Science and Coding Not every tree has a nickname, but The President has earned it. This tree is a giant sequoia that stands 247 feet tall. That is as tall as a ten-story building. It is estimated to be over 3,200 years old. That would mean it started growing around the same time as when Greece attacked Troy in the Trojan War of legend. A dendrochronologist is a scientist who measures the age of trees. The data they collect can be used to study atmospheric conditions in a specific year and the rates of climate changes. How do scientists determine the age of a tree? For a living tree, scientists measure the height, girth (circumference), and the size of the leaf canopy of the tree. Sometimes they drill a hole through the tree to extract a core sample. This sample is then used to count the tree rings. To assess the age of a dead tree, the trunk can be sliced to make a “tree cookie.” On this cross section, the number of rings can be counted. New growth occurs near the bark. A tree adds one ring each year it is alive. A single ring is composed of a light layer and a dark layer. The light layer is growth from the spring, which is faster. This is known as spring wood or early wood. The dark layer is growth from the summer, which is slower. This is known as summer wood or late wood. It is denser than spring wood. The algorithm for determining the age of a tree is to count the number of rings. Look at the photograph. Notice that the growth rings are not the same size. How can you determine which years had the most rainfall? How can you evaluate your algorithm for success? Assume the tree was cut down in 2017. The tree stopped growing at that point, so no more rings were created. Using your algorithm, in what year had the least rainfall? Do not count the bark as an annual ring. Algorithm for Tree Age Jody/Shutterstock.com The President is a giant sequoia estimated to be over 3,200 years old. Alan Linn/Shutterstock.com The cross section of a tree trunk can reveal the age of the tree. Copyright Goodheart-Willcox Co., Inc. 34 34 I t d d ti t C t S S i C Introd duction to Computer S Science: Codingdi