# Why ships and airplanes measure speed in nautical miles (knots) rather than miles and kilometers?

When you travel using a bike or a car, your speed is measured in miles or kilometers per hour. That unit of measurement, however, changes when you get on a ship or an airplane. These two vessels use the term ‘knot’ or nautical miles instead to determine how fast they are traveling. But have you ever wondered why they use knots instead of KPH or MPH? Well, the story traced back a very long time ago.

If your thinking that unit of measurement, knots, has something to do with rope – you are right. At the onset of the 17th century, sailors started using a simple device, the standard log, to measure their ships’ speed. A piece of rope is tied on a wood shaped like a pie slice called ‘chip.’ Then, depending on the nautical mile’s length, knots are placed at uniform intervals along the entirety of the rope, at 14.4 meters to be precise.

To measure the speed, one end of the rope remains at the ship, while the other end with the chip is thrown into the water. Mariners would then utilize a sand hourglass as the rope roll out freely. They would tabulate the time the line unreeled, and add up the number of knots that had gone through their fingers. After a specified duration, the counted number of knots would determine the ship’s speed at that time. For instance, if the sailor counted 8 knots, the vessel is traveling at 8 nautical miles per hour.

While it is useful, it’s not quite convenient as it deters sailors from having an indicator that would inform them about the ship’s speed from time to time. Mariners had to do the process many times throughout the days to arrive in an average of how fast they ship is going. Nevertheless, it enables them to determine where they are and how much longer it would take for them to reach their destination.

For a long time, though, there was disarray among different countries regarding the exact measurement of one nautical mile. The argument was only settled in 1929 when the nautical mile’s measurement was internationally standardized at 6,076 feet. United Staes only adapted in 25 years later in 1954.

A nautical mile is far different from the mile we have on land, which is regarded as statute mile. The former is derived from Earth circumference, while the latter is based on walking distance. A nautical mile is equal to a minute of latitude and is slightly longer than the standard mile we know. A nautical mile is equal to 1.1508 statute miles.

Today, the device used to measure speed is still called a log. However, the way it works is very much different. Also, knots are still used as a unit of measurement sans the rope and the wood. We utilize modern technologies, such as satellites, GPS, and Doppler radar, all much easier and quicker to do, and far more accurate to an extreme degree. Airplanes also use knots to measure speed and nautical miles for determining distance, as they also use Earth’s circumference.

Thanks to the inventiveness of ancient mariners, a simple device used a very a long time ago, has become the foundation of the unit of measurement we have today.