> In sailing, what does a knot measure?And the answer: speed.On the ocean, a knot measures speed, with one knot measuring one nautical mileper hour. Nautical miles are based on longitude and latitude coordinates, withone nautical mile equaling one minute of latitude.Photo credit: public domain.Measuring speed and distance was a whole lot harderbefore Google Maps. And that's not to mention measuring speed and distance onthe ocean – though it may seem strange, using knots is an effective andaccurate way to estimate the speed of a ship on the sea. Interestingly, the term"knot" dates back to the 17th century, when sailors measured the speed of theirship using a device called a "common log." The common log was a rope with (youguessed it) knots at regular intervals attached to a piece of wood. Marinerswould lower the wood piece into the water and allow it to float freely behindthe ship for an amount of time that was measured with an hourglass, and when thetime was up, they would count the knots between the ship and the piece of wood.Voila! That number of knots estimated the speed of the ship.Nautical miles, on the other hand, offer a means of measuring distance on theocean. This system works with the curvature of the Earth on long distancejourneys, which proves effective to use in air and space travel as well.Although nautical miles weren't standardized until the mid-20th century, theiruse by sailors was consistent beginning in the late 16th century. Navigation atsea was actually done by eye until around 1500, when navigational instrumentswere developed and cartographers began using a coordinate system with parallelsof latitude and meridians of longitude.Learn more about knots and nautical travel here[https://www.history.com/news/why-is-a-ships-speed-measured-in-knots].