Q: Why is a ship’s speed measured in knots instead of miles per
hour?
Q: Why is a ship’s speed measured in knots instead of miles per hour?
A: A knot is one nautical mile per hour and equals 6,076 feet (1/60 of a degree at the equator). So if you’re moving at one nautical mile per hour, you’re going 47.25 feet every 28 seconds.
A long time ago, sailors used this length to measure their ship’s speed. Ships carried a rope, called a log line, with a weight attached to one end and knots tied in it every 47.25 feet. Sailors would put the weighted end in the water, and as the ship clipped along, a reel of the knotted rope would unfurl.
If one knot was pulled off every 28 seconds, the ship was traveling at 1 knot. If five knots were being pulled off every 28 seconds, it was traveling at 5 knots, and so forth.
Source: Douglas B. Smith
