# This Is Why Sea Speed Is Measured In ‘Knots’

A ‘knot’ is equal to 1.15 miles (1.85 km) per hour, but who cares? The real question here is why on earth do we measure a ship’s speed in knots. As it turns out though, there’s a pretty good explanation behind this indeed weird ‘measuring unit’.

Here’s how it started.

Back in the 17th century, in order to know the speed of their ship, sailors were using a chip-log device called “common log”. This device was essentially a rope that had knots at evenly spaced intervals and it was attached to a plank of wood that was shaped like a wedge in order to float behind the ship perpendicular. The device was lowered into the sea and was let freely for 1/120th of a mile with a 30-second sand-glass timer. When the time passed, the rope was pulled and sailors counted the number of knots between the ship and the wood with the number of knots counted being the speed of the ship. Here’s a picture of the device: (the article continues after the ad)

By the way, to clarify things out, a knot is not the same as a nautical mile. The difference is that knot measures speed while a nautical mile measures distance.

### If you like what you read, then you will definitely love this one: Why Is A Quarter Called ‘Two Bits’?

Photo: WikimediaArno_M / Pixabay
Photoshop: I’m A Useless Info Junkie
Sources: What is the difference between a nautical mile and a knot? | The Wise Book of Whys