The original 14.4 meter distance between knots in the rope, divided by a 30-second timer, was equivalent to a speed of 1.85 kilometers per hour. Ergo, 1 knot equals 1 nautical mile per hour.

For example, a ship that is sailing at 10 knots, will do 10 nautical miles in an hour. Seventeenth-century mariners starting measuring the speed of their ships by using a common log.

So, today, if you’re using a 28-second timer, to get your accurate speed in knots, you need to have the interval of knots at 14.4018 meters (47 feet, 3 inches).

A ship's speed is given in knots, a measure dating back to the 16th century. iStock The concept of knots originated in the late 16th century, when European navigators were making long ocean voyages.

The average speed of most modern cruise ships is just 20 knots or approximately 23 miles per hour. This may not seem much, but this is enough for a ship to travel 480 nautical miles or 550 miles ...

The original 14.4 meter distance between knots in the rope, divided by a 30-second timer, was equivalent to a speed of 1.85 kilometers per hour. Ergo, 1 knot equals 1 nautical mile per hour.