1906 in science

The year 1906 in science and technology involved some significant events, listed below.

• 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.^[1][2]

• 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.^[3]
• Richard Oldham argues that the Earth has a molten interior.^[4]

• 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.

• September – Last death from yellow fever in the Panama Canal Zone following a mosquito eradication program led by William C. Gorgas.^[5]
• 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;^[6][7] the condition will rapidly become known as Alzheimer's disease.^[8]
• BCG (Bacilli-Calmette-Guerin) immunization for tuberculosis first developed.
• Transmission of dengue fever by the Aedes mosquito is confirmed.^[9]
• 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.

• Walther Nernst presents a formulation of the third law of thermodynamics.

• January – Lee De Forest files a patent for the Audion vacuum tube, which helps usher in the age of electronics.^[10]
• 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^[11] 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.^[12][13]

• November 12 – First displays of the Deutsches Museum open to the public in Munich.

• African Invertebrates begins publication as Annals of the Natal Government Museum; it will be continuing publication more than a century later.

• Nobel Prizes
  • Physics – Sir J. J. Thomson
  • Chemistry – Henri Moissan
  • Medicine – Camillo Golgi, Santiago Ramón y Cajal
• Hughes Medal – Hertha Ayrton

• January 6 – G. Ledyard Stebbins (died 2000), American botanist and geneticist.
• January 10 – Grigore Moisil (died 1973), Romanian mathematician.
• January 11 – Albert Hofmann (died 2008), Swiss chemist.
• February 3
  • George Adamson (died 1989), Indian-born wildlife conservationist.
  • Ilona Banga, Hungarian biochemist (died 1998)
• February 4 – Clyde Tombaugh (died 1997), American astronomer.
• February 17 – Elizabeth M. Ramsey (died 1993), American research physician.
• February 18 – Hans Asperger (died 1980), Austrian pediatrician.
• April 28 – Kurt Gödel (died 1978), Austrian mathematician.
• June 13 – Bruno de Finetti (died 1985), Italian statistician.
• June 15 – Gordon Welchman (died 1985), English-born mathematician and cryptanalyst.
• June 18 – Orvan Hess (died 2002), American obstetrician.
• June 23 – Derek Jackson (died 1982), Swiss-born British spectroscopist and steeplechase rider (also his twin brother Vivian).
• June 28 – Maria Göppert (died 1972), German-born theoretical physicist, recipient of the Nobel Prize in Physics.
• July 2 – Hans Bethe (died 2005), German-born physicist, recipient of the Nobel Prize in Physics.
• August 19 – Philo Farnsworth (died 1971), American television pioneer.
• September 1 – Karl August Folkers (died 1997), American biochemist.
• September 4 – Max Delbrück (died 1981), German-born biologist.
• September 30 – Vera Faddeeva (died 1983), Soviet mathematician.
• October 2 – Willy Ley (died 1969), German-born scientific populariser.
• November 3 – Carl Benjamin Boyer (died 1976), American historian of mathematics.
• November 5 – Fred Lawrence Whipple (died 2004), American astronomer, coins the term "dirty snowball" to explain the nature of comets.
• November 18 – George Wald (died 1997), American scientist.
• December 9 – Grace Hopper (died 1992), American computer scientist.
• December 25 – Ernst Ruska (died 1988), German physicist, recipient of the Nobel Prize in Physics.

• January 13 (Old Style December 31, 1905) – Alexander Stepanovich Popov (born 1859), Russian physicist.
• January 14 – Hermann Sprengel (born 1834), German-born British chemist.
• February 27 – Samuel Pierpont Langley (born 1834), American astronomer.
• March 8 – Henry Baker Tristram (born 1822), English ornithologist.
• April 19 – Pierre Curie (born 1859), French winner of the Nobel Prize in Physics.
• May 15 – James Blyth (born 1839), Scottish electrical engineer.
• July 5 – Paul Drude (born 1863), German physicist (suicide).
• September 5 – Ludwig Boltzmann (born 1844), Austrian physicist.