The year 1906 in science and technology involved some significant events, listed below.
Chemistry
Charles Barkla discovers that each element has a characteristic X-ray and that the degree of penetration of these X-rays is related to the atomic weight of the element. Mikhail Tsvet first names the chromatography technique for organic compound separation, in the course of demonstrating that chlorophyll is not a single chemical compound.
Geology
April 18 – The San Francisco earthquake, an estimated 7.9 on the Richter scale and centered on the San Andreas fault, strikes near San Francisco, California. The earthquake and fire destroy over 80% of the buildings in the city, and kill as many as 6,000 people. Harry Fielding Reid devises the elastic-rebound theory to account for earthquake mechanism. Richard Oldham argues that the Earth has a molten interior.
Mathematics
Andrey Markov produces his first theories on Markov chain processes. Axel Thue uses the Thue–Morse sequence to found the study of combinatorics on words.
Medicine
September – Last death from yellow fever in the Panama Canal Zone following a mosquito eradication program led by William C. Gorgas. October–December – Martha Baer undergoes sex reassignment surgery to become Karl M. Baer in Germany. November 3 – A speech given by Alois Alzheimer for the first time presents the pathology and clinical symptoms of pre-senile dementia together; the condition will rapidly become known as Alzheimer's disease. BCG (Bacilli-Calmette-Guerin) immunization for tuberculosis first developed. Transmission of dengue fever by the Aedes mosquito is confirmed. Frederick Hopkins proposes the existence of vitamins and suggests that a lack of them causes scurvy and rickets. Charles Sherrington publishes The Integrative Action of the Nervous System. Clemens Peter von Pirquet, with Béla Schick, coins the term "allergy" to describe hypersensitive reactions. Royal Victoria Hospital, Belfast, is completed, the first such air conditioned building in the world. George Newman publishes Infant Mortality: a Social Problem in England. August von Wassermann develops a complement fixation test for the diagnosis of syphilis.
Physics
Walther Nernst presents a formulation of the third law of thermodynamics.
Technology
January – Lee De Forest files a patent for the Audion vacuum tube, which helps usher in the age of electronics. February 10 – Launch of British battleship HMS Dreadnought. March 18 – At Montesson in France, Romanian inventor Traian Vuia becomes the first person to achieve an unassisted takeoff in a heavier-than-air powered monoplane, but it is incapable of sustained flight. October 18 – German inventor Arthur Korn demonstrates the transmission of a photograph electronically over a distance of 1800 km using his Bildetelegraph or phototelautograph system. December 24 – Reginald Fessenden makes the first radio broadcast, including a musical recording, a violin solo, and readings, from Brant Rock, Massachusetts. The first practicable gyrocompass is invented by Hermann Anschütz-Kaempfe in Germany.
Events
November 12 – First displays of the Deutsches Museum open to the public in Munich.
Publications
African Invertebrates begins publication as Annals of the Natal Government Museum; it will be continuing publication more than a century later.