From Eric Kvaalen
David Copsey calculates that the sun may emit superflares more or less every 184 years (Letters, 18 June). Some sun-like stars produce superflares; others apparently do not. Those that do are much more magnetically active than the sun. Records of nitric acid and carbon-14 in ice cores show that we have not had a solar flare bigger than the 1859 “Carrington event” since 1561. There are signs of bigger events in the 8th and 10th centuries.
A Carrington-like event may be dangerous to our technological civilisation, but obviously there has not been a superflare capable of wiping out life on Earth for billions of years.
Les Essarts-le-Roi, France
