Ball points out how much attitudes have changed over time. A microwave cloaking device, for example, would not have impressed a medieval audience at all, as it is clearly visible. All it does is guide invisible electromagnetic microwaves around objects placed inside the device; it is only invisible to the already invisible. Only if you know from science that these invisible waves are as real as the world you see with your own eyes will you find this impressive. The fact that people have indeed been impressed by microwave cloaking shows the extent to which science has entered the public consciousness.

Invisible is filled to the brim with stories, anecdotes and gossip about people whose names you have probably never heard. It may amuse you to learn what both serious people and charlatans have believed in the past and how incredibly they went wrong. But equally, it may depress you, as you may wonder whether we are any wiser these days: “For while man strives he errs”, as Goethe’s Faust has it. For my taste, however, the book focuses too much on the dark, gothic side of invisibility and on the absurd errors of our unfortunate predecessors. Even in the darkest times, amidst the greatest confusion and error, there has been an invisible stream of reason, clarity and wonder that elevates those who follow it above the absurd. It is called science. As Steven Weinberg put it in The First Three Minutes, “The effort to understand the universe is one of the very few things which lifts human life a little above the level of farce and gives it some of the grace of tragedy.” In a book about invisibility, I would have preferred less of the farce and more of the science.

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