Sailing Through Time: Why ships use knots as a unit of speed

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If you’ve ever embarked on a cruise or simply have a fascination with nautical pursuits, you’ve likely come across ships’ speeds being measured in “knots.” This particular unit of measurement has deep historical roots, intertwined with the development of maritime navigation. In this article, I will take you on a journey through the centuries to discover the allure behind the term “knot” and why this unit of measurement continues to be a mainstay in the world of navigation.

A Tale of Rope and Knots:

The history of knots as a unit of measurement dates back to at least the 16th century. Early sailors used a simple but ingenious method to calculate the speed of their ship. They tied a rope around a reel, with knots tied at regular intervals. The rope was then attached to a piece of wood that was thrown overboard. As the ship moved forward, the rope would unravel, and sailors would count how many knots passed in a given amount of time, usually measured with an hourglass. Thus, the number of knots that passed in that period became a primitive measure of the ship’s speed.

Standardization and Modern Definition:

As time passed and navigation techniques advanced, the knot system became more sophisticated and standardized. Today, one knot is equal to one nautical mile per hour, which is equal to 1.852 kilometers per hour or 1.1508 miles per hour. This standardization was important to ensure that ships around the world use a common measure, facilitating international navigation and communication.

The Nautical Mile:

But why use nautical miles instead of land miles or kilometers? The answer lies in the geometry of the Earth. A nautical mile is based on the circumference of the Earth and is defined as one minute of arc along a meridian of the Earth. This is particularly useful in navigation, where geographic coordinates, measured in degrees, minutes, and seconds, are fundamental for pinpointing locations and plotting courses.

Relevance Today:

Despite advances in technology and the availability of more precise measures, knots remain the standard unit for the speed of ships. This is partly due to tradition, but also because knots are intrinsically linked to geographic coordinates, making navigation more intuitive for sailors.


Measuring the speed of ships in knots is a legacy of an era when navigation was as much an art as it was a science. This unit of measurement has grown and evolved alongside navigation techniques and continues to play a fundamental role in modern navigation. Knots are not just a tribute to the rich history of maritime navigation, but are also an example of how traditions can harmoniously integrate with modern science and technology. So, every time you hear about knots, think of the daring explorations of centuries past and the journey that navigation has taken through time.


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Sailing Through Time: Why ships use knots as a unit of speed


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