N-rays

N-rays
	FALSE
	"A new form of radiation, called N-rays, is emitted by many materials and the human body, and can be detected by the way it brightens a faint spark or glowing screen."
Domain	Science & Environment
Tactic	Pseudoscience / Junk Science; Statistical & Evidentiary Distortion;
Era	Historical
First seen	1903
Origin	The French physicist René Blondlot of the University of Nancy, who announced the discovery in 1903
Last reviewed	2026-10-27
	Further reading: books on Science & Environment

N-rays were a form of radiation that the respected French physicist René Blondlot announced in 1903, naming them after his university in Nancy. Within a year, dozens of scientists, most of them in France, had published more than a hundred papers describing the properties of N-rays, which were said to be emitted by many substances, including the human body. N-rays did not exist. In 1904 the American physicist Robert W. Wood visited Blondlot's laboratory and secretly removed a key component from the apparatus; Blondlot and his assistants continued to report seeing the effects. N-rays became the classic example of what the chemist Irving Langmuir later called "pathological science": research in which scientists deceive themselves.

The claim

Blondlot had been studying the newly discovered X-rays when he reported that a small electric spark grew brighter when certain rays were directed at it. He concluded that he had found a new kind of radiation. Experiments in his laboratory and others soon claimed that N-rays were emitted by the Sun, gas burners, heated metal, and the human nervous system and muscles, and that they could be stored in materials, refracted by aluminum prisms and blocked by water. Detection depended on observers judging small changes in the brightness of a faint spark or a phosphorescent screen in a darkened room.

Origin

The discovery came during an exciting period in physics. X-rays had been discovered in 1895, radioactivity in 1896 and the electron in 1897, so a new form of radiation seemed entirely plausible. Blondlot was a member of the French Academy of Sciences, with a strong reputation. National pride may also have played a role, since X-rays had been discovered in Germany and French scientists welcomed a major French discovery. In 1904 the Academy awarded Blondlot a major prize, although officially for his work as a whole.

What the evidence shows

Many physicists outside France, including in Britain and Germany, could not reproduce the effects. In September 1904 Robert W. Wood, a physicist at Johns Hopkins University known for his skill at experimental physics and for debunking, visited Blondlot's laboratory at the suggestion of the journal Nature.

During a demonstration in which N-rays were supposedly being spread into a spectrum by an aluminum prism, Wood, working in the darkened room, quietly removed the prism. Blondlot continued to report the same readings, which should have been impossible. In another test, Wood substituted a piece of wood for a metal file that was supposedly emitting N-rays, and observers still reported the effect. Wood published his account in Nature later that month, without naming Blondlot's assistants.

After Wood's report, interest in N-rays collapsed outside France, and within a few years even French researchers had abandoned them. Blondlot continued to believe in them.

Pathological science

In a 1953 lecture the Nobel Prize–winning chemist Irving Langmuir described "pathological science" as research in which scientists are tricked by subjective effects, wishful thinking or threshold interactions. He listed characteristic symptoms, several of which fit N-rays:

The effect is produced by a barely detectable cause.
The effect is always close to the limit of detection.
Claims of great accuracy are made despite this.
Fantastic theories are proposed to explain the results.
Criticisms are answered with ad hoc excuses.
Support rises to a peak and then fades away.

N-ray detection relied on human judgment of faint changes in brightness, exactly the kind of observation most vulnerable to expectation. Observers who knew what they were supposed to see saw it.

Why it persists

N-rays are still taught as a cautionary tale because they show that self-deception can affect skilled, honest scientists, not just frauds or amateurs. The episode is a central example of why modern science relies on blinding, in which observers do not know which condition they are measuring, and on independent replication.

Lessons for readers

Effects that sit at the edge of detectability deserve extra skepticism.
Expectation can shape what even experts perceive.
Blinded measurements and independent replication protect against self-deception.
A flood of confirming papers from one group or country does not settle a question if others cannot reproduce the result.
Honest scientists can be wrong; the scientific method is designed to catch such errors.

Sources

R. W. Wood, "The N-Rays," Nature 70 (September 29, 1904).
Irving Langmuir, "Pathological Science," colloquium at the Knolls Research Laboratory, December 18, 1953 (transcribed and published in Physics Today, 1989).
Mary Jo Nye, "N-Rays: An Episode in the History and Psychology of Science," Historical Studies in the Physical Sciences 11, no. 1 (1980).
Irving M. Klotz, "The N-Ray Affair," Scientific American 242, no. 5 (1980).