Why does boats measure speed in knots and not mph/kmh?
In: Physics
The term “knots”, as mentioned refers to a old low-tech way of measuring speed by counting knots tied in a rope. The term translates to “nautical miles per hour” (so a knot isn’t some other unit of measure).
Nautical Miles are different from Land Miles because land miles can be easily measured directly (with a string or a wheel or anything really). Nautical miles aren’t measured but *calculated*, a sailor would take measurements of stars at night and use those measurements and some math equations to determine where on the surface of the Earth they are. A nautical mile is defined as 1 Minute Division (1/60) of a Degree of Latitude (the horizontal lines on the globe, like a ladder).
ELI15 – Land miles are easily measured in an X-Y-Z (cubic) 3D axis, this means that any point in space is defined by 3 points, one on each axis. Traveling the sea is more like walking across the surface of a ball, so rather than an X-Y-Z system, we use a spherical axis system where each point is defined by degrees around the origin, like arms on a clock, and a single distance (radius) from the origin to the point.
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