Mysteries of vernacular: X-ray - Jessica Oreck and Rachael Teel

Mysteries of vernacular: X-ray, a form of electromagnetic radiation capable of penetrating solids. The word X-ray harkens back to the work of Rene Descartes, a French philosopher, mathematician, and writer in the 17th century.

One of Descartes' innumerable contributions to the world of numbers was the invention of a simple yet brilliant convention most people take for granted today: the representation of unknowns within an equation as X, Y, and Z. When the German scientist Wilhelm Rontgen discovered what we now call X-rays in the late 19th century, he gave them the name X-strahlen.

Strahlen is German for shine, and X, of course, represented the unknown nature of the radiation Rontgen had discovered, the X-factor, so to speak. The English translation maintained the X but replaced the German shine with ray, meaning a beam of light.

Coincidentally, in mathematics, the word ray refers to a line with a point of origin that has no end and extends to infinity, bringing us neatly back to the unknown. Today we understand what X-radiation is, and in spite of the humble objections of its discoverer, it is also commonly called Rontgen Radiation, eliminating with the X the fundamental mystery of its nature.