N ray

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The so-called N rays (or N-rays) were a phenomenon described by French scientist René-Prosper Blondlot but subsequently found to be illusory.

In 1903, Blondlot, a distinguished physicist working at the University of Nancy, perceived changes in the brightness of an electric spark in a spark gap which he actually photographed and he attributed to a novel form of radiation, naming it the N-ray, for the University of Nancy. However, no other researchers seemed able to reproduce his photographs. Blondlot, Augustin Charpentier, Arsène d'Arsonval and many others claimed to be able to detect rays emanating from most substances, including the human body. Most researchers of the subject at the time used the perceived light of a dim phosphorescent surface as "detectors", although work in the period clearly showed the change in brightness to be a physiological phenomenon rather than some actual change in the level of illumination. Physicists Gustave le Bon and P. Audollet and spiritualist Carl Hunter even claimed the discovery as their own, leading to a commission of the Académie des sciences to decide priority.

The "discovery" excited international interest and many physicists worked to replicate the effects. However, the notable physicists Lord Kelvin, William Crookes, Otto Lummer and Heinrich Rubens failed to do so. Following his own failure, self-described as "having wasted an entire morning", US physicist Robert W. Wood who had a reputation as a popular "debunker" in the period was prevailed upon to travel to Blondlot's lab in France to investigate further. He secretly removed an essential prism from the experimental apparatus, yet the experimenters still said that they observed N rays. He secretly replaced a large file that was supposed to be giving off N rays with an inert piece of wood, yet the N rays were still "observed". His report on these investigations, published in the September 29, 1904 edition of Nature, suggested that these were a purely subjective phenomenon, with the scientists involved having recorded data that matched their expectations. By 1905 no one outside Nancy believed in N rays.

The incident is used as a cautionary tale among scientists on the dangers of error introduced by experimenter bias. More precisely, patriotism was at the heart of this self-deception. France had been defeated by the Germans in the Franco-Prussian War in 1870, and after the major discovery by Wilhelm Röntgen of the X Ray the race was on for new discoveries.

N rays were cited as an example of pathological science by Irving Langmuir. However, the case is far more interesting than a single event, because nearly identical properties of an equally unknown radiation were recorded some 50 years before in another country by the Baron von Reichenbach in his treatise "Researches on Magnetism, Electricity, Heat, Light, Crystallization, and Chemical Attraction in their relations to the Vital Force", London, 1850, and before that in Vienna by F.A. Mesmer in his "Memoire on the discovery of Animal-magnetism", 1779. It is clear that Reichenbach was aware of Mesmer's work and that researchers in Paris working with Blondlot were aware of Reichenbach's work (Revue Scientifique, Ser 5, Vol II, No.22) although there is no proof that Professor Blondlot was personally aware of it. However, this spread of nearly identical pathological science in history shows the phenomena to have greater breadth than the usually assumed patriotic self-deception.

Blondlot still has a street named after him in downtown Nancy as the belief that he had made a major discovery persisted.

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