The Sunspot Number, the longest scientific experiment still ongoing, is a crucial tool used to study the solar dynamo, space weather and climate change. It has now been recalibrated and shows a ...

along the ice core, reflecting past-atmospheric dust concentrations." Plain old dust, Ram added, holds the key in these experiments because it reflects how dry conditions were in a particular year.

Sunspots come and go, but recently they have mostly gone. For centuries, astronomers have recorded when these dark blemishes on the solar surface emerge, only to fade away after a few days, weeks or ...