13:26 16 September 2013
Transient dark features on the sun's surface – sunspots – were first noted by astronomers in ancient Greece and China some 2500 years ago. We have been recording sunspot numbers since the early 17th century, so creating the world's longest continuous data series. As indicators of solar activity, these records are essential in fields from space mission planning to climate science – making recent controversy about their long-term accuracy of more than academic interest. Richard Webb
Read more: "Spot of bother: have we been getting solar activity wrong?"
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The suggestion that they were features of the sun's surface, rather than orbiting bodies transiting across its face, put Galileo in conflict with other astronomers of the day such as Christoph Scheiner, who argued that the sun was a perfect, unblemished creation of God.
(Image: SSPL/Getty)
