Gary Moore, age 13, of East Peoria, Illinois, for his question:

Is a knot loner than a mile?

A mile is a measure of distance. The land mile is equal to 1760 yards or 5280 feet. The sea mile is a section of a great circle around the earth. It is equal to 6080.20 feet. This is the nautical mile used by ships at sea. The knot is a measure of speed. It is the number of sea miles which a ship travels in one hour.

The knot was originally a mark on a cord. The cord was attached to the ships log, a gadget which trailed through the water behind the ship. This device measured the speed of the ship as so many marks or knots were paid out on the line. The number of knots that went by in 28 seconds gave the number of miles per hour at which the ship was traveling.

Nowadays, this job is done by a more complex device called a taffrail. Suppose you say that a ship is traveling at 20 knots an hour. A real sailor would know in a minute that you are a landlubber. For a knot means so many sea miles per hour. To be correct, you must say that the ship is traveling at 20 knots.