Debbie Ebenstein, age 12, of Peoria, Illinois, for her question:

How many dog years are equal to one human year?

A light year equals about six million million earth miles. But a dog's year is something else. It is based very roughly on life spans    the life expectancy of an average human being and the life expectancy of an average dog. Barring accidents, a healthy human may live to celebrate his or her 80th birthday    or maybe longer. Barring accidents, a healthy dog is an old fellow at the age of 12 years and his family cannot expect to enjoy his company much longer than 13 years.

Growing up and growing old are somewhat different in dogs and people. A dog matures faster. A puppy develops through the first six months of his life while a human child is progressing through six years. At eight months to two years the dog is fully grown. At the age of two, each year compares with about 12 human years:, Then the dog slows down. After he reaches adulthood, every year of a dog's life equals about four years in the life of a human being. On the life time average, each dog year can be compared with six or seven human years. A 12 year old dog is as biologically old as an elderly gentleman of about 75.