Rudolf Wolf

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Rudolf Wolf
Rudolf Wolf
Born7 July 1816
Died6 December 1893 (1893-12-07) (aged 77)
Alma materUniversity of Zurich
Known forWolf number
Scientific career
InstitutionsUniversity of Zurich
Doctoral advisorEncke

Johann Rudolf Wolf (7 July 1816 – 6 December 1893) was a Swiss astronomer and mathematician best known for his research on sunspots.

Wolf was born in Fällanden, near Zurich. He studied at the universities of Zurich, Vienna, and Berlin. Encke was one of his teachers. Wolf became professor of astronomy at the University of Bern in 1844 and director of the Bern Observatory in 1847. In 1855 he accepted a chair of astronomy at both the University of Zurich and the Federal Institute of Technology in Zurich.

Wolf was greatly impressed by the discovery of the sunspot cycle by Heinrich Schwabe and he not only carried out his own observations, but he collected all the available data on sunspot activity back as far as 1610 and calculated a period for the cycle of 11.1 years.[1] In 1848 he devised a way of quantifying sunspot activity. The Wolf number, as it is now called, remains in use. In 1852 Wolf was one of four people who discovered the link between the cycle and geomagnetic activity on Earth.[2][3]

Around 1850, to study the laws of probability, Wolf performed a Buffon's needle experiment, dropping a needle on a plate 5000 times to verify the value of π, a precursor to the Monte Carlo method.[4][5][6]


  1. ^ Wolf, R. (1852). "Neue Untersuchungen über die Periode der Sonnenflecken und ihre Bedeutung" [New investigations regarding the period of sunspots and its significance]. Mittheilungen der Naturforschenden Gesellschaft in Bern (in German). 255: 249–270. Wolf's estimates of the solar cycle's period appear on p. 250 and p. 251.
  2. ^ Wolf, R. (1852). "Sonnenflecken-Beobachtungen in der ersten Hälfte des Jahres 1852; Entdeckung des Zusammenhanges zwischen den Declinationsvariationen der Magnetnadel und den Sonnenflecken" [Sunspot observations in the first half of the year 1852; discovery of a relation between the variations of the declination of the magnetic needle and sunspots]. Mittheilungen der Naturforschenden Gesellschaft in Bern (in German). 245: 179–184.
    Notices of Wolf's discovery appeared in:
  3. ^ The three other astronomers who observed a relation between the solar cycle and magnetic declination on Earth were:
  4. ^ "Wolf biography". Retrieved 2017-10-20.
  5. ^ Riedwyl, Hans (1990). "Rudolf Wolf's Contribution to the Buffon Needle Problem (an Early Monte Carlo Experiment) and Application of Least Squares". The American Statistician. 44 (2): 138–139. doi:10.2307/2684154. JSTOR 2684154.
  6. ^ J.V. Uspensky (1937). Introduction To Mathematical Probability. pp. 112–113.

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