|Born||7 July 1816|
|Died||6 December 1893 (aged 77)|
|Alma mater||University of Zurich|
|Institutions||University of Zurich|
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. 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.
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.
- 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 [Reports of the Scientific Society of Bern] (in German). 255: 249–270. Wolf's estimates of the solar cycle's period appear on p. 250 and p. 251.
- 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:
- Wolf, R. (1853). "Ueber den Zusammenhang magnetischer Erscheinungen mit dem Zustande der Sonne" [On the relation of magnetic phenomena with the condition of the sun]. Astronomische Nachrichten [Astronomical News] (in German). 35 (820): columns 59–60.
- Wolf (1852). "Liaison entre les taches du Soleil et les variations en déclinaison de l'aiguille aimantée" [Connection between sunspots and variations in the declination of a magnetic needle]. Comptes rendus (in French). 35: 364.
- Wolf, Rod. (1852). "Sur le retour périodique de minimums des taches solaires; concordance entre ces périodes et les variations de déclinaison magnétique" [On the periodic return of sunspot minima; agreement between these periods and the variations of magnetic declination]. Comptes rendus (in French). 35: 704–705.
- The three other astronomers who observed a relation between the solar cycle and magnetic declination on Earth were:
- Johann von Lamont (1805–1879) of Scotland and Germany: Lamont (1851). "Ueber die zehnjährige Periode, welche sich in der Gröβe der täglichen Bewegung der Magnetnadel darstellt" [On the ten-year period which is present in the magnitude of the daily movement of the magnetic needle]. Annalen der Physik. 2nd series (in German). 84: 572–584. doi:10.1002/andp.18511601206.
- Edward Sabine (1788–1883) of Ireland: Sabine, Edward (1852). "On the periodical laws discoverable in the mean effects of the larger magnetic disturbances". Philosophical Transactions of the Royal Society of London. 142: 103–124. From p. 103: " … I have had the satisfaction of finding that the observations [of magnetic declination] of these years [i.e., 1846–1848] confirm … the existence of a periodical variation, which … corresponds precisely both in period and epoch, with the variation in the frequency and magnitude of the solar spots, recently announced by M. Schwabe … "
- Jean-Alfred Gautier (1793–1881) of Switzerland: Gautier, Alfred (1852). "Notice sur quelques recherches récentes, astronomiques et physiques, relative aux apparences que présente le corps du soleil" [Notice on some recent astronomical and physical investigations regarding appearances that the body of the sun shows]. Bibliothèque Universelle de Genève: Archives des sciences physiques et naturelles (in French). 20: 177–207, 265–282. On pp. 189–190, after discussing Schwabe's discovery of the solar cycle, Gautier presents Lamont's findings on the relation between the solar cycle and the periodic variations in the magnetic declination. Gautier mentions that the Austrian astronomer Augustin Reslhuber (1808–1875) confirmed Lamont's findings. (Reslhuber's confirmation appeared in: Reslhuber, A. (1852). "Ueber die vom Dr. Lamont beobachtete zehn-jährige Periode in der Größe der täglichen Bewegung der Declinationsnadel" [On the ten-year period in the magnitude of the daily movement of the declination needle, which was observed by Dr. Lamont]. Annalen der Physik. 2nd series (in German). 85: 412–420.)
- "Wolf biography". www-history.mcs.st-andrews.ac.uk. Retrieved 2017-10-20.
- 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.
- J.V. Uspensky (1937). Introduction To Mathematical Probability. pp. 112–113.
- Lutstorf, Heinz Theo. Professor Rudolf Wolf und seine Zeit 1816-1893 (PDF). ETH-Bibliothek.
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- The Sun – History
- Analysis of Wolf's dice data by Edwin Jaynes
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