(March 27, 1845 – February 10, 1923)
Although X-ray was part of the electromagnetic radiations which James Clerk Maxwell predicted, and whose existence Heinrich Hertz later confirmed, its characteristics remained unknown until Wilhelm Roentgen disclosed them in 1895. Roentgen was a physicist-cum-engineer, who discovered X-rays while researching on high frequency low wavelength electromagnetic radiations. After the discovery, he did not know what to call it; so, he adopted “x” which is commonly used to denote an unknown mathematical entity. Roentgen studied under August Kundt and Rudolf Clausius: both of whom influenced him greatly. It was from Kundt that he acquired the habit of constructing his own lab apparatuses. Before investigating radiations, his prior works were mostly on the specific heats of gases, the thermal conductivity of crystals, the electrochemical properties of quartz, as well as the magnetoelectric effect. He also researched on how pressure affected the refractive indices of fluids, on the modification of planes of electromagnetically polarized light, as well as on the variations in the functions of the temperature and the compressibility of fluids. His various treatises would help advance several scientific fields. Roentgen was universally praised for not patenting his X-ray discovery: given its medical importance. The Nobel Prize he received in 1901 (for discovering X-ray) made him the first person to be awarded the physics prize. And in 2004, the IUPAC honored him by naming a synthetic element roentgenium. He is also the eponym of the 126-kilometer-wide Roentgen lunar impact crater: adjacent to the ones named after Walther Hermann Nernst and Hendrik Antoon Lorentz.