Weather in Space

Sunspots and Solar Activity

Who managed to calculate cosmic ray activity on Earth dating back over 11,000 years?

Sami Solanki (1958-), an astronomy professor at Germany’s Max Planck Institute, developed a method for estimating solar ray activity dating back millennia. Solanki based his method on the knowledge that cosmic rays create chemical reactions in the atmosphere. One byproduct of these reactions is carbon-14, which then precipitates down onto the Earth’s crust. Trees and other vegetation absorb this radioactive form of carbon; preserved vegetation that has been buried underground for centuries can be dug up and its composition analyzed. Radiation from sunspots actually decreases the production of carbon-14, and so when sunspot activity is high, there is less carbon-14 for trees to absorb. Using this information, Solanki discovered that there has been more sunspot activity since around 1930 than during any other period going back 8,000 years.


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