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1904 Butterfly diagram: sunspots

Author: Edward Walter Maunder (1851-1928)

Use of the "butterfly diagram'' to study the variation of sunspots over time, leading to the discovery that they were markedly reduced in frequency from 1645--1715 (the "Maunder minimum''). [Earlier work, started in 1843 by H. Schwabe, showed that sunspots exhibit an approximately twenty-two year cycle, with each eleven-year cycle of sunspots followed by a reversal of the direction of the sun's magnetic field]

Category: Statistics & Graphics

This web version is dedicated to Arthur H. Robinson (1915-2004), who inspired and encouraged our interest; to Antoine de Falguerolles, who initiated it, and to les Chevaliers des Album de Statistique Graphique, who supported it with interest, enthusiasm, and resources. In particular, Gilles Palsky, Antoine de Falguerolles, Antony Unwin and Ruddy Ostermann contributed important images and background information. This work is supported by the National Sciences and Engineering Research Council of Canada, Grant OGP0138748.

Citations: References to information or images obtained from this web site should be cited as follows:
Friendly, M. & Denis, D. J. (2001). Milestones in the history of thematic cartography, statistical graphics, and data visualization. Web document, http://www.datavis.ca/milestones/. Accessed:

Copyright © 2001-2018 Michael Friendly
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