A、To examine the chemical elements in the Ice Age. B、To look into the pattern of solar wind activity. C、To analyze the compositi

You can tell the age of a tree by counting its rings. But these records of tree’s life really say a lot more. Scientists are using tree rings to learn what’s been happening on the sun’s surface for the last ten thousand years. Each ring represents a year of growth. As a tree grows, it adds a layer to its trunk taking up chemical elements from the air. By looking up the dements in the rings from the given year, scientists can tell what dements were in the air that year. Dr. Stevenson is analyzing one element—earbon14 in rings 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 carbon14 trail back in time, he found carbonn4 levels change with the intensity of solar burning. You see the sun has cycles. Sometimes it burns fiercely and other times it is 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 carbon14 co. Earth. When there’s mom solar rand activity, less carbon14 is produced. Ten thousand years of tree fines show that the carbon 14 level rises and falls about every 420 years. The scientists concluded that the solar wind activity must fellow the same cycle.