Speed on the land is measured in the unit of time spent for passing of one kilometer – kilometers per hour. On water the speed is measured in knots – the special units characteristic only of navigation.
According to encyclopedic dictionaries the knot represents the linear measure equal to 1 nautical mile or 1852 meters. Thus, the vessel going with a speed of one mile per hour or 1 knot an hour passes the distance equal to one kilometer and 852 meters for an hour. What such, at first sight, strange features of conducting measurements in navigation and navigation are connected with?
Knot birth
The fact is that this linear measure was born in times when accuracy was completely subordinated to the make-shifts and the simplest methods capable to give though some information which is brought closer to the truth. Methods of calculation of speeds were simple and primitive. Sailors had to use an ordinary tench or the thin rope tied to a stern on which through certain distances special marks in the form of simple knots became.
Tench with a special log on the end (a usual large-size log which was used for determination of such geographical parameter as longitude) was thrown out overboard and followed at the rate of the ship. Gathering speed, the vessel promoted tension of a cable on which other end the notorious log was located, and through a fist of the sailor standing on the deck various number of knots of a rope could pass in time which he marked by means of ordinary hourglasses.
There are several hypotheses connected with the distance applied to formation of knots according to one of versions it equaled to 25 feet or 7.63 meters, and on another - 47 feet and 3 inches, that is about 14.5 meters.
The systematized tradition
Today the tradition to measure speeds of the ships in knots remained, however it was systematized and brought to a certain order. It is interesting that for measurement of speed of the ship logs which changed to unrecognizability are still used and instead of a usual log with a rope represent high-precision sea mechanisms, or the peculiar revolving objects shipped in water and having special metal blades which at the movement of the vessel put modern devices of measurement of vessel speed in action.
The knot is equated to one nautical mile which, by the way, a little more than overland: 1852 m against 1609 m.
However the sharpness and resourcefulness of the first sailors of a long voyage who do not have special knowledge and technical means still blows the mind of modern fans of the sea.