Nautical Miles and Knots

A nautical
mile is precise measurement based on the circumference of the earth. The
equator divides the earth into two equal halves. This circular line is divided
into 360 equal parts called degrees. Each degree is divided into 60 smaller
parts, called minutes. A nautical mile is the length of one minute. The
nautical mile is a standardized unit of measurement used by all nations for air
and sea travel. It equals 1.1508 miles
(1.852 kilometers).

If you are
traveling at one nautical mile per hour, you are travelling at the speed of one
knot. Why is it called a knot? To tell speed, a ship would carry a line wound
on a reel. A chip of wood on the end of
the line allowed to drag in the water behind the ship, causing the line to
unreel. The line was knotted at
intervals of 47 feet 3 inches and the line allowed to drag for exactly 28
seconds. (47 feet 3 inches are to 1.1508
miles what 28 seconds are to one hour) If the line unwound too the fifth knot
in 28 seconds, the ship was moving at 5 knots per hour.