Sharon Kelly, age 11, of Nogales, Ariz., for her question:

HOW LONG IS A MILE?

In the system of measurement used in the United States today, the unit of measurement used for distance on land is called the statute mile or land mile. It is equal to 5,280 feet.

The mile was first used by the ancient Romans. It was about 5,000 feet long and contained 1,000 paces, each five feet in length.

The term "mile" comes from "milia pasuum," the Latin word for "a thousand paces."

Around the year 1500, the 5,000 foot Roman mile was changed to the 5,280 foot mile of today, although many countries still kept their own length.

The metric system measures land distances in kilometers. A kilometer equals 3,280.8 feet, or about five eighths of a mile. One mile equals 1.60934 kilometers.

Distances on the sea are measured in nautical miles. The international nautical mile used in the U.S. equals 6,076 feet. This makes the international nautical mile equal to 1.1540779 statute or land miles.