Denrochronology (from the Greek δένδρον = tree, χρόνος = time, and λογία = study) or tree-ring dating is the method of scientific dating based on the analysis of tree-ring growth patterns. This technique was developed during the first half of the 20th century originally by the astronomer A. E. Douglass, the founder of the Laboratory of Tree-Ring Research at the University of Arizona. Douglass sought to better understand cycles of sunspot activity and reasoned (correctly) that changes in solar activity would affect climate patterns on earth which would subsequently be recorded by tree-ring growth patterns (i.e., sunspots → climate → tree rings). The technique of dendrochronology can date the tree rings in many types of wood to the exact calendar year each ring was formed.