If you're familiar with modern medicine you've probably had an X-ray or two in your lifetime, so you know what it is. The process has become a standard procedure for a variety of reasons, because it's a non-invasive way of looking at what's inside us – and it's been made relatively simple and cheap.
While it's not 100% safe, a chest X-ray typically exposes a person to a dose of radiation similar to that received during a transatlantic flight. It's fine once in a while but better not to abuse it. Interestingly, about 50 years ago shoe-fitting fluoroscopes were quite common.
Customers of shoe stores would stand so that their feet were inside the machines known as X-ray shoe fitters, Pedoscopes or Foot-o-scopes, which used the X-ray technology to show how well the shoe was fitting. But that's not how the X-rays were first used. What is an X-ray, anyway?
Well, these rays are composed of X-radiation. And the 'X' stands for… 'unknown'. That's right, we colloquially call this form of electromagnetic radiation “unknown rays”. In many languages it's known by another name, Röntgen radiation, after Wilhelm Röntgen. He not only discovered it, but also named it X-radiation to signify the previously unknown type of radiation. Describing to a journalist what happened November 8, 1895 during his experiments with electrical discharge tubes, the scientist said:
"I was working with a Crookes tube covered by a shield of black cardboard. A piece of barium platino-cyanide paper was on the bench there. I had been passing a current through the tube, and I noticed a peculiar black line across the paper…. The effect was one which could only be produced in ordinary parlance by the passage of light. No light could come from the tube because the shield which covered it was impervious to any light known even that of the electric arc….It seemed at first a new kind of invisible light… I tested it. Rays were coming from the tube, which had a luminescent effect upon the paper."
After further experiments focusing on this ability of 'unknown radiation' to pass through objects, Roentgen said, “It soon appeared from tests that the rays had a penetrative power to a degree hitherto unknown.” Eventually, he discovered medical applications of the curiosity when he made a picture of his wife's hand on a photographic plate formed due to X-rays. The photograph of his wife's hand, made in 1895, was the first photograph of a human body part using X-rays. However, a book called The Travels and Adventures of Serendipity by Robert K. Merton argues over the 'accidental' status of this and other discoveries.
Otto Glasser, in his biography of Roentgen, also alleges that a certain version of Roentgen's discovery that is both false and attributes too much importance to accident "has had a wide appeal to the imagination of the general public." … The same is true of the remark made by the historian of science William Cecil Dampier-Whetham, in connection, incidentally, with Roentgen's invention: "Great discoveries are made accidentally less often than the populace likes to think.”
There is another opinion, Sir Alexander Fleming said: “For the birth of something new, there has to be a happening. Newton saw an apple fall; James Watt watched a kettle boil; Roentgen fogged some photographic plates. And these people knew enough to translate ordinary happenings into something new.” And of course, the author of the quote is none other than the person who accidentally discovered penicillin – so, I guess, he's more familiar with chance and serendipity than most of us.
