Rudolf Wolf
DOI: 10.1063/PT.5.031258
Today is the birthday of astronomer Rudolf Wolf, born in Fallenden, Switzerland, in 1816. He studied in Zurich, Vienna, and Berlin before becoming a lecturer in math and physics at the University of Bern. In the 1840s Wolf learned about the work of astronomer Heinrich Schwabe, whose observations of the Sun had led him to propose a cycle in the number of sunspots. In 1847 Wolf started charting sunspots and soon after devised a system for counting sunspots and groups of sunspots. Based on his observations and historical records, he estimated that solar cycles last about 11.1 years. He also correlated solar activity with geomagnetic activity on Earth. Today astronomers still use Wolf’s counting system to study the Sun’s 11-year cycles.
Date in History: 7 July 1816
