Question:
"How is speed measured at Sea?"
Louis from Bath, Maine--USA

Answer:
The captains in our group knew what the answer was to this one, but the rest of us couldn't wait to learn the answer. Great question!
We went to "The Handy Ocean Answer Book" and learned... "...Nautical speed for ships (it is also used for airplanes) is measured in knots. One knot is equal to one nautical mile per hour. For example, a ship travelling at a 30 knot speed travels 30 nautical miles an hour. Navigators use the nautical mile because of its simple relationship to the degrees and minutes when measuring latitude and longitude. The international nautical mile equals one-sixtieth of one degree, or a minute of arc, of the Earth's circumference. Thus, the international nautical mile equals 1.151 statute miles (1.852 kilometers)."

So where did they come up with the term 'knot?' Glad you asked...
"The word "knot" originated long ago when sailing ships carried a speed-measuring device called a 'log chip and line:' A log attached to a rope was heaved overboard attached to a line that contained knots spaced at intervals of 47 feet, 3 inches (14.4 meters). As the login the water pulled on the rope and the rope was continually let out, the speed was calculated as the number of knots were counted in a standardized time interval of 28 seconds. Thus, if the log pulled out 5 knots in 28 seconds, the sailing ship was moving at 5 knots or 5 nautical miles per hour."

Thanks to the "The Handy Ocean Answer Book" by Thomas E. Svarney & Patricia Barnes-Svarney Visible Ink Press, 2000 

Find more great stories in the OCEAN ARCHIVES >