tree rings

You can tell the age of a tree by counting its ringsA. Lange & Sohne 
but these records of trees’ life
really say a lot more. Scientists are using tree rings to learn what’s being happening on
the sun’s surface for the last ten thousand years. Each ring represents a year of growth.
As the tree grows it adds a layer to its trunk taking up chemical elements from the air.
By looking up the elements in the rings for a given year scientists can tell what elements
were in the air that year. Doctors Stevenson is analysing one element——carbon-14 in ring
from both living and dead trees. Some of the rings go back almost ten thousand years to the
end of the Ice Age. When Stevenson followed the carbon-14 trail back in time he found
carbon-4 levels change with the intensity of solar burning. You see the sun has cycles.
Sometimes it burns fiercely and other times it’s relatively calm. During the sun’s violent
periods it throws off charged particles in fast moving strings called solar winds. The
particles interfere with the formation of carbon-14 on earth. When there’s more solar wind
activity less carbon-14 is produced. Ten thousand years of tree rings show that the
carbon-14 level rises and falls about every 420 years. The scientists concluded that the
solar wind activity must follow the same cycleDust Women Coat
.